WorldWideScience

Sample records for subgrid scale mixing

  1. Lagrangian scheme to model subgrid-scale mixing and spreading in heterogeneous porous media

    Science.gov (United States)

    Herrera, P. A.; Cortínez, J. M.; Valocchi, A. J.

    2017-04-01

    Small-scale heterogeneity of permeability controls spreading, dilution, and mixing of solute plumes at large scale. However, conventional numerical simulations of solute transport are unable to resolve scales of heterogeneity below the grid scale. We propose a Lagrangian numerical approach to implement closure models to account for subgrid-scale spreading and mixing in Darcy-scale numerical simulations of solute transport in mildly heterogeneous porous media. The novelty of the proposed approach is that it considers two different dispersion coefficients to account for advective spreading mechanisms and local-scale dispersion. Using results of benchmark numerical simulations, we demonstrate that the proposed approach is able to model subgrid-scale spreading and mixing provided there is a correct choice of block-scale dispersion coefficient. We also demonstrate that for short travel times it is only possible to account for spreading or mixing using a single block-scale dispersion coefficient. Moreover, we show that it is necessary to use time-dependent dispersion coefficients to obtain correct mixing rates. On the contrary, for travel times that are large in comparison to the typical dispersive time scale, it is possible to use a single expression to compute the block-dispersion coefficient, which is equal to the asymptotic limit of the block-scale macrodispersion coefficient proposed by Rubin et al. (1999). Our approach provides a flexible and efficient way to model subgrid-scale mixing in numerical models of large-scale solute transport in heterogeneous aquifers. We expect that these findings will help to better understand the applicability of the advection-dispersion-equation (ADE) to simulate solute transport at the Darcy scale in heterogeneous porous media.

  2. A Physically Based Horizontal Subgrid-scale Turbulent Mixing Parameterization for the Convective Boundary Layer in Mesoscale Models

    Science.gov (United States)

    Zhou, Bowen; Xue, Ming; Zhu, Kefeng

    2017-04-01

    Compared to the representation of vertical turbulent mixing through various PBL schemes, the treatment of horizontal turbulence mixing in the boundary layer within mesoscale models, with O(10) km horizontal grid spacing, has received much less attention. In mesoscale models, subgrid-scale horizontal fluxes most often adopt the gradient-diffusion assumption. The horizontal mixing coefficients are usually set to a constant, or through the 2D Smagorinsky formulation, or in some cases based on the 1.5-order turbulence kinetic energy (TKE) closure. In this work, horizontal turbulent mixing parameterizations using physically based characteristic velocity and length scales are proposed for the convective boundary layer based on analysis of a well-resolved, wide-domain large-eddy simulation (LES). The proposed schemes involve different levels of sophistication. The first two schemes can be used together with first-order PBL schemes, while the third uses TKE to define its characteristic velocity scale and can be used together with TKE-based higher-order PBL schemes. The current horizontal mixing formulations are also assessed a priori through the filtered LES results to illustrate their limitations. The proposed parameterizations are tested a posteriori in idealized simulations of turbulent dispersion of a passive scalar. Comparisons show improved horizontal dispersion by the proposed schemes, and further demonstrate the weakness of the current schemes.

  3. A new mixed subgrid-scale model for large eddy simulation of turbulent drag-reducing flows of viscoelastic fluids

    Science.gov (United States)

    Li, Feng-Chen; Wang, Lu; Cai, Wei-Hua

    2015-07-01

    A mixed subgrid-scale (SGS) model based on coherent structures and temporal approximate deconvolution (MCT) is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is to perform spatial filtering for the momentum equation and temporal filtering for the conformation tensor transport equation of turbulent flow of viscoelastic fluid, respectively. The MCT model is suitable for large eddy simulation (LES) of turbulent drag-reducing flows of viscoelastic fluids in engineering applications since the model parameters can be easily obtained. The LES of forced homogeneous isotropic turbulence (FHIT) with polymer additives and turbulent channel flow with surfactant additives based on MCT SGS model shows excellent agreements with direct numerical simulation (DNS) results. Compared with the LES results using the temporal approximate deconvolution model (TADM) for FHIT with polymer additives, this mixed SGS model MCT behaves better, regarding the enhancement of calculating parameters such as the Reynolds number. For scientific and engineering research, turbulent flows at high Reynolds numbers are expected, so the MCT model can be a more suitable model for the LES of turbulent drag-reducing flows of viscoelastic fluid with polymer or surfactant additives. Project supported by the China Postdoctoral Science Foundation (Grant No. 2011M500652), the National Natural Science Foundation of China (Grant Nos. 51276046 and 51206033), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20112302110020).

  4. Final Report. Evaluating the Climate Sensitivity of Dissipative Subgrid-Scale Mixing Processes and Variable Resolution in NCAR's Community Earth System Model

    Energy Technology Data Exchange (ETDEWEB)

    Jablonowski, Christiane [Univ. of Michigan, Ann Arbor, MI (United States)

    2015-12-14

    The goals of this project were to (1) assess and quantify the sensitivity and scale-dependency of unresolved subgrid-scale mixing processes in NCAR’s Community Earth System Model (CESM), and (2) to improve the accuracy and skill of forthcoming CESM configurations on modern cubed-sphere and variable-resolution computational grids. The research thereby contributed to the description and quantification of uncertainties in CESM’s dynamical cores and their physics-dynamics interactions.

  5. Sub-Grid Scale Plume Modeling

    Directory of Open Access Journals (Sweden)

    Greg Yarwood

    2011-08-01

    Full Text Available Multi-pollutant chemical transport models (CTMs are being routinely used to predict the impacts of emission controls on the concentrations and deposition of primary and secondary pollutants. While these models have a fairly comprehensive treatment of the governing atmospheric processes, they are unable to correctly represent processes that occur at very fine scales, such as the near-source transport and chemistry of emissions from elevated point sources, because of their relatively coarse horizontal resolution. Several different approaches have been used to address this limitation, such as using fine grids, adaptive grids, hybrid modeling, or an embedded sub-grid scale plume model, i.e., plume-in-grid (PinG modeling. In this paper, we first discuss the relative merits of these various approaches used to resolve sub-grid scale effects in grid models, and then focus on PinG modeling which has been very effective in addressing the problems listed above. We start with a history and review of PinG modeling from its initial applications for ozone modeling in the Urban Airshed Model (UAM in the early 1980s using a relatively simple plume model, to more sophisticated and state-of-the-science plume models, that include a full treatment of gas-phase, aerosol, and cloud chemistry, embedded in contemporary models such as CMAQ, CAMx, and WRF-Chem. We present examples of some typical results from PinG modeling for a variety of applications, discuss the implications of PinG on model predictions of source attribution, and discuss possible future developments and applications for PinG modeling.

  6. Statistical dynamical subgrid-scale parameterizations for geophysical flows

    Energy Technology Data Exchange (ETDEWEB)

    O' Kane, T J; Frederiksen, J S [Centre for Australian Weather and Climate Research, Bureau of Meteorology, 700 Collins St, Docklands, Melbourne, VIC (Australia) and CSIRO Marine and Atmospheric Research, Aspendale, VIC (Australia)], E-mail: t.okane@bom.gov.au

    2008-12-15

    Simulations of both atmospheric and oceanic circulations at given finite resolutions are strongly dependent on the form and strengths of the dynamical subgrid-scale parameterizations (SSPs) and in particular are sensitive to subgrid-scale transient eddies interacting with the retained scale topography and the mean flow. In this paper, we present numerical results for SSPs of the eddy-topographic force, stochastic backscatter, eddy viscosity and eddy-mean field interaction using an inhomogeneous statistical turbulence model based on a quasi-diagonal direct interaction approximation (QDIA). Although the theoretical description on which our model is based is for general barotropic flows, we specifically focus on global atmospheric flows where large-scale Rossby waves are present. We compare and contrast the closure-based results with an important earlier heuristic SSP of the eddy-topographic force, based on maximum entropy or statistical canonical equilibrium arguments, developed specifically for general ocean circulation models (Holloway 1992 J. Phys. Oceanogr. 22 1033-46). Our results demonstrate that where strong zonal flows and Rossby waves are present, such as in the atmosphere, maximum entropy arguments are insufficient to accurately parameterize the subgrid contributions due to eddy-eddy, eddy-topographic and eddy-mean field interactions. We contrast our atmospheric results with findings for the oceans. Our study identifies subgrid-scale interactions that are currently not parameterized in numerical atmospheric climate models, which may lead to systematic defects in the simulated circulations.

  7. Simple subgrid scale stresses models for homogeneous isotropic turbulence

    Science.gov (United States)

    Aupoix, B.; Cousteix, J.

    Large eddy simulations employing the filtering of Navier-Stokes equations highlight stresses, related to the interaction between large scales below the cut and small scales above it, which have been designated 'subgrid scale stresses'. Their effects include both the energy flux through the cut and a component of viscous diffusion. The eddy viscosity introduced in the subgrid scale models which give the correct energy flux through the cut by comparison with spectral closures is shown to depend only on the small scales. The Smagorinsky (1963) model can only be obtained if the cut lies in the middle of the inertial range. A novel model which takes the small scales into account statistically, and includes the effects of viscosity, is proposed and compared with classical models for the Comte-Bellot and Corrsin (1971) experiment.

  8. Importance of subgrid-scale parameterization in numerical simulations of lake circulation

    Science.gov (United States)

    Wang, Yongqi

    Two subgrid-scale modeling techniques--Smagorinsky's postulation for the horizontal eddy viscosity and the Mellor-Yamada level-2 model for the vertical eddy viscosity--are applied as turbulence closure conditions to numerical simulations of resolved-scale baroclinic lake circulations. The use of the total variation diminishing (TVD) technique in the numerical treatment of the advection terms in the governing equations depresses numerical diffusion to an acceptably low level and makes stable numerical performances possible with small eddy viscosities resulting from the turbulence closure parameterizations. The results show that, with regard to the effect of an external wind stress, the vertical turbulent mixing is mainly restricted to the topmost epilimnion with the order of magnitude for the vertical eddy viscosity of 10 -3 m 2 s -1, whilst the horizontal turbulent mixing may reach a somewhat deeper zone with an order of magnitude for the horizontal eddy viscosity of 0.1-1 m 2 s -1. Their spatial and temporal variations and influences on numerical results are significant. A comparison with prescribed constant eddy viscosities clearly shows the importance of subgrid-scale closures on resolved-scale flows in the lake circulation simulation. A predetermination of the eddy viscosities is inappropriate and should be abandoned. Their values must be determined by suitable subgrid-scale closure techniques.

  9. The subgrid-scale scalar variance under supercritical pressure conditions

    Science.gov (United States)

    Masi, Enrica; Bellan, Josette

    2011-08-01

    To model the subgrid-scale (SGS) scalar variance under supercritical-pressure conditions, an equation is first derived for it. This equation is considerably more complex than its equivalent for atmospheric-pressure conditions. Using a previously created direct numerical simulation (DNS) database of transitional states obtained for binary-species systems in the context of temporal mixing layers, the activity of terms in this equation is evaluated, and it is found that some of these new terms have magnitude comparable to that of governing terms in the classical equation. Most prominent among these new terms are those expressing the variation of diffusivity with thermodynamic variables and Soret terms having dissipative effects. Since models are not available for these new terms that would enable solving the SGS scalar variance equation, the adopted strategy is to directly model the SGS scalar variance. Two models are investigated for this quantity, both developed in the context of compressible flows. The first one is based on an approximate deconvolution approach and the second one is a gradient-like model which relies on a dynamic procedure using the Leonard term expansion. Both models are successful in reproducing the SGS scalar variance extracted from the filtered DNS database, and moreover, when used in the framework of a probability density function (PDF) approach in conjunction with the β-PDF, they excellently reproduce a filtered quantity which is a function of the scalar. For the dynamic model, the proportionality coefficient spans a small range of values through the layer cross-stream coordinate, boding well for the stability of large eddy simulations using this model.

  10. Subgrid-scale turbulence in shock-boundary layer flows

    Science.gov (United States)

    Jammalamadaka, Avinash; Jaberi, Farhad

    2015-04-01

    Data generated by direct numerical simulation (DNS) for a Mach 2.75 zero-pressure gradient turbulent boundary layer interacting with shocks of different intensities are used for a priori analysis of subgrid-scale (SGS) turbulence and various terms in the compressible filtered Navier-Stokes equations. The numerical method used for DNS is based on a hybrid scheme that uses a non-dissipative central scheme in the shock-free turbulent regions and a robust monotonicity-preserving scheme in the shock regions. The behavior of SGS stresses and their components, namely Leonard, Cross and Reynolds components, is examined in various regions of the flow for different shock intensities and filter widths. The backscatter in various regions of the flow is found to be significant only instantaneously, while the ensemble-averaged statistics indicate no significant backscatter. The budgets for the SGS kinetic energy equation are examined for a better understanding of shock-tubulence interactions at the subgrid level and also with the aim of providing useful information for one-equation LES models. A term-by-term analysis of SGS terms in the filtered total energy equation indicate that while each term in this equation is significant by itself, the net contribution by all of them is relatively small. This observation is consistent with our a posteriori analysis.

  11. A priori study of subgrid-scale flux of a passive scalar in isotropic homogeneous turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Chumakov, Sergei [Los Alamos National Laboratory

    2008-01-01

    We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direction of the flux is strongly coupled with the subgrid-scale stress axes rather than the resolved flow quantities such as strain, vorticity, or scalar gradient. We derive an approximate transport equation for the subgrid-scale flux of a scalar and look at the relative importance of the terms in the transport equation. A particular form of LES tensor-viscosity model for the scalar flux is investigated, which includes the subgrid-scale stress. Effect of different models for the subgrid-scale stress on the model for the subgrid-scale flux is studied.

  12. Modeling Subgrid Scale Droplet Deposition in Multiphase-CFD

    Science.gov (United States)

    Agostinelli, Giulia; Baglietto, Emilio

    2017-11-01

    The development of first-principle-based constitutive equations for the Eulerian-Eulerian CFD modeling of annular flow is a major priority to extend the applicability of multiphase CFD (M-CFD) across all two-phase flow regimes. Two key mechanisms need to be incorporated in the M-CFD framework, the entrainment of droplets from the liquid film, and their deposition. Here we focus first on the aspect of deposition leveraging a separate effects approach. Current two-field methods in M-CFD do not include appropriate local closures to describe the deposition of droplets in annular flow conditions. As many integral correlations for deposition have been proposed for lumped parameters methods applications, few attempts exist in literature to extend their applicability to CFD simulations. The integral nature of the approach limits its applicability to fully developed flow conditions, without geometrical or flow variations, therefore negating the scope of CFD application. A new approach is proposed here that leverages local quantities to predict the subgrid-scale deposition rate. The methodology is first tested into a three-field approach CFD model.

  13. Exploring nonlinear subgrid-scale models and new characteristic length scales for large-eddy simulation

    NARCIS (Netherlands)

    Silvis, Maurits H.; Trias, F. Xavier; Abkar, M.; Bae, H.J.; Lozano-Duran, A.; Verstappen, R.W.C.P.; Moin, Parviz; Urzay, Javier

    2016-01-01

    We study subgrid-scale modeling for large-eddy simulation of anisotropic turbulent flows on anisotropic grids. In particular, we show how the addition of a velocity-gradient-based nonlinear model term to an eddy viscosity model provides a better representation of energy transfer. This is shown to

  14. Physical consistency of subgrid-scale models for large-eddy simulation of incompressible turbulent flows

    CERN Document Server

    Silvis, Maurits H; Verstappen, Roel

    2016-01-01

    We study the construction of subgrid-scale models for large-eddy simulation of incompressible turbulent flows. In particular, we aim to consolidate a systematic approach of constructing subgrid-scale models, based on the idea that it is desirable that subgrid-scale models are consistent with the properties of the Navier-Stokes equations and the turbulent stresses. To that end, we first discuss in detail the symmetries of the Navier-Stokes equations, and the near-wall scaling behavior, realizability and dissipation properties of the turbulent stresses. We furthermore summarize the requirements that subgrid-scale models have to satisfy in order to preserve these important mathematical and physical properties. In this fashion, a framework of model constraints arises that we apply to analyze the behavior of a number of existing subgrid-scale models that are based on the local velocity gradient. We show that these subgrid-scale models do not satisfy all the desired properties, after which we explain that this is p...

  15. Evapotranspiration and cloud variability at regional sub-grid scales

    Science.gov (United States)

    Vila-Guerau de Arellano, Jordi; Sikma, Martin; Pedruzo-Bagazgoitia, Xabier; van Heerwaarden, Chiel; Hartogensis, Oscar; Ouwersloot, Huug

    2017-04-01

    In regional and global models uncertainties arise due to our incomplete understanding of the coupling between biochemical and physical processes. Representing their impact depends on our ability to calculate these processes using physically sound parameterizations, since they are unresolved at scales smaller than the grid size. More specifically over land, the coupling between evapotranspiration, turbulent transport of heat and moisture, and clouds lacks a combined representation to take these sub-grid scales interactions into account. Our approach is based on understanding how radiation, surface exchange, turbulent transport and moist convection are interacting from the leaf- to the cloud scale. We therefore place special emphasis on plant stomatal aperture as the main regulator of CO2-assimilation and water transpiration, a key source of moisture source to the atmosphere. Plant functionality is critically modulated by interactions with atmospheric conditions occurring at very short spatiotemporal scales such as cloud radiation perturbations or water vapour turbulent fluctuations. By explicitly resolving these processes, the LES (large-eddy simulation) technique is enabling us to characterize and better understand the interactions between canopies and the local atmosphere. This includes the adaption time of vegetation to rapid changes in atmospheric conditions driven by turbulence or the presence of cumulus clouds. Our LES experiments are based on explicitly coupling the diurnal atmospheric dynamics to a plant physiology model. Our general hypothesis is that different partitioning of direct and diffuse radiation leads to different responses of the vegetation. As a result there are changes in the water use efficiencies and shifts in the partitioning of sensible and latent heat fluxes under the presence of clouds. Our presentation is as follows. First, we discuss the ability of LES to reproduce the surface energy balance including photosynthesis and CO2 soil

  16. Multifractal subgrid-scale modeling within a variational multiscale method for large-eddy simulation of turbulent flow

    Science.gov (United States)

    Rasthofer, U.; Gravemeier, V.

    2013-02-01

    Multifractal subgrid-scale modeling within a variational multiscale method is proposed for large-eddy simulation of turbulent flow. In the multifractal subgrid-scale modeling approach, the subgrid-scale velocity is evaluated from a multifractal description of the subgrid-scale vorticity, which is based on the multifractal scale similarity of gradient fields in turbulent flow. The multifractal subgrid-scale modeling approach is integrated into a variational multiscale formulation, which constitutes a new application of the variational multiscale concept. A focus of this study is on the application of the multifractal subgrid-scale modeling approach to wall-bounded turbulent flow. Therefore, a near-wall limit of the multifractal subgrid-scale modeling approach is derived in this work. The novel computational approach of multifractal subgrid-scale modeling within a variational multiscale formulation is applied to turbulent channel flow at various Reynolds numbers, turbulent flow over a backward-facing step and turbulent flow past a square-section cylinder, which are three of the most important and widely-used benchmark examples for wall-bounded turbulent flow. All results presented in this study confirm a very good performance of the proposed method. Compared to a dynamic Smagorinsky model and a residual-based variational multiscale method, improved results are obtained. Moreover, it is demonstrated that the subgrid-scale energy transfer incorporated by the proposed method very well approximates the expected energy transfer as obtained from appropriately filtered direct numerical simulation data. The computational cost is notably reduced compared to a dynamic Smagorinsky model and only marginally increased compared to a residual-based variational multiscale method.

  17. Subgrid-scale models for large-eddy simulation of rotating turbulent channel flows

    Science.gov (United States)

    Silvis, Maurits H.; Bae, Hyunji Jane; Trias, F. Xavier; Abkar, Mahdi; Moin, Parviz; Verstappen, Roel

    2017-11-01

    We aim to design subgrid-scale models for large-eddy simulation of rotating turbulent flows. Rotating turbulent flows form a challenging test case for large-eddy simulation due to the presence of the Coriolis force. The Coriolis force conserves the total kinetic energy while transporting it from small to large scales of motion, leading to the formation of large-scale anisotropic flow structures. The Coriolis force may also cause partial flow laminarization and the occurrence of turbulent bursts. Many subgrid-scale models for large-eddy simulation are, however, primarily designed to parametrize the dissipative nature of turbulent flows, ignoring the specific characteristics of transport processes. We, therefore, propose a new subgrid-scale model that, in addition to the usual dissipative eddy viscosity term, contains a nondissipative nonlinear model term designed to capture transport processes, such as those due to rotation. We show that the addition of this nonlinear model term leads to improved predictions of the energy spectra of rotating homogeneous isotropic turbulence as well as of the Reynolds stress anisotropy in spanwise-rotating plane-channel flows. This work is financed by the Netherlands Organisation for Scientific Research (NWO) under Project Number 613.001.212.

  18. Stochastic fields method for sub-grid scale emission heterogeneity in mesoscale atmospheric dispersion models

    OpenAIRE

    M. Cassiani; Vinuesa, J.F.; Galmarini, S.; Denby, B

    2010-01-01

    The stochastic fields method for turbulent reacting flows has been applied to the issue of sub-grid scale emission heterogeneity in a mesoscale model. This method is a solution technique for the probability density function (PDF) transport equation and can be seen as a straightforward extension of currently used mesoscale dispersion models. It has been implemented in an existing mesoscale model and the results are compared with Large-Eddy Simulation (LES) data devised to test specifically the...

  19. Subgrid-scale stresses and scalar fluxes constructed by the multi-scale turnover Lagrangian map

    Science.gov (United States)

    AL-Bairmani, Sukaina; Li, Yi; Rosales, Carlos; Xie, Zheng-tong

    2017-04-01

    The multi-scale turnover Lagrangian map (MTLM) [C. Rosales and C. Meneveau, "Anomalous scaling and intermittency in three-dimensional synthetic turbulence," Phys. Rev. E 78, 016313 (2008)] uses nested multi-scale Lagrangian advection of fluid particles to distort a Gaussian velocity field and, as a result, generate non-Gaussian synthetic velocity fields. Passive scalar fields can be generated with the procedure when the fluid particles carry a scalar property [C. Rosales, "Synthetic three-dimensional turbulent passive scalar fields via the minimal Lagrangian map," Phys. Fluids 23, 075106 (2011)]. The synthetic fields have been shown to possess highly realistic statistics characterizing small scale intermittency, geometrical structures, and vortex dynamics. In this paper, we present a study of the synthetic fields using the filtering approach. This approach, which has not been pursued so far, provides insights on the potential applications of the synthetic fields in large eddy simulations and subgrid-scale (SGS) modelling. The MTLM method is first generalized to model scalar fields produced by an imposed linear mean profile. We then calculate the subgrid-scale stress, SGS scalar flux, SGS scalar variance, as well as related quantities from the synthetic fields. Comparison with direct numerical simulations (DNSs) shows that the synthetic fields reproduce the probability distributions of the SGS energy and scalar dissipation rather well. Related geometrical statistics also display close agreement with DNS results. The synthetic fields slightly under-estimate the mean SGS energy dissipation and slightly over-predict the mean SGS scalar variance dissipation. In general, the synthetic fields tend to slightly under-estimate the probability of large fluctuations for most quantities we have examined. Small scale anisotropy in the scalar field originated from the imposed mean gradient is captured. The sensitivity of the synthetic fields on the input spectra is assessed by

  20. Stochastic fields method for sub-grid scale emission heterogeneity in mesoscale atmospheric dispersion models

    Directory of Open Access Journals (Sweden)

    M. Cassiani

    2010-01-01

    Full Text Available The stochastic fields method for turbulent reacting flows has been applied to the issue of sub-grid scale emission heterogeneity in a mesoscale model. This method is a solution technique for the probability density function (PDF transport equation and can be seen as a straightforward extension of currently used mesoscale dispersion models. It has been implemented in an existing mesoscale model and the results are compared with Large-Eddy Simulation (LES data devised to test specifically the effect of sub-grid scale emission heterogeneity on boundary layer concentration fluctuations. The sub-grid scale emission variability is assimilated in the model as a PDF of the emissions. The stochastic fields method shows excellent agreement with the LES data without adjustment of the constants used in the mesoscale model. The stochastic fields method is a stochastic solution of the transport equations for the concentration PDF of dispersing scalars, therefore it possesses the ability to handle chemistry of any complexity without the need to introduce additional closures for the high order statistics of chemical species. This study shows for the first time the feasibility of applying this method to mesoscale chemical transport models.

  1. A scale-aware subgrid model for quasi-geostrophic turbulence

    Science.gov (United States)

    Bachman, Scott D.; Fox-Kemper, Baylor; Pearson, Brodie

    2017-02-01

    This paper introduces two methods for dynamically prescribing eddy-induced diffusivity, advection, and viscosity appropriate for primitive equation models with resolutions permitting the forward potential enstrophy cascade of quasi-geostrophic dynamics, such as operational ocean models and high-resolution climate models with O>(25>) km horizontal resolution and finer. Where quasi-geostrophic dynamics fail (e.g., the equator, boundary layers, and deep convection), the method reverts to scalings based on a matched two-dimensional enstrophy cascade. A principle advantage is that these subgrid models are scale-aware, meaning that the model is suitable over a range of grid resolutions: from mesoscale grids that just permit baroclinic instabilities to grids below the submesoscale where ageostrophic effects dominate. Two approaches are presented here using Large Eddy Simulation (LES) techniques adapted for three-dimensional rotating, stratified turbulence. The simpler approach has one nondimensional parameter, Λ, which has an optimal value near 1. The second approach dynamically optimizes Λ during simulation using a test filter. The new methods are tested in an idealized scenario by varying the grid resolution, and their use improves the spectra of potential enstrophy and energy in comparison to extant schemes. The new methods keep the gridscale Reynolds and Péclet numbers near 1 throughout the domain, which confers robust numerical stability and minimal spurious diapycnal mixing. Although there are no explicit parameters in the dynamic approach, there is strong sensitivity to the choice of test filter. Designing test filters for heterogeneous ocean turbulence adds cost and uncertainty, and we find the dynamic method does not noticeably improve over setting Λ = 1.

  2. Evaluation of Subgrid-Scale Transport of Hydrometeors in a PDF-based Scheme using High-Resolution CRM Simulations

    Science.gov (United States)

    Wong, M.; Ovchinnikov, M.; Wang, M.; Larson, V. E.

    2014-12-01

    In current climate models, the model resolution is too coarse to explicitly resolve deep convective systems. Parameterization schemes are therefore needed to represent the physical processes at the sub-grid scale. Recently, an approach based on assumed probability density functions (PDFs) has been developed to help unify the various parameterization schemes used in current global models. In particular, a unified parameterization scheme called the Cloud Layers Unified By Binormals (CLUBB) scheme has been developed and tested successfully for shallow boundary-layer clouds. CLUBB's implementation in the Community Atmosphere Model, version 5 (CAM5) is also being extended to treat deep convection cases, but parameterizing subgrid-scale vertical transport of hydrometeors remains a challenge. To investigate the roots of the problem and possible solutions, we generate a high-resolution benchmark simulation of a deep convection case using a cloud-resolving model (CRM) called System for Atmospheric Modeling (SAM). We use the high-resolution 3D CRM results to assess the prognostic and diagnostic higher-order moments in CLUBB that are in relation to the subgrid-scale transport of hydrometeors. We also analyze the heat and moisture budgets in terms of CLUBB variables from the SAM benchmark simulation. The results from this study will be used to devise a better representation of vertical subgrid-scale transport of hydrometeors by utilizing the sub-grid variability information from CLUBB.

  3. Effects of Implementing Subgrid-Scale Cloud-Radiation Interactions in a Regional Climate Model

    Science.gov (United States)

    Herwehe, J. A.; Alapaty, K.; Otte, T.; Nolte, C. G.

    2012-12-01

    Interactions between atmospheric radiation, clouds, and aerosols are the most important processes that determine the climate and its variability. In regional scale models, when used at relatively coarse spatial resolutions (e.g., larger than 1 km), convective cumulus clouds need to be parameterized as subgrid-scale clouds. Like many groups, our regional climate modeling group at the EPA uses the Weather Research & Forecasting model (WRF) as a regional climate model (RCM). One of the findings from our RCM studies is that the summertime convective systems simulated by the WRF model are highly energetic, leading to excessive surface precipitation. We also found that the WRF model does not consider the interactions between convective clouds and radiation, thereby omitting an important process that drives the climate. Thus, the subgrid-scale cloudiness associated with convective clouds (from shallow cumuli to thunderstorms) does not exist and radiation passes through the atmosphere nearly unimpeded, potentially leading to overly energetic convection. This also has implications for air quality modeling systems that are dependent upon cloud properties from the WRF model, as the failure to account for subgrid-scale cloudiness can lead to problems such as the underrepresentation of aqueous chemistry processes within clouds and the overprediction of ozone from overactive photolysis. In an effort to advance the climate science of the cloud-aerosol-radiation (CAR) interactions in RCM systems, as a first step we have focused on linking the cumulus clouds with the radiation processes. To this end, our research group has implemented into WRF's Kain-Fritsch (KF) cumulus parameterization a cloudiness formulation that is widely used in global earth system models (e.g., CESM/CAM5). Estimated grid-scale cloudiness and associated condensate are adjusted to account for the subgrid clouds and then passed to WRF's Rapid Radiative Transfer Model - Global (RRTMG) radiation schemes to affect

  4. Improving sub-grid scale accuracy of boundary features in regional finite-difference models

    Science.gov (United States)

    Panday, Sorab; Langevin, Christian D.

    2012-01-01

    As an alternative to grid refinement, the concept of a ghost node, which was developed for nested grid applications, has been extended towards improving sub-grid scale accuracy of flow to conduits, wells, rivers or other boundary features that interact with a finite-difference groundwater flow model. The formulation is presented for correcting the regular finite-difference groundwater flow equations for confined and unconfined cases, with or without Newton Raphson linearization of the nonlinearities, to include the Ghost Node Correction (GNC) for location displacement. The correction may be applied on the right-hand side vector for a symmetric finite-difference Picard implementation, or on the left-hand side matrix for an implicit but asymmetric implementation. The finite-difference matrix connectivity structure may be maintained for an implicit implementation by only selecting contributing nodes that are a part of the finite-difference connectivity. Proof of concept example problems are provided to demonstrate the improved accuracy that may be achieved through sub-grid scale corrections using the GNC schemes.

  5. Large eddy simulation of flow over a wall-mounted cube: Comparison of different semi dynamic subgrid scale models

    Directory of Open Access Journals (Sweden)

    M Nooroullahi

    2016-09-01

    Full Text Available In this paper the ability of different semi dynamic subgrid scale models for large eddy simulation was studied in a challenging test case. The semi dynamic subgrid scale models were examined in this investigation is Selective Structure model, Coherent structure model, Wall Adaptive Large Eddy model. The test case is a simulation of flow over a wall-mounted cube in a channel. The results of these models were compared to structure function model, dynamic models and experimental data at Reynolds number 40000. Results show that these semi dynamic models could improve the ability of numerical simulation in comparison with other models which use a constant coefficient for simulation of subgrid scale viscosity. In addition, these models don't have the instability problems of dynamic models.

  6. Parameterization of subgrid plume dilution for use in large-scale atmospheric simulations

    Directory of Open Access Journals (Sweden)

    A. D. Naiman

    2010-03-01

    Full Text Available A new model of plume dynamics has been developed for use as a subgrid model of plume dilution in a large-scale atmospheric simulation. The model uses mean wind, shear, and diffusion parameters derived from the local large-scale variables to advance the plume cross-sectional shape and area in time. Comparisons with a large eddy simulation of aircraft emission plume dynamics, with an analytical solution to the dynamics of a sheared Gaussian plume, and with measurements of aircraft exhaust plume dilution at cruise altitude show good agreement with these previous studies. We argue that the model also provides a reasonable approximation of line-shaped contrail dilution and give an example of how it can be applied in a global climate model.

  7. Numerical dissipation vs. subgrid-scale modelling for large eddy simulation

    Science.gov (United States)

    Dairay, Thibault; Lamballais, Eric; Laizet, Sylvain; Vassilicos, John Christos

    2017-05-01

    This study presents an alternative way to perform large eddy simulation based on a targeted numerical dissipation introduced by the discretization of the viscous term. It is shown that this regularisation technique is equivalent to the use of spectral vanishing viscosity. The flexibility of the method ensures high-order accuracy while controlling the level and spectral features of this purely numerical viscosity. A Pao-like spectral closure based on physical arguments is used to scale this numerical viscosity a priori. It is shown that this way of approaching large eddy simulation is more efficient and accurate than the use of the very popular Smagorinsky model in standard as well as in dynamic version. The main strength of being able to correctly calibrate numerical dissipation is the possibility to regularise the solution at the mesh scale. Thanks to this property, it is shown that the solution can be seen as numerically converged. Conversely, the two versions of the Smagorinsky model are found unable to ensure regularisation while showing a strong sensitivity to numerical errors. The originality of the present approach is that it can be viewed as implicit large eddy simulation, in the sense that the numerical error is the source of artificial dissipation, but also as explicit subgrid-scale modelling, because of the equivalence with spectral viscosity prescribed on a physical basis.

  8. A nonlinear structural subgrid-scale closure for compressible MHD. I. Derivation and energy dissipation properties

    Energy Technology Data Exchange (ETDEWEB)

    Vlaykov, Dimitar G., E-mail: Dimitar.Vlaykov@ds.mpg.de [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen (Germany); Grete, Philipp [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Schmidt, Wolfram [Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany); Schleicher, Dominik R. G. [Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C (Chile)

    2016-06-15

    Compressible magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical phenomena ranging from the intergalactic to the stellar scales. In studying them, numerical simulations are nearly inescapable, due to the large degree of nonlinearity involved. However, the dynamical ranges of these phenomena are much larger than what is computationally accessible. In large eddy simulations (LESs), the resulting limited resolution effects are addressed explicitly by introducing to the equations of motion additional terms associated with the unresolved, subgrid-scale dynamics. This renders the system unclosed. We derive a set of nonlinear structural closures for the ideal MHD LES equations with particular emphasis on the effects of compressibility. The closures are based on a gradient expansion of the finite-resolution operator [W. K. Yeo (CUP, 1993)] and require no assumptions about the nature of the flow or magnetic field. Thus, the scope of their applicability ranges from the sub- to the hyper-sonic and -Alfvénic regimes. The closures support spectral energy cascades both up and down-scale, as well as direct transfer between kinetic and magnetic resolved and unresolved energy budgets. They implicitly take into account the local geometry, and in particular, the anisotropy of the flow. Their properties are a priori validated in Paper II [P. Grete et al., Phys. Plasmas 23, 062317 (2016)] against alternative closures available in the literature with respect to a wide range of simulation data of homogeneous and isotropic turbulence.

  9. A priori study of subgrid-scale features in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Dabbagh, F.; Trias, F. X.; Gorobets, A.; Oliva, A.

    2017-10-01

    At the crossroad between flow topology analysis and turbulence modeling, a priori studies are a reliable tool to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent flows. In this paper, properties of the SGS features in the framework of a large-eddy simulation are studied for a turbulent Rayleigh-Bénard convection (RBC). To do so, data from direct numerical simulation (DNS) of a turbulent air-filled RBC in a rectangular cavity of aspect ratio unity and π spanwise open-ended distance are used at two Rayleigh numbers R a ∈{1 08,1 010 } [Dabbagh et al., "On the evolution of flow topology in turbulent Rayleigh-Bénard convection," Phys. Fluids 28, 115105 (2016)]. First, DNS at Ra = 108 is used to assess the performance of eddy-viscosity models such as QR, Wall-Adapting Local Eddy-viscosity (WALE), and the recent S3PQR-models proposed by Trias et al. ["Building proper invariants for eddy-viscosity subgrid-scale models," Phys. Fluids 27, 065103 (2015)]. The outcomes imply that the eddy-viscosity modeling smoothes the coarse-grained viscous straining and retrieves fairly well the effect of the kinetic unfiltered scales in order to reproduce the coherent large scales. However, these models fail to approach the exact evolution of the SGS heat flux and are incapable to reproduce well the further dominant rotational enstrophy pertaining to the buoyant production. Afterwards, the key ingredients of eddy-viscosity, νt, and eddy-diffusivity, κt, are calculated a priori and revealed positive prevalent values to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. The topological analysis suggests that the effective turbulent diffusion paradigm and the hypothesis of a constant turbulent Prandtl number are only applicable in the large-scale strain-dominated areas in the bulk. It is shown that the bulk-dominated rotational structures of vortex-stretching (and its synchronous viscous dissipative structures) hold

  10. Convective kinetic energy equation under the mass-flux subgrid-scale parameterization

    Science.gov (United States)

    Yano, Jun-Ichi

    2015-03-01

    The present paper originally derives the convective kinetic energy equation under mass-flux subgrid-scale parameterization in a formal manner based on the segmentally-constant approximation (SCA). Though this equation is long since presented by Arakawa and Schubert (1974), a formal derivation is not known in the literature. The derivation of this formulation is of increasing interests in recent years due to the fact that it can explain basic aspects of the convective dynamics such as discharge-recharge and transition from shallow to deep convection. The derivation is presented in two manners: (i) for the case that only the vertical component of the velocity is considered and (ii) the case that both the horizontal and vertical components are considered. The equation reduces to the same form as originally presented by Arakwa and Schubert in both cases, but with the energy dissipation term defined differently. In both cases, nevertheless, the energy "dissipation" (loss) term consists of the three principal contributions: (i) entrainment-detrainment, (ii) outflow from top of convection, and (iii) pressure effects. Additionally, inflow from the bottom of convection contributing to a growth of convection is also formally counted as a part of the dissipation term. The eddy dissipation is also included for a completeness. The order-of-magnitude analysis shows that the convective kinetic energy "dissipation" is dominated by the pressure effects, and it may be approximately described by Rayleigh damping with a constant time scale of the order of 102-103 s. The conclusion is also supported by a supplementary analysis of a cloud-resolving model (CRM) simulation. The Appendix discusses how the loss term ("dissipation") of the convective kinetic energy is qualitatively different from the conventional eddy-dissipation process found in turbulent flows.

  11. A dynamic subgrid scale model for Large Eddy Simulations based on the Mori-Zwanzig formalism

    Science.gov (United States)

    Parish, Eric J.; Duraisamy, Karthik

    2017-11-01

    The development of reduced models for complex multiscale problems remains one of the principal challenges in computational physics. The optimal prediction framework of Chorin et al. [1], which is a reformulation of the Mori-Zwanzig (M-Z) formalism of non-equilibrium statistical mechanics, provides a framework for the development of mathematically-derived reduced models of dynamical systems. Several promising models have emerged from the optimal prediction community and have found application in molecular dynamics and turbulent flows. In this work, a new M-Z-based closure model that addresses some of the deficiencies of existing methods is developed. The model is constructed by exploiting similarities between two levels of coarse-graining via the Germano identity of fluid mechanics and by assuming that memory effects have a finite temporal support. The appeal of the proposed model, which will be referred to as the 'dynamic-MZ-τ' model, is that it is parameter-free and has a structural form imposed by the mathematics of the coarse-graining process (rather than the phenomenological assumptions made by the modeler, such as in classical subgrid scale models). To promote the applicability of M-Z models in general, two procedures are presented to compute the resulting model form, helping to bypass the tedious error-prone algebra that has proven to be a hindrance to the construction of M-Z-based models for complex dynamical systems. While the new formulation is applicable to the solution of general partial differential equations, demonstrations are presented in the context of Large Eddy Simulation closures for the Burgers equation, decaying homogeneous turbulence, and turbulent channel flow. The performance of the model and validity of the underlying assumptions are investigated in detail.

  12. A nonlinear structural subgrid-scale closure for compressible MHD Part II: a priori comparison on turbulence simulation data

    CERN Document Server

    Grete, P; Schmidt, W; Schleicher, D R G

    2016-01-01

    Even though compressible plasma turbulence is encountered in many astrophysical phenomena, its effect is often not well understood. Furthermore, direct numerical simulations are typically not able to reach the extreme parameters of these processes. For this reason, large-eddy simulations (LES), which only simulate large and intermediate scales directly, are employed. The smallest, unresolved scales and the interactions between small and large scales are introduced by means of a subgrid-scale (SGS) model. We propose and verify a new set of nonlinear SGS closures for future application as an SGS model in LES of compressible magnetohydrodynamics (MHD). We use 15 simulations (without explicit SGS model) of forced, isotropic, homogeneous turbulence with varying sonic Mach number $\\mathrm{M_s} = 0.2$ to $20$ as reference data for the most extensive \\textit{a priori} tests performed so far in literature. In these tests we explicitly filter the reference data and compare the performance of the new closures against th...

  13. A nonlinear structural subgrid-scale closure for compressible MHD Part I: derivation and energy dissipation properties

    CERN Document Server

    Vlaykov, Dimitar G; Schmidt, Wolfram; Schleicher, Dominik R G

    2016-01-01

    Compressible magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical phenomena ranging from the intergalactic to the stellar scales. In studying them, numerical simulations are nearly inescapable, due to the large degree of nonlinearity involved. However the dynamical ranges of these phenomena are much larger than what is computationally accessible. In large eddy simulations (LES), the resulting limited resolution effects are addressed explicitly by introducing to the equations of motion additional terms associated with the unresolved, subgrid-scale (SGS) dynamics. This renders the system unclosed. We derive a set of nonlinear structural closures for the ideal MHD LES equations with particular emphasis on the effects of compressibility. The closures are based on a gradient expansion of the finite-resolution operator (W.K. Yeo CUP 1993, ed. Galperin & Orszag) and require no assumptions about the nature of the flow or magnetic field. Thus the scope of their applicability ranges from the sub- to ...

  14. Parameterization for subgrid-scale motion of ice-shelf calving fronts

    Directory of Open Access Journals (Sweden)

    T. Albrecht

    2011-01-01

    Full Text Available A parameterization for the motion of ice-shelf fronts on a Cartesian grid in finite-difference land-ice models is presented. The scheme prevents artificial thinning of the ice shelf at its edge, which occurs due to the finite resolution of the model. The intuitive numerical implementation diminishes numerical dispersion at the ice front and enables the application of physical boundary conditions to improve the calculation of stress and velocity fields throughout the ice-sheet-shelf system. Numerical properties of this subgrid modification are assessed in the Potsdam Parallel Ice Sheet Model (PISM-PIK for different geometries in one and two horizontal dimensions and are verified against an analytical solution in a flow-line setup.

  15. One-equation sub-grid scale (SGS) modelling for Euler-Euler large eddy simulation (EELES) of dispersed bubbly flow

    NARCIS (Netherlands)

    Niceno, B.; Dhotre, M.T.; Deen, N.G.

    2008-01-01

    In this work, we have presented a one-equation model for sub-grid scale (SGS) kinetic energy and applied it for an Euler-Euler large eddy simulation (EELES) of a bubble column reactor. The one-equation model for SGS kinetic energy shows improved predictions over the state-of-the-art dynamic

  16. Impact of Sub-grid Soil Textural Properties on Simulations of Hydrological Fluxes at the Continental Scale Mississippi River Basin

    Science.gov (United States)

    Kumar, R.; Samaniego, L. E.; Livneh, B.

    2013-12-01

    Knowledge of soil hydraulic properties such as porosity and saturated hydraulic conductivity is required to accurately model the dynamics of near-surface hydrological processes (e.g. evapotranspiration and root-zone soil moisture dynamics) and provide reliable estimates of regional water and energy budgets. Soil hydraulic properties are commonly derived from pedo-transfer functions using soil textural information recorded during surveys, such as the fractions of sand and clay, bulk density, and organic matter content. Typically large scale land-surface models are parameterized using a relatively coarse soil map with little or no information on parametric sub-grid variability. In this study we analyze the impact of sub-grid soil variability on simulated hydrological fluxes over the Mississippi River Basin (≈3,240,000 km2) at multiple spatio-temporal resolutions. A set of numerical experiments were conducted with the distributed mesoscale hydrologic model (mHM) using two soil datasets: (a) the Digital General Soil Map of the United States or STATSGO2 (1:250 000) and (b) the recently collated Harmonized World Soil Database based on the FAO-UNESCO Soil Map of the World (1:5 000 000). mHM was parameterized with the multi-scale regionalization technique that derives distributed soil hydraulic properties via pedo-transfer functions and regional coefficients. Within the experimental framework, the 3-hourly model simulations were conducted at four spatial resolutions ranging from 0.125° to 1°, using meteorological datasets from the NLDAS-2 project for the time period 1980-2012. Preliminary results indicate that the model was able to capture observed streamflow behavior reasonably well with both soil datasets, in the major sub-basins (i.e. the Missouri, the Upper Mississippi, the Ohio, the Red, and the Arkansas). However, the spatio-temporal patterns of simulated water fluxes and states (e.g. soil moisture, evapotranspiration) from both simulations, showed marked

  17. Resolution-dependent behavior of subgrid-scale vertical transport in the Zhang-McFarlane convection parameterization

    Science.gov (United States)

    Xiao, Heng; Gustafson, William I.; Hagos, Samson M.; Wu, Chien-Ming; Wan, Hui

    2015-06-01

    To better understand the behavior of quasi-equilibrium-based convection parameterizations at higher resolution, we use a diagnostic framework to examine the resolution-dependence of subgrid-scale vertical transport of moist static energy as parameterized by the Zhang-McFarlane convection parameterization (ZM). Grid-scale input to ZM is supplied by coarsening output from cloud-resolving model (CRM) simulations onto subdomains ranging in size from 8 × 8 to 256 × 256 km2. Then the ZM-based parameterization of vertical transport of moist static energy for scales smaller than the subdomain size (w'h'>¯ZM) are compared to those directly calculated from the CRM simulations (w'h'>¯CRM) for different subdomain sizes. The ensemble mean w'h'>¯CRM decreases by more than half as the subdomain size decreases from 128 to 8 km across while w'h'>¯ZM decreases with subdomain size only for strong convection cases and increases for weaker cases. The resolution dependence of w'h'>¯ZM is determined by the positive-definite grid-scale tendency of convective available potential energy (CAPE) in the convective quasi-equilibrium (QE) closure. Further analysis shows the actual grid-scale tendency of CAPE (before taking the positive definite value) and w'h'>¯CRM behave very similarly as the subdomain size changes because they are both tied to grid-scale advective tendencies. We can improve the resolution dependence of w'h'>¯ZM significantly by averaging the grid-scale tendency of CAPE over an appropriately large area surrounding each subdomain before taking its positive definite value. Even though the ensemble mean w'h'>¯CRM decreases with increasing resolution, its variability increases dramatically. w'h'>¯ZM cannot capture such increase in the variability, suggesting the need for stochastic treatment of convection at relatively high spatial resolution (8 or 16 km).

  18. Large Eddy Simulation of an SD7003 Airfoil: Effects of Reynolds number and Subgrid-scale modeling

    Science.gov (United States)

    Sarlak, Hamid

    2017-05-01

    This paper presents results of a series of numerical simulations in order to study aerodynamic characteristics of the low Reynolds number Selig-Donovan airfoil, SD7003. Large Eddy Simulation (LES) technique is used for all computations at chord-based Reynolds numbers 10,000, 24,000 and 60,000 and simulations have been performed to primarily investigate the role of sub-grid scale (SGS) modeling on the dynamics of flow generated over the airfoil, which has not been dealt with in great detail in the past. It is seen that simulations are increasingly getting influenced by SGS modeling with increasing the Reynolds number, and the effect is visible even at a relatively low chord-Reynolds number of 60,000. Among the tested models, the dynamic Smagorinsky gives the poorest predictions of the flow, with overprediction of lift and a larger separation on airfoils suction side. Among various models, the implicit LES offers closest pressure distribution predictions compared with literature.

  19. Assessment of sub-grid scale dispersion closure with regularized deconvolution method in a particle-laden turbulent jet

    Science.gov (United States)

    Wang, Qing; Zhao, Xinyu; Ihme, Matthias

    2017-11-01

    Particle-laden turbulent flows are important in numerous industrial applications, such as spray combustion engines, solar energy collectors etc. It is of interests to study this type of flows numerically, especially using large-eddy simulations (LES). However, capturing the turbulence-particle interaction in LES remains challenging due to the insufficient representation of the effect of sub-grid scale (SGS) dispersion. In the present work, a closure technique for the SGS dispersion using regularized deconvolution method (RDM) is assessed. RDM was proposed as the closure for the SGS dispersion in a counterflow spray that is studied numerically using finite difference method on a structured mesh. A presumed form of LES filter is used in the simulations. In the present study, this technique has been extended to finite volume method with an unstructured mesh, where no presumption on the filter form is required. The method is applied to a series of particle-laden turbulent jets. Parametric analyses of the model performance are conducted for flows with different Stokes numbers and Reynolds numbers. The results from LES will be compared against experiments and direct numerical simulations (DNS).

  20. Exploring the Limits of the Dynamic Procedure for Modeling Subgrid-Scale Stresses in LES of Inhomogeneous Flows.

    Science.gov (United States)

    Le, A.-T.; Kim, J.; Coleman, G.

    1996-11-01

    One of the primary reasons dynamic subgrid-scale (SGS) models are more successful than those that are `hand-tuned' is thought to be their insensitivity to numerical and modeling parameters. Jiménez has recently demonstrated that large-eddy simulations (LES) of decaying isotropic turbulence using a dynamic Smagorinsky model yield correct decay rates -- even when the model is subjected to a range of artificial perturbations. The objective of the present study is to determine to what extent this `self-adjusting' feature of dynamic SGS models is found in LES of inhomogeneous flows. The effects of numerical and modeling parameters on the accuracy of LES solutions of fully developed and developing turbulent channel flow are studied, using a spectral code and various dynamic models (including those of Lilly et al. and Meneveau et al.); other modeling parameters tested include the filter-width ratio and the effective magnitude of the Smagorinsky coefficient. Numerical parameters include the form of the convective term and the type of test filter (sharp-cutoff versus tophat). The resulting LES statistics are found to be surprisingly sensitive to the various parameter choices, which implies that more care than is needed for homogeneous-flow simulations must be exercised when performing LES of inhomogeneous flows.

  1. Effect of Considering Sub-Grid Scale Uncertainties on the Forecasts of a High-Resolution Limited Area Ensemble Prediction System

    Science.gov (United States)

    Kim, SeHyun; Kim, Hyun Mee

    2017-05-01

    The ensemble prediction system (EPS) is widely used in research and at operation center because it can represent the uncertainty of predicted atmospheric state and provide information of probabilities. The high-resolution (so-called "convection-permitting") limited area EPS can represent the convection and turbulence related to precipitation phenomena in more detail, but it is also much sensitive to small-scale or sub-grid scale processes. The convection and turbulence are represented using physical processes in the model and model errors occur due to sub-grid scale processes that were not resolved. This study examined the effect of considering sub-grid scale uncertainties using the high-resolution limited area EPS of the Korea Meteorological Administration (KMA). The developed EPS has horizontal resolution of 3 km and 12 ensemble members. The initial and boundary conditions were provided by the global model. The Random Parameters (RP) scheme was used to represent sub-grid scale uncertainties. The EPSs with and without the RP scheme were developed and the results were compared. During the one month period of July, 2013, a significant difference was shown in the spread of 1.5 m temperature and the Root Mean Square Error and spread of 10 m zonal wind due to application of the RP scheme. For precipitation forecast, the precipitation tended to be overestimated relative to the observation when the RP scheme was applied. Moreover, the forecast became more accurate for heavy precipitations and the longer forecast lead times. For two heavy rainfall cases occurred during the research period, the higher Equitable Threat Score was observed for heavy precipitations in the system with the RP scheme compared to the one without, demonstrating consistency with the statistical results for the research period. Therefore, the predictability for heavy precipitation phenomena that affected the Korean Peninsula increases if the RP scheme is used to consider sub-grid scale uncertainties

  2. Sub-grid scale models for discontinuous Galerkin methods based on the Mori-Zwanzig formalism

    Science.gov (United States)

    Parish, Eric; Duraisamy, Karthk

    2017-11-01

    The optimal prediction framework of Chorin et al., which is a reformulation of the Mori-Zwanzig (M-Z) formalism of non-equilibrium statistical mechanics, provides a framework for the development of mathematically-derived closure models. The M-Z formalism provides a methodology to reformulate a high-dimensional Markovian dynamical system as a lower-dimensional, non-Markovian (non-local) system. In this lower-dimensional system, the effects of the unresolved scales on the resolved scales are non-local and appear as a convolution integral. The non-Markovian system is an exact statement of the original dynamics and is used as a starting point for model development. In this work, we investigate the development of M-Z-based closures model within the context of the Variational Multiscale Method (VMS). The method relies on a decomposition of the solution space into two orthogonal subspaces. The impact of the unresolved subspace on the resolved subspace is shown to be non-local in time and is modeled through the M-Z-formalism. The models are applied to hierarchical discontinuous Galerkin discretizations. Commonalities between the M-Z closures and conventional flux schemes are explored. This work was supported in part by AFOSR under the project ''LES Modeling of Non-local effects using Statistical Coarse-graining'' with Dr. Jean-Luc Cambier as the technical monitor.

  3. Simple lattice Boltzmann subgrid-scale model for convectional flows with high Rayleigh numbers within an enclosed circular annular cavity

    Science.gov (United States)

    Chen, Sheng; Tölke, Jonas; Krafczyk, Manfred

    2009-08-01

    Natural convection within an enclosed circular annular cavity formed by two concentric vertical cylinders is of fundamental interest and practical importance. Generally, the assumption of axisymmetric thermal flow is adopted for simulating such natural convections and the validity of the assumption of axisymmetric thermal flow is still held even for some turbulent convection. Usually the Rayleigh numbers (Ra) of realistic flows are very high. However, the work to design suitable and efficient lattice Boltzmann (LB) models on such flows is quite rare. To bridge the gap, in this paper a simple LB subgrid-scale (SGS) model, which is based on our recent work [S. Chen, J. Tölke, and M. Krafczyk, Phys. Rev. E 79, 016704 (2009); S. Chen, J. Tölke, S. Geller, and M. Krafczyk, Phys. Rev. E 78, 046703 (2008)], is proposed for simulating convectional flow with high Ra within an enclosed circular annular cavity. The key parameter for the SGS model can be quite easily and efficiently evaluated by the present model. The numerical experiments demonstrate that the present model works well for a large range of Ra and Prandtl number (Pr). Though in the present study a popularly used static Smagorinsky turbulence model is adopted to demonstrate how to develop a LB SGS model for simulating axisymmetric thermal flows with high Ra, other state-of-the-art turbulence models can be incorporated into the present model in the same way. In addition, the present model can be extended straightforwardly to simulate other axisymmetric convectional flows with high Ra, for example, turbulent convection with internal volumetric heat generation in a vertical cylinder, which is an important simplified representation of a nuclear reactor.

  4. A Dynamic Subgrid Scale Model for Large Eddy Simulations Based on the Mori-Zwanzig Formalism

    CERN Document Server

    Parish, Eric J

    2016-01-01

    The development of reduced models for complex systems that lack scale separation remains one of the principal challenges in computational physics. The optimal prediction framework of Chorin et al., which is a reformulation of the Mori-Zwanzig (M-Z) formalism of non-equilibrium statistical mechanics, provides a methodology for the development of mathematically-derived reduced models of dynamical systems. Several promising models have emerged from the optimal prediction community and have found application in molecular dynamics and turbulent flows. In this work, a novel M-Z-based closure model that addresses some of the deficiencies of existing methods is developed. The model is constructed by exploiting similarities between two levels of coarse-graining via the Germano identity of fluid mechanics and by assuming that memory effects have a finite temporal support. The appeal of the proposed model, which will be referred to as the `dynamic-$\\tau$' model, is that it is parameter-free and has a structural form imp...

  5. Sub-grid scale representation of vegetation in global land surface schemes: implications for estimation of the terrestrial carbon sink

    Directory of Open Access Journals (Sweden)

    J. R. Melton

    2014-02-01

    Full Text Available Terrestrial ecosystem models commonly represent vegetation in terms of plant functional types (PFTs and use their vegetation attributes in calculations of the energy and water balance as well as to investigate the terrestrial carbon cycle. Sub-grid scale variability of PFTs in these models is represented using different approaches with the "composite" and "mosaic" approaches being the two end-members. The impact of these two approaches on the global carbon balance has been investigated with the Canadian Terrestrial Ecosystem Model (CTEM v 1.2 coupled to the Canadian Land Surface Scheme (CLASS v 3.6. In the composite (single-tile approach, the vegetation attributes of different PFTs present in a grid cell are aggregated and used in calculations to determine the resulting physical environmental conditions (soil moisture, soil temperature, etc. that are common to all PFTs. In the mosaic (multi-tile approach, energy and water balance calculations are performed separately for each PFT tile and each tile's physical land surface environmental conditions evolve independently. Pre-industrial equilibrium CLASS-CTEM simulations yield global totals of vegetation biomass, net primary productivity, and soil carbon that compare reasonably well with observation-based estimates and differ by less than 5% between the mosaic and composite configurations. However, on a regional scale the two approaches can differ by > 30%, especially in areas with high heterogeneity in land cover. Simulations over the historical period (1959–2005 show different responses to evolving climate and carbon dioxide concentrations from the two approaches. The cumulative global terrestrial carbon sink estimated over the 1959–2005 period (excluding land use change (LUC effects differs by around 5% between the two approaches (96.3 and 101.3 Pg, for the mosaic and composite approaches, respectively and compares well with the observation-based estimate of 82.2 ± 35 Pg C over the same

  6. Assessment of subgrid-scale models with a large-eddy simulation-dedicated experimental database: The pulsatile impinging jet in turbulent cross-flow

    Science.gov (United States)

    Baya Toda, Hubert; Cabrit, Olivier; Truffin, Karine; Bruneaux, Gilles; Nicoud, Franck

    2014-07-01

    Large-Eddy Simulation (LES) in complex geometries and industrial applications like piston engines, gas turbines, or aircraft engines requires the use of advanced subgrid-scale (SGS) models able to take into account the main flow features and the turbulence anisotropy. Keeping this goal in mind, this paper reports a LES-dedicated experiment of a pulsatile hot-jet impinging a flat-plate in the presence of a cold turbulent cross-flow. Unlike commonly used academic test cases, this configuration involves different flow features encountered in complex configurations: shear/rotating regions, stagnation point, wall-turbulence, and the propagation of a vortex ring along the wall. This experiment was also designed with the aim to use quantitative and nonintrusive optical diagnostics such as Particle Image Velocimetry, and to easily perform a LES involving a relatively simple geometry and well-controlled boundary conditions. Hence, two eddy-viscosity-based SGS models are investigated: the dynamic Smagorinsky model [M. Germano, U. Piomelli, P. Moin, and W. Cabot, "A dynamic subgrid-scale eddy viscosity model," Phys. Fluids A 3(7), 1760-1765 (1991)] and the σ-model [F. Nicoud, H. B. Toda, O. Cabrit, S. Bose, and J. Lee, "Using singular values to build a subgrid-scale model for large eddy simulations," Phys. Fluids 23(8), 085106 (2011)]. Both models give similar results during the first phase of the experiment. However, it was found that the dynamic Smagorinsky model could not accurately predict the vortex-ring propagation, while the σ-model provides a better agreement with the experimental measurements. Setting aside the implementation of the dynamic procedure (implemented here in its simplest form, i.e., without averaging over homogeneous directions and with clipping of negative values to ensure numerical stability), it is suggested that the mitigated predictions of the dynamic Smagorinsky model are due to the dynamic constant, which strongly depends on the mesh resolution

  7. An explicit relaxation filtering framework based upon Perona-Malik anisotropic diffusion for shock capturing and subgrid scale modeling of Burgers turbulence

    CERN Document Server

    Maulik, Romit

    2016-01-01

    In this paper, we introduce a relaxation filtering closure approach to account for subgrid scale effects in explicitly filtered large eddy simulations using the concept of anisotropic diffusion. We utilize the Perona-Malik diffusion model and demonstrate its shock capturing ability and spectral performance for solving the Burgers turbulence problem, which is a simplified prototype for more realistic turbulent flows showing the same quadratic nonlinearity. Our numerical assessments present the behavior of various diffusivity functions in conjunction with a detailed sensitivity analysis with respect to the free modeling parameters. In comparison to direct numerical simulation (DNS) and under-resolved DNS results, we find that the proposed closure model is efficient in the prevention of energy accumulation at grid cut-off and is also adept at preventing any possible spurious numerical oscillations due to shock formation under the optimal parameter choices. In contrast to other relaxation filtering approaches, it...

  8. Modeling lightning-NOx chemistry on a sub-grid scale in a global chemical transport model

    Directory of Open Access Journals (Sweden)

    A. Gressent

    2016-05-01

    Full Text Available For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM to parameterize the effects of the nonlinear reactions occurring within high concentrated NOx plumes from lightning NOx emissions (LNOx in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NOx–O3 chemical interactions, and the fractions of NOx conversion into HNO3 within the plume. Parameter estimates were made using the Dynamical Simple Model of Atmospheric Chemical Complexity (DSMACC box model, simple plume dispersion simulations, and the 3-D Meso-NH (non-hydrostatic mesoscale atmospheric model. In order to assess the impact of the LNOx plume approach on the NOx and O3 distributions on a large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNOx parameterization implies an NOx and O3 decrease on a large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over central Africa in July and a relative increase downwind of LNOx emissions (up to 18 and 2 % for NOx and O3, respectively, in July. The calculated variability in NOx and O3 mixing ratios around the mean value according to the known uncertainties in the parameter estimates is at a maximum over continental tropical regions with ΔNOx [−33.1, +29.7] ppt and ΔO3 [−1.56, +2.16] ppb, in January, and ΔNOx [−14.3, +21] ppt and ΔO3 [−1.18, +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows us (i to reproduce a more realistic lightning NOx chemistry leading to better NOx and O3 distributions on the large scale and (ii to focus on other improvements to reduce remaining uncertainties from processes

  9. Recursive renormalization group theory based subgrid modeling

    Science.gov (United States)

    Zhou, YE

    1991-01-01

    Advancing the knowledge and understanding of turbulence theory is addressed. Specific problems to be addressed will include studies of subgrid models to understand the effects of unresolved small scale dynamics on the large scale motion which, if successful, might substantially reduce the number of degrees of freedom that need to be computed in turbulence simulation.

  10. Large Eddy Simulations of a Premixed Jet Combustor Using Flamelet-Generated Manifolds: Effects of Heat Loss and Subgrid-Scale Models

    KAUST Repository

    Hernandez Perez, Francisco E.

    2017-01-05

    Large eddy simulations of a turbulent premixed jet flame in a confined chamber were conducted using the flamelet-generated manifold technique for chemistry tabulation. The configuration is characterized by an off-center nozzle having an inner diameter of 10 mm, supplying a lean methane-air mixture with an equivalence ratio of 0.71 and a mean velocity of 90 m/s, at 573 K and atmospheric pressure. Conductive heat loss is accounted for in the manifold via burner-stabilized flamelets and the subgrid-scale (SGS) turbulencechemistry interaction is modeled via presumed probability density functions. Comparisons between numerical results and measured data show that a considerable improvement in the prediction of temperature is achieved when heat losses are included in the manifold, as compared to the adiabatic one. Additional improvement in the temperature predictions is obtained by incorporating radiative heat losses. Moreover, further enhancements in the LES predictions are achieved by employing SGS models based on transport equations, such as the SGS turbulence kinetic energy equation with dynamic coefficients. While the numerical results display good agreement up to a distance of 4 nozzle diameters downstream of the nozzle exit, the results become less satisfactory along the downstream, suggesting that further improvements in the modeling are required, among which a more accurate model for the SGS variance of progress variable can be relevant.

  11. Intercomparison of different subgrid-scale models for the Large Eddy Simulation of the diurnal evolution of the atmospheric boundary layer during the Wangara experiment

    Science.gov (United States)

    Dall'Ozzo, C.; Carissimo, B.; Musson-Genon, L.; Dupont, E.; Milliez, M.

    2012-04-01

    The study of a whole diurnal cycle of the atmospheric boundary layer evolving through unstable, neutral and stable states is essential to test a model applicable to the dispersion of pollutants. Consequently a LES of a diurnal cycle is performed and compared to observations from the Wangara experiment (Day 33-34). All simulations are done with Code_Saturne [1] an open source CFD code. The synthetic eddy method (SEM) [2] is implemented to initialize turbulence at the beginning of the simulation. Two different subgrid-scale (SGS) models are tested: the Smagorinsky model [3],[4] and the dynamical Wong and Lilly model [5]. The first one, the most classical, uses a Smagorinsky constant Cs to parameterize the dynamical turbulent viscosity while the second one relies on a variable C. Cs remains insensitive to the atmospheric stability level in contrary to the parameter C determined by the Wong and Lilly model. It is based on the error minimization of the difference between the tensors of the resolved turbulent stress (Lij) and the difference of the SGS stress tensors at two different filter scales (Mij). Furthermore, the thermal eddy diffusivity, as opposed to the Smagorinsky model, is calculated with a dynamical Prandtl number determination. The results are confronted to previous simulations from Basu et al. (2008) [6], using a locally averaged scale-dependent dynamic (LASDD) SGS model, and to previous RANS simulations. The accuracy in reproducing the experimental atmospheric conditions is discussed, especially regarding the night time low-level jet formation. In addition, the benefit of the utilization of a coupled radiative model is discussed.

  12. Predictions from high scale mixing unification hypothesis

    Indian Academy of Sciences (India)

    2016-01-09

    Jan 9, 2016 ... Starting with 'high scale mixing unification' hypothesis, we investigate the renormalization group evolution of mixing parameters and masses for both Dirac and Majorana-type neutrinos. Following this hypothesis, the PMNS mixing parameters are taken to be identical to the CKM ones at a unifying high ...

  13. Advanced subgrid-scale modeling for convection-dominated species transport at fluid interfaces with application to mass transfer from rising bubbles

    Science.gov (United States)

    Weiner, Andre; Bothe, Dieter

    2017-10-01

    This paper presents a novel subgrid scale (SGS) model for simulating convection-dominated species transport at deformable fluid interfaces. One possible application is the Direct Numerical Simulation (DNS) of mass transfer from rising bubbles. The transport of a dissolving gas along the bubble-liquid interface is determined by two transport phenomena: convection in streamwise direction and diffusion in interface normal direction. The convective transport for technical bubble sizes is several orders of magnitude higher, leading to a thin concentration boundary layer around the bubble. A true DNS, fully resolving hydrodynamic and mass transfer length scales results in infeasible computational costs. Our approach is therefore a DNS of the flow field combined with a SGS model to compute the mass transfer between bubble and liquid. An appropriate model-function is used to compute the numerical fluxes on all cell faces of an interface cell. This allows to predict the mass transfer correctly even if the concentration boundary layer is fully contained in a single cell layer around the interface. We show that the SGS-model reduces the resolution requirements at the interface by a factor of ten and more. The integral flux correction is also applicable to other thin boundary layer problems. Two flow regimes are investigated to validate the model. A semi-analytical solution for creeping flow is used to assess local and global mass transfer quantities. For higher Reynolds numbers ranging from Re = 100 to Re = 460 and Péclet numbers between Pe =104 and Pe = 4 ṡ106 we compare the global Sherwood number against correlations from literature. In terms of accuracy, the predicted mass transfer never deviates more than 4% from the reference values.

  14. High-Resolution Global Modeling of the Effects of Subgrid-Scale Clouds and Turbulence on Precipitating Cloud Systems

    Energy Technology Data Exchange (ETDEWEB)

    Bogenschutz, Peter [National Center for Atmospheric Research, Boulder, CO (United States); Moeng, Chin-Hoh [National Center for Atmospheric Research, Boulder, CO (United States)

    2015-10-13

    The PI’s at the National Center for Atmospheric Research (NCAR), Chin-Hoh Moeng and Peter Bogenschutz, have primarily focused their time on the implementation of the Simplified-Higher Order Turbulence Closure (SHOC; Bogenschutz and Krueger 2013) to the Multi-scale Modeling Framework (MMF) global model and testing of SHOC on deep convective cloud regimes.

  15. Impact of an additional radiative CO2 cooling induced by subgrid-scale gravity waves in the middle and upper atmosphere

    Science.gov (United States)

    Medvedev, A. S.; Yigit, E.; Kutepov, A.; Feofilov, A.

    2011-12-01

    Atmospheric fluctuations produced by GWs are a substantial source of momentum and energy in the thermosphere (Yigit et al., 2009). These fluctuations also affect radiative transfer and, ultimately, the radiative heating/cooling rates. Recently, Kutepov et al. (2007) developed a methodology to account for radiative effects of subgrid-scale GWs not captured by general circulation models (GCMs). It has been extended by Kutepov et al (2011) to account not only for wave-induced variations of temperature, but also of CO2 and atomic oxygen. It was shown that these GWs can cause additional cooling of up to 3 K/day around mesopause. A key parameter for calculating the additional cooling is the temperature variance associated with GWs, which is a subproduct of conventional GW schemes. In this study, the parameterization of Kutepov et al. (2011) has been implemented into a 3-D comprehensive GCM that incorporates the effects of unresolved GWs via the extended nonlinear scheme of Yigit et al. (2008). Simulated net effects of the additional radiative CO2 cooling on the temperature and wind in the mesosphere and lower thermosphere are presented and discussed for solstice conditions. 1. Kutepov, A. A, A. G. Feofilov, A. S. Medvedev, A. W. A. Pauldrach, and P. Hartogh (2007), Geophys. Res. Lett. 34, L24807, doi:10.1029/2007GL032392. 2. Kutepov, A. A., A. G. Feofilov, A. S. Medvedev, U. Berger, and M. Kaufmann (2011), submitted to Geophys. Res. Letts. 3. Yigit, E., A. D. Aylward, and A. S. Medvedev (2008), J. Geophys. Res., 113, D19106, doi:10.1029/2008JD010135. 4. Yigit, E., A. S. Medvedev, A. D. Aylward, P. Hartogh, and M. J. Harris (2009), J. Geophys. Res., 114, D07101, doi:10.1029/2008JD011132.

  16. Effect of reactions in small eddies on biomass gasification with eddy dissipation concept - Sub-grid scale reaction model.

    Science.gov (United States)

    Chen, Juhui; Yin, Weijie; Wang, Shuai; Meng, Cheng; Li, Jiuru; Qin, Bai; Yu, Guangbin

    2016-07-01

    Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Predicting the impacts of fishing canals on Floodplain Dynamics in Northern Cameroon using a small-scale sub-grid hydraulic model

    Science.gov (United States)

    Shastry, A. R.; Durand, M. T.; Fernandez, A.; Hamilton, I.; Kari, S.; Labara, B.; Laborde, S.; Mark, B. G.; Moritz, M.; Neal, J. C.; Phang, S. C.

    2015-12-01

    Modeling Regime Shifts in the Logone floodplain (MORSL) is an ongoing interdisciplinary project at The Ohio State University studying the ecological, social and hydrological system of the region. This floodplain, located in Northern Cameroon, is part of the Lake Chad basin. Between September and October the floodplain is inundated by the overbank flow from the Logone River, which is important for agriculture and fishing. Fishermen build canals to catch fish during the flood's recession to the river by installing fishnets at the intersection of the canals and the river. Fishing canals thus connect the river to natural depressions of the terrain, which act as seasonal ponds during this part of the year. Annual increase in the number of canals affect hydraulics and hence fishing in the region. In this study, the Bara region (1 km2) of the Logone floodplain, through which Lorome Mazra flows, is modeled using LISFLOOD-FP, a raster-based model with sub-grid parameterizations of canals. The aim of the study is to find out how the small-scale, local features like canals and fishnets govern the flow, so that it can be incorporated in a large-scale model of the floodplain at a coarser spatial resolution. We will also study the effect of increasing number of canals on the flooding pattern. We use a simplified version of the hydraulic system at a grid-cell size of 30-m, using synthetic topography, parameterized fishing canals, and representing fishnets as trash screens. The inflow at Bara is obtained from a separate, lower resolution (1-km grid-cell) model run, which is forced by daily discharge records obtained from Katoa, located about 25-km to the south of Bara. The model appropriately captures the rise and recession of the annual flood, supporting use of the LISFLOOD-FP approach. Predicted water levels at specific points in the river, the canals, the depression and the floodplain will be compared to field measured heights of flood recession in Bara, November 2014.

  18. Birefringent dispersive FDTD subgridding scheme

    OpenAIRE

    De Deckere, B; Van Londersele, Arne; De Zutter, Daniël; Vande Ginste, Dries

    2016-01-01

    A novel 2D finite difference time domain (FDTD) subgridding method is proposed, only subject to the Courant limit of the coarse grid. By making mu or epsilon inside the subgrid dispersive, unconditional stability is induced at the cost of a sparse, implicit set of update equations. By only adding dispersion along preferential directions, it is possible to dramatically reduce the rank of the matrix equation that needs to be solved.

  19. A subgrid parameterization scheme for precipitation

    Directory of Open Access Journals (Sweden)

    S. Turner

    2012-04-01

    Full Text Available With increasing computing power, the horizontal resolution of numerical weather prediction (NWP models is improving and today reaches 1 to 5 km. Nevertheless, clouds and precipitation formation are still subgrid scale processes for most cloud types, such as cumulus and stratocumulus. Subgrid scale parameterizations for water vapor condensation have been in use for many years and are based on a prescribed probability density function (PDF of relative humidity spatial variability within the model grid box, thus providing a diagnosis of the cloud fraction. A similar scheme is developed and tested here. It is based on a prescribed PDF of cloud water variability and a threshold value of liquid water content for droplet collection to derive a rain fraction within the model grid. Precipitation of rainwater raises additional concerns relative to the overlap of cloud and rain fractions, however. The scheme is developed following an analysis of data collected during field campaigns in stratocumulus (DYCOMS-II and fair weather cumulus (RICO and tested in a 1-D framework against large eddy simulations of these observed cases. The new parameterization is then implemented in a 3-D NWP model with a horizontal resolution of 2.5 km to simulate real cases of precipitating cloud systems over France.

  20. Preliminary Scaling Estimate for Select Small Scale Mixing Demonstration Tests

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Beric E.; Fort, James A.; Gauglitz, Phillip A.; Rector, David R.; Schonewill, Philip P.

    2013-09-12

    The Hanford Site double-shell tank (DST) system provides the staging location for waste that will be transferred to the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Specific WTP acceptance criteria for waste feed delivery describe the physical and chemical characteristics of the waste that must be met before the waste is transferred from the DSTs to the WTP. One of the more challenging requirements relates to the sampling and characterization of the undissolved solids (UDS) in a waste feed DST because the waste contains solid particles that settle and their concentration and relative proportion can change during the transfer of the waste in individual batches. A key uncertainty in the waste feed delivery system is the potential variation in UDS transferred in individual batches in comparison to an initial sample used for evaluating the acceptance criteria. To address this uncertainty, a number of small-scale mixing tests have been conducted as part of Washington River Protection Solutions’ Small Scale Mixing Demonstration (SSMD) project to determine the performance of the DST mixing and sampling systems.

  1. The Sensitivity of Simulated Competition Between Different Plant Functional Types to Subgrid Scale Representation of Vegetation in a Land Surface Model

    Science.gov (United States)

    Shrestha, R. K.; Arora, V.; Melton, J. R.

    2014-12-01

    Vegetation is a dynamic component of the earth system that affects weather and climate at hourly to centennial time scales. However, most current dynamic vegetation models do not explicitly simulate competition among Plant Functional Types (PFTs). Here we use the coupled CLASS-CTEM model (Canadian Land Surface Scheme coupled to Canadian Terrestrial Ecosystem Model) to explicitly simulate competition between nine PFTs for available space using a modified version of Lotka - Volterra (LV) predator-prey equations. The nine PFTs include evergreen and deciduous needleleaf trees, evergreen and cold and drought deciduous broadleaf trees and C3 and C4 crops and grasses. The CLASS-CTEM model can be configured either in the composite (single tile) or the mosaic (multiple tiles) mode. Our results show that the model is sensitive to the chosen mode. The simulated fractional coverage of PFTs are similar between two approaches at some locations whereas at the other locations the two approaches yield different results. The simulated fractional coverage of PFTs are also compared with the available observations-based estimates. Simulated results at selected locations across the globe show that the model is able to realistically simulate the fractional coverage of tree and grass PFTs and the bare fraction, as well as the fractional coverage of individual tree and grass PFTs. Along with the observed patterns of vegetation distribution the CLASS-CTEM modelling framework is also able to simulate realistic succession patterns. Some differences remain and these are attributed to the coarse spatial resolution of the model (~3.75°) and the limited number of PFTs represented in the model.

  2. Subgrid Parameterization of the Soil Moisture Storage Capacity for a Distributed Rainfall-Runoff Model

    Directory of Open Access Journals (Sweden)

    Weijian Guo

    2015-05-01

    Full Text Available Spatial variability plays an important role in nonlinear hydrologic processes. Due to the limitation of computational efficiency and data resolution, subgrid variability is usually assumed to be uniform for most grid-based rainfall-runoff models, which leads to the scale-dependence of model performances. In this paper, the scale effect on the Grid-Xinanjiang model was examined. The bias of the estimation of precipitation, runoff, evapotranspiration and soil moisture at the different grid scales, along with the scale-dependence of the effective parameters, highlights the importance of well representing the subgrid variability. This paper presents a subgrid parameterization method to incorporate the subgrid variability of the soil storage capacity, which is a key variable that controls runoff generation and partitioning in the Grid-Xinanjiang model. In light of the similar spatial pattern and physical basis, the soil storage capacity is correlated with the topographic index, whose spatial distribution can more readily be measured. A beta distribution is introduced to represent the spatial distribution of the soil storage capacity within the grid. The results derived from the Yanduhe Basin show that the proposed subgrid parameterization method can effectively correct the watershed soil storage capacity curve. Compared to the original Grid-Xinanjiang model, the model performances are quite consistent at the different grid scales when the subgrid variability is incorporated. This subgrid parameterization method reduces the recalibration necessity when the Digital Elevation Model (DEM resolution is changed. Moreover, it improves the potential for the application of the distributed model in the ungauged basin.

  3. SCALE INTERACTION IN A MIXING LAYER. THE ROLE OF THE LARGE-SCALE GRADIENTS

    KAUST Repository

    Fiscaletti, Daniele

    2015-08-23

    The interaction between scales is investigated in a turbulent mixing layer. The large-scale amplitude modulation of the small scales already observed in other works depends on the crosswise location. Large-scale positive fluctuations correlate with a stronger activity of the small scales on the low speed-side of the mixing layer, and a reduced activity on the high speed-side. However, from physical considerations we would expect the scales to interact in a qualitatively similar way within the flow and across different turbulent flows. Therefore, instead of the large-scale fluctuations, the large-scale gradients modulation of the small scales has been additionally investigated.

  4. Subgrid Modeling Geomorphological and Ecological Processes in Salt Marsh Evolution

    Science.gov (United States)

    Shi, F.; Kirby, J. T., Jr.; Wu, G.; Abdolali, A.; Deb, M.

    2016-12-01

    Numerical modeling a long-term evolution of salt marshes is challenging because it requires an extensive use of computational resources. Due to the presence of narrow tidal creeks, variations of salt marsh topography can be significant over spatial length scales on the order of a meter. With growing availability of high-resolution bathymetry measurements, like LiDAR-derived DEM data, it is increasingly desirable to run a high-resolution model in a large domain and for a long period of time to get trends of sedimentation patterns, morphological change and marsh evolution. However, high spatial-resolution poses a big challenge in both computational time and memory storage, when simulating a salt marsh with dimensions of up to O(100 km^2) with a small time step. In this study, we have developed a so-called Pre-storage, Sub-grid Model (PSM, Wu et al., 2015) for simulating flooding and draining processes in salt marshes. The simulation of Brokenbridge salt marsh, Delaware, shows that, with the combination of the sub-grid model and the pre-storage method, over 2 orders of magnitude computational speed-up can be achieved with minimal loss of model accuracy. We recently extended PSM to include a sediment transport component and models for biomass growth and sedimentation in the sub-grid model framework. The sediment transport model is formulated based on a newly derived sub-grid sediment concentration equation following Defina's (2000) area-averaging procedure. Suspended sediment transport is modeled by the advection-diffusion equation in the coarse grid level, but the local erosion and sedimentation rates are integrated over the sub-grid level. The morphological model is based on the existing morphological model in NearCoM (Shi et al., 2013), extended to include organic production from the biomass model. The vegetation biomass is predicted by a simple logistic equation model proposed by Marani et al. (2010). The biomass component is loosely coupled with hydrodynamic and

  5. On the development of a subgrid CFD model for fire extinguishment

    Energy Technology Data Exchange (ETDEWEB)

    TIESZEN,SHELDON R.; LOPEZ,AMALIA R.

    2000-02-02

    A subgrid model is presented for use in CFD fire simulations to account for thermal suppressants and strain. The extinguishment criteria is based on the ratio of a local fluid-mechanics time-scale to a local chemical time-scale compared to an empirically-determined critical Damkohler number. Local extinction occurs if this time scale is exceeded, global fire extinguishment occurs when local extinction has occurred for all combusting cells. The fluid mechanics time scale is based on the Kolmogorov time scale and the chemical time scale is based on blowout of a perfectly stirred reactor. The input to the reactor is based on cell averaged temperatures, assumed stoichiometric fuel/air composition, and cell averaged suppressant concentrations including combustion products. A detailed chemical mechanism is employed. The chemical time-scale is precalculated and mixing rules are used to reduce the composition space that must be parameterized. Comparisons with experimental data for fire extinguishment in a flame-stabilizing, backward-facing step geometry indicates that the model is conservative for this condition.

  6. Quantification of marine aerosol subgrid variability and its correlation with clouds based on high-resolution regional modeling: Quantifying Aerosol Subgrid Variability

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Guangxing; Qian, Yun; Yan, Huiping; Zhao, Chun; Ghan, Steven J.; Easter, Richard C.; Zhang, Kai

    2017-06-16

    One limitation of most global climate models (GCMs) is that with the horizontal resolutions they typically employ, they cannot resolve the subgrid variability (SGV) of clouds and aerosols, adding extra uncertainties to the aerosol radiative forcing estimation. To inform the development of an aerosol subgrid variability parameterization, here we analyze the aerosol SGV over the southern Pacific Ocean simulated by the high-resolution Weather Research and Forecasting model coupled to Chemistry. We find that within a typical GCM grid, the aerosol mass subgrid standard deviation is 15% of the grid-box mean mass near the surface on a 1 month mean basis. The fraction can increase to 50% in the free troposphere. The relationships between the sea-salt mass concentration, meteorological variables, and sea-salt emission rate are investigated in both the clear and cloudy portion. Under clear-sky conditions, marine aerosol subgrid standard deviation is highly correlated with the standard deviations of vertical velocity, cloud water mixing ratio, and sea-salt emission rates near the surface. It is also strongly connected to the grid box mean aerosol in the free troposphere (between 2 km and 4 km). In the cloudy area, interstitial sea-salt aerosol mass concentrations are smaller, but higher correlation is found between the subgrid standard deviations of aerosol mass and vertical velocity. Additionally, we find that decreasing the model grid resolution can reduce the marine aerosol SGV but strengthen the correlations between the aerosol SGV and the total water mixing ratio (sum of water vapor, cloud liquid, and cloud ice mixing ratios).

  7. Polyethylene encapsulation of mixed wastes: Scale-up feasibility

    Energy Technology Data Exchange (ETDEWEB)

    Kalb, P.D.; Heiser, J.H.; Colombo, P.

    1991-12-31

    A polyethylene process for the improved encapsulation of radioactive, hazardous, and mixed wastes have been developed at Brookhaven National Laboratory (BNL). Improvements in waste loading and waste form performance have been demonstrated through bench-scale development and testing. Maximum waste loadings of up to 70 dry wt % mixed waste nitrate salt were achieved, compared with 13--20 dry wt % using conventional cement processes. Stability under anticipated storage and disposal conditions and compliance with applicable hazardous waste regulations were demonstrated through a series of lab-scale waste form performance tests. Full-scale demonstration of this process using actual or surrogate waste is currently planned. A scale-up feasibility test was successfully conducted, demonstrating the ability to process nitrate salts at production rates (up to 450 kg/hr) and the close agreement between bench- and full-scale process parameters. Cored samples from the resulting pilot-scale (114 liter) waste form were used to verify homogeneity and to provide additional specimens for confirmatory performance testing.

  8. Comparing turbulent mixing of biogenic VOC across model scale

    Science.gov (United States)

    Li, Y.; Barth, M. C.; Steiner, A. L.

    2016-12-01

    Vertical mixing of biogenic volatile organic compounds (BVOC) in the planetary boundary layer (PBL) is very important in simulating the formation of ozone, secondary organic aerosols (SOA), and climate feedbacks. To assess the representation of vertical mixing in the atmosphere for the Baltimore-Washington DISCOVER-AQ 2011 campaign, we use two models of different scale and turbulence representation: (1) the National Center for Atmospheric Research's Large Eddy Simulation (LES), and (2) the Weather Research and Forecasting-Chemistry (WRF-Chem) model to simulate regional meteorology and chemistry. For WRF-Chem, we evaluate the boundary layer schemes in the model at convection-permitting scales (4km). WRF-Chem simulated vertical profiles are compared with the results from turbulence-resolving LES model under similar meteorological and chemical environment. The influence of clouds on gas and aqueous species and the impact of cloud processing at both scales are evaluated. Temporal evolutions of a surface-to-cloud concentration ratio are calculated to determine the capability of BVOC vertical mixing in WRF-Chem.

  9. Scale interactions in a mixing layer – the role of the large-scale gradients

    KAUST Repository

    Fiscaletti, D.

    2016-02-15

    © 2016 Cambridge University Press. The interaction between the large and the small scales of turbulence is investigated in a mixing layer, at a Reynolds number based on the Taylor microscale of , via direct numerical simulations. The analysis is performed in physical space, and the local vorticity root-mean-square (r.m.s.) is taken as a measure of the small-scale activity. It is found that positive large-scale velocity fluctuations correspond to large vorticity r.m.s. on the low-speed side of the mixing layer, whereas, they correspond to low vorticity r.m.s. on the high-speed side. The relationship between large and small scales thus depends on position if the vorticity r.m.s. is correlated with the large-scale velocity fluctuations. On the contrary, the correlation coefficient is nearly constant throughout the mixing layer and close to unity if the vorticity r.m.s. is correlated with the large-scale velocity gradients. Therefore, the small-scale activity appears closely related to large-scale gradients, while the correlation between the small-scale activity and the large-scale velocity fluctuations is shown to reflect a property of the large scales. Furthermore, the vorticity from unfiltered (small scales) and from low pass filtered (large scales) velocity fields tend to be aligned when examined within vortical tubes. These results provide evidence for the so-called \\'scale invariance\\' (Meneveau & Katz, Annu. Rev. Fluid Mech., vol. 32, 2000, pp. 1-32), and suggest that some of the large-scale characteristics are not lost at the small scales, at least at the Reynolds number achieved in the present simulation.

  10. Scaling of turbulence and turbulent mixing using Terascale numerical simulations

    Science.gov (United States)

    Donzis, Diego A.

    Fundamental aspects of turbulence and turbulent mixing are investigated using direct numerical simulations (DNS) of stationary isotropic turbulence, with Taylor-scale Reynolds numbers (Rlambda) ranging from 8 to 650 and Schmidt numbers (Sc) from 1/8 to 1024. The primary emphasis is on important scaling issues that arise in the study of intermittency, mixing and turbulence under solid-body rotation. Simulations up to 20483 in size have been performed using large resource allocations on Terascale computers at leading supercomputing centers. Substantial efforts in algorithmic development have also been undertaken and resulted in a new code based on a two-dimensional domain decomposition which allows the use of very large number of processors. Benchmark tests indicate very good parallel performance for resolutions up to 40963 on up to 32768 processors, which is highly promising for future simulations at higher resolutions and processor counts eventually to approach Petascale levels. Investigation of intermittency through the statistics of dissipation and enstrophy in a series of simulations at the same Reynolds number but different resolution indicate that accurate results in high-order moments require a higher degree of fine-scale resolution than commonly practiced. However, statistics up to fourth order are satisfactory if the grid spacing is not larger than Komogorov scale, without the requirement of a clear analytic range for corresponding structure functions as suggested by recent theories. Results from highly resolved simulations provide support for a modified resolution criterion derived in this work for structure functions of different orders and as a function of Rlambda. At the highest Reynolds number in our simulations (400 and 650) dissipation and enstrophy exhibit extreme fluctuations of O(1000) the mean which have not been studied in the literature before. The far tails of the probability density functions of dissipation and enstrophy appear to coincide

  11. Quality of mixing in a stired bioreactor used for animal cells culture: heterogeneities in a lab scale bioreactor and evolution of mixing time with scale up

    National Research Council Canada - National Science Library

    Collignon, ML; Dossin, D; Delafosse, A; Crine, M; Toye, D

    2010-01-01

    .... The mixing time is measured by conductimetry inside 20 l, 80 l, 600 l tanks. The Grenville correlation is adjusted on these experimental measurements to improve the prediction of the mixing time during the scale-up of the...

  12. PROPERTIES IMPORTANT TO MIXING FOR WTP LARGE SCALE INTEGRATED TESTING

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D.; Martino, C.; Poirier, M.

    2012-04-26

    Large Scale Integrated Testing (LSIT) is being planned by Bechtel National, Inc. to address uncertainties in the full scale mixing performance of the Hanford Waste Treatment and Immobilization Plant (WTP). Testing will use simulated waste rather than actual Hanford waste. Therefore, the use of suitable simulants is critical to achieving the goals of the test program. External review boards have raised questions regarding the overall representativeness of simulants used in previous mixing tests. Accordingly, WTP requested the Savannah River National Laboratory (SRNL) to assist with development of simulants for use in LSIT. Among the first tasks assigned to SRNL was to develop a list of waste properties that matter to pulse-jet mixer (PJM) mixing of WTP tanks. This report satisfies Commitment 5.2.3.1 of the Department of Energy Implementation Plan for Defense Nuclear Facilities Safety Board Recommendation 2010-2: physical properties important to mixing and scaling. In support of waste simulant development, the following two objectives are the focus of this report: (1) Assess physical and chemical properties important to the testing and development of mixing scaling relationships; (2) Identify the governing properties and associated ranges for LSIT to achieve the Newtonian and non-Newtonian test objectives. This includes the properties to support testing of sampling and heel management systems. The test objectives for LSIT relate to transfer and pump out of solid particles, prototypic integrated operations, sparger operation, PJM controllability, vessel level/density measurement accuracy, sampling, heel management, PJM restart, design and safety margin, Computational Fluid Dynamics (CFD) Verification and Validation (V and V) and comparison, performance testing and scaling, and high temperature operation. The slurry properties that are most important to Performance Testing and Scaling depend on the test objective and rheological classification of the slurry (i

  13. Quantifying Mixing and Scales of Heterogeneity in 2-D Numerical Models of Chaotic Mantle Mixing

    Science.gov (United States)

    Harris, A. C.; Naliboff, J.; Prytulak, J.; Vanacore, E.; Cooper, K. M.; Hart, S.; Kellogg, L. H.

    2006-12-01

    Fundamental to our understanding of geochemical reservoirs within the Earth's mantle is the concept of the scale and distribution of heterogeneity. Although many studies approach this concept qualitatively few have attempted a quantitative assessment. Through a collaborative effort at the CIDER (Cooperative Institute for Deep Earth Research) 2006 summer workshop, we applied a 2-D/1-D power spectral and statistical analysis, respectively, to the temperature field and passive tracer distribution within a 2-D numerical model of mantle convection. The resultant data provides a means to objectively describe the scales of mixing and heterogeneity within various model scenarios. The dynamic models used had a 1x10 aspect ratio, included temperature- and pressure-dependent viscosity, had a Rayleigh number of 10^7, and had both internal and basal heating. One end member case includes a layered structure for viscosity and thermal conductivity, with a sharp increase in the mid-mantle. Spectral analysis of the temperature fields indicates that power near the upper and lower boundary layers is concentrated in long-wavelength structures while in the mid-mantle the spectrum is broader. Layering the viscosity structure enhances this dichotomy, but does not isolate the upper from the lower mantle and does not necessarily lead to decreased mixing rates or efficiency. Preliminary results demonstrate that the overall particle distribution, measured as a function of the distance between particles, is not necessarily unimodal. Furthermore, at a given time step this distribution may become multimodal.

  14. Efficient non-hydrostatic modelling of 3D wave-induced currents using a subgrid approach

    Science.gov (United States)

    Rijnsdorp, Dirk P.; Smit, Pieter B.; Zijlema, Marcel; Reniers, Ad J. H. M.

    2017-08-01

    Wave-induced currents are an ubiquitous feature in coastal waters that can spread material over the surf zone and the inner shelf. These currents are typically under resolved in non-hydrostatic wave-flow models due to computational constraints. Specifically, the low vertical resolutions adequate to describe the wave dynamics - and required to feasibly compute at the scales of a field site - are too coarse to account for the relevant details of the three-dimensional (3D) flow field. To describe the relevant dynamics of both wave and currents, while retaining a model framework that can be applied at field scales, we propose a two grid approach to solve the governing equations. With this approach, the vertical accelerations and non-hydrostatic pressures are resolved on a relatively coarse vertical grid (which is sufficient to accurately resolve the wave dynamics), whereas the horizontal velocities and turbulent stresses are resolved on a much finer subgrid (of which the resolution is dictated by the vertical scale of the mean flows). This approach ensures that the discrete pressure Poisson equation - the solution of which dominates the computational effort - is evaluated on the coarse grid scale, thereby greatly improving efficiency, while providing a fine vertical resolution to resolve the vertical variation of the mean flow. This work presents the general methodology, and discusses the numerical implementation in the SWASH wave-flow model. Model predictions are compared with observations of three flume experiments to demonstrate that the subgrid approach captures both the nearshore evolution of the waves, and the wave-induced flows like the undertow profile and longshore current. The accuracy of the subgrid predictions is comparable to fully resolved 3D simulations - but at much reduced computational costs. The findings of this work thereby demonstrate that the subgrid approach has the potential to make 3D non-hydrostatic simulations feasible at the scale of a

  15. Monte Carlo-based subgrid parameterization of vertical velocity and stratiform cloud microphysics in ECHAM5.5-HAM2

    Directory of Open Access Journals (Sweden)

    J. Tonttila

    2013-08-01

    Full Text Available A new method for parameterizing the subgrid variations of vertical velocity and cloud droplet number concentration (CDNC is presented for general circulation models (GCMs. These parameterizations build on top of existing parameterizations that create stochastic subgrid cloud columns inside the GCM grid cells, which can be employed by the Monte Carlo independent column approximation approach for radiative transfer. The new model version adds a description for vertical velocity in individual subgrid columns, which can be used to compute cloud activation and the subgrid distribution of the number of cloud droplets explicitly. Autoconversion is also treated explicitly in the subcolumn space. This provides a consistent way of simulating the cloud radiative effects with two-moment cloud microphysical properties defined at subgrid scale. The primary impact of the new parameterizations is to decrease the CDNC over polluted continents, while over the oceans the impact is smaller. Moreover, the lower CDNC induces a stronger autoconversion of cloud water to rain. The strongest reduction in CDNC and cloud water content over the continental areas promotes weaker shortwave cloud radiative effects (SW CREs even after retuning the model. However, compared to the reference simulation, a slightly stronger SW CRE is seen e.g. over mid-latitude oceans, where CDNC remains similar to the reference simulation, and the in-cloud liquid water content is slightly increased after retuning the model.

  16. Scaling Relationships Based on Scaled Tank Mixing and Transfer Test Results

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F.; Holmes, Aimee E.; Heredia-Langner, Alejandro

    2013-09-18

    This report documents the statistical analyses performed (by Pacific Northwest National Laboratory for Washington River Protection Solutions) on data from 26 tests conducted using two scaled tanks (43 and 120 inches) in the Small Scale Mixing Demonstration platform. The 26 tests varied several test parameters, including mixer-jet nozzle velocity, base simulant, supernatant viscosity, and capture velocity. For each test, samples were taken pre-transfer and during five batch transfers. The samples were analyzed for the concentrations (lbs/gal slurry) of four primary components in the base simulants (gibbsite, stainless steel, sand, and ZrO2). The statistical analyses including modeling the component concentrations as functions of test parameters using stepwise regression with two different model forms. The resulting models were used in an equivalent performance approach to calculate values of scaling exponents (for a simple geometric scaling relationship) as functions of the parameters in the component concentration models. The resulting models and scaling exponents are displayed in tables and graphically. The sensitivities of component concentrations and scaling exponents to the test parameters are presented graphically. These results will serve as inputs to subsequent work by other researchers to develop scaling relationships that are applicable to full-scale tanks.

  17. Scaling Relationships Based on Scaled Tank Mixing and Transfer Test Results

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Holmes, Aimee E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Heredia-Langner, Alejandro [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Kearn P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kelly, Steven E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-01-01

    This report documents the statistical analyses performed (by Pacific Northwest National Laboratory for Washington River Protection Solutions) on data from 26 tests conducted using two scaled tanks (43 and 120 inches) in the Small Scale Mixing Demonstration platform. The 26 tests varied several test parameters, including mixer-jet nozzle velocity, base simulant, supernatant viscosity, and capture velocity. For each test, samples were taken pre-transfer and during five batch transfers. The samples were analyzed for the concentrations (lbs/gal slurry) of four primary components in the base simulants (gibbsite, stainless steel, sand, and ZrO2). The statistical analyses including modeling the component concentrations as functions of test parameters using stepwise regression with two different model forms. The resulting models were used in an equivalent performance approach to calculate values of scaling exponents (for a simple geometric scaling relationship) as functions of the parameters in the component concentration models. The resulting models and scaling exponents are displayed in tables and graphically. The sensitivities of component concentrations and scaling exponents to the test parameters are presented graphically. These results will serve as inputs to subsequent work by other researchers to develop scaling relationships that are applicable to full-scale tanks.

  18. Unsteady Flame Embedding (UFE) Subgrid Model for Turbulent Premixed Combustion Simulations

    KAUST Repository

    El-Asrag, Hossam

    2010-01-04

    We present a formulation for an unsteady subgrid model for premixed combustion in the flamelet regime. Since chemistry occurs at the unresolvable scales, it is necessary to introduce a subgrid model that accounts for the multi-scale nature of the problem using the information available on the resolved scales. Most of the current models are based on the laminar flamelet concept, and often neglect the unsteady effects. The proposed model\\'s primary objective is to encompass many of the flame/turbulence interactions unsteady features and history effects. In addition it provides a dynamic and accurate approach for computing the subgrid flame propagation velocity. The unsteady flame embedding approach (UFE) treats the flame as an ensemble of locally one-dimensional flames. A set of elemental one dimensional flames is used to describe the turbulent flame structure at the subgrid level. The stretched flame calculations are performed on the stagnation line of a strained flame using the unsteady filtered strain rate computed from the resolved- grid. The flame iso-surface is tracked using an accurate high-order level set formulation to propagate the flame interface at the coarse resolution with minimum numerical diffusion. In this paper the solver and the model components are introduced and used to investigate two unsteady flames with different Lewis numbers in the thin reaction zone regime. The results show that the UFE model captures the unsteady flame-turbulence interactions and the flame propagation speed reasonably well. Higher propagation speed is observed for the lower than unity Lewis number flame because of the impact of differential diffusion.

  19. Slip, Swim, Mix, Pack: Fluid Mechanics at the Micron Scale

    Science.gov (United States)

    Lauga, Eric

    2006-11-01

    This talk summarizes my thesis work which was advised by Michael P. Brenner and Howard A. Stone at Harvard University and is devoted to fluid behavior at the micrometer length scale. We consider four different problems. We first address the topic of the no-slip boundary condition in Newtonian liquids. After briefly reviewing the field, we (1) present models for apparent slip in three distinct experimental settings, (2) propose a new method to probe slip and (3) show that slip has virtually no influence on the non-modal stability of shear flows. The second problem we consider addresses mixing in micro-devices. We show that microchannels which are obtained with a single step of microfabrication (that is, have constant height) are able to generate fully three-dimensional flows. The third problem we present proposes a mechanical model for the motion of the bacterium E. coli near solid boundaries. It has been observed that, near a solid surface, E. coli does not swim in a straight line but in clockwise circles, which we show is a consequence of the hydrodynamic interactions between the free- swimming bacterium and the surface. The final problem we consider addresses self-assembly of micro- particles. We show that when spherical particles located on a liquid droplet are forced to come together by evaporation of the droplet, the geometrical and mechanical constraints arising during the process lead to unique final clusters.

  20. Discontinuous Galerkin Subgrid Finite Element Method for Heterogeneous Brinkman’s Equations

    KAUST Repository

    Iliev, Oleg P.

    2010-01-01

    We present a two-scale finite element method for solving Brinkman\\'s equations with piece-wise constant coefficients. This system of equations model fluid flows in highly porous, heterogeneous media with complex topology of the heterogeneities. We make use of the recently proposed discontinuous Galerkin FEM for Stokes equations by Wang and Ye in [12] and the concept of subgrid approximation developed for Darcy\\'s equations by Arbogast in [4]. In order to reduce the error along the coarse-grid interfaces we have added a alternating Schwarz iteration using patches around the coarse-grid boundaries. We have implemented the subgrid method using Deal.II FEM library, [7], and we present the computational results for a number of model problems. © 2010 Springer-Verlag Berlin Heidelberg.

  1. A new downscaling method for sub-grid turbulence modeling

    Directory of Open Access Journals (Sweden)

    L. Rottner

    2017-06-01

    Full Text Available In this study we explore a new way to model sub-grid turbulence using particle systems. The ability of particle systems to model small-scale turbulence is evaluated using high-resolution numerical simulations. These high-resolution data are averaged to produce a coarse-grid velocity field, which is then used to drive a complete particle-system-based downscaling. Wind fluctuations and turbulent kinetic energy are compared between the particle simulations and the high-resolution simulation. Despite the simplicity of the physical model used to drive the particles, the results show that the particle system is able to represent the average field. It is shown that this system is able to reproduce much finer turbulent structures than the numerical high-resolution simulations. In addition, this study provides an estimate of the effective spatial and temporal resolution of the numerical models. This highlights the need for higher-resolution simulations in order to evaluate the very fine turbulent structures predicted by the particle systems. Finally, a study of the influence of the forcing scale on the particle system is presented.

  2. Parallel up-scaling of Capacitive Mixing (CapMix) system enhances the specific performance

    NARCIS (Netherlands)

    Liu, Fei; Donkers, Tim F.W.; Wagterveld, R.M.; Schaetzle, Olivier; Saakes, Michel; Buisman, Cees J.N.; Hamelers, Hubertus V.M.

    2016-01-01

    Given the considerable amount of energy dissipated in the salinity gradient at the point where a river flows into the sea, we investigate the technology of capacitive mixing (CapMix), an attractive technology for generating electrical power from this gradient. We determine the performances of

  3. A Fast and Accurate Scheme for Sea Ice Dynamics with a Stochastic Subgrid Model

    Science.gov (United States)

    Seinen, C.; Khouider, B.

    2016-12-01

    Sea ice physics is a very complex process occurring over a wide range of scales; such as local melting or large scale drift. At the current grid resolution of Global Climate Models (GCMs), we are able to resolve large scale sea ice dynamics but uncertainty remains due to subgrid physics and potential dynamic feedback, especially due to the formation of melt ponds. Recent work in atmospheric science has shown success of Markov Jump stochastic subgrid models in the representation of clouds and convection and their feedback into the large scales. There has been a push to implement these methods in other parts of the Earth System and for the cryosphere in particular but in order to test these methods, efficient and accurate solvers are required for the resolved large scale sea-ice dynamics. We present a second order accurate scheme, in both time and space, for the sea ice momentum equation (SIME) with a Jacobian Free Newton Krylov (JFNK) solver. SIME is a highly nonlinear equation due to sea ice rheology terms appearing in the stress tensor. The most commonly accepted formulation, introduced by Hibler, allows sea-ice to resist significant stresses in compression but significantly less in tension. The relationship also leads to large changes in internal stresses from small changes in velocity fields. These non-linearities have resulted in the use of implicit methods for SIME and a JFNK solver was recently introduced and used to gain efficiency. However, the method used so far is only first order accurate in time. Here we expand the JFNK approach to a Crank-Nicholson discretization of SIME. This fully second order scheme is achieved with no increase in computational cost and will allow efficient testing and development of subgrid stochastic models of sea ice in the near future.

  4. Atomic Scale Mixing for Inertial Confinement Fusion Associated Hydro Instabilities

    Science.gov (United States)

    2013-01-26

    removed by consideration of the Prandtl number. Detonation waves allowmultiple solutions, as weak or strong detonations [30], while some dissipative...andmixture concentrations provide the main input to a thermonuclear (TN) burn computation [3]. The in- terest in mix is brought about by current...mechanism often selects the weak deto- nation. Equations suggested by three phase flow for petroleum reservoirs show nonuniqueness for wave interaction

  5. A scale invariance criterion for LES parametrizations

    Directory of Open Access Journals (Sweden)

    Urs Schaefer-Rolffs

    2015-01-01

    Full Text Available Turbulent kinetic energy cascades in fluid dynamical systems are usually characterized by scale invariance. However, representations of subgrid scales in large eddy simulations do not necessarily fulfill this constraint. So far, scale invariance has been considered in the context of isotropic, incompressible, and three-dimensional turbulence. In the present paper, the theory is extended to compressible flows that obey the hydrostatic approximation, as well as to corresponding subgrid-scale parametrizations. A criterion is presented to check if the symmetries of the governing equations are correctly translated into the equations used in numerical models. By applying scaling transformations to the model equations, relations between the scaling factors are obtained by demanding that the mathematical structure of the equations does not change.The criterion is validated by recovering the breakdown of scale invariance in the classical Smagorinsky model and confirming scale invariance for the Dynamic Smagorinsky Model. The criterion also shows that the compressible continuity equation is intrinsically scale-invariant. The criterion also proves that a scale-invariant turbulent kinetic energy equation or a scale-invariant equation of motion for a passive tracer is obtained only with a dynamic mixing length. For large-scale atmospheric flows governed by the hydrostatic balance the energy cascade is due to horizontal advection and the vertical length scale exhibits a scaling behaviour that is different from that derived for horizontal length scales.

  6. Scaling Theory for Pulsed Jet Mixed Vessels, Sparging, and Cyclic Feed Transport Systems for Slurries

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, William L.; Rector, David R.; Rassat, Scot D.; Enderlin, Carl W.; Minette, Michael J.; Bamberger, Judith A.; Josephson, Gary B.; Wells, Beric E.; Berglin, Eric J.

    2013-09-27

    This document is a previously unpublished work based on a draft report prepared by Pacific Northwest National Laboratory (PNNL) for the Hanford Waste Treatment and Immobilization Plant (WTP) in 2012. Work on the report stopped when WTP’s approach to testing changed. PNNL is issuing a modified version of the document a year later to preserve and disseminate the valuable technical work that was completed. This document establishes technical bases for evaluating the mixing performance of Waste Treatment Plant (WTP) pretreatment process tanks based on data from less-than-full-scale testing, relative to specified mixing requirements. The technical bases include the fluid mechanics affecting mixing for specified vessel configurations, operating parameters, and simulant properties. They address scaling vessel physical performance, simulant physical performance, and “scaling down” the operating conditions at full scale to define test conditions at reduced scale and “scaling up” the test results at reduced scale to predict the performance at full scale. Essentially, this document addresses the following questions: • Why and how can the mixing behaviors in a smaller vessel represent those in a larger vessel? • What information is needed to address the first question? • How should the information be used to predict mixing performance in WTP? The design of Large Scale Integrated Testing (LSIT) is being addressed in other, complementary documents.

  7. A distributed Grid-Xinanjiang model with integration of subgrid variability of soil storage capacity

    Directory of Open Access Journals (Sweden)

    Wei-jian Guo

    2016-04-01

    Full Text Available Realistic hydrological response is sensitive to the spatial variability of landscape properties. For a grid-based distributed rainfall-runoff model with a hypothesis of a uniform grid, the high-frequency information within a grid cell will be gradually lost as the resolution of the digital elevation model (DEM grows coarser. Therefore, the performance of a hydrological model is usually scale-dependent. This study used the Grid-Xinanjiang (GXAJ model as an example to investigate the effects of subgrid variability on hydrological response at different scales. With the aim of producing a more reasonable hydrological response and spatial description of the landscape properties, a new distributed rainfall-runoff model integrating the subgrid variability (the GXAJSV model was developed. In this model, the topographic index is used as an auxiliary variable correlated with the soil storage capacity. The incomplete beta distribution is suggested for simulating the probability distribution of the soil storage capacity within the raster grid. The Yaogu Basin in China was selected for model calibration and validation at different spatial scales. Results demonstrated that the proposed model can effectively eliminate the scale dependence of the GXAJ model and produce a more reasonable hydrological response.

  8. Quality of mixing in a stired bioreactor used for animal cells culture: heterogeneities in a lab scale bioreactor and evolution of mixing time with scale up

    Directory of Open Access Journals (Sweden)

    Collignon, ML.

    2010-01-01

    Full Text Available Animal cells are industrially cultivated inside stirred bioreactors to produce proteinic compounds. Due to the use of mild agitation conditions in order to limit mechanical constraints, the homogeneity of the culture medium can be far from perfect. This study has therefore two objectives: the global characterization of the mixing via the mixing time and the local description of concentration fields. The mixing time is measured by conductimetry inside 20 l, 80 l, 600 l tanks. The Grenville correlation is adjusted on these experimental measurements to improve the prediction of the mixing time during the scale-up of the process. The concentration fields are visualized by the Planar Laser Induced Fluorescence (P.L.I.F. technique in the 20 l tank. This part of the study is focused on the time evolution of the maximum value of the tracer concentration inside measurement planes and of the numerical distribution of theses concentration fields.

  9. Mixing Metaphors: Building Infrastructure for Large Scale School Turnaround

    Science.gov (United States)

    Peurach, Donald J.; Neumerski, Christine M.

    2015-01-01

    The purpose of this analysis is to increase understanding of the possibilities and challenges of building educational infrastructure--the basic, foundational structures, systems, and resources--to support large-scale school turnaround. Building educational infrastructure often exceeds the capacity of schools, districts, and state education…

  10. Effects of Standard Extremity on Mixed Standard Scale Performance Ratings.

    Science.gov (United States)

    1983-03-01

    standard rating scale: An) evaluation. Organizational B~ehavior and Human Performance, 1977, 18, 19-35. Thorndike , R. M. Correliationalprocedures for...Department of Psychiatry and Chapel Hill, NC 27514 " B(-havioral Science * Baltimore, MD 21205 [r. Edward E, Lawlr Un v’rsity of Southern Californi

  11. Combination of Lidar Elevations, Bathymetric Data, and Urban Infrastructure in a Sub-Grid Model for Predicting Inundation in New York City during Hurricane Sandy

    CERN Document Server

    Loftis, Jon Derek; Hamilton, Stuart E; Forrest, David R

    2014-01-01

    We present the geospatial methods in conjunction with results of a newly developed storm surge and sub-grid inundation model which was applied in New York City during Hurricane Sandy in 2012. Sub-grid modeling takes a novel approach for partial wetting and drying within grid cells, eschewing the conventional hydrodynamic modeling method by nesting a sub-grid containing high-resolution lidar topography and fine scale bathymetry within each computational grid cell. In doing so, the sub-grid modeling method is heavily dependent on building and street configuration provided by the DEM. The results of spatial comparisons between the sub-grid model and FEMA's maximum inundation extents in New York City yielded an unparalleled absolute mean distance difference of 38m and an average of 75% areal spatial match. An in-depth error analysis reveals that the modeled extent contour is well correlated with the FEMA extent contour in most areas, except in several distinct areas where differences in special features cause sig...

  12. Emergence of scaling and assortative mixing through altruism

    Science.gov (United States)

    Li, Ping; Zhang, Jie; Small, Michael

    2011-06-01

    Many social networks, apart from displaying scale-free characteristics observed in some instances, possess another remarkable feature that distinguishes them from those that appear in biological and technological context-assortativity. However, little or no attention has been payed to the mechanism of assortativity in modeling these networks. Inspired by individuals' altruistic behavior in sociology, we develop a model with a different growth mechanism called “altruistic attachment”, which can reproduce not only the power law degree distribution but degree correlations. We study in detail the statistical properties of our network model, which we also demonstrate striking differences with the BA model, and can portray real social networks more precisely.

  13. Structural colour: Colour mixing in wing scales of a butterfly

    Science.gov (United States)

    Vukusic, P.; Sambles, J. R.; Lawrence, C. R.

    2000-03-01

    Green coloration in the animal kingdom, as seen in birds' feathers and reptile integument, is often an additive mixture of structurally effected blue and pigmentary yellow. Here we investigate the origin of the bright green coloration of the wing scales of the Indonesian male Papilio palinurus butterfly, the microstructure of which generates an extraordinary combination of both yellow and blue iridescence. The dual colour arises from a modulation imposed on the multilayer, producing the blue component as a result of a previously undiscovered retro-reflection process.

  14. Pseudoscalar-photon mixing and the large scale alignment of QsO ...

    Indian Academy of Sciences (India)

    Pseudoscalar-photon mixing and the large scale alignment of QsO optical polarizations. PANKAJ JAIN, sUKANTA PANDA and s sARALA. Physics Department, Indian Institute of Technology, Kanpur 208 016, India. Abstract. We review the observation of large scale alignment of QSO optical polariza- tions. Alignment is seen ...

  15. Characterization of Mixed Wettability at Different Scales and its Impact on Oil Recovery Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Mukul M.; Hirasaki, George J.

    2002-01-28

    The objectives of this project was to: (1) quantify the pore scale mechanisms that determine the wettability state of a reservoir, (2) study the effect of crude oil, brine and mineral compositions in the establishment of mixed wet states, (3) clarify the effect of mixed - wettability on oil displacement efficiency in waterfloods, (4) develop a new tracer technique to measure wettability, fluid distributions, residual saturation's and relative permeabilities, and (5) develop methods for properly incorporating wettability in up-scaling from pore to core to reservoir scales.

  16. Acceleration of inertial particles in wall bounded flows: DNS and LES with stochastic modelling of the subgrid acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Zamansky, Remi; Vinkovic, Ivana; Gorokhovski, Mikhael, E-mail: ivana.vinkovic@univ-lyonl.fr [Laboratoire de Mecanique des Fluides et d' Acoustique CNRS UMR 5509 Ecole Centrale de Lyon, 36, av. Guy de Collongue, 69134 Ecully Cedex (France)

    2011-12-22

    Inertial particle acceleration statistics are analyzed using DNS for turbulent channel flow. Along with effects recognized in homogeneous isotropic turbulence, an additional effect is observed due to high and low speed vortical structures aligned with the channel wall. In response to those structures, particles with moderate inertia experience strong longitudinal acceleration variations. DNS is also used in order to assess LES-SSAM (Subgrid Stochastic Acceleration Model), in which an approximation to the instantaneous non-filtered velocity field is given by simulation of both, filtered and residual, accelerations. This approach allow to have access to the intermittency of the flow at subgrid scale. Advantages of LES-SSAM in predicting particle dynamics in the channel flow at a high Reynolds number are shown.

  17. Evaluation of mixing and mass transfer in a stirred pilot scale bioreactor utilizing CFD

    DEFF Research Database (Denmark)

    Bach, Christian; Yang, Jifeng; Larsson, Hilde Kristina

    2017-01-01

    and mass transfer performance of a high power agitated pilot scale bioreactor has been characterized using a novel combination of computational fluid dynamics (CFD) and experimental investigations. The effect of turbulence inside the vessel was predicted using a standard RANS k-ε model. Mixing time......Knowledge and prediction of mixing and mass transfer in agitated bioreactors is fundamental for process development and scale up. In particular key process parameters such as mixing time and volumetric mass transfer coefficient are essential for bioprocess development. In this work the mixing...... transfer coefficients were determined from six Trichoderma reesei fermentations at different well-defined process conditions. Similarly the mass transfer was predicted by Higbie’s penetration model from two-phase CFD simulations using a correlation of bubble size and power input, and the overall mass...

  18. CHARACTERIZATION OF MIXED WETTABILITY AT DIFFERENT SCALES AND ITS IMPACT ON OIL RECOVERY EFFICIENCY

    Energy Technology Data Exchange (ETDEWEB)

    Mukul M. Sharma; George J. Hirasaki

    2003-09-01

    The objectives of the this research project were to: (1) Quantify the pore scale mechanisms that determine the wettability state of a reservoir; (2) Study the effect of crude oil, brine and mineral compositions in the establishment of mixed wet states; (3) Clarify the effect of mixed-wettability on oil displacement efficiency in waterfloods; and (4) Develop a new tracer technique to measure wettability, fluid distributions, residual saturations and relative permeabilities.

  19. Controlled mixed fermentation at winery scale using Zygotorulaspora florentina and Saccharomyces cerevisiae.

    Science.gov (United States)

    Lencioni, Livio; Romani, Cristina; Gobbi, Mirko; Comitini, Francesca; Ciani, Maurizio; Domizio, Paola

    2016-10-03

    Over the last few years the use of multi-starter inocula has become an attractive biotechnological practice in the search for wine with high flavour complexity or distinctive characters. This has been possible through exploiting the particular oenological features of some non-Saccharomyces yeast strains, and the effects that derive from their specific interactions with Saccharomyces. In the present study, we evaluated the selected strain Zygotorulaspora florentina (formerly Zygosaccharomyces florentinus) in mixed culture fermentations with Saccharomyces cerevisiae, from the laboratory scale to the winery scale. The scale-up fermentation and substrate composition (i.e., white or red musts) influenced the analytical composition of the mixed fermentation. At the laboratory scale, mixed fermentation with Z. florentina exhibited an enhancement of polysaccharides and 2-phenylethanol content and a reduction of volatile acidity. At the winery scale, different fermentation characteristics of Z. florentina were observed. Using Sangiovese red grape juice, sequential fermentation trials showed a significantly higher concentration of glycerol and esters while the sensorial analysis of the resulting wines showed higher floral notes and lower perception of astringency. To our knowledge, this is the first time that this yeasts association has been evaluated at the winery scale indicating the potential use of this mixed culture in red grape varieties. Copyright © 2016. Published by Elsevier B.V.

  20. COMPUTATIONAL FLUID DYNAMICS MODELING OF SCALED HANFORD DOUBLE SHELL TANK MIXING - CFD MODELING SENSITIVITY STUDY RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    JACKSON VL

    2011-08-31

    The primary purpose of the tank mixing and sampling demonstration program is to mitigate the technical risks associated with the ability of the Hanford tank farm delivery and celtification systems to measure and deliver a uniformly mixed high-level waste (HLW) feed to the Waste Treatment and Immobilization Plant (WTP) Uniform feed to the WTP is a requirement of 24590-WTP-ICD-MG-01-019, ICD-19 - Interface Control Document for Waste Feed, although the exact definition of uniform is evolving in this context. Computational Fluid Dynamics (CFD) modeling has been used to assist in evaluating scaleup issues, study operational parameters, and predict mixing performance at full-scale.

  1. Autonomous Operation of Hybrid Microgrid With AC and DC Subgrids

    DEFF Research Database (Denmark)

    Chiang Loh, Poh; Li, Ding; Kang Chai, Yi

    2013-01-01

    This paper investigates on power-sharing issues of an autonomous hybrid microgrid. Unlike existing microgrids which are purely ac, the hybrid microgrid studied here comprises dc and ac subgrids interconnected by power electronic interfaces. The main challenge here is to manage power flows among all...... converters. Suitable control and normalization schemes are now developed for controlling them with the overall hybrid microgrid performance already verified in simulation and experiment....

  2. Modeling and Experimental Investigations of Mixing-Controlled Geochemical and Biological Reactions at the Pore Scale

    Science.gov (United States)

    Valocchi, A. J.; Werth, C. J.; Yoon, H.; Tang, Y.

    2012-12-01

    Several studies have demonstrated the important role played by mixing-controlled reactions in porous media. For example, transverse mixing of nutrients along the fringes of a contaminant plume is often the limiting step that controls overall degradation rate during natural or engineered in situ bioremediation. Similar mixing processes can promote precipitation/dissolution reactions during geological sequestration of carbon dioxide. Field and laboratory investigations have demonstrated that the length scale of transverse mixing zones can be very small, often on the order of centimeters or less. To study dispersion, mixing and reaction at this scale, we use pore-scale numerical simulation models and micro-fluidics laboratory experiments. An overview of our methods and findings, including comparisons between direct numerical simulations and laboratory experiments will be presented. The presentation will emphasize recent results including: (a) coupling of precipitation/dissolution with porosity reduction under different geochemical conditions, and (b) impact of pore structure on biodegradation and biofilm growth patterns. Our work has improved understanding of coupled flow, transport and reaction processes; however, there remain significant challenges in extending the results to larger field scales.

  3. MAGNETOHYDRODYNAMIC KINK WAVES IN NONUNIFORM SOLAR FLUX TUBES: PHASE MIXING AND ENERGY CASCADE TO SMALL SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Roberto; Terradas, Jaume, E-mail: roberto.soler@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain)

    2015-04-10

    Magnetohydrodynamic (MHD) kink waves are ubiquitously observed in the solar atmosphere. The propagation and damping of these waves may play relevant roles in the transport and dissipation of energy in the solar atmospheric medium. However, in the atmospheric plasma dissipation of transverse MHD wave energy by viscosity or resistivity needs very small spatial scales to be efficient. Here, we theoretically investigate the generation of small scales in nonuniform solar magnetic flux tubes due to phase mixing of MHD kink waves. We go beyond the usual approach based on the existence of a global quasi-mode that is damped in time due to resonant absorption. Instead, we use a modal expansion to express the MHD kink wave as a superposition of Alfvén continuum modes that are phase mixed as time evolves. The comparison of the two techniques evidences that the modal analysis is more physically transparent and describes both the damping of global kink motions and the building up of small scales due to phase mixing. In addition, we discuss that the processes of resonant absorption and phase mixing are closely linked. They represent two aspects of the same underlying physical mechanism: the energy cascade from large scales to small scales due to naturally occurring plasma and/or magnetic field inhomogeneities. This process may provide the necessary scenario for efficient dissipation of transverse MHD wave energy in the solar atmospheric plasma.

  4. Operational forecasting with the subgrid technique on the Elbe Estuary

    Science.gov (United States)

    Sehili, Aissa

    2017-04-01

    Modern remote sensing technologies can deliver very detailed land surface height data that should be considered for more accurate simulations. In that case, and even if some compromise is made with regard to grid resolution of an unstructured grid, simulations still will require large grids which can be computationally very demanding. The subgrid technique, first published by Casulli (2009), is based on the idea of making use of the available detailed subgrid bathymetric information while performing computations on relatively coarse grids permitting large time steps. Consequently, accuracy and efficiency are drastically enhanced if compared to the classical linear method, where the underlying bathymetry is solely discretized by the computational grid. The algorithm guarantees rigorous mass conservation and nonnegative water depths for any time step size. Computational grid-cells are permitted to be wet, partially wet or dry and no drying threshold is needed. The subgrid technique is used in an operational forecast model for water level, current velocity, salinity and temperature of the Elbe estuary in Germany. Comparison is performed with the comparatively highly resolved classical unstructured grid model UnTRIM. The daily meteorological forcing data are delivered by the German Weather Service (DWD) using the ICON-EU model. Open boundary data are delivered by the coastal model BSHcmod of the German Federal Maritime and Hydrographic Agency (BSH). Comparison of predicted water levels between classical and subgrid model shows a very good agreement. The speedup in computational performance due to the use of the subgrid technique is about a factor of 20. A typical daily forecast can be carried out within less than 10 minutes on standard PC-like hardware. The model is capable of permanently delivering highly resolved temporal and spatial information on water level, current velocity, salinity and temperature for the whole estuary. The model offers also the possibility to

  5. Taking individual scaling differences into account by analyzing profile data with the Mixed Assessor Model

    DEFF Research Database (Denmark)

    Brockhoff, Per Bruun; Schlich, Pascal; Skovgaard, Ib

    2015-01-01

    Scale range differences between individual assessors will often constitute a non-trivial part of the assessor-by-product interaction in sensory profile data (Brockhoff, 2003, 1998; Brockhoff and Skovgaard, 1994). We suggest a new mixed model ANOVA analysis approach, the Mixed Assessor Model (MAM......) that properly takes this into account by a simple inclusion of the product averages as a covariate in the modeling and allowing the covariate regression coefficients to depend on the assessor. This gives a more powerful analysis by removing the scaling difference from the error term and proper confidence limits...... are deduced that include scaling difference in the error term to the proper extent. A meta study of 8619 sensory attributes from 369 sensory profile data sets from SensoBase (www.sensobase.fr) is conducted. In 45.3% of all attributes scaling heterogeneity is present (P-value

  6. The practical influence of rapid mixing on coagulation in a full-scale water treatment plant.

    Science.gov (United States)

    Allerdings, Demitri; Förster, Gerrit; Vasyukova, Ekaterina; Uhl, Wolfgang

    2015-01-01

    This study focuses on the effect of rapid mixing on the coagulation efficiency in a full-scale drinking-water treatment plant and discusses the mechanisms involved in the floc-formation process. The results refer to three periods of operation of the waterworks when no mechanical mixing was provided in the tanks for coagulant dosing due to mechanical failure of the rapid mixers. Although a certain deterioration of the subsequent flocculation process was observed, as assessed using the data for suspended solids, turbidity, and chemical oxygen demand, the overall water treatment performance was not affected. This suggests an insignificant role for intense rapid mixing in sweep flocculation during full-scale water treatment and reveals the potential to reduce the required energy costs for mechanical mixers.

  7. Hot-spot mix in ignition-scale inertial confinement fusion targets.

    Science.gov (United States)

    Regan, S P; Epstein, R; Hammel, B A; Suter, L J; Scott, H A; Barrios, M A; Bradley, D K; Callahan, D A; Cerjan, C; Collins, G W; Dixit, S N; Döppner, T; Edwards, M J; Farley, D R; Fournier, K B; Glenn, S; Glenzer, S H; Golovkin, I E; Haan, S W; Hamza, A; Hicks, D G; Izumi, N; Jones, O S; Kilkenny, J D; Kline, J L; Kyrala, G A; Landen, O L; Ma, T; MacFarlane, J J; MacKinnon, A J; Mancini, R C; McCrory, R L; Meezan, N B; Meyerhofer, D D; Nikroo, A; Park, H-S; Ralph, J; Remington, B A; Sangster, T C; Smalyuk, V A; Springer, P T; Town, R P J

    2013-07-26

    Mixing of plastic ablator material, doped with Cu and Ge dopants, deep into the hot spot of ignition-scale inertial confinement fusion implosions by hydrodynamic instabilities is diagnosed with x-ray spectroscopy on the National Ignition Facility. The amount of hot-spot mix mass is determined from the absolute brightness of the emergent Cu and Ge K-shell emission. The Cu and Ge dopants placed at different radial locations in the plastic ablator show the ablation-front hydrodynamic instability is primarily responsible for hot-spot mix. Low neutron yields and hot-spot mix mass between 34(-13,+50)  ng and 4000(-2970,+17 160)  ng are observed.

  8. Statistics and scaling of turbulence in a spatially developing mixing layer at Reλ = 250

    KAUST Repository

    Attili, Antonio

    2012-03-21

    The turbulent flow originating from the interaction between two parallel streams with different velocities is studied by means of direct numerical simulation. Rather than the more common temporal evolving layer, a spatially evolving configuration, with perturbed laminar inlet conditions is considered. The streamwise evolution and the self-similar state of turbulence statistics are reported and compared to results available in the literature. The characteristics of the transitional region agree with those observed in other simulations and experiments of mixing layers originating from laminar inlets. The present results indicate that the transitional region depends strongly on the inlet flow. Conversely, the self-similar state of turbulent kinetic energy and dissipation agrees quantitatively with those in a temporal mixing layer developing from turbulent initial conditions [M. M. Rogers and R. D. Moser, “Direct simulation of a self-similar turbulent mixing layer,” Phys. Fluids6, 903 (1994)]. The statistical features of turbulence in the self-similar region have been analysed in terms of longitudinal velocity structure functions, and scaling exponents are estimated by applying the extended self-similarity concept. In the small scale range (60 < r/η < 250), the scaling exponents display the universal anomalous scaling observed in homogeneous isotropic turbulence. The hypothesis of isotropy recovery holds in the turbulent mixing layer despite the presence of strong shear and large-scale structures, independently of the means of turbulence generation. At larger scales (r/η > 400), the mean shear and large coherent structures result in a significant deviation from predictions based on homogeneous isotropic turbulence theory. In this second scaling range, the numerical values of the exponents agree quantitatively with those reported for a variety of other flows characterized by strong shear, such as boundary layers, as well as channel and wake flows.

  9. Structure function scaling in a Reλ = 250 turbulent mixing layer

    KAUST Repository

    Attili, Antonio

    2011-12-22

    A highly resolved Direct Numerical Simulation of a spatially developing turbulent mixing layer is presented. In the fully developed region, the flow achieves a turbulent Reynolds number Reλ = 250, high enough for a clear separation between large and dissipative scales, so for the presence of an inertial range. Structure functions have been calculated in the self-similar region using velocity time series and Taylor\\'s frozen turbulence hypothesis. The Extended Self-Similarity (ESS) concept has been employed to evaluate relative scaling exponents. A wide range of scales with scaling exponents and intermittency levels equal to homogeneous isotropic turbulence has been identified. Moreover an additional scaling range exists for larger scales; it is characterized by smaller exponents, similar to the values reported in the literature for flows with strong shear.

  10. Development of Scales for Measuring Specific Elements of the Services Marketing Mix

    Directory of Open Access Journals (Sweden)

    Edo Rajh

    2009-12-01

    Full Text Available The purpose of this research was to develop scales that might be used for measuring specific elements of services marketing mix, including service delivery process, physical environment, and employees. Psychometric characteristics of initial set of items were analyzed by assessment of reliability, convergent and discriminant validity, and dimensionality of initial set of items. Cronbach alpha coeficients, explorative and confrimative factor analysis were employed. Results indicated that developed measurement scales had satisfactory psychometric characteristics. Measurement scales had very good reliability, convergent and discriminant validity, and unidimensionality.

  11. The Desirable Scale", impact of scale on group mix and social quality in assisted living facilities.

    NARCIS (Netherlands)

    Dort Spierings

    2012-01-01

    In order to be able to age in place, Dutch elderly are being housed in Assisted Living Facilities (ALFs) for over 25 years. Here they can live independently and rely on care and services. The physical scale of ALFs ranges from 30 up to 300 residents. This paper presents the findings of a multiple

  12. STATISTICAL EVALUATION OF SMALL SCALE MIXING DEMONSTRATION SAMPLING AND BATCH TRANSFER PERFORMANCE - 12093

    Energy Technology Data Exchange (ETDEWEB)

    GREER DA; THIEN MG

    2012-01-12

    The ability to effectively mix, sample, certify, and deliver consistent batches of High Level Waste (HLW) feed from the Hanford Double Shell Tanks (DST) to the Waste Treatment and Immobilization Plant (WTP) presents a significant mission risk with potential to impact mission length and the quantity of HLW glass produced. DOE's Tank Operations Contractor, Washington River Protection Solutions (WRPS) has previously presented the results of mixing performance in two different sizes of small scale DSTs to support scale up estimates of full scale DST mixing performance. Currently, sufficient sampling of DSTs is one of the largest programmatic risks that could prevent timely delivery of high level waste to the WTP. WRPS has performed small scale mixing and sampling demonstrations to study the ability to sufficiently sample the tanks. The statistical evaluation of the demonstration results which lead to the conclusion that the two scales of small DST are behaving similarly and that full scale performance is predictable will be presented. This work is essential to reduce the risk of requiring a new dedicated feed sampling facility and will guide future optimization work to ensure the waste feed delivery mission will be accomplished successfully. This paper will focus on the analytical data collected from mixing, sampling, and batch transfer testing from the small scale mixing demonstration tanks and how those data are being interpreted to begin to understand the relationship between samples taken prior to transfer and samples from the subsequent batches transferred. An overview of the types of data collected and examples of typical raw data will be provided. The paper will then discuss the processing and manipulation of the data which is necessary to begin evaluating sampling and batch transfer performance. This discussion will also include the evaluation of the analytical measurement capability with regard to the simulant material used in the demonstration tests. The

  13. Validity of contents of a paediatric critical comfort scale using mixed methodology.

    Science.gov (United States)

    Bosch-Alcaraz, A; Jordan-Garcia, I; Alcolea-Monge, S; Fernández-Lorenzo, R; Carrasquer-Feixa, E; Ferrer-Orona, M; Falcó-Pegueroles, A

    Critical illness in paediatric patients includes acute conditions in a healthy child as well as exacerbations of chronic disease, and therefore these situations must be clinically managed in Critical Care Units. The role of the paediatric nurse is to ensure the comfort of these critically ill patients. To that end, instruments are required that correctly assess critical comfort. To describe the process for validating the content of a paediatric critical comfort scale using mixed-method research. Initially, a cross-cultural adaptation of the Comfort Behavior Scale from English to Spanish using the translation and back-translation method was made. After that, its content was evaluated using mixed method research. This second step was divided into a quantitative stage in which an ad hoc questionnaire was used in order to assess each scale's item relevance and wording and a qualitative stage with two meetings with health professionals, patients and a family member following the Delphi Method recommendations. All scale items obtained a content validity index >0.80, except physical movement in its relevance, which obtained 0.76. Global content scale validity was 0.87 (high). During the qualitative stage, items from each of the scale domains were reformulated or eliminated in order to make the scale more comprehensible and applicable. The use of a mixed-method research methodology during the scale content validity phase allows the design of a richer and more assessment-sensitive instrument. Copyright © 2017 Sociedad Española de Enfermería Intensiva y Unidades Coronarias (SEEIUC). Publicado por Elsevier España, S.L.U. All rights reserved.

  14. Scaling of Mixing Rate in Mantle Convection Models: Influence of Plate Tectonics, Melting and Crustal Production

    Science.gov (United States)

    Tackley, Paul

    2017-04-01

    It is generally thought that the early Earth's mantle was hotter than today, which using conventional convective scalings should have led to vigorous convection and mixing. Geochemical observations, however, suggest that mixing was not as rapid as would be expected, leading to the suggestion that early Earth had stagnant lid convection [Debaille et al., 2003]. Additionally, the mantle's thermal evolution is difficult to explain using conventional scalings because early heat loss would have been too rapid, which has led to the hypothesis that plate tectonics convection does not follow the conventional convective scalings [Korenaga, 2003]. One physical process that could be important in this context is partial melting leading to crustal production, which has been shown to have the major effects of buffering mantle temperature and carrying a significant fraction of the heat from hot mantle [Nakagawa & Tackley, 2012], making plate tectonics easier [Lourenco et al., 2016], and causing compositional differentiation of the mantle that can buffer core heat loss [Nakagawa & Tackley, 2010]. Here, the influence of this process on mantle mixing is examined, using secular thermo-chemical models that simulate Earth's evolution over 4.5 billion years. Mixing is quantified both in terms of how rapidly stretching occurs, and in terms of dispersion: how rapidly initially close heterogeneities are dispersed horizontally and vertically through the mantle. It is found that convection with plate tectonics, melting and crustal production does not follow the conventional Nu-Ra and velocity-Ra scalings derived from boundary-layer theory, and thus mixing in the early Earth is much less rapid than earlier thought. Reasons for this will be analysed in this presentation.

  15. Initial condition effects on large scale structure in numerical simulations of plane mixing layers

    Science.gov (United States)

    McMullan, W. A.; Garrett, S. J.

    2016-01-01

    In this paper, Large Eddy Simulations are performed on the spatially developing plane turbulent mixing layer. The simulated mixing layers originate from initially laminar conditions. The focus of this research is on the effect of the nature of the imposed fluctuations on the large-scale spanwise and streamwise structures in the flow. Two simulations are performed; one with low-level three-dimensional inflow fluctuations obtained from pseudo-random numbers, the other with physically correlated fluctuations of the same magnitude obtained from an inflow generation technique. Where white-noise fluctuations provide the inflow disturbances, no spatially stationary streamwise vortex structure is observed, and the large-scale spanwise turbulent vortical structures grow continuously and linearly. These structures are observed to have a three-dimensional internal geometry with branches and dislocations. Where physically correlated provide the inflow disturbances a "streaky" streamwise structure that is spatially stationary is observed, with the large-scale turbulent vortical structures growing with the square-root of time. These large-scale structures are quasi-two-dimensional, on top of which the secondary structure rides. The simulation results are discussed in the context of the varying interpretations of mixing layer growth that have been postulated. Recommendations are made concerning the data required from experiments in order to produce accurate numerical simulation recreations of real flows.

  16. Large-Scale Structure Effects on Particle Motion in a Spatialy Developing Mixing Layer

    Science.gov (United States)

    Nikitopoulos, Dimitris E.; Acharya, Sumanta; Ning, Hui

    1996-11-01

    We will present results from a simulation of particle motion in a spatially developing turbulent mixing layer forced by a single frequency. The simulation is based on a model which utilizes Eulerian formulation for the carrier phase flowfield and Lagrangian formulation for the dispersed particles. The carrier-phase mean flow is determined from the classical turbulent boundary layer equations and a traditional k-ɛ turbulence model modified to include interaction terms with the imposed large-scale structure. An integral energy method is used to determine the evolution of the large-scale structure which is modeled as a spatially growing wave. The effect of the carrier phase small-scale turbulent fluctuations is taken into account by using a classical stochastic model with a gaussian PDF. The effects of the particle time scale magnitude relative to the large-scale structure timescale (Stokes number) are discussed as well as the effects of the particle injection conditions. It is found that the Stokes number for which the cross-stream dispersion of the particles is maximized has a strong dependence on the particle injection conditions. The particle injection phase relative to the large-scale structure also has a profound influence on the motion of the particles and their distribution within the mixing layer.

  17. CFD modeling of two immiscible fluids mixing in a commercial scale static mixer

    Directory of Open Access Journals (Sweden)

    V. Abdolkarimi

    2014-12-01

    Full Text Available A Computational Fluid Dynamics model based on the Eulerian formulation for multiphase flow was developed to model the mixing hydrodynamics of two immiscible fluids in a commercial scale static mixer. The two immiscible liquids were condensate and caustic solutions and were considered as two phases that are interpenetrating each other. The aim of this study was to develop a comprehensive Computational Fluid Dynamics model for predicting the impact of hydrodynamic parameters such as length, diameter and the arrangement of the corrugated plates of a static mixer on the degree of mixing and the pressure drop of the mixture. The model has been evaluated by comparing predictions of the degree of mixing and the mixture pressure drop with the same data available for the static mixer of the desulfurization plant of the Kharg petrochemical company. It has been shown that the predictions of the developed model are well adapted to the experimental data.

  18. Mixed

    Directory of Open Access Journals (Sweden)

    Pau Baya

    2011-05-01

    Full Text Available Remenat (Catalan (Mixed, "revoltillo" (Scrambled in Spanish, is a dish which, in Catalunya, consists of a beaten egg cooked with vegetables or other ingredients, normally prawns or asparagus. It is delicious. Scrambled refers to the action of mixing the beaten egg with other ingredients in a pan, normally using a wooden spoon Thought is frequently an amalgam of past ideas put through a spinner and rhythmically shaken around like a cocktail until a uniform and dense paste is made. This malleable product, rather like a cake mixture can be deformed pulling it out, rolling it around, adapting its shape to the commands of one’s hands or the tool which is being used on it. In the piece Mixed, the contortion of the wood seeks to reproduce the plasticity of this slow heavy movement. Each piece lays itself on the next piece consecutively like a tongue of incandescent lava slowly advancing but with unstoppable inertia.

  19. Two stage hydrolysis of corn stover at high solids content for mixing power saving and scale-up applications.

    Science.gov (United States)

    Liu, Ke; Zhang, Jian; Bao, Jie

    2015-11-01

    A two stage hydrolysis of corn stover was designed to solve the difficulties between sufficient mixing at high solids content and high power input encountered in large scale bioreactors. The process starts with the quick liquefaction to convert solid cellulose to liquid slurry with strong mixing in small reactors, then followed the comprehensive hydrolysis to complete saccharification into fermentable sugars in large reactors without agitation apparatus. 60% of the mixing energy consumption was saved by removing the mixing apparatus in large scale vessels. Scale-up ratio was small for the first step hydrolysis reactors because of the reduced reactor volume. For large saccharification reactors in the second step, the scale-up was easy because of no mixing mechanism was involved. This two stage hydrolysis is applicable for either simple hydrolysis or combined fermentation processes. The method provided a practical process option for industrial scale biorefinery processing of lignocellulose biomass. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Weakening Gravity on Redshift-Survey Scales with Kinetic Matter Mixing

    CERN Document Server

    D'Amico, Guido; Mancarella, Michele; Vernizzi, Filippo

    2017-01-01

    We explore general scalar-tensor models in the presence of a kinetic mixing between matter and the scalar field, which we call Kinetic Matter Mixing. In the frame where gravity is de-mixed from the scalar this is due to disformal couplings of matter species to the gravitational sector, with disformal coefficients that depend on the gradient of the scalar field. In the frame where matter is minimally coupled, it originates from the so-called beyond Horndeski quadratic Lagrangian. We extend the Effective Theory of Interacting Dark Energy by allowing disformal coupling coefficients to depend on the gradient of the scalar field as well. In this very general approach, we derive the conditions to avoid ghost and gradient instabilities and we define Kinetic Matter Mixing independently of the frame metric used to described the action. We study its phenomenological consequences for a $\\Lambda$CDM background evolution, first analytically on small scales. Then, we compute the matter power spectrum and the angular spectr...

  1. Comparison of Waste Feed Delivery Small Scale Mixing Demonstration Simulant to Hanford Waste

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Beric E.; Gauglitz, Phillip A.; Rector, David R.

    2011-08-15

    'The Hanford double-shell tank (DST) system provides the staging location for waste feed delivery to the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Hall (2008) includes WTP acceptance criteria that describe physical and chemical characteristics of the waste that must be certified as acceptable before the waste is transferred from the DSTs to the WTP. One of the more challenging requirements relates to the sampling and characterization of the undissolved solids (UDS) in a waste feed DST. The objectives of Washington River Protection Solutions' (WRPS) Small Scale Mixing Demonstration (SSMD) project are to understand and demonstrate the DST sampling and batch transfer performance at multiple scales using slurry simulants comprised of UDS particles and liquid (Townson 2009). The SSMD project utilizes geometrically scaled DST feed tanks to generate mixing, sampling, and transfer test data. In Phase 2 of the testing, RPP-49740, the 5-part simulant defined in RPP-48358 was used as the waste slurry simulant. The Phase 2 test data are being used to estimate the expected performance of the prototypic systems in the full-scale DSTs. As such, understanding of the how the small-scale systems as well as the simulant relate to the full-scale DSTs and actual waste is required. The focus of this report is comparison of the size and density of the 5-part SSMD simulant to that of the Hanford waste. This is accomplished by computing metrics for particle mobilization, suspension, settling, transfer line intake, and pipeline transfer from the characterization of the 5-part SSMD simulant and characterizations of the Hanford waste. In addition, the effects of the suspending fluid characteristics on the test results are considered, and a computational fluid dynamics tool useful to quantify uncertainties from simulant selections is discussed.'

  2. Enhanced reaction kinetics and reactive mixing scale dynamics in mixing fronts under shear flow for arbitrary Damköhler numbers

    Science.gov (United States)

    Bandopadhyay, Aditya; Le Borgne, Tanguy; Méheust, Yves; Dentz, Marco

    2017-02-01

    Mixing fronts, where fluids of different chemical compositions mix with each other, are known to represent hotspots of chemical reaction in hydrological systems. These fronts are typically subjected to velocity gradients, ranging from the pore scale due to no slip boundary conditions at fluid solid interfaces, to the catchment scale due to permeability variations and complex geometry of the Darcy velocity streamlines. A common trait of these processes is that the mixing interface is strained by shear. Depending on the Péclet number Pe , which represents the ratio of the characteristic diffusion time to the characteristic shear time, and the Damköhler number Da , which represents the ratio of the characteristic diffusion time to the characteristic reaction time, the local reaction rates can be strongly impacted by the dynamics of the mixing interface. So far, this impact has been characterized mostly either in kinetics-limited or in mixing-limited conditions, that is, for either low or high Da. Here the coupling of shear flow and chemical reactivity is investigated for arbitrary Damköhler numbers, for a bimolecular reaction and an initial interface with separated reactants. Approximate analytical expressions for the global production rate and reactive mixing scale are derived based on a reactive lamella approach that allows for a general coupling between stretching enhanced mixing and chemical reactions. While for Pe Da , we uncover a "strong stretching" scenario where new scaling laws emerge from the interplay between reaction kinetics, diffusion, and stretching. The analytical results are validated against numerical simulations. These findings shed light on the effect of flow heterogeneity on the enhancement of chemical reaction and the creation of spatially localized hotspots of reactivity for a broad range of systems ranging from kinetic limited to mixing limited situations.

  3. An Interdisciplinary Approach to Developing Renewable Energy Mixes at the Community Scale

    Science.gov (United States)

    Gormally, Alexandra M.; Whyatt, James D.; Timmis, Roger J.; Pooley, Colin G.

    2013-04-01

    Renewable energy has risen on the global political agenda due to concerns over climate change and energy security. The European Union (EU) currently has a target of 20% renewable energy by the year 2020 and there is increasing focus on the ways in which these targets can be achieved. Here we focus on the UK context which could be considered to be lagging behind other EU countries in terms of targets and implementation. The UK has a lower overall target of 15% renewable energy by 2020 and in 2011 reached only 3.8 % (DUKES, 2012), one of the lowest progressions compared to other EU Member States (European Commission, 2012). The reticence of the UK to reach such targets could in part be due to their dependence on their current energy mix and a highly centralised electricity grid system, which does not lend itself easily to the adoption of renewable technologies. Additionally, increasing levels of demand and the need to raise energy awareness are key concerns in terms of achieving energy security in the UK. There is also growing concern from the public about increasing fuel and energy bills. One possible solution to some of these problems could be through the adoption of small-scale distributed renewable schemes implemented at the community-scale with local ownership or involvement, for example, through energy co-operatives. The notion of the energy co-operative is well understood elsewhere in Europe but unfamiliar to many UK residents due to its centralised approach to energy provision. There are many benefits associated with engaging in distributed renewable energy systems. In addition to financial benefits, participation may raise energy awareness and can lead to positive responses towards renewable technologies. Here we briefly explore how a mix of small-scale renewables, including wind, hydro-power and solar PV, have been implemented and managed by a small island community in the Scottish Hebrides to achieve over 90% of their electricity needs from renewable

  4. Organics Characteristics of Sludge from a Full-Scale Anaerobic Digester Treating Domestic Mixed Sewage Sludge

    Directory of Open Access Journals (Sweden)

    Seswoya Roslinda

    2017-01-01

    Full Text Available Sewage sludge, normally in form of mixed sewage sludge is treated using anaerobic digester worldwide. In Malaysia, sewage sludge was categorized as domestic sewage sludge since sewage treatment plant treats only domestic sewage. The complex organic compounds in form of carbohydrates and proteins are transformed to methane during anaerobic digestion. The characteristics of complex organic compounds in domestic mixed sewage sludge are needed to assess the energy recovery form digesting domestic mixed sewage sludge. Besides that, it is common to use anaerobic biomass from existing anaerobic digester for the new setup of the anaerobic reactor. Therefore, this study was outlined to study the characteristics of domestic mixed sewage sludge and anaerobic biomass, particularly on the complex organic compounds. The complex organic compounds measured were carbohydrates and proteins. The higher complex organic solubilisation as a result of thermal pre-treatment was proven to improve the methane production. Therefore, in this study, the impact of low thermal pre-treatment in improving the organics solubilisation was assessed too. Low thermal pre-treatment at 70°C and 90°C at various treatment time were applied to the domestic mixed sewage sludge. The results indicated that the domestic sewage sludge and anaerobic biomass from a full-scale anaerobic digester contained complex organic compounds; existed mostly in form of particulate as shown by the low value of soluble to total ratio. Besides that, the low thermal treatment at 70°C and 90°C increased the organics solubilisation. Protein solubilisation was observed exceeded 8% after being treated for 20 min at both thermal treatments. However, the impact of low thermal treatment was better at 90°C, in which higher solubilisation was observed at longer treatment time.

  5. Mixing of Proton and Electron Scales - Effects of Proton Temperature Anisotropy on the Electron Firehose Instability

    Science.gov (United States)

    Maneva, Y. G.; Lazar, M.; Vinas, A. F.; Poedts, D. S.

    2015-12-01

    We perform kinetic linear theory instability analysis in a non-drifting anisotropic electron-proton plasma to study the effects of proton temperature anisotropies on the electron firehose instability in the collisionless solar wind. We solve the Vlasov linear theory dispersion relation for hot highly anisotropic electron-proton plasma in high-beta regime to study the behavior of the solar wind plasma close to the instability thresholds as observed by different spacecraft at 1 AU. We consider temperature and anisotropy regimes for which the electrons and the protons can interact via the excited electromagnetic fluctuations. For the selected parameters simultaneous electron and proton firehose instabilities can be observed with the growth rate of the electron firehose instability extending towards the proton scales. The co-existance of the proton and the electron firehose and the mixing of scales for the electromagnetic fluctuations excited by the two instabilities depends on the initial temperatures, anisotropies and angle of propagation. In the case of parallel wave propagation both left and right-hand polarized waves are simultaneously excited. As we increase the angle of propagation the electron firehose starts to dominate with excitation of large-amplitude aperiodic fluctuations over a large range of wave-numbers, starting at the protons scales and extending up to the smaller electron scales. We calculate the maximum growth rate of the oblique electron firehose as a function of the proton temperature anisotropy and discuss the implications of the electron-proton scale mixing for the observed plasma properties and instability thresholds in the undisturbed solar wind.

  6. Studies supporting the use of mechanical mixing in large scale beer fermentations.

    Science.gov (United States)

    Nienow, Alvin W; McLeod, Georgina; Hewitt, Christopher J

    2010-05-01

    Brewing fermentations have traditionally been undertaken without the use of mechanical agitation, with mixing being provided only by the fluid motion induced by the CO(2) evolved during the batch process. This approach has largely been maintained because of the belief in industry that rotating agitators would damage the yeast. Recent studies have questioned this view. At the bench scale, brewer's yeast is very robust and withstands intense mechanical agitation under aerobic conditions without observable damage as measured by flow cytometry and other parameters. Much less intense mechanical agitation also decreases batch fermentation time for anaerobic beer production by about 25% compared to mixing by CO(2) evolution alone with a small change in the concentration of the different flavour compounds. These changes probably arise for two reasons. Firstly, the agitation increases the relative velocity and the area of contact between the cells and the wort, thereby enhancing the rate of mass transfer to and from the cells. Secondly, the agitation eliminates spatial variations in both yeast concentration and temperature, thus ensuring that the cells are maintained close to the optimum temperature profile during the whole of the fermentation time. These bench scale studies have recently been supported by results at the commercial scale from mixing by an impeller or by a rotary jet head, giving more consistent production without changes in final flavour. It is suggested that this reluctance of the brewing industry to use (adequate) mechanical agitation is another example where the myth of shear damage has had a detrimental effect on the optimal operation of commercial bioprocessing.

  7. Scaling of Thermal Images at Different Spatial Resolution: The Mixed Pixel Problem

    Directory of Open Access Journals (Sweden)

    Hamlyn G. Jones

    2014-07-01

    Full Text Available The consequences of changes in spatial resolution for application of thermal imagery in plant phenotyping in the field are discussed. Where image pixels are significantly smaller than the objects of interest (e.g., leaves, accurate estimates of leaf temperature are possible, but when pixels reach the same scale or larger than the objects of interest, the observed temperatures become significantly biased by the background temperature as a result of the presence of mixed pixels. Approaches to the estimation of the true leaf temperature that apply both at the whole-pixel level and at the sub-pixel level are reviewed and discussed.

  8. Scheduling of power generation a large-scale mixed-variable model

    CERN Document Server

    Prékopa, András; Strazicky, Beáta; Deák, István; Hoffer, János; Németh, Ágoston; Potecz, Béla

    2014-01-01

    The book contains description of a real life application of modern mathematical optimization tools in an important problem solution for power networks. The objective is the modelling and calculation of optimal daily scheduling of power generation, by thermal power plants,  to satisfy all demands at minimum cost, in such a way that the  generation and transmission capacities as well as the demands at the nodes of the system appear in an integrated form. The physical parameters of the network are also taken into account. The obtained large-scale mixed variable problem is relaxed in a smart, practical way, to allow for fast numerical solution of the problem.

  9. Mixing large and small particles in a pilot scale rotary kiln

    DEFF Research Database (Denmark)

    Nielsen, Anders Rooma; Aniol, Rasmus Wochnik; Larsen, Morten Boberg

    2011-01-01

    The mixing of solid alternative fuel particles in cement raw materials was studied experimentally by visual observation in a pilot scale rotary kiln. Fuel particles were placed on top of the raw material bed prior to the experiment. The percentage of particles visible above the bed as a function...... of time was evaluated with the bed predominantly in the rolling bed mode. Experiments were conducted to investigate the effects of fuel particle size and shape, fuel particle density, rotary kiln fill degree and rotational speed. Large fuel particles and low-density fuel particles appeared more on top.......Results can be up-scaled to industrial conditions in cement rotary kilns and show that even relatively large fuel particles will predominantly be covered by raw material after less than 30s in the rotary kiln. This affects the heating and combustion mechanisms for the fuel particles....

  10. Constraining the Turbulence Scale and Mixing of a Crushed Pulsar Wind Nebula

    Science.gov (United States)

    Ng, Chi Yung; Ma, Y. K.; Bucciantini, Niccolo; Slane, Patrick O.; Gaensler, Bryan M.; Temim, Tea

    2016-04-01

    Pulsar wind nebulae (PWNe) are synchrotron-emitting nebulae resulting from the interaction between pulsars' relativistic particle outflows and the ambient medium. The Snail PWN in supernova remnant G327.1-1.1 is a rare system that has recently been crushed by supernova reverse shock. We carried out radio polarization observations with the Australia Telescope Compact Array and found highly ordered magnetic field structure in the nebula. This result is surprising, given the turbulent environment expected from hydrodynamical simulations. We developed a toymodel and compared simple simulations with observations to constrain the characteristic turbulence scale in the PWN and the mixing with supernova ejecta. We estimate that the turbulence scale is about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50-75%. The latter implies substantial mixing of the pulsar wind with the surrounding supernova ejecta.This work is supported by an ECS grant of the Hong Kong Government under HKU 709713P. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  11. Mixed convection around calandria tubes in a ¼ scale CANDU-6 moderator circulation tank

    Energy Technology Data Exchange (ETDEWEB)

    Atkins, M.D.; Rossouw, D.J.; Boer, M. [Nuclear Science Division, School of Mechanical and Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Kim, T., E-mail: tong.kim@wits.ac.za [Nuclear Science Division, School of Mechanical and Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Rhee, B.W.; Kim, H.T. [Severe Accident and PHWR Safety Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-05-15

    Highlights: • A secondary jet is formed at a stagnation region and is directed towards the center of the MCT. • The secondary jet undergoes the significant dissipation and mixing due to calandria tubes (CTs). • Its cooling effectiveness is reduced on the CTs in the bottom of the MCT. • With forced convection dominance, peak heat transfer is on the upper CT surface. • With natural convection dominance, peak heat transfer is on the lower CT surface. - Abstract: This study experimentally characterizes mixed convection around calandria tubes (CTs) in a ¼ scale CANDU-6 moderator circulation tank (MCT) that uses air as the working fluid. In a full scale CANDU-6 reactor that undergoes a postulated dual failure with a loss-of-coolant accident without the emergency core cooling system available, mixed convection heat transfer occurs around the CTs. The cooling effectiveness of the moderator is diminished as an emergency heat sink if overheating eventually leads to film boiling. To prevent the onset of film boiling, local sub-cooling margins of the moderator needs to be maintained or else the critical heat flux should be increased. Circulating the moderator which interacts with the overheated CTs increases the heat transfer into the moderator which may suppress film boiling. The present experimental results demonstrate that the cooling effectiveness of the circulating moderator, in particular the secondary jet, is attenuated substantially as it is convected away from the inner wall towards the center of the MCT. The momentum of the secondary jet is diffused through the CTs. At a low jet Reynolds number, the secondary jet becomes ineffective so that some overheated CTs positioned in the other half of the MCT are cooled only by natural convection.

  12. Leading for the long haul: a mixed-method evaluation of the Sustainment Leadership Scale (SLS).

    Science.gov (United States)

    Ehrhart, Mark G; Torres, Elisa M; Green, Amy E; Trott, Elise M; Willging, Cathleen E; Moullin, Joanna C; Aarons, Gregory A

    2018-01-19

    Despite our progress in understanding the organizational context for implementation and specifically the role of leadership in implementation, its role in sustainment has received little attention. This paper took a mixed-method approach to examine leadership during the sustainment phase of the Exploration, Preparation, Implementation, Sustainment (EPIS) framework. Utilizing the Implementation Leadership Scale as a foundation, we sought to develop a short, practical measure of sustainment leadership that can be used for both applied and research purposes. Data for this study were collected as a part of a larger mixed-method study of evidence-based intervention, SafeCare®, sustainment. Quantitative data were collected from 157 providers using web-based surveys. Confirmatory factor analysis was used to examine the factor structure of the Sustainment Leadership Scale (SLS). Qualitative data were collected from 95 providers who participated in one of 15 focus groups. A framework approach guided qualitative data analysis. Mixed-method integration was also utilized to examine convergence of quantitative and qualitative findings. Confirmatory factor analysis supported the a priori higher order factor structure of the SLS with subscales indicating a single higher order sustainment leadership factor. The SLS demonstrated excellent internal consistency reliability. Qualitative analyses offered support for the dimensions of sustainment leadership captured by the quantitative measure, in addition to uncovering a fifth possible factor, available leadership. This study found qualitative and quantitative support for the pragmatic SLS measure. The SLS can be used for assessing leadership of first-level leaders to understand how staff perceive leadership during sustainment and to suggest areas where leaders could direct more attention in order to increase the likelihood that EBIs are institutionalized into the normal functioning of the organization.

  13. Comparison of Waste Feed Delivery Small Scale Mixing Demonstration Simulant to Hanford Waste

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Beric E.; Gauglitz, Phillip A.; Rector, David R.

    2012-07-10

    The Hanford double-shell tank (DST) system provides the staging location for waste that will be transferred to the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Specific WTP acceptance criteria for waste feed delivery describe the physical and chemical characteristics of the waste that must be met before the waste is transferred from the DSTs to the WTP. One of the more challenging requirements relates to the sampling and characterization of the undissolved solids (UDS) in a waste feed DST because the waste contains solid particles that settle and their concentration and relative proportion can change during the transfer of the waste in individual batches. A key uncertainty in the waste feed delivery system is the potential variation in UDS transferred in individual batches in comparison to an initial sample used for evaluating the acceptance criteria. To address this uncertainty, a number of small-scale mixing tests have been conducted as part of Washington River Protection Solutions' Small Scale Mixing Demonstration (SSMD) project to determine the performance of the DST mixing and sampling systems. A series of these tests have used a five-part simulant composed of particles of different size and density and designed to be equal or more challenging than AY-102 waste. This five-part simulant, however, has not been compared with the broad range of Hanford waste, and thus there is an additional uncertainty that this simulant may not be as challenging as the most difficult Hanford waste. The purpose of this study is to quantify how the current five-part simulant compares to all of the Hanford sludge waste, and to suggest alternate simulants that could be tested to reduce the uncertainty in applying the current testing results to potentially more challenging wastes.

  14. Comparison of Waste Feed Delivery Small Scale Mixing Demonstration Simulant to Hanford Waste

    Energy Technology Data Exchange (ETDEWEB)

    Wells, Beric E.; Gauglitz, Phillip A.; Rector, David R.

    2011-09-01

    The Hanford double-shell tank (DST) system provides the staging location for waste that will be transferred to the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Specific WTP acceptance criteria for waste feed delivery describe the physical and chemical characteristics of the waste that must be met before the waste is transferred from the DSTs to the WTP. One of the more challenging requirements relates to the sampling and characterization of the undissolved solids (UDS) in a waste feed DST because the waste contains solid particles that settle and their concentration and relative proportion can change during the transfer of the waste in individual batches. A key uncertainty in the waste feed delivery system is the potential variation in UDS transferred in individual batches in comparison to an initial sample used for evaluating the acceptance criteria. To address this uncertainty, a number of small-scale mixing tests have been conducted as part of Washington River Protection Solutions' Small Scale Mixing Demonstration (SSMD) project to determine the performance of the DST mixing and sampling systems. A series of these tests have used a five-part simulant composed of particles of different size and density and designed to be equal or more challenging than AY-102 waste. This five-part simulant, however, has not been compared with the broad range of Hanford waste, and thus there is an additional uncertainty that this simulant may not be as challenging as the most difficult Hanford waste. The purpose of this study is to quantify how the current five-part simulant compares to all of the Hanford sludge waste, and to suggest alternate simulants that could be tested to reduce the uncertainty in applying the current testing results to potentially more challenging wastes.

  15. Sub-grid combustion modeling for compressible two-phase reacting flows

    Science.gov (United States)

    Sankaran, Vaidyanathan

    2003-06-01

    A generic formulation for modeling the turbulent combustion in compressible, high Reynolds number, two-phase; reacting flows has been developed and validated. A sub-grid mixing/combustion model called Linear Eddy Mixing (LEM) model has been extended to compressible flows and used inside the framework of Large Eddy Simulation (LES) in this LES-LEM approach. The LES-LEM approach is based on the proposition that the basic mechanistic distinction between the convective and the molecular effects should be preserved for accurate prediction of complex flow-fields such as those encountered in many combustion systems. Liquid droplets (represented by computational parcels) are tracked using the Lagrangian approach wherein the Newton's equation of motion for the discrete particles are integrated explicitly in the Eulerian gas field. The gas phase LES velocity fields are used to estimate the instantaneous gas velocity at the droplet location. Drag effects due to the droplets on the gas phase and the heat transfer between the gas and the liquid phase are explicitly included. Thus, full coupling is achieved between the two phases in the simulation. Validation of the compressible LES-LEM approach is conducted by simulating the flow-field in an operational General Electric Aircraft Engines combustor (LM6000). The results predicted using the proposed approach compares well with the experiments and a conventional (G-equation) thin-flame model. Particle tracking algorithms used in the present study are validated by simulating droplet laden temporal mixing layers. Quantitative and qualitative comparison with the results of spectral DNS exhibits good agreement. Simulations using the current LES-LEM for freely propagating partially premixed flame in a droplet-laden isotropic turbulent field correctly captures the flame structure in the partially premixed flames. Due to the strong spatial variation of equivalence ratio a broad flame similar to a premixed flame is realized. The current

  16. Methods for Quantifying the Uncertainties of LSIT Test Parameters, Test Results, and Full-Scale Mixing Performance Using Models Developed from Scaled Test Data

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cooley, Scott K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kuhn, William L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rector, David R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Heredia-Langner, Alejandro [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-05-01

    This report discusses the statistical methods for quantifying uncertainties in 1) test responses and other parameters in the Large Scale Integrated Testing (LSIT), and 2) estimates of coefficients and predictions of mixing performance from models that relate test responses to test parameters. Testing at a larger scale has been committed to by Bechtel National, Inc. and the U.S. Department of Energy (DOE) to “address uncertainties and increase confidence in the projected, full-scale mixing performance and operations” in the Waste Treatment and Immobilization Plant (WTP).

  17. Resolving terrestrial ecosystem processes along a subgrid topographic gradient for an earth-system model

    Science.gov (United States)

    Subin, Z M; Milly, Paul C.D.; Sulman, B N; Malyshev, Sergey; Shevliakova, E

    2014-01-01

    Soil moisture is a crucial control on surface water and energy fluxes, vegetation, and soil carbon cycling. Earth-system models (ESMs) generally represent an areal-average soil-moisture state in gridcells at scales of 50–200 km and as a result are not able to capture the nonlinear effects of topographically-controlled subgrid heterogeneity in soil moisture, in particular where wetlands are present. We addressed this deficiency by building a subgrid representation of hillslope-scale topographic gradients, TiHy (Tiled-hillslope Hydrology), into the Geophysical Fluid Dynamics Laboratory (GFDL) land model (LM3). LM3-TiHy models one or more representative hillslope geometries for each gridcell by discretizing them into land model tiles hydrologically coupled along an upland-to-lowland gradient. Each tile has its own surface fluxes, vegetation, and vertically-resolved state variables for soil physics and biogeochemistry. LM3-TiHy simulates a gradient in soil moisture and water-table depth between uplands and lowlands in each gridcell. Three hillslope hydrological regimes appear in non-permafrost regions in the model: wet and poorly-drained, wet and well-drained, and dry; with large, small, and zero wetland area predicted, respectively. Compared to the untiled LM3 in stand-alone experiments, LM3-TiHy simulates similar surface energy and water fluxes in the gridcell-mean. However, in marginally wet regions around the globe, LM3-TiHy simulates shallow groundwater in lowlands, leading to higher evapotranspiration, lower surface temperature, and higher leaf area compared to uplands in the same gridcells. Moreover, more than four-fold larger soil carbon concentrations are simulated globally in lowlands as compared with uplands. We compared water-table depths to those simulated by a recent global model-observational synthesis, and we compared wetland and inundated areas diagnosed from the model to observational datasets. The comparisons demonstrate that LM3-TiHy has the

  18. Computational Fluid Dynamics (CFD) Simulations of Jet Mixing in Tanks of Different Scales

    Science.gov (United States)

    Breisacher, Kevin; Moder, Jeffrey

    2010-01-01

    For long-duration in-space storage of cryogenic propellants, an axial jet mixer is one concept for controlling tank pressure and reducing thermal stratification. Extensive ground-test data from the 1960s to the present exist for tank diameters of 10 ft or less. The design of axial jet mixers for tanks on the order of 30 ft diameter, such as those planned for the Ares V Earth Departure Stage (EDS) LH2 tank, will require scaling of available experimental data from much smaller tanks, as well designing for microgravity effects. This study will assess the ability for Computational Fluid Dynamics (CFD) to handle a change of scale of this magnitude by performing simulations of existing ground-based axial jet mixing experiments at two tank sizes differing by a factor of ten. Simulations of several axial jet configurations for an Ares V scale EDS LH2 tank during low Earth orbit (LEO) coast are evaluated and selected results are also presented. Data from jet mixing experiments performed in the 1960s by General Dynamics with water at two tank sizes (1 and 10 ft diameter) are used to evaluate CFD accuracy. Jet nozzle diameters ranged from 0.032 to 0.25 in. for the 1 ft diameter tank experiments and from 0.625 to 0.875 in. for the 10 ft diameter tank experiments. Thermally stratified layers were created in both tanks prior to turning on the jet mixer. Jet mixer efficiency was determined by monitoring the temperatures on thermocouple rakes in the tanks to time when the stratified layer was mixed out. Dye was frequently injected into the stratified tank and its penetration recorded. There were no velocities or turbulence quantities available in the experimental data. A commercially available, time accurate, multi-dimensional CFD code with free surface tracking (FLOW-3D from Flow Science, Inc.) is used for the simulations presented. Comparisons are made between computed temperatures at various axial locations in the tank at different times and those observed experimentally. The

  19. Exact Scale Invariance in Mixing of Binary Candidates in Voting Model

    Science.gov (United States)

    Mori, Shintaro; Hisakado, Masato

    2010-03-01

    We introduce a voting model and discuss the scale invariance in the mixing of candidates. The Candidates are classified into two categories μ\\in \\{0,1\\} and are called as “binary” candidates. There are in total N=N0+N1 candidates, and voters vote for them one by one. The probability that a candidate gets a vote is proportional to the number of votes. The initial number of votes (“seed”) of a candidate μ is set to be sμ. After infinite counts of voting, the probability function of the share of votes of the candidate μ obeys gamma distributions with the shape exponent sμ in the thermodynamic limit Z0=N1s1+N0s0\\to ∞. Between the cumulative functions \\{xμ\\} of binary candidates, the power-law relation 1-x1 ˜ (1-x0)α with the critical exponent α=s1/s0 holds in the region 1-x0,1-x1≪ 1. In the double scaling limit (s1,s0)\\to (0,0) and Z0 \\to ∞ with s1/s0=α fixed, the relation 1-x1=(1-x0)α holds exactly over the entire range 0≤ x0,x1 ≤ 1. We study the data on horse races obtained from the Japan Racing Association for the period 1986 to 2006 and confirm scale invariance.

  20. Near-wall Behavior of a Scale Self-Recognition Mixed SGS Model

    Science.gov (United States)

    Kihara, Mizuki; Minamoto, Yuki; Naka, Yoshitsugu; Fukushima, Naoya; Shimura, Masayasu; Tanahashi, Mamoru

    2016-11-01

    A Scale Self-Recognition Mixed SGS Model was developed in terms of GS-SGS energy transfer in homogenius isotropic turbulence by Fukushima et al. (2015). In the present research, the near-wall characteristics of the Smagorinsky coefficient, CS are investigated in terms of GS-SGS energy transfer by analyzing DNS data of turbulent channel flows at Reτ = 400, 800 and 1270. CS is dependent on grid anisotropy, and this cause dependences of CS on Reτ . It is revealed that CS obtained directly from the DNS data is independent of Reτ and dependent on only dimensionless wall distance, y+ and filter-width to Kolmogorov scale ratio corrected by f, f . Δ / η , when the grid anisotropy is isolated from CS by using the correction function f proposed by Scotti et al. (1993). The contributions of Leonard, cross and Reynolds terms to total energy transfer are also independent of Reτ and dependent on only y+ and f . Δ / η in the near-wall region. These results suggest that CS can be determined dynamically from f . Δ / η in the wall turbulence if η is sufficiently predicted from the grid scale quantities.

  1. A Subgrid Parameterization for Wind Turbines in Weather Prediction Models with an Application to Wind Resource Limits

    Directory of Open Access Journals (Sweden)

    B. H. Fiedler

    2014-01-01

    Full Text Available A subgrid parameterization is offered for representing wind turbines in weather prediction models. The parameterization models the drag and mixing the turbines cause in the atmosphere, as well as the electrical power production the wind causes in the wind turbines. The documentation of the parameterization is complete; it does not require knowledge of proprietary data of wind turbine characteristics. The parameterization is applied to a study of wind resource limits in a hypothetical giant wind farm. The simulated production density was found not to exceed 1 W m−2, peaking at a deployed capacity density of 5 W m−2 and decreasing slightly as capacity density increased to 20 W m−2.

  2. Flow Kinematics and Lagrangian Mixing Dynamics in a Darcy Scale Heterogeneous Porous Medium

    Science.gov (United States)

    Dentz, M.; de Barros, F.; Le Borgne, T.

    2013-12-01

    We study the mixing behavior of a solute blob that is transported through a two-dimensional Darcy scale heterogeneous porous medium. Flow heterogeneity is induced by spatial variability in hydraulic conductivity. The fundamental mechanism governing the evolution of the solute blob are the competition of the stretching and compression action within a fluid element, and diffusion. We formulate the transport problem in a Lagrangian framework and consider the motion of solute particles that form the blob, in the coordinate system attached to the fluid element on which it originates. The blob evolution is fully characterized by the time series of stretching and shear rates of the material segment in its own coordinate system. Associated stirring protocols, or spreading protocols may be different from the ones encountered in chaotic and turbulent flow and can be related to the evolution of center of mass velocities of an ensemble of solute blobs. The permeability variability is modeled using a stochastic approach, which renders the stretching and shear rate time series as stochastic processes. Theses stochastic series are investigated numerically using random walk particle tracking simulations, and quantified analytically in terms of multiplicative and additive stochastic processes for the strip elongation and shear deformation. In this stochastic framework, we study the ensemble concentration PDF, concentration entropy and scalar dissipation rate. We relate the mixing properties to the appearance of coherent structures as quantified by the Okubo-Weiss measure and its Lagrangian counterpart.

  3. Properties important to mixing and simulant recommendations for WTP full-scale vessel testing

    Energy Technology Data Exchange (ETDEWEB)

    Poirier, M. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Martino, C. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-12-01

    Full Scale Vessel Testing (FSVT) is being planned by Bechtel National, Inc., to demonstrate the ability of the standard high solids vessel design (SHSVD) to meet mixing requirements over the range of fluid properties planned for processing in the Pretreatment Facility (PTF) of the Hanford Waste Treatment and Immobilization Plant (WTP). Testing will use simulated waste rather than actual Hanford waste. Therefore, the use of suitable simulants is critical to achieving the goals of the test program. WTP personnel requested the Savannah River National Laboratory (SRNL) to assist with development of simulants for use in FSVT. Among the tasks assigned to SRNL was to develop a list of waste properties that are important to pulse-jet mixer (PJM) performance in WTP vessels with elevated concentrations of solids.

  4. Pelletizing of fuel blends mixed with lignin for energetic use in small scale combustion units

    Directory of Open Access Journals (Sweden)

    Frank Döhling

    2015-03-01

    Full Text Available As part of future bio-economy concepts technical lignin, by-products derived from the pulp- and paper industry, may be recycled for further utilization. Via a specially developed process the liquid lignin lye can be converted into a solid state. The lignin granules were mixed with a blend of canola straw and peeled oat bran in different proportions (1–2 wt.-% to adjust the characteristics of the mixtures for pelletizing. Combustion tests with the produced pellets were carried out in a small scale combustion unit (25 kW showing that depending on the amount and kind of lignin CO-, SO2- and particulate matter emissions are affected. Through further optimization of fuel mixtures and by means of secondary measures existing emission limits could be complied.

  5. How well-mixed is well mixed? Hydrodynamic-biokinetic model integration in an aerated tank of a full-scale water resource recovery facility.

    Science.gov (United States)

    Rehman, Usman; Audenaert, Wim; Amerlinck, Youri; Maere, Thomas; Arnaldos, Marina; Nopens, Ingmar

    2017-10-01

    Current water resource recovery facility (WRRF) models only consider local concentration variations caused by inadequate mixing to a very limited extent, which often leads to a need for (rigorous) calibration. The main objective of this study is to visualize local impacts of mixing by developing an integrated hydrodynamic-biokinetic model for an aeration compartment of a full-scale WRRF. Such a model is able to predict local variations in concentrations and thus allows judging their importance at a process level. In order to achieve this, full-scale hydrodynamics have been simulated using computational fluid dynamics (CFD) through a detailed description of the gas and liquid phases and validated experimentally. In a second step, full ASM1 biokinetic model was integrated with the CFD model to account for the impact of mixing at the process level. The integrated model was subsequently used to evaluate effects of changing influent and aeration flows on process performance. Regions of poor mixing resulting in non-uniform substrate distributions were observed even in areas commonly assumed to be well-mixed. The concept of concentration distribution plots was introduced to quantify and clearly present spatial variations in local process concentrations. Moreover, the results of the CFD-biokinetic model were concisely compared with a conventional tanks-in-series (TIS) approach. It was found that TIS model needs calibration and a single parameter set does not suffice to describe the system under both dry and wet weather conditions. Finally, it was concluded that local mixing conditions have significant consequences in terms of optimal sensor location, control system design and process evaluation.

  6. A mixed-integer linear programming approach to the reduction of genome-scale metabolic networks.

    Science.gov (United States)

    Röhl, Annika; Bockmayr, Alexander

    2017-01-03

    Constraint-based analysis has become a widely used method to study metabolic networks. While some of the associated algorithms can be applied to genome-scale network reconstructions with several thousands of reactions, others are limited to small or medium-sized models. In 2015, Erdrich et al. introduced a method called NetworkReducer, which reduces large metabolic networks to smaller subnetworks, while preserving a set of biological requirements that can be specified by the user. Already in 2001, Burgard et al. developed a mixed-integer linear programming (MILP) approach for computing minimal reaction sets under a given growth requirement. Here we present an MILP approach for computing minimum subnetworks with the given properties. The minimality (with respect to the number of active reactions) is not guaranteed by NetworkReducer, while the method by Burgard et al. does not allow specifying the different biological requirements. Our procedure is about 5-10 times faster than NetworkReducer and can enumerate all minimum subnetworks in case there exist several ones. This allows identifying common reactions that are present in all subnetworks, and reactions appearing in alternative pathways. Applying complex analysis methods to genome-scale metabolic networks is often not possible in practice. Thus it may become necessary to reduce the size of the network while keeping important functionalities. We propose a MILP solution to this problem. Compared to previous work, our approach is more efficient and allows computing not only one, but even all minimum subnetworks satisfying the required properties.

  7. Experimental Investigation of Large-Scale Flow Structures in Turbulent Mixed Convection

    Science.gov (United States)

    Koerner, Max; Resagk, Christian; Thess, Andre

    2014-11-01

    We report on experimental investigations of the temporal and spatial behavior of large-scale flow structures (LSC) in turbulent mixed convection. Using a reduced scale model room with a passenger cabin based geometry allows a global view on the LSCs, which are mainly responsible for thermal comfort and air quality within rooms. Moreover, the usage of pressurized working gases like air or sulfur hexafluoride (SF6) enables experimental investigations within broad ranges of the Reynolds number Re and Rayleigh number Ra. Thus, it is also possible to achieve realistic values of the dimensionless numbers allowing direct conclusions to be drawn about the LSCs in rooms similar to passenger cabins. The LSCs are determined by measurements of the 2D velocity field using a 2D2C particle image velocimetry system. In order to characterize three-dimensionally evolved flow structures, the measurement plane can be moved throughout the depth of the model room. We found very complex LSCs ranging from two-dimensional to three-dimensional structures and from one-roll systems over simple two-roll ones to chaotic behavior of the flow. The formation the LSCs has a strong dependency on the relation between Re and Ra and they often show distinct coherent oscillations. The authors gratefully acknowledge the DFG (Grant No. TH497-32-1) for financial support.

  8. Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Chitta, L. P.; Peter, H.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Iniesta, J. C. Del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain); Schmidt, W. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Knölker, M., E-mail: chitta@mps.mpg.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)

    2017-03-01

    How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca ii H images obtained from the Sunrise Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.

  9. Development of a Hybrid RANS/LES Method for Turbulent Mixing Layers

    Science.gov (United States)

    Georgiadis, Nicholas J.; Alexander, J. Iwan D.; Reshotko, Eli

    2001-01-01

    Significant research has been underway for several years in NASA Glenn Research Center's nozzle branch to develop advanced computational methods for simulating turbulent flows in exhaust nozzles. The primary efforts of this research have concentrated on improving our ability to calculate the turbulent mixing layers that dominate flows both in the exhaust systems of modern-day aircraft and in those of hypersonic vehicles under development. As part of these efforts, a hybrid numerical method was recently developed to simulate such turbulent mixing layers. The method developed here is intended for configurations in which a dominant structural feature provides an unsteady mechanism to drive the turbulent development in the mixing layer. Interest in Large Eddy Simulation (LES) methods have increased in recent years, but applying an LES method to calculate the wide range of turbulent scales from small eddies in the wall-bounded regions to large eddies in the mixing region is not yet possible with current computers. As a result, the hybrid method developed here uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall-bounded regions entering a mixing section and uses a LES procedure to calculate the mixing-dominated regions. A numerical technique was developed to enable the use of the hybrid RANS-LES method on stretched, non-Cartesian grids. With this technique, closure for the RANS equations is obtained by using the Cebeci-Smith algebraic turbulence model in conjunction with the wall-function approach of Ota and Goldberg. The LES equations are closed using the Smagorinsky subgrid scale model. Although the function of the Cebeci-Smith model to replace all of the turbulent stresses is quite different from that of the Smagorinsky subgrid model, which only replaces the small subgrid turbulent stresses, both are eddy viscosity models and both are derived at least in part from mixing-length theory. The similar formulation of these two models enables the RANS

  10. Large-scale tomographic PIV in forced and mixed convection using a parallel SMART version

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, Matthias; Ehrenfried, Klaus; Bosbach, Johannes; Wagner, Claus [German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Goettingen (Germany)

    2012-07-15

    Large-scale tomographic particle image velocimetry (tomographic PIV) was used to study large-scale flow structures of turbulent convective air flow in an elongated rectangular convection cell. Three flow cases have been investigated, that is, pure forced convection and mixed convection at two different Archimedes numbers. The Reynolds number was constant at Re=1.04 x 10{sup 4} for all cases, while the Archimedes numbers were Ar=2.1 and 3.6 for the mixed convection cases, corresponding to Rayleigh numbers of Ra=1.6 x 10{sup 8} and 2.8 x 10{sup 8}, respectively. In these investigations, the size of the measurement volume was as large as 840 mm x 500 mm x 240 mm. To allow for statistical analysis of the measured instantaneous flow fields, a large number of samples needed to be evaluated. Therefore, an efficient parallel implementation of the tomographic PIV algorithm was developed, which is based on a version of the simultaneous multiplicative reconstruction technique (SMART). Our algorithm distinguishes itself amongst other features by the fact that it does not store any weighting coefficients. The measurement of forced convection reveals an almost two-dimensional roll structure, which is orientated in the longitudinal cell direction. Its mean velocity field exhibits a core line with a wavy shape and a wavelength, which corresponds to the height and depth of the cell. In the instantaneous fields, the core line oscillates around its mean position. Under the influence of thermal buoyancy forces, the global structure of the flow field changes significantly. At lower Archimedes numbers, the resulting roll-like structure is shifted and deformed as compared to pure forced convection. Additionally, the core line oscillates much more strongly around its mean position due to the interaction of the roll structure with the rising hot air. If the Archimedes number is further increased, the roll-like structure breaks up into four counter-rotating convection rolls as a result of

  11. Microbiological-enhanced mixing across scales during in-situ bioreduction of metals and radionuclides at Department of Energy Sites

    Energy Technology Data Exchange (ETDEWEB)

    Valocchi, Albert [Univ. of Illinois, Urbana-Champaign, IL (United States); Werth, Charles [Univ. of Texas, Austin, TX (United States); Liu, Wen-Tso [Univ. of Illinois, Urbana-Champaign, IL (United States); Sanford, Robert [Univ. of Illinois, Urbana-Champaign, IL (United States); Nakshatrala, Kalyan [Univ. of Houston, TX (United States)

    2015-10-20

    Bioreduction is being actively investigated as an effective strategy for subsurface remediation and long-term management of DOE sites contaminated by metals and radionuclides (i.e. U(VI)). These strategies require manipulation of the subsurface, usually through injection of chemicals (e.g., electron donor) which mix at varying scales with the contaminant to stimulate metal reducing bacteria. There is evidence from DOE field experiments suggesting that mixing limitations of substrates at all scales may affect biological growth and activity for U(VI) reduction. Although current conceptual models hold that biomass growth and reduction activity is limited by physical mixing processes, a growing body of literature suggests that reaction could be enhanced by cell-to-cell interaction occurring over length scales extending tens to thousands of microns. Our project investigated two potential mechanisms of enhanced electron transfer. The first is the formation of single- or multiple-species biofilms that transport electrons via direct electrical connection such as conductive pili (i.e. ‘nanowires’) through biofilms to where the electron acceptor is available. The second is through diffusion of electron carriers from syntrophic bacteria to dissimilatory metal reducing bacteria (DMRB). The specific objectives of this work are (i) to quantify the extent and rate that electrons are transported between microorganisms in physical mixing zones between an electron donor and electron acceptor (e.g. U(IV)), (ii) to quantify the extent that biomass growth and reaction are enhanced by interspecies electron transport, and (iii) to integrate mixing across scales (e.g., microscopic scale of electron transfer and macroscopic scale of diffusion) in an integrated numerical model to quantify these mechanisms on overall U(VI) reduction rates. We tested these hypotheses with five tasks that integrate microbiological experiments, unique micro-fluidics experiments, flow cell experiments, and

  12. Modeling Macro- and Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes

    Science.gov (United States)

    Menon, Suresh

    1998-01-01

    Simulation of turbulent mixing and chemical processes in the near-field plume and plume-vortex regimes has been successfully carried out recently using a reduced gas phase kinetics mechanism which substantially decreased the computational cost. A detailed mechanism including gas phase HOx, NOx, and SOx chemistry between the aircraft exhaust and the ambient air in near-field aircraft plumes is compiled. A reduced mechanism capturing the major chemical pathways is developed. Predictions by the reduced mechanism are found to be in good agreement with those by the detailed mechanism. With the reduced chemistry, the computer CPU time is saved by a factor of more than 3.5 for the near-field plume modeling. Distributions of major chemical species are obtained and analyzed. The computed sensitivities of major species with respect to reaction step are deduced for identification of the dominant gas phase kinetic reaction pathways in the jet plume. Both the near field plume and the plume-vortex regimes were investigated using advanced mixing models. In the near field, a stand-alone mixing model was used to investigate the impact of turbulent mixing on the micro- and macro-scale mixing processes using a reduced reaction kinetics model. The plume-vortex regime was simulated using a large-eddy simulation model. Vortex plume behind Boeing 737 and 747 aircraft was simulated along with relevant kinetics. Many features of the computed flow field show reasonable agreement with data. The entrainment of the engine plumes into the wing tip vortices and also the partial detrainment of the plume were numerically captured. The impact of fluid mechanics on the chemical processes was also studied. Results show that there are significant differences between spatial and temporal simulations especially in the predicted SO3 concentrations. This has important implications for the prediction of sulfuric acid aerosols in the wake and may partly explain the discrepancy between past numerical studies

  13. Clinical utilisation of the "G.T. MSRS", the rating scale for mixed states: 35 cases report.

    Science.gov (United States)

    Tavormina, Giuseppe

    2015-09-01

    The knowledge of the clinical features of the mixed states and of the symptoms of the "mixity" of mood disorders is crucial: to mis-diagnose or mis-treat patients with these symptoms may increase the suicide risk and make worse the evolution of mood disorders. The rating scale "G.T. MSRS" has been designed to improve the clinical effectiveness of both psychiatrists and GPs by enabling them to make an early "general" diagnosis of mixed states. This study presents some cases in which the "G.T. MSRS" scale has been used, in order to demonstrate its usefullness.

  14. Aerosol indirect effects in the ECHAM5-HAM2 climate model with subgrid cloud microphysics in a stochastic framework

    Science.gov (United States)

    Tonttila, Juha; Räisänen, Petri; Järvinen, Heikki

    2015-04-01

    Representing cloud properties in global climate models remains a challenging topic, which to a large extent is due to cloud processes acting on spatial scales much smaller than the typical model grid resolution. Several attempts have been made to alleviate this problem. One such method was introduced in the ECHAM5-HAM2 climate model by Tonttila et al. (2013), where cloud microphysical properties, along with the processes of cloud droplet activation and autoconversion, were computed using an ensemble of stochastic subcolumns within the climate model grid columns. Moreover, the subcolumns were sampled for radiative transfer using the Monte Carlo Independent Column Approximation approach. The same model version is used in this work (Tonttila et al. 2014), where 5-year nudged integrations are performed with a series of different model configurations. Each run is performed twice, once with pre-industrial (PI, year 1750) aerosol emission conditions and once with present-day (PD, year 2000) conditions, based on the AEROCOM emission inventories. The differences between PI and PD simulations are used to estimate the impact of anthropogenic aerosols on clouds and the aerosol indirect effect (AIE). One of the key results is that when both cloud activation and autoconversion are computed in the subcolumn space, the aerosol-induced PI-to-PD change in the global-mean liquid water path is up to 19 % smaller than in the reference with grid-scale computations. Together with similar changes in the cloud droplet number concentration, this influences the cloud radiative effects and thus the AIE, which is estimated as the difference in the net cloud radiative effect between PI and PD conditions. Accordingly, the AIE is reduced by 14 %, from 1.59 W m-2 in the reference model version to 1.37 W m-2 in the experimental model configuration. The results of this work explicitly show that careful consideration of the subgrid variability in cloud microphysical properties and consistent

  15. The effects of the sub-grid variability of soil and land cover data on agricultural droughts in Germany

    Science.gov (United States)

    Kumar, Rohini; Samaniego, Luis; Zink, Matthias

    2013-04-01

    Simulated soil moisture from land surface or water balance models is increasingly used to characterize and/or monitor the development of agricultural droughts at regional and global scales (e.g. NLADS, EDO, GLDAS). The skill of these models to accurately replicate hydrologic fluxes and state variables is strongly dependent on the quality meteorological forcings, the conceptualization of dominant processes, and the parameterization scheme used to incorporate the variability of land surface properties (e.g. soil, topography, and vegetation) at a coarser spatial resolutions (e.g. at least 4 km). The goal of this study is to analyze the effects of the sub-grid variability of soil texture and land cover properties on agricultural drought statistics such as duration, severity, and areal extent. For this purpose, a process based mesoscale hydrologic model (mHM) is used to create two sets of daily soil moisture fields over Germany at the spatial resolution of (4 × 4) km2 from 1950 to 2011. These simulations differ from each other only on the manner in which the land surface properties are accounted within the model. In the first set, soil moisture fields are obtained with the multiscale parameter regionalization (MPR) scheme (Samaniego, et. al. 2010, Kumar et. al. 2012), which explicitly takes the sub-grid variability of soil texture and land cover properties into account. In the second set, on the contrary, a single dominant soil and land cover class is used for ever grid cell at 4 km. Within each set, the propagation of the parameter uncertainty into the soil moisture simulations is also evaluated using an ensemble of 100 best global parameter sets of mHM (Samaniego, et. al. 2012). To ensure comparability, both sets of this ensemble simulations are forced with the same fields of meteorological variables (e.g., precipitation, temperature, and potential evapotranspiration). Results indicate that both sets of model simulations, with and without the sub-grid variability of

  16. PILOT SCALE TESTING OF MONOSODIUM TITANATE MIXING FOR THE SRS SMALL COLUMN ION EXCHANGE PROCESS - 11224

    Energy Technology Data Exchange (ETDEWEB)

    Poirier, M.; Restivo, M.; Williams, M.; Herman, D.; Steeper, T.

    2011-01-25

    The Small Column Ion Exchange (SCIX) process is being developed to remove cesium, strontium, and select actinides from Savannah River Site (SRS) Liquid Waste using an existing waste tank (i.e., Tank 41H) to house the process. Savannah River National Laboratory (SRNL) is conducting pilot-scale mixing tests to determine the pump requirements for suspending monosodium titanate (MST), crystalline silicotitanate (CST), and simulated sludge. The purpose of this pilot scale testing is to determine the requirements for the pumps to suspend the MST particles so that they can contact the strontium and actinides in the liquid and be removed from the tank. The pilot-scale tank is a 1/10.85 linear scaled model of SRS Tank 41H. The tank diameter, tank liquid level, pump nozzle diameter, pump elevation, and cooling coil diameter are all 1/10.85 of their dimensions in Tank 41H. The pump locations correspond to the proposed locations in Tank 41H by the SCIX program (Risers B5 and B2 for two pump configurations and Risers B5, B3, and B1 for three pump configurations). The conclusions from this work follow: (i) Neither two standard slurry pumps nor two quad volute slurry pumps will provide sufficient power to initially suspend MST in an SRS waste tank. (ii) Two Submersible Mixer Pumps (SMPs) will provide sufficient power to initially suspend MST in an SRS waste tank. However, the testing shows the required pump discharge velocity is close to the maximum discharge velocity of the pump (within 12%). (iii) Three SMPs will provide sufficient power to initially suspend MST in an SRS waste tank. The testing shows the required pump discharge velocity is 66% of the maximum discharge velocity of the pump. (iv) Three SMPs are needed to resuspend MST that has settled in a waste tank at nominal 45 C for four weeks. The testing shows the required pump discharge velocity is 77% of the maximum discharge velocity of the pump. Two SMPs are not sufficient to resuspend MST that settled under these

  17. Large-Scale Bi-Level Strain Design Approaches and Mixed-Integer Programming Solution Techniques

    Science.gov (United States)

    Kim, Joonhoon; Reed, Jennifer L.; Maravelias, Christos T.

    2011-01-01

    The use of computational models in metabolic engineering has been increasing as more genome-scale metabolic models and computational approaches become available. Various computational approaches have been developed to predict how genetic perturbations affect metabolic behavior at a systems level, and have been successfully used to engineer microbial strains with improved primary or secondary metabolite production. However, identification of metabolic engineering strategies involving a large number of perturbations is currently limited by computational resources due to the size of genome-scale models and the combinatorial nature of the problem. In this study, we present (i) two new bi-level strain design approaches using mixed-integer programming (MIP), and (ii) general solution techniques that improve the performance of MIP-based bi-level approaches. The first approach (SimOptStrain) simultaneously considers gene deletion and non-native reaction addition, while the second approach (BiMOMA) uses minimization of metabolic adjustment to predict knockout behavior in a MIP-based bi-level problem for the first time. Our general MIP solution techniques significantly reduced the CPU times needed to find optimal strategies when applied to an existing strain design approach (OptORF) (e.g., from ∼10 days to ∼5 minutes for metabolic engineering strategies with 4 gene deletions), and identified strategies for producing compounds where previous studies could not (e.g., malate and serine). Additionally, we found novel strategies using SimOptStrain with higher predicted production levels (for succinate and glycerol) than could have been found using an existing approach that considers network additions and deletions in sequential steps rather than simultaneously. Finally, using BiMOMA we found novel strategies involving large numbers of modifications (for pyruvate and glutamate), which sequential search and genetic algorithms were unable to find. The approaches and solution

  18. Large-scale bi-level strain design approaches and mixed-integer programming solution techniques.

    Science.gov (United States)

    Kim, Joonhoon; Reed, Jennifer L; Maravelias, Christos T

    2011-01-01

    The use of computational models in metabolic engineering has been increasing as more genome-scale metabolic models and computational approaches become available. Various computational approaches have been developed to predict how genetic perturbations affect metabolic behavior at a systems level, and have been successfully used to engineer microbial strains with improved primary or secondary metabolite production. However, identification of metabolic engineering strategies involving a large number of perturbations is currently limited by computational resources due to the size of genome-scale models and the combinatorial nature of the problem. In this study, we present (i) two new bi-level strain design approaches using mixed-integer programming (MIP), and (ii) general solution techniques that improve the performance of MIP-based bi-level approaches. The first approach (SimOptStrain) simultaneously considers gene deletion and non-native reaction addition, while the second approach (BiMOMA) uses minimization of metabolic adjustment to predict knockout behavior in a MIP-based bi-level problem for the first time. Our general MIP solution techniques significantly reduced the CPU times needed to find optimal strategies when applied to an existing strain design approach (OptORF) (e.g., from ∼10 days to ∼5 minutes for metabolic engineering strategies with 4 gene deletions), and identified strategies for producing compounds where previous studies could not (e.g., malate and serine). Additionally, we found novel strategies using SimOptStrain with higher predicted production levels (for succinate and glycerol) than could have been found using an existing approach that considers network additions and deletions in sequential steps rather than simultaneously. Finally, using BiMOMA we found novel strategies involving large numbers of modifications (for pyruvate and glutamate), which sequential search and genetic algorithms were unable to find. The approaches and solution

  19. Large-scale bi-level strain design approaches and mixed-integer programming solution techniques.

    Directory of Open Access Journals (Sweden)

    Joonhoon Kim

    Full Text Available The use of computational models in metabolic engineering has been increasing as more genome-scale metabolic models and computational approaches become available. Various computational approaches have been developed to predict how genetic perturbations affect metabolic behavior at a systems level, and have been successfully used to engineer microbial strains with improved primary or secondary metabolite production. However, identification of metabolic engineering strategies involving a large number of perturbations is currently limited by computational resources due to the size of genome-scale models and the combinatorial nature of the problem. In this study, we present (i two new bi-level strain design approaches using mixed-integer programming (MIP, and (ii general solution techniques that improve the performance of MIP-based bi-level approaches. The first approach (SimOptStrain simultaneously considers gene deletion and non-native reaction addition, while the second approach (BiMOMA uses minimization of metabolic adjustment to predict knockout behavior in a MIP-based bi-level problem for the first time. Our general MIP solution techniques significantly reduced the CPU times needed to find optimal strategies when applied to an existing strain design approach (OptORF (e.g., from ∼10 days to ∼5 minutes for metabolic engineering strategies with 4 gene deletions, and identified strategies for producing compounds where previous studies could not (e.g., malate and serine. Additionally, we found novel strategies using SimOptStrain with higher predicted production levels (for succinate and glycerol than could have been found using an existing approach that considers network additions and deletions in sequential steps rather than simultaneously. Finally, using BiMOMA we found novel strategies involving large numbers of modifications (for pyruvate and glutamate, which sequential search and genetic algorithms were unable to find. The approaches and

  20. Sub-Grid Modeling of Electrokinetic Effects in Micro Flows

    Science.gov (United States)

    Chen, C. P.

    2005-01-01

    Advances in micro-fabrication processes have generated tremendous interests in miniaturizing chemical and biomedical analyses into integrated microsystems (Lab-on-Chip devices). To successfully design and operate the micro fluidics system, it is essential to understand the fundamental fluid flow phenomena when channel sizes are shrink to micron or even nano dimensions. One important phenomenon is the electro kinetic effect in micro/nano channels due to the existence of the electrical double layer (EDL) near a solid-liquid interface. Not only EDL is responsible for electro-osmosis pumping when an electric field parallel to the surface is imposed, EDL also causes extra flow resistance (the electro-viscous effect) and flow anomaly (such as early transition from laminar to turbulent flow) observed in pressure-driven microchannel flows. Modeling and simulation of electro-kinetic effects on micro flows poses significant numerical challenge due to the fact that the sizes of the double layer (10 nm up to microns) are very thin compared to channel width (can be up to 100 s of m). Since the typical thickness of the double layer is extremely small compared to the channel width, it would be computationally very costly to capture the velocity profile inside the double layer by placing sufficient number of grid cells in the layer to resolve the velocity changes, especially in complex, 3-d geometries. Existing approaches using "slip" wall velocity and augmented double layer are difficult to use when the flow geometry is complicated, e.g. flow in a T-junction, X-junction, etc. In order to overcome the difficulties arising from those two approaches, we have developed a sub-grid integration method to properly account for the physics of the double layer. The integration approach can be used on simple or complicated flow geometries. Resolution of the double layer is not needed in this approach, and the effects of the double layer can be accounted for at the same time. With this

  1. Two Scales of Mixed Rossby-gravity and Kelvin Waves in the lower Stratosphere

    Science.gov (United States)

    Trenberth, K. E.; Karl, T. R.; Xie, S. P.; Nieves, V.; Tung, K. K.; Roemmich, D. H.; Kiladis, G. N.; Gehne, M.; Dias, J.

    2015-12-01

    Two scales of mixed Rossby-gravity (MRG) and Kelvin waves in the lower stratosphere are identified through space time spectral, cross spectral and Principal Component analysis of filtered dynamical fields from radiosonde and reanalysis data. A standard covariance matrix EOF analysis of filtered wind along the equator at 50 hPa is used to isolate MRG and Kelvin waves, using ERA Interim analyses for the entire period 1979-2012. This approach uses 2-6 day meridional wind for MRG waves and 10-25 day eastward zonal wind for Kelvin waves as a basis for the two independent EOF analyses, respectively. Raw wind, geopotential height and CLAUS brightness temperature are then projected onto the EOF PCs at all levels from 1000 to 1 hPa to obtain the structure and evolution of the waves. In all cases EOF pairs are obtained corresponding to propagating modes. The classical Yanai MRG waves are readily identified, and have periods of around 4 days and zonal wavenumber four meridional wind and streamfunction structures centered on the equator, with antisymmetric zonal wind and geopotential as expected. However a faster mode, with a period of around three days is also identified, with a zonal wavenumber three structure. This latter mode is actually much more coherent in cross spectra between antisymmetric zonal wind, geopotential and temperature at 10 degrees north and south. This scale matches the equatorial Rossby radius expected of a disturbance with an equivalent depth of about 120 meters, as identified in space-time spectra of various dynamical quantities obtained from lower stratospheric radiosonde and reanalyses. Strong modulation of this MRG activity by the QBO is also seen for both modes. Kelvin waves are similarly identified using equatorial zonal wind filtered for 10-25 day eastward travelling fluctuations. Two scales are evident here: a wave one and also a wave two disturbance, each with periods of around 14 days. Evidence that the Kelvin and MRG modes are excited by

  2. The Storm Surge and Sub-Grid Inundation Modeling in New York City during Hurricane Sandy

    Directory of Open Access Journals (Sweden)

    Harry V. Wang

    2014-03-01

    Full Text Available Hurricane Sandy inflicted heavy damage in New York City and the New Jersey coast as the second costliest storm in history. A large-scale, unstructured grid storm tide model, Semi-implicit Eulerian Lagrangian Finite Element (SELFE, was used to hindcast water level variation during Hurricane Sandy in the mid-Atlantic portion of the U.S. East Coast. The model was forced by eight tidal constituents at the model’s open boundary, 1500 km away from the coast, and the wind and pressure fields from atmospheric model Regional Atmospheric Modeling System (RAMS provided by Weatherflow Inc. The comparisons of the modeled storm tide with the NOAA gauge stations from Montauk, NY, Long Island Sound, encompassing New York Harbor, Atlantic City, NJ, to Duck, NC, were in good agreement, with an overall root mean square error and relative error in the order of 15–20 cm and 5%–7%, respectively. Furthermore, using large-scale model outputs as the boundary conditions, a separate sub-grid model that incorporates LIDAR data for the major portion of the New York City was also set up to investigate the detailed inundation process. The model results compared favorably with USGS’ Hurricane Sandy Mapper database in terms of its timing, local inundation area, and the depth of the flooding water. The street-level inundation with water bypassing the city building was created and the maximum extent of horizontal inundation was calculated, which was within 30 m of the data-derived estimate by USGS.

  3. The Impact of Test Dimensionality, Common-Item Set Format, and Scale Linking Methods on Mixed-Format Test Equating

    Science.gov (United States)

    Öztürk-Gübes, Nese; Kelecioglu, Hülya

    2016-01-01

    The purpose of this study was to examine the impact of dimensionality, common-item set format, and different scale linking methods on preserving equity property with mixed-format test equating. Item response theory (IRT) true-score equating (TSE) and IRT observed-score equating (OSE) methods were used under common-item nonequivalent groups design.…

  4. A Three-Dimensional Scale-adaptive Turbulent Kinetic Energy Model in ARW-WRF Model

    Science.gov (United States)

    Zhang, Xu; Bao, Jian-Wen; Chen, Baode

    2017-04-01

    A new three-dimensional (3D) turbulent kinetic energy (TKE) subgrid mixing model is developed to address the problem of simulating the convective boundary layer (CBL) across the terra incognita in the Advanced Research version of the Weather Research and Forecasting Model (ARW-WRF). The new model combines the horizontal and vertical subgrid turbulent mixing into a single energetically consistent framework, in contrast to the convectional one-dimensional (1D) planetary boundary layer (PBL) schemes. The transition between large-eddy simulation (LES) and mesoscale limit is accomplished in the new scale-adaptive model. A series of dry CBL and real-time simulations using the WRF model are carried out, in which the newly-developed, scale-adaptive, more general and energetically consistent TKE-based model is compared with the conventional 1D TKE-based PBL schemes for parameterizing vertical subgrid turbulent mixing against the WRF LES dataset and observations. The characteristics of the WRF-simulated results using the new and conventional schemes are compared. The importance of including the nonlocal component in the vertical buoyancy specification in the newly-developed general TKE-based scheme is illustrated. The improvements of the new scheme over convectional PBL schemes across the terra incognita can be seen in the partitioning of vertical flux profiles. Through comparing the results from the simulations against the WRF LES dataset and observations, we will show the feasibility of using the new scheme in the WRF model in the lieu of the conventional PBL parameterization schemes.

  5. Enhancing Representation of Subgrid Land Surface Characteristics in the Community Land Model

    Science.gov (United States)

    Ke, Y.; Coleman, A.; Leung, L.; Huang, M.; Li, H.; Wigmosta, M. S.

    2011-12-01

    The Community Land Model (CLM) is the land surface model used in the Community Earth System Model (CESM). In CLM each grid cell is composed of subgrid land units, snow/soil columns and plant functional types (PFTs). In the current version of CLM (CLM4.0), land surface parameters such as vegetated/non-vegetated land cover and surface characteristics including fractional glacier, lake, wetland, urban area, and PFT, and its associated leaf area index (LAI), stem area index (SAI), and canopy top and bottom heights are provided at 0.5° or coarser resolution. This study aims to enhance the representation of the land surface data by (1) creating higher resolution (0.05° or higher) global land surface parameters, and (2) developing an effective and accurate subgrid classification scheme for elevation and PFTs so that variations of land surface processes due to the subgrid distribution of PFTs and elevation can be represented in CLM. To achieve higher-resolution global land surface parameters, MODIS 500m land cover product (MCD12Q1) collected in 2005 was used to generate percentage of glacier, lake, wetland, and urban area and fractional PFTs at 0.05° resolution. Spatially and temporally continuous and consistent global LAI data re-processed and improved from MOD15A2 (http://globalchange.bnu.edu.cn/research/lai), combined with the PFT data, was used to create LAI, SAI, and, canopy top and bottom height data. 30-second soil texture data was obtained from a hybrid 30-second State Soil Geographic Database (STATSGO) and the 5-minute Food and Agriculture Organization two-layer 16-category soil texture dataset. The relationship between global distribution of PFTs and 1-km resolution elevation data is being analyzed to develop a subgrid classification of PFT and elevation. Statistical analysis is being conducted to compare different subgrid classification methods to select a method that explains the highest percentage of subgrid variance in both PFT and elevation distribution

  6. An investigation of the sub-grid variability of trace gases and aerosols for global climate modeling

    Directory of Open Access Journals (Sweden)

    Y. Qian

    2010-07-01

    Full Text Available One fundamental property and limitation of grid based models is their inability to identify spatial details smaller than the grid cell size. While decades of work have gone into developing sub-grid treatments for clouds and land surface processes in climate models, the quantitative understanding of sub-grid processes and variability for aerosols and their precursors is much poorer. In this study, WRF-Chem is used to simulate the trace gases and aerosols over central Mexico during the 2006 MILAGRO field campaign, with multiple spatial resolutions and emission/terrain scenarios. Our analysis focuses on quantifying the sub-grid variability (SGV of trace gases and aerosols within a typical global climate model grid cell, i.e. 75×75 km2.

    Our results suggest that a simulation with 3-km horizontal grid spacing adequately reproduces the overall transport and mixing of trace gases and aerosols downwind of Mexico City, while 75-km horizontal grid spacing is insufficient to represent local emission and terrain-induced flows along the mountain ridge, subsequently affecting the transport and mixing of plumes from nearby sources. Therefore, the coarse model grid cell average may not correctly represent aerosol properties measured over polluted areas. Probability density functions (PDFs for trace gases and aerosols show that secondary trace gases and aerosols, such as O3, sulfate, ammonium, and nitrate, are more likely to have a relatively uniform probability distribution (i.e. smaller SGV over a narrow range of concentration values. Mostly inert and long-lived trace gases and aerosols, such as CO and BC, are more likely to have broad and skewed distributions (i.e. larger SGV over polluted regions. Over remote areas, all trace gases and aerosols are more uniformly distributed compared to polluted areas. Both CO and O3 SGV vertical profiles are nearly constant within the PBL during daytime, indicating that trace gases

  7. A flexible well-mixed milliliter-scale reactor with high oxygen transfer rate for microbial cultivations

    DEFF Research Database (Denmark)

    Bolic, Andrijana; Larsson, Hilde Kristina; Hugelier, Siewert

    2016-01-01

    (one- and bi-directional).Computational fluid dynamics (CFD) was employed in order to simulate the mixing times, the oxygen transfer rates and the appearance and size of the gas-liquid interfaces in the 1 mL-scale bioreactor with unidirectional mixing and surface aeration.Mixing performance was tested...... and the oxygen transfer rate was determined experimentally as well. The obtained results show a good mixing time (between 0.4 s and 2 s) and a high oxygen transfer rate (kLa > 1000 h−1).The milliliter-scale bioreactor platform was used to cultivate Saccharomyces cerevisiae and Lactobacillus paracasei....... on the one side and a bioreactor with special designed magnetic stirrer and non-invasive optical sensors for measurement of pH, dissolved oxygen and optical density on the other side. The system has a high level of flexibility in terms of volume (0.5–2 mL), aeration (sparging and surface aeration) and mixing...

  8. Mixing of process heels, process solutions, and recycle streams: Results of the small-scale radioactive tests

    Energy Technology Data Exchange (ETDEWEB)

    GJ Lumetta; JP Bramson; OT Farmer III; LR Greenwood; FV Hoopes; MA Mann; MJ Steele; RT Steele; RG Swoboda; MW Urie

    2000-05-17

    Various recycle streams will be combined with the low-activity waste (LAW) or the high-level waste (HLW) feed solutions during the processing of the Hanford tank wastes by BNFL, Inc. In addition, the LAW and HLW feed solutions will also be mixed with heels present in the processing equipment. This report describes the results of a test conducted by Battelle to assess the effects of mixing specific process streams. Observations were made regarding adverse reactions (mainly precipitation) and effects on the Tc oxidation state (as indicated by K{sub d} measurements with SuperLig{reg_sign} 639). The work was conducted according to test plan BNFL-TP-29953-023, Rev. 0, Small Scale Mixing of Process Heels, Solutions, and Recycle Streams. The test went according to plan, with only minor deviations from the test plan. The deviations from the test plan are discussed in the experimental section.

  9. MELCOR analyses of NUPEC`s large-scale hydrogen mixing test-II

    Energy Technology Data Exchange (ETDEWEB)

    Tezuka, Hiroko [Nuclear Power Engineering Corporation, Tokyo (Japan); Ajisaka, Kazuhiro [Computer Software Development Co., Ltd., Tokyo (Japan)

    1995-12-31

    NUPEC has carried out hydrogen mixing tests to investigate hydrogen distribution behavior within a model containment and to provide a set of experimental data for validation of severe accident analysis codes.

  10. Morphological changes of a superconducting phase in a mixed state with a normal current: a multiple scale analysis

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyay, A [Department of Chemistry, University of Warwick (United Kingdom)

    2008-03-21

    The mixed states of superconducting (SC) and normal (N) phases in one-dimensional systems are characterized by several phase slips and localization of the order parameter of the SC phase. The phenomenon is explained on the basis of a complex Ginzburg Landau (CGL) model. We present a simple analysis of the system on multiple scales to capture localization and phase slips when phases coexist. (fast track communication)

  11. Mixing Studies in a 1:60 scale model of a cornerfired boiler with OFA

    DEFF Research Database (Denmark)

    Matlok, Simon; Scheel Larsen, Poul; Gjernes, Erik

    1998-01-01

    , spatial scales and correlations) as function of distance downstream of point of injection. Experimental results are compared to those of numerical calculations. The visualization scheme is analysed for experimental uncertainties in terms of calibration procedure, seeding type and concentration, scale...

  12. Mindful Leaders in Highly Effective Schools: A Mixed-Method Application of Hoy's M-Scale

    Science.gov (United States)

    Kearney, W. Sean; Kelsey, Cheryl; Herrington, David

    2013-01-01

    This article presents a mixed-method study utilizing teacher ratings of principal mindfulness from 149 public schools in Texas and follow-up qualitative data analysis through semi-structured interviews conducted with the top 10 percent of princeipals identified as mindful. This research is based on the theoretical framework of mindfulness as…

  13. Low-frequency scaling of the standard and mixed magnetic field and Müller integral equations

    KAUST Repository

    Bogaert, Ignace

    2014-02-01

    The standard and mixed discretizations for the magnetic field integral equation (MFIE) and the Müller integral equation (MUIE) are investigated in the context of low-frequency (LF) scattering problems involving simply connected scatterers. It is proved that, at low frequencies, the frequency scaling of the nonsolenoidal part of the solution current can be incorrect for the standard discretization. In addition, it is proved that the frequency scaling obtained with the mixed discretization is correct. The reason for this problem in the standard discretization scheme is the absence of exact solenoidal currents in the rotated RWG finite element space. The adoption of the mixed discretization scheme eliminates this problem and leads to a well-conditioned system of linear equations that remains accurate at low frequencies. Numerical results confirm these theoretical predictions and also show that, when the frequency is lowered, a finer and finer mesh is required to keep the accuracy constant with the standard discretization. © 1963-2012 IEEE.

  14. Experimental investigation of in-vessel mixing phenomena in a VVER-1000 scaled test facility during unsteady asymmetric transients

    Energy Technology Data Exchange (ETDEWEB)

    Bucalossi, A. [EC JRC, (JRC F.5) PO Box 2, 1755 ZG Petten (Netherlands); Moretti, F.; Melideo, D. [Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Universita di Pisa (UNIPI) 2, via Diotisalvi, 56100 Pisa (Italy); Del Nevo, A., E-mail: delnevo@hotmail.com [Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Universita di Pisa (UNIPI) 2, via Diotisalvi, 56100 Pisa (Italy); D' Auria, F. [Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Universita di Pisa (UNIPI) 2, via Diotisalvi, 56100 Pisa (Italy); Hoehne, T. [Forschungszentrum Dresden-Rossendorf (FZD), P.O.B. 51 01 19, D-01314 Dresden (Germany); Lisenkov, E. [FSUE OKB Gidropress, Ordshonikidize 21, RU-142103 Podolsk, Moscow district (Russian Federation); Gallori, D. [AREVA NP SAS, Tour AREVA - 92084 Paris, La Defense Cedex (France)

    2011-08-15

    Highlights: > Five mixing experiments in a scaled model of a VVER-1000 are described and discussed. > In-vessel mixing investigations of the coolant properties distribution at the core inlet. > These tests brought an improvement to existing experimental database for TH code validation. - Abstract: In-vessel turbulent mixing phenomena affect the time and space distribution of coolant properties (e.g., boron concentration and temperature) at the core inlet which impacts consequently the neutron kinetics response. For reactor safety evaluation purposes and to characterize these phenomena it is necessary to set and validate appropriate numerical modelling tools to improve the current conservative predictions. With such purpose, an experimental campaign was carried out by OKB Gidropress, in the framework of the European Commission Project 'TACIS R2.02/02 - Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration) at core inlet'. The experiments were conducted on a scaled facility representing the primary system of a VVER-1000 including a detailed model of the Reactor Pressure Vessel with its internals. The simulated transients involved perturbations of coolant properties distribution providing a wide validation matrix. The main achievements of the set of experiments featuring transient asymmetric pump behaviour are presented in this paper. The potential of the obtained experimental database for the validation of thermal fluid dynamics numerical simulation tools is also discussed and the role of computational fluid dynamics in supporting the experimental data analysis is highlighted.

  15. Two-length-scale turbulence model for self-similar buoyancy-, shock-, and shear-driven mixing

    Science.gov (United States)

    Morgan, Brandon E.; Schilling, Oleg; Hartland, Tucker A.

    2018-01-01

    The three-equation k -L -a turbulence model [B. Morgan and M. Wickett, Three-equation model for the self-similar growth of Rayleigh-Taylor and Richtmyer-Meshkov instabilities, Phys. Rev. E 91, 043002 (2015), 10.1103/PhysRevE.91.043002] is extended by the addition of a second length scale equation. It is shown that the separation of turbulence transport and turbulence destruction length scales is necessary for simultaneous prediction of the growth parameter and turbulence intensity of a Kelvin-Helmholtz shear layer when model coefficients are constrained by similarity analysis. Constraints on model coefficients are derived that satisfy an ansatz of self-similarity in the low-Atwood-number limit and allow the determination of model coefficients necessary to recover expected experimental behavior. The model is then applied in one-dimensional simulations of Rayleigh-Taylor, reshocked Richtmyer-Meshkov, Kelvin-Helmholtz, and combined Rayleigh-Taylor-Kelvin-Helmholtz instability mixing layers to demonstrate that the expected growth rates are recovered numerically. Finally, it is shown in the case of combined instability that the model predicts a mixing width that is a linear combination of Rayleigh-Taylor and Kelvin-Helmholtz mixing processes.

  16. MELCOR analyses of NUPEC`s large-scale hydrogen mixing test-III

    Energy Technology Data Exchange (ETDEWEB)

    Tezuka, Hiroko [Nuclear Power Engineering Corp., Tokoyo (Japan); Ezzidi, A. [Computer Software Development Co., Ltd., Tokyo (Japan)

    1996-12-31

    The Nuclear Power Engineering Corporation has carried out hydrogen mixing and distribution tests to investigate hydrogen distribution behavior in a model containment and at the same time to provide a set of experimental data for the validation of severe-accident analysis codes. Some of the mixing tests have been analyzed by using the MELCOR code, which is an integral severe-accident analysis code used by nuclear safety regulators in Japan, and have been reported previously. In these reports, using the corresponding node compartment where experimental data were measured, there was a large discrepancy for helium concentration in some compartments, such as the gas-injected volume, dead-end compartment, and inside the dome. It was found that the discrepancy came from mainly nonhomogeneous helium gas concentration in these compartments. Noding and flow resistance parameter surveys were performed in the M-2-2 and M-8-1 test analyses to obtain a better prediction.

  17. Mixing and mass transfer in a pilot scale U-loop bioreactor

    DEFF Research Database (Denmark)

    Petersen, Leander Adrian Haaning; Villadsen, John; Jørgensen, Sten Bay

    2017-01-01

    A system capable of handling a large volumetric gas fraction while providing a high gas to liquid mass transfer is a necessity if the metanotrophic bacterium Methylococcus capsulatus is to be used in single cell protein (SCP) production. In this study mixing time and mass transfer coefficients we...... equipped with static mixers at modest volumetric liquid and gas flow rates. This article is protected by copyright. All rights reserved...

  18. Model Validation for Propulsion - On the TFNS and LES Subgrid Models for a Bluff Body Stabilized Flame

    Science.gov (United States)

    Wey, Thomas

    2017-01-01

    With advances in computational power and availability of distributed computers, the use of even the most complex of turbulent chemical interaction models in combustors and coupled analysis of combustors and turbines is now possible and more and more affordable for realistic geometries. Recent more stringent emission standards have enticed the development of more fuel-efficient and low-emission combustion system for aircraft gas turbine applications. It is known that the NOx emissions tend to increase dramatically with increasing flame temperature. It is well known that the major difficulty, when modeling the turbulence-chemistry interaction, lies in the high non-linearity of the reaction rate expressed in terms of the temperature and species mass fractions. The transport filtered density function (FDF) model and the linear eddy model (LEM), which both use local instantaneous values of the temperature and mass fractions, have been shown to often provide more accurate results of turbulent combustion. In the present, the time-filtered Navier-Stokes (TFNS) approach capable of capturing unsteady flow structures important for turbulent mixing in the combustion chamber and two different subgrid models, LEM-like and EUPDF-like, capable of emulating the major processes occurring in the turbulence-chemistry interaction will be used to perform reacting flow simulations of a selected test case. The selected test case from the Volvo Validation Rig was documented by Sjunnesson.

  19. A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves

    Science.gov (United States)

    Montzka, Carsten; Herbst, Michael; Weihermüller, Lutz; Verhoef, Anne; Vereecken, Harry

    2017-07-01

    Agroecosystem models, regional and global climate models, and numerical weather prediction models require adequate parameterization of soil hydraulic properties. These properties are fundamental for describing and predicting water and energy exchange processes at the transition zone between solid earth and atmosphere, and regulate evapotranspiration, infiltration and runoff generation. Hydraulic parameters describing the soil water retention (WRC) and hydraulic conductivity (HCC) curves are typically derived from soil texture via pedotransfer functions (PTFs). Resampling of those parameters for specific model grids is typically performed by different aggregation approaches such a spatial averaging and the use of dominant textural properties or soil classes. These aggregation approaches introduce uncertainty, bias and parameter inconsistencies throughout spatial scales due to nonlinear relationships between hydraulic parameters and soil texture. Therefore, we present a method to scale hydraulic parameters to individual model grids and provide a global data set that overcomes the mentioned problems. The approach is based on Miller-Miller scaling in the relaxed form by Warrick, that fits the parameters of the WRC through all sub-grid WRCs to provide an effective parameterization for the grid cell at model resolution; at the same time it preserves the information of sub-grid variability of the water retention curve by deriving local scaling parameters. Based on the Mualem-van Genuchten approach we also derive the unsaturated hydraulic conductivity from the water retention functions, thereby assuming that the local parameters are also valid for this function. In addition, via the Warrick scaling parameter λ, information on global sub-grid scaling variance is given that enables modellers to improve dynamical downscaling of (regional) climate models or to perturb hydraulic parameters for model ensemble output generation. The present analysis is based on the ROSETTA PTF

  20. A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves

    Directory of Open Access Journals (Sweden)

    C. Montzka

    2017-07-01

    Full Text Available Agroecosystem models, regional and global climate models, and numerical weather prediction models require adequate parameterization of soil hydraulic properties. These properties are fundamental for describing and predicting water and energy exchange processes at the transition zone between solid earth and atmosphere, and regulate evapotranspiration, infiltration and runoff generation. Hydraulic parameters describing the soil water retention (WRC and hydraulic conductivity (HCC curves are typically derived from soil texture via pedotransfer functions (PTFs. Resampling of those parameters for specific model grids is typically performed by different aggregation approaches such a spatial averaging and the use of dominant textural properties or soil classes. These aggregation approaches introduce uncertainty, bias and parameter inconsistencies throughout spatial scales due to nonlinear relationships between hydraulic parameters and soil texture. Therefore, we present a method to scale hydraulic parameters to individual model grids and provide a global data set that overcomes the mentioned problems. The approach is based on Miller–Miller scaling in the relaxed form by Warrick, that fits the parameters of the WRC through all sub-grid WRCs to provide an effective parameterization for the grid cell at model resolution; at the same time it preserves the information of sub-grid variability of the water retention curve by deriving local scaling parameters. Based on the Mualem–van Genuchten approach we also derive the unsaturated hydraulic conductivity from the water retention functions, thereby assuming that the local parameters are also valid for this function. In addition, via the Warrick scaling parameter λ, information on global sub-grid scaling variance is given that enables modellers to improve dynamical downscaling of (regional climate models or to perturb hydraulic parameters for model ensemble output generation. The present analysis is based

  1. Relationship between Tomm performance and PAI validity scales in a mixed clinical sample.

    Science.gov (United States)

    Whiteside, Douglas M; Dunbar-Mayer, Philip; Waters, Dana P

    2009-04-01

    This study addressed the relationship between Personality Assessment Inventory (PAI) validity indicators and cognitive effort measures on the Test of Memory Malingering (TOMM). Significant correlations were found between TOMM and some PAI validity scales. Factor analysis results found separate cognitive and personality components, but the Negative Impression Management (NIM) scale, a measure of response bias, had factor loadings on both the cognitive and the personality components. Follow-up hierarchical multiple regression and t-test analysis generally confirmed this result, and found that NIM and the Infrequency (INF) scale have significant relationships with the TOMM. The results indicate that individuals with elevations on the PAI's INF and NIM scales often display decreased cognitive effort on the TOMM. The current results support the hypothesis that personality assessment validity indicators have a modest but significant relationship with poor cognitive effort.

  2. Autonomous Operation of Hybrid Microgrid with AC and DC Sub-Grids

    DEFF Research Database (Denmark)

    Loh, Poh Chiang; Blaabjerg, Frede

    2011-01-01

    This paper investigates on the active and reactive power sharing of an autonomous hybrid microgrid. Unlike existing microgrids which are purely ac, the hybrid microgrid studied here comprises dc and ac sub-grids, interconnected by power electronic interfaces. The main challenge here is to manage...... the power flow among all the sources distributed throughout the two types of sub-grids, which certainly is tougher than previous efforts developed for only either ac or dc microgrid. This wider scope of control has not yet been investigated, and would certainly rely on the coordinated operation of dc...... sources, ac sources and interlinking converters. Suitable control and normalization schemes are therefore developed for controlling them with results presented for showing the overall performance of the hybrid microgrid....

  3. Examining the Variability of Sleep Patterns during Treatment for Chronic Insomnia: Application of a Location-Scale Mixed Model.

    Science.gov (United States)

    Ong, Jason C; Hedeker, Donald; Wyatt, James K; Manber, Rachel

    2016-06-15

    The purpose of this study was to introduce a novel statistical technique called the location-scale mixed model that can be used to analyze the mean level and intra-individual variability (IIV) using longitudinal sleep data. We applied the location-scale mixed model to examine changes from baseline in sleep efficiency on data collected from 54 participants with chronic insomnia who were randomized to an 8-week Mindfulness-Based Stress Reduction (MBSR; n = 19), an 8-week Mindfulness-Based Therapy for Insomnia (MBTI; n = 19), or an 8-week self-monitoring control (SM; n = 16). Sleep efficiency was derived from daily sleep diaries collected at baseline (days 1-7), early treatment (days 8-21), late treatment (days 22-63), and post week (days 64-70). The behavioral components (sleep restriction, stimulus control) were delivered during late treatment in MBTI. For MBSR and MBTI, the pre-to-post change in mean levels of sleep efficiency were significantly larger than the change in mean levels for the SM control, but the change in IIV was not significantly different. During early and late treatment, MBSR showed a larger increase in mean levels of sleep efficiency and a larger decrease in IIV relative to the SM control. At late treatment, MBTI had a larger increase in the mean level of sleep efficiency compared to SM, but the IIV was not significantly different. The location-scale mixed model provides a two-dimensional analysis on the mean and IIV using longitudinal sleep diary data with the potential to reveal insights into treatment mechanisms and outcomes. © 2016 American Academy of Sleep Medicine.

  4. Analysis of subgrid models of heat convection by symmetry group theory

    Science.gov (United States)

    Razafindralandy, Dina; Hamdouni, Aziz

    2007-04-01

    Symmetries, i.e. transformations which leave the set of the solutions of the Navier-Stokes equations unchanged, play an important role in turbulence (conservation laws, wall laws, …). They should not be destroyed by turbulence models. The symmetries of the heat convection equations are then presented, for a non-isothermal fluid. Next, common subgrid stress tensor and flux models are analyzed, using the symmetry approach. To cite this article: D. Razafindralandy, A. Hamdouni, C. R. Mecanique 335 (2007).

  5. Experimental approach for mixed-mode fatigue delamination crack growth with large-scale bridging in polymer composites

    DEFF Research Database (Denmark)

    Holmes, John W.; Liu, Liu; Sørensen, Bent F.

    2014-01-01

    of delaminations in a typical fibre-reinforced polymer composite was investigated under a constant cyclic loading amplitude. Pure mode I, mode II and mixed-mode crack growth conditions were examined. The results, analysed using a J-integral approach, show that the double cantilever beam loaded with uneven bending...... crack growth rate observed. In addition to details concerning the equipment, a general discussion of the development of cyclic bridging laws for delamination growth in the presence of large-scale bridging is provided....

  6. Multi-scaling mix and non-universality between population and facility density

    CERN Document Server

    Qian, J H; Han, D D; Ma, Y G; 10.1016/j.physa.2012.05.038

    2012-01-01

    The distribution of facilities is closely related to our social economic activities. Recent studies have reported a scaling relation between population and facility density with the exponent depending on the type of facility. In this paper, we show that generally this exponent is not universal for a specific type of facility. Instead by using Chinese data we find that it increases with Per Capital GDP. Thus our observed scaling law is actually a mixture of some multi-scaling relations. This result indicates that facilities may change their public or commercial attributes according to the outside environment. We argue that this phenomenon results from the unbalanced regional economic level and suggest a modification for previous model by introducing consuming capacity. The modified model reproduces most of our observed properties.

  7. Mixing and mass transfer in a pilot scale U-loop bioreactor.

    Science.gov (United States)

    Petersen, Leander A H; Villadsen, John; Jørgensen, Sten B; Gernaey, Krist V

    2017-02-01

    A system capable of handling a large volumetric gas fraction while providing a high gas to liquid mass transfer is a necessity if the metanotrophic bacterium Methylococcus capsulatus is to be used in single cell protein (SCP) production. In this study, mixing time and mass transfer coefficients were determined in a 0.15 m 3 forced flow U-loop fermenter of a novel construction. The effect on the impeller drawn power when a gas was introduced into the system was also studied. Mixing time decreased and mass transfer increased with increasing volumetric liquid flow rate and specific power input. This happened also for a large volume fraction of the gas, which was shown to have only minor effect on the power drawn from the pump impeller. Very large mass transfer coefficients, considerably higher than those obtainable in an STR and previous tubular loop reactors, could be achieved in the U-loop fermenter equipped with static mixers at modest volumetric liquid and gas flow rates. Biotechnol. Bioeng. 2017;114: 344-354. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. Numerical simulation of a plane turbulent mixing layer, with applications to isothermal, rapid reactions

    Science.gov (United States)

    Lin, P.; Pratt, D. T.

    1987-01-01

    A hybrid method has been developed for the numerical prediction of turbulent mixing in a spatially-developing, free shear layer. Most significantly, the computation incorporates the effects of large-scale structures, Schmidt number and Reynolds number on mixing, which have been overlooked in the past. In flow field prediction, large-eddy simulation was conducted by a modified 2-D vortex method with subgrid-scale modeling. The predicted mean velocities, shear layer growth rates, Reynolds stresses, and the RMS of longitudinal velocity fluctuations were found to be in good agreement with experiments, although the lateral velocity fluctuations were overpredicted. In scalar transport, the Monte Carlo method was extended to the simulation of the time-dependent pdf transport equation. For the first time, the mixing frequency in Curl's coalescence/dispersion model was estimated by using Broadwell and Breidenthal's theory of micromixing, which involves Schmidt number, Reynolds number and the local vorticity. Numerical tests were performed for a gaseous case and an aqueous case. Evidence that pure freestream fluids are entrained into the layer by large-scale motions was found in the predicted pdf. Mean concentration profiles were found to be insensitive to Schmidt number, while the unmixedness was higher for higher Schmidt number. Applications were made to mixing layers with isothermal, fast reactions. The predicted difference in product thickness of the two cases was in reasonable quantitative agreement with experimental measurements.

  9. Large-scale melting and impact mixing on early-formed asteroids

    DEFF Research Database (Denmark)

    Greenwood, Richard; Barrat, J.-A.; Scott, Edward Robert Dalton

    Large-scale melting of asteroids and planetesimals is now known to have taken place ex-tremely early in solar system history [1]. The first-generation bodies produced by this process would have been subject to rapid collisional reprocessing, leading in most cases to fragmentation and/or accretion...

  10. Mixing and flushing time scales in the Azhikode Estuary, southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Revichandran, C.; Pylee, A.

    Flushing time scales of the Azhikode Estuary, Kerala, India showed pronounced dry season and wet season signals as well as large inter-annual variation. Cumulative flushing time of the estuary varies from 4.8 tide cycles in April to 1.22 tide cycles...

  11. Developing and validating the Youth Conduct Problems Scale-Rwanda: a mixed methods approach.

    Directory of Open Access Journals (Sweden)

    Lauren C Ng

    Full Text Available This study developed and validated the Youth Conduct Problems Scale-Rwanda (YCPS-R. Qualitative free listing (n = 74 and key informant interviews (n = 47 identified local conduct problems, which were compared to existing standardized conduct problem scales and used to develop the YCPS-R. The YCPS-R was cognitive tested by 12 youth and caregiver participants, and assessed for test-retest and inter-rater reliability in a sample of 64 youth. Finally, a purposive sample of 389 youth and their caregivers were enrolled in a validity study. Validity was assessed by comparing YCPS-R scores to conduct disorder, which was diagnosed with the Mini International Neuropsychiatric Interview for Children, and functional impairment scores on the World Health Organization Disability Assessment Schedule Child Version. ROC analyses assessed the YCPS-R's ability to discriminate between youth with and without conduct disorder. Qualitative data identified a local presentation of youth conduct problems that did not match previously standardized measures. Therefore, the YCPS-R was developed solely from local conduct problems. Cognitive testing indicated that the YCPS-R was understandable and required little modification. The YCPS-R demonstrated good reliability, construct, criterion, and discriminant validity, and fair classification accuracy. The YCPS-R is a locally-derived measure of Rwandan youth conduct problems that demonstrated good psychometric properties and could be used for further research.

  12. Scaling properties of SU(2) gauge theory with mixed fundamental-adjoint action

    CERN Document Server

    Rinaldi, Enrico; Lucini, Biagio; Patella, Agostino; Rago, Antonio

    2012-01-01

    We study the phase diagram of the SU(2) lattice gauge theory with fundamental-adjoint Wilson plaquette action. We confirm the presence of a first order bulk phase transition and we estimate the location of its end-point in the bare parameter space. If this point is second order, the theory is one of the simplest realizations of a lattice gauge theory admitting a continuum limit at finite bare couplings. All the relevant gauge observables are monitored in the vicinity of the fixed point with very good control over finite-size effects. The scaling properties of the low-lying glueball spectrum are studied while approaching the end-point in a controlled manner.

  13. Planning of community-scale renewable energy management systems in a mixed stochastic and fuzzy environment

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Y.P.; Tan, Q. [Environmental Systems Engineering Program, Faculty of Engineering, Unversity of Regina, Regina, Saskatchewan (Canada); Huang, G.H. [Environmental Systems Engineering Program, Faculty of Engineering, Unversity of Regina, Regina, Saskatchewan (Canada)]|[Chinese Research Academy of Environmental Science, Beijing Normal University, Beijing 100012-100875 (China); Yang, Z.F. [State Key Laboratory of Water Environment Simulation, School of Enviroment, Beijing Normal University, Beijing 100875 (China)

    2009-07-15

    In this study, an interval-parameter superiority-inferiority-based two-stage programming model has been developed for supporting community-scale renewable energy management (ISITSP-CREM). This method is based on an integration of the existing interval linear programming (ILP), two-stage programming (TSP) and superiority-inferiority-based fuzzy-stochastic programming (SI-FSP). It allows uncertainties presented as both probability/possibilistic distributions and interval values to be incorporated within a general optimization framework, facilitating the reflection of multiple uncertainties and complexities during the process of renewable energy management systems planning. ISITSP-CREM can also be used for effectively addressing dynamic interrelationships between renewable energy availabilities, economic penalties and electricity-generation deficiencies within a community scale. Thus, complexities in renewable energy management systems can be systematically reflected, highly enhancing applicability of the modeling process. The developed method has then been applied to a case of long-term renewable energy management planning for three communities. Useful solutions for the planning of renewable energy management systems have been generated. Interval solutions associated with different energy availabilities and economic penalties have been obtained. They can be used for generating decision alternatives and thus help decision makers identify desired policies under various economic and system-reliability constraints. The generated solutions can also provide desired energy resource/service allocation plans with a minimized system cost (or economic penalties), a maximized system reliability level and a maximized energy security. Tradeoffs between system costs and energy security can also be tackled. Higher costs will increase potential energy generation amount, while a desire for lower system costs will run into a risk of energy deficiency. They are helpful for supporting

  14. Mixed-effects modelling of the interspecies pharmacokinetic scaling of pegylated human erythropoietin.

    Science.gov (United States)

    Jolling, Koen; Perez Ruixo, Juan Jose; Hemeryck, Alex; Vermeulen, An; Greway, Tony

    2005-04-01

    The aim of this study was to develop a population pharmacokinetic model for interspecies allometric scaling of pegylated r-HuEPO (PEG-EPO) pharmacokinetics to man. A total of 927 serum concentrations from 193 rats, 6 rabbits, 34 monkeys, and 9 dogs obtained after a single dose of PEG-EPO, administered by the i.v. (dose range: 12.5-550 microg/kg) and s.c. (dose range: 12.5-500 microg/kg) routes, were pooled in this analysis. An open two-compartment model with first-order absorption and lag time (Tlag) and linear elimination from the central compartment was fitted to the data using the NONMEM V software. Body weight (WT) was used as a scaling factor and the effect of brain weight (BW), sex, and pregnancy status on the pharmacokinetic parameters was investigated. The final model was evaluated by means of a non-parametric bootstrap analysis and used to predict the PEG-EPO pharmacokinetic parameters in healthy male subjects. The systemic clearance (CL) in males was estimated to be 4.08WT1.030xBW-0.345 ml/h. In females, the CL was 90.7% of the CL in males. The volumes of the central (Vc) and the peripheral (Vp) compartment were characterized as 57.8WT0.959 ml, and 48.1WT1.150 ml, respectively. Intercompartmental flow was estimated at 2.32WT0.930 ml/h. Absorption rate constant (Ka) was estimated at 0.0538WT-0.149. The absolute s.c. bioavailability F was calculated at 52.5, 80.2, and 49.4% in rat, monkey, and dog, respectively. The interindividual variability in the population pharmacokinetic parameters was fairly low (parametric bootstrap confirmed the accuracy of the NONMEM estimates. The mean model predicted pharmacokinetic parameters in healthy male subjects of 70 kg were estimated at: CL: 26.2 ml/h; Vc: 3.6l; Q: 286 l/h; Vp: 6.9l, and Ka: 0.031 h-1. The population pharmacokinetic model developed was appropriate to describe the time course of PEG-EPO serum concentrations and their variability in different species. The model predicted pharmacokinetics of PEG-EPO in

  15. Numerical Dissipation and Subgrid Scale Modeling for Separated Flows at Moderate Reynolds Numbers

    Science.gov (United States)

    Cadieux, Francois; Domaradzki, Julian Andrzej

    2014-11-01

    Flows in rotating machinery, for unmanned and micro aerial vehicles, wind turbines, and propellers consist of different flow regimes. First, a laminar boundary layer is followed by a laminar separation bubble with a shear layer on top of it that experiences transition to turbulence. The separated turbulent flow then reattaches and evolves downstream from a nonequilibrium turbulent boundary layer to an equilibrium one. In previous work, the capability of LES to reduce the resolution requirements down to 1 % of DNS resolution for such flows was demonstrated (Cadieux et al., JFE 136-6). However, under-resolved DNS agreed better with the benchmark DNS than simulations with explicit SGS modeling because numerical dissipation and filtering alone acted as a surrogate SGS dissipation. In the present work numerical viscosity is quantified using a new method proposed recently by Schranner et al. and its effects are analyzed and compared to turbulent eddy viscosities of explicit SGS models. The effect of different SGS models on a simulation of the same flow using a non-dissipative code is also explored. Supported by NSF.

  16. Accounting for subgrid scale topographic variations in flood propagation modeling using MODFLOW

    DEFF Research Database (Denmark)

    Milzow, Christian; Kinzelbach, W.

    2010-01-01

    To be computationally viable, grid-based spatially distributed hydrological models of large wetlands or floodplains must be set up using relatively large cells (order of hundreds of meters to kilometers). Computational costs are especially high when considering the numerous model runs or model time...

  17. On the Effect of an Anisotropy-Resolving Subgrid-Scale Model on Turbulent Vortex Motions

    Science.gov (United States)

    2014-09-19

    expression coincides with the modified Leonard stress proposed by Ger- mano et al. (1991). In this model, the SGS turbulence energy kSGS may be evaluated as... mano subgridscale closure method. Phys. Fluids A, Vol. 4, pp. 633-635. Morinishi, Y. and Vasilyev, O.V. (2001), A recommended modification to the

  18. Final Report: Systematic Development of a Subgrid Scaling Framework to Improve Land Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dickinson, Robert Earl [Univ. of Texas, Austin, TX (United States)

    2016-07-11

    We carried out research to development improvements of the land component of climate models and to understand the role of land in climate variability and change. A highlight was the development of a 3D canopy radiation model. More than a dozen publications resulted.

  19. Small-scale spatial variability of soil microbial community composition and functional diversity in a mixed forest

    Science.gov (United States)

    Wang, Qiufeng; Tian, Jing; Yu, Guirui

    2014-05-01

    Patterns in the spatial distribution of organisms provide important information about mechanisms that regulate the diversity and complexity of soil ecosystems. Therefore, information on spatial distribution of microbial community composition and functional diversity is urgently necessary. The spatial variability on a 26×36 m plot and vertical distribution (0-10 cm and 10-20 cm) of soil microbial community composition and functional diversity were studied in a natural broad-leaved Korean pine (Pinus koraiensis) mixed forest soil in Changbai Mountain. The phospholipid fatty acid (PLFA) pattern was used to characterize the soil microbial community composition and was compared with the community substrate utilization pattern using Biolog. Bacterial biomass dominated and showed higher variability than fungal biomass at all scales examined. The microbial biomass decreased with soil depths increased and showed less variability in lower 10-20 cm soil layer. The Shannon-Weaver index value for microbial functional diversity showed higher variability in upper 0-10 cm than lower 10-20 cm soil layer. Carbohydrates, carboxylic acids, polymers and amino acids are the main carbon sources possessing higher utilization efficiency or utilization intensity. At the same time, the four carbon source types contributed to the differentiation of soil microbial communities. This study suggests the higher diversity and complexity for this mix forest ecosystem. To determine the driving factors that affect this spatial variability of microorganism is the next step for our study.

  20. Culture scale-up and immobilisation of a mixed methanotrophic consortium for methane remediation in pilot-scale bio-filters.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Saravanan, Nadarajan; Cirés, Samuel; Alvarez-Roa, Carlos; Razaghi, Ali; Chidambarampadmavathy, Karthigeyan; Velu, Chinnathambi; Subashchandrabose, Gobalakrishnan; Heimann, Kirsten

    2017-02-01

    Robust methanotrophic consortia for methane (CH4) remediation and by-product development are presently not readily available for industrial use. In this study, a mixed methanotrophic consortium (MMC), sequentially enriched from a marine sediment, was assessed for CH4 removal efficiency and potential biomass-generated by-product development. Suitable packing material for bio-filters to support MMC biofilm establishment and growth was also evaluated. The enriched MMC removed ∼7-13% CH4 under a very high gas flow rate (2.5 L min-1; 20-25% CH4) in continuous-stirred tank reactors (∼10 L working volume) and the biomass contained long-chain fatty acids (i.e. C16 and C18). Cultivation of the MMC on plastic bio-balls abated ∼95-97% CH4 in pilot-scale non-sterile outdoor-operated bio-filters (0.1 L min-1; 1% CH4). Contamination by cyanobacteria had beneficial effects on treating low-level CH4, by providing additional oxygen for methane oxidation by MMC, suggesting that the co-cultivation of MMC with cyanobacterial mats does not interfere with and may actually be beneficial for remediation of CH4 and CO2 at industrial scale.

  1. Scaling wind stirring effects in an oceanic bulk mixed layer model with application to an OGCM of the tropical Pacific

    Science.gov (United States)

    Zhu, Yuchao; Zhang, Rong-Hua

    2017-11-01

    The mixed layer depth (MLD) plays an important role in the climate system through its influences on sea surface temperature (SST). The Kraus-Turner-Niiler (hereafter referred to as KTN) bulk mixed layer (ML) model is designed for describing the MLD and has been adopted widely by many ocean modeling. However, large biases exist in the MLD simulation using the original KTN model in the tropical Pacific. This is partly due to the uncertainties in representing wind stirring effect in the model, which is scaled by a parameter (m 0). Traditionally, m 0 is taken as a constant uniformly in space. In this study, the m 0 is estimated as spatially and seasonally varying through its inverse calculation from a balance equation describing the turbulent kinetic energy (TKE) budget of the ML. It is illustrated that the m 0 is spatially varying over the tropical Pacific. The derived m 0 fields are then embedded into an ocean general circulation model (OGCM). Compared with the observations and the global ocean data assimilation system (GODAS) analyses, the MLD simulations in the OGCM with varying m 0 are substantially improved in the tropical Pacific Ocean on seasonal and interannual time scales. Additionally, the Pacific subtropical cells (STCs) become intensified, accompanied with the strengthening of upwelling in the eastern equatorial Pacific; thus, more realistic simulations are obtained in spatially and seasonally varying m 0 case compared with the constant m 0 case. As the related cooling effect from the upwelling is enhanced, the simulated SST is slightly cooled down in the eastern equatorial Pacific. Further applications and implications are also discussed.

  2. Bench-scale arc melter for R&D in thermal treatment of mixed wastes

    Energy Technology Data Exchange (ETDEWEB)

    Kong, P.C.; Grandy, J.D.; Watkins, A.D.; Eddy, T.L.; Anderson, G.L.

    1993-05-01

    A small dc arc melter was designed and constructed to run bench-scale investigations on various aspects of development for high-temperature (1,500-1,800{degrees}C) processing of simulated transuranic-contaminated waste and soil located at the Radioactive Waste Management Complex (RWMC). Several recent system design and treatment studies have shown that high-temperature melting is the preferred treatment. The small arc melter is needed to establish techniques and procedures (with surrogates) prior to using a similar melter with the transuranic-contaminated wastes in appropriate facilities at the site. This report documents the design and construction, starting and heating procedures, and tests evaluating the melter`s ability to process several waste types stored at the RWMC. It is found that a thin graphite strip provides reliable starting with initial high current capability for partially melting the soil/waste mixture. The heating procedure includes (1) the initial high current-low voltage mode, (2) a low current-high voltage mode that commences after some slag has formed and arcing dominates over the receding graphite conduction path, and (3) a predominantly Joule heating mode during which the current can be increased within the limits to maintain relatively quiescent operation. Several experiments involving the melting of simulated wastes are discussed. Energy balance, slag temperature, and electrode wear measurements are presented. Recommendations for further refinements to enhance its processing capabilities are identified. Future studies anticipated with the arc melter include waste form processing development; dissolution, retention, volatilization, and collection for transuranic and low-level radionuclides, as well as high vapor pressure metals; electrode material development to minimize corrosion and erosion; refractory corrosion and/or skull formation effects; crucible or melter geometry; metal oxidation; and melt reduction/oxidation (redox) conditions.

  3. Large-scale flow structures and heat transport of turbulent forced and mixed convection in a closed rectangular cavity

    Energy Technology Data Exchange (ETDEWEB)

    Schmeling, D., E-mail: Daniel.Schmeling@dlr.de [German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstrasse 10, D-37073 Goettingen (Germany); Westhoff, A.; Kuehn, M.; Bosbach, J.; Wagner, C. [German Aerospace Center (DLR), Institute of Aerodynamics and Flow Technology, Bunsenstrasse 10, D-37073 Goettingen (Germany)

    2011-10-15

    Highlights: > Superposition of forced and thermal convection is studied in a rectangular cavity. > For pure forced convection the mean wind exhibits a solid body rotation. > Four buoyancy induced convection rolls are formed for mixed convection at Ar {approx} 3.3. > The enthalpy flux difference between out- and inflowing air has a maximum at Ar {approx} 0.6. - Abstract: Results of an experimental study of flow structure formation and heat transport in turbulent forced and mixed convection are presented. The experiments were conducted in a rectangular cavity with a square cross section, which has an aspect ratio between length and height of {Gamma}{sub xz} = 5. Air at atmospheric pressure was used as working fluid. The air inflow was supplied through a slot below the ceiling, while exhausting was provided by another slot, which is located directly above the floor. Both vents extend over the whole length of the cell. In order to induce thermal convection the bottom of the cell is heated while the ceiling is maintained at a constant temperature. This configuration allows to generate and study mixed convection under well defined conditions. Results of forced convection at Re = 1.07 x 10{sup 4} as well as mixed convection at 1.01 x 10{sup 4} {<=} Re {<=} 3.4 x 10{sup 4} and Ra = 2.4 x 10{sup 8} (3.3 {>=} Ar {>=} 0.3), which were obtained by means of Particle Image Velocimetry and local temperature measurements, are presented. For purely forced convection a 2D mean wind, which can be approximated by a solid body rotation, is found. With increasing Archimedes number this structure becomes unstable, leading to a transition of the solid body rotation into additional smaller convection rolls. Proper orthogonal decomposition of the instantaneous velocity fields has been performed for further analysis of these coherent large-scale structures. Their fingerprint is found in the spatial temperature distribution of the out flowing air at the end of the outlet channel, which

  4. Evaluation of a Sub-Grid Topographic Drag Parameterizations for Modeling Surface Wind Speed During Storms Over Complex Terrain in the Northeast U.S.

    Science.gov (United States)

    Frediani, M. E.; Hacker, J.; Anagnostou, E. N.; Hopson, T. M.

    2015-12-01

    This study aims at improving regional simulation of 10-meter wind speed by verifying PBL schemes for storms at different scales, including convective storms, blizzards, tropical storms and nor'easters over complex terrain in the northeast U.S. We verify a recently proposed sub-grid topographic drag scheme in stormy conditions and compare it with two PBL schemes (Mellor-Yamada and Yonsei University) from WRF-ARW over a region in the Northeast U.S. The scheme was designed to adjust the surface drag over regions with high subgrid-scale topographic variability. The schemes are compared using spatial, temporal, and pattern criteria against surface observations. The spatial and temporal criteria are defined by season, diurnal cycle, and topography; the pattern, is based on clusters derived using clustering analysis. Results show that the drag scheme reduces the positive bias of low wind speeds, but over-corrects the high wind speeds producing a magnitude-increasing negative bias with increasing speed. Both other schemes underestimate the most frequent low-speed mode and overestimate the high-speeds. Error characteristics of all schemes respond to seasonal and diurnal cycle changes. The Topo-wind experiment shows the best agreement with the observation quantiles in summer and fall, the best representation of the diurnal cycle in these seasons, and reduces the bias of all surface stations near the coast. In more stable conditions the Topo-wind scheme shows a larger negative bias. The cluster analysis reveals a correlation between bias and mean speed from the Mellor-Yamada and Yonsei University schemes that is not present when the drag scheme is used. When the drag scheme is used the bias correlates with wind direction; the bias increases when the meridional wind component is negative. This pattern corresponds to trajectories with more land interaction with the highest biases found in northwest circulation clusters.

  5. Mixed-effects modelling of scale growth profiles predicts the occurrence of early and late fish migrants.

    Directory of Open Access Journals (Sweden)

    Francisco Marco-Rius

    Full Text Available Fish growth is commonly used as a proxy for fitness but this is only valid if individual growth variation can be interpreted in relation to conspecifics' performance. Unfortunately, assessing individual variation in growth rates is problematic under natural conditions because subjects typically need to be marked, repeated measurements of body size are difficult to obtain in the field, and recaptures may be limited to a few time events which will generally vary among individuals. The analysis of consecutive growth rings (circuli found on scales and other hard structures offers an alternative to mark and recapture for examining individual growth variation in fish and other aquatic vertebrates where growth rings can be visualized, but accounting for autocorrelations and seasonal growth stanzas has proved challenging. Here we show how mixed-effects modelling of scale growth increments (inter-circuli spacing can be used to reconstruct the growth trajectories of sea trout (Salmo trutta and correctly classify 89% of individuals into early or late seaward migrants (smolts. Early migrants grew faster than late migrants during their first year of life in freshwater in two natural populations, suggesting that migration into the sea was triggered by ontogenetic (intrinsic drivers, rather than by competition with conspecifics. Our study highlights the profound effects that early growth can have on age at migration of a paradigmatic fish migrant and illustrates how the analysis of inter-circuli spacing can be used to reconstruct the detailed growth of individuals when these cannot be marked or are only caught once.

  6. Auto-thermal reforming using mixed ion-electronic conducting ceramic membranes for a small-scale H₂ production plant.

    Science.gov (United States)

    Spallina, Vincenzo; Melchiori, Tommaso; Gallucci, Fausto; van Sint Annaland, Martin

    2015-03-18

    The integration of mixed ionic electronic conducting (MIEC) membranes for air separation in a small-to-medium scale unit for H2 production (in the range of 650-850 Nm3/h) via auto-thermal reforming of methane has been investigated in the present study. Membranes based on mixed ionic electronic conducting oxides such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) give sufficiently high oxygen fluxes at temperatures above 800 °C with high purity (higher than 99%). Experimental results of membrane permeation tests are presented and used for the reactor design with a detailed reactor model. The assessment of the H2 plant has been carried out for different operating conditions and reactor geometry and an energy analysis has been carried out with the flowsheeting software Aspen Plus, including also the turbomachines required for a proper thermal integration. A micro-gas turbine is integrated in the system in order to supply part of the electricity required in the system. The analysis of the system shows that the reforming efficiency is in the range of 62%-70% in the case where the temperature at the auto-thermal reforming membrane reactor (ATR-MR) is equal to 900 °C. When the electric consumption and the thermal export are included the efficiency of the plant approaches 74%-78%. The design of the reactor has been carried out using a reactor model linked to the Aspen flowsheet and the results show that with a larger reactor volume the performance of the system can be improved, especially because of the reduced electric consumption. From this analysis it has been found that for a production of about 790 Nm3/h pure H2, a reactor with a diameter of 1 m and length of 1.8 m with about 1500 membranes of 2 cm diameter is required.

  7. Destruction of hazardous and mixed wastes using mediated electrochemical oxidation in a Ag(II)HNO3 bench scale system

    Energy Technology Data Exchange (ETDEWEB)

    Balazs, B.; Chiba, Z.; Hsu, P.; Lewis, P.; Murguia, L.; Adamson, M.

    1997-02-01

    Mediated Electrochemical Oxidation (MEO) is a promising technology for the destruction of organic containing wastes and the remediation of mixed wastes containing transuranic components. The combination of a powerful oxidant and an acid solution allows the conversion of nearly all organics, whether present in hazardous or in mixed waste, to carbon dioxide. Insoluble transuranics are dissolved in this process and may be recovered by separation and precipitation. The oxidant, or mediator, is a multivalent transition metal ion which is cleanly recycled in a number of charge transfer steps in an electrochemical cell. The MEO technique offers several advantages which are inherent in the system. First, the oxidation/dissolution processes are accomplished at near ambient pressures and temperatures (30-70{degrees}C). Second, all waste stream components and oxidation products (with the exception of evolved gases) are contained in an aqueous environment. This electrolyte acts as an accumulator for inorganics which were present in the original waste stream, and the large volume of electrolyte provides a thermal buffer for the energy released during oxidation of the organics. Third, the generation of secondary waste is minimal, as the process needs no additional reagents. Finally, the entire process can be shut down by simply turning off the power, affording a level of control unavailable in some other techniques. Although the oxidation of organics and the dissolution of transuranics by higher valency metal ions has been known for some time, applying the MEO technology to waste treatment is a relatively recent development. Numerous groups, both in the United States and Europe, have made substantial progress in the last decade towards understanding the mechanistic pathways, kinetics, and engineering aspects of the process. At Lawrence Livermore National Laboratory, substantial contributions have been made to this knowledge base in these areas and others. Conceptual design and

  8. Representation and evaluation of aerosol mixing state in a climate model

    Science.gov (United States)

    Bauer, S. E.; Prather, K. A.; Ault, A. P.

    2011-12-01

    Aerosol particles in the atmosphere are composed out of multiple chemical species. The aerosol mixing state is an important aerosol property that will determine the interaction of aerosols with the climate system via radiative forcings and cloud activation. Through the introduction of aerosol microphysics into climate models, aerosol mixing state is by now taken into account to a certain extend in climate models, and evaluation of mixing state is the next challenge. Here we use data from the Aerosol Time of Flight Mass Spectrometer (ATOFMS) and compare the results to the GISS-modelE-MATRIX model, a global climate model including a detailed aerosol micro-physical scheme. We use data from various field campaigns probing, urban, rural and maritime air masses and compare those to climatological and nudged simulations for the years 2005 to 2009. ATOFMS provides information about the size distributions of several mixing state classes, including the chemical components of black and organic carbon, sulfates, dust and salts. MATRIX simulates 16 aerosol populations, which definitions are based on mixing state. We have grouped ATOFMS and MATRIX data into similar mixing state classes and compare the size resolved number concentrations against each other. As a first result we find that climatological simulations are rather difficult to evaluate with field data, and that nudged simulations give a much better agreement. However this is not just caused by the better fit of natural - meteorological driven - aerosol components, but also due to the interaction between meteorology and aerosol formation. The model seems to get the right amount of mixing state of black carbon material with sulfate and organic components, but seems to always overestimate the fraction of black carbon that is externally mixed. In order to understand this bias between model and the ATOFMS data, we will look into microphysical processes near emission sources and investigate the climate relevance of these sub-grid

  9. Reasons for Marijuana and Tobacco Co-use Among Young Adults: A Mixed Methods Scale Development Study.

    Science.gov (United States)

    Berg, Carla J; Payne, Jackelyn; Henriksen, Lisa; Cavazos-Rehg, Patricia; Getachew, Betelihem; Schauer, Gillian L; Haardörfer, Regine

    2017-08-09

    Marijuana-tobacco co-use has increased recently, particularly in young adults. We conducted a mixed-methods study to: (1) examine reasons for co-use; and (2) develop a scale assessing reasons for co-use among participants in a longitudinal cohort study of 3,418 students aged 18-25 from 7 Georgia colleges and universities. Phone-based semi-structured interviews were conducted in Summer 2015 among 46 current (past 30-day, n = 26) or lifetime (n = 20) marijuana users. Subsequently, scale items were developed and included at Wave 3. Participants reporting past 4-month tobacco and marijuana use (n = 328) completed the Reasons for Marijuana-Tobacco Co-use section. Per qualitative data, reasons for marijuana-tobacco co-use included synergistic effects, one triggering or preceding the other's use, using one to reduce the other's use, co-administration, social context, and experimentation. The survey subsample included 37.1% who used cigarettes, 30.4% LCCs, 9.4% smokeless, 23.7% e-cigarettes, and 30.4% hookah. Four subscale factors emerged: (1) Instrumentality, indicating synergistic effects; (2) Displacement, indicating using one product to reduce/quit the other; (3) Social context, indicating use in different settings/social situations; and (4) Experimentation, indicating experimentation with both but no specific reasons for co-use. These subscales demonstrated distinct associations with tobacco type used; nicotine dependence; marijuana and alcohol use frequency; tobacco and marijuana use motives, respectively; perceptions of tobacco and marijuana; and parental and friend use. Including these subscales in regressions predicting nicotine dependence and days of marijuana use significantly contributed to each model. These findings might inform theoretical frameworks upon which marijuana-tobacco co-use occurs and direct future intervention studies.

  10. Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

    Directory of Open Access Journals (Sweden)

    A. John Blacker

    2015-12-01

    Full Text Available The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72–100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates.

  11. Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors.

    Science.gov (United States)

    Blacker, A John; Jolley, Katherine E

    2015-01-01

    The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72-100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates.

  12. Modelling sub-grid wetland in the ORCHIDEE global land surface model: evaluation against river discharges and remotely sensed data

    Directory of Open Access Journals (Sweden)

    B. Ringeval

    2012-07-01

    Full Text Available The quality of the global hydrological simulations performed by land surface models (LSMs strongly depends on processes that occur at unresolved spatial scales. Approaches such as TOPMODEL have been developed, which allow soil moisture redistribution within each grid-cell, based upon sub-grid scale topography. Moreover, the coupling between TOPMODEL and a LSM appears as a potential way to simulate wetland extent dynamic and its sensitivity to climate, a recently identified research problem for biogeochemical modelling, including methane emissions. Global evaluation of the coupling between TOPMODEL and an LSM is difficult, and prior attempts have been indirect, based on the evaluation of the simulated river flow. This study presents a new way to evaluate this coupling, within the ORCHIDEE LSM, using remote sensing data of inundated areas. Because of differences in nature between the satellite derived information – inundation extent – and the variable diagnosed by TOPMODEL/ORCHIDEE – area at maximum soil water content, the evaluation focuses on the spatial distribution of these two quantities as well as on their temporal variation. Despite some difficulties in exactly matching observed localized inundated events, we obtain a rather good agreement in the distribution of these two quantities at a global scale. Floodplains are not accounted for in the model, and this is a major limitation. The difficulty of reproducing the year-to-year variability of the observed inundated area (for instance, the decreasing trend by the end of 90s is also underlined. Classical indirect evaluation based on comparison between simulated and observed river flow is also performed and underlines difficulties to simulate river flow after coupling with TOPMODEL. The relationship between inundation and river flow at the basin scale in the model is analyzed, using both methods (evaluation against remote sensing data and river flow. Finally, we discuss the potential of

  13. On the path of plumes of the Río De La Plata Estuary main tributaries and their mixing scales

    Directory of Open Access Journals (Sweden)

    Claudia G Simionato

    2009-12-01

    Full Text Available With a length of 300 km and a width that narrows from 220 km at its mouth to 40 km at its upper end, the Río de la Plata is one of the largest estuaries of the world. Its three main tributaries -contributing to a total mean runoff of 22,000 m³ s-1- have different properties and are object of diverse environmental impact due to dissimilar development conditions on their shores. The knowledge of the paths of the plumes of those tributaries along the estuary and their mixing scales is necessary for management purposes. In this paper, advection-diffusion equations for passive tracers are coupled to the three-dimensional Hamburg Shelf Ocean Model and validated by means of a case study. Then, simulations in which each tributary is characterized by a different dye tracer are done for scenarios resulting of the combination of diverse characteristic atmospheric forcing and runoff conditions. The impact of bathymetry and Earth's rotation on plumes paths and mixing is also evaluated. Results indicate that, for mean to low discharge conditions, the path of the waters of the tributaries is in the form of two main plumes. The different water speeds of both tributaries, the presence of a bend immediately after their confluence and the varying geometry and bathymetry of the estuary favor a rapid mixing between the Uruguay and Paraná Guazú-Bravo waters, which then flow along the northern portion of the upper estuary channel. The Paraná de las Palmas waters, instead, occupy the southern shallow region of Playa Honda in the upper estuary and then flow following the southern coast. Downstream Colonia, at the intermediate estuary, the occurrence of another large bend and a change in bathymetric features force the flow to concentrate in the central part of the estuary and favor further mixing between the plumes. For high discharge conditions the northern part of the upper estuary is divided into two regions, one with a larger concentration of Uruguay waters

  14. Modeling mood variation and covariation among adolescent smokers: application of a bivariate location-scale mixed-effects model.

    Science.gov (United States)

    Pugach, Oksana; Hedeker, Donald; Richmond, Melanie J; Sokolovsky, Alexander; Mermelstein, Robin

    2014-05-01

    Ecological momentary assessments (EMAs) are useful for understanding both between- and within-subject dynamic changes in smoking and mood. Modeling 2 moods (positive affect [PA] and negative affect [NA], PA and NA) simultaneously will better enable researchers to explore the association between mood variables and what influences them at both the momentary and subject level. The EMA component of a natural history study of adolescent smoking was analyzed with a bivariate location-scale mixed-effects model. The proposed model separately estimates the between- and within-subject variances and jointly models the 2 mood constructs. A total of 461 adolescents completed the baseline EMA wave, which resulted in 14,105 random prompts. Smoking level, represented by the number of smoking events on EMA, entered the model as 2 predictors: one that compared nonsmokers during the EMA week to 1-cigarette smokers, and the second one that estimated the effect of smoking level on mood among smokers. Results suggest that nonsmokers had more consistent positive and negative moods compared to 1-cigarette smokers. Among those who smoked, both moods were more consistent at higher smoking levels. The effects of smoking level were greater for NA than for PA. The within-subject association between mood constructs was negative and strongest among 1-cigarette smokers; the within-subject association between positive and negative moods was negatively associated with smoking. Mood variation and association between mood constructs varied across smoking levels. The most infrequent smokers were characterized with more inconsistent moods, whereas mood was more consistent for subjects with higher smoking levels.

  15. Anaerobic digester foaming in full-scale cylindrical digesters--effects of organic loading rate, feed characteristics, and mixing.

    Science.gov (United States)

    Subramanian, Bhargavi; Pagilla, Krishna R

    2014-05-01

    Cylindrical anaerobic digesters (AD) were investigated to determine the causes and contributors of AD foaming due to the following: organic loading rate (OLR) and mixing effects, waste activated sludge (WAS) storage effects and foam suppression mixing at the surface of AD, and the effects of primary sludge (PS) solids fraction in the feed sludge. No foaming was observed over the duration of the study, indicating absence of a primary foaming cause even though the suspected contributors to AD foaming were present. Total solids and temperature profiles showed that reducing mixing frequency did not significantly impact digester performance or the homogeneity of the digester contents. The results showed that high organic loading rates, reduced mixing, and feed sludge storage by themselves do not cause foaming in most ADs when the primary foaming cause is absent. Reduced mixing and surface sludge sprays are practical strategies to control AD foaming. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Numerical Simulation of Atmospheric Boundary Layer Flow Over Battlefield-scale Complex Terrain: Surface Fluxes From Resolved and Subgrid Scales

    Science.gov (United States)

    2015-07-06

    Grimmond, 2015: Proc. 9th International Conference on Urban Climate , Paris, France. Anderson W, Li Q, Bou-Zeid E, 2014: Proc. of American...represen- tative information is known about the macroscale attributes of these coher- ent motions, we have developed a sim- ple, semi -empirical model to...dust from arid landscapes on the Llano Estacado in west Texas and eastern New Mexico. • Under Review: National Science Foundation, Fluid Dynamics Program

  17. A variational multi-scale method with spectral approximation of the sub-scales: Application to the 1D advection-diffusion equations

    KAUST Repository

    Chacón Rebollo, Tomás

    2015-03-01

    This paper introduces a variational multi-scale method where the sub-grid scales are computed by spectral approximations. It is based upon an extension of the spectral theorem to non necessarily self-adjoint elliptic operators that have an associated base of eigenfunctions which are orthonormal in weighted L2 spaces. This allows to element-wise calculate the sub-grid scales by means of the associated spectral expansion. We propose a feasible VMS-spectral method by truncation of this spectral expansion to a finite number of modes. We apply this general framework to the convection-diffusion equation, by analytically computing the family of eigenfunctions. We perform a convergence and error analysis. We also present some numerical tests that show the stability of the method for an odd number of spectral modes, and an improvement of accuracy in the large resolved scales, due to the adding of the sub-grid spectral scales.

  18. Simultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy

    Science.gov (United States)

    Ciricosta, O.; Scott, H.; Durey, P.; Hammel, B. A.; Epstein, R.; Preston, T. R.; Regan, S. P.; Vinko, S. M.; Woolsey, N. C.; Wark, J. S.

    2017-11-01

    In a National Ignition Facility implosion, hydrodynamic instabilities may cause the cold material from the imploding shell to be injected into the hot-spot (hot-spot mix), enhancing the radiative and conductive losses, which in turn may lead to a quenching of the ignition process. The bound-bound features of the spectrum emitted by high-Z ablator dopants that get mixed into the hot-spot have been previously used to infer the total amount of mixed mass; however, the typical errorbars are larger than the maximum tolerable mix. We present here an improved 2D model for mix spectroscopy which can be used to retrieve information on both the amount of mixed mass and the full imploded plasma profile. By performing radiation transfer and simultaneously fitting all of the features exhibited by the spectra, we are able to constrain self-consistently the effect of the opacity of the external layers of the target on the emission, thus improving the accuracy of the inferred mixed mass. The model's predictive capabilities are first validated by fitting simulated spectra arising from fully characterized hydrodynamic simulations, and then, the model is applied to previously published experimental results, providing values of mix mass in agreement with previous estimates. We show that the new self consistent procedure leads to better constrained estimates of mix and also provides insight into the sensitivity of the hot-spot spectroscopy to the spatial properties of the imploded capsule, such as the in-flight aspect ratio of the cold fuel surrounding the hotspot.

  19. A Hybrid Numerical Method for Turbulent Mixing Layers. Degree awarded by Case Western Reserve Univ.

    Science.gov (United States)

    Georgiadis, Nicholas J.

    2001-01-01

    A hybrid method has been developed for simulations of compressible turbulent mixing layers. Such mixing layers dominate the flows in exhaust systems of modern day aircraft and also those of hypersonic vehicles currently under development. The method configurations in which a dominant structural feature provides an unsteady mechanism to drive the turbulent development in the mixing layer. The hybrid method uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall bounded regions entering a mixing section, and a Large Eddy Simulation (LES) procedure to calculate the mixing dominated regions. A numerical technique was developed to enable the use of the hybrid RANS-LES method on stretched, non-Cartesian grids. Closure for the RANS equations was obtained using the Cebeci-Smith algebraic turbulence model in conjunction with the wall-function approach of Ota and Goldberg. The wall-function approach enabled a continuous computational grid from the RANS regions to the LES region. The LES equations were closed using the Smagorinsky subgrid scale model. The hybrid RANS-LES method is applied to a benchmark compressible mixing layer experiment. Preliminary two dimensional calculations are used to investigate the effects of axial grid density and boundary conditions. Vortex shedding from the base region of a splitter plate separating the upstream flows was observed to eventually transition to turbulence. The location of the transition, however, was much further downstream than indicated by experiments. Actual LES calculations, performed in three spatial directions, also indicated vortex shedding, but the transition to turbulence was found to occur much closer to the beginning of the mixing section. which is in agreement with experimental observations. These calculations demonstrated that LES simulations must be performed in three dimensions. Comparisons of time-averaged axial velocities and turbulence intensities indicated reasonable agreement with experimental

  20. Using Cosmic-Ray Neutron Probes to Monitor Landscape Scale Soil Water Content in Mixed Land Use Agricultural Systems

    National Research Council Canada - National Science Library

    Franz, Trenton E; Wahbi, Ammar; Vreugdenhil, Mariette; Weltin, Georg; Heng, Lee; Oismueller, Markus; Strauss, Peter; Dercon, Gerd; Desilets, Darin

    2016-01-01

    .... In this work, we explore the use of the newly established Cosmic-Ray Neutron Probe (CRNP) and method to monitor landscape average SWC in a mixed agricultural land use system in northeast Austria...

  1. Informing the scale-up of Kenya’s nursing workforce: a mixed methods study of factors affecting pre-service training capacity and production

    OpenAIRE

    Appiagyei, Ashley A; Kiriinya, Rose N; Gross, Jessica M; Wambua, David N; Oywer, Elizabeth O; Kamenju, Andrew K; Higgins, Melinda K; Riley, Patricia L; Rogers, Martha F

    2014-01-01

    Background Given the global nursing shortage and investments to scale-up the workforce, this study evaluated trends in annual student nurse enrolment, pre-service attrition between enrolment and registration, and factors that influence nurse production in Kenya. Methods This study used a mixed methods approach with data from the Regulatory Human Resources Information System (tracks initial student enrolment through registration) and the Kenya Health Workforce Information System (tracks deploy...

  2. Mixed Single/Double Precision in OpenIFS: A Detailed Study of Energy Savings, Scaling Effects, Architectural Effects, and Compilation Effects

    Science.gov (United States)

    Fagan, Mike; Dueben, Peter; Palem, Krishna; Carver, Glenn; Chantry, Matthew; Palmer, Tim; Schlacter, Jeremy

    2017-04-01

    It has been shown that a mixed precision approach that judiciously replaces double precision with single precision calculations can speed-up global simulations. In particular, a mixed precision variation of the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) showed virtually the same quality model results as the standard double precision version (Vana et al., Single precision in weather forecasting models: An evaluation with the IFS, Monthly Weather Review, in print). In this study, we perform detailed measurements of savings in computing time and energy using a mixed precision variation of the -OpenIFS- model. The mixed precision variation of OpenIFS is analogous to the IFS variation used in Vana et al. We (1) present results for energy measurements for simulations in single and double precision using Intel's RAPL technology, (2) conduct a -scaling- study to quantify the effects that increasing model resolution has on both energy dissipation and computing cycles, (3) analyze the differences between single core and multicore processing, and (4) compare the effects of different compiler technologies on the mixed precision OpenIFS code. In particular, we compare intel icc/ifort with gnu gcc/gfortran.

  3. Fast parametric relationships for the large-scale reservoir simulation of mixed CH4-CO2 gas hydrate systems

    Science.gov (United States)

    Reagan, Matthew T.; Moridis, George J.; Seim, Katie S.

    2017-06-01

    A recent Department of Energy field test on the Alaska North Slope has increased interest in the ability to simulate systems of mixed CO2-CH4 hydrates. However, the physically realistic simulation of mixed-hydrate simulation is not yet a fully solved problem. Limited quantitative laboratory data leads to the use of various ab initio, statistical mechanical, or other mathematic representations of mixed-hydrate phase behavior. Few of these methods are suitable for inclusion in reservoir simulations, particularly for systems with large number of grid elements, 3D systems, or systems with complex geometric configurations. In this work, we present a set of fast parametric relationships describing the thermodynamic properties and phase behavior of a mixed methane-carbon dioxide hydrate system. We use well-known, off-the-shelf hydrate physical properties packages to generate a sufficiently large dataset, select the most convenient and efficient mathematical forms, and fit the data to those forms to create a physical properties package suitable for inclusion in the TOUGH+ family of codes. The mapping of the phase and thermodynamic space reveals the complexity of the mixed-hydrate system and allows understanding of the thermodynamics at a level beyond what much of the existing laboratory data and literature currently offer.

  4. Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure

    Science.gov (United States)

    Bellan, Josette; Taskinoglu, Ezgi

    2012-01-01

    The simulation of high-pressure turbulent flows, where the pressure, p, is larger than the critical value, p(sub c), for the species under consideration, is relevant to a wide array of propulsion systems, e.g. gas turbine, diesel, and liquid rocket engines. Most turbulence models, however, have been developed for atmospheric-p turbulent flows. The difference between atmospheric-p and supercritical-p turbulence is that, in the former situation, the coupling between dynamics and thermodynamics is moderate to negligible, but for the latter it is very significant, and can dominate the flow characteristics. The reason for this stems from the mathematical form of the equation of state (EOS), which is the perfect-gas EOS in the former case, and the real-gas EOS in the latter case. For flows at supercritical pressure, p, the large eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas EOS. The equations use transport properties that depend on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid scale (SGS) fluxes, but also new SGS terms, each denoted as a correction. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations, and represent differences between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) that is the difference between the filtered divergence of the heat flux and the divergence of the heat flux computed as a function of the filtered flow field. In a previous study, there was only partial success in modeling the q-correction term, but in this innovation, success has been achieved by using a different modeling approach. This analysis, based on a temporal mixing layer Direct Numerical Simulation database, shows that the focus in modeling the q

  5. Time line cell tracking for the approximation of lagrangian coherent structures with subgrid accuracy

    KAUST Repository

    Kuhn, Alexander

    2013-12-05

    Lagrangian coherent structures (LCSs) have become a widespread and powerful method to describe dynamic motion patterns in time-dependent flow fields. The standard way to extract LCS is to compute height ridges in the finite-time Lyapunov exponent field. In this work, we present an alternative method to approximate Lagrangian features for 2D unsteady flow fields that achieve subgrid accuracy without additional particle sampling. We obtain this by a geometric reconstruction of the flow map using additional material constraints for the available samples. In comparison to the standard method, this allows for a more accurate global approximation of LCS on sparse grids and for long integration intervals. The proposed algorithm works directly on a set of given particle trajectories and without additional flow map derivatives. We demonstrate its application for a set of computational fluid dynamic examples, as well as trajectories acquired by Lagrangian methods, and discuss its benefits and limitations. © 2013 The Authors Computer Graphics Forum © 2013 The Eurographics Association and John Wiley & Sons Ltd.

  6. Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova

    Energy Technology Data Exchange (ETDEWEB)

    James Glimm

    2009-06-04

    The three year plan for this project was to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (Direct Numerical Simulation (DNS), Large Eddy Simulations (LES), full two fluid simulations and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We model 2D and 3D perturbations of planar or circular interfaces. We compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. Multiple layers and reshock are considered here.

  7. Grain to outcrop-scale frozen moments of dynamic magma mixing in the syenite magma chamber, Yelagiri Alkaline Complex, South India

    Directory of Open Access Journals (Sweden)

    M.L. Renjith

    2014-11-01

    Full Text Available Magma mixing process is unusual in the petrogenesis of felsic rocks associated with alkaline complex worldwide. Here we present a rare example of magma mixing in syenite from the Yelagiri Alkaline Complex, South India. Yelagiri syenite is a reversely zoned massif with shoshonitic (Na2O + K2O=5–10 wt.%, Na2O/K2O = 0.5–2, TiO2 <0.7 wt.% and metaluminous character. Systematic modal variation of plagioclase (An11–16 Ab82–88, K-feldspar (Or27–95 Ab5–61, diopside (En34–40Fs11–18Wo46–49, biotite, and Ca-amphibole (edenite build up three syenite facies within it and imply the role of in-situ fractional crystallization (FC. Evidences such as (1 disequilibrium micro-textures in feldspars, (2 microgranular mafic enclaves (MME and (3 synplutonic dykes signify mixing of shoshonitic mafic magma (MgO = 4–5 wt.%, SiO2 = 54–59 wt.%, K2O/Na2O = 0.4–0.9 with syenite. Molecular-scale mixing of mafic magma resulted disequilibrium growth of feldspars in syenite. Physical entity of mafic magma preserved as MME due to high thermal-rheological contrast with syenite magma show various hybridization through chemical exchange, mechanical dilution enhanced by chaotic advection and phenocryst migration. In synplutonic dykes, disaggregation and mixing of mafic magma was confined within the conduit of injection. Major-oxides mass balance test quantified that approximately 0.6 portions of mafic magma had interacted with most evolved syenite magma and generated most hybridized MME and dyke samples. It is unique that all the rock types (syenite, MME and synplutonic dykes share similar shoshonitic and metaluminous character; mineral chemistry, REE content, coherent geochemical variation in Harker diagram suggest that mixing of magma between similar composition. Outcrop-scale features of crystal accumulation and flow fabrics also significant along with MME and synplutonic dykes in syenite suggesting that Yelagiri syenite magma chamber had evolved

  8. Seasonal development of mixed layer depths, nutrients, chlorophyll and Calanus finmarchicus in the Norwegian Sea - A basin-scale habitat comparison

    KAUST Repository

    Bagøien, Espen

    2012-09-01

    Seasonal patterns for mixed layer depths, nutrients, chlorophyll, and Calanus finmarchicus in different water masses between 62 and 70°N of the Norwegian Sea were compared using spatiotemporally aggregated basin-scale data. Norwegian Coastal Water was stratified throughout the year due to a low-salinity upper layer. The winter mixed layer depth was typically about 50-60m, and the spring phytoplankton bloom peaked in late April. In Atlantic and Arctic Waters the winter mixed layer depths were much greater, typically about 175-250m. Due to the requirement for thermal stratification, the phytoplankton build-ups there were slower and the peaks were delayed until late May. Seasonal development of mixed layer depths, nutrient consumption and chlorophyll was similar for the Atlantic and Arctic areas. Young Calanus copepodites of the first new generation in Coastal Water peaked in early May, preceding the peak in Atlantic Water by about 2weeks, and that in Arctic Water by about 6weeks. While the young G 1 cohorts in Coastal and Atlantic waters coincided rather well in time with the phytoplankton blooms, the timing of the cohort in Arctic Water was delayed compared to the phytoplankton. Two or more Calanus generations in Coastal Water, and two generations in Atlantic Water were observed. Only one generation was found in Arctic Water, where scarce autumn data precludes evaluation of a possible second generation. © 2012 Elsevier Ltd.

  9. The effect of design and scale on the mixing and mass transfer in U-loop bioreactors

    DEFF Research Database (Denmark)

    Petersen, Leander Adrian Haaning; Villadsen, John; Jørgensen, Sten Bay

    vertical forced flow loop reactor where gas and liquid are driven through a series of static mixers in a U-shaped pipe, is quite capable of coping with these challenges in pilot scale. The critical question remains; what happens when the scale undergoes a more than 10 fold increase and the geometry...

  10. Investigating Effect of Ignoring Hierarchical Data Structures on Accuracy of Vertical Scaling Using Mixed-Effects Rasch Model

    Science.gov (United States)

    Wang, Shudong; Jiao, Hong; Jin, Ying; Thum, Yeow Meng

    2010-01-01

    The vertical scales of large-scale achievement tests created by using item response theory (IRT) models are mostly based on cluster (or correlated) educational data in which students usually are clustered in certain groups or settings (classrooms or schools). While such application directly violated assumption of independent sample of person in…

  11. Use of fundamental condensation heat transfer experiments for the development of a sub-grid liquid jet condensation model

    Energy Technology Data Exchange (ETDEWEB)

    Buschman, Francis X., E-mail: Francis.Buschman@unnpp.gov; Aumiller, David L.

    2017-02-15

    Highlights: • Direct contact condensation data on liquid jets up to 1.7 MPa in pure steam and in the presence of noncondensable gas. • Identified a pressure effect on the impact of noncondensables to suppress condensation heat transfer not captured in existing data or correlations. • Pure steam data is used to develop a new correlation for condensation heat transfer on subcooled liquid jets. • Noncondensable data used to develop a modification to the renewal time estimate used in the Young and Bajorek correlation for condensation suppression in the presence of noncondensables. • A jet injection boundary condition, using a sub-grid jet condensation model, is developed for COBRA-IE which provides a more detailed estimate of the condensation rate on the liquid jet and allows the use of jet specific closure relationships. - Abstract: Condensation on liquid jets is an important phenomenon for many different facets of nuclear power plant transients and analyses such as containment spray cooling. An experimental facility constructed at the Pennsylvania State University, the High Pressure Liquid Jet Condensation Heat Transfer facility (HPLJCHT), has been used to perform steady-state condensation heat transfer experiments in which the temperature of the liquid jet is measured at different axial locations allowing the condensation rate to be determined over the jet length. Test data have been obtained in a pure steam environment and with varying concentrations of noncondensable gas. This data extends the available jet condensation data from near atmospheric pressure up to a pressure of 1.7 MPa. An empirical correlation for the liquid side condensation heat transfer coefficient has been developed based on the data obtained in pure steam. The data obtained with noncondensable gas were used to develop a correlation for the renewal time as used in the condensation suppression model developed by Young and Bajorek. This paper describes a new sub-grid liquid jet

  12. Proceedings of the workshop on hydrocarbon processing mixing and scale-up problems. [Fuels processing for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Gabor, J. D. [ed.

    1978-01-01

    A workshop was convened by the Division of Fossil Fuel Utilization of the US Department of Energy in cooperation with the Particulate and Multiphase Process Program of the National Science Foundation to identify needs for fundamental engineering support for the design of chemical reactors for processing heavy hydrocarbon liquids. The problems associated with dispersing liquid hydrocarbons in a reacting gas and mixing within the gas phase are of primary concern. The transactions of the workshop begin with an introduction to the immediate goals of the Department of Energy. Fuel cell systems and current research and development are reviewed. Modeling of combustion and the problems of soot formation and deposits in hydrocarbon fuels are next considered. The fluid mechanics of turbulent mixing and its effect on chemical reactions are then presented. Current experimental work and process development provide an update on the present state-of-the-art.

  13. Simulated Transport and Mixing of Anthropogenic and Biogenic Aerosol and Their Entrainment into Clouds during the Goamazon Campaign

    Science.gov (United States)

    Fast, J. D.; Shrivastava, M. B.; Fan, J.; Berg, L. K.; Chand, D.; Fortner, E.; Mei, F.; Pekour, M. S.; Shilling, J. E.; Springston, S. R.; Tomlinson, J. M.; Wang, J.

    2014-12-01

    Several recent studies have suggested that anthropogenic emissions enhance the production of biogenic secondary organic aerosol (SOA). Because Manaus, Brazil is an isolated large city within the Amazon rainforest, measurements collected within and outside of the downwind urban plume during the 2014 Green Ocean Amazon (GoAmazon) campaign (supported by the U.S. Department of Energy's Atmospheric Radiation and Measurement program) will provide valuable information needed by regional and global models to evaluate parameterizations of SOA. The isolated urban plume should also provide distinct patterns of mixing with biogenic emissions and eliminate complications of multiple anthropogenic sources found in most other regions of the world. The objective of this study is to evaluate the performance of preliminary simulations of the transport, mixing, and chemical evolution of the Manaus urban plume from the chemistry version of the Weather Research and Forecasting model (WRF-Chem) using the available surface and aircraft measurements collected during the first intensive observation period (IOP) of GoAmazon. Simulations are performed using both a 10 km or 2 km grid spacing as well as a newly developed treatment that couples a sectional aerosol model and its parameterization of SOA using a volatility basis set approach with resolved clouds and a sub-grid scale cloud parameterization. Since the first IOP of GoAmazon was conducted during the wet season, shallow and deep convection were observed on most days and likely impacts the transport and vertical mixing of the Manaus plume. Therefore, we are using the available field campaign cloud measurements to evaluate the impact of sub-grid scale clouds on the horizontal and vertical distribution of aerosols. Satellite data is also used to assess the regional variability in simulated clouds and precipitation. Analyses of the simulations during the first IOP will be presented. Simulations with and without anthropogenic emissions will

  14. Predictions of dynamic changes in reaction rates as a consequence of incomplete mixing using pore scale reactive transport modeling on images of porous media.

    Science.gov (United States)

    Alhashmi, Z; Blunt, M J; Bijeljic, B

    2015-08-01

    We present a pore scale model capable of simulating fluid/fluid reactive transport on images of porous media from first principles. We use a streamline-based particle tracking method for simulating flow and transport, while for reaction to occur, both reactants must be within a diffusive distance of each other during a time-step. We assign a probability of reaction (Pr), as a function of the reaction rate constant (kr) and the diffusion length. Firstly, we validate our model for reaction against analytical solutions for the bimolecular reaction (A+B→C) in a free fluid. Then, we simulate transport and reaction in a beadpack to validate the model through predicting the fluid/fluid reaction experimental results provided by Gramling et al. (2002). Our model accurately predicts the experimental data, as it takes into account the degree of incomplete mixing present at the sub-pore (image voxel) level, in contrast to advection-dispersion-reaction equation (ADRE) model that over-predicts pore scale mixing. Finally, we show how our model can predict dynamic changes in the reaction rate accurately accounting for the local geometry, topology and flow field at the pore scale. We demonstrate the substantial difference between the predicted early-time reaction rate in comparison to the ADRE model. Copyright © 2015. Published by Elsevier B.V.

  15. Determining student teachers' perceptions on using technology via Likert scale, visual association test and metaphors: A mixed study

    National Research Council Canada - National Science Library

    Mevhibe Kobak; Nazlı Ruya Taşkın

    2013-01-01

    .... Based on the data obtained, even though student teachers’ perceptions on using technology were found positive in the light of Likert scale, there was no significant relation in terms of gender and enrolled undergraduate program...

  16. Stochastic representation of the Reynolds transport theorem: revisiting large-scale modeling

    CERN Document Server

    Harouna, S Kadri

    2016-01-01

    We explore the potential of a formulation of the Navier-Stokes equations incorporating a random description of the small-scale velocity component. This model, established from a version of the Reynolds transport theorem adapted to a stochastic representation of the flow, gives rise to a large-scale description of the flow dynamics in which emerges an anisotropic subgrid tensor, reminiscent to the Reynolds stress tensor, together with a drift correction due to an inhomogeneous turbulence. The corresponding subgrid model, which depends on the small scales velocity variance, generalizes the Boussinesq eddy viscosity assumption. However, it is not anymore obtained from an analogy with molecular dissipation but ensues rigorously from the random modeling of the flow. This principle allows us to propose several subgrid models defined directly on the resolved flow component. We assess and compare numerically those models on a standard Green-Taylor vortex flow at Reynolds 1600. The numerical simulations, carried out w...

  17. Application of spectral linear mixing to rock slabs analyses at various scales using Ma_Miss BreadBoard instrument

    Science.gov (United States)

    De Angelis, Simone; Manzari, Paola; De Sanctis, Maria Cristina; Altieri, Francesca; Carli, Cristian; Agrosì, Giovanna

    2017-09-01

    Focus of this work is the analysis of rock slabs by means of the Ma_Miss BreadBoard instrument. Ma_Miss (Mars Multispectral Imager for Subsurface Studies, Coradini et al., 2001; De Sanctis et al., 2017) is the miniaturized imaging spectrometer onboard the ESA Exomars 2020 mission. Here we report the results of the analysis carried out on rock slabs using the Ma_Miss breadboard (BB) (De Angelis et al., 2014, 2015) and a Spectro-Goniometer (SPG). The samples are three volcanic rocks (from the Aeolian Islands and Montiferru volcanoes, Italy) and two carbonate rocks (from Central Apennines, Italy). Visible and near infrared spectroscopic characterization has been first performed on all the samples with a Spectro-goniometer (SPG). Successively, higher spatial resolution spectra were acquired with the Ma_Miss BB setup in each of the areas analyzed with the SPG. We compared the spectra of the same areas of the slabs, acquired with SPG and Ma_Miss BB. Three different analysis approaches have been performed on the spectra: arithmetical averaging of the spectra, linear mixing of reflectances and linear mixing of Single Scattering Albedoes (using Hapke model). The comparison shows that: (i) Ma_Miss instrument has great capabilities for the investigation of rock surfaces with high detail; a large number of different mineralogical phases can be recognized thanks to Ma_Miss high resolution within each millimeter-sized analyzed area; (ii) the agreement with SPG spectra is excellent especially when linear mixing is applied for the convolution of Ma_Miss BB spectra.

  18. Simultaneous inference for multilevel linear mixed models - with an application to a large-scale school meal study

    DEFF Research Database (Denmark)

    Ritz, Christian; Laursen, Rikke Pilmann; Damsgaard, Camilla Trab

    2017-01-01

    of a school meal programme. We propose a novel and versatile framework for simultaneous inference on parameters estimated from linear mixed models that were fitted separately for several outcomes from the same study, but did not necessarily contain the same fixed or random effects. By combining asymptotic...... sizes of practical relevance we studied simultaneous coverage through simulation, which showed that the approach achieved acceptable coverage probabilities even for small sample sizes (10 clusters) and for 2–16 outcomes. The approach also compared favourably with a joint modelling approach. We also...

  19. Numerical analysis of blunting of a crack tip in a ductile material under small-scale yielding and mixed mode loading

    Science.gov (United States)

    Saka, M.; Abé, H.; Tanaka, S.

    1986-03-01

    The blunting of the tip of a crack in a ductile material is analysed under the conditions of plane strain, small-scale yielding, and mixed mode loading of Modes I and II. The material is assumed to be an elastic-perfectly plastic solid with Poisson's ratio being 1/2. The stress and strain fields for a sharp crack under mixed mode loading are first determined by means of elastic-plastic finite element analysis. It is shown that only one elastic sector exists around the crack tip, in contrast with the possibility of existence of two elastic sectors as discussed by Gao. The results obtained for a sharp crack are used as the boundary conditions for the subsequent numerical analysis of crack tip blunting under mixed mode loading, based on slip line theory. The characteristic shapes of the blunted crack tip are obtained for a wide range of Mode I and Mode II combinations, and found to resemble the tip of Japanese sword. Also the stress field around the blunted crack tip is determined.

  20. Spatial heterogeneity and scale-dependent habitat selection for two sympatric raptors in mixed-grass prairie.

    Science.gov (United States)

    Atuo, Fidelis Akunke; O'Connell, Timothy John

    2017-08-01

    Sympatric predators are predicted to partition resources, especially under conditions of food limitation. Spatial heterogeneity that influences prey availability might play an important role in the scales at which potential competitors select habitat. We assessed potential mechanisms for coexistence by examining the role of heterogeneity in resource partitioning between sympatric raptors overwintering in the southern Great Plains. We conducted surveys for wintering Red-tailed hawk (Buteo jamaicensis) and Northern Harrier (Circus cyanea) at two state wildlife management areas in Oklahoma, USA. We used information from repeated distance sampling to project use locations in a GIS. We applied resource selection functions to model habitat selection at three scales and analyzed for niche partitioning using the outlying mean index. Habitat selection of the two predators was mediated by spatial heterogeneity. The two predators demonstrated significant fine-scale discrimination in habitat selection in homogeneous landscapes, but were more sympatric in heterogeneous landscapes. Red-tailed hawk used a variety of cover types in heterogeneous landscapes but specialized on riparian forest in homogeneous landscapes. Northern Harrier specialized on upland grasslands in homogeneous landscapes but selected more cover types in heterogeneous landscapes. Our study supports the growing body of evidence that landscapes can affect animal behaviors. In the system we studied, larger patches of primary land cover types were associated with greater allopatry in habitat selection between two potentially competing predators. Heterogeneity within the scale of raptor home ranges was associated with greater sympatry in use and less specialization in land cover types selected.

  1. Investigation of mixing enhancement in porous media under helical flow conditions: 3-D bench-scale experiments

    DEFF Research Database (Denmark)

    Chiogna, Gabriele; Ye, Yu; Cirpka, Olaf A.

    2017-01-01

    Lateral mass exchange at the fringe of solute plumes is a fundamental process leading to plume dilution and reactive mixing. Mass transfer between the plume and ambient water can be considerably enhanced by helical flow occurring in three-dimensional heterogeneous anisotropic porous media [1-3]. We...... performed steady-state conservative tracer experiments in a fully three-dimensional flow-through chamber to investigate the effects of helical flow on plume spiraling and deformation, as well as on its dilution [4]. Helical flow was created by packing the porous medium in angled stripes of materials...... with different grain sizes to create blocks with macroscopically anisotropic hydraulic conductivity. The hydraulic conductivity of the blocks was varied in different experiments. Solute concentrations and flow rates were measured at high spatial resolution for samples collected at 49 outlet ports. This allowed...

  2. Variational Multi-Scale method with spectral approximation of the sub-scales.

    KAUST Repository

    Dia, Ben Mansour

    2015-01-07

    A variational multi-scale method where the sub-grid scales are computed by spectral approximations is presented. It is based upon an extension of the spectral theorem to non necessarily self-adjoint elliptic operators that have an associated base of eigenfunctions which are orthonormal in weighted L2 spaces. We propose a feasible VMS-spectral method by truncation of this spectral expansion to a nite number of modes.

  3. Sensitivity of the scale partition for variational multiscale large-eddy simulation of channel flow

    NARCIS (Netherlands)

    Holmen, J.; Hughes, T.J.R.; Oberai, A.A.; Wells, G.N.

    2004-01-01

    The variational multiscale method has been shown to perform well for large-eddy simulation (LES) of turbulent flows. The method relies upon a partition of the resolved velocity field into large- and small-scale components. The subgrid model then acts only on the small scales of motion, unlike

  4. Trehalose as a stress marker of the physiological impact of mixing on yeast production: scale-down reactors and mini-bioreactors investigations

    Directory of Open Access Journals (Sweden)

    Thonart, P.

    2010-01-01

    Full Text Available Trehalose is a reserve carbohydrate produced by Saccharomyces cerevisiae under stress conditions and used as a cryoprotectant during freeze drying. So the cellular content of trehalose is an important parameter to control in industrial context. Scale-down reactors have been used to produce Saccharomyces cerevisiae. These reactors permit to mimic the hydrodynamic conditions experienced by cells during large scale production. Three types of scale-down reactors have been tested, differing by the geometry of the non-mixed part and the recirculation flow rate. The results show that cells cultivated in scale-down reactors produced less trehalose compared to the reference reactor. These results are completed by the study of the expression of the TPS2 promoter coupled with a green fluorescent protein (GFP. TPS2 is a gene coding for a subunit of the enzymatic complex responsible of trehalose synthesis. This strain was produced in mini-bioreactors which are shake flasks equipped with a dissolved oxygen probe. This approach allows using trehalose, or related enzymes, as a cellular marker of the stress encountered by yeast in industrial process.

  5. Spatial heterogeneity and scale?dependent habitat selection for two sympatric raptors in mixed?grass prairie

    OpenAIRE

    Atuo, Fidelis Akunke; O'Connell, Timothy John

    2017-01-01

    Abstract Sympatric predators are predicted to partition resources, especially under conditions of food limitation. Spatial heterogeneity that influences prey availability might play an important role in the scales at which potential competitors select habitat. We assessed potential mechanisms for coexistence by examining the role of heterogeneity in resource partitioning between sympatric raptors overwintering in the southern Great Plains. We conducted surveys for wintering Red?tailed hawk (B...

  6. Scaling Behavior of Quantum Nanosystems: Emergence of Quasi-particles, Collective Modes, and Mixed Exchange Symmetry States

    OpenAIRE

    Shreif, Zeina; Ortoleva, Peter

    2011-01-01

    Quantum nanosystems such as graphene nanoribbons or superconducting nanoparticles are studied via a multiscale approach. Long space-time dynamics is derived using a perturbation expansion in the ratio of the nearest-neighbor distance to a nanometer-scale characteristic length, and a theorem on the equivalence of long-time averages and expectation values. This dynamics is shown to satisfy a coarse-grained wave equation (CGWE) which takes a Schr\\"odinger-like form with modified masses and inter...

  7. From Detailed Description of Chemical Reacting Carbon Particles to Subgrid Models for CFD

    Directory of Open Access Journals (Sweden)

    Schulze S.

    2013-04-01

    Full Text Available This work is devoted to the development and validation of a sub-model for the partial oxidation of a spherical char particle moving in an air/steam atmosphere. The particle diameter is 2 mm. The coal particle is represented by moisture- and ash-free nonporous carbon while the coal rank is implemented using semi-global reaction rate expressions taken from the literature. The submodel includes six gaseous chemical species (O2, CO2, CO, H2O, H2, N2. Three heterogeneous reactions are employed, along with two homogeneous semi-global reactions, namely carbon monoxide oxidation and the water-gas-shift reaction. The distinguishing feature of the subgrid model is that it takes into account the influence of homogeneous reactions on integral characteristics such as carbon combustion rates and particle temperature. The sub-model was validated by comparing its results with a comprehensive CFD-based model resolving the issues of bulk flow and boundary layer around the particle. In this model, the Navier-Stokes equations coupled with the energy and species conservation equations were used to solve the problem by means of the pseudo-steady state approach. At the surface of the particle, the balance of mass, energy and species concentration was applied including the effect of the Stefan flow and heat loss due to radiation at the surface of the particle. Good agreement was achieved between the sub-model and the CFD-based model. Additionally, the CFD-based model was verified against experimental data published in the literature (Makino et al. (2003 Combust. Flame 132, 743-753. Good agreement was achieved between numerically predicted and experimentally obtained data for input conditions corresponding to the kinetically controlled regime. The maximal discrepancy (10% between the experiments and the numerical results was observed in the diffusion-controlled regime. Finally, we discuss the influence of the Reynolds number, the ambient O2 mass fraction and the ambient

  8. 3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields

    Directory of Open Access Journals (Sweden)

    Dan Kang

    2014-01-01

    Full Text Available In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  9. 3D online submicron scale observation of mixed metal powder's microstructure evolution in high temperature and microwave compound fields.

    Science.gov (United States)

    Kang, Dan; Xu, Feng; Hu, Xiao-fang; Dong, Bo; Xiao, Yu; Xiao, Ti-qiao

    2014-01-01

    In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37  μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  10. Insights into large-scale cell-culture reactors: II. Gas-phase mixing and CO₂ stripping.

    Science.gov (United States)

    Sieblist, Christian; Hägeholz, Oliver; Aehle, Mathias; Jenzsch, Marco; Pohlscheidt, Michael; Lübbert, Andreas

    2011-12-01

    Most discussions about stirred tank bioreactors for cell cultures focus on liquid-phase motions and neglect the importance of the gas phase for mixing, power input and especially CO(2) stripping. Particularly in large production reactors, CO(2) removal from the culture is known to be a major problem. Here, we show that stripping is mainly affected by the change of the gas composition during the movement of the gas phase through the bioreactor from the sparger system towards the headspace. A mathematical model for CO(2)-stripping and O(2)-mass transfer is presented taking gas-residence times into account. The gas phase is not moving through the reactor in form of a plug flow as often assumed. The model is validated by measurement data. Further measurement results are presented that show how the gas is partly recirculated by the impellers, thus increasing the gas-residence time. The gas-residence times can be measured easily with stimulus-response techniques. The results offer further insights on the gas-residence time distributions in stirred tank reactors. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Near-Surface Scale-Model GPR Sandbox Experiments with Cylinders and Spheres: Resonances from Mixed Direct, Reflective, Circumferential, and Refractive-Shortcut Modes

    Science.gov (United States)

    Arcone, S. A.

    2016-12-01

    Scale-model 2.6 GHz GPR experiments performed using a sandbox reveal mode mixing within the frequency spectra of common targets, and the benefits of using frequency spectra to detect target attributes. The box was 4 m long, 1.2 m wide, 1 m deep, and filled with pure quartz medium sand with dielectric constant of 2.6, as verified by bottom reflections and ground wave measurements. The scale factor is 10 for the detection of field targets 20-40 cm deep by a 260 MHz GPR. Modes mean various ray-optic propagation paths between transmitter and receiver antennas, and along which time delays were calculated, even for circumferential modes, which are visualized computationally. Mixing means constructive interference between most of these modes to produce resonances. Cylindrical targets were several cm deep and in diameter. Antennas were on or close to the surface. Processing included background removal to eliminate direct coupling, but which did not reduce its higher frequency modal effects. Despite the short pulse of only 0.7 ns duration, the interference acts as though spectra consist of infinite wavetrains, as is well known from Fourier theory. Important resonances result from interference between 1) direct coupling from transmitter to receiver antennas and circumferential modes for a metal pipe of any length, rather than any half-wave resonance caused by pipe length; 2) direct coupling and target surface reflections for a cylinder or flat plate; and 3) direct ground and surface waves for off-axis detection. Resonances near 800 MHz are masked by the direct coupling and may be caused by subtractive mixing of two pairs of mixed modes. A time domain radargram for a large dielectric sphere shows the enhanced Mie surface creep-refractive short-cut solution. Despite the 2.6 GHz pulse center frequency, the modes range from 0.7-5 GHz. The interference caused by the direct coupling is almost ubiquitous and must be considered in target detection. Resonances hold for antennas

  12. Determining student teachers' perceptions on using technology via Likert scale, visual association test and metaphors: A mixed study

    Directory of Open Access Journals (Sweden)

    Mevhibe Kobak

    2013-04-01

    Full Text Available The aim of this study is to determine senior student teachers’ perceptions on using technology by approaching various points of view. In this study, researchers collected data through Technology Perceptions Scale, Visual Association Activity and Technology Metaphors. The participants of the study were 104 senior student teachers who were enrolled in Balıkesir University Necatibey Faculty of Education. In this descriptive study, researchers interpreted qualitative data in conjunction with quantitative data. Based on the data obtained, even though student teachers’ perceptions on using technology were found positive in the light of Likert scale, there was no significant relation in terms of gender and enrolled undergraduate program. According to the results of visual association test, student teachers ranked smartboard, Internet and computer in the first three, and portable media player, mobile phone and video/camera in the last three. Besides, researchers analyzed and classified student teachers’ metaphors about technology under 9 categories: 1developing-changing technology, 2rapidly progressing technology, 3 limitless-endless technology, 4beneficial technology, 5harmful technology, 6both beneficial and harmful technology, 7indispensible technology, 8technology as a necessity, 9 all-inclusive technology. At the end of the study, those nine categories which were acquired using the content analysis technique are presented in a table which shows the interaction between categories in a holistic view.

  13. Workshop on Human Activity at Scale in Earth System Models

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Melissa R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Aziz, H. M. Abdul [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Coletti, Mark A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kennedy, Joseph H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nair, Sujithkumar S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Omitaomu, Olufemi A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-01-26

    Changing human activity within a geographical location may have significant influence on the global climate, but that activity must be parameterized in such a way as to allow these high-resolution sub-grid processes to affect global climate within that modeling framework. Additionally, we must have tools that provide decision support and inform local and regional policies regarding mitigation of and adaptation to climate change. The development of next-generation earth system models, that can produce actionable results with minimum uncertainties, depends on understanding global climate change and human activity interactions at policy implementation scales. Unfortunately, at best we currently have only limited schemes for relating high-resolution sectoral emissions to real-time weather, ultimately to become part of larger regions and well-mixed atmosphere. Moreover, even our understanding of meteorological processes at these scales is imperfect. This workshop addresses these shortcomings by providing a forum for discussion of what we know about these processes, what we can model, where we have gaps in these areas and how we can rise to the challenge to fill these gaps.

  14. Environmental impacts of a large-scale incinerator with mixed MSW of high water content from a LCA perspective.

    Science.gov (United States)

    Lou, Ziyang; Bilitewski, Bernd; Zhu, Nanwen; Chai, Xiaoli; Li, Bing; Zhao, Youcai

    2015-04-01

    Large-scale incinerators are applied widely as a result of the heavy burden of municipal solid waste (MSW) generated, while strong opposition is arising from the public living nearby. A large-scale working incineration plant of 1500 ton/day was chosen for evaluation using life cycle assessment. It was found that the corresponding human toxicity impacts via soil (HTs), human toxicity impacts via water (HTw) and human toxicity impacts via air (HTa) categories are 0.213, 2.171, and 0.012 personal equivalents (PE), and global warming (GW100) and nutrient enrichment (NE) impacts are 0.002 and 0.001 PE per ton of waste burned for this plant. Heavy metals in flue gas, such as Hg and Pb, are the two dominant contributors to the toxicity impact categories, and energy recovery could reduce the GW100 and NE greatly. The corresponding HTs, HTw and HTa decrease to 0.087, 0.911 and 0.008 PE, and GW100 turns into savings of -0.007 PE due to the increase of the heating value from 3935 to 5811 kJ/kg, if a trommel screener of 40 mm mesh size is used to pre-separate MSW. MSW sorting and the reduction of water content by physical pressure might be two promising pre-treatment methods to improve the combustion performance, and the application of stricter standards for leachate discharge and the flue gas purification process are two critical factors for improvement of the environmental profile identified in this work. Copyright © 2015. Published by Elsevier B.V.

  15. A mixed-methods study of system-level sustainability of evidence-based practices in 12 large-scale implementation initiatives.

    Science.gov (United States)

    Scudder, Ashley T; Taber-Thomas, Sarah M; Schaffner, Kristen; Pemberton, Joy R; Hunter, Leah; Herschell, Amy D

    2017-12-07

    In recent decades, evidence-based practices (EBPs) have been broadly promoted in community behavioural health systems in the United States of America, yet reported EBP penetration rates remain low. Determining how to systematically sustain EBPs in complex, multi-level service systems has important implications for public health. This study examined factors impacting the sustainability of parent-child interaction therapy (PCIT) in large-scale initiatives in order to identify potential predictors of sustainment. A mixed-methods approach to data collection was used. Qualitative interviews and quantitative surveys examining sustainability processes and outcomes were completed by participants from 12 large-scale initiatives. Sustainment strategies fell into nine categories, including infrastructure, training, marketing, integration and building partnerships. Strategies involving integration of PCIT into existing practices and quality monitoring predicted sustainment, while financing also emerged as a key factor. The reported factors and strategies impacting sustainability varied across initiatives; however, integration into existing practices, monitoring quality and financing appear central to high levels of sustainability of PCIT in community-based systems. More detailed examination of the progression of specific activities related to these strategies may aide in identifying priorities to include in strategic planning of future large-scale initiatives. ClinicalTrials.gov ID NCT02543359 ; Protocol number PRO12060529.

  16. A model for scale up of family health innovations in low-income and middle-income settings: a mixed methods study.

    Science.gov (United States)

    Bradley, Elizabeth H; Curry, Leslie A; Taylor, Lauren A; Pallas, Sarah Wood; Talbert-Slagle, Kristina; Yuan, Christina; Fox, Ashley; Minhas, Dilpreet; Ciccone, Dana Karen; Berg, David; Pérez-Escamilla, Rafael

    2012-01-01

    Many family health innovations that have been shown to be both efficacious and cost-effective fail to scale up for widespread use particularly in low-income and middle-income countries (LMIC). Although individual cases of successful scale-up, in which widespread take up occurs, have been described, we lack an integrated and practical model of scale-up that may be applicable to a wide range of public health innovations in LMIC. To develop an integrated and practical model of scale-up that synthesises experiences of family health programmes in LMICs. We conducted a mixed methods study that included in-depth interviews with 33 key informants and a systematic review of peer-reviewed and grey literature from 11 electronic databases and 20 global health agency web sites. We included key informants and studies that reported on the scale up of several family health innovations including Depo-Provera as an example of a product innovation, exclusive breastfeeding as an example of a health behaviour innovation, community health workers (CHWs) as an example of an organisational innovation and social marketing as an example of a business model innovation. Key informants were drawn from non-governmental, government and international organisations using snowball sampling. An article was excluded if the article: did not meet the study's definition of the innovation; did not address dissemination, diffusion, scale up or sustainability of the innovation; did not address low-income or middle-income countries; was superficial in its discussion and/or did not provide empirical evidence about scale-up of the innovation; was not available online in full text; or was not available in English, French, Spanish or Portuguese, resulting in a final sample of 41 peer-reviewed articles and 30 grey literature sources. We used the constant comparative method of qualitative data analysis to extract recurrent themes from the interviews, and we integrated these themes with findings from the

  17. Direct numerical simulation of a transitional supercritical binary mixing layer: heptane and nitrogen

    Science.gov (United States)

    Okong'o, Nora A.; Bellan, Josette

    2002-08-01

    mass flux rather than the typical momentum flux, which constitutes the governing dissipation in atmospheric mixing layers. Examination of the passive-scalar probability density functions (PDFs) indicates that neither the Gaussian, nor the beta PDFs are able to approximate the evolution of the DNS-extracted PDF from its inception through transition. Furthermore, the temperature species PDFs are well correlated, meaning that their joint PDF is not properly approximated by the product of their marginal PDFs; this indicates that the traditional reactive flow modelling based on replacing the joint PDF representing the reaction rate by the product of the marginal PDFs is not appropriate. Finally, the subgrid-scale temperature species PDFs are also well correlated, and the species PDF exhibits important departures from the Gaussian. These results suggest that classic PDFs used in atmospheric pressure flows would not capture the physics of this supercritical mixing layer, either in an assumed PDF model at the larger scale, or at the subgrid scale.

  18. Comparison of height-diameter models based on geographically weighted regressions and linear mixed modelling applied to large scale forest inventory data

    Energy Technology Data Exchange (ETDEWEB)

    Quirós Segovia, M.; Condés Ruiz, S.; Drápela, K.

    2016-07-01

    Aim of the study: The main objective of this study was to test Geographically Weighted Regression (GWR) for developing height-diameter curves for forests on a large scale and to compare it with Linear Mixed Models (LMM). Area of study: Monospecific stands of Pinus halepensis Mill. located in the region of Murcia (Southeast Spain). Materials and Methods: The dataset consisted of 230 sample plots (2582 trees) from the Third Spanish National Forest Inventory (SNFI) randomly split into training data (152 plots) and validation data (78 plots). Two different methodologies were used for modelling local (Petterson) and generalized height-diameter relationships (Cañadas I): GWR, with different bandwidths, and linear mixed models. Finally, the quality of the estimated models was compared throughout statistical analysis. Main results: In general, both LMM and GWR provide better prediction capability when applied to a generalized height-diameter function than when applied to a local one, with R2 values increasing from around 0.6 to 0.7 in the model validation. Bias and RMSE were also lower for the generalized function. However, error analysis showed that there were no large differences between these two methodologies, evidencing that GWR provides results which are as good as the more frequently used LMM methodology, at least when no additional measurements are available for calibrating. Research highlights: GWR is a type of spatial analysis for exploring spatially heterogeneous processes. GWR can model spatial variation in tree height-diameter relationship and its regression quality is comparable to LMM. The advantage of GWR over LMM is the possibility to determine the spatial location of every parameter without additional measurements. Abbreviations: GWR (Geographically Weighted Regression); LMM (Linear Mixed Model); SNFI (Spanish National Forest Inventory). (Author)

  19. Metal-fluxes characterization at a catchment scale: Study of mixing processes and end-member analysis in the Meca River watershed (SW Spain)

    Science.gov (United States)

    Cánovas, C. R.; Macías, F.; Olías, M.; López, R. Pérez; Nieto, J. M.

    2017-07-01

    Fluxes of acidity and contaminants from acid mine drainage (AMD) sources to the receiving surface water bodies were studied in a mining-impacted watershed (Meca River, SW Spain) using a novel methodology based on the joint application of EMMA and MIX codes. The application of EMMA and elemental ratios allowed delimiting the end-members responsible for water quality variations at a catchment scale. The further application of MIX quantified the significant impact of AMD on the river quality; less than 10% of AMD relative contribution is enough to maintain acidic conditions during most of the year. The mixing model also provided information about the element mobility, distinguishing those elements with a quasi-conservative behavior (e.g., Cu, Zn, Al, Co or Ni) from those affected by mineral precipitation/dissolution (e.g., K, Si, Na, Sr, Ca, Fe, Pb, or As). Floods are the main driver of dissolved and, mainly particulate, contaminants in the catchment. Thus, the first rainfall events in November only accounted for 19% of the annual Meca flow but yielded between 26 and 43% of the net acidity and dissolved metal loads (mainly, Fe, As and Pb). Concerning particulate transport, around 332 tons of particulate Fe, 49 tons of Al, 0.79 tons of As and 0.37 tons of Pb were recorded during these first floods. The particulate As concentration can be up to 34 times higher than the dissolved one during floods and between 2 and 4 times higher for Fe, Pb and Cr. This integrated modeling approach could be a promising and useful tool to face future restoration plans in derelict mines worldwide. This approach would allow prioritizing remedial measures, achieving an environmental and cost-effective restoration of degraded areas.

  20. Landscape-scale effects of fire severity on mixed-conifer and red fir forest structure in Yosemite National Park

    Science.gov (United States)

    Kane, Van R.; Lutz, James A.; Roberts, Susan L.; Smith, Douglas F.; McGaughey, Robert J.; Povak, Nicholas A.; Brooks, Matthew L.

    2013-01-01

    While fire shapes the structure of forests and acts as a keystone process, the details of how fire modifies forest structure have been difficult to evaluate because of the complexity of interactions between fires and forests. We studied this relationship across 69.2 km2 of Yosemite National Park, USA, that was subject to 32 fires ⩾40 ha between 1984 and 2010. Forests types included ponderosa pine (Pinus ponderosa), white fir-sugar pine (Abies concolor/Pinus lambertiana), and red fir (Abies magnifica). We estimated and stratified burned area by fire severity using the Landsat-derived Relativized differenced Normalized Burn Ratio (RdNBR). Airborne LiDAR data, acquired in July 2010, measured the vertical and horizontal structure of canopy material and landscape patterning of canopy patches and gaps. Increasing fire severity changed structure at the scale of fire severity patches, the arrangement of canopy patches and gaps within fire severity patches, and vertically within tree clumps. Each forest type showed an individual trajectory of structural change with increasing fire severity. As a result, the relationship between estimates of fire severity such as RdNBR and actual changes appears to vary among forest types. We found three arrangements of canopy patches and gaps associated with different fire severities: canopy-gap arrangements in which gaps were enclosed in otherwise continuous canopy (typically unburned and low fire severities); patch-gap arrangements in which tree clumps and gaps alternated and neither dominated (typically moderate fire severity); and open-patch arrangements in which trees were scattered across open areas (typically high fire severity). Compared to stands outside fire perimeters, increasing fire severity generally resulted first in loss of canopy cover in lower height strata and increased number and size of gaps, then in loss of canopy cover in higher height strata, and eventually the transition to open areas with few or no trees. However

  1. A novel image fusion algorithm based on 2D scale-mixing complex wavelet transform and Bayesian MAP estimation for multimodal medical images

    Directory of Open Access Journals (Sweden)

    Abdallah Bengueddoudj

    2017-05-01

    Full Text Available In this paper, we propose a new image fusion algorithm based on two-dimensional Scale-Mixing Complex Wavelet Transform (2D-SMCWT. The fusion of the detail 2D-SMCWT coefficients is performed via a Bayesian Maximum a Posteriori (MAP approach by considering a trivariate statistical model for the local neighboring of 2D-SMCWT coefficients. For the approximation coefficients, a new fusion rule based on the Principal Component Analysis (PCA is applied. We conduct several experiments using three different groups of multimodal medical images to evaluate the performance of the proposed method. The obtained results prove the superiority of the proposed method over the state of the art fusion methods in terms of visual quality and several commonly used metrics. Robustness of the proposed method is further tested against different types of noise. The plots of fusion metrics establish the accuracy of the proposed fusion method.

  2. In-stream attenuation of nitrogen and phosphorus from major point source in large-scale watershed: mixed source and long-term variation

    Science.gov (United States)

    Chen, X.; Fulda, M.; Keller, A. A.

    2011-12-01

    Increased human activity in agriculture and industry has posed significant impact on natural water bodies and resulted in water quality deterioration. Agricultural non-point source pollution and urban point source discharge from municipal waste water treatment plant are the more recent concerns. Computer models are often used to help assess the fate and transport of pollutant, which involves complex interactions such as adsorption, biochemical reaction and plants uptake. However, it remains to be a challenge to assess the attenuation of total nitrogen and total phosphorus in large-scale watershed where there are significant difference in land use types and soil properties, especially when there are significant temporal variations through a long-term simulation. In this study, a large-scale watershed model in the Ohio River Basin was constructed considering a ten year simulation period. To assess the downstream impacts of increasing or decreasing nutrient loads, a hypothetical waste water treatment plant was added as the point source in different subwatersheds, monitoring the downstream effects. Five scenarios (100 kg/d Ammonia, 100 kg/d Nitrate, 100 kg/d Phosphate, mixed 100 kg/d Ammonia & 100 kg/d Phosphate and mixed 100 kg/d Nitrate & 100 kg/d Phosphate) were examined to assess the attenuation process throughout the 10-years simulation. In addition to significant differences in the attenuation in different subwatersheds, the various loads had complex interrelations. We also observed significant variations in attenuation for short-term simulation, while in long-term, the attenuation factors tended to be stabilized.

  3. Large Eddy Simulation of an SD7003 Airfoil: Effects of Reynolds number and Subgrid-scale modeling

    DEFF Research Database (Denmark)

    Sarlak Chivaee, Hamid

    2017-01-01

    This paper presents results of a series of numerical simulations in order to study aerodynamic characteristics of the low Reynolds number Selig-Donovan airfoil, SD7003. Large Eddy Simulation (LES) technique is used for all computations at chord-based Reynolds numbers 10,000, 24,000 and 60...

  4. What Do People Who Score Highly on the Tampa Scale of Kinesiophobia Really Believe?: A Mixed Methods Investigation in People With Chronic Nonspecific Low Back Pain.

    Science.gov (United States)

    Bunzli, Samantha; Smith, Anne; Watkins, Rochelle; Schütze, Robert; O'Sullivan, Peter

    2015-07-01

    The Tampa Scale of Kinesiophobia (TSK) has been used to identify people with back pain who have high levels of "fear of movement" to direct them into fear reduction interventions. However, there is considerable debate as to what construct(s) the scale measures. Somatic Focus and Activity Avoidance subscales identified in factor analytic studies remain poorly defined. Using a mixed methods design, this study sought to understand the beliefs that underlie high scores on the TSK to better understand what construct(s) it measures. In-depth qualitative interviews with 36 adults with chronic nonspecific low back pain (average duration=7 y), scoring highly on the TSK (average score=47/68), were conducted. Following inductive analysis of transcripts, individuals were classified into groups on the basis of underlying beliefs. Associations between groups and itemized scores on the TSK and subscales were explored. Frequencies of response for each item were evaluated. Two main beliefs were identified: (1) The belief that painful activity will result in damage; and (2) The belief that painful activity will increase suffering and/or functional loss. The Somatic Focus subscale was able to discriminate between the 2 belief groups lending construct validity to the subscale. Ambiguous wording of the Activity Avoidance subscale may explain limitations in discriminate ability. The TSK may be better described as a measure of the "beliefs that painful activity will result in damage and/or increased suffering and/or functional loss."

  5. Asenapine effects on individual Young Mania Rating Scale items in bipolar disorder patients with acute manic or mixed episodes: a pooled analysis

    Directory of Open Access Journals (Sweden)

    Cazorla P

    2013-03-01

    Full Text Available Pilar Cazorla, Jun Zhao, Mary Mackle, Armin Szegedi Merck, Rahway, NJ, USA Background: An exploratory post hoc analysis was conducted to evaluate the potential differential effects over time of asenapine and olanzapine compared with placebo on the eleven individual items comprising the Young Mania Rating Scale (YMRS in patients with manic or mixed episodes in bipolar I disorder. Methods: Data were pooled from two 3-week randomized, controlled trials in which the eleven individual items comprising the YMRS were measured over 21 days. An analysis of covariance model adjusted by baseline value was used to test for differences in changes from baseline in YMRS scores between groups. Results: Each of the eleven individual YMRS item scores was significantly reduced compared with placebo at day 21. After 2 days of treatment, asenapine and olanzapine were superior to placebo for six of the YMRS items: disruptive/aggressive behavior, content, irritability, elevated mood, sleep, and speech. Conclusion: Reduction in manic symptoms over 21 days was associated with a broad-based improvement across all symptom domains with no subset of symptoms predominating. Keywords: asenapine, Young Mania Rating Scale, bipolar disorder, YMRS, antipsychotic, olanzapine

  6. Auto-Thermal Reforming Using Mixed Ion-Electronic Conducting Ceramic Membranes for a Small-Scale H2 Production Plant

    Directory of Open Access Journals (Sweden)

    Vincenzo Spallina

    2015-03-01

    Full Text Available The integration of mixed ionic electronic conducting (MIEC membranes for air separation in a small-to-medium scale unit for H2 production (in the range of 650–850 Nm3/h via auto-thermal reforming of methane has been investigated in the present study. Membranes based on mixed ionic electronic conducting oxides such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF give sufficiently high oxygen fluxes at temperatures above 800 °C with high purity (higher than 99%. Experimental results of membrane permeation tests are presented and used for the reactor design with a detailed reactor model. The assessment of the H2 plant has been carried out for different operating conditions and reactor geometry and an energy analysis has been carried out with the flowsheeting software Aspen Plus, including also the turbomachines required for a proper thermal integration. A micro-gas turbine is integrated in the system in order to supply part of the electricity required in the system. The analysis of the system shows that the reforming efficiency is in the range of 62%–70% in the case where the temperature at the auto-thermal reforming membrane reactor (ATR-MR is equal to 900 °C. When the electric consumption and the thermal export are included the efficiency of the plant approaches 74%–78%. The design of the reactor has been carried out using a reactor model linked to the Aspen flowsheet and the results show that with a larger reactor volume the performance of the system can be improved, especially because of the reduced electric consumption. From this analysis it has been found that for a production of about 790 Nm3/h pure H2, a reactor with a diameter of 1 m and length of 1.8 m with about 1500 membranes of 2 cm diameter is required.

  7. Is the increase of scale in the tropics a pathway to smallholders? Dimension and ecological zone effect on the mixed crop-livestock farms

    Directory of Open Access Journals (Sweden)

    Jaime Rangel

    2017-07-01

    Full Text Available Mixed crop-livestock farms are widely spread in different tropical regions in the world; they contribute to food security, rural development, sustainability and poverty alleviation. The effect of scale on performance of dual purpose (DP cattle farms was evaluated in two Mexican ecological zones: dry (DT and wet tropics (WT. In 2011, a questionnaire of 184 items distributed into technical and social characteristics was applied to a representative sample of 3,285 farms with 50 or less cows (0.97%. The farms were classified into three groups according to their dimension: very small (1-9 cows, small (10-19 cows and medium (20-50 cows. A general linear model (GLM with two factors and their interactions was applied. Significant effects in dimension and ecological zone were found as well as seven interactions between both factors (p<0.05. Native pastures were used in all farms for grazing. However, small farms’ herds frequently grazed on cultivated pastures and on crop residues (p<0.05. Medium farms showed the highest grazing surface, but in the WT silage and green fodder were used while in the DT dry fodders were used (p<0.001. The interactions between factors showed a bigger specialization in milk production in DT farms, whereas WT farms were more specialized in meat production. The mixed crop-livestock system in tropic region requires an increase in herd size according to farm’s own productive structure, which is strongly influenced by the ecological zone. The systems would improve with the active participation of smallholders to identify and achieve best practices, higher technological adoption level and with an effective support from public and private Institutions.

  8. Magma mixing and crystal exchange at Yellowstone caldera revealed though sub-crystal-scale age, trace-element, and Hf-isotopic analyses of zircons

    Science.gov (United States)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Wimpenny, J.; Yin, Q.

    2011-12-01

    We examine magma mixing and crystal exchange in a young magma reservoir by correlating sub-crystal-scale SIMS age, SIMS trace element, and LA-MC-ICPMS Hf-isotopic data from zircons in the coeval ca. 100ka, yet compositionally distinct rhyolites of the Solfatara Plateau flow (SPF) and Hayden Valley flow (HVF) at Yellowstone Caldera. The SPF and HVF lavas are part of the Central Plateau Member (CPM) of the Plateau Rhyolite that is composed of the youngest intracaldera rhyolite flows at Yellowstone, erupted between ca. 170-70ka. We compare these data to age and trace element data from zircons in 1) the Pitchstone Plateau Flow, West Yellowstone Flow, and Dry Creek Flow of the CPM as representative of main reservoir zircons, 2) the ca. 118ka extracaldera Gibbon River Flow rhyolite (GRF), and 3) the ca. 260ka Scaup Lake Flow of the Upper Basin Member rhyolites. Additionally, we compare the zircon data to new MC-ICPMS Hf-isotopic data from CPM glasses. Correlating age, trace element, and Hf-isotopic data from zircons in the HVF and SPF reveals the presence of four zircon populations. Main reservoir-like (MR-like) zircons have trace element compositions similar to main CPM reservoir zircons, young ages (Lastly, a population of zircons (which we interpret to be inherited) have cores with older ages (>350ka), a range in trace element compositions, and high ɛHf (-5.8 to -3.6) whereas the rims have restricted MR-like trace element compositions and ɛHf within error of CPM glasses. The sense of core to rim zoning specific to each population suggests that each population has its own unique history. The core to rim zoning in MR-like and inherited zircons, from cores with a range of Hf-isotopic compositions to rims similar to CPM glasses, suggests that MR-like and inherited zircons in the SPF and HVF came from distinct high ɛHf magmas and were incorporated into the CPM reservoir. For mixed zircons, the zoning from MR-like or EC-like cores to intermediate rim compositions

  9. Quantifying Flow and Pollutant Loading at Nested-Scales in a Mixed-Land-Use Watershed of the Central United States

    Science.gov (United States)

    Zeiger, S. J.; Hubbart, J. A.

    2016-12-01

    The impacts of land use on flow and pollutant loading regimes are poorly understood in mixed-land-use watersheds. Stream water quantity and quality was monitored using a nested-scale experimental watershed study design in a rapidly urbanizing mixed-land-use watershed of the central USA. Agricultural land use decreased by 18.4% and urban land use increased by 21.6% from the headwaters toward the watershed outlet. Four years of grab samples were collected at each site (n=836 samples per site) and analyzed for suspended sediment, total phosphorus, and inorganic nitrogen species during the study period (2010 - 2013). Daily flow and load duration curves were generated to quantify daily flow and pollutant yields at multiple flow intervals [high flow (0-10%), moist conditions (10-40%), mid-range flows (40-60%), dry conditions (60-90%), and low flow (90-100%)]. Greater than 92.1% of the total pollutant loads were transported during the high flow interval. Less than 0.1% suspended sediments and less than 1.0% TP-P were transported during mid-range conditions. Concentrations of NO3-N exceeding 5.0 mg L-1 were observed during moist conditions when median daily flow was 0.06 m3 s-1 in the headwaters where agricultural land use dominated 57% of the total drainage area (78.9 km2). The eutro-mesotrophic boundary was exceeded by a range of 37.8% (NO3-N in the agricultural headwaters) to 182.2% [(suspended sediment near the watershed outlet where urban land use accounted for 26% of the total drainage area (207.5 km2)] during the high flow interval. The eutro-mesotrophic boundary was exceeded by 56.3% for suspended sediment near the watershed outlet during moist conditions. However, the observed median daily pollutant loading did not exceed the load duration curve below the mid-range flow interval. Results highlight a critical need for pollutant monitoring at multiple flow intervals to capture the variability of pollutant loading in mixed-land-use watersheds.

  10. A Search for New Physics at the TeV Scale Via a Precise Measurement of the Weak Mixing Angle in Moller Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Emam, W.

    2004-11-01

    This dissertation reports on a precise measurement of the parity-violating asymmetry in electron-electron (Moeller) scattering at a four-momentum transfer Q{sup 2} = 0.03 (GeV/c){sup 2}. The observed parity-violating asymmetry is A{sub PV} = -128 {+-} 14 (stat.) {+-} 12 (syst.) x 10{sup -9}. This is the most precise asymmetry ever measured in a parity-violating electron scattering. In the context of the Standard Model, the A{sub PV} result determines the weak mixing angle, which is one of the fundamental parameters of the model. The result is sin{sup 2} {theta}{sub W}{sup eff} = 0.2403 {+-} 0.0014, which is consistent with the Standard Model expectation at the current level of precision. The comparison between this measurement of the weak mixing angle at low Q{sup 2} and at the Z{sup 0} pole establishes the running of sin{sup 2} {theta}{sub W} with 6.5{sigma} significance. In addition, they report on the first observation of a transverse asymmetry in electron-electron scattering. The observed asymmetry is A{sub T}{sup Moeller} = 2.7 x 10{sup -6}, which is consistent with the theoretical predictions. They also provide a new measurement of the transverse asymmetry in ep scattering A{sub T}{sup ep} = 2 x 10{sup -6}. The consistency of the result with the theoretical prediction provides new limits on the TeV scale physics. A limit of 0.9 TeV was set on the mass of the extra Z' boson in the SO(10) Model. A limit of 14 TeV and 6 TeV was set on the compositeness scales {Lambda}{sub ee}{sup +} and {Lambda}{sub ee}{sup -}, respectively. Finally a limit of 0.2 TeV was set on ratio of the doubly-charged Higgs mass to the ee{Delta} coupling g{sub ee{Delta}}{sup 2}/m{sub {delta}}{sup 2}.

  11. Using large eddy simulations to reveal the size, strength, and phase of updraft and downdraft cores of an Arctic mixed-phase stratocumulus cloud

    Science.gov (United States)

    Roesler, Erika L.; Posselt, Derek J.; Rood, Richard B.

    2017-04-01

    Three-dimensional large eddy simulations (LES) are used to analyze a springtime Arctic mixed-phase stratocumulus observed on 26 April 2008 during the Indirect and Semi-Direct Aerosol Campaign. Two subgrid-scale turbulence parameterizations are compared. The first scheme is a 1.5-order turbulent kinetic energy (1.5-TKE) parameterization that has been previously applied to boundary layer cloud simulations. The second scheme, Cloud Layers Unified By Binormals (CLUBB), provides higher-order turbulent closure with scale awareness. The simulations, in comparisons with observations, show that both schemes produce the liquid profiles within measurement variability but underpredict ice water mass and overpredict ice number concentration. The simulation using CLUBB underpredicted liquid water path more than the simulation using the 1.5-TKE scheme, so the turbulent length scale and horizontal grid box size were increased to increase liquid water path and reduce dissipative energy. The LES simulations show this stratocumulus cloud to maintain a closed cellular structure, similar to observations. The updraft and downdraft cores self-organize into a larger meso-γ-scale convective pattern with the 1.5-TKE scheme, but the cores remain more isotropic with the CLUBB scheme. Additionally, the cores are often composed of liquid and ice instead of exclusively containing one or the other. These results provide insight into traditionally unresolved and unmeasurable aspects of an Arctic mixed-phase cloud. From analysis, this cloud's updraft and downdraft cores appear smaller than other closed-cell stratocumulus such as midlatitude stratocumulus and Arctic autumnal mixed-phase stratocumulus due to the weaker downdrafts and lower precipitation rates.

  12. [Validation of the Quality of Life in Alzheimer's Disease (QOL-AD) scale in Mexican patients with Alzheimer, vascular and mixed-type dementia].

    Science.gov (United States)

    Rosas-Carrasco, Oscar; Torres-Arreola, Laura del Pilar; Guerra-Silla, M de Guadalupe; Torres-Castro, Sara; Gutierrez-Robledo, Luis Miguel

    2010-07-16

    To adapt the Quality of Life in Alzheimer's Disease (QOL-AD) scale to Spanish, as well as to evaluate its reliability and validity in Mexico. The study involved a sample of 114 patients diagnosed with Alzheimer, vascular and mixed-type dementia, according to the criteria of the National Institute for Neurological and Communicative Disorders/Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA), the National Institute of Neurological Disorders and Stroke/Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) and the Alzheimer's Disease Diagnostic and Treatment Centers (ADDTC), respectively. Their primary caregivers (n = 114) and a control group (n = 30) of persons aged 60 or over without dementia and their closest relatives were also evaluated. The total group with dementia obtained a mean age and a standard deviation of 80.15 +/- 7.13. The Folstein minimental test was 18.55 +/- 4.99. We obtained a Cronbach's alpha of 0.88 for the patient version of the QOL-AD (QOL-ADp) and 0.82 for the caregiver version of the QOL-AD (QOL-ADc). The test-retest yielded an intraclass correlation coefficient of 0.9 (p dementia and the control group. The QOL-AD yielded satisfactory results in terms of internal and external reliability, validity between measurements and between known groups. Thus, we can recommend its use to evaluate the quality of life of patients with dementia.

  13. A Hybrid Approach Using an Artificial Bee Algorithm with Mixed Integer Programming Applied to a Large-Scale Capacitated Facility Location Problem

    Directory of Open Access Journals (Sweden)

    Guillermo Cabrera G.

    2012-01-01

    Full Text Available We present a hybridization of two different approaches applied to the well-known Capacitated Facility Location Problem (CFLP. The Artificial Bee algorithm (BA is used to select a promising subset of locations (warehouses which are solely included in the Mixed Integer Programming (MIP model. Next, the algorithm solves the subproblem by considering the entire set of customers. The hybrid implementation allows us to bypass certain inherited weaknesses of each algorithm, which means that we are able to find an optimal solution in an acceptable computational time. In this paper we demonstrate that BA can be significantly improved by use of the MIP algorithm. At the same time, our hybrid implementation allows the MIP algorithm to reach the optimal solution in a considerably shorter time than is needed to solve the model using the entire dataset directly within the model. Our hybrid approach outperforms the results obtained by each technique separately. It is able to find the optimal solution in a shorter time than each technique on its own, and the results are highly competitive with the state-of-the-art in large-scale optimization. Furthermore, according to our results, combining the BA with a mathematical programming approach appears to be an interesting research area in combinatorial optimization.

  14. Application of simplified models to CO2 migration and immobilization in large-scale geological systems

    KAUST Repository

    Gasda, Sarah E.

    2012-07-01

    Long-term stabilization of injected carbon dioxide (CO 2) is an essential component of risk management for geological carbon sequestration operations. However, migration and trapping phenomena are inherently complex, involving processes that act over multiple spatial and temporal scales. One example involves centimeter-scale density instabilities in the dissolved CO 2 region leading to large-scale convective mixing that can be a significant driver for CO 2 dissolution. Another example is the potentially important effect of capillary forces, in addition to buoyancy and viscous forces, on the evolution of mobile CO 2. Local capillary effects lead to a capillary transition zone, or capillary fringe, where both fluids are present in the mobile state. This small-scale effect may have a significant impact on large-scale plume migration as well as long-term residual and dissolution trapping. Computational models that can capture both large and small-scale effects are essential to predict the role of these processes on the long-term storage security of CO 2 sequestration operations. Conventional modeling tools are unable to resolve sufficiently all of these relevant processes when modeling CO 2 migration in large-scale geological systems. Herein, we present a vertically-integrated approach to CO 2 modeling that employs upscaled representations of these subgrid processes. We apply the model to the Johansen formation, a prospective site for sequestration of Norwegian CO 2 emissions, and explore the sensitivity of CO 2 migration and trapping to subscale physics. Model results show the relative importance of different physical processes in large-scale simulations. The ability of models such as this to capture the relevant physical processes at large spatial and temporal scales is important for prediction and analysis of CO 2 storage sites. © 2012 Elsevier Ltd.

  15. Simulation of subgrid orographic precipitation with an embedded 2-D cloud-resolving model

    Science.gov (United States)

    Jung, Joon-Hee; Arakawa, Akio

    2016-03-01

    By explicitly resolving cloud-scale processes with embedded two-dimensional (2-D) cloud-resolving models (CRMs), superparameterized global atmospheric models have successfully simulated various atmospheric events over a wide range of time scales. Up to now, however, such models have not included the effects of topography on the CRM grid scale. We have used both 3-D and 2-D CRMs to simulate the effects of topography with prescribed "large-scale" winds. The 3-D CRM is used as a benchmark. The results show that the mean precipitation can be simulated reasonably well by using a 2-D representation of topography as long as the statistics of the topography such as the mean and standard deviation are closely represented. It is also shown that the use of a set of two perpendicular 2-D grids can significantly reduce the error due to a 2-D representation of topography.

  16. Informing the scale-up of Kenya's nursing workforce: a mixed methods study of factors affecting pre-service training capacity and production.

    Science.gov (United States)

    Appiagyei, Ashley A; Kiriinya, Rose N; Gross, Jessica M; Wambua, David N; Oywer, Elizabeth O; Kamenju, Andrew K; Higgins, Melinda K; Riley, Patricia L; Rogers, Martha F

    2014-08-20

    Given the global nursing shortage and investments to scale-up the workforce, this study evaluated trends in annual student nurse enrolment, pre-service attrition between enrolment and registration, and factors that influence nurse production in Kenya. This study used a mixed methods approach with data from the Regulatory Human Resources Information System (tracks initial student enrolment through registration) and the Kenya Health Workforce Information System (tracks deployment and demographic information on licensed nurses) for the quantitative analyses and qualitative data from key informant interviews with nurse training institution educators and/or administrators. Trends in annual student nurse enrolment from 1999 to 2010 were analyzed using regulatory and demographic data. To assess pre-service attrition between training enrolment and registration with the nursing council, data for a cohort that enrolled in training from 1999 to 2004 and completed training by 2010 was analyzed. Multivariate logistic regression was used to test for factors that significantly affected attrition. To assess the capacity of nurse training institutions for scale-up, qualitative data was obtained through key informant interviews. From 1999 to 2010, 23,350 students enrolled in nurse training in Kenya. While annual new student enrolment doubled between 1999 (1,493) and 2010 (3,030), training institutions reported challenges in their capacity to accommodate the increased numbers. Key factors identified by the nursing faculty included congestion at clinical placement sites, limited clinical mentorship by qualified nurses, challenges with faculty recruitment and retention, and inadequate student housing, transportation and classroom space. Pre-service attrition among the cohort that enrolled between 1999 and 2004 and completed training by 2010 was found to be low (6%). To scale-up the nursing workforce in Kenya, concurrent investments in expanding the number of student nurse clinical

  17. Informing the scale-up of Kenya’s nursing workforce: a mixed methods study of factors affecting pre-service training capacity and production

    Science.gov (United States)

    2014-01-01

    Background Given the global nursing shortage and investments to scale-up the workforce, this study evaluated trends in annual student nurse enrolment, pre-service attrition between enrolment and registration, and factors that influence nurse production in Kenya. Methods This study used a mixed methods approach with data from the Regulatory Human Resources Information System (tracks initial student enrolment through registration) and the Kenya Health Workforce Information System (tracks deployment and demographic information on licensed nurses) for the quantitative analyses and qualitative data from key informant interviews with nurse training institution educators and/or administrators. Trends in annual student nurse enrolment from 1999 to 2010 were analyzed using regulatory and demographic data. To assess pre-service attrition between training enrolment and registration with the nursing council, data for a cohort that enrolled in training from 1999 to 2004 and completed training by 2010 was analyzed. Multivariate logistic regression was used to test for factors that significantly affected attrition. To assess the capacity of nurse training institutions for scale-up, qualitative data was obtained through key informant interviews. Results From 1999 to 2010, 23,350 students enrolled in nurse training in Kenya. While annual new student enrolment doubled between 1999 (1,493) and 2010 (3,030), training institutions reported challenges in their capacity to accommodate the increased numbers. Key factors identified by the nursing faculty included congestion at clinical placement sites, limited clinical mentorship by qualified nurses, challenges with faculty recruitment and retention, and inadequate student housing, transportation and classroom space. Pre-service attrition among the cohort that enrolled between 1999 and 2004 and completed training by 2010 was found to be low (6%). Conclusion To scale-up the nursing workforce in Kenya, concurrent investments in expanding the

  18. Super-SILAC mix coupled with SIM/AIMS assays for targeted verification of phosphopeptides discovered in a large-scale phosphoproteome analysis of hepatocellular carcinoma.

    Science.gov (United States)

    Lin, Yu-Tsun; Chien, Kun-Yi; Wu, Chia-Chun; Chang, Wen-Yu; Chu, Lichieh Julie; Chen, Min-Chi; Yeh, Chau-Ting; Yu, Jau-Song

    2017-03-22

    Plentiful studies have established a close association between aberrant phosphorylation and hepatocellular carcinoma (HCC). Here, we applied a quantitative phosphoproteomics platform combining dimethylation labeling and online 3D strong cation exchange chromatography (SCX)-titanium oxide (TiO2)/RP-LTQ-Orbitrap to compare phosphoproteomes between three pairs of HCC tissues and non-tumor counterparts. This analysis yielded 7868 quantifiable phosphopeptides and numerous up- or down-regulated candidates. Increased phosphorylation of LMNA and NIPA was confirmed using specific antibodies. To expand our verification capability, we evaluated the use of LTQ-Orbitrap run in SIM/Accurate inclusion mass screening (AIMS) mode with a super-SILAC mixture as an internal standard to quantify a subset of phosphopeptide candidates in HCC tissue samples. In sample I used for discovery experiment, we successfully quantified 32 (in SIM mode) and 30 (in AIMS mode) phosphopeptides with median coefficients of variation (CVs) of 7.5% and 8.3%, respectively. When the assay was applied to other three pairs of HCC specimens for verification experiment, 40 target phosphopeptides were quantified reliably (~7.5% CV), and more than half of them were differentially expressed between tumor and adjacent non-tumor tissues. Collectively, these results indicate the feasibility of using super-SILAC mix-SIM/AIMS assays for targeted verification of phosphopeptides discovered by large-scale phosphoproteome analyses of HCC specimens. In this study, we developed a strategy for conducting both discovery and targeted verification of deregulated phosphoproteins in HCC tissue specimens on LTQ-Orbitrap. This strategy allowed us to generate a quantitative HCC tissue phosphoproteome dataset containing significantly deregulated phosphoproteins that represents a valuable resource for the identification of potential HCC biomarkers and/or therapeutic targets. Furthermore, our proof-of-concept experiments demonstrated

  19. Renormalization-group theory for the eddy viscosity in subgrid modeling

    Science.gov (United States)

    Zhou, YE; Vahala, George; Hossain, Murshed

    1988-01-01

    Renormalization-group theory is applied to incompressible three-dimensional Navier-Stokes turbulence so as to eliminate unresolvable small scales. The renormalized Navier-Stokes equation now includes a triple nonlinearity with the eddy viscosity exhibiting a mild cusp behavior, in qualitative agreement with the test-field model results of Kraichnan. For the cusp behavior to arise, not only is the triple nonlinearity necessary but the effects of pressure must be incorporated in the triple term. The renormalized eddy viscosity will not exhibit a cusp behavior if it is assumed that a spectral gap exists between the large and small scales.

  20. Sensitivity of the scale partition for variational multiscale large-eddy simulation of channel flow

    OpenAIRE

    Holmen, J; Hughes, T.J.R; Oberai, A.A.; Wells, G. N.

    2004-01-01

    The variational multiscale method has been shown to perform well for large-eddy simulation (LES) of turbulent flows. The method relies upon a partition of the resolved velocity field into large- and small-scale components. The subgrid model then acts only on the small scales of motion, unlike conventional LES models which act on all scales of motion. For homogeneous isotropic turbulence and turbulent channel flows, the multiscale model can outperform conventional LES formulations. An issue in...

  1. Experimental and CFD Studies of Coolant Flow Mixing within Scaled Models of the Upper and Lower Plenums of NGNP Gas-Cooled Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Yassin [Texas A & M Univ., College Station, TX (United States); Anand, Nk [Texas A & M Univ., College Station, TX (United States)

    2016-03-30

    A 1/16th scaled VHTR experimental model was constructed and the preliminary test was performed in this study. To produce benchmark data for CFD validation in the future, the facility was first run at partial operation with five pipes being heated. PIV was performed to extract the vector velocity field for three adjacent naturally convective jets at statistically steady state. A small recirculation zone was found between the pipes, and the jets entered the merging zone at 3 cm from the pipe outlet but diverged as the flow approached the top of the test geometry. Turbulence analysis shows the turbulence intensity peaked at 41-45% as the jets mixed. A sensitivity analysis confirmed that 1000 frames were sufficient to measure statistically steady state. The results were then validated by extracting the flow rate from the PIV jet velocity profile, and comparing it with an analytic flow rate and ultrasonic flowmeter; all flow rates lie within the uncertainty of the other two methods for Tests 1 and 2. This test facility can be used for further analysis of naturally convective mixing, and eventually produce benchmark data for CFD validation for the VHTR during a PCC or DCC accident scenario. Next, a PTV study of 3000 images (1500 image pairs) were used to quantify the velocity field in the upper plenum. A sensitivity analysis confirmed that 1500 frames were sufficient to precisely estimate the flow. Subsequently, three (3, 9, and 15 cm) Y-lines from the pipe output were extracted to consider the output differences between 50 to 1500 frames. The average velocity field and standard deviation error that accrued in the three different tests were calculated to assess repeatability. The error was varied, from 1 to 14%, depending on Y-elevation. The error decreased as the flow moved farther from the output pipe. In addition, turbulent intensity was calculated and found to be high near the output. Reynolds stresses and turbulent intensity were used to validate the data by

  2. USING CMAQ FOR EXPOSURE MODELING AND CHARACTERIZING THE SUB-GRID VARIABILITY FOR EXPOSURE ESTIMATES

    Science.gov (United States)

    Atmospheric processes and the associated transport and dispersion of atmospheric pollutants are known to be highly variable in time and space. Current air quality models that characterize atmospheric chemistry effects, e.g. the Community Multi-scale Air Quality (CMAQ), provide vo...

  3. A New Approach to Validate Subgrid Models in Complex High Reynolds Number Flows

    Science.gov (United States)

    1994-05-01

    data are also shown. These figures show the characteristic decrease in correla- tion when the grid is coarsened with the scale similarity model showing...passmms sogbe .iului by a Pus* dll- apWaishmalm ass" immp to bpssm do af sepia abdas h bell pufai aftg a pmiuayomd NO P) emd a smA amedidg of do @*M

  4. Pilot-scale passive bioreactors for the treatment of acid mine drainage: efficiency of mushroom compost vs. mixed substrates for metal removal.

    Science.gov (United States)

    Song, Hocheol; Yim, Gil-Jae; Ji, Sang-Woo; Neculita, Carmen Mihaela; Hwang, Taewoon

    2012-11-30

    Pilot-scale field-testing of passive bioreactors was performed to evaluate the efficiency of a mixture of four substrates (cow manure compost, mushroom compost, sawdust, and rice straw) relative to mushroom compost alone, and of the effect of the Fe/Mn ratio, during the treatment of acid mine drainage (AMD) over a 174-day period. Three 141 L columns, filled with either mushroom compost or the four substrate mixture (in duplicate), were set-up and fed with AMD from a closed mine site, in South Korea, using a 4-day hydraulic retention time. In the former bioreactor, effluent deterioration was observed over 1-2 months, despite the good efficiency predicted by the physicochemical characterization of mushroom compost. Steady state effluent quality was then noted for around 100 days before worsening in AMD source water occurred in response to seasonal variations in precipitation. Such changes in AMD quality resulted in performance deterioration in all reactors followed by a slow recovery toward the end of testing. Both substrates (mushroom compost and mixtures) gave satisfactory performance in neutralizing pH (6.1-7.8). Moreover, the system was able to consistently reduce sulfate from day 49, after the initial leaching out from organic substrates. Metal removal efficiencies were on the order of Al (∼100%) > Fe (68-92%) > Mn (49-61%). Overall, the mixed substrates showed comparable performance to mushroom compost, while yielding better effluent quality upon start-up. The results also indicated mushroom compost could release significant amounts of Mn and sulfate during bioreactor operation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Physics and dynamics coupling across scales in the next generation CESM: Meeting the challenge of high resolution. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Vincent E.

    2015-02-21

    This is a final report for a SciDAC grant supported by BER. The project implemented a novel technique for coupling small-scale dynamics and microphysics into a community climate model. The technique uses subcolumns that are sampled in Monte Carlo fashion from a distribution of subgrid variability. The resulting global simulations show several improvements over the status quo.

  6. Numerical Methods for the Optimization of Nonlinear Residual-Based Sungrid-Scale Models Using the Variational Germano Identity

    NARCIS (Netherlands)

    Maher, G.D.; Hulshoff, S.J.

    2014-01-01

    The Variational Germano Identity [1, 2] is used to optimize the coefficients of residual-based subgrid-scale models that arise from the application of a Variational Multiscale Method [3, 4]. It is demonstrated that numerical iterative methods can be used to solve the Germano relations to obtain

  7. Why PUB needs scaling

    Science.gov (United States)

    Lovejoy, S.; Schertzer, D.; Hubert, P.; Mouchel, J. M.; Benjoudhi, H.; Tchigurinskaya, Y.; Gaume, E.; Vesseire, J.-M.

    2003-04-01

    Hydrological fields display an extreme variability over a wide range of space-time scales. This variability is beyond the scope of classical mathematical and modeling methods which are forced to combine homogeneity assumptions with scale truncations and subgrid parameterizations. These ad hoc procedures nevertheless lead to complex numerical codes: they are difficult to transfer from one basin to another one, or even to verify with data at a different scale. Tuning the model parameters is hazardous: “predictions” are often reduced to fitting existing observations and are in any case essentially limited to the narrow range of space-time scales over which the parameters have been estimated. In contrast, in recent scaling approaches heterogeneity and uncertainty at all scales are no longer obstacles. The variability is viewed as a consequence of a scale symmetry which must first be elucidated and then exploited: small scale homogeneity assumptions are replaced by small scale heterogeneity assumptions which are verified from data covering wide ranges of scale. PUB provides an unprecedented opportunity not only to test scaling concepts and techniques, but also to development them further. Indeed, PUB can be restated in the following manner: given a partial knowledge on the input (atmospheric states, dynamics and fluxes) and of the media (basin) over a given range of scales, what can we predict for the output (steamflow and water quality) and over which range of scales? We illustrate this state of the art with examples taken from various projects involving precipitation and stream flow collectively spanning the range of scales from centimeters to planetary scales in space, from seconds to tens of years in time.

  8. Characterization of mixing errors in a coupled physical biogeochemical model of the North Atlantic: implications for nonlinear estimation using Gaussian anamorphosis

    Directory of Open Access Journals (Sweden)

    D. Béal

    2010-02-01

    Full Text Available In biogeochemical models coupled to ocean circulation models, vertical mixing is an important physical process which governs the nutrient supply and the plankton residence in the euphotic layer. However, vertical mixing is often poorly represented in numerical simulations because of approximate parameterizations of sub-grid scale turbulence, wind forcing errors and other mis-represented processes such as restratification by mesoscale eddies. Getting a sufficient knowledge of the nature and structure of these errors is necessary to implement appropriate data assimilation methods and to evaluate if they can be controlled by a given observation system.

    In this paper, Monte Carlo simulations are conducted to study mixing errors induced by approximate wind forcings in a three-dimensional coupled physical-biogeochemical model of the North Atlantic with a 1/4° horizontal resolution. An ensemble forecast involving 200 members is performed during the 1998 spring bloom, by prescribing perturbations of the wind forcing to generate mixing errors. The biogeochemical response is shown to be rather complex because of nonlinearities and threshold effects in the coupled model. The response of the surface phytoplankton depends on the region of interest and is particularly sensitive to the local stratification. In addition, the statistical relationships computed between the various physical and biogeochemical variables reflect the signature of the non-Gaussian behaviour of the system. It is shown that significant information on the ecosystem can be retrieved from observations of chlorophyll concentration or sea surface temperature if a simple nonlinear change of variables (anamorphosis is performed by mapping separately and locally the ensemble percentiles of the distributions of each state variable on the Gaussian percentiles. The results of idealized observational updates (performed with perfect observations and neglecting horizontal correlations

  9. Large scale finite element solvers for the large eddy simulation of incompressible turbulent flows

    OpenAIRE

    Colomés Gené, Oriol

    2016-01-01

    In this thesis we have developed a path towards large scale Finite Element simulations of turbulent incompressible flows. We have assessed the performance of residual-based variational multiscale (VMS) methods for the large eddy simulation (LES) of turbulent incompressible flows. We consider VMS models obtained by different subgrid scale approximations which include either static or dynamic subscales, linear or nonlinear multiscale splitting, and different choices of the subscale space. W...

  10. Effective Momentum and heat flux models for simulation of stratification and mixing in a large pool of water

    Energy Technology Data Exchange (ETDEWEB)

    Hua Li; Villanueva, W.; Kudinov, P. [Royal Institute of Technology (KTH). Div. of Nuclear Power Safety, Stockholm (Sweden)

    2012-06-15

    Performance of a boiling water reactor (BWR) containment is mostly determined by reliable operation of pressure suppression pool which serves as a heat sink to cool and condense steam released from the core vessel. Thermal stratification in the pool can significantly impede the pool's pressure suppression capacity. A source of momentum is required in order to break stratification and mix the pool. It is important to have reliable prediction of transient development of stratification and mixing in the pool in different regimes of steam injection. Previously, we have proposed to model the effect of steam injection on the mixing and stratification with the Effective Heat Source (EHS) and the Effective Momentum Source (EMS) models. The EHS model is used to provide thermal effect of steam injection on the pool, preserving heat and mass balance. The EMS model is used to simulate momentum induced by steam injection in different flow regimes. The EMS model is based on the combination of (1) synthetic jet theory, which predicts effective momentum if amplitude and frequency of flow oscillations in the pipe are given, and (2) model proposed by Aya and Nariai for prediction of the amplitude and frequency of oscillations at a given pool temperature and steam mass flux. The complete EHS/EMS models only require the steam mass flux, initial pool bulk temperature, and design-specific parameters, to predict thermal stratification and mixing in a pressure suppression pool. In this work we use EHS/EMS models implemented in containment thermal hydraulic code GOTHIC. The POOLEX/PPOOLEX experiments (Lappeenranta University of Technology, Finland) are utilized, to (a) quantify errors due to GOTHIC's physical models and numerical schemes, (b) propose necessary improvements in GOTHIC sub-grid scale modeling, and (c) validate our proposed models. Specifically the data from POOLEX STB-21 and PPOOLEX STR-03 and STR-04 tests are used for validation of the EHS and EMS models in this

  11. Energy savings by reduced mixing in aeration tanks: Results from a full scale investigation and long term implementation at Avedoere wastewater treatment plant

    DEFF Research Database (Denmark)

    Sharma, Anitha Kumari; Guildal, T.; Thomsen, H.R.

    2011-01-01

    investigation was conducted to study the effect of reduced mixing on flow velocity, suspended solid sedimentation, concentration gradients of oxygen and SS with depth and treatment efficiency. The only negative effect observed was on flow velocity; however the velocity was above the critical velocity. The plant...

  12. Study on the Effect of Jet Velocity on Mixing Performance and Sludge Prevention in Large-Scale Crude-Oil Tanks by the CFD Technique

    Directory of Open Access Journals (Sweden)

    Ali Akbar Lotfi Neyestanak

    2017-06-01

    Full Text Available In this paper, computational fluid dynamic modelling was developed to study the effect of the floating jet velocity or submerged rotary jet in sludge prevention in a large crude-oil storage tank. The Euler-Euler method was used in a two-dimensional CFD model to describe oil and sludge flow behaviour at the bottom of the storage tank. By modifying some parameters, the k-e model was used to describe the turbulence of the mixing flow. The results show the effect of jet velocity, angle, and time on the mixing process. By increasing the velocity from 5 m s−1, the mixing pattern significantly changes and improves the mixing of the sludge with crude oil. To evaluate the results, chosen was the sludge profile related to the bottom of the sample tank, and modelling results showed an 80 cm reduction in thickness of the sludge, which corresponds well to the profile of the bottom of the tank. In addition, the y+ axis indicated that the amounts at all points were less than 300, which is acceptable in two-phase modelling.

  13. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    Science.gov (United States)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  14. SUPECA kinetics for scaling redox reactions in networks of mixed substrates and consumers and an example application to aerobic soil respiration

    National Research Council Canada - National Science Library

    Tang, Jin-Yun; Riley, William J

    2017-01-01

    .... However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities...

  15. Modeling of condensation, stratification, and mixing phenomena in a pool of water

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Kudinov, P.; Villanueva, W. (Royal Institute of Technology (KTH). Div. of Nuclear Power Safety, Stockholm (Sweden))

    2010-12-15

    This work pertains to the research program on Containment Thermal-Hydraulics at KTH. The objective is to evaluate and improve performance of methods, which are used to analyze thermal-hydraulics of steam suppression pools in a BWR plant under different abnormal transient and accident conditions. As a passive safety system, the function of steam pressure suppression pools is paramount to the containment performance. In the present work, the focus is on apparently-benign but intricate and potentially risk-significant scenarios in which thermal stratification could significantly impede the pool's pressure suppression capacity. For the case of small flow rates of steam influx, the steam condenses rapidly in the pool and the hot condensate rises in a narrow plume above the steam injection plane and spreads into a thin layer at the pool's free surface. When the steam flow rate increases significantly, momentum introduced by the steam injection and/or periodic expansion and shrink of large steam bubbles due to direct contact condensation can cause breakdown of the stratified layers and lead to mixing of the pool water. Accurate prediction of the pool thermal-hydraulics in such scenarios presents a computational challenge. Lumped-parameter models have no capability to predict temperature distribution of water pool during thermal stratification development. While high-order-accurate CFD (RANS, LES) methods are not practical due to excessive computing power needed to calculate 3D high-Rayleighnumber natural circulation flow in long transients. In the present work, a middleground approach is used, namely CFD-like model of the general purpose thermalhydraulic code GOTHIC. Each cell of 3D GOTHIC grid uses lumped parameter volume type closures for modeling of various heat and mass transfer processes at subgrid scale. We use GOTHIC to simulate POOLEX/PPOOLEX experiment, in order to (a) quantify errors due to GOTHIC's physical models and numerical schemes, and (b

  16. Multi-scale habitat relationships of snowshoe hares (Lepus americanus) in the mixed conifer landscape of the Northern Rockies, USA: Cross-scale effects of horizontal cover with implications for forest management

    Science.gov (United States)

    Joseph D. Holbrook; John R. Squires; Lucretia E. Olson; Rick L. Lawrence; Shannon L. Savage

    2016-01-01

    Snowshoe hares (Lepus americanus) are an ecologically important herbivore because they modify vegetation through browsing and serve as a prey resource for multiple predators. We implemented a multiscale approach to characterize habitat relationships for snowshoe hares across the mixed conifer landscape of the northern Rocky Mountains, USA. Our objectives were to (1)...

  17. Mixing and turbulent mixing in fluids, plasma and materials: summary of works presented at the 3rd International Conference on Turbulent Mixing and Beyond

    Science.gov (United States)

    Gauthier, Serge; Keane, Christopher J.; Niemela, Joseph J.; Abarzhi, Snezhana I.

    2013-07-01

    on 'Universal magnetohydrodynamic turbulence and small-scale dynamo', Blackman on 'Accretion disks and dynamos: toward a unified mean field theory', Frederiksen et al on 'Stochastic subgrid parameterizations for atmospheric and oceanic flows', Grinstein et al 'On coarse-grained simulations of turbulent material mixing', Klimenko on 'Mixing, entropy and competition', Smalyuk on 'Experimental techniques for measuring Rayleigh-Taylor instability in inertial confinement fusion', and Sugiyama on 'Intrinsic stochasticity in fusion plasmas'. In particular, Beresnyak reviews the universal magneto-hydrodynamic scenario and small-scale dynamo (including the measurement of its efficiency), Kolmogorov constant and anisotropy constant in high-resolution direct numerical simulations. Blackman discusses recent developments in the theory of accretion disks and dynamos, and proposes a potential path toward a unified mean field theory of these astrophysical phenomena. Frederiksen et al discusses novel approaches to stochastic sub-grid parameterizations for atmospheric and oceanic flows. Grinstein et al discuss numerical approaches for turbulent material mixing that employ coarse-grained simulations. Klimenko presents a new general framework for studies of competitive mixing and non-traditional thermodynamics that can be applied to random behavior associated with turbulence, mixing and competition. Smalyuk discusses the advancements in experimental diagnostics of Rayleigh-Taylor instability in inertial confinement fusion. Sugiyama reviews magnetic fusion and discusses stochastic processes and intrinsic stochasticity in fusion plasmas. Conclusion . In conclusion, the authors hope that this new Topical Issue will continue to serve for exposure of the state-of-the-art in recent theoretical, experimental and numerical developments in 'Turbulent Mixing and Beyond' phenomena to a broad scientific community, for integration of our knowledge of the subject and for further enrichment of its

  18. The role of dissipation and mixing in exchange flow through a contracting channel

    Science.gov (United States)

    Winters, Kraig B.; Seim, Harvey E.

    2000-03-01

    We investigate the transport of mass and momentum between layers in idealized exchange flow through a contracting channel. Lock-exchange initial value problems are run to approximately steady state using a three-dimensional, non-hydrostatic numerical model. The numerical model resolves the large-scale exchange flow and shear instabilities that form at the interface, parameterizing the effects of subgrid-scale turbulence. The closure scheme is based on an assumed steady, local balance of turbulent production and dissipation in a density-stratified fluid.

  19. A small scale intercalibration study on organobromine compounds in Japan. Results on brominated dioxins, mixed halogenated dioxins and brominated flame retardants

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, S.; Sakai, Shin-ichi [National Institute for Environmental Studies, Tsukuba (Japan); Watanabe, I. [Osaka Prefectural Institute of Public Health, Osaka (Japan)

    2004-09-15

    Recently, environmental problems relating to brominated flame retardants (BFRs) have become a matter of great concern due to their potential toxic risk on human and wildlife and recent increase in levels of polybrominated diphenyl ethers (PBDEs). Many laboratories have started work on PBDEs and other BFRs such as tetrabromo-bisphenol A (TBBPA), tribromophenol (TBP) and hexabromocyclododecane (HBCD). International intercalibration studies on the analysis of PBDEs have been conducted. The results of intercalibration studies indicated that determination of some higher brominated diphenyl ethers such as BDEs 183 and 209 was not under the control in most laboratories although these compounds are major in commercial Octa- and Deca- BDE products. Moreover, results on BFRs other than PBDEs are very much limited. Another concern has been related to the thermal breakdown products of BFRs such as polybrominated and mixed brominated/chlorinated dibenzo-p-dioxins and dibenzofurans (PBDDs/DFs and mixed PXDDs/DFs). Considerable levels (ppm or even higher) of PBDDs/DFs were detected in waste television cabinets and other flame-retarded plastics. Based on 'the Law Concerning Special Measures against Dioxins (applied since January 2000)', the Ministry of the Environment, Japan is working to promote studies on brominated dioxins, and conducted a pilot survey in the environment8. PBDDs/DFs and monobromo-polychloro dibenzo-p-dioxins and dibenzofurans (MoBPCDDs/DFs) were found in various environmental media with BFRs. Although commercially available standards for these compounds are still limited, development of a good QA/QC system has become imperative. To evaluate the accuracy and reliability in the analysis for organobromine compounds, an intercalibration study in which 10 laboratories in Japan participated was initiated since April, 2003. In this presentation, the results on PBDD/DFs, MoBPCDDs/DFs and PBDEs, in 'Mixed Standard Solutions' and &apos

  20. Study on the Effect of Jet Velocity on Mixing Performance and Sludge Prevention in Large-Scale Crude-Oil Tanks by the CFD Technique

    OpenAIRE

    Ali Akbar Lotfi Neyestanak; Mohammad Reza Tarybakhsh; Saeed Daneshmand

    2017-01-01

    In this paper, computational fluid dynamic modelling was developed to study the effect of the floating jet velocity or submerged rotary jet in sludge prevention in a large crude-oil storage tank. The Euler-Euler method was used in a two-dimensional CFD model to describe oil and sludge flow behaviour at the bottom of the storage tank. By modifying some parameters, the k-e model was used to describe the turbulence of the mixing flow. The results show the effect of jet velocity, angle, and time ...

  1. Indicators of burn severity at extended temporal scales: a decade of ecosystem response in mixed-conifer forests of western Montana

    Science.gov (United States)

    Sarah A. Lewis; Andrew T. Hudak; Peter R. Robichaud; Penelope Morgan; Kevin L. Satterberg; Eva K. Strand; Alistair M. S. Smith; Joseph A. Zamudio; Leigh B. Lentile

    2017-01-01

    We collected field and remotely sensed data spanning 10 years after three 2003 Montana wildfires to monitor ecological change across multiple temporal and spatial scales. Multiple endmember spectral mixture analysis was used to create post-fire maps of: char, soil, green (GV) and non-photosynthetic (NPV) vegetation from high-resolution 2003 hyperspectral (HS) and 2007...

  2. Comparison of three methods to derive canopy-scale flux measurements above a mixed oak and hornbeam forest in Northern Italy

    Science.gov (United States)

    Acton, William; Schallhart, Simon; Langford, Ben; Valach, Amy; Rantala, Pekka; Fares, Silvano; Carriero, Giulia; Mentel, Thomas; Tomlinson, Sam; Dragosits, Ulrike; Hewitt, Nicholas; Nemitz, Eiko

    2015-04-01

    Plants emit a wide range of Biogenic Volatile Organic Compounds (BVOCs) into the atmosphere. These BVOCs are a major source of reactive carbon into the troposphere and play an important role in atmospheric chemistry by, for example, acting as an OH sink and contributing to the formation of secondary organic aerosol. While the emission rates of some of these compounds are relatively well understood, large uncertainties are still associated with the emission estimates of many compounds. Here the fluxes and mixing ratios of BVOCs recorded during June/July 2012 over the Bosco Fontana forest reserve in northern Italy are reported and discussed, together with a comparison of three methods of flux calculation. This work was carried out as a part of the EC FP7 project ECLAIRE (Effects of Climate Change on Air Pollution and Response Strategies for European Ecosystems). The Bosco Fontana reserve is a semi natural deciduous forest dominated by Carpinus betulus (hornbeam), Quercus robur (pedunculate oak) and Quercus rubra (northern red oak). Virtual disjunct eddy covariance measurements made using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS) were used to calculate fluxes and mixing ratios of BVOCs above the forest canopy at Bosco Fontana. BVOC mixing ratios were dominated by methanol with acetaldehyde, acetone, acetic acid, isoprene, the sum of methyl vinyl ketone and methacrolein, methyl ethyl ketone and monoterpenes also recorded. A large flux of isoprene was observed as well as significant fluxes of monoterpenes, methanol, acetaldehyde and methyl vinyl ketone / methacrolein. The fluxes recorded using the PTR-MS and PTR-ToF-MS showed good agreement. Comparison of the isoprene fluxes calculated using these instruments also agreed well with fluxes modelled using the MEGAN algorithms (Guenther et al. 2006). The detailed tree distribution maps for the forest at Bosco Fontana compiled by Dalponte et

  3. Collaborative Research: Quantifying the Uncertainties of Aerosol Indirect Effects and Impacts on Decadal-Scale Climate Variability in NCAR CAM5 and CESM1

    Energy Technology Data Exchange (ETDEWEB)

    Nenes, Athanasios [Georgia Inst. of Technology, Atlanta, GA (United States)

    2017-06-23

    The goal of this proposed project is to assess the climatic importance and sensitivity of aerosol indirect effect (AIE) to cloud and aerosol processes and feedbacks, which include organic aerosol hygroscopicity, cloud condensation nuclei (CCN) activation kinetics, Giant CCN, cloud-scale entrainment, ice nucleation in mixed-phase and cirrus clouds, and treatment of subgrid variability of vertical velocity. A key objective was to link aerosol, cloud microphysics and dynamics feedbacks in CAM5 with a suite of internally consistent and integrated parameterizations that provide the appropriate degrees of freedom to capture the various aspects of the aerosol indirect effect. The proposal integrated new parameterization elements into the cloud microphysics, moist turbulence and aerosol modules used by the NCAR Community Atmospheric Model version 5 (CAM5). The CAM5 model was then used to systematically quantify the uncertainties of aerosol indirect effects through a series of sensitivity tests with present-day and preindustrial aerosol emissions. New parameterization elements were developed as a result of these efforts, and new diagnostic tools & methodologies were also developed to quantify the impacts of aerosols on clouds and climate within fully coupled models. Observations were used to constrain key uncertainties in the aerosol-cloud links. Advanced sensitivity tools were developed and implements to probe the drivers of cloud microphysical variability with unprecedented temporal and spatial scale. All these results have been published in top and high impact journals (or are in the final stages of publication). This proposal has also supported a number of outstanding graduate students.

  4. Mixing navigation on networks

    Science.gov (United States)

    Zhou, Tao

    2008-05-01

    In this article, we propose a mixing navigation mechanism, which interpolates between random-walk and shortest-path protocol. The navigation efficiency can be remarkably enhanced via a few routers. Some advanced strategies are also designed: For non-geographical scale-free networks, the targeted strategy with a tiny fraction of routers can guarantee an efficient navigation with low and stable delivery time almost independent of network size. For geographical localized networks, the clustering strategy can simultaneously increase efficiency and reduce the communication cost. The present mixing navigation mechanism is of significance especially for information organization of wireless sensor networks and distributed autonomous robotic systems.

  5. SUPECA kinetics for scaling redox reactions in networks of mixed substrates and consumers and an example application to aerobic soil respiration

    Directory of Open Access Journals (Sweden)

    J.-Y. Tang

    2017-09-01

    Full Text Available Several land biogeochemical models used for studying carbon–climate feedbacks have begun explicitly representing microbial dynamics. However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities, and interactions with plants and mineral soils. We focus here on developing a mathematical formulation of the substrate–consumer relationships for consumer-mediated redox reactions of the form A + BE→  products, where products could be, e.g., microbial biomass or bioproducts. Under the quasi-steady-state approximation, these substrate–consumer relationships can be formulated as the computationally difficult full equilibrium chemistry problem or approximated analytically with the dual Monod (DM or synthesizing unit (SU kinetics. We find that DM kinetics is scaling inconsistently for reaction networks because (1 substrate limitations are not considered, (2 contradictory assumptions are made regarding the substrate processing rate when transitioning from single- to multi-substrate redox reactions, and (3 the product generation rate cannot be scaled from one to multiple substrates. In contrast, SU kinetics consistently scales the product generation rate from one to multiple substrates but predicts unrealistic results as consumer abundances reach large values with respect to their substrates. We attribute this deficit to SU's failure to incorporate substrate limitation in its derivation. To address these issues, we propose SUPECA (SU plus the equilibrium chemistry approximation – ECA kinetics, which consistently imposes substrate and consumer mass balance constraints. We show that SUPECA kinetics satisfies the partition principle, i.e., scaling invariance across a network of an arbitrary number of reactions (e.g., as in Newton's law of motion and Dalton's law of partial pressures. We tested SUPECA kinetics

  6. SUPECA kinetics for scaling redox reactions in networks of mixed substrates and consumers and an example application to aerobic soil respiration

    Science.gov (United States)

    Tang, Jin-Yun; Riley, William J.

    2017-09-01

    Several land biogeochemical models used for studying carbon-climate feedbacks have begun explicitly representing microbial dynamics. However, to our knowledge, there has been no theoretical work on how to achieve a consistent scaling of the complex biogeochemical reactions from microbial individuals to populations, communities, and interactions with plants and mineral soils. We focus here on developing a mathematical formulation of the substrate-consumer relationships for consumer-mediated redox reactions of the form A + BE→ products, where products could be, e.g., microbial biomass or bioproducts. Under the quasi-steady-state approximation, these substrate-consumer relationships can be formulated as the computationally difficult full equilibrium chemistry problem or approximated analytically with the dual Monod (DM) or synthesizing unit (SU) kinetics. We find that DM kinetics is scaling inconsistently for reaction networks because (1) substrate limitations are not considered, (2) contradictory assumptions are made regarding the substrate processing rate when transitioning from single- to multi-substrate redox reactions, and (3) the product generation rate cannot be scaled from one to multiple substrates. In contrast, SU kinetics consistently scales the product generation rate from one to multiple substrates but predicts unrealistic results as consumer abundances reach large values with respect to their substrates. We attribute this deficit to SU's failure to incorporate substrate limitation in its derivation. To address these issues, we propose SUPECA (SU plus the equilibrium chemistry approximation - ECA) kinetics, which consistently imposes substrate and consumer mass balance constraints. We show that SUPECA kinetics satisfies the partition principle, i.e., scaling invariance across a network of an arbitrary number of reactions (e.g., as in Newton's law of motion and Dalton's law of partial pressures). We tested SUPECA kinetics with the equilibrium chemistry

  7. A sub-grid, mixture-fraction-based thermodynamic equilibrium model for gas phase combustion in FIRETEC: development and results

    Science.gov (United States)

    M. M. Clark; T. H. Fletcher; R. R. Linn

    2010-01-01

    The chemical processes of gas phase combustion in wildland fires are complex and occur at length-scales that are not resolved in computational fluid dynamics (CFD) models of landscape-scale wildland fire. A new approach for modelling fire chemistry in HIGRAD/FIRETEC (a landscape-scale CFD wildfire model) applies a mixture– fraction model relying on thermodynamic...

  8. ADVANCED MIXING MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S; Richard Dimenna, R; David Tamburello, D

    2008-11-13

    The process of recovering the waste in storage tanks at the Savannah River Site (SRS) typically requires mixing the contents of the tank with one to four dual-nozzle jet mixers located within the tank. The typical criteria to establish a mixed condition in a tank are based on the number of pumps in operation and the time duration of operation. To ensure that a mixed condition is achieved, operating times are set conservatively long. This approach results in high operational costs because of the long mixing times and high maintenance and repair costs for the same reason. A significant reduction in both of these costs might be realized by reducing the required mixing time based on calculating a reliable indicator of mixing with a suitably validated computer code. The work described in this report establishes the basis for further development of the theory leading to the identified mixing indicators, the benchmark analyses demonstrating their consistency with widely accepted correlations, and the application of those indicators to SRS waste tanks to provide a better, physically based estimate of the required mixing time. Waste storage tanks at SRS contain settled sludge which varies in height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. If shorter mixing times can be shown to support Defense Waste Processing Facility (DWPF) or other feed requirements, longer pump lifetimes can be achieved with associated operational cost and

  9. ADVANCED MIXING MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S; Dimenna, R; Tamburello, D

    2011-02-14

    height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. One of the main objectives in the waste processing is to provide feed of a uniform slurry composition at a certain weight percentage (e.g. typically {approx}13 wt% at SRS) over an extended period of time. In preparation of the sludge for slurrying, several important questions have been raised with regard to sludge suspension and mixing of the solid suspension in the bulk of the tank: (1) How much time is required to prepare a slurry with a uniform solid composition? (2) How long will it take to suspend and mix the sludge for uniform composition in any particular waste tank? (3) What are good mixing indicators to answer the questions concerning sludge mixing stated above in a general fashion applicable to any waste tank/slurry pump geometry and fluid/sludge combination?

  10. Cloud-scale model intercomparison of chemical constituent transport in deep convection

    Directory of Open Access Journals (Sweden)

    M. C. Barth

    2007-09-01

    Full Text Available Transport and scavenging of chemical constituents in deep convection is important to understanding the composition of the troposphere and therefore chemistry-climate and air quality issues. High resolution cloud chemistry models have been shown to represent convective processing of trace gases quite well. To improve the representation of sub-grid convective transport and wet deposition in large-scale models, general characteristics, such as species mass flux, from the high resolution cloud chemistry models can be used. However, it is important to understand how these models behave when simulating the same storm. The intercomparison described here examines transport of six species. CO and O3, which are primarily transported, show good agreement among models and compare well with observations. Models that included lightning production of NOx reasonably predict NOx mixing ratios in the anvil compared with observations, but the NOx variability is much larger than that seen for CO and O3. Predicted anvil mixing ratios of the soluble species, HNO3, H2O2, and CH2O, exhibit significant differences among models, attributed to different schemes in these models of cloud processing including the role of the ice phase, the impact of cloud-modified photolysis rates on the chemistry, and the representation of the species chemical reactivity. The lack of measurements of these species in the convective outflow region does not allow us to evaluate the model results with observations.

  11. Mixed Movements

    DEFF Research Database (Denmark)

    Brabrand, Helle

    2010-01-01

    levels than those related to building, and this exploration is a special challenge and competence implicit artistic development work. The project Mixed Movements generates drawing-material, not primary as representation, but as a performance-based media, making the body being-in-the-media felt and appear......Mixed Movements is a research project engaged in performance-based architectural drawing. Architectonic implementation questions relations between the human body and a body of architecture by the different ways we handle drawing materials. A drawing may explore architectonic problems at other...

  12. Development and validation of effective models for simulation of stratification and mixing phenomena in a pool of water

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Kudinov, P.; Villanueva, W. (Royal Institute of Technology (KTH). Div. of Nuclear Power Safety (Sweden))

    2011-06-15

    's physical models and numerical schemes, (b) propose necessary improvements in GOTHIC sub-grid scale modeling, and (c) to validate proposed models. Results obtained with the EHS model shows that GOTHIC can predict development of thermal stratification in the pool if adequate grid resolution is provided. An equation for the effective momentum is proposed based on feasibility studies of the EMS model and analysis of the measured data in the test with chugging regime of steam injection. An experiment with higher resolution in space and time of oscillatory flow inside the blowdown pipe is highly desirable to uniquely determine model coefficients. Implementation of EHS/EMS model in GOTHIC and their validation against new PPOOLEX experiment is underway. (Author)

  13. Mixed parentage

    DEFF Research Database (Denmark)

    Bang Appel, Helene; Singla, Rashmi

    2016-01-01

    Despite an increase in cross border intimate relationships and children of mixed parentage, there is little mention or scholarship about them in the area of childhood and migrancy in the Nordic countries. The international literature implies historical pathologisation, contestation and current...

  14. Mixed segmentation

    DEFF Research Database (Denmark)

    Hansen, Allan Grutt; Bonde, Anders; Aagaard, Morten

    This book is about using recent developments in the fields of data analytics and data visualization to frame new ways of identifying target groups in media communication. Based on a mixed-methods approach, the authors combine psychophysiological monitoring (galvanic skin response) with textual...

  15. Restricting 32-128 km horizontal scales hardly affects the MJO in the Superparameterized Community Atmosphere Model v.3.0 but the number of cloud-resolving grid columns constrains vertical mixing

    Science.gov (United States)

    Pritchard, Michael S.; Bretherton, Christopher S.; DeMott, Charlotte A.

    2014-09-01

    The effects of artificially restricting the 32-128 km horizontal scale regime on MJO dynamics in the Superparameterized Community Atmosphere Model v.3.0 have been explored through reducing the extent of its embedded cloud resolving model (CRM) arrays. Two and four-fold reductions in CRM extent (from 128 to 64 km and 32 km) produce statistical composite MJO signatures with spatial scale, zonal phase speed, and intrinsic wind-convection anomaly structure that are all remarkably similar to the standard SPCAM's MJO. This suggests that the physics of mesoscale convective organization on 32-128 km scales are not critical to MJO dynamics in SPCAM and that reducing CRM extent may be a viable strategy for 400% more computationally efficient analysis of superparameterized MJO dynamics. However several unexpected basic state responses caution that extreme CRM domain reduction can lead to systematic mean state issues in superparameterized models. We hypothesize that an artificial limit on the efficiency of vertical updraft mixing is set by the number of grid columns available for compensating subsidence in the embedded CRM arrays. This can lead to reduced moisture ventilation supporting too much liquid cloud and thus an overly strong cloud shortwave radiative forcing, particularly in regions of deep convection.

  16. Blended e-learning and end of life care in nursing homes: a small-scale mixed-methods case study.

    Science.gov (United States)

    Farrington, Conor Jt

    2014-01-01

    A 'blended' (e-learning and facilitated workshops) training course for Group C staff (i.e. staff with relatively infrequent contact with end of life care) has been delivered across several English counties with the aim of improving end of life care in nursing and residential care homes. This paper evaluates the impact of the course on participants' understandings of and confidence in delivering end of life care in one nursing home, while also considering barriers to change in practice. A mixed-methods case study approach, incorporating pre- and post-course questionnaires (SHA East of England End of Life Care Education Programme 'ABC' Project Work Force C or Non Nurse Workforce B Pre and Post Course Questionnaire; E-Learning in End of Life Care Study Pre and Post Course Questionnaire), documentary analysis, semi-structured interviews, and observation of course workshops. Participants were 20 members of staff at a nursing home in a city in the East of England, including 14 Health Care Assistants (carers) and 6 others (administrative, activities, hosting, and catering staff). The questionnaires and interviews assessed understandings of and confidence towards end of life care delivery. Improvements in participants' confidence in delivering end of life care were observed, particularly in the core competency areas of symptom management, communication, and advance care planning. A shift towards more detailed and more holistic understandings of end of life care was in evidence; some participants also championed end of life care in the home as a result of the course. Several barriers to changes in practice were encountered, including uneven participation, the absence of mechanisms for disseminating new insights and knowledge within the home, and a widespread perception that nurses' professional dominance in the home made sustainable change difficult to enact. While blended e-learning courses have the potential to generate positive change in participants' understandings of

  17. Sub-Grid-Scale Description of Turbulent Magnetic Reconnection in Magnetohydrodynamics

    CERN Document Server

    Widmer, Fabien; Yokoi, Nobumitsu

    2015-01-01

    Magnetic reconnection requires, at least locally, a non-ideal plasma response. In collisionless space and astrophysical plasmas, turbulence could permit this instead of the too rare binary collisions. We investigated the influence of turbulence on the reconnection rate in the framework of a single fluid compressible MHD approach. The goal is to find out, whether unresolved, sub-grid for MHD simulations, turbulence can enhance the reconnection process in high Reynolds number astrophysical plasma. We solve, simultaneously with the grid-scale MHD equations, evolution equations for the sub-grid turbulent energy and cross helicity according to Yokoi's model (Yokoi (2013)) where turbulence is self-generated and -sustained through the inhomogeneities of the mean fields. Simulations of Harris and force free sheets confirm the results of Higashimori et al. (2013) and new results are obtained about the dependence on resistivity for large Reynolds number as well as guide field effects. The amount of energy transferred f...

  18. Effect of aerosol subgrid variability on aerosol optical depth and cloud condensation nuclei: Implications for global aerosol modelling

    NARCIS (Netherlands)

    Weigum, Natalie; Schutgens, Nick; Stier, Philip

    2016-01-01

    A fundamental limitation of grid-based models is their inability to resolve variability on scales smaller than a grid box. Past research has shown that significant aerosol variability exists on scales smaller than these grid-boxes, which can lead to discrepancies in simulated aerosol climate effects

  19. Mixed-Method Quasi-Experimental Study of Outcomes of a Large-Scale Multilevel Economic and Food Security Intervention on HIV Vulnerability in Rural Malawi.

    Science.gov (United States)

    Weinhardt, Lance S; Galvao, Loren W; Yan, Alice F; Stevens, Patricia; Mwenyekonde, Thokozani Ng'ombe; Ngui, Emmanuel; Emer, Lindsay; Grande, Katarina M; Mkandawire-Valhmu, Lucy; Watkins, Susan C

    2017-03-01

    The objective of the Savings, Agriculture, Governance, and Empowerment for Health (SAGE4Health) study was to evaluate the impact of a large-scale multi-level economic and food security intervention on health outcomes and HIV vulnerability in rural Malawi. The study employed a quasi-experimental non-equivalent control group design to compare intervention participants (n = 598) with people participating in unrelated programs in distinct but similar geographical areas (control, n = 301). We conducted participant interviews at baseline, 18-, and 36-months on HIV vulnerability and related health outcomes, food security, and economic vulnerability. Randomly selected households (n = 1002) were interviewed in the intervention and control areas at baseline and 36 months. Compared to the control group, the intervention led to increased HIV testing (OR 1.90; 95 % CI 1.29-2.78) and HIV case finding (OR = 2.13; 95 % CI 1.07-4.22); decreased food insecurity (OR = 0.74; 95 % CI 0.63-0.87), increased nutritional diversity, and improved economic resilience to shocks. Most effects were sustained over a 3-year period. Further, no significant differences in change were found over the 3-year study period on surveys of randomly selected households in the intervention and control areas. Although there were general trends toward improvement in the study area, only intervention participants' outcomes were significantly better. Results indicate the intervention can improve economic and food security and HIV vulnerability through increased testing and case finding. Leveraging the resources of economic development NGOs to deliver locally-developed programs with scientific funding to conduct controlled evaluations has the potential to accelerate the scientific evidence base for the effects of economic development programs on health.

  20. Collaborative Project: High-resolution Global Modeling of the Effects of Subgrid-Scale Clouds and Turbulence on Precipitating Cloud Systems

    Energy Technology Data Exchange (ETDEWEB)

    Randall, David A. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Atmospheric Science

    2015-11-01

    We proposed to implement, test, and evaluate recently developed turbulence parameterizations, using a wide variety of methods and modeling frameworks together with observations including ARM data. We have successfully tested three different turbulence parameterizations in versions of the Community Atmosphere Model: CLUBB, SHOC, and IPHOC. All three produce significant improvements in the simulated climate. CLUBB will be used in CAM6, and also in ACME. SHOC is being tested in the NCEP forecast model. In addition, we have achieved a better understanding of the strengths and limitations of the PDF-based parameterizations of turbulence and convection.

  1. Evaluation of the Transport and Diffusion of Pollutants over an Urban Area Using a Local-Scale Advection-Diffusion Model and a Sub-Grid Street Model

    DEFF Research Database (Denmark)

    Salerno, R.; Vignati, E.

    1994-01-01

    Fifth International Conference on the Development and Application of Computer Techniques to Environmental Studies, Envirosoft/94.......Fifth International Conference on the Development and Application of Computer Techniques to Environmental Studies, Envirosoft/94....

  2. Final Technical Report for "High-resolution global modeling of the effects of subgrid-scale clouds and turbulence on precipitating cloud systems"

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Vincent [Univ. of Wisconsin, Milwaukee, WI (United States)

    2016-11-25

    The Multiscale Modeling Framework (MMF) embeds a cloud-resolving model in each grid column of a General Circulation Model (GCM). A MMF model does not need to use a deep convective parameterization, and thereby dispenses with the uncertainties in such parameterizations. However, MMF models grossly under-resolve shallow boundary-layer clouds, and hence those clouds may still benefit from parameterization. In this grant, we successfully created a climate model that embeds a cloud parameterization (“CLUBB”) within a MMF model. This involved interfacing CLUBB’s clouds with microphysics and reducing computational cost. We have evaluated the resulting simulated clouds and precipitation with satellite observations. The chief benefit of the project is to provide a MMF model that has an improved representation of clouds and that provides improved simulations of precipitation.

  3. Rapid mixing kinetic techniques.

    Science.gov (United States)

    Martin, Stephen R; Schilstra, Maria J

    2013-01-01

    Almost all of the elementary steps in a biochemical reaction scheme are either unimolecular or bimolecular processes that frequently occur on sub-second, often sub-millisecond, time scales. The traditional approach in kinetic studies is to mix two or more reagents and monitor the changes in concentrations with time. Conventional spectrophotometers cannot generally be used to study reactions that are complete within less than about 20 s, as it takes that amount of time to manually mix the reagents and activate the instrument. Rapid mixing techniques, which generally achieve mixing in less than 2 ms, overcome this limitation. This chapter is concerned with the use of these techniques in the study of reactions which reach equilibrium; the application of these methods to the study of enzyme kinetics is described in several excellent texts (Cornish-Bowden, Fundamentals of enzyme kinetics. Portland Press, 1995; Gutfreund, Kinetics for the life sciences. Receptors, transmitters and catalysis. Cambridge University Press, 1995).There are various ways to monitor changes in concentration of reactants, intermediates and products after mixing, but the most common way is to use changes in optical signals (absorbance or fluorescence) which often accompany reactions. Although absorbance can sometimes be used, fluorescence is often preferred because of its greater sensitivity, particularly in monitoring conformational changes. Such methods are continuous with good time resolution but they seldom permit the direct determination of the concentrations of individual species. Alternatively, samples may be taken from the reaction volume, mixed with a chemical quenching agent to stop the reaction, and their contents assessed by techniques such as HPLC. These methods can directly determine the concentrations of different species, but are discontinuous and have a limited time resolution.

  4. Validation of effective momentum and heat flux models for stratification and mixing in a water pool

    Energy Technology Data Exchange (ETDEWEB)

    Hua Li; Villanueva, W.; Kudinov, P. [Royal Institute of Technology (KTH), Div. of Nuclear Power Safety, Stockholm (Sweden)

    2013-06-15

    The pressure suppression pool is the most important feature of the pressure suppression system in a Boiling Water Reactor (BWR) that acts primarily as a passive heat sink during a loss of coolant accident (LOCA) or when the reactor is isolated from the main heat sink. The steam injection into the pool through the blowdown pipes can lead to short term dynamic phenomena and long term thermal transient in the pool. The development of thermal stratification or mixing in the pool is a transient phenomenon that can influence the pool's pressure suppression capacity. Different condensation regimes depending on the pool's bulk temperature and steam flow rates determine the onset of thermal stratification or erosion of stratified layers. Previously, we have proposed to model the effect of steam injection on the mixing and stratification with the Effective Heat Source (EHS) and the Effective Momentum Source (EMS) models. The EHS model is used to provide thermal effect of steam injection on the pool, preserving heat and mass balance. The EMS model is used to simulate momentum induced by steam injection in different flow regimes. The EMS model is based on the combination of (i) synthetic jet theory, which predicts effective momentum if amplitude and frequency of flow oscillations in the pipe are given, and (ii) model proposed by Aya and Nariai for prediction of the amplitude and frequency of oscillations at a given pool temperature and steam mass flux. The complete EHS/EMS models only require the steam mass flux, initial pool bulk temperature, and design-specific parameters, to predict thermal stratification and mixing in a pressure suppression pool. In this work we use EHS/EMS models implemented in containment thermal hydraulic code GOTHIC. The PPOOLEX experiments (Lappeenranta University of Technology, Finland) are utilized to (a) quantify errors due to GOTHIC's physical models and numerical schemes, (b) propose necessary improvements in GOTHIC sub-grid scale

  5. Advective and Mixing Time Scales for Transport of Denmark Strait Overflow Water from the Labrador Sea to the Western Subtropical Atlantic Ocean Determined from 129I, CFC and Hydrographic Time Series Observations

    Science.gov (United States)

    Smethie, W. M., Jr.; Smith, J.; Curry, R. G.; Yashayaev, I.; Azetsu-Scott, K.

    2016-02-01

    129I released to the North Sea from two nuclear fuel reprocessing plants is transported through the Nordic Seas and the Arctic Ocean and is entering the deep North Atlantic, predominantly in dense Denmark Strait Overflow Water (DSOW). CFCs enter the surface ocean and also become incorporated in DSOW. Measurements of temperature, salinity, CFCs and 129I have been made at least annually along WOCE/CLIVAR line AR7W in the Labrador Sea from the mid 1990s to present, along Line W extending from the continental slope southeast of Cape Cod toward Bermuda from 2003 to 2014, and along a single occupation of a line extending from Bermuda southeast across the Bermuda Rise in 2010. The measurements in the Labrador Sea were used as input to DSOW flowing from there to the subtropical western Atlantic Ocean. We compared the temporal changes along Line W to the temporal changes along the AR7W line and applied the boundary current model of Waugh and Hall (J. Phys. Oceanogr. 35,1538-1552, 2005) to the Line W and Bermuda Rise line observations to determine the transit time of DSOW transported to Line W in the Deep Western Boundary Current (DWBC) and transported to the southeastern flank of Bermuda via interior flow paths. The lateral mixing time scale along these two flow paths was also estimated with this model. CFC-11 and 129I increase monotonically in the DSOW in the Labrador Sea and salinity oscillates on a 5-year cycle. The boundary current model reproduces all of these trends. The transit time and lateral mixing time constant for DSOW transported to Line W are 7 years (mean flow velocity of 2.1 cm/sec) and 3-6 years, respectively, and for DSOW transported to the southeast flank of Bermuda are 6-10 years and 2-5 years.

  6. Reactive mixing in swirling flows

    Science.gov (United States)

    Cheng, W. K.

    1980-01-01

    The effect of swirl on the mixing of two gas streams of the same density and axial velocity in a coaxial annular geometry has been examined. The flow is studied via a fluorescent tracer, 2-3 biacetyl. Through direct excitation, collisional excitation, and collisional de-excitation of the tracer, the turbulent transport, molecularly mixed and unmixed regions in the flow are visualized. The visualization results indicate that there are interesting three dimensional inviscid large scale structures. Mixing in the molecular level is found to be mainly localized in these structures.

  7. Mixed salt crystallisation fouling

    CERN Document Server

    Helalizadeh, A

    2002-01-01

    The main purpose of this investigation was to study the mechanisms of mixed salt crystallisation fouling on heat transfer surfaces during convective heat transfer and sub-cooled flow boiling conditions. To-date no investigations on the effects of operating parameters on the deposition of mixtures of calcium sulphate and calcium carbonate, which are the most common constituents of scales formed on heat transfer surfaces, have been reported. As part of this research project, a substantial number of experiments were performed to determine the mechanisms controlling deposition. Fluid velocity, heat flux, surface and bulk temperatures, concentration of the solution, ionic strength, pressure and heat transfer surface material were varied systematically. After clarification of the effect of these parameters on the deposition process, the results of these experiments were used to develop a mechanistic model for prediction of fouling resistances, caused by crystallisation of mixed salts, under convective heat transfer...

  8. Monitoring phenology of photosynthesis in temperate evergreen and mixed deciduous forests using the normalized difference vegetation index (NDVI) and the photochemical reflectance index (PRI) at leaf and canopy scales

    Science.gov (United States)

    Wong, C. Y.; Arain, M. A.; Ensminger, I.

    2016-12-01

    Evergreen conifers in boreal and temperate regions undergo strong seasonal changes in photoperiod and temperatures, which determines their phenology of high photosynthetic activity in the growing season and downregulation during the winter. Monitoring the timing of the transition between summer activity and winter downregulation in evergreens is difficult since this is a largely invisible process, unlike in deciduous trees that have a visible budding and a sequence of leaf unfolding in the spring and leaf abscission in the fall. The light-use efficiency (LUE) model estimates gross primary productivity (GPP) and may be parameterized using remotely sensed vegetation indices. Using spectral reflectance data, we derived the normalized difference vegetation index (NDVI), a measure of leaf "greenness", and the photochemical reflectance index (PRI), a proxy for chlorophyll:carotenoid ratios which is related to photosynthetic activity. To better understand the relationship between these vegetation indices and photosynthetic activity and to contrast this relationship between plant functional types, the phenology of NDVI, PRI and photosynthesis was monitored in an evergreen forest and a mixed deciduous forest at the leaf and canopy scale. Our data indicates that the LUE model can be parameterized by NDVI and PRI to track forest phenology. Differences in the sensitivity of PRI and NDVI will be discussed. These findings have implications to address the phenology of evergreen conifers by using PRI to complement NDVI in the LUE model, potentially improving model productivity estimates in northern hemisphere forests, that are dominated by conifers.

  9. The sensitivity of stratocumulus-capped mixed layers to cloud droplet concentration: do LES and mixed-layer models agree?

    Directory of Open Access Journals (Sweden)

    J. Uchida

    2010-05-01

    Full Text Available The sensitivity of a stratocumulus-capped mixed layer to a change in cloud droplet concentration is evaluated with a large-eddy simulation (LES and a mixed layer model (MLM. The strength of the second aerosol indirect effect simulated by the two model types agrees within 50% for cases in which the LES-simulated boundary layer remains well mixed, if the MLM entrainment closure includes the effects of cloud droplet sedimentation.

    To achieve this agreement, parameters in the MLM entrainment closure and the drizzle parameterization must be retuned to match the LES. This is because the LES advection scheme and microphysical parameterization significantly bias the entrainment rate and precipitation profile compared to observational best guesses. Before this modification, the MLM simulates more liquid water path and much more drizzle at a given droplet concentration than the LES and is more sensitive to droplet concentration, even undergoing a drizzle-induced boundary layer collapse at low droplet concentrations. After this modification, both models predict a comparable decrease of cloud liquid water path as droplet concentration increases, cancelling 30–50% of the Twomey effect for our case. The agreement breaks down at the lowest simulated droplet concentrations, for which the boundary layer in the LES is not well mixed.

    Our results highlight issues with both types of model. Potential LES biases due to inadequate resolution, subgrid mixing and parameterized microphysics must be carefully considered when trying to make a quantitative inference of the second indirect effect from an LES of a stratocumulus-topped boundary layer. On the other hand, even slight internal decoupling of the boundary layer invalidates the central assumption of an MLM, substantially limiting the range of conditions that MLM-predicted sensitivities to droplet concentration are meaningful.

  10. The sensitivity of stratocumulus-capped mixed layers to cloud droplet concentration: do LES and mixed-layer models agree?

    Science.gov (United States)

    Uchida, J.; Bretherton, C. S.; Blossey, P. N.

    2010-05-01

    The sensitivity of a stratocumulus-capped mixed layer to a change in cloud droplet concentration is evaluated with a large-eddy simulation (LES) and a mixed layer model (MLM). The strength of the second aerosol indirect effect simulated by the two model types agrees within 50% for cases in which the LES-simulated boundary layer remains well mixed, if the MLM entrainment closure includes the effects of cloud droplet sedimentation. To achieve this agreement, parameters in the MLM entrainment closure and the drizzle parameterization must be retuned to match the LES. This is because the LES advection scheme and microphysical parameterization significantly bias the entrainment rate and precipitation profile compared to observational best guesses. Before this modification, the MLM simulates more liquid water path and much more drizzle at a given droplet concentration than the LES and is more sensitive to droplet concentration, even undergoing a drizzle-induced boundary layer collapse at low droplet concentrations. After this modification, both models predict a comparable decrease of cloud liquid water path as droplet concentration increases, cancelling 30-50% of the Twomey effect for our case. The agreement breaks down at the lowest simulated droplet concentrations, for which the boundary layer in the LES is not well mixed. Our results highlight issues with both types of model. Potential LES biases due to inadequate resolution, subgrid mixing and parameterized microphysics must be carefully considered when trying to make a quantitative inference of the second indirect effect from an LES of a stratocumulus-topped boundary layer. On the other hand, even slight internal decoupling of the boundary layer invalidates the central assumption of an MLM, substantially limiting the range of conditions that MLM-predicted sensitivities to droplet concentration are meaningful.

  11. Multi-Layer Arctic Mixed-Phase Clouds Simulated by a Cloud-Resolving Model: Comparison with ARM Observations and Sensitivity Experiments

    Science.gov (United States)

    Luo, Yali; Xu, Kuan-Man; Morrison, Hugh; McFarquhar, Greg M.; Wang, Zhien; Zhang, Gong

    2007-01-01

    A cloud-resolving model (CRM) is used to simulate the multiple-layer mixed-phase stratiform (MPS) clouds that occurred during a three-and-a-half day subperiod of the Department of Energy-Atmospheric Radiation Measurement Program s Mixed-Phase Arctic Cloud Experiment (M-PACE). The CRM is implemented with an advanced two-moment microphysics scheme, a state-of-the-art radiative transfer scheme, and a complicated third-order turbulence closure. Concurrent meteorological, aerosol, and ice nucleus measurements are used to initialize the CRM. The CRM is prescribed by time-varying large-scale advective tendencies of temperature and moisture and surface turbulent fluxes of sensible and latent heat. The CRM reproduces the occurrences of the single- and double-layer MPS clouds as revealed by the M-PACE observations. However, the simulated first cloud layer is lower and the second cloud layer thicker compared to observations. The magnitude of the simulated liquid water path agrees with that observed, but its temporal variation is more pronounced than that observed. As in an earlier study of single-layer cloud, the CRM also captures the major characteristics in the vertical distributions and temporal variations of liquid water content (LWC), total ice water content (IWC), droplet number concentration and ice crystal number concentration (nis) as suggested by the aircraft observations. However, the simulated mean values differ significantly from the observed. The magnitude of nis is especially underestimated by one order of magnitude. Sensitivity experiments suggest that the lower cloud layer is closely related to the surface fluxes of sensible and latent heat; the upper cloud layer is probably initialized by the large-scale advective cooling/moistening and maintained through the strong longwave (LW) radiative cooling near the cloud top which enhances the dynamical circulation; artificially turning off all ice-phase microphysical processes results in an increase in LWP by a

  12. A Case for Nebula Scale Mixing Between Non-Carbonaceous and Carbonaceous Chondrite Reservoirs: Testing the Grand Tack Model with Chromium Isotopic Composition of Almahata Sitta Stone 91A

    Science.gov (United States)

    Sanborn, M. E.; Yin, Q.-Z.; Goodrich, C. A.; Zolensky, M.; Fioretti, A. M.

    2017-01-01

    There is an increasing number of Cr-O-Ti isotope studies that show solar system materials are divided into two main populations, one carbonaceous chondrite (CC)-like and the other is non-carbonaceous (NC)-like, with minimal mixing attributed to a gap opened in the protoplanetary disk due to Jupiter's formation. The Grand Tack model suggests there should be large-scale mixing between S- and C-type asteroids, an idea supported by our recent work on chondrule (Delta)17O-e54Cr isotope systematics. The Almahata Sitta (AhS) meteorite provides a unique opportunity to test the Grand Tack model. The meteorite fell to Earth in October 2008 and has been linked to the asteroid 2008 TC3 which was discovered just prior to the fall of the AhS stones. The AhS meteorite is composed of up to 700 individual pieces with approx.140 of those pieces having some geochemical and/or petrologic studies. Almahata Sitta is an anomalous polymict ureilite with other meteorite components, including enstatite, ordinary, and carbonaceous chondrites with an approximate abundance of 70% ureilites and 30% chondrites. This observation has lead to the suggestion that TC3 2008 was a loosely aggregated rubble pile-like asteroid with the non-ureilite sample clasts within the rubble-pile. Due to the loosely-aggregated nature of AhS, the object disintegrated during atmospheric entry resulting in the weakly held clasts falling predominantly as individual stones in the AhS collection area. However, recent work has identified one sample of AhS, sample 91A, which may represent two different lithologies coexisting within a single stone. The predominate lithology type in 91A appears to be that of a C2 chondrite based on mineralogy but also contains olivine, pyroxene, and albite that have ureilite-like compositions. Previous Cr isotope investigations into AhS stones are sparse and what data is available show nearly uniform isotopic composition similar to that of typical ureilites with negative e54Cr values.

  13. Solute mixing regulates heterogeneity of mineral precipitation in porous media: Effect of Solute Mixing on Precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Cil, Mehmet B.; Xie, Minwei; Packman, Aaron I.; Buscarnera, Giuseppe (NWU); (HKUST-- China)

    2017-07-04

    Synchrotron X-ray microtomography was used to track the spatiotemporal evolution of mineral precipitation and the consequent alteration of the pore structure. Column experiments were conducted by injecting CaCl2 and NaHCO3 solutions into granular porous media either as a premixed supersaturated solution (external mixing) or as separate solutions that mixed within the specimen (internal mixing). The two mixing modes produced distinct mineral growth patterns. While internal mixing promoted transverse heterogeneity with precipitation at the mixing zone, external mixing favored relatively homogeneous precipitation along the flow direction. The impact of precipitation on pore water flow and permeability was assessed via 3-D flow simulations, which indicated anisotropic permeability evolution for both mixing modes. Under both mixing modes, precipitation decreased the median pore size and increased the skewness of the pore size distribution. Such similar pore-scale evolution patterns suggest that the clogging of individual pores depends primarily on local supersaturation state and pore geometry.

  14. The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

    Directory of Open Access Journals (Sweden)

    A. Wiacek

    2010-09-01

    clouds" and the general influence of dust in the mixed-phase cloud region are highly uncertain due to both a considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work, and due to uncertainties in sub-grid scale vertical transport processes unresolved by the present trajectory analysis. For "classical" cirrus-forming temperatures (T≲−40 °C, our results show that only mineral dust ice nuclei that underwent mixed-phase cloud-processing, most likely acquiring coatings of organic or inorganic material, are likely to be relevant. While the potential paucity of deposition ice nuclei shown in this work dimishes the possibility of deposition nucleation, the absence of liquid water droplets at T≲−40 °C makes the less explored contact freezing mechanism (involving droplet collisions with bare ice nuclei highly inefficient. These factors together indicate the necessity of further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

  15. A Darwinian mechanism for biogenic ocean mixing

    Science.gov (United States)

    Katija, Kakani; Dabiri, John

    2009-11-01

    Recent observations of biogenic turbulence in the ocean have led to conflicting ideas regarding the contribution of animal swimming to ocean mixing. Previous measurements indicate elevated turbulent dissipation in the vicinity of large populations of planktonic animals swimming in concert. However, elevated turbulent dissipation is by itself insufficient proof of substantial biogenic mixing. We conducted field measurements of mixing efficiency by individual Mastigias sp. (a Palauan jellyfish) using a self-contained underwater velocimetry apparatus. These measurements revealed another mechanism that contributes to animal mixing besides wake turbulence. This mechanism was first described by Sir Charles Galton Darwin and is in fact the dominant mechanism of mixing by swimming animals. The efficiency of Darwin's mechanism (or drift) is dependent on animal shape rather than fluid length scale and, unlike turbulent wake mixing, is enhanced by the fluid viscosity. Therefore, it provides a means of biogenic mixing that can be equally effective in small plankton and large mammals.

  16. Turbulent diapycnal mixing in the northwestern Pacific

    Science.gov (United States)

    Balcerak, Ernie

    2011-11-01

    Nearly vertical mixing in the oceans across surfaces of constant density (isopycnals), known as diapycnal mixing, transports heat, modifies water masses, and maintains stratification. This mixing needs to be included in models of large-scale ocean circulation and climate models, but it is not fully understood. Some studies have suggested that wind is a key source of energy for diapycnal mixing in the deep ocean, but observational and modeling studies have been contradictory. To learn more, Jing et al. used data from recent hydrographic studies to study turbulent diapycnal mixing in the subtropical northwestern Pacific Ocean, a region that encompasses a range of ocean conditions, including both flat and rough seafloor. They examined spatial and seasonal variations as well as the role of eddies. They found that enhanced mixing occurred over rougher seafloor. Over flatter seafloor the researchers found that mixing is probably stirred by wind near the surface, with eddies playing an important role in enhancing mixing at greater depths. In the upper 600 meters of the ocean, the wind and diapycnal mixing varied seasonally, with stronger winds and mixing in winter and weaker winds and mixing in summer. This is different from the midlatitude northwestern Pacific, where seasonality of diapycnal mixing can be found at 1500-meter depth. (Journal of Geophysical Research-Oceans, doi:10.1029/2011JC007142, 2011)

  17. Mixed plastics recycling technology

    CERN Document Server

    Hegberg, Bruce

    1995-01-01

    Presents an overview of mixed plastics recycling technology. In addition, it characterizes mixed plastics wastes and describes collection methods, costs, and markets for reprocessed plastics products.

  18. A Novel Multi-Scale Domain Overlapping CFD/STH Coupling Methodology for Multi-Dimensional Flows Relevant to Nuclear Applications

    Science.gov (United States)

    Grunloh, Timothy P.

    The objective of this dissertation is to develop a 3-D domain-overlapping coupling method that leverages the superior flow field resolution of the Computational Fluid Dynamics (CFD) code STAR-CCM+ and the fast execution of the System Thermal Hydraulic (STH) code TRACE to efficiently and accurately model thermal hydraulic transport properties in nuclear power plants under complex conditions of regulatory and economic importance. The primary contribution is the novel Stabilized Inertial Domain Overlapping (SIDO) coupling method, which allows for on-the-fly correction of TRACE solutions for local pressures and velocity profiles inside multi-dimensional regions based on the results of the CFD simulation. The method is found to outperform the more frequently-used domain decomposition coupling methods. An STH code such as TRACE is designed to simulate large, diverse component networks, requiring simplifications to the fluid flow equations for reasonable execution times. Empirical correlations are therefore required for many sub-grid processes. The coarse grids used by TRACE diminish sensitivity to small scale geometric details such as Reactor Pressure Vessel (RPV) internals. A CFD code such as STAR-CCM+ uses much finer computational meshes that are sensitive to the geometric details of reactor internals. In turbulent flows, it is infeasible to fully resolve the flow solution, but the correlations used to model turbulence are at a low level. The CFD code can therefore resolve smaller scale flow processes. The development of a 3-D coupling method was carried out with the intention of improving predictive capabilities of transport properties in the downcomer and lower plenum regions of an RPV in reactor safety calculations. These regions are responsible for the multi-dimensional mixing effects that determine the distribution at the core inlet of quantities with reactivity implications, such as fluid temperature and dissolved neutron absorber concentration.

  19. Developing a global mixed-canopy, height-variable vegetation structure dataset for estimating global vegetation albedo by a clumped canopy radiative transfer scheme in the NASA Ent Terrestrial Biosphere Model and GISS GCM

    Science.gov (United States)

    Montes, Carlo; Kiang, Nancy Y.; Ni-Meister, Wenge; Yang, Wenze; Schaaf, Crystal; Aleinov, Igor; Jonas, Jeffrey A.; Zhao, Feng; Yao, Tian; Wang, Zhuosen; Sun, Qingsong; Carrer, Dominique

    2016-04-01

    products are a GVSD consisting of mixed plant communities (e.g. mixed forests, savannas, mixed PFTs) following the Ecosystem Demography model (Moorcroft et al., 2001) approach represented by multi-cohort community patches at the sub-grid level of the GCM, which are ensembles of identical individuals whose differences are represented by PFTs, canopy height, density and vegetation structure sensitivity to allometric parameters. The performance of the Ent TBM in estimating VIS-NIR vegetation albedo by the new GVSD and ACTS is assessed first by comparison against the previous GISS GCM vegetation classification and prescribed Lambertian albedoes of Matthews (1984), and secondly, against MODIS global estimations and FLUXNET site-scale observations. Ultimately, this GVSD will serve as a template for community data sets, and be used as boundary conditions to the Ent TBM for prediction of biomass, carbon balances and GISS GCM climate.

  20. A Posteriori Study of a DNS Database Describing Super critical Binary-Species Mixing

    Science.gov (United States)

    Bellan, Josette; Taskinoglu, Ezgi

    2012-01-01

    Currently, the modeling of supercritical-pressure flows through Large Eddy Simulation (LES) uses models derived for atmospheric-pressure flows. Those atmospheric-pressure flows do not exhibit the particularities of high densitygradient magnitude features observed both in experiments and simulations of supercritical-pressure flows in the case of two species mixing. To assess whether the current LES modeling is appropriate and if found not appropriate to propose higher-fidelity models, a LES a posteriori study has been conducted for a mixing layer that initially contains different species in the lower and upper streams, and where the initial pressure is larger than the critical pressure of either species. An initially-imposed vorticity perturbation promotes roll-up and a double pairing of four initial span-wise vortices into an ultimate vortex that reaches a transitional state. The LES equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equation set uses transport properties depending on the thermodynamic variables. Unlike all LES models to date, the differential equations contain, additional to the subgrid scale (SGS) fluxes, a new SGS term that is a pressure correction in the momentum equation. This additional term results from filtering of Direct Numerical Simulation (DNS) equations, and represents the gradient of the difference between the filtered pressure and the pressure computed from the filtered flow field. A previous a priori analysis, using a DNS database for the same configuration, found this term to be of leading order in the momentum equation, a fact traced to the existence of high-densitygradient magnitude regions that populated the entire flow; in the study, models were proposed for the SGS fluxes as well as this new term. In the present study, the previously proposed constantcoefficient SGS-flux models of the a priori investigation are tested a posteriori in LES, devoid of or including, the

  1. Mixing and Mass Transfer in Industrial Bioreactors

    DEFF Research Database (Denmark)

    Villadsen, John

    2015-01-01

    Design of a real reactor for a real process in industrial scale requires much more than the design of the "ideal" reactors. This insight is formulated in empirical relations between key process parameters, such as mass and heat transfer coefficients, and the power input to the process. Mixing...... formulas are not in any way quantitatively correct, but based on dimensional analysis one is able to extrapolate from small-to large-scale operation. It is shown that linear scale-up may not give the smallest power input for a given mixing objective. The introduction presented is the basis...

  2. Representing Sub-Plot Canopy Heterogeneity Improves Model Prediction of Net Ecosystem Exchange in a Mixed-Deciduous Forest

    Science.gov (United States)

    Frasson, R. P. M.; Bohrer, G.; Medvigy, D.; Vogel, C. S.; Gough, C. M.; Curtis, P.

    2014-12-01

    Canopy density and composition may vary within an eddy covariance tower's footprint in response to small-scale topographic features, biotic interactions such as herbivory, local disturbances, etc. We are investigating how different representations of canopy heterogeneity influence predictions of net ecosystem CO2 exchange in a mixed-deciduous forest by an age/plant functional type structured ecosystem model. Our study area is located at the University of Michigan Biological Station (UMBS) where two eddy covariance towers and periodic tree censuses provide a rich long-term record of ecosystem structure, weather, and carbon uptake. Meteorological measurements collected at the US-UMB AmeriFlux tower served to force, optimize, and evaluate the Ecosystem Demography model version 2 (ED2), while tree census information was used to initialize ED2. To test the influence that representing canopy heterogeneity has on model-tower agreement, we ran a set of ED2 site-level simulations with an increasing number of sub-grid patches. The first simulation, which we call 'aggregated', had one large patch explicitly containing all trees. The aggregated canopy represents a case where different size cohorts of each plant functional type are distributed homogeneously throughout the plot with uniform stem density. Six other simulations represented patch-level canopies with varying degrees of heterogeneity, ranging from 5 to 64 sub-plot patches; each patch represented from one to several of the 0.1 ha tree census plots. A preliminary comparison of the aggregated and the 20-plot heterogeneous simulations showed that including patch-level heterogeneity in the canopy description improved model prediction quality. For example, compared to the single-patch, aggregated simulation, including 20 sub-plot patches improved model bias in the estimated accumulated 5-year net ecosystem exchange from 17% to 5%, which is smaller than our tower observation uncertainty. As a result of this study, we will

  3. Mixing in explosions

    Energy Technology Data Exchange (ETDEWEB)

    Kuhl, A.L.

    1993-12-01

    Explosions always contain embedded turbulent mixing regions, for example: boundary layers, shear layers, wall jets, and unstable interfaces. Described here is one particular example of the latter, namely, the turbulent mixing occurring in the fireball of an HE-driven blast wave. The evolution of the turbulent mixing was studied via two-dimensional numerical simulations of the convective mixing processes on an adaptive mesh. Vorticity was generated on the fireball interface by baroclinic effects. The interface was unstable, and rapidly evolved into a turbulent mixing layer. Four phases of mixing were observed: (1) a strong blast wave phase; (2) and implosion phase; (3) a reshocking phase; and (4) an asymptotic mixing phase. The flowfield was azimuthally averaged to evaluate the mean and r.m.s. fluctuation profiles across the mixing layer. The vorticity decayed due to a cascade process. This caused the corresponding enstrophy parameter to increase linearly with time -- in agreement with homogeneous turbulence calculations of G.K. Batchelor.

  4. Scale in Education Research: Towards a Multi-Scale Methodology

    Science.gov (United States)

    Noyes, Andrew

    2013-01-01

    This article explores some theoretical and methodological problems concerned with scale in education research through a critique of a recent mixed-method project. The project was framed by scale metaphors drawn from the physical and earth sciences and I consider how recent thinking around scale, for example, in ecosystems and human geography might…

  5. Optimal Mixing Evolutionary Algorithms

    NARCIS (Netherlands)

    D. Thierens (Dirk); P.A.N. Bosman (Peter); N. Krasnogor

    2011-01-01

    htmlabstractA key search mechanism in Evolutionary Algorithms is the mixing or juxtaposing of partial solutions present in the parent solutions. In this paper we look at the efficiency of mixing in genetic algorithms (GAs) and estimation-of-distribution algorithms (EDAs). We compute the mixing

  6. Mixed methods research.

    Science.gov (United States)

    Halcomb, Elizabeth; Hickman, Louise

    2015-04-08

    Mixed methods research involves the use of qualitative and quantitative data in a single research project. It represents an alternative methodological approach, combining qualitative and quantitative research approaches, which enables nurse researchers to explore complex phenomena in detail. This article provides a practical overview of mixed methods research and its application in nursing, to guide the novice researcher considering a mixed methods research project.

  7. Mixing of solids in different mixing devices

    Indian Academy of Sciences (India)

    as devices for powder mixing, are tested as well as Turbula and V-shaped drum mixer, since those devices .... 1679·90. 13 force on the particles exceeds the pull of gravity), its working capacity is about 50% to 60% of volume. ... In solid/solid mixing the unit is usually vertical with the flow being by gravity only. The material is ...

  8. Mixed Alcohol Synthesis Catalyst Screening

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; White, James F.; Stevens, Don J.

    2007-09-03

    National Renewable Energy Laboratory (NREL) and Pacific Northwest National Laboratory (PNNL) are conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). PNNL is tasked with obtaining commercially available or preparing promising mixed-alcohol catalysts and screening them in a laboratory-scale reactor system. Commercially available catalysts and the most promising experimental catalysts are provided to NREL for testing using a slipstream from a pilot-scale biomass gasifier. From the standpoint of producing C2+ alcohols as the major product, it appears that the rhodium catalyst is the best choice in terms of both selectivity and space-time yield (STY). However, unless the rhodium catalyst can be improved to provide minimally acceptable STYs for commercial operation, mixed alcohol synthesis will involve significant production of other liquid coproducts. The modified Fischer-Tropsch catalyst shows the most promise for providing both an acceptable selectivity to C2+ alcohols and total liquid STY. However, further optimization of the Fischer-Tropsch catalysts to improve selectivity to higher alcohols is highly desired. Selection of a preferred catalyst will likely entail a decision on the preferred coproduct slate. No other catalysts tested appear amenable to the significant improvements needed for acceptable STYs.

  9. Mixing and compaction temperatures for Superpave mixes

    Science.gov (United States)

    Yildirim, Yetkin

    According to Superpave mixture design, gyratory specimens are mixed and compacted at equiviscous binder temperatures corresponding to viscosities of 0.17 and 0.28 Pa.s. respectively. These were the values previously used in the Marshal mix design method to determine optimal mixing and compaction temperatures. In order to estimate the appropriate mixing and compaction temperatures for Superpave mixture design, a temperature-viscosity relationship for the binder needs to be developed (ASTM D 2493, Calculation of Mixing and Compaction Temperatures). The current approach is simple and provides reasonable temperatures for unmodified binders. However, some modified binders have exhibited unreasonably high temperatures for mixing and compaction using this technique. These high temperatures can result in construction problems, damage of asphalt, and production of fumes. Heating asphalt binder to very high temperatures during construction oxidizes the binder and separates the polymer from asphalt binder. It is known that polymer modified asphalt binders have many benefits to the roads, such as; increasing rutting resistance, enhancing low temperature cracking resistance, improving traction, better adhesion and cohesion, elevating tensile strength which are directly related to the service life of the pavement. Therefore, oxidation and separation of the polymer from the asphalt binder results in reduction of the service life. ASTM D 2493 was established for unmodified asphalt binders which are Newtonian fluids at high temperatures. For these materials, viscosity does not depend on shear rate. However, most of the modified asphalt binders exhibit a phenomenon known as pseudoplasticity, where viscosity does depend on shear rate. Thus, at the high shear rates occurring during mixing and compaction, it is not necessary to go to very high temperatures. This research was undertaken to determine the shear rate during compaction such that the effect of this parameter could be

  10. Functional Additive Mixed Models

    Science.gov (United States)

    Scheipl, Fabian; Staicu, Ana-Maria; Greven, Sonja

    2014-01-01

    We propose an extensive framework for additive regression models for correlated functional responses, allowing for multiple partially nested or crossed functional random effects with flexible correlation structures for, e.g., spatial, temporal, or longitudinal functional data. Additionally, our framework includes linear and nonlinear effects of functional and scalar covariates that may vary smoothly over the index of the functional response. It accommodates densely or sparsely observed functional responses and predictors which may be observed with additional error and includes both spline-based and functional principal component-based terms. Estimation and inference in this framework is based on standard additive mixed models, allowing us to take advantage of established methods and robust, flexible algorithms. We provide easy-to-use open source software in the pffr() function for the R-package refund. Simulations show that the proposed method recovers relevant effects reliably, handles small sample sizes well and also scales to larger data sets. Applications with spatially and longitudinally observed functional data demonstrate the flexibility in modeling and interpretability of results of our approach. PMID:26347592

  11. Vertical Velocities in Cumulus Convection: Implications for Climate and Prospects for Realistic Simulation at Cloud Scale

    Science.gov (United States)

    Donner, Leo

    2014-05-01

    Cumulus mass fluxes are essential controls on the interactions between cumulus convection and large-scale flows. Cumulus parameterizations have generally been built around them, and these parameterizations are basic components of climate models. Several important questions in climate science depend also on cumulus vertical velocities. Interactions between aerosols and convection comprise a prominent example, and scale-aware cumulus parameterizations that require explicit information about cumulus areas are another. Basic progress on these problems requires realistic characterization of cumulus vertical velocities from observations and models. Recent deployments of dual-Doppler radars are providing unprecedented observations, which can be compared against cloud-resolving models (CRMs). The CRMs can subsequently be analyzed to develop and evaluate parameterizations of vertical velocities in climate models. Vertical velocities from several cloud models will be compared against observations in this presentation. CRM vertical velocities will be found to depend strongly on model resolution and treatment of sub-grid turbulence and microphysics. Although many current state-of-science CRMs do not simulate vertical velocities well, recent experiments with these models suggest that with appropriate treatments of sub-grid turbulence and microphysics robustly realistic modeling of cumulus vertical velocities is possible.

  12. Nanoscale mixing of soft solids.

    Science.gov (United States)

    Choi, Soo-Hyung; Lee, Sangwoo; Soto, Haidy E; Lodge, Timothy P; Bates, Frank S

    2011-02-16

    Assessing the state of mixing on the molecular scale in soft solids is challenging. Concentrated solutions of micelles formed by self-assembly of polystyrene-block-poly(ethylene-alt-propylene) (PS-PEP) diblock copolymers in squalane (C(30)H(62)) adopt a body-centered cubic (bcc) lattice, with glassy PS cores. Utilizing small-angle neutron scattering (SANS) and isotopic labeling ((1)H and (2)H (D) polystyrene blocks) in a contrast-matching solvent (a mixture of squalane and perdeuterated squalane), we demonstrate quantitatively the remarkable fact that a commercial mixer can create completely random mixtures of micelles with either normal, PS(H), or deuterium-labeled, PS(D), cores on a well-defined bcc lattice. The resulting SANS intensity is quantitatively modeled by the form factor of a single spherical core. These results demonstrate both the possibility of achieving complete nanoscale mixing in a soft solid and the use of SANS to quantify the randomness.

  13. Towards Cloud-Resolving European-Scale Climate Simulations using a fully GPU-enabled Prototype of the COSMO Regional Model

    Science.gov (United States)

    Leutwyler, David; Fuhrer, Oliver; Cumming, Benjamin; Lapillonne, Xavier; Gysi, Tobias; Lüthi, Daniel; Osuna, Carlos; Schär, Christoph

    2014-05-01

    The representation of moist convection is a major shortcoming of current global and regional climate models. State-of-the-art global models usually operate at grid spacings of 10-300 km, and therefore cannot fully resolve the relevant upscale and downscale energy cascades. Therefore parametrization of the relevant sub-grid scale processes is required. Several studies have shown that this approach entails major uncertainties for precipitation processes, which raises concerns about the model's ability to represent precipitation statistics and associated feedback processes, as well as their sensitivities to large-scale conditions. Further refining the model resolution to the kilometer scale allows representing these processes much closer to first principles and thus should yield an improved representation of the water cycle including the drivers of extreme events. Although cloud-resolving simulations are very useful tools for climate simulations and numerical weather prediction, their high horizontal resolution and consequently the small time steps needed, challenge current supercomputers to model large domains and long time scales. The recent innovations in the domain of hybrid supercomputers have led to mixed node designs with a conventional CPU and an accelerator such as a graphics processing unit (GPU). GPUs relax the necessity for cache coherency and complex memory hierarchies, but have a larger system memory-bandwidth. This is highly beneficial for low compute intensity codes such as atmospheric stencil-based models. However, to efficiently exploit these hybrid architectures, climate models need to be ported and/or redesigned. Within the framework of the Swiss High Performance High Productivity Computing initiative (HP2C) a project to port the COSMO model to hybrid architectures has recently come to and end. The product of these efforts is a version of COSMO with an improved performance on traditional x86-based clusters as well as hybrid architectures with GPUs

  14. Multiscale habitat relationships of snowshoe hares (Lepus americanus) in the mixed conifer landscape of the Northern Rockies, USA: Cross-scale effects of horizontal cover with implications for forest management.

    Science.gov (United States)

    Holbrook, Joseph D; Squires, John R; Olson, Lucretia E; Lawrence, Rick L; Savage, Shannon L

    2017-01-01

    Snowshoe hares (Lepus americanus) are an ecologically important herbivore because they modify vegetation through browsing and serve as a prey resource for multiple predators. We implemented a multiscale approach to characterize habitat relationships for snowshoe hares across the mixed conifer landscape of the northern Rocky Mountains, USA. Our objectives were to (1) assess the relationship between horizontal cover and snowshoe hares, (2) estimate how forest metrics vary across the gradient of snowshoe hare use and horizontal cover, and (3) model and map snowshoe hare occupancy and intensity of use. Results indicated that both occupancy and intensity of use by snowshoe hares increased with horizontal cover and that the effect became stronger as intensity of use increased. This underscores the importance of dense horizontal cover to achieve high use, and likely density, of snowshoe hares. Forest structure in areas with high snowshoe hare use and horizontal cover was characterized as multistoried with dense canopy cover and medium-sized trees (e.g., 12.7-24.4 cm). The abundance of lodgepole pine (Pinus contorta) was associated with snowshoe hare use within a mixed conifer context, and the only species to increase in abundance with horizontal cover was Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa). Our landscape-level modeling produced similar patterns in that we observed a positive effect of lodgepole pine and horizontal cover on both occupancy and use by snowshoe hares, but we also observed a positive yet parabolic effect of snow depth on snowshoe hare occupancy. This work is among the first to characterize the multiscale habitat relationships of snowshoe hares across a mixed conifer landscape as well as to map their occupancy and intensity of use. Moreover, our results provide stand- and landscape-level insights that directly relate to management agencies, which aids in conservation efforts of snowshoe hares and their associated

  15. MIXED AND MIXING SYSTEMS WORLDWIDE: A PREFACE

    Directory of Open Access Journals (Sweden)

    Seán Patrick Donlan

    2012-09-01

    Full Text Available This issue of the Potchefstroom Electronic Law Journal (South Africa sees thepublication of a selection of articles derived from the Third International Congress ofthe World Society of Mixed Jurisdiction Jurists (WSMJJ. That Congress was held atthe Hebrew University of Jerusalem, Israel in the summer of 2011. It reflected athriving Society consolidating its core scholarship on classical mixed jurisdictions(Israel, Louisiana, the Philippines, Puerto Rico, Quebec, Scotland, and South Africawhile reaching to new horizons (including Cyprus, Hong Kong and Macau, Malta,Nepal, etc. This publication reflects in microcosm the complexity of contemporaryscholarship on mixed and plural legal systems. This complexity is, of course, wellunderstoodby South African jurists whose system is derived both from the dominantEuropean traditions as well as from African customary systems, including both thosethat make up part of the official law of the state as well as those non-state norms thatcontinue to be important in the daily lives of many South Africans.

  16. European mixed forests

    DEFF Research Database (Denmark)

    Bravo-Oviedo, Andres; Pretzsch, Hans; Ammer, Christian

    2014-01-01

    Aim of study: We aim at (i) developing a reference definition of mixed forests in order to harmonize comparative research in mixed forests and (ii) review the research perspectives in mixed forests. Area of study: The definition is developed in Europe but can be tested worldwide. Material...... and Methods: Review of existent definitions of mixed forests based and literature review encompassing dynamics, management and economic valuation of mixed forests. Main results: A mixed forest is defined as a forest unit, excluding linear formations, where at least two tree species coexist at any...... developmental stage, sharing common resources (light, water, and/or soil nutrients). The presence of each of the component species is normally quantified as a proportion of the number of stems or of basal area, although volume, biomass or canopy cover as well as proportions by occupied stand area may be used...

  17. Efficiency of Metal Mixing in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Yutaka [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Saitoh, Takayuki R., E-mail: yutaka.hirai@nao.ac.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2017-04-01

    Metal mixing plays a critical role in the enrichment of metals in galaxies. The abundance of elements such as Mg, Fe, and Ba in metal-poor stars helps us understand the metal mixing in galaxies. However, the efficiency of metal mixing in galaxies is not yet understood. Here we report a series of N -body/smoothed particle hydrodynamics simulations of dwarf galaxies with different efficiencies of metal mixing using a turbulence-induced mixing model. We show that metal mixing apparently occurs in dwarf galaxies from Mg and Ba abundances. We find that a scaling factor for metal diffusion larger than 0.01 is necessary to reproduce the measured abundances of Ba in dwarf galaxies. This value is consistent with the value expected from turbulence theory and experiments. We also find that the timescale of metal mixing is less than 40 Myr. This timescale is shorter than the typical dynamical times of dwarf galaxies. We demonstrate that the determination of a degree of scatters of Ba abundance by the observation will help us to better constrain the efficiency of metal mixing.

  18. Optimal Length Scale for a Turbulent Dynamo.

    Science.gov (United States)

    Sadek, Mira; Alexakis, Alexandros; Fauve, Stephan

    2016-02-19

    We demonstrate that there is an optimal forcing length scale for low Prandtl number dynamo flows that can significantly reduce the required energy injection rate. The investigation is based on simulations of the induction equation in a periodic box of size 2πL. The flows considered are the laminar and turbulent ABC flows forced at different forcing wave numbers k_{f}, where the turbulent case is simulated using a subgrid turbulence model. At the smallest allowed forcing wave number k_{f}=k_{min}=1/L the laminar critical magnetic Reynolds number Rm_{c}^{lam} is more than an order of magnitude smaller than the turbulent critical magnetic Reynolds number Rm_{c}^{turb} due to the hindering effect of turbulent fluctuations. We show that this hindering effect is almost suppressed when the forcing wave number k_{f} is increased above an optimum wave number k_{f}L≃4 for which Rm_{c}^{turb} is minimum. At this optimal wave number, Rm_{c}^{turb} is smaller by more than a factor of 10 than the case forced in k_{f}=1. This leads to a reduction of the energy injection rate by 3 orders of magnitude when compared to the case where the system is forced at the largest scales and thus provides a new strategy for the design of a fully turbulent experimental dynamo.

  19. Mixing of solids in different mixing devices

    Indian Academy of Sciences (India)

    Agitation of the powder (especially powders with different bulk densities) may result in migration of smaller particles downwards and of larger ones upwards. Another problem is segregation whose main cause is the difference in particle size, density shape and resilience. There are standard mixing devices, such as drum ...

  20. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over four flux towers in the United States

    Science.gov (United States)

    Xueri Dang; Chun-Ta Lai; David Y. Hollinger; Andrew J. Schauer; Jingfeng Xiao; J. William Munger; Clenton Owensby; James R. Ehleringer

    2011-01-01

    We evaluated an idealized boundary layer (BL) model with simple parameterizations using vertical transport information from community model outputs (NCAR/NCEP Reanalysis and ECMWF Interim Analysis) to estimate regional-scale net CO2 fluxes from 2002 to 2007 at three forest and one grassland flux sites in the United States. The BL modeling...

  1. Effects of mixing on methane production during thermophilic anaerobic digestion of manure

    DEFF Research Database (Denmark)

    Kaparaju, Prasad Laxmi-Narasimha; Buendia, Inmaculada M.; Ellegaard, Lars

    2008-01-01

    (10 min mixing before feeding) was advantageous compared to vigorous mixing (110 times per minute). On the other hand, under low substrate to inoculum ratio (10/90), gentle mixing was the best. The study thus indicated that mixing schemes and intensities have some effect on anaerobic digestion....../feeding) on methane production was investigated in three lab-scale continuously stirred tank reactors. On comparison to continuous mixing, intermittent and minimal mixing strategies improved methane productions by 1.3% and 12.5%, respectively. Pilot-scale studies also supported the lab-scale results with an average 7......% increase in biogas yields during intermittent mixing compared to continuous mixing. The effect of mixing intensities (minimal, gentle or vigorous) in batch assays at 55 °C showed that when the process was overloaded by high substrate to inoculum ratio (40/60), gentle (35 times per minute) or minimal mixing...

  2. The Mixed language Debate

    DEFF Research Database (Denmark)

    A range of views on mixed languages and their connections to phenomena such as secret languages, massive borrowing, codeswitching and codemixing, and thier origin.......A range of views on mixed languages and their connections to phenomena such as secret languages, massive borrowing, codeswitching and codemixing, and thier origin....

  3. System equivalent model mixing

    NARCIS (Netherlands)

    Klaassen, Steven W.B.; van der Seijs, M.V.; de Klerk, D.

    2017-01-01

    This paper introduces SEMM: a method based on Frequency Based Substructuring (FBS) techniques that enables the construction of hybrid dynamic models. With System Equivalent Model Mixing (SEMM) frequency based models, either of numerical or experimental nature, can be mixed to form a hybrid model.

  4. Shear mixing in classical Novae

    Science.gov (United States)

    Alexakis, A.; Calder, A. C.; Dursi, L. J.; Times, F. X.; Truran, J. W.; Rosner, R.; Lamb, D. M.; Mignone, A.; Fryxel, B.; Zingale, M.; Olson, K.; Ricker, P.

    2003-03-01

    The mixing of white dwarf material with the accretion envelope in classical novae scenarios is essential for the later evolution and the outburst. One of the plausible mechanisms for the enrichment involves the coupling of large scale flows like convection or accretion with the breaking interfacial waves at the white dwarf surface. We examine how the interaction of accretion wind with a white dwarf surface can lead to a substantial C/O enrichment that can power a novae. We use the FLASH code to perform two and three dimensional simulations of wind driven gravity waves and investigate their growth and non-linear development for a variety of wind profiles. Our results show that even weak winds generate gravity waves through a resonant mechanism with the wind that grow nonlinear and break leading to spray formation and mixing. The total amount of white dwarf material mixed at late times, is shown to be proportional to the square of the maximum wind velocity, inversely proportional to gravity and independent of the functional form of the wind profile. This work has been supported by the DOE ASCI/Alliances program at the University of Chicago under grant No. B341495.

  5. High-mix insulins

    Directory of Open Access Journals (Sweden)

    Sanjay Kalra

    2015-01-01

    Full Text Available Premix insulins are commonly used insulin preparations, which are available in varying ratios of different molecules. These drugs contain one short- or rapid-acting, and one intermediate- or long-acting insulin. High-mix insulins are mixtures of insulins that contain 50% or more than 50% of short-acting insulin. This review describes the clinical pharmacology of high-mix insulins, including data from randomized controlled trials. It suggests various ways, in which high-mix insulin can be used, including once daily, twice daily, thrice daily, hetero-mix, and reverse regimes. The authors provide a rational framework to help diabetes care professionals, identify indications for pragmatic high-mix use.

  6. Direct numerical simulations of the double scalar mixing layer. Part I: Passive scalar mixing and dissipation

    Science.gov (United States)

    Cha, Chong M.; de Bruyn Kops, Stephen M.; Mortensen, Mikael

    2006-06-01

    The double scalar mixing layer (DSML) is a canonical problem for studying the mixing of multiple streams and, with reaction, combustion of the partially premixed type. In a DSML, a third stream consisting of a premixture of the reactants is introduced in between the pure fuel and air streams of the classic twin-feed or binary mixing problem. The well-known presumed probability density function (PDF), such as the β-PDF, can adequately model passive scalar mixing for the binary mixing problem on which state-of-the-art turbulent combustion models such as conditional moment closure and flamelet approaches rely. However, the β-PDF model, now a standard in CFD simulation, cannot describe turbulent mixing involving multiple streams; e.g., the asymmetric three-stream mixing characterizing the DSML. In this paper, direct numerical simulations of the DSML are performed to make available a high-fidelity database for developing more general, fine-scale mixing models required to compute turbulent combustion problems of practical engineering interest, which usually involve mixing between multiple streams. In this first part of two investigations, nonreacting numerical experiments are presented with emphasis on the nontrivial distributions of the passive scalar and its dissipation rate. Mapping closure modeling is applied to describe the PDFs and conditional dissipation rates of a single mixture fraction.

  7. A Review on Mixing in Microfluidics

    Directory of Open Access Journals (Sweden)

    Sangmo Kang

    2010-09-01

    Full Text Available Small-scale mixing is of uttermost importance in bio- and chemical analyses using micro TAS (total analysis systems or lab-on-chips. Many microfluidic applications involve chemical reactions where, most often, the fluid diffusivity is very low so that without the help of chaotic advection the reaction time can be extremely long. In this article, we will review various kinds of mixers developed for use in microfluidic devices. Our review starts by defining the terminology necessary to understand the fundamental concept of mixing and by introducing quantities for evaluating the mixing performance, such as mixing index and residence time. In particular, we will review the concept of chaotic advection and the mathematical terms, Poincare section and Lyapunov exponent. Since these concepts are developed from nonlinear dynamical systems, they should play important roles in devising microfluidic devices with enhanced mixing performance. Following, we review the various designs of mixers that are employed in applications. We will classify the designs in terms of the driving forces, including mechanical, electrical and magnetic forces, used to control fluid flow upon mixing. The advantages and disadvantages of each design will also be addressed. Finally, we will briefly touch on the expected future development regarding mixer design and related issues for the further enhancement of mixing performance.

  8. The mixing of fluids

    Energy Technology Data Exchange (ETDEWEB)

    Ottino, J.M.

    1989-01-01

    What do the eruption of Krakatau, the manufacture of puff pastry and the brightness of stars have in common Each involves some aspect of mixing. Mixing also plays a critical role in modern technology. Chemical engineers rely on mixing to ensure that substances react properly, to produce polymer blends that exhibit unique properties and to disperse drag-reducing agents in pipelines. Yet in spite of its of its ubiquity in nature and industry, mixing is only imperfectly under-stood. Indeed, investigators cannot even settle on a common terminology: mixing is often referred to as stirring by oceanographers and geophysicists, as blending by polymer engineers and as agitation by process engineers. Regardless of what the process is called, there is little doubt that it is exceedingly complex and is found in a great variety of systems. In constructing a theory of fluid mixing, for example, one has to take into account fluids that can be miscible or partially miscible and reactive or inert, and flows that are slow and orderly or very fast and turbulent. It is therefore not surprising that no single theory can explain all aspect of mixing in fluids and that straightforward computations usually fail to capture all the important details. Still, both physical experiments and computer simulations can provide insight into the mixing process. Over the past several years the authors and his colleague have taken both approaches in an effort to increase understanding of various aspect of the process-particularly of mixing involving slow flows and viscous fluids such as oils.

  9. Multi scale and physics models for intermediate and low temperatures H+-solid oxide fuel cells with H+/e-/O2- mixed conducting properties: Part A, generalized percolation theory for LSCF-SDC-BZCY 3-component cathodes

    Science.gov (United States)

    Chen, Daifen; Zhang, Qiang; Lu, Liu; Periasamy, Vijay; Tade, Moses O.; Shao, Zongping

    2016-01-01

    H+ based solid oxide fuel cell (SOFC) composite cathodes are generally agreed to be of quite different relationships among the microstructure parameters, electrode properties and detailed working processes from the conventional O2--SOFC composite cathodes. In this paper, the percolation theory is significantly generalized and developed to suit most of the typical H+-SOFC composite cathodes with e-/H+, e-/O2- or e-/H+/O2- mixed conducting characteristics; not just limited to the BCZY, SDC and LSCF materials. It provides an easy way to investigate the effect of microstructure parameters on the H+-SOFC electrode characteristics in quantity. The studied electrode properties include: i) the potential coexisting sites of O2, e-, and O2- transport paths for the oxygen reduction; ii) the potential coexisting sites of O2-, H+ and H2O transport paths for the vapor formation; iii) the effective e-, O2-, and H+ conducting and gas diffusing capabilities of the composite cathodes, and so on. It will be helpful for the H+-SOFC composite cathode manufacture to achieve the expected properties. Furthermore, it is also an important step for the developing of the multiphysics-model in manuscript part B to study the effect of the microstructure parameters on the H+-SOFC working details.

  10. News on Deep Mixing

    Science.gov (United States)

    Lattanzio, John C.; Dearborn, Davis S. P.; Eggleton, Peter P.

    2008-04-01

    We briefly summarize the abundant observational evidence for the need of a ``deep mixing'' mechanism in first-ascent red-giant stars, and probably in AGB stars as well. By the term ``deep mixing'' we mean some mixing mechanism which operates in the radiative zone below the convective envelope, and which transports material from the convective region to hotter regions, near the top of the hydrogen shell, where nuclear burning may take place. We then discuss a recent discovery of deep-mixing caused by the burning of 3He following first dredge-up in low-mass stars. This is expected to be a thermohaline process and preliminary calculations show that it has many of the properties required to explain the observations.

  11. Effects of Low- Versus High-Fidelity Simulations on the Cognitive Burden and Performance of Entry-Level Paramedicine Students: A Mixed-Methods Comparison Trial Using Eye-Tracking, Continuous Heart Rate, Difficulty Rating Scales, Video Observation and Interviews.

    Science.gov (United States)

    Mills, Brennen W; Carter, Owen B-J; Rudd, Cobie J; Claxton, Louise A; Ross, Nathan P; Strobel, Natalie A

    2016-02-01

    High-fidelity simulation-based training is often avoided for early-stage students because of the assumption that while practicing newly learned skills, they are ill suited to processing multiple demands, which can lead to "cognitive overload" and poorer learning outcomes. We tested this assumption using a mixed-methods experimental design manipulating psychological immersion. Thirty-nine randomly assigned first-year paramedicine students completed low- or high-environmental fidelity simulations [low-environmental fidelity simulations (LF(en)S) vs. high-environmental fidelity simulation (HF(en)S)] involving a manikin with obstructed airway (SimMan3G). Psychological immersion and cognitive burden were determined via continuous heart rate, eye tracking, self-report questionnaire (National Aeronautics and Space Administration Task Load Index), independent observation, and postsimulation interviews. Performance was assessed by successful location of obstruction and time-to-termination. Eye tracking confirmed that students attended to multiple, concurrent stimuli in HF(en)S and interviews consistently suggested that they experienced greater psychological immersion and cognitive burden than their LF(en)S counterparts. This was confirmed by significantly higher mean heart rate (P students who ultimately revived the patient (58% vs. 30%, P students did so significantly more quickly (P students had low immersion resulting in greater assessment anxiety. High-environmental fidelity simulation engendered immersion and a sense of urgency in students, whereas LF(en)S created assessment anxiety and slower performance. We conclude that once early-stage students have learned the basics of a clinical skill, throwing them in the "deep end" of high-fidelity simulation creates significant additional cognitive burden but this has considerable educational merit.

  12. Music Mixing Surface

    OpenAIRE

    Gelineck, Steven; Büchert, Morten; Andersen, Jesper

    2013-01-01

    This paper presents a multi-touch based interface for mixing music. The goal of the interface is to provide users with a more intuitive control of the music mix by implementing the so-called stage metaphor control scheme, which is especially suitable for multi-touch surfaces. Specifically, we discuss functionality important for the professional music technician (main target user) - functionality, which is especially challenging to integrate when implementing the stage metaphor. Finally we pro...

  13. The health marketing mix

    OpenAIRE

    Pralea, A. R.

    2011-01-01

    The well-known marketing mix of the commercial sector has found its application and has been developing in the non-profit sector. In most of the cases, the techniques and tools of commercial marketing are used to change behaviours in order to achieve social good. The targeted behaviours range widely from environmental ones to health related behaviours. The aim of the current paper is to highlight some of the characteristics of the marketing mix when applied to change health related behaviours...

  14. Music Mixing Surface

    DEFF Research Database (Denmark)

    Gelineck, Steven; Büchert, Morten; Andersen, Jesper

    2013-01-01

    This paper presents a multi-touch based interface for mixing music. The goal of the interface is to provide users with a more intuitive control of the music mix by implementing the so-called stage metaphor control scheme, which is especially suitable for multi-touch surfaces. Specifically, we...... discuss functionality important for the professional music technician (main target user) - functionality, which is especially challenging to integrate when implementing the stage metaphor. Finally we propose and evaluate solutions to these challenges....

  15. Physics and Dynamics Coupling Across Scales in the Next Generation CESM. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Bacmeister, Julio T. [University Corporation for Atmospheric Research (UCAR), Boulder, CO (United States)

    2015-06-12

    This project examines physics/dynamics coupling, that is, exchange of meteorological profiles and tendencies between an atmospheric model’s dynamical core and its various physics parameterizations. Most model physics parameterizations seek to represent processes that occur on scales smaller than the smallest scale resolved by the dynamical core. As a consequence a key conceptual aspect of parameterizations is an assumption about the subgrid variability of quantities such as temperature, humidity or vertical wind. Most existing parameterizations of processes such as turbulence, convection, cloud, and gravity wave drag make relatively ad hoc assumptions about this variability and are forced to introduce empirical parameters, i.e., “tuning knobs” to obtain realistic simulations. These knobs make systematic dependences on model grid size difficult to quantify.

  16. FBR for Catalytic Propylene Polymerization: Controlled Mixing and Reactor Modeling

    NARCIS (Netherlands)

    Meier, G.B.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria

    2002-01-01

    Particle mixing and segregation have been studied in a small-scale fluidized-bed reactor (FBR) under pressure. The solids mixing is relatively faster than the residence time of catalyst particles in the case of a polymerization process, but smaller particles accumulate in the upper zone. Semibatch

  17. Pulse Jet Mixing Tests With Noncohesive Solids

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Perry A.; Bamberger, Judith A.; Enderlin, Carl W.; Fort, James A.; Wells, Beric E.; Sundaram, S. K.; Scott, Paul A.; Minette, Michael J.; Smith, Gary L.; Burns, Carolyn A.; Greenwood, Margaret S.; Morgen, Gerald P.; Baer, Ellen BK; Snyder, Sandra F.; White, Michael K.; Piepel, Gregory F.; Amidan, Brett G.; Heredia-Langner, Alejandro

    2012-02-17

    This report summarizes results from pulse jet mixing (PJM) tests with noncohesive solids in Newtonian liquid. The tests were conducted during FY 2007 and 2008 to support the design of mixing systems for the Hanford Waste Treatment and Immobilization Plant (WTP). Tests were conducted at three geometric scales using noncohesive simulants, and the test data were used to develop models predicting two measures of mixing performance for full-scale WTP vessels. The models predict the cloud height (the height to which solids will be lifted by the PJM action) and the critical suspension velocity (the minimum velocity needed to ensure all solids are suspended off the floor, though not fully mixed). From the cloud height, the concentration of solids at the pump inlet can be estimated. The predicted critical suspension velocity for lifting all solids is not precisely the same as the mixing requirement for 'disturbing' a sufficient volume of solids, but the values will be similar and closely related. These predictive models were successfully benchmarked against larger scale tests and compared well with results from computational fluid dynamics simulations. The application of the models to assess mixing in WTP vessels is illustrated in examples for 13 distinct designs and selected operational conditions. The values selected for these examples are not final; thus, the estimates of performance should not be interpreted as final conclusions of design adequacy or inadequacy. However, this work does reveal that several vessels may require adjustments to design, operating features, or waste feed properties to ensure confidence in operation. The models described in this report will prove to be valuable engineering tools to evaluate options as designs are finalized for the WTP. Revision 1 refines data sets used for model development and summarizes models developed since the completion of Revision 0.

  18. Parental Language Mixing: Its Measurement and the Relation of Mixed Input to Young Bilingual Children's Vocabulary Size

    Science.gov (United States)

    Byers-Heinlein, Krista

    2013-01-01

    Is parental language mixing related to vocabulary acquisition in bilingual infants and children? Bilingual parents (who spoke English and another language; n = 181) completed the Language Mixing Scale questionnaire, a new self-report measure that assesses how frequently parents use words from two different languages in the same sentence, such as…

  19. Mixed waste management options

    Energy Technology Data Exchange (ETDEWEB)

    Owens, C.B.; Kirner, N.P. [EG and G Idaho, Inc., Idaho Falls, ID (United States). Idaho National Engineering Lab.

    1991-12-31

    Disposal fees for mixed waste at proposed commercial disposal sites have been estimated to be $15,000 to $40,000 per cubit foot. If such high disposal fees are imposed, generators may be willing to apply extraordinary treatment or regulatory approaches to properly dispose of their mixed waste. This paper explores the feasibility of several waste management scenarios and attempts to answer the question: Can mixed waste be managed out of existence? Existing data on commercially generated mixed waste streams are used to identify the realm of mixed waste known to be generated. Each waste stream is evaluated from both a regulatory and technical perspective in order to convert the waste into a strictly low-level radioactive or a hazardous waste. Alternative regulatory approaches evaluated in this paper include a delisting petition, no migration petition, and a treatability variance. For each waste stream, potentially available treatment options are identified that could lead to these variances. Waste minimization methodology and storage for decay are also considered. Economic feasibility of each option is discussed broadly.

  20. [Mixed states and schizophrenia].

    Science.gov (United States)

    Fakra, E; Belzeaux, R; Pringuey, D; Cermolacce, M; Corréard, N; Micoulaud-Franchi, J-A; Azorin, J-M

    2013-12-01

    Because of their compilation of contrasted symptoms and their variable clinical presentation, mixed episodes have been withdrawn from the DSM. However, mixed states question not only the bonds between depression and mania, but also the distinction between bipolar disorders and schizophrenia. Indeed, doubts about the dichotomy introduced by Kraepelin between bipolar disorders and schizophrenia is as old as the nosolgy itself, as attest the later works of this author revealing his hesitations on his own classification. But findings here reviewed issued from recent technical advances, particularly in the imaging and genetic fields, offer a better understanding of the boundaries between these two disorders. Yet, when confronted to an acute episode, clinicians may find it challenging to distinguish a mixed state from a schizophrenic relapse. Indeed, there is no pathognomonic manifestation allowing to retain a diagnosis with confidence. The physician will therefore have to identify a pattern of signs, which will orient his assessment with no certainty. Thus, negative rather than affective or psychotic symptomatology appears to be useful in discriminating schizophrenia (or schizoaffective) disorders from mixed mania. However, a conclusion during this acute stage appears in definitive a formal exercise, first because the final diagnosis will only be ascertained once the symptoms are amended, and second because, according to our classifications, a mood episode, including mania and mixed mania, can be observed without ruling out the diagnosis of schizophrenia. Copyright © 2013 L’Encéphale. Published by Elsevier Masson SAS.. All rights reserved.

  1. Mixing on a Continental Shelf

    Science.gov (United States)

    Chernys, Michael; Dhanak, Manhar

    2000-11-01

    Small scale turbulence measurements over a warm continental shelf during the passage of a cold front over the Eastern Florida coast are described. Over a 22 hour period microstructure velocity shear, conductivity, and temperature, together with background current profiles and CTD were measured using an autonomous underwater vehicle. The aim was to investigate the impact of the front on mixing in the shallow water column. Periodic CTD casts were taken from the boat and surface currents were measured from a shore fixed surface current radar system. The AUV surveyed the water column at 10m depth. A cold front appraoched the region 4/18/2000 with wind speeds of 3-6 m/s, originating from a westerly direction the ambient air temperature being 27^0C. Dissipation rates, O(10-6 W/kg) were measured, with good agreement of the shear spectra with the Nasmyth spectra. As the front progressed, the winds switched to a northerly direction and the air temperature dropped to 22^0C, lower dissipation rates, O(2 × 10-7 W/kg) were observed. The associated mixing rates and values of the flow Richardson number will be described.

  2. Mixed waste: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Moghissi, A.A.; Blauvelt, R.K.; Benda, G.A.; Rothermich, N.E. [eds.] [Temple Univ., Philadelphia, PA (United States). Dept. of Environmental Safety and Health

    1993-12-31

    This volume contains the peer-reviewed and edited versions of papers submitted for presentation a the Second International Mixed Waste Symposium. Following the tradition of the First International Mixed Waste Symposium, these proceedings were prepared in advance of the meeting for distribution to participants. The symposium was organized by the Mixed Waste Committee of the American Society of Mechanical Engineers. The topics discussed at the symposium include: stabilization technologies, alternative treatment technologies, regulatory issues, vitrification technologies, characterization of wastes, thermal technologies, laboratory and analytical issues, waste storage and disposal, organic treatment technologies, waste minimization, packaging and transportation, treatment of mercury contaminated wastes and bioprocessing, and environmental restoration. Individual abstracts are catalogued separately for the data base.

  3. Neutrino Mixing: Theoretical Overview

    CERN Document Server

    Altarelli, Guido

    2013-01-01

    We present a concise review of the recent important experimental developments on neutrino mixing (hints for sterile neutrinos, large $\\theta_{13}$, possible non maximal $\\theta_{23}$, approaching sensitivity on $\\delta_{CP}$) and their implications on models of neutrino mixing. The new data disfavour many models but the surviving ones still span a wide range going from Anarchy (no structure, no symmetry in the lepton sector) to a maximum of symmetry, as for the models based on discrete non-abelian flavour groups that can be improved following the indications from the data.

  4. Mixed Reality Systems

    Directory of Open Access Journals (Sweden)

    Dieter Müller

    2009-11-01

    Full Text Available Currently one of the most challenging aspects of human computer interaction design is the integration of physical and digital worlds in a single environment. This fusion involves the development of "Mixed Reality Systems”, including various technologies from the domains of augmented and virtual reality. In this paper I will present related concepts and discuss lessons learned from our own research and prototype development. Our recent work involves the use of mixed reality (as opposed to ‘pure’ virtual reality techniques to support seamless collaborative work between remote and hands-on laboratories.

  5. Mixing in a river

    Energy Technology Data Exchange (ETDEWEB)

    Bernath, L.; Menegus, R.L.; Ring, H.F.

    1956-05-09

    Many rivers are burdened with tributary streams of warm water and/or liquid wastes containing dissolved or suspended matter. The warm water and waste matter mix thoroughly with the river water some distance downstream from the point of entry of the tributary, but near the point of entry there may be high local temperatures or concentrations of waste. It is often necessary to know the local temperatures or concentrations of waste. The authors have used a formula for computing the turbulent mixing that takes place in such a situation; this formula fits quite well in the case of one Southern river.

  6. Turbulence and Interfacial Mixing

    Energy Technology Data Exchange (ETDEWEB)

    Glimm, James; Li, Xiaolin

    2005-03-15

    The authors study mix from analytical and numerical points of view. These investigations are linked. The analytical studies (in addition to laboratory experiments) provide bench marks for the direct simulation of mix. However, direct simulation is too detailed to be useful and to expensive to be practical. They also consider averaged equations. Here the major issue is the validation of the closure assumptions. They appeal to the direct simulation methods for this step. They have collaborated with several NNSA teams; moreover, Stony Brook alumni (former students, faculty and research collaborators) presently hold staff positions in NNSA laboratories.

  7. Mixed crystal organic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Zaitseva, Natalia P; Carman, M Leslie; Glenn, Andrew M; Hamel, Sebastien; Hatarik, Robert; Payne, Stephen A; Stoeffl, Wolfgang

    2014-09-16

    A mixed organic crystal according to one embodiment includes a single mixed crystal having two compounds with different bandgap energies, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source, wherein the signal response signature does not include a significantly-delayed luminescence characteristic of neutrons interacting with the organic crystal relative to a luminescence characteristic of gamma rays interacting with the organic crystal. According to one embodiment, an organic crystal includes bibenzyl and stilbene or a stilbene derivative, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source.

  8. Suppression of phase mixing in drift-kinetic plasma turbulence

    CERN Document Server

    Parker, J T; Schekochihin, A A; Dellar, P J

    2016-01-01

    Transfer of free energy from large to small velocity-space scales by phase mixing leads to Landau damping in a linear plasma. In a turbulent drift-kinetic plasma, this transfer is statistically nearly canceled by an inverse transfer from small to large velocity-space scales due to "anti-phase-mixing" modes excited by a stochastic form of plasma echo. Fluid moments (density, velocity, temperature) are thus approximately energetically isolated from the higher moments of the distribution function, so phase mixing is ineffective as a dissipation mechanism when the plasma collisionality is small.

  9. Mixing and solid suspension in a stirred precipitator

    Energy Technology Data Exchange (ETDEWEB)

    Chang, T P

    1986-01-01

    Full-scale mixing and solid suspension studies have been conducted to determine the optimum agitator design for precipitators used in plutonium processing. Design considerations include the geometry of precipitator vessels, feed locations, flow patterns, and product requirements. Evaluations of various agitator designs are based on their capabilities: (1) to achieve uniform mixing of reactants in minimum time, (2) to suspend the slurry uniformly throughout the vessel, and (3) to minimize power consumption without inducing air entrainment. Tests of full-scale agitator designs showed that significant improvements in mixing, solid suspension, and energy consumption were achieved.

  10. Scales of mantle heterogeneity

    Science.gov (United States)

    Moore, J. C.; Akber-Knutson, S.; Konter, J.; Kellogg, J.; Hart, S.; Kellogg, L. H.; Romanowicz, B.

    2004-12-01

    A long-standing question in mantle dynamics concerns the scale of heterogeneity in the mantle. Mantle convection tends to both destroy (through stirring) and create (through melt extraction and subduction) heterogeneity in bulk and trace element composition. Over time, these competing processes create variations in geochemical composition along mid-oceanic ridges and among oceanic islands, spanning a range of scales from extremely long wavelength (for example, the DUPAL anomaly) to very small scale (for example, variations amongst melt inclusions). While geochemical data and seismic observations can be used to constrain the length scales of mantle heterogeneity, dynamical mixing calculations can illustrate the processes and timescales involved in stirring and mixing. At the Summer 2004 CIDER workshop on Relating Geochemical and Seismological Heterogeneity in the Earth's Mantle, an interdisciplinary group evaluated scales of heterogeneity in the Earth's mantle using a combined analysis of geochemical data, seismological data and results of numerical models of mixing. We mined the PetDB database for isotopic data from glass and whole rock analyses for the Mid-Atlantic Ridge (MAR) and the East Pacific Rise (EPR), projecting them along the ridge length. We examined Sr isotope variability along the East Pacific rise by looking at the difference in Sr ratio between adjacent samples as a function of distance between the samples. The East Pacific Rise exhibits an overall bowl shape of normal MORB characteristics, with higher values in the higher latitudes (there is, however, an unfortunate gap in sampling, roughly 2000 km long). These background characteristics are punctuated with spikes in values at various locations, some, but not all of which are associated with off-axis volcanism. A Lomb-Scargle periodogram for unevenly spaced data was utilized to construct a power spectrum of the scale lengths of heterogeneity along both ridges. Using the same isotopic systems (Sr, Nd

  11. A viscosity-enhanced mechanism for biogenic ocean mixing.

    Science.gov (United States)

    Katija, Kakani; Dabiri, John O

    2009-07-30

    Recent observations of biologically generated turbulence in the ocean have led to conflicting conclusions regarding the significance of the contribution of animal swimming to ocean mixing. Measurements indicate elevated turbulent dissipation--comparable with levels caused by winds and tides--in the vicinity of large populations of planktonic animals swimming together. However, it has also been noted that elevated turbulent dissipation is by itself insufficient proof of substantial biogenic mixing, because much of the turbulent kinetic energy of small animals is injected below the Ozmidov buoyancy length scale, where it is primarily dissipated as heat by the fluid viscosity before it can affect ocean mixing. Ongoing debate regarding biogenic mixing has focused on comparisons between animal wake turbulence and ocean turbulence. Here, we show that a second, previously neglected mechanism of fluid mixing--first described over 50 years ago by Charles Darwin--is the dominant mechanism of mixing by swimming animals. The efficiency of mixing by Darwin's mechanism is dependent on animal shape rather than fluid length scale and, unlike turbulent wake mixing, is enhanced by fluid viscosity. Therefore, it provides a means of biogenic mixing that can be equally effective in small zooplankton and large mammals. A theoretical model for the relative contributions of Darwinian mixing and turbulent wake mixing is created and validated by in situ field measurements of swimming jellyfish using a newly developed scuba-based laser velocimetry device. Extrapolation of these results to other animals is straightforward given knowledge of the animal shape and orientation during vertical migration. On the basis of calculations of a broad range of aquatic animal species, we conclude that biogenic mixing via Darwin's mechanism can be a significant contributor to ocean mixing and nutrient transport.

  12. Turbulent mixing and entrainment in a gravity current

    Energy Technology Data Exchange (ETDEWEB)

    Ecke, Robert E [Los Alamos National Laboratory; Odier, Philippe [ENS-LYON, FRANCE; Chen, Jun [PURDUE UNIV.

    2010-01-01

    We present an experimental study of the mixing processes in a gravity current. The turbulent transport of momentum and buoyancy can be described in a very direct and compact form by a Prandtl mixing length model: the turbulent vertical fluxes of momentum and buoyancy are found to scale quadratically with the vertical mean gradients of velocity and density. The scaling coefficient is the square of the mixing lenth, approximately constant over the mixing zone of the stratified shear layer. We show how, in different flow configurations, this length can be related to the shear length of the flow ({var_epsilon}/{partial_derivative}{sub z}u{sup 3}){sup 1/2}. We also study the fluctuations of the momentum and density turbulent fluxes, showing how they relate to the mixing phenomena, and to the entrainment/detrainment balance.

  13. Probabilistic Downscaling of Remote Sensing Data with Applications for Multi-Scale Biogeochemical Flux Modeling.

    Science.gov (United States)

    Stoy, Paul C; Quaife, Tristan

    2015-01-01

    Upscaling ecological information to larger scales in space and downscaling remote sensing observations or model simulations to finer scales remain grand challenges in Earth system science. Downscaling often involves inferring subgrid information from coarse-scale data, and such ill-posed problems are classically addressed using regularization. Here, we apply two-dimensional Tikhonov Regularization (2DTR) to simulate subgrid surface patterns for ecological applications. Specifically, we test the ability of 2DTR to simulate the spatial statistics of high-resolution (4 m) remote sensing observations of the normalized difference vegetation index (NDVI) in a tundra landscape. We find that the 2DTR approach as applied here can capture the major mode of spatial variability of the high-resolution information, but not multiple modes of spatial variability, and that the Lagrange multiplier (γ) used to impose the condition of smoothness across space is related to the range of the experimental semivariogram. We used observed and 2DTR-simulated maps of NDVI to estimate landscape-level leaf area index (LAI) and gross primary productivity (GPP). NDVI maps simulated using a γ value that approximates the range of observed NDVI result in a landscape-level GPP estimate that differs by ca 2% from those created using observed NDVI. Following findings that GPP per unit LAI is lower near vegetation patch edges, we simulated vegetation patch edges using multiple approaches and found that simulated GPP declined by up to 12% as a result. 2DTR can generate random landscapes rapidly and can be applied to disaggregate ecological information and compare of spatial observations against simulated landscapes.

  14. Mixed Interaction Spaces

    DEFF Research Database (Denmark)

    Lykke-Olesen, Andreas; Eriksson, E.; Hansen, T.R.

    In this paper, we describe a new interaction technique for mobile devices named Mixed Interaction Space that uses the camera of the mobile device to track the position, size and rotation of a fixed-point. In this demonstration we will present a system that uses a hand-drawn circle, colored object...

  15. Mediterranean Outflow Mixing Dynamics

    Science.gov (United States)

    1993-02-01

    34 26 FEBRUARY 1993 Our hydrographic data show that the identity at least as far south as the tropics. ( Sociedad Espanola de Estudios para la Commu...mixing that in- tic , it has properties that make it neutrally of the marginal seas, and second, to allow corporates overlying North Atlantic water into

  16. Glueball-meson mixing

    Energy Technology Data Exchange (ETDEWEB)

    Vento, Vicente [Consejo Superior de Investigaciones Cientificas, Departamento de Fisica Teorica y Instituto de Fisica Corpuscular, Universidad de Valencia, Burjassot (Spain)

    2016-01-15

    Calculations in unquenched QCD for the scalar glueball spectrum have confirmed previous results of Gluodynamics finding a glueball at ∝1750 MeV. I analyze the implications of this discovery from the point of view of glueball-meson mixing in light of the experimental scalar spectrum. (orig.)

  17. Mixed-Initiative Clustering

    Science.gov (United States)

    Huang, Yifen

    2010-01-01

    Mixed-initiative clustering is a task where a user and a machine work collaboratively to analyze a large set of documents. We hypothesize that a user and a machine can both learn better clustering models through enriched communication and interactive learning from each other. The first contribution or this thesis is providing a framework of…

  18. MixFit

    DEFF Research Database (Denmark)

    Haller, Toomas; Leitsalu, Liis; Fischer, Krista

    2017-01-01

    . Numerical ancestry component scores are assigned to individuals based on comparisons with reference populations. These comparisons are conducted with an existing analytical pipeline making use of genotype phasing, similarity matrix computation and our addition-multidimensional best fitting by Mix...... computer programs and scripts one of which was developed in house (available at: www.geenivaramu.ee/en/tools/mixfit)....

  19. Against Mixed Epistemology

    Directory of Open Access Journals (Sweden)

    Joe Milburn

    2015-08-01

    Full Text Available We can call any reductive account of knowledge that appeals to both safety and ability conditions a mixed account of knowledge. Examples of mixed accounts of knowledge include Pritchard’s (2012 Anti-Luck Virtue Epistemology, Kelp’s (2013 Safe-Apt account of knowledge, and Turri’s (2011 Ample belief account of knowledge. Mixed accounts of knowledge are motivated by well-known counterexamples to pure safety and pure ability accounts of knowledge. It is thought that by combining both safety and ability conditions we can give an extensionally adequate reductive account of knowledge. In this paper I argue that the putative counterexamples to pure safety and pure ability accounts of knowledge fail to motivate mixed accounts of knowledge. In particular, I argue that if the putative counterexamples are problematic for safety accounts they are problematic for ability accounts and vice-versa. The reason for this, I argue, is that the safety condition and ability condition should be understood as alternative expressions of the same intuition — that knowledge must come from a reliable source.

  20. Mixed Partnering and Parenting

    DEFF Research Database (Denmark)

    Singla, Rashmi

    Book of Abstracts ICCP 2016 This proposal deals with psychosocial intervention of couples in mixed-marriages in Denmark, which has barely been scientifically explored due to the homogeneity and colourblindness dominant discourse. The term “mixed” is used for couples who feel that their intimate r...

  1. Sylgard® Mixing Study

    Energy Technology Data Exchange (ETDEWEB)

    Bello, Mollie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Welch, Cynthia F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Goodwin, Lynne Alese [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Keller, Jennie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-08-22

    Sylgard® 184 and Sylgard® 186 silicone elastomers form Dow Corning® are used as potting agents across the Nuclear Weapons Complex. A standardized mixing procedure is required for filled versions of these products. The present study is a follow-up to a mixing study performed by MST-7 which established the best mixing procedure to use when adding filler to either 184 or 186 base resins. The most effective and consistent method of mixing resin and curing agent for three modified silicone elastomer recipes is outlined in this report. For each recipe, sample size, mixing type, and mixing time was varied over 10 separate runs. The results show that the THINKY™ Mixer gives reliable mixing over varying batch sizes and mixing times. Hand Mixing can give improved mixing, as indicated by reduced initial viscosity; however, this method is not consistent.

  2. Quantifying macro-mixing and micro-mixing in a static mixer using two-tracer laser-induced fluorescence

    Science.gov (United States)

    Lehwald, Andreas; Thévenin, Dominique; Zähringer, Katharina

    2010-05-01

    An experimental procedure has been developed to quantify mixing at large scales (flow-induced) and at small scales (induced by molecular diffusion). It relies on the simultaneous imaging of two different fluorescent tracers using planar laser-induced fluorescence (PLIF). In order to quantify micro-mixing, a suitable neutralization reaction involving the fluorescent tracer uranine has been identified. Using PLIF, uranine is measured simultaneously with another fluorescent tracer, pyridine 2, employed to characterize macro-mixing. Since both tracers are quite inexpensive, this procedure allows an in-depth characterization of mixing properties even in large installations, by measuring the concentration fields of the involved tracers in a non-intrusive manner. This measurement procedure has been applied to a static mixer segment with geometrical features and dimensions similar to that found in practical applications. Laminar inflow conditions are employed. The flow and mixing analysis obtained by post-processing the measurement results is detailed in the present article.

  3. Hawaii Ocean Mixing Experiment: Program Summary

    Science.gov (United States)

    Ray, Richard D.; Chao, Benjamin F. (Technical Monitor)

    2002-01-01

    It is becoming apparent that insufficient mixing occurs in the pelagic ocean to maintain the large scale thermohaline circulation. Observed mixing rates fall a factor of ten short of classical indices such as Munk's "Abyssal Recipe." The growing suspicion is that most of the mixing in the sea occurs near topography. Exciting recent observations by Polzin et al., among others, fuel this speculation. If topographic mixing is indeed important, it must be acknowledged that its geographic distribution, both laterally and vertically, is presently unknown. The vertical distribution of mixing plays a critical role in the Stommel Arons model of the ocean interior circulation. In recent numerical studies, Samelson demonstrates the extreme sensitivity of flow in the abyssal ocean to the spatial distribution of mixing. We propose to study the topographic mixing problem through an integrated program of modeling and observation. We focus on tidally forced mixing as the global energetics of this process have received (and are receiving) considerable study. Also, the well defined frequency of the forcing and the unique geometry of tidal scattering serve to focus the experiment design. The Hawaiian Ridge is selected as a study site. Strong interaction between the barotropic tide and the Ridge is known to take place. The goals of the Hawaiian Ocean Mixing Experiment (HOME) are to quantify the rate of tidal energy loss to mixing at the Ridge and to identify the mechanisms by which energy is lost and mixing generated. We are challenged to develop a sufficiently comprehensive picture that results can be generalized from Hawaii to the global ocean. To achieve these goals, investigators from five institutions have designed HOME, a program of historic data analysis, modeling and field observation. The Analysis and Modeling efforts support the design of the field experiments. As the program progresses, a global model of the barotropic (depth independent) tide, and two models of the

  4. Chaotic mixing by microswimmers moving on quasiperiodic orbits

    Science.gov (United States)

    Jalali, Mir Abbas; Khoshnood, Atefeh; Alam, Mohammad-Reza

    2015-11-01

    Life on the Earth is strongly dependent upon mixing across a vast range of scales. For example, mixing distributes nutrients for microorganisms in aquatic environments, and balances the spatial energy distribution in the oceans and the atmosphere. From industrial point of view, mixing is essential in many microfluidic processes and lab-on-a-chip operations, polymer engineering, pharmaceutics, food engineering, petroleum engineering, and biotechnology. Efficient mixing, typically characterized by chaotic advection, is hard to achieve in low Reynolds number conditions because of the linear nature of the Stokes equation that governs the motion. We report the first demonstration of chaotic mixing induced by a microswimmer that strokes on quasiperiodic orbits with multi-loop turning paths. Our findings can be utilized to understand the interactions of microorganisms with their environments, and to design autonomous robotic mixers that can sweep and mix an entire volume of complex-geometry containers.

  5. PREFACE: Turbulent Mixing and Beyond Turbulent Mixing and Beyond

    Science.gov (United States)

    Abarzhi, Snezhana I.; Gauthier, Serge; Rosner, Robert

    2008-10-01

    The goals of the International Conference `Turbulent Mixing and Beyond' are to expose the generic problem of Turbulence and Turbulent Mixing in Unsteady Flows to a wide scientific community, to promote the development of new ideas in tackling the fundamental aspects of the problem, to assist in the application of novel approaches in a broad range of phenomena, where the non-canonical turbulent processes occur, and to have a potential impact on technology. The Conference provides the opportunity to bring together scientists from the areas which include, but are not limited to, high energy density physics, plasmas, fluid dynamics, turbulence, combustion, material science, geophysics, astrophysics, optics and telecommunications, applied mathematics, probability and statistics, and to have their attention focused on the long-standing formidable task. The Turbulent Mixing and Turbulence in Unsteady Flows, including multiphase flows, plays a key role in a wide variety of phenomena, ranging from astrophysical to nano-scales, under either high or low energy density conditions. Inertial confinement and magnetic fusion, light-matter interaction and non-equilibrium heat transfer, properties of materials under high strain rates, strong shocks, explosions, blast waves, supernovae and accretion disks, stellar non-Boussinesq and magneto-convection, planetary interiors and mantle-lithosphere tectonics, premixed and non-premixed combustion, oceanography, atmospheric flows, unsteady boundary layers, hypersonic and supersonic flows, are a few examples to list. A grip on unsteady turbulent processes is crucial for cutting-edge technology such as laser-micromachining and free-space optical telecommunications, and for industrial applications in aeronautics. Unsteady Turbulent Processes are anisotropic, non-local and multi-scale, and their fundamental scaling, spectral and invariant properties depart from the classical Kolmogorov scenario. The singular aspects and similarity of the

  6. Psychoacoustic Approaches for Harmonic Music Mixing

    Directory of Open Access Journals (Sweden)

    Roman B. Gebhardt

    2016-05-01

    Full Text Available The practice of harmonic mixing is a technique used by DJs for the beat-synchronous and harmonic alignment of two or more pieces of music. In this paper, we present a new harmonic mixing method based on psychoacoustic principles. Unlike existing commercial DJ-mixing software, which determines compatible matches between songs via key estimation and harmonic relationships in the circle of fifths, our approach is built around the measurement of musical consonance. Given two tracks, we first extract a set of partials using a sinusoidal model and average this information over sixteenth note temporal frames. By scaling the partials of one track over ±6 semitones (in 1/8th semitone steps, we determine the pitch-shift that maximizes the consonance of the resulting mix. For this, we measure the consonance between all combinations of dyads within each frame according to psychoacoustic models of roughness and pitch commonality. To evaluate our method, we conducted a listening test where short musical excerpts were mixed together under different pitch shifts and rated according to consonance and pleasantness. Results demonstrate that sensory roughness computed from a small number of partials in each of the musical audio signals constitutes a reliable indicator to yield maximum perceptual consonance and pleasantness ratings by musically-trained listeners.

  7. Quantifying mixing using magnetic resonance imaging.

    Science.gov (United States)

    Tozzi, Emilio J; McCarthy, Kathryn L; Bacca, Lori A; Hartt, William H; McCarthy, Michael J

    2012-01-25

    Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media (1, 2). The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile (1)H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for

  8. Organic aerosol mixing observed by single-particle mass spectrometry.

    Science.gov (United States)

    Robinson, Ellis Shipley; Saleh, Rawad; Donahue, Neil M

    2013-12-27

    We present direct measurements of mixing between separately prepared organic aerosol populations in a smog chamber using single-particle mass spectra from the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Docosane and docosane-d46 (22 carbon linear solid alkane) did not show any signs of mixing, but squalane and squalane-d62 (30 carbon branched liquid alkane) mixed on the time scale expected from a condensational-mixing model. Docosane and docosane-d46 were driven to mix when the chamber temperature was elevated above the melting point for docosane. Docosane vapors were shown to mix into squalane-d62, but not the other way around. These results are consistent with low diffusivity in the solid phase of docosane particles. We performed mixing experiments on secondary organic aerosol (SOA) surrogate systems finding that SOA derived from toluene-d8 (a surrogate for anthropogenic SOA (aSOA)) does not mix into squalane (a surrogate for hydrophobic primary organic aerosol (POA)) but does mix into SOA derived from α-pinene (biogenic SOA (bSOA) surrogate). For the aSOA/POA, the volatility of either aerosol does not limit gas-phase diffusion, indicating that the two particle populations do not mix simply because they are immiscible. In the aSOA/bSOA system, the presence of toluene-d8-derived SOA molecules in the α-pinene-derived SOA provides evidence that the diffusion coefficient in α-pinene-derived SOA is high enough for mixing on the time scale of 1 min. The observations from all of these mixing experiments are generally invisible to bulk aerosol composition measurements but are made possible with single-particle composition data.

  9. Concepts of scale and scaling

    Science.gov (United States)

    Jianguo Wu; Harbin Li

    2006-01-01

    The relationship between pattern and process is of great interest in all natural and social sciences, and scale is an integral part of this relationship. It is now well documented that biophysical and socioeconomic patterns and processes operate on a wide range of spatial and temporal scales. In particular, the scale multiplicity and scale dependence of pattern,...

  10. Charm lifetimes and mixing

    Energy Technology Data Exchange (ETDEWEB)

    Harry W.K. Cheung

    2001-11-28

    A review of the latest results on charm lifetimes and D-mixing is presented. The e{sup +}e{sup -} collider experiments are now able to measure charm lifetimes quite precisely, however comparisons with the latest results from fixed-target experiments show that possible systematic effects could be evident. The new D-mixing results from the B-factories have changed the picture that is emerging. Although the new world averaged value of y{sub CP} is now consistent with zero, there is still a very interesting and favored scenario if the strong phase difference between the Doubly-Cabibbo-suppressed and the Cabibbo-flavored D{sup 0} {yields} K{pi} decay is large.

  11. Renormalization of fermion mixing

    Energy Technology Data Exchange (ETDEWEB)

    Schiopu, R.

    2007-05-11

    Precision measurements of phenomena related to fermion mixing require the inclusion of higher order corrections in the calculation of corresponding theoretical predictions. For this, a complete renormalization scheme for models that allow for fermion mixing is highly required. The correct treatment of unstable particles makes this task difficult and yet, no satisfactory and general solution can be found in the literature. In the present work, we study the renormalization of the fermion Lagrange density with Dirac and Majorana particles in models that involve mixing. The first part of the thesis provides a general renormalization prescription for the Lagrangian, while the second one is an application to specific models. In a general framework, using the on-shell renormalization scheme, we identify the physical mass and the decay width of a fermion from its full propagator. The so-called wave function renormalization constants are determined such that the subtracted propagator is diagonal on-shell. As a consequence of absorptive parts in the self-energy, the constants that are supposed to renormalize the incoming fermion and the outgoing antifermion are different from the ones that should renormalize the outgoing fermion and the incoming antifermion and not related by hermiticity, as desired. Instead of defining field renormalization constants identical to the wave function renormalization ones, we differentiate the two by a set of finite constants. Using the additional freedom offered by this finite difference, we investigate the possibility of defining field renormalization constants related by hermiticity. We show that for Dirac fermions, unless the model has very special features, the hermiticity condition leads to ill-defined matrix elements due to self-energy corrections of external legs. In the case of Majorana fermions, the constraints for the model are less restrictive. Here one might have a better chance to define field renormalization constants related by

  12. Observation of Bs mixing

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    A peculiar and most important property of Bs mesons is that they transform spontaneously into their own antiparticles, and back again. These transitions, known as flavor oscillations or mixing, are extremely rapid, rendering their measurement a very challenging experimental task. The determination of the Bs oscillation frequency is, at the same time, of great interest for constraining elements of the Standard Model CKM matrix and its unitarity. Large samples of Bs mesons collected by the CDF and D0 experiments operating at the Fermilab Tevatron have recently yielded unprecedented results, which are here reported. Emphasis is given to details of the analysis developed at CDF, presenting the observation of Bs mixing, the precise measurement of the oscillation frequency, and a discussion of its impact on the description of the flavor sector.

  13. DYPTOP: a cost-efficient TOPMODEL implementation to simulate sub-grid spatio-temporal dynamics of global wetlands and peatlands

    Directory of Open Access Journals (Sweden)

    B. D. Stocker

    2014-12-01

    TOPMODEL (DYPTOP, which predicts the extent of inundation based on a computationally efficient TOPMODEL implementation. This approach rests on an empirical, grid-cell-specific relationship between the mean soil water balance and the flooded area. DYPTOP combines the simulated inundation extent and its temporal persistency with criteria for the ecosystem water balance and the modelled peatland-specific soil carbon balance to predict the global distribution of peatlands. We apply DYPTOP in combination with the LPX-Bern DGVM and benchmark the global-scale distribution, extent, and seasonality of inundation against satellite data. DYPTOP successfully predicts the spatial distribution and extent of wetlands and major boreal and tropical peatland complexes and reveals the governing limitations to peatland occurrence across the globe. Peatlands covering large boreal lowlands are reproduced only when accounting for a positive feedback induced by the enhanced mean soil water holding capacity in peatland-dominated regions. DYPTOP is designed to minimize input data requirements, optimizes computational efficiency and allows for a modular adoption in Earth system models.

  14. Marketing Mix in Services

    OpenAIRE

    Cătălin Grădinaru; Sorin-George Toma; Paul Marinescu

    2016-01-01

    In a hypercompetitive environment, one in which it is difficult to gain substantial competitiveadvantages, it is becoming harder and harder to differentiate yourself from the rest, especially whenactivating in the services field. In order for a company to scientifically act, react and manage to satisfyas well as possible the customer’s needs, it should carry out a rigorous management process ofservices marketing. In the past, the marketing mix comprised 4Ps: product, price, place and promotio...

  15. Bounded Stochastic Shell Mixing Model: Further Development and Application to Inhomogeneous Scalar Mixing

    Science.gov (United States)

    Vaithianathan, T.; Xia, Yanjun; Collins, Lance R.

    2011-11-01

    Xia and Collins [Physics of Fluids 23 (6):065107, 2011] developed the Bounded Stochastic Shell Mixing (BSSM) model that takes into account the multi-scale nature of the turbulent mixing process. They successfully applied the model to mixing of isotropic scalars with an initial double-delta probability density function (PDF). To enforce the scalar bounds, they introduced a novel ``zeroth mode'' that precisely cancels the inherently non-conservative random terms in the formulation. The extension of the model to the mixing of inhomogeneous scalar fields uses notional particles that move with a fluctuating velocity that is chosen to conform with the underlying turbulent energy spectrum. A consistency condition further requires the particle motion in the direction of the mean scalar gradient be carefully connected to the generation of the scalar fluctuation. The appropriate constraint has been derived and is enforced by the numerical algorithm. This new formulation has been applied to turbulent mixing of a scalar slab of specified thickness. (In the limit of zero thickness, this reduces to the classical ``line source'' problem.) We analyze multiple scalars so that differential diffusion can be considered as well as the effect of the thickness of the slab (relative to the turbulence length scales). The predictions of the BSSM model compare well with direct numerical simulations.

  16. Mixing of solids

    CERN Document Server

    Weinekötter, Ralf

    2000-01-01

    This book is a welcome edition to the Particle Technology Series, formerly Powder Technology Series. It is the second book in the series which describes powder mixing and we make no excuses for that. The topic of powder mixing is fundamental to powder technology and is one which always aroses interest. That will not change. As powder products become more complex they will pose new mixing problems. The solutions lie in the intelligent use of equipment, an understanding of powder properties and a good knowledge of basic statistics. The authors of this book have presented those three ingredients with great clarity. The book is based on long experience and deep thought, I have enjoyed reading it and am pleased to recommend it. Delft University of Technology, NL-Delft, July 1999 Brian Scarlett, Series Editor IX VII Foreword to the English Edition In response to many enquiries from industrial organisations and institutes involved with the technology of processing bulk materials, we are pleased to present the Englis...

  17. MARKETING MIX IN SPORT

    Directory of Open Access Journals (Sweden)

    Srećko Novaković

    2011-03-01

    Full Text Available Marketing mix'' along the term of life cycle has robbed the trademark for the conception of marketing and the market direction of company, corporations and institutions. Essence marketing-mixa is in the simultaneous determining of the target market group of consumer (the buyer or stays the public and specially prepared and the coordinated impact of elements mixa, and this is the product, price, distributions and graduation ceremonies. Given that is mix combinations of verified variables, companies he use in order to would achieve are wished the scope sales on the target market. In the wider context significant influence of environment on the chosen structure marketing-mixa have not only technological, economic and competitive services already and socially-owned, legislative, legal and political services. From those reasons chant the marketing -mixa occasionally replaces expression are coordinated term acts on the market. Elements marketing-mix-and at sport marketings same are as well as at marketings every other activity. They contain the sportively product and the service, appreciate the sport product and services, distribution of sport product and services and the promotion of sport product and services.

  18. Refractive Microstructure From Diffusive And Turbulent Ocean Mixing

    Science.gov (United States)

    Williams, Albert J., III

    1980-02-01

    Small scale fluctuations in refractive index can affect visibility and image quality in ocean optics. Such fluctuations are a result of temperature and salinity microstructure. Ocean mixing proceeds by the stirring together of dissimilar water types at finer and finer scales until diffusion creates a water type intermediate to the original components. Optically, the most important scale in the mixing cascade is microstructure because it consists of the highest gradient and smallest scale structures. Two classes of mixing process have been distinguished by shadowgraph images made in conjunction with profiles of temperature, salinity, and velocity shear. One class is diffusive and depends on the vertical distribution of temperature and salinity. The other class is turbulent and depends on velocity shear.

  19. Photosynthetic efficiency of Chlorella sorokiniana in a turbulently mixed short light-path photobioreactor

    NARCIS (Netherlands)

    Kliphuis, A.M.J.; Winter, de L.; Vejrazka, C.; Martens, D.E.; Janssen, M.G.J.; Wijffels, R.H.

    2010-01-01

    To be able to study the effect of mixing as well as any other parameter on productivity of algal cultures, we designed a lab-scale photobioreactor in which a short light path (SLP) of (12 mm) is combined with controlled mixing and aeration. Mixing is provided by rotating an inner tube in the

  20. Quantitative diagnostics of stratospheric mixing

    Science.gov (United States)

    Sobel, Adam Harrison

    1998-12-01

    This thesis addresses the planetary-scale mixing of tracers along isentropic surfaces in the extratropical winter stratosphere. The primary goal is a more fully quantitative understanding of the mixing than is available at present. The general problem of representing eddy mixing in a one- dimensional mean representation of a two-dimensional flow is discussed. The limitations of the eddy diffusion model are reviewed, and alternatives explored. The stratosphere may, for some purposes, be viewed as consisting of relatively well-mixed regions separated by moving, internal transport barriers. Methods for diagnosing transport across moving surfaces, such as tracer isosurfaces, from given flow and tracer fields are reviewed. The central results of the thesis involve diagnostic studies of output from a shallow water model of the stratosphere. It is first proved that in an inviscid shallow water atmosphere subject to mass sources and sinks, if the mass enclosed by a potential vorticity (PV) contour is steady in time, then the integral of the mass source over the area enclosed by the contour must be zero. Next, two different approaches are used to diagnose the time-averaged transport across PV contours in the model simulations. The first is the modified Lagrangian mean (MLM) approach, which relates the transport across PV contours to PV sources and sinks. The second is called 'local gradient reversal' (LGR), and is similar to contour advection with surgery. The model includes a sixth-order hyperdiffusion on the vorticity field. Except in a thin outer 'entrainment zone', the hyperdiffusion term has only a very weak effect on the MLM mass budget of the polar vortex edge. In the entrainment zone, the hyperdiffusion term has a significant effect. The LGR results capture this behavior, providing good quantitative estimates of the hyperdiffusion term, which is equivalent to the degree of radiative disequilibrium at a PV contour. This agreement shows that the main role of the

  1. Pre-Mix and on-site mixing of fumigants

    OpenAIRE

    Ryan, R F; Shore, W. P.

    2010-01-01

    Pre-Mix or On-Site mixing, a common practice with liquid insecticides, has benefits of increased synergy with fumigants. Both Pre-Mix and On-Site mixing have some issues with compatibility (e.g., active ingredient chemical stability; material compatibility; reaction with other ingredients). In addition to its fumigant properties, carbon dioxide (CO₂), has a synergistic effect on other fumigants and reduces flammability. The general consensus on the amount of CO₂ to improve efficacy is in the ...

  2. Calculation of collisional mixing

    Science.gov (United States)

    Koponen, I.; Hautala, M.

    1990-06-01

    Collisional mixing of markers is calculated by splitting the calculation into two parts. Relocation cross sections have been calculated using a realistic potential in a Monte Carlo simulation. The cross sections are used in the computation of marker relocation. The cumulative effect of successive relocations is assumed to be an uncorrelated transport process and it is treated as a weighted random walk. Matrix relocation was not included in the calculations. The results from this two-step simulation model are compared with analytical models. A fit to the simulated differential relocation cross sections has been found which makes the numerical integration of the Bothe formula feasible. The influence of primaries has been treated in this way. When all the recoils are included the relocation profiles are nearly Gaussian and the Pearson IV distributions yield acceptable profiles in the studied cases. The approximations and cut-off procedures which cause the major uncertainties in calculations are pointed out. The choice of the cut-off energy is shown to be the source of the largest uncertainty whereas the mathematical approximations can be used with good accuracy. The methods are used to study the broadening of a Pt marker in Si mixed by 300 keV Xe ions, broadening of a Ti marker in Al mixed by 300 keV Xe ions and broadening of a Ti marker in Hf mixed by 750 keV Kr ions. The fluence in each case is 2 × 10 16{ions}/{cm 2}. The calculated averages of half widths at half maximum vary between 11-18, 9-12 and 10-15 nm, respectively, depending on the cut-off energy and the mixing efficiencies vary between 11-29, 6-11 and 6-14 {Å5}/{eV}, respectively. The broadenings of Pt in Si and Ti in Al are about two times smaller than the measured values and the broadening of Ti in Hf is in agreement with the measured values.

  3. MixSIAR: advanced stable isotope mixing models in R

    Science.gov (United States)

    Background/Question/Methods The development of stable isotope mixing models has coincided with modeling products (e.g. IsoSource, MixSIR, SIAR), where methodological advances are published in parity with software packages. However, while mixing model theory has recently been ex...

  4. The Value of Mixed Methods Research: A Mixed Methods Study

    Science.gov (United States)

    McKim, Courtney A.

    2017-01-01

    The purpose of this explanatory mixed methods study was to examine the perceived value of mixed methods research for graduate students. The quantitative phase was an experiment examining the effect of a passage's methodology on students' perceived value. Results indicated students scored the mixed methods passage as more valuable than those who…

  5. Calvin’s election mix in small-scale theology

    Directory of Open Access Journals (Sweden)

    James A. Loader

    2009-11-01

    Full Text Available This paper shows how Calvin’s ideas about the Old Testament concept of Israel’s election can be dangerous when they are applied uncritically. The main illustration material is drawn from a context the author was himself part of, notably the South African apartheid theology of Calvinist provenance. The paper begins with documenting Calvin’s views on Israel and Israel’s election in the Old Testament, moving to a consideration of how this motif was connected to the idea of predestination and construed to become an instrument to defend apartheid in what may be called a substandard theology. It is suggested that a glance at the English-speaking world shows surprising similarities that justify further consideration. In this title several dimensions are present that need to be explicated.

  6. Calvin's election mix in small-scale theology | Loader | HTS ...

    African Journals Online (AJOL)

    This paper shows how Calvin's ideas about the Old Testament concept of Israel's election can be dangerous when they are applied uncritically. The main illustration material is drawn from a context the author was himself part of, notably the South African apartheid theology of Calvinist provenance. The paper begins with ...

  7. Mixed Method Research: An Overview

    OpenAIRE

    Dewan Mahboob HOSSAIN

    2012-01-01

    This article gives a general overview of mixed method research. In mixed method, the researchers combine both qualitative and quantitative approaches in a single research project. The article first attempts to define mixed method research. Then it gives a comparison of qualitative and quantitative approaches. It also introduces the well-known controversy among the researchers: which of these approaches is superior? By explaining this controversy, the article identifies the need for mixed meth...

  8. Boundary mixing in Orkney Passage outflow

    Science.gov (United States)

    Polzin, K. L.; Garabato, A. C. Naveira; Abrahamsen, E. P.; Jullion, L.; Meredith, M. P.

    2014-12-01

    One of the most remarkable features of contemporary oceanic climate change is the warming and contraction of Antarctic Bottom Water over much of global ocean abyss. These signatures represent changes in ventilation mediated by mixing and entrainment processes that may be location-specific. Here we use available data to document, as best possible, those mixing processes as Weddell Sea Deep and Bottom Waters flow along the South Orkney Plateau, exit the Weddell Sea via Orkney Passage and fill the abyssal Scotia Sea. First, we find that an abrupt transition in topography upstream of Orkney Passage delimits the extent of the coldest waters along the Plateau's flanks and may indicate a region of especially intense mixing. Second, we revisit a control volume budget by Heywood et al. (2002) for waters trapped within the Scotia Sea after entering through Orkney Passage. This budget requires extremely vigorous water mass transformations with a diapycnal transfer coefficient of 39>(±10>)×10-4 m2 s-1. Evidence for such intense diapycnal mixing is not found in the abyssal Scotia Sea interior and, while we do find large rates of diapycnal mixing in conjunction with a downwelling Ekman layer on the western side of Orkney Passage, it is insufficient to close the budget. This leads us to hypothesize that the Heywood budget is closed by a boundary mixing process in which the Ekman layer associated with the Weddell Sea Deep Water boundary current experiences relatively large vertical scale overturning associated with tidal forcing along the southern boundary of the Scotia Sea.

  9. Lagrangian Studies of Lateral Mixing

    Science.gov (United States)

    2017-09-19

    the Gulf Stream warm core, Ro and Rig O(1) at the Gulf Stream north wall) allowed for efficient investigation of submesoscale mixing resulting from...Float and dye revealed energetic mixing in the negative PV region, with dye spreading indicating lateral mixing rates of ~100 m2/s. Please see

  10. Magnetically coupled system for mixing

    Energy Technology Data Exchange (ETDEWEB)

    Miller, III, Harlan; Meichel, George; Legere, Edward; Malkiel, Edwin; Woods, Robert Paul; Ashley, Oliver; Katz, Joseph; Ward, Jason; Petersen, Paul

    2015-09-22

    The invention provides a mixing system comprising a magnetically coupled drive system and a foil for cultivating algae, or cyanobacteria, in an open or enclosed vessel. The invention provides effective mixing, low energy usage, low capital expenditure, and ease of drive system component maintenance while maintaining the integrity of a sealed mixing vessel.

  11. Extended Mixed Vector Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Mijanur Rahaman

    2014-01-01

    Full Text Available We study extended mixed vector equilibrium problems, namely, extended weak mixed vector equilibrium problem and extended strong mixed vector equilibrium problem in Hausdorff topological vector spaces. Using generalized KKM-Fan theorem (Ben-El-Mechaiekh et al.; 2005, some existence results for both problems are proved in noncompact domain.

  12. Coloring mixed hypergraphs

    CERN Document Server

    Voloshin, Vitaly I

    2002-01-01

    The theory of graph coloring has existed for more than 150 years. Historically, graph coloring involved finding the minimum number of colors to be assigned to the vertices so that adjacent vertices would have different colors. From this modest beginning, the theory has become central in discrete mathematics with many contemporary generalizations and applications. Generalization of graph coloring-type problems to mixed hypergraphs brings many new dimensions to the theory of colorings. A main feature of this book is that in the case of hypergraphs, there exist problems on both the minimum and th

  13. MixedNotes

    DEFF Research Database (Denmark)

    Jokela, Tero; Lucero, Andrés

    2014-01-01

    Affinity Diagramming is a technique to organize and make sense of qualitative data. It is commonly used in Contextual Design and HCI research. However, preparing notes for and building an Affinity Diagram remains a laborious process, with a wide variety of different approaches and practices....... In this paper, we present MixedNotes, a novel technique to prepare physical paper notes for Affinity Diagramming, and a software tool to support this technique. The technique has been tested with large real-life Affinity Diagrams with overall positive results....

  14. A CFD model for determining mixing and mass transfer in a high power agitated bioreactor

    OpenAIRE

    Bach, Christian; Albæk, Mads O.; Stocks, Stuart M.; Krühne, Ulrich; Gernaey, Krist V.

    2016-01-01

    Prediction of mixing and mass transfer in agitated systems is a vital tool for process development and scale up in industrial biotechnology. In particular key process parameters such as mixing time and kLa are essential for bioprocess development [1]. In this work the mixing and mass transfer performance of a high power agitated pilot scale bioreactor has been characterized using a novel combination of computational fluid dynamics (CFD) and experimental investigations. The effect of turbulenc...

  15. Pulse Jet Mixing Tests With Noncohesive Solids

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Perry A.; Bamberger, Judith A.; Enderlin, Carl W.; Fort, James A.; Wells, Beric E.; Sundaram, S. K.; Scott, Paul A.; Minette, Michael J.; Smith, Gary L.; Burns, Carolyn A.; Greenwood, Margaret S.; Morgen, Gerald P.; Baer, Ellen BK; Snyder, Sandra F.; White, Michael; Piepel, Gregory F.; Amidan, Brett G.; Heredia-Langner, Alejandro; Bailey, Sharon A.; Bower, John C.; Denslow, Kayte M.; Eakin, David E.; Elmore, Monte R.; Gauglitz, Phillip A.; Guzman, Anthony D.; Hatchell, Brian K.; Hopkins, Derek F.; Hurley, David E.; Johnson, Michael D.; Kirihara, Leslie J.; Lawler, Bruce D.; Loveland, Jesse S.; Mullen, O Dennis; Pekour, Mikhail S.; Peters, Timothy J.; Robinson, Peter J.; Russcher, Michael S.; Sande, Susan; Santoso, Christian; Shoemaker, Steven V.; Silva, Steve M.; Smith, Devin E.; Su, Yin-Fong; Toth, James J.; Wiberg, John D.; Yu, Xiao-Ying; Zuljevic, Nino

    2009-05-11

    This report summarizes results from pulse jet mixing (PJM) tests with noncohesive solids in Newtonian liquid conducted during FY 2007 and 2008 to support the design of mixing systems for the Hanford Waste Treatment and Immobilization Plant (WTP). Tests were conducted at three geometric scales using noncohesive simulants. The test data were used to independently develop mixing models that can be used to predict full-scale WTP vessel performance and to rate current WTP mixing system designs against two specific performance requirements. One requirement is to ensure that all solids have been disturbed during the mixing action, which is important to release gas from the solids. The second requirement is to maintain a suspended solids concentration below 20 weight percent at the pump inlet. The models predict the height to which solids will be lifted by the PJM action, and the minimum velocity needed to ensure all solids have been lifted from the floor. From the cloud height estimate we can calculate the concentration of solids at the pump inlet. The velocity needed to lift the solids is slightly more demanding than "disturbing" the solids, and is used as a surrogate for this metric. We applied the models to assess WTP mixing vessel performance with respect to the two perform¬ance requirements. Each mixing vessel was evaluated against these two criteria for two defined waste conditions. One of the wastes was defined by design limits and one was derived from Hanford waste characterization reports. The assessment predicts that three vessel types will satisfy the design criteria for all conditions evaluated. Seven vessel types will not satisfy the performance criteria used for any of the conditions evaluated. The remaining three vessel types provide varying assessments when the different particle characteristics are evaluated. The assessment predicts that three vessel types will satisfy the design criteria for all conditions evaluated. Seven vessel types will not satisfy

  16. Fast mixing condensation nucleus counter

    OpenAIRE

    Flagan, Richard C.; Wang, Jian

    2003-01-01

    A fast mixing condensation nucleus counter useful for detecting particles entrained in a sample gas stream is provided. The fast mixing condensation nucleus counter comprises a detector and a mixing condensation device having a mixing chamber adapted to allow gas to flow from an inlet to an outlet, wherein the outlet directs the gas flow to the detector. The mixing chamber has an inlet for introducing vapor-laden gas into the chamber and at least one nozzle for introducing a sample gas having...

  17. Multi-scale analysis of local flow topology in isotropic turbulence

    Science.gov (United States)

    Danish, Mohammad; Meneveau, Charles

    2017-11-01

    Knowledge of local flow-topology, as described by the velocity gradients, is useful to develop insights of turbulence processes, such as energy cascade, material element deformation, etc. Much has been learned in recent past about flow-topology at the smallest (viscous) scales of turbulence. However, less is known at larger (or inertial) scales of turbulence. In this work, we present a detailed study on the scale-dependence of various quantities of our interest, like population fraction of different flow-topologies, joint probability distribution of second and third invariants of velocity gradient tensor, etc. We use a new filter proposed by Eyink & Aluie to decompose the flow into small and large scales. We provide further insights for the observed behavior of scale-dependence by examining the probability fluxes appearing in the Fokker-Plank equation. Specifically, we aim to understand whether the differences observed between the viscous and inertial range are due to different effects caused by pressure, subgrid-scale or viscous stresses, or various combination thereof. For this purpose, we use the isotropic turbulence dataset at Reλ = 433 available at JHTDB and the analysis tools developed for SciServer, including FFT to evaluate filtering and gradients. Supported by the National Science Foundation (Grants No. 1507469 and 1633124).

  18. Sensitivity of the scale partition for variational multiscale large-eddy simulation of channel flow

    Science.gov (United States)

    Holmen, Jens; Hughes, Thomas J. R.; Oberai, Assad A.; Wells, Garth N.

    2004-03-01

    The variational multiscale method has been shown to perform well for large-eddy simulation (LES) of turbulent flows. The method relies upon a partition of the resolved velocity field into large- and small-scale components. The subgrid model then acts only on the small scales of motion, unlike conventional LES models which act on all scales of motion. For homogeneous isotropic turbulence and turbulent channel flows, the multiscale model can outperform conventional LES formulations. An issue in the multiscale method for LES is choice of scale partition and sensitivity of the computed results to it. This is the topic of this investigation. The multiscale formulation for channel flows is briefly reviewed. Then, through the definition of an error measure relative to direct numerical simulation (DNS) results, the sensitivity of the method to the partition between large- and small-scale motions is examined. The error in channel flow simulations, relative to DNS results, is computed for various partitions between large- and small-scale spaces, and conclusions drawn from the results.

  19. Simulation of mixing-limited reactions using a continuum approach

    Science.gov (United States)

    Barnard, Jack M.

    2017-06-01

    The limiting of reaction rates in porous media due to the imperfect mixing of reactants is a well studied phenomenon. It has been observed on both the field and laboratory scale and studied using a range of numerical techniques including continuum approaches and Lagrangian particle tracking methods. A new method is presented here for the simulation of mixing-limited reactions using continuum methods, based on the idea of separating each reactant into a mixed and an unmixed fraction, of which only the mixed fraction can react. The method is shown to be capable of producing mixing-limited reaction rates associated with one-, two-, and three-dimensional systems, and of producing outputs well fitted to the experimental data presented in Gramling et al. (2002) .

  20. Effects of incomplete mixing on chemical reactions under flow heterogeneities.

    Science.gov (United States)

    Perez, Lazaro; Hidalgo, Juan J.; Dentz, Marco

    2016-04-01

    Evaluation of the mixing process in aquifers is of primary importance when assessing attenuation of pollutants. In aquifers different hydraulic and chemical properties can increase mixing and spreading of the transported species. Mixing processes control biogeochemical transformations such as precipitation/dissolution reactions or degradation reactions that are fast compared to mass transfer processes. Reactions are local phenomena that fluctuate at the pore scale, but predictions are often made at much larger scales. However, aquifer heterogeities are found at all scales and generates flow heterogeneities which creates complex concentration distributions that enhances mixing. In order to assess the impact of spatial flow heterogeneities at pore scale we study concentration profiles, gradients and reaction rates using a random walk particle tracking (RWPT) method and kernel density estimators to reconstruct concentrations and gradients in two setups. First, we focus on a irreversible bimolecular reaction A+B → C under homogeneous flow to distinguish phenomena of incomplete mixing of reactants from finite-size sampling effects. Second, we analise a fast reversible bimolecular chemical reaction A+B rightleftharpoons C in a laminar Poiseuille flow reactor to determine the difference between local and global reaction rates caused by the incomplete mixing under flow heterogeneities. Simulation results for the first setup differ from the analytical solution of the continuum scale advection-dispersion-reaction equation studied by Gramling et al. (2002), which results in an overstimation quantity of reaction product (C). In the second setup, results show that actual reaction rates are bigger than the obtained from artificially mixing the system by averaging the concentration vertically. - LITERATURE Gramling, C. M.,Harvey, C. F., Meigs, and L. C., (2002). Reactive transport in porous media: A comparison of model prediction with laboratory visualization, Environ. Sci

  1. Representation of the Antarctic circumpolar vortex mixing barrier in a Global Climate Model

    Science.gov (United States)

    Cameron, Chris; Conway, Jono; Bodeker, Greg; Renwick, James

    2017-04-01

    Dynamical processes that occur in the stratosphere between 15 and 50 km above Earth's surface can affect circulation in the troposphere and have an impact on weather and climate. The Antarctic Circumpolar Vortex (ACV) forms each winter and spring as a zone of strong stratospheric westerly winds surrounding Antarctica. The ACV presents a barrier to transport of air masses between middle and high-latitudes, and contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for ozone loss. The processes controlling the permeability of the ACV, and how they are likely to respond to a changing climate and a recovering ozone hole, have not been well studied, and as a result are not well simulated in Global Climate Models, particularly in terms of sub-grid scale turbulent diffusion which is parameterized in the models. The UK Met Office Unified Model (UM) is used to examine vortex permeability using both the "New Dynamics" and the upgraded "ENDGame" dynamical cores. Results are compared against reanalysis representations of vortex permeability using the MERRA-2 and ERA-Interim reanalyses data sets, which have been shown to have superior performance in the Southern Hemisphere stratosphere when compared against NCEP-CFSR, and MERRA reanalyses. Results are expected to lead to improved representation of ACV transport process in Global Climate Models and subsequent improvements in climate modelling.

  2. Quantum Groups, Property (T), and Weak Mixing

    Science.gov (United States)

    Brannan, Michael; Kerr, David

    2017-11-01

    For second countable discrete quantum groups, and more generally second countable locally compact quantum groups with trivial scaling group, we show that property (T) is equivalent to every weakly mixing unitary representation not having almost invariant vectors. This is a generalization of a theorem of Bekka and Valette from the group setting and was previously established in the case of low dual by Daws, Skalski, and Viselter. Our approach uses spectral techniques and is completely different from those of Bekka-Valette and Daws-Skalski-Viselter. By a separate argument we furthermore extend the result to second countable nonunimodular locally compact quantum groups, which are shown in particular not to have property (T), generalizing a theorem of Fima from the discrete setting. We also obtain quantum group versions of characterizations of property (T) of Kerr and Pichot in terms of the Baire category theory of weak mixing representations and of Connes and Weiss in terms of the prevalence of strongly ergodic actions.

  3. Marketing mix and competitiveness

    Directory of Open Access Journals (Sweden)

    Anđelković Slobodan

    2007-01-01

    Full Text Available Competitiveness cannot simply be viewed as a country's ability to export or generate trade surpluses, since these can be brought about at least temporarily by means of artificially lowering the exchange rate and/or compressing domestic expenditures, as has been done in recent years by many DC that have tried to adjust to diminished resource availability. Authors standpoint is that international competitiveness requires creating comparative advantage where it does not exist, and requires action on several levels including an emerging consensus on the importance of macroeconomic policy, role and accountability of the government as well as the imperative of developing and internalizing technology body of knowledge for achieving competitiveness. Particular attention is given to the role and impact of marketing instruments marketing mix.

  4. Chaotic mixing and mixing efficiency in a short time

    Science.gov (United States)

    Funakoshi, Mitsuaki

    2008-01-01

    Several studies of the chaotic motion of fluid particles by two-dimensional time-periodic flows or three-dimensional steady flows, called Lagrangian chaos, are first introduced. Secondly, some of the studies on efficient mixing caused by Lagrangian chaos, called chaotic mixing, are reviewed with discussion of several indices for the estimation of mixing efficiency. Finally, several indices to estimate the efficiency of mixing in a short time, such as those related to transport matrices, stable and unstable manifolds of hyperbolic periodic points of Poincaré maps, and lines of separation, are explained by showing examples of mixing by two-dimensional time-periodic flows between eccentric rotating cylinders and mixing by three-dimensional steady flows in a model of static mixers.

  5. A first large-scale flood inundation forecasting model

    Science.gov (United States)

    Schumann, G. J.-P.; Neal, J. C.; Voisin, N.; Andreadis, K. M.; Pappenberger, F.; Phanthuwongpakdee, N.; Hall, A. C.; Bates, P. D.

    2013-10-01

    At present continental to global scale flood forecasting predicts at a point discharge, with little attention to detail and accuracy of local scale inundation predictions. Yet, inundation variables are of interest and all flood impacts are inherently local in nature. This paper proposes a large-scale flood inundation ensemble forecasting model that uses best available data and modeling approaches in data scarce areas. The model was built for the Lower Zambezi River to demonstrate current flood inundation forecasting capabilities in large data-scarce regions. ECMWF ensemble forecast (ENS) data were used to force the VIC (Variable Infiltration Capacity) hydrologic model, which simulated and routed daily flows to the input boundary locations of a 2-D hydrodynamic model. Efficient hydrodynamic modeling over large areas still requires model grid resolutions that are typically larger than the width of channels that play a key role in flood wave propagation. We therefore employed a novel subgrid channel scheme to describe the river network in detail while representing the floodplain at an appropriate scale. The modeling system was calibrated using channel water levels from satellite laser altimetry and then applied to predict the February 2007 Mozambique floods. Model evaluation showed that simulated flood edge cells were within a distance of between one and two model resolutions compared to an observed flood edge and inundation area agreement was on average 86%. Our study highlights that physically plausible parameter values and satisfactory performance can be achieved at spatial scales ranging from tens to several hundreds of thousands of km2 and at model grid resolutions up to several km2.

  6. Prevalent mixed Hölder spectra and mixed multifractal formalism in a product of continuous Besov spaces

    Science.gov (United States)

    Ben Abid, Moez

    2017-08-01

    In this work we show that the mixed Hölder spectra of a pair of functions in a prevalent set of a product of continuous Besov spaces satisfies a mixed multifractal formalism based on the wavelet leaders. The results can be easily extended for finitely many functions in a product of continuous Besov spaces. We will use the notion of the essential shyness to calculate the mixed wavelet leaders scaling function for almost every pair of functions. As far as we know this is the first application of this notion.

  7. Fluid mixing in stratified gravity currents: the Prandtl mixing length.

    Science.gov (United States)

    Odier, P; Chen, J; Rivera, M K; Ecke, R E

    2009-04-03

    Shear-induced vertical mixing in a stratified flow is a key ingredient of thermohaline circulation. We experimentally determine the vertical flux of momentum and density of a forced gravity current using high-resolution velocity and density measurements. A constant eddy-viscosity model provides a poor description of the physics of mixing, but a Prandtl mixing length model relating momentum and density fluxes to mean velocity and density gradients works well. For the average gradient Richardson number Ri(g) approximately 0.08 and a Taylor Reynolds number Re(lambda) approximately 100, the mixing lengths are fairly constant, about the same magnitude, comparable to the turbulent shear length.

  8. Maslowian Scale.

    Science.gov (United States)

    Falk, C.; And Others

    The development of the Maslowian Scale, a method of revealing a picture of one's needs and concerns based on Abraham Maslow's levels of self-actualization, is described. This paper also explains how the scale is supported by the theories of L. Kohlberg, C. Rogers, and T. Rusk. After a literature search, a list of statements was generated…

  9. Higgs scalaron mixed inflation

    Directory of Open Access Journals (Sweden)

    Yohei Ema

    2017-07-01

    Full Text Available We discuss the inflationary dynamics of a system with a non-minimal coupling between the Higgs and the Ricci scalar as well as a Ricci scalar squared term. There are two scalar modes in this system, i.e. the Higgs and the spin-zero mode of the graviton, or the scalaron. We study the two-field dynamics of the Higgs and the scalaron during inflation, and clarify the condition where inflation is dominated by the Higgs/scalaron. We also find that the cut-off scale at around the vacuum is as large as the Planck scale, and hence there is no unitarity issue, although there is a constraint on the couplings from the perturbativity of the theory at around the vacuum.

  10. Helicity scalings

    Energy Technology Data Exchange (ETDEWEB)

    Plunian, F [ISTerre, CNRS, Universite Joseph Fourier, Grenoble (France); Lessinnes, T; Carati, D [Physique Statistique et Plasmas, Universite Libre de Bruxelles (Belgium); Stepanov, R, E-mail: Franck.Plunian@ujf-grenoble.fr [Institute of Continuous Media Mechanics of the Russian Academy of Science, Perm (Russian Federation)

    2011-12-22

    Using a helical shell model of turbulence, Chen et al. (2003) showed that both helicity and energy dissipate at the Kolmogorov scale, independently from any helicity input. This is in contradiction with a previous paper by Ditlevsen and Giuliani (2001) in which, using a GOY shell model of turbulence, they found that helicity dissipates at a scale larger than the Kolmogorov scale, and does depend on the helicity input. In a recent paper by Lessinnes et al. (2011), we showed that this discrepancy is due to the fact that in the GOY shell model only one helical mode (+ or -) is present at each scale instead of both modes in the helical shell model. Then, using the GOY model, the near cancellation of the helicity flux between the + and - modes cannot occur at small scales, as it should be in true turbulence. We review the main results with a focus on the numerical procedure needed to obtain accurate statistics.

  11. Air Distribution in a Furnished Room Ventilated by Mixing Ventilation

    DEFF Research Database (Denmark)

    Nielsen, June Richter; Nielsen, Peter V.; Svidt, Kjeld

    Using isothermal full-scale experiments and two-dimensional isothermal CFD simulations it is investigated how normal office furniture influences the air movements in a room with mixing ventilation. Three different set-ups are made in the experiments and different sizes and locations of the furnit......Using isothermal full-scale experiments and two-dimensional isothermal CFD simulations it is investigated how normal office furniture influences the air movements in a room with mixing ventilation. Three different set-ups are made in the experiments and different sizes and locations...... of the furniture volume are simulated. The simulations are made in three different lengths of the room....

  12. Mixing from below in hydrothermal ore deposits

    Science.gov (United States)

    Bons, Paul D.; Gomez-Rivas, Enrique; Markl, Gregor; Walter, Bejamin

    2014-05-01

    Unconformity-related hydrothermal ore deposits typically show indications of mixing of two end-member fluids: (a) hot, deep, rock-buffered basement brines and (b) colder fluids derived from the surface or overlying sediments. The hydromechanics of bringing these fluids together from above and below remain unclear. Classical percolative Darcy-flow models are inconsistent with (1) fluid overpressure indicated by fracturing and brecciation, (2) fast fluid flow indicated by thermal disequilibrium, and (3) strong fluid composition variations on the mm-scale, indicated by fluid inclusion analyses (Bons et al. 2012; Fusswinkel et al. 2013). We propose that fluids first descend, sucked down by desiccation reactions in exhumed basement. Oldest fluids reach greatest depths, where long residence times and elevated temperatures allow them the extensively equilibrate with their host rock, reach high salinity and scavenge metals, if present. Youngest fluids can only penetrate to shallower depths and can (partially) retain signatures from their origin, for example high Cl/Br ratios from the dissolution of evaporitic halite horizons. When fluids are released from all levels of the crustal column, these fluids mix during rapid ascent to form hydrothermal ore deposits. Mixing from below provides a viable hydromechanical mechanism to explain the common phenomenon of mixed shallow and deep fluids in hydrothermal ore deposits. Bons, P.D., Elburg, M.A., Gomez-Rivas, E. 2012. A review of the formation of tectonic veins and their microstructures. J. Struct. Geol. doi:10.1016/j.jsg.2012.07.005 Fusswinkel, T., Wagner, T., Wälle, M., Wenzel, T., Heinrich, C.A., Markl, M. 2013. Fluid mixing forms basement-hosted Pb-Zn deposits: Insight from metal and halogen geochemistry of individual fluid inclusions. Geology. doi:10.1130/G34092.1

  13. Improving the representation of river-groundwater interactions in land surface modeling at the regional scale: Observational evidence and parameterization applied in the Community Land Model

    KAUST Repository

    Zampieri, Matteo

    2012-02-01

    Groundwater is an important component of the hydrological cycle, included in many land surface models to provide a lower boundary condition for soil moisture, which in turn plays a key role in the land-vegetation-atmosphere interactions and the ecosystem dynamics. In regional-scale climate applications land surface models (LSMs) are commonly coupled to atmospheric models to close the surface energy, mass and carbon balance. LSMs in these applications are used to resolve the momentum, heat, water and carbon vertical fluxes, accounting for the effect of vegetation, soil type and other surface parameters, while lack of adequate resolution prevents using them to resolve horizontal sub-grid processes. Specifically, LSMs resolve the large-scale runoff production associated with infiltration excess and sub-grid groundwater convergence, but they neglect the effect from loosing streams to groundwater. Through the analysis of observed data of soil moisture obtained from the Oklahoma Mesoscale Network stations and land surface temperature derived from MODIS we provide evidence that the regional scale soil moisture and surface temperature patterns are affected by the rivers. This is demonstrated on the basis of simulations from a land surface model (i.e., Community Land Model - CLM, version 3.5). We show that the model cannot reproduce the features of the observed soil moisture and temperature spatial patterns that are related to the underlying mechanism of reinfiltration of river water to groundwater. Therefore, we implement a simple parameterization of this process in CLM showing the ability to reproduce the soil moisture and surface temperature spatial variabilities that relate to the river distribution at regional scale. The CLM with this new parameterization is used to evaluate impacts of the improved representation of river-groundwater interactions on the simulated water cycle parameters and the surface energy budget at the regional scale. © 2011 Elsevier B.V.

  14. PREFACE Turbulent Mixing and Beyond

    Science.gov (United States)

    Abarzhi, Snezhana I.; Gauthier, Serge; Niemela, Joseph J.

    2010-12-01

    The goals of the International Conference 'Turbulent Mixing and Beyond', TMB-2009, are to expose the generic problem of non-equilibrium turbulent processes to a broad scientific community, to promote the development of new ideas in tackling the fundamental aspects of the problem, to assist in the application of novel approaches in a broad range of phenomena, where the turbulent processes occur, and to have a potential impact on technology. The Conference provides the opportunity to bring together researchers from different areas, which include but are not limited to fluid dynamics, plasmas, high energy density physics, astrophysics, material science, combustion, atmospheric and Earth sciences, nonlinear and statistical physics, applied mathematics, probability and statistics, data processing and computations, optics and telecommunications, and to have their attention focused on the long-standing formidable task of non-equilibrium processes. Non-equilibrium turbulent processes play a key role in a broad variety of phenomena spanning astrophysical to atomistic scales and high or low energy density regimes. Inertial confinement and magnetic fusion, light-matter interaction and non-equilibrium heat transfer, strong shocks and explosions, material transformation under high strain rate, supernovae and accretion disks, stellar non-Boussinesq and magneto-convection, planetary interiors and mantle-lithosphere tectonics, premixed and non-premixed combustion, non-canonical wall-bounded flows, hypersonic and supersonic boundary layers, dynamics of atmosphere and oceanography, are just a few examples. A grip on non-equilibrium turbulent processes is crucial for cutting-edge technology such as laser micro-machining, nano-electronics, free-space optical telecommunications, and for industrial applications in the areas of aeronautics and aerodynamics. Non-equilibrium turbulent processes are anisotropic, non-local, multi-scale and multi-phase, and often are driven by shocks or

  15. Concentration Distribution in a Mixing Ventilated Room

    DEFF Research Database (Denmark)

    Jensen, Rasmus Lund; Pedersen, D. N.; Nielsen, Peter Vilhelm

    2001-01-01

    Today there is an increasing focus on the importance of a proper ventilation system to obtain good working conditions in the term of air and thermal quality to ensure high productivity. Different ventilation principles are used, e.g., mixing ventilation and displacement ventilation. In order....... Full scale experiments along with a breathing thermal manikin (BTM) have been used. The results show that the location of the sources is of great importance, just as well as temperature differences. Furthermore, the concentration in the breathing zone showed large differences throughout the room....

  16. Baryogenesis through mixing of heavy Majorana neutrinos

    CERN Document Server

    Pilaftsis, Apostolos

    1999-01-01

    We review the scenario of baryogenesis through leptogenesis induced by the out-of-equilibrium decays of heavy neutrinos. We pay special attention to the resonant phenomenon of CP violation through mixing of two nearly degenerate heavy Majorana neutrinos and show how unitarity and CPT invariance is maintained within the resummation approach. An important consequence of this is that the leptogenesis scale may be as low as 1 TeV, even for models with universal Yukawa couplings. We briefly discuss the impact of finite temperature effects and low-energy constraints to the afore-mentioned mechanism of CP violation.

  17. Framing scales and scaling frames

    NARCIS (Netherlands)

    Lieshout, van M.; Dewulf, A.; Aarts, M.N.C.; Termeer, C.J.A.M.

    2009-01-01

    Policy problems are not just out there. Actors highlight different aspects of a situation as problematic and situate the problem on different scales. In this study we will analyse the way actors apply scales in their talk (or texts) to frame the complex decision-making process of the establishment

  18. Mixing Ventilation. Guide on mixing air distribution design

    DEFF Research Database (Denmark)

    Kandzia, Claudia; Kosonen, Risto; Melikov, Arsen Krikor

    In this guidebook most of the known and used in practice methods for achieving mixing air distribution are discussed. Mixing ventilation has been applied to many different spaces providing fresh air and thermal comfort to the occupants. Today, a design engineer can choose from large selection...... of air diffusers and exhaust openings....

  19. Mixing ventilation guide on mixing air distribution design

    CERN Document Server

    Kandzia, Claudia; Kosonen, Risto; Krikor Melikov, Arsen; Nielsen, Peter Vilhelm

    2013-01-01

    In this guidebook most of the known and used in practice methods for achieving mixing air distribution are discussed. Mixing ventilation has been applied to many different spaces providing fresh air and thermal comfort to the occupants. Today, a design engineer can choose from large selection of air diffusers and exhaust openings.

  20. Mixing in polymeric microfluidic devices.

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H. (University of Colorado at Boulder, Boulder, CO); Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

    2006-04-01

    This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the

  1. Scaling of pressurized fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Guralnik, S.; Glicksman, L.R.

    1994-10-01

    The project has two primary objectives. The first is to verify a set of hydrodynamic scaling relationships for commercial pressurized fluidized bed combustors (PFBC). The second objective is to investigate solids mixing in pressurized bubbling fluidized beds. American Electric Power`s (AEP) Tidd combined-cycle demonstration plant will provide time-varying pressure drop data to serve as the basis for the scaling verification. The verification will involve demonstrating that a properly scaled cold model and the Tidd PFBC exhibit hydrodynamically similar behavior. An important issue in PFBC design is the spacing of fuel feed ports. The feed spacing is dictated by the fuel distribution and the mixing characteristics within the bed. After completing the scaling verification, the cold model will be used to study the characteristics of PFBCs. A thermal tracer technique will be utilized to study mixing both near the fuel feed region and in the far field. The results allow the coal feed and distributor to be designed for optimal heating.

  2. Phenomenology of relaxion-Higgs mixing

    Science.gov (United States)

    Flacke, Thomas; Frugiuele, Claudia; Fuchs, Elina; Gupta, Rick S.; Perez, Gilad

    2017-06-01

    We show that the relaxion generically stops its rolling at a point that breaks CP leading to relaxion-Higgs mixing. This opens the door to a variety of observational probes since the possible relaxion mass spans a broad range from sub-eV to the GeV scale. We derive constraints from current experiments (fifth force, astrophysical and cosmological probes, beam dump, flavour, LEP and LHC) and present projections from future experiments such as NA62, SHiP and PIXIE. We find that a large region of the parameter space is already under the experimental scrutiny. All the experimental constraints we derive are equally applicable for general Higgs portal models. In addition, we show that simple multiaxion (clockwork) UV completions suffer from a mild fine tuning problem, which increases with the number of sites. These results favour a cut-off scale lower than the existing theoretical bounds.

  3. Influence of Sub-grid-Scale Isentropic Transports on McRAS Evaluations using ARM-CART SCM Datasets

    Science.gov (United States)

    Sud, Y. C.; Walker, G. K.; Tao, W. K.

    2004-01-01

    In GCM-physics evaluations with the currently available ARM-CART SCM datasets, McRAS produced very similar character of near surface errors of simulated temperature and humidity containing typically warm and moist biases near the surface and cold and dry biases aloft. We argued it must have a common cause presumably rooted in the model physics. Lack of vertical adjustment of horizontal transport was thought to be a plausible source. Clearly, debarring such a freedom would force the incoming air to diffuse into the grid-cell which would naturally bias the surface air to become warm and moist while the upper air becomes cold and dry, a characteristic feature of McRAS biases. Since, the errors were significantly larger in the two winter cases that contain potentially more intense episodes of cold and warm advective transports, it further reaffirmed our argument and provided additional motivation to introduce the corrections. When the horizontal advective transports were suitably modified to allow rising and/or sinking following isentropic pathways of subgrid scale motions, the outcome was to cool and dry (or warm and moisten) the lower (or upper) levels. Ever, crude approximations invoking such a correction reduced the temperature and humidity biases considerably. The tests were performed on all the available ARM-CART SCM cases with consistent outcome. With the isentropic corrections implemented through two different numerical approximations, virtually similar benefits were derived further confirming the robustness of our inferences. These results suggest the need for insentropic advective transport adjustment in a GCM due to subgrid scale motions.

  4. Experimental study on mixing efficiency in water supply rectangular tanks

    Science.gov (United States)

    Bateman, A.; Medina, V.; Mujal, A.

    2009-04-01

    Phenomenon of mixing in drinking water storage tanks and reservoirs has a direct effect on the quality of water. Creation of poor mixing zones and volume stratification can have negative effects in public health. The design of a storage tank must consider the conditions of the inlet and outlets, and also their orientation (vertical or horizontal) to prevent the formation of these zones. Experiments done in a reduced scaled-model with a rectangular base and three different inlets (two waterfalls and a pipe inlet) had the objective to decide which of these inlets achieved the best mixing efficiency. Four situations were considered while three entrances, two unsteady: filling and drawing, and two steady with different outlets. Moreover the effects of columns that support the roof of the tank were studied by running the three entrances with and without columns in the four situations. Neglecting the viscous scale effects, the time taken to mix the volume stored depends on the distance between the inlet and the opposite wall as though as its orientation. Taking into account the whole tank columns have a negative effect on mixing efficiency although they divide the flux and create local zones of turbulence around them, increasing local mixing. Using a digital treating image technique the results are found in a quantitative way.

  5. Mixing in a Microfluid Device

    DEFF Research Database (Denmark)

    Hjorth, Poul G.; Deryabin, Mikhail

    Mixing of fluids in microchannels cannot rely on turbulence since the flow takes place at extremly low Reynolds numbers. Various active and passive devices have been developed to induce mixing in microfluid flow devices. We describe here a model of an active mixer where a transverse periodic flow...

  6. mixed type partial differential equation

    Directory of Open Access Journals (Sweden)

    M. Denche

    2003-01-01

    Full Text Available In this paper, we study a mixed problem with integral boundary conditions for a high order partial differential equation of mixed type. We prove the existence and uniqueness of the solution. The proof is based on energy inequality, and on the density of the range of the operator generated by the considered problem.

  7. Mixed Waste Working Group report

    Energy Technology Data Exchange (ETDEWEB)

    1993-11-09

    The treatment of mixed waste remains one of this country`s most vexing environmental problems. Mixed waste is the combination of radioactive waste and hazardous waste, as defined by the Resource Conservation and Recovery Act (RCRA). The Department of Energy (DOE), as the country`s largest mixed waste generator, responsible for 95 percent of the Nation`s mixed waste volume, is now required to address a strict set of milestones under the Federal Facility Compliance Act of 1992. DOE`s earlier failure to adequately address the storage and treatment issues associated with mixed waste has led to a significant backlog of temporarily stored waste, significant quantities of buried waste, limited permanent disposal options, and inadequate treatment solutions. Between May and November of 1993, the Mixed Waste Working Group brought together stakeholders from around the Nation. Scientists, citizens, entrepreneurs, and bureaucrats convened in a series of forums to chart a course for accelerated testing of innovative mixed waste technologies. For the first time, a wide range of stakeholders were asked to examine new technologies that, if given the chance to be tested and evaluated, offer the prospect for better, safer, cheaper, and faster solutions to the mixed waste problem. In a matter of months, the Working Group has managed to bridge a gap between science and perception, engineer and citizen, and has developed a shared program for testing new technologies.

  8. The Mixed Waste Management Facility. Preliminary design review

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    This document presents information about the Mixed Waste Management Facility. Topics discussed include: cost and schedule baseline for the completion of the project; evaluation of alternative options; transportation of radioactive wastes to the facility; capital risk associated with incineration; radioactive waste processing; scaling of the pilot-scale system; waste streams to be processed; molten salt oxidation; feed preparation; initial operation to demonstrate selected technologies; floorplans; baseline revisions; preliminary design baseline; cost reduction; and project mission and milestones.

  9. Bacteria-induced mixing in natural waters

    Science.gov (United States)

    Sommer, T.; Danza, F.; Berg, J.; Sengupta, A.; Constantinescu, G.; Tokyay, T.; Bürgmann, H.; Dressler, Y.; Sepúlveda Steiner, O.; Schubert, C. J.; Tonolla, M.; Wüest, A.

    2017-09-01

    Swimming organisms can enhance mixing in their natural environments by creating eddies in their wake and by dragging water along. However, these mixing mechanisms are inefficient for microorganisms, because swimming-induced variations in velocity, temperature, and dissolved substances are evened out before they can be advected. In bioconvection, however, microorganisms induce water movement not by propulsion directly but by locally changing the fluid density, which drives convection. Observations of bioconvection have so far mainly been limited to laboratory settings. We report the first observation and quantification of bioconvection within a stratified natural water body. Using in situ measurements, laboratory experiments, and numerical simulations, we demonstrate that the bacterium Chromatium okenii is capable of mixing 0.3 to 1.2 m thick water layers at around 12 m water depth in the Alpine Lake Cadagno (Switzerland). As many species are capable of driving bioconvection, this phenomenon potentially plays a role in species distributions and influences large-scale phenomena like algal blooms.

  10. Incorporating channel geometric uncertainty into a regional scale flood inundation model

    Science.gov (United States)

    Neal, Jeffrey; Odoni, Nick; Trigg, Mark; Freer, Jim; Bates, Paul

    2013-04-01

    Models that simulate the dynamics of river and floodplain water surface elevations over large regions have a wide range of applications including regional scale flood risk estimation and simulating wetland inundation dynamics, while potential emerging applications include estimating river discharge from level observations as part of a data assimilation system. The river routing schemes used by global land surface models are often relatively simple in that they are based on wave speed, kinematic and diffusive physics. However, as the research on large scale river modelling matures, approaches are being developed that resemble scaled-up versions of the hydrodynamic models traditionally applied to rivers at the reach scale. These developments are not surprising given that such models can be significantly more accurate than traditional routing schemes at simulating water surface elevation. This presentation builds on the work of Neal et al. (2012) who adapted a reach scale dynamic flood inundation model for large scale application with the addition of a sub-grid parameterisation for channel flow. The scheme was shown to be numerically stable and scalable, with the aid of some simple test cases, before it was applied to an 800 km reach of the River Niger that includes the complex waterways and lakes of the Niger Inland Delta in Mali. However, the model was significantly less accurate at low to moderate flows than at high flow due, in part, to assuming that the channel geometry was rectangular. Furthermore, this made it difficult to calibrate channel parameters with water levels during typical flow conditions. This presentation will describe an extension of this sub-grid model that allows the channel shape to be defined as an exponent of width, along with a regression based approach to approximate the wetted perimeter length for the new geometry. By treating the geometry in this way uncertainty in the channel shape can be considered as a model parameter, which for the

  11. Surface wind mixing in the Regional Ocean Modeling System (ROMS)

    Science.gov (United States)

    Robertson, Robin; Hartlipp, Paul

    2017-12-01

    Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat, energy, and gases in the upper ocean. Winds are the primary force for surface mixing. To properly simulate upper ocean dynamics and the flux of these quantities within the upper ocean, models must reproduce mixing in the upper ocean. To evaluate the performance of the Regional Ocean Modeling System (ROMS) in replicating the surface mixing, the results of four different vertical mixing parameterizations were compared against observations, using the surface mixed layer depth, the temperature fields, and observed diffusivities for comparisons. The vertical mixing parameterizations investigated were Mellor- Yamada 2.5 level turbulent closure (MY), Large- McWilliams- Doney Kpp (LMD), Nakanishi- Niino (NN), and the generic length scale (GLS) schemes. This was done for one temperate site in deep water in the Eastern Pacific and three shallow water sites in the Baltic Sea. The model reproduced the surface mixed layer depth reasonably well for all sites; however, the temperature fields were reproduced well for the deep site, but not for the shallow Baltic Sea sites. In the Baltic Sea, the models overmixed the water column after a few days. Vertical temperature diffusivities were higher than those observed and did not show the temporal fluctuations present in the observations. The best performance was by NN and MY; however, MY became unstable in two of the shallow simulations with high winds. The performance of GLS nearly as good as NN and MY. LMD had the poorest performance as it generated temperature diffusivities that were too high and induced too much mixing. Further observational comparisons are needed to evaluate the effects of different stratification and wind conditions and the limitations on the vertical mixing parameterizations.

  12. The total energy flux leaving the ocean's mixed layer

    Science.gov (United States)

    Rimac, Antonija; von Storch, Jin-Song; Eden, Carsten

    2017-04-01

    Interior density mixing contributes to drive the large-scale ocean circulation. The energy needed for this mixing is believed to be supplied predominantly by the tidal and wind forcing. In this study, we focus on the wind-power input to three different types of motions, that is, near-inertial waves, sub-inertial fluctuations, and time-mean flows. Surface winds can generate near-inertial waves which propagate freely into the ocean's interior and after escaping the mixed layer contribute to interior mixing. Winds also input power into the ocean to maintain the time-mean circulation and to generate sub-inertial fluctuations, either by the vertical or horizontal shear instability of the large-scale flows, or directly via wind induced fluctuations at the ocean surface. The energy of both the sub-inertial fluctuations and the time-mean flow will be eventually dissipated (or transferred to the internal gravity wave field or small scale turbulence). However, the exact portion of the power that escapes the turbulent mixed layer and that can potentially affect the interior mixing, is still unknown. The total energy flux leaving the ocean's spatially and seasonally varying mixed layer is estimated using a global 1/10° ocean general circulation model. From the total wind-power input of 3.33 TW into near-inertial waves (0.35 TW) sub-inertial fluctuations (0.87 TW), and the time-mean circulation (2.11 TW), 0.92 TW leave the mixed layer; with 0.04 TW (11.4%) due to near-inertial motions, 0.07 TW (8.3%) due to sub-inertial fluctuations, and 0.81 TW (38.4%) due to time-mean motions. Of the 0.81 TW from the time-mean motions, 0.5 TW result from the projection of the horizontal flux onto the sloped bottom of the mixed layer. This projection is negligible for the transient fluxes. The spatial structure of the vertical flux is determined principally by the wind stress curl. The mean and sub-inertial fluxes leaving the mixed layer are approximately 40-50% smaller than the respective

  13. Fluctuations of a passive scalar in a turbulent mixing layer

    KAUST Repository

    Attili, Antonio

    2013-09-19

    The turbulent flow originating downstream of the Kelvin-Helmholtz instability in a mixing layer has great relevance in many applications, ranging from atmospheric physics to combustion in technical devices. The mixing of a substance by the turbulent velocity field is usually involved. In this paper, a detailed statistical analysis of fluctuations of a passive scalar in the fully developed region of a turbulent mixing layer from a direct numerical simulation is presented. Passive scalar spectra show inertial ranges characterized by scaling exponents −4/3 and −3/2 in the streamwise and spanwise directions, in agreement with a recent theoretical analysis of passive scalar scaling in shear flows [Celani et al., J. Fluid Mech. 523, 99 (2005)]. Scaling exponents of high-order structure functions in the streamwise direction show saturation of intermittency with an asymptotic exponent ζ∞=0.4 at large orders. Saturation of intermittency is confirmed by the self-similarity of the tails of the probability density functions of the scalar increments at different scales r with the scaling factor r−ζ∞ and by the analysis of the cumulative probability of large fluctuations. Conversely, intermittency saturation is not observed for the spanwise increments and the relative scaling exponents agree with recent results for homogeneous isotropic turbulence with mean scalar gradient. Probability density functions of the scalar increments in the three directions are compared to assess anisotropy.

  14. Scaling down

    Directory of Open Access Journals (Sweden)

    Ronald L Breiger

    2015-11-01

    Full Text Available While “scaling up” is a lively topic in network science and Big Data analysis today, my purpose in this essay is to articulate an alternative problem, that of “scaling down,” which I believe will also require increased attention in coming years. “Scaling down” is the problem of how macro-level features of Big Data affect, shape, and evoke lower-level features and processes. I identify four aspects of this problem: the extent to which findings from studies of Facebook and other Big-Data platforms apply to human behavior at the scale of church suppers and department politics where we spend much of our lives; the extent to which the mathematics of scaling might be consistent with behavioral principles, moving beyond a “universal” theory of networks to the study of variation within and between networks; and how a large social field, including its history and culture, shapes the typical representations, interactions, and strategies at local levels in a text or social network.

  15. Pengaruh Sikap Konsumen terhadap Marketing Mix Hospitality

    Directory of Open Access Journals (Sweden)

    Kusuma Chandra Kirana

    2016-06-01

    Full Text Available Abstract Yogyakarta has been known as the city of tourism for the many culture and heritage in this region. The city of Heritage attached to it, has an impact on people’s behavior in the consumption of products or services. A demand for good tourism on the products service has encouraged the growth of industries that promote values. Hospitality, an industry engaged in social services, is growing rapidly in Yogyakarta. The industry deals with hospitality services and management of socio-religious events, such as weddings. Based on the data obtained, people of Yogyakarta are very sensitive to the appropriate product warranties. This study used descriptive statistics of Likert shari’i scale, a modified Likert scale. Data were analyzed using Fishbein formulation. The results of the above studies indicate that the overall consumers’ attitude towards hospitality marketing mix in Yogyakarta is positive with the value of Ao: + 5.1601. On the other hand, the score of partial assessments of hospitality marketing mix in Yogyakarta are as follows; product assessment Ao = +1.047025, price Ao =0.58305, location Ao = +0.980075, promotion Ao = +0.3479.

  16. Perfect mixing of immiscible macromolecules at fluid interfaces

    Science.gov (United States)

    Sheiko, Sergei; Matyjaszewski, Krzysztof; Tsukruk, Vladimir; Carrillo, Jan-Michael; Rubinstein, Michael; Dobrynin, Andrey; Zhou, Jing

    2014-03-01

    Macromolecules typically phase separate unless their shapes and chemical compositions are tailored to explicitly drive mixing. But now our research has shown that physical constraints can drive spontaneous mixing of chemically different species. We have obtained long-range 2D arrays of perfectly mixed macromolecules having a variety of molecular architectures and chemistries, including linear chains, block-copolymer stars, and bottlebrush copolymers with hydrophobic, hydrophilic, and lipophobic chemical compositions. This is achieved by entropy-driven enhancement of steric repulsion between macromolecules anchored on a substrate. By monitoring the kinetics of mixing, we have proved that molecular intercalation is an equilibrium state. The array spacing is controlled by the length of the brush side chains. This entropic templating strategy opens new ways for generating patterns on sub-100 nm length scales with potential application in lithography, directed self-assembly, and biomedical assays. Financial support from the National Science Foundation DMR-0906985, DMR-1004576, DMR-1122483, and DMR-0907515.

  17. Nomogram for the height of the daytime mixed layer

    Energy Technology Data Exchange (ETDEWEB)

    Nyren, K. [Ericsson EriSoft AB, Umeaa (Sweden); Gryning, S.E. [Risoe National Lab., Roskilde (Denmark)

    1997-10-01

    We present a nomogram that provide information about the general behaviour of the mixed layer at a given location. The nomogram is meant to be a practical and easy to use tool to determine the height of the mixed layer for i.e. weather forecaster, air pollution studies and planning of meteorological experiments. Use of the nomogram is restricted to flat, relatively homogeneous terrain. Inhomogeneous terrain with patch scales of 10 km or more might create organised circulation like i.e. lake breezes. The data represented in the nomogram is computed using a meteorological preprocessor and climatological temperature data for the location. The nomogram is simplified but retain main physical processes that control the evolution of the mixed layer and can be easily constructed for any chosen location on land. Nomogram of the mixed layer behavior at the location of Cabauw, the Netherlands is shown and discussed. (au)

  18. Mixing Ventilation System in a Single-Aisle Aircraft Cabin

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm; Zhang, Chen; Wojcik, Kamil

    2014-01-01

    Traditionally, air is supplied to the aircraft cabin either by individual nozzles or by supply slots. The air is expected to be fully mixed in the cabin, and the system is considered to be a mixing ventilation system. This paper will provide measurements on the mixing flow in an aircraft cabin...... and present a design procedure of the system. Finally, a personalised ventilation system will be described, which can be used together with the mixing ventilation system. The experiments are made in a full-scale, left side mock-up of a single-aisle (Boeing 737) cabin with four seats. The four passengers...... are simulated by thermal manikins. Velocity, temperature and cross-infection risk are measured. The experiments proved that fully developed turbulent flow will take place in the cabin and that the flow element theory can be used for the design procedure when the air flow rate is above a certain level...

  19. Modeling of fuel mixing in fluidized bed combustors

    Energy Technology Data Exchange (ETDEWEB)

    David Pallares; Filip Johnsson [Chalmers University of Technology, Goeteborg (Sweden). Department of Energy and Environment

    2008-12-15

    This paper presents a three-dimensional model for fuel mixing in fluidized bed combustors. The model accounts for mixing patterns which were experimentally shown to govern mixing in risers with geometry and operational conditions representative for furnaces in fluidized bed combustors. The mixing process is modeled for three different solid phases in the furnace and the model, which includes the return leg, can be applied both under bubbling and circulating regimes. The semi-empirical basis of the model was previously validated in different large-scale fluidized bed combustors and is combined with a model for fuel particle conversion to obtain the fuel concentration field. Model results are compared with experimental data from the Chalmers 12 MW{sub th} CFB combustor, yielding a reasonable agreement.

  20. Confidence Intervals for Assessing Heterogeneity in Generalized Linear Mixed Models

    Science.gov (United States)

    Wagler, Amy E.

    2014-01-01

    Generalized linear mixed models are frequently applied to data with clustered categorical outcomes. The effect of clustering on the response is often difficult to practically assess partly because it is reported on a scale on which comparisons with regression parameters are difficult to make. This article proposes confidence intervals for…

  1. Scaling Rules!

    Science.gov (United States)

    Malkinson, Dan; Wittenberg, Lea

    2015-04-01

    Scaling is a fundamental issue in any spatially or temporally hierarchical system. Defining domains and identifying the boundaries of the hierarchical levels may be a challenging task. Hierarchical systems may be broadly classified to two categories: compartmental and continuous ones. Examples of compartmental systems include: governments, companies, computerized networks, biological taxonomy and others. In such systems the compartments, and hence the various levels and their constituents are easily delineated. In contrast, in continuous systems, such as geomorphological, ecological or climatological ones, detecting the boundaries of the various levels may be difficult. We propose that in continuous hierarchical systems a transition from one functional scale to another is associated with increased system variance. Crossing from a domain of one scale to the domain of another is associated with a transition or substitution of the dominant drivers operating in the system. Accordingly we suggest that crossing this boundary is characterized by increased variance, or a "variance leap", which stabilizes, until crossing to the next domain or hierarchy level. To assess this we compiled sediment yield data from studies conducted at various spatial scales and from different environments. The studies were partitioned to ones conducted in undisturbed environments, and those conducted in disturbed environments, specifically by wildfires. The studies were conducted in plots as small as 1 m2, and watersheds larger than 555000 ha. Regressing sediment yield against plot size, and incrementally calculating the variance in the systems, enabled us to detect domains where variance values were exceedingly high. We propose that at these domains scale-crossing occurs, and the systems transition from one hierarchical level to another. Moreover, the degree of the "variance leaps" characterizes the degree of connectivity among the scales.

  2. Analytical Solution for Reactive Solute Transport Considering Incomplete Mixing

    Science.gov (United States)

    Bellin, A.; Chiogna, G.

    2013-12-01

    The laboratory experiments of Gramling et al. (2002) showed that incomplete mixing at the pore scale exerts a significant impact on transport of reactive solutes and that assuming complete mixing leads to overestimation of product concentration in bimolecular reactions. We consider here the family of equilibrium reactions for which the concentration of the reactants and the product can be expressed as a function of the mixing ratio, the concentration of a fictitious non reactive solute. For this type of reactions we propose, in agreement with previous studies, to model the effect of incomplete mixing at scales smaller than the Darcy scale assuming that the mixing ratio is distributed within an REV according to a Beta distribution. We compute the parameters of the Beta model by imposing that the mean concentration is equal to the value that the concentration assumes at the continuum Darcy scale, while the variance decays with time as a power law. We show that our model reproduces the concentration profiles of the reaction product measured in the Gramling et al. (2002) experiments using the transport parameters obtained from conservative experiments and an instantaneous reaction kinetic. The results are obtained applying analytical solutions both for conservative and for reactive solute transport, thereby providing a method to handle the effect of incomplete mixing on multispecies reactive solute transport, which is simpler than other previously developed methods. Gramling, C. M., C. F. Harvey, and L. C. Meigs (2002), Reactive transport in porous media: A comparison of model prediction with laboratory visualization, Environ. Sci. Technol., 36(11), 2508-2514.

  3. Mixed features in bipolar disorder.

    Science.gov (United States)

    Solé, Eva; Garriga, Marina; Valentí, Marc; Vieta, Eduard

    2017-04-01

    Mixed affective states, defined as the coexistence of depressive and manic symptoms, are complex presentations of manic-depressive illness that represent a challenge for clinicians at the levels of diagnosis, classification, and pharmacological treatment. The evidence shows that patients with bipolar disorder who have manic/hypomanic or depressive episodes with mixed features tend to have a more severe form of bipolar disorder along with a worse course of illness and higher rates of comorbid conditions than those with non-mixed presentations. In the updated Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5), the definition of "mixed episode" has been removed, and subthreshold nonoverlapping symptoms of the opposite pole are captured using a "with mixed features" specifier applied to manic, hypomanic, and major depressive episodes. However, the list of symptoms proposed in the DSM-5 specifier has been widely criticized, because it includes typical manic symptoms (such as elevated mood and grandiosity) that are rare among patients with mixed depression, while excluding symptoms (such as irritability, psychomotor agitation, and distractibility) that are frequently reported in these patients. With the new classification, mixed depressive episodes are three times more common in bipolar II compared with unipolar depression, which partly contributes to the increased risk of suicide observed in bipolar depression compared to unipolar depression. Therefore, a specific diagnostic category would imply an increased diagnostic sensitivity, would help to foster early identification of symptoms and ensure specific treatment, as well as play a role in suicide prevention in this population.

  4. A LES Study on Passive Mixing in Supersonic Shear Layer Flows Considering Effects of Baffle Configuration

    Directory of Open Access Journals (Sweden)

    Ren Zhao-Xin

    2014-01-01

    Full Text Available Under the background of dual combustor ramjet (DCR, a numerical investigation of supersonic mixing layer was launched, focused on the mixing enhancement method of applying baffles with different geometric configurations. Large eddy simulation with high order schemes, containing a fifth-order hybrid WENO compact scheme for the convective flux and sixth-order compact one for the viscous flux, was utilized to numerically study the development of the supersonic mixing layer. The supersonic cavity flow was simulated and the cavity configuration could influence the mixing characteristics, since the impingement process of large scale structures formed inside the cavity could raise the vorticity and promote the mixing. The effect of baffle's configurations on the mixing process was analyzed by comparing the flow properties, mixing efficiency, and total pressure loss. The baffle could induce large scale vortexes, promote the mixing layer to lose its stability easily, and then lead to the mixing efficiency enhancement. However, the baffle could increase the total pressure loss. The present investigation could provide guidance for applying new passive mixing enhancement methods for the supersonic mixing.

  5. Generalized, Linear, and Mixed Models

    CERN Document Server

    McCulloch, Charles E; Neuhaus, John M

    2011-01-01

    An accessible and self-contained introduction to statistical models-now in a modernized new editionGeneralized, Linear, and Mixed Models, Second Edition provides an up-to-date treatment of the essential techniques for developing and applying a wide variety of statistical models. The book presents thorough and unified coverage of the theory behind generalized, linear, and mixed models and highlights their similarities and differences in various construction, application, and computational aspects.A clear introduction to the basic ideas of fixed effects models, random effects models, and mixed m

  6. Equations of the mixed type

    CERN Document Server

    Bitsadze, A V

    1963-01-01

    Equations of the Mixed Type compiles a series of lectures on certain fundamental questions in the theory of equations of mixed type. This book investigates the series of problems concerning linear partial differential equations of the second order in two variables, and possessing the property that the type of the equation changes either on the boundary of or inside the considered domain. Topics covered include general remarks on linear partial differential equations of mixed type; study of the solutions of second order hyperbolic equations with initial conditions given along the lines of parab

  7. [Marketing mix in health service].

    Science.gov (United States)

    Ameri, Cinzia; Fiorini, Fulvio

    2015-01-01

    The marketing mix is the combination of the marketing variables that a firm employs with the purpose to achieve the expected volume of business within its market. In the sale of goods, four variables compose the marketing mix (4 Ps): Product, Price, Point of sale and Promotion. In the case of providing services, three further elements play a role: Personnel, Physical Evidence and Processes (7 Ps). The marketing mix must be addressed to the consumers as well as to the employees of the providing firm. Furthermore, it must be interpreted as employees ability to satisfy customers (interactive marketing).

  8. Two-fluid sub-grid-scale viscosity in nonlinear simulation of ballooning modes in a heliotron device

    Science.gov (United States)

    Miura, H.; Hamba, F.; Ito, A.

    2017-07-01

    A large eddy simulation (LES) approach is introduced to enable the study of the nonlinear growth of ballooning modes in a heliotron-type device, by solving fully 3D two-fluid magnetohydrodynamic (MHD) equations numerically over a wide range of parameter space, keeping computational costs as low as possible. A model to substitute the influence of scales smaller than the grid size, at sub-grid scale (SGS), and at the scales larger than it—grid scale (GS)—has been developed for LES. The LESs of two-fluid MHD equations with SGS models have successfully reproduced the growth of the ballooning modes in the GS and nonlinear saturation. The numerical results show the importance of SGS effects on the GS components, or the effects of turbulent fluctuation at small scales in low-wavenumber unstable modes, over the course of the nonlinear saturation process. The results also show the usefulness of the LES approach in studying instability in a heliotron device. It is shown through a parameter survey over many SGS model coefficients that turbulent small-scale components in experiments can contribute to keeping the plasma core pressure from totally collapsing.

  9. Discriminative Mixed-Membership Models

    Data.gov (United States)

    National Aeronautics and Space Administration — Although mixed-membership models have achieved great success in unsupervised learning, they have not been widely applied to classification problems. In this paper,...

  10. Mixed-mu superconducting bearings

    Science.gov (United States)

    Hull, John R.; Mulcahy, Thomas M.

    1998-01-01

    A mixed-mu superconducting bearing including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure.

  11. Mixed methods research for TESOL

    CERN Document Server

    Brown, James; Farr, Fiona

    2014-01-01

    Defining and discussing the relevance of theoretical and practical issues involved in mixed methods research. Covering the basics of research methodology, this textbook shows you how to choose and combine quantitative and qualitative research methods to b

  12. Estimates of tidal mixing in the Indonesian archipelago from multidisciplinary INDOMIX in-situ data

    OpenAIRE

    Koch Larrouy, Ariane; Atmadipoera, A.; Beek, P. van; Madec, G.; Aucan, Jerôme; Lyard, F.; Grelet, Jacques; Souhaut, M.

    2015-01-01

    The Indonesian Mixing program (INDOMIX) was designed to quantify the very strong mixing that transforms Pacific waters into isohaline Indonesian Waters in the Indonesian archipelago. The turbulent dissipation rates and associated mixing were estimated and analyzed using a multidisciplinary approach that combines physical and geochemical in-situ observations: (1) direct measurements of the dissipation using a microstructure profiler, (2) use of density-based fine-scale methods applied to CTD a...

  13. Promocja a marketing-mix

    OpenAIRE

    Cyrson, Edward F.

    1994-01-01

    Many companies have often forgotten that promotion is an element of marketing-mix. Therelore their promotional campain has not always been as effective as it could be. In designing and developing marketing communication one should consider all elements of marketing-mix as well as all promotional tools. They together create a promotional system in which all the elements are Mutually reinforcing and give the system the most efficient and effective power. The major thrust of promo...

  14. Markets: Ready-Mixed Concrete

    OpenAIRE

    Chad Syverson

    2008-01-01

    Concrete's natural color is gray. Its favored uses are utilitarian. Its very ubiquity causes it to blend into the background. But ready-mix concrete does have one remarkable characteristic: other than manufactured ice, perhaps no other manufacturing industry faces greater transport barriers. The transportation problem arises because ready-mix concrete both has a low value-to-weight ratio and is highly perishable -- it absolutely must be discharged from the truck before it hardens. These trans...

  15. Nuclear scales

    Energy Technology Data Exchange (ETDEWEB)

    Friar, J.L.

    1998-12-01

    Nuclear scales are discussed from the nuclear physics viewpoint. The conventional nuclear potential is characterized as a black box that interpolates nucleon-nucleon (NN) data, while being constrained by the best possible theoretical input. The latter consists of the longer-range parts of the NN force (e.g., OPEP, TPEP, the {pi}-{gamma} force), which can be calculated using chiral perturbation theory and gauged using modern phase-shift analyses. The shorter-range parts of the force are effectively parameterized by moments of the interaction that are independent of the details of the force model, in analogy to chiral perturbation theory. Results of GFMC calculations in light nuclei are interpreted in terms of fundamental scales, which are in good agreement with expectations from chiral effective field theories. Problems with spin-orbit-type observables are noted.

  16. Stochastic Theory of Turbulence Mixing by Finite Eddies in the Turbulent Boundary Layer

    NARCIS (Netherlands)

    Dekker, H.; Leeuw, G. de; Maassen van den Brink, A.

    1995-01-01

    Turbulence mixing is treated by means of a novel formulation of nonlocal K-theory, involving sample paths and a stochastic hypothesis. The theory simplifies for mixing by exchange (strong-eddies) and is then applied to the boundary layer (involving scaling). This maps boundary layer turbulence onto

  17. Pile mixing increases greenhouse gas emissions during composting of dairy manure

    Science.gov (United States)

    The effect of pile mixing on greenhouse gas (GHG) emissions from stored dairy manure was determined using large flux chambers designed to completely cover pilot-scale manure piles. GHG emissions from piles that were mixed four times during the 80 day trial were about 20% higher than unmixed piles. ...

  18. Computing assortative mixing by degree with the s-metric in networks using linear programming

    NARCIS (Netherlands)

    Waldorp, L.J.; Schmittmann, V.D.

    2015-01-01

    Calculation of assortative mixing by degree in networks indicates whether nodes with similar degree are connected to each other. In networks with scale-free distribution high values of assortative mixing by degree can be an indication of a hub-like core in networks. Degree correlation has generally

  19. Greenhouse gas emissions during composting of dairy manure: Delaying pile mixing does not reduce overall emissions

    Science.gov (United States)

    The effect of the timing of pile mixing on greenhouse gas (GHG) emissions during dairy manure composting was determined using large flux chambers designed to completely cover replicate pilot-scale compost piles. GHG emissions from compost piles that were mixed at 2, 3, 4, or 5 weeks after initial c...

  20. Surface water iron supplies in the Southern Ocean sustained by deep winter mixing

    CSIR Research Space (South Africa)

    Tagliabue, A

    2014-04-01

    Full Text Available Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surfacewaters from subsurface reservoir