WorldWideScience

Sample records for hydrodynamic dispersion parameters

  1. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  2. Hydrodynamic modeling of juvenile mussel dispersal in a large river: The potential effects of bed shear stress and other parameters

    Science.gov (United States)

    Daraio, J.A.; Weber, L.J.; Newton, T.J.

    2010-01-01

    Because unionid mussels have a parasitic larval stage, they are able to disperse upstream and downstream as larvae while attached to their host fish and with flow as juveniles after excystment from the host. Understanding unionid population ecology requires knowledge of the processes that affect juvenile dispersal prior to establishment. We examined presettlement (transport and dispersion with flow) and early postsettlement (bed shear stress) hydraulic processes as negative censoring mechanisms. Our approach was to model dispersal using particle tracking through a 3-dimensional flow field output from hydrodynamic models of a reach of the Upper Mississippi River. We tested the potential effects of bed shear stress (??b) at 5 flow rates on juvenile mussel dispersal and quantified the magnitude of these effects as a function of flow rate. We explored the reach-scale relationships of Froude number (Fr), water depth (H), local bed slope (S), and unit stream power (QS) with the likelihood of juvenile settling (??). We ran multiple dispersal simulations at each flow rate to estimate ??, the parameter of a Poisson distribution, from the number of juveniles settling in each grid cell, and calculated dispersal distances. Virtual juveniles that settled in areas of the river where b > critical shear stress (c) were resuspended in the flow and transported further downstream, so we ran simulations at 3 different conditions for ??c (??c = ??? no resuspension, 0.1, and 0.05 N/m2). Differences in virtual juvenile dispersal distance were significantly dependent upon c and flow rate, and effects of b on settling distribution were dependent upon c. Most simulations resulted in positive correlations between ?? and ??b, results suggesting that during early postsettlement, ??b might be the primary determinant of juvenile settling distribution. Negative correlations between ?? and ??b occurred in some simulations, a result suggesting that physical or biological presettlement processes

  3. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  4. Hydrodynamic dispersion broadening of a sedimentation front

    Science.gov (United States)

    Martin, J.; Rakotomalala, N.; Salin, D.

    1994-10-01

    Hydrodynamic dispersion is responsible for the spreading of the sedimentation front even in a noncolloidal monodisperse suspension. Measurements of the broadening of the top front observed during sedimentation have been used in determining the hydrodynamic dispersion coefficient. Hindered settling has an opposed effect and leads to the self-sharpening of the front. Both effects have to be taken into account simultaneously. This Letter provides a simple, but complete determination of the space and time concentration profile and shows that the final front should consist of a steady-shape profile propagating at constant velocity. With such a solution, the data of Davis et al. [AIChE J. 34, 123 (1988); J. Fluid Mech. 196, 107 (1988)] give hydrodynamic dispersion coefficient five times larger than their former analysis, in agreement with Lee et al. [Phys. Fluids A 4, 2601 (1992)].

  5. Frictionless dispersive hydrodynamics of Stokes flows

    CERN Document Server

    Maiden, Michelle D; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-01-01

    Effectively frictionless, dispersive flow characterizes superfluids, nonlinear optical diffraction, and geophysical fluid interfaces. Dispersive shock waves (DSWs) and solitons are fundamental nonlinear excitations in these media, but DSW studies to date have been severely constrained by a loss of coherence. Here we report on a novel dispersive hydrodynamics testbed: the effectively frictionless flow of interfacial waves between two high contrast, low Reynolds' number Stokes fluids. This system enables high fidelity observations of large amplitude DSWs, found to agree quantitatively with a nonlinear wave averaging theory. We then report on observations of highly coherent phenomena including DSW backflow, the refraction or absorption of solitons by DSWs, and multi-phase DSW-DSW merger. The complex, coherent, nonlinear mixing of DSWs and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  6. Intrinsic ambiguity in second order viscosity parameters in relativistic hydrodynamics

    CERN Document Server

    Nakayama, Yu

    2012-01-01

    We show that relativistic hydrodynamics in Minkowski space-time has intrinsic ambiguity in second order viscosity parameters in the Landau-Lifshitz frame. This stems from the possibility of improvements of energy-momentum tensor. There exist at least two viscosity parameters which can be removed by using this ambiguity in scale invariant hydrodynamics in (1+3) dimension, and seemingly non-conformal hydrodynamic theories can be hiddenly conformal invariant.

  7. Gamma neutron method applied to field measurement of hydrodynamic dispersion

    Science.gov (United States)

    Brissaud, F.; Pappalardo, A.; Couchat, Ph.

    1983-06-01

    The gamma neutron method is applied to the study of solute movements during field irrigations under steady-state and transient hydrodynamic conditions. Two different types of behavior are discussed. In the first, the labeled water pulse velocity matches the conservation of the vertical rate of water and, when the deuterated water concentration profiles are mass-conservative, the experimental results are accurately described by the equation of dispersion. In the second, the pore water velocity differs considerably from that of strictly vertical displacements and the concentration profiles are not massconservative.

  8. Dispersive deformations of hydrodynamic reductions of (2 + 1)D dispersionless integrable systems

    Science.gov (United States)

    Ferapontov, E. V.; Moro, A.

    2009-01-01

    We demonstrate that hydrodynamic reductions of dispersionless integrable systems in 2 + 1 dimensions, such as the dispersionless Kadomtsev-Petviashvili (dKP) and dispersionless Toda lattice (dTl) equations, can be deformed into reductions of the corresponding dispersive counterparts. Modulo the Miura group, such deformations are unique. The requirement that any hydrodynamic reduction possesses a deformation of this kind imposes strong constraints on the structure of dispersive terms, suggesting an alternative approach to the integrability in 2 + 1 dimensions.

  9. Retrieval of vegetation hydrodynamic parameters from satellite multispectral data

    Science.gov (United States)

    Forzieri, Giovanni; Degetto, Massimo; Righetti, Maurizio; Castelli, Fabio; Preti, Federico

    2013-04-01

    Riparian vegetation plays a crucial role on affecting the floodplain hydraulic roughness, which in turn significantly influences the dynamics of flood waves. This work explores the potential accuracies of retrieving vegetation hydrodynamic parameters through satellite multispectral data. The method is focused on estimation of vegetation height and flexural rigidity for herbaceous patterns and of plant density, tree height, stem diameter, crown base height and crown diameter of high-forest and coppice consociations for arboreal and shrub patterns. The retrieval algorithm performs: (1) classification procedure of riparian corridor; (2) land cover-based Principal Component Analysis of spectral channels; (3) explorative analysis of correlation structure between principal components and biomechanical properties and (4) model identification/estimation/validation for floodplain roughness parameterization. To capture the impacts of stiff/flexible vegetation, a GIS hydrodynamic model has been coupled with a flow resistance external routine that estimates the hydraulic roughness by using simulated water stages and the remote sensing-derived vegetation parameters. The procedure is tested along a 3-km reach of the Avisio river (Trentino Alto Adige, Italy) by comparing extended field surveys and a synchronous SPOT-5 multispectral image acquired on 28/08/2004. Results showed significant correlation values between spectral-derived information and hydrodynamic parameters. Predictive models provided high coefficients of determination, especially for mixed arboreal and shrub land covers. The generated structural parameter maps represent spatially explicit data layers that can be used as inputs to hydrodynamic models to analyze flow resistance effects in different submergence conditions of vegetation. The hydraulic modelling results showed that the new method is able to provide accurate hydraulic output data and to enhance the roughness estimation up to 73% with respect to a

  10. TSUNAMI DISPERSION SENSITIVITY TO SEISMIC SOURCE PARAMETERS

    Directory of Open Access Journals (Sweden)

    Oleg Igorevich Gusev

    2016-05-01

    Full Text Available The study focuses on the sensitivity of frequency dispersion effects to the form of initial surface elevation of seismic tsunami source. We vary such parameters of the source as rupture depth, dip-angle and rake-angle. Some variations in magnitude and strike angle are considered. The fully nonlinear dispersive model on a rotating sphere is used for wave propagation simulations. The main feature of the algorithm is the splitting of initial system on two subproblems of elliptic and hyperbolic type, which allows implementation of well-suitable numerical methods for them. The dispersive effects are estimated through differences between computations with the dispersive and nondispersive models. We consider an idealized test with a constant depth, a model basin for near-field tsunami simulations and a realistic scenario. Our computations show that the dispersion effects are strongly sensitive to the rupture depth and the dip-angle variations. Waves generated by sources with lager magnitude may be even more affected by dispersion.

  11. Hydrodynamic parameters of mesh fillers relevant to miniature regenerative cryocoolers

    Science.gov (United States)

    Landrum, E. C.; Conrad, T. J.; Ghiaasiaan, S. M.; Kirkconnell, Carl S.

    2010-06-01

    Directional hydrodynamic parameters of two fine-mesh porous materials that are suitable for miniature regenerative cryocoolers were studied under steady and oscillating flows of helium. These materials included stacked discs of #635 stainless steel (wire diameter of 20.3 μm) and #325 phosphor bronze (wire diameter of 35.6 μm) wire mesh screens, which are among the commercially available fillers for use in small-scale regenerators and heat exchangers, respectively. Experiments were performed in test sections in which pressure variations across these fillers, in the axial and lateral (radial) directions, were measured under steady and oscillatory flows. The directional permeability and Forchheimer's inertial coefficient were then obtained by using a Computational Fluid Dynamics (CFD)-assisted method. The oscillatory flow experiments covered a frequency range of 50-200 Hz. The results confirmed the importance of anisotropy in the mesh screen fillers, and indicated differences between the directional hydrodynamic resistance parameters for steady and oscillating flow regimes.

  12. Radiation Hydrodynamic Parameter Study of Inertial Fusion Energy Reactor Chambers

    Science.gov (United States)

    Sacks, Ryan; Moses, Gregory

    2014-10-01

    Inertial fusion energy reactors present great promise for the future as they are capable of providing baseline power with no carbon footprint. Simulation work regarding the chamber response and first wall insult is performed with the 1-D radiation hydrodynamics code BUCKY. Simulation with differing chamber parameters are implemented to study the effect of gas fill, gas mixtures and chamber radii. Xenon and argon gases are of particular interest as shielding for the first wall due to their high opacity values and ready availability. Mixing of the two gases is an attempt to engineer a gas cocktail to provide the maximum amount of shielding with the least amount of cost. A parameter study of different chamber radii shows a consistent relationship with that of first wall temperature (~1/r2) and overpressure (~1/r3). This work is performed under collaboration with Lawrence Livermore National Laboratory.

  13. DISSIPATION AND DISPERSION APPROXIMATION TO HYDRODYNAMICAL EQUATIONS AND ASYMPTOTIC LIMIT

    Institute of Scientific and Technical Information of China (English)

    Hsiao Ling; Li Hailiang

    2008-01-01

    The compressible Euler equations with dissipation and/or dispersion correction are widely used in the area of applied sciences, for instance, plasma physics,charge transport in semiconductor devices, astrophysics, geophysics, etc. We consider the compressible Euler equation with density-dependent (degenerate) viscosities and capillarity, and investigate the global existence of weak solutions and asymptotic limit.

  14. Influence of nonlinearity of the phonon dispersion relation on wave velocities in the four-moment maximum entropy phonon hydrodynamics

    Science.gov (United States)

    Larecki, Wieslaw; Banach, Zbigniew

    2014-01-01

    This paper analyzes the propagation of the waves of weak discontinuity in a phonon gas described by the four-moment maximum entropy phonon hydrodynamics involving a nonlinear isotropic phonon dispersion relation. For the considered hyperbolic equations of phonon gas hydrodynamics, the eigenvalue problem is analyzed and the condition of genuine nonlinearity is discussed. The speed of the wave front propagating into the region in thermal equilibrium is first determined in terms of the integral formula dependent on the phonon dispersion relation and subsequently explicitly calculated for the Dubey dispersion-relation model: |k|=ωc-1(1+bω2). The specification of the parameters c and b for sodium fluoride (NaF) and semimetallic bismuth (Bi) then makes it possible to compare the calculated dependence of the wave-front speed on the sample’s temperature with the empirical relations of Coleman and Newman (1988) describing for NaF and Bi the variation of the second-sound speed with temperature. It is demonstrated that the calculated temperature dependence of the wave-front speed resembles the empirical relation and that the parameters c and b obtained from fitting respectively the empirical relation and the original material parameters of Dubey (1973) are of the same order of magnitude, the difference being in the values of the numerical factors. It is also shown that the calculated temperature dependence is in good agreement with the predictions of Hardy and Jaswal’s theory (Hardy and Jaswal, 1971) on second-sound propagation. This suggests that the nonlinearity of a phonon dispersion relation should be taken into account in the theories aiming at the description of the wave-type phonon heat transport and that the Dubey nonlinear isotropic dispersion-relation model can be very useful for this purpose.

  15. Hydrodynamic dispersion effect on natural convection in porous surfaces by double diffusion; Efeito da dispersao hidrodinamica na conveccao natural por difusao dupla em meios porosos

    Energy Technology Data Exchange (ETDEWEB)

    Telles, Rubens S.

    1990-12-31

    This work discusses the problem of hydrodynamic dispersion on natural convection in porous medium near impermeable surfaces. The study considers the convection caused by density variation due to temperature and concentration gradients combination. The parametrization of the phenomenon is obtained through scale analysis. It is also presented four possible situations according to the intensity of dispersion term. In search of similarity solutions the similarity variables and parameters associated to dispersion are found through scale analysis. The Runge-Kutta algorithm and the `shooting` method are used to solve the equations resulting from the similarity transformations. Several cases are solved covering an extensive range of the governing parameters. 22 refs., 43 figs., 13 tabs.

  16. Can we calibrate simultaneously groundwater recharge and aquifer hydrodynamic parameters ?

    Science.gov (United States)

    Hassane Maina, Fadji; Ackerer, Philippe; Bildstein, Olivier

    2017-04-01

    By groundwater model calibration, we consider here fitting the measured piezometric heads by estimating the hydrodynamic parameters (storage term and hydraulic conductivity) and the recharge. It is traditionally recommended to avoid simultaneous calibration of groundwater recharge and flow parameters because of correlation between recharge and the flow parameters. From a physical point of view, little recharge associated with low hydraulic conductivity can provide very similar piezometric changes than higher recharge and higher hydraulic conductivity. If this correlation is true under steady state conditions, we assume that this correlation is much weaker under transient conditions because recharge varies in time and the parameters do not. Moreover, the recharge is negligible during summer time for many climatic conditions due to reduced precipitation, increased evaporation and transpiration by vegetation cover. We analyze our hypothesis through global sensitivity analysis (GSA) in conjunction with the polynomial chaos expansion (PCE) methodology. We perform GSA by calculating the Sobol indices, which provide a variance-based 'measure' of the effects of uncertain parameters (storage and hydraulic conductivity) and recharge on the piezometric heads computed by the flow model. The choice of PCE has the following two benefits: (i) it provides the global sensitivity indices in a straightforward manner, and (ii) PCE can serve as a surrogate model for the calibration of parameters. The coefficients of the PCE are computed by probabilistic collocation. We perform the GSA on simplified real conditions coming from an already built groundwater model dedicated to a subdomain of the Upper-Rhine aquifer (geometry, boundary conditions, climatic data). GSA shows that the simultaneous calibration of recharge and flow parameters is possible if the calibration is performed over at least one year. It provides also the valuable information of the sensitivity versus time, depending on

  17. NMR measurement of hydrodynamic dispersion in porous media subject to biofilm mediated precipitation reactions.

    Science.gov (United States)

    Fridjonsson, Einar O; Seymour, Joseph D; Schultz, Logan N; Gerlach, Robin; Cunningham, Alfred B; Codd, Sarah L

    2011-03-01

    Noninvasive measurements of hydrodynamic dispersion by nuclear magnetic resonance (NMR) are made in a model porous system before and after a biologically mediated precipitation reaction. Traditional magnetic resonance imaging (MRI) was unable to detect the small scale changes in pore structure visualized during light microscopy analysis after destructive sampling of the porous medium. However, pulse gradient spin echo nuclear magnetic resonance (PGSE NMR) measurements clearly indicated a change in hydrodynamics including increased pore scale mixing. These changes were detected through time-dependent measurement of the propagator by PGSE NMR. The dynamics indicate an increased pore scale mixing which alters the preasymptotic approach to asymptotic Gaussian dynamics governed by the advection diffusion equation. The methods described here can be used in the future to directly measure the transport of solutes in biomineral-affected porous media and contribute towards reactive transport models, which take into account the influence of pore scale changes in hydrodynamics.

  18. Influence of hydrodynamic parameters on tsunami run-up uncertainty induced by earthquake random slip distribtutions

    Science.gov (United States)

    Løvholt, Finn; Kim, Jihwan; Pedersen, Geir; Harbitz, Carl

    2016-04-01

    The standard approach in forward modeling of earthquake tsunamis usually assume a uniform slip pattern. This is assumption is used both in deterministic and probabilistic models. However, the slip distribution for an earthquake is subject to (aleatory) uncertainty, and consequently the induced tsunami run-up will have an uncertainty range even given the same moment magnitude and hypocentre earthquake location. Here, we present studies of run-up variability due to stochastic earthquake slip variation in both two and three dimensions. The approach taken is fully idealized, although we draw upon the experience from two of the most destructive events the last hundred years, namely the Mw8 1976 Moro Gulf earthquake and tsunami as well as the Mw9 2011 Tohoku earthquake tsunami. The former event is used to design the two-dimensional stochastic simulations, and the latter event the three-dimensional simulations. Our primary focus is not reproduce past run-up, but rather to investigate how the hydrodynamics influence uncertainty. These quantities include among others the non-hydrodynamic response during generation, frequency dispersion, friction from the seabed, and wave-breaking. We simulate tsunamis for an ensemble of synthetic random slip over an idealized shelf geometry broken into linear segments. The uncertainty propagation from source to run-up for the two different cases are discussed and compared. As demonstrated, both the dimensionality and the earthquake parameters influence the contributions of the hydrodynamic parameters on the uncertainty. Further work will be needed to explore the transitional behaviour between the two very different cases displayed here. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 603839 (Project ASTARTE).

  19. Assessment of hydrodynamics, biochemical parameters and eddy diffusivity in a semi-enclosed Ionian basin

    Science.gov (United States)

    De Serio, Francesca; Mossa, Michele

    2016-11-01

    In the framework of the Italian flagship Project RITMARE, during December 2013 a meteo-oceanographic station was installed in the Mar Grande basin, a semi-enclosed bay in Southern Italy, connected to the Ionian Sea. Due to the presence of coastal heavy industry and anthropic pressure, this marine system has experienced environmental degradation over the last decades. Therefore, much monitoring of hydrodynamics and water quality indicators is required. In fact, this monitoring makes it possible to check the real-time biochemical status of the basin and therefore promptly intervene when accidental spills occur, and to create a dataset necessary to calibrate and validate modelling systems providing forecasts. The present paper aims to analyze and discuss the long term and continuous recordings of hydrodynamic and biochemical data collected by this station, available for the period from January 2014 up to December 2014. In detail, hourly measurements of wind, waves, current velocity, water temperature, salinity, chlorophyll and turbidity concentrations were archived in monthly time-series and processed in frequency domain, using the FFT (Fast Fourier Transform), to both delineate the reciprocal effects of drivers and deduce some correlations between parameters (De Serio and Mossa, 2013). Following this, monthly surface current data were processed in order to obtain time-averaged values of the turbulent velocity components, turbulent kinetic energy and turbulent time scales. Based on these calculated turbulent parameters, the horizontal eddy diffusivity was computed with the hypothesis of homogeneous turbulence using two methods, which provided results with the same order of magnitude. These results are of interest for numerical dispersion models. Finally, only referring to the month of December 2014, the time series of the crude oil concentration was available at the station and was examined in depth. The field data enabled us to conclude that the crude oil dispersion

  20. Fluorescence photobleaching to evaluate flow velocity and hydrodynamic dispersion in nanoslits.

    Science.gov (United States)

    Cuenca, Amandine; Bodiguel, Hugues

    2012-05-01

    Velocity measurement is a key issue when studying flows below the micron scale, due to the lack of sensitivity of conventional detection techniques. We present an approach based on fluorescence photobleaching to evaluate flow velocity at the nanoscale by direct visualization. Solutions containing a fluorescent dye are injected into nanoslits. A photobleached line, created through laser beam illumination, moves through the channel due to the fluid flow. The velocity and effective diffusion coefficient are calculated from the temporal data of the line position and width respectively. The measurable velocity range is only limited by the diffusion rate of the fluorescent dye for low velocities and by the apparition of Taylor dispersion for high velocities. By controlling the pressure drop and measuring the velocity, we determine the fluid viscosity. The photobleached line spreads in time due to molecular diffusion and Taylor hydrodynamic dispersion. By taking into account the finite spatial and temporal extensions of the bleaching under flow, we determine the effective diffusion coefficient, which we find to be in good agreement with the expression of the two dimensional Taylor-Aris dispersion coefficient. Finally we analyze and discuss the role of the finite width of the rectangular slit on hydrodynamic dispersion.

  1. Effects of fundamental structure parameters on dynamic responses of submerged floating tunnel under hydrodynamic loads

    Institute of Scientific and Technical Information of China (English)

    Xu Long; Fei Ge; Lei Wang; Youshi Hong

    2009-01-01

    This paper investigates the effects of structure parameters on dynamic responses of submerged floating tunnel (SFT) under hydrodynamic loads. The structure parameters includes buoyancy-weight ratio (BWR), stiffness coefficients of the cable systems, tunnel net buoyancy and tunnel length. First, the importance of structural damp in relation to the dynamic responses of SFT is demonstrated and the mechanism of structural damp effect is discussed. Thereafter, the fundamental structure parameters are investi-gated through the analysis of SFT dynamic responses under hydrodynamic loads. The results indicate that the BWR of SFT is a key structure parameter. When BWR is 1.2, there is a remarkable trend change in the vertical dynamic response of SFT under hydrodynamic loads. The results also indicate that the ratio of the tunnel net buoyancy to the cable stiffness coefficient is not a characteristic factor affecting the dynamic responses of SFT under hydrodynamic loads.

  2. Optimisation of dispersion parameters of Gaussian plume model for CO₂ dispersion.

    Science.gov (United States)

    Liu, Xiong; Godbole, Ajit; Lu, Cheng; Michal, Guillaume; Venton, Philip

    2015-11-01

    The carbon capture and storage (CCS) and enhanced oil recovery (EOR) projects entail the possibility of accidental release of carbon dioxide (CO2) into the atmosphere. To quantify the spread of CO2 following such release, the 'Gaussian' dispersion model is often used to estimate the resulting CO2 concentration levels in the surroundings. The Gaussian model enables quick estimates of the concentration levels. However, the traditionally recommended values of the 'dispersion parameters' in the Gaussian model may not be directly applicable to CO2 dispersion. This paper presents an optimisation technique to obtain the dispersion parameters in order to achieve a quick estimation of CO2 concentration levels in the atmosphere following CO2 blowouts. The optimised dispersion parameters enable the Gaussian model to produce quick estimates of CO2 concentration levels, precluding the necessity to set up and run much more complicated models. Computational fluid dynamics (CFD) models were employed to produce reference CO2 dispersion profiles in various atmospheric stability classes (ASC), different 'source strengths' and degrees of ground roughness. The performance of the CFD models was validated against the 'Kit Fox' field measurements, involving dispersion over a flat horizontal terrain, both with low and high roughness regions. An optimisation model employing a genetic algorithm (GA) to determine the best dispersion parameters in the Gaussian plume model was set up. Optimum values of the dispersion parameters for different ASCs that can be used in the Gaussian plume model for predicting CO2 dispersion were obtained.

  3. Evaluation of the hydrodynamic behaviour of turbulence promoters in parallel plate electrochemical reactors by means of the dispersion model

    Energy Technology Data Exchange (ETDEWEB)

    Colli, A.N. [Programa de Electroquimica Aplicada e Ingenieria Electroquimica (PRELINE), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina); Bisang, J.M., E-mail: jbisang@fiq.unl.edu.ar [Programa de Electroquimica Aplicada e Ingenieria Electroquimica (PRELINE), Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2829, S3000AOM Santa Fe (Argentina)

    2011-08-30

    Highlights: {center_dot} The type of turbulence promoters has a strong influence on the hydrodynamics. {center_dot} The dispersion model is appropriate for expanded plastic turbulence promoters. {center_dot} The dispersion model is appropriate for glass beads turbulence promoters. - Abstract: The hydrodynamic behaviour of electrochemical reactors with parallel plate electrodes is experimentally studied using the stimulus-response method either with an empty reactor or with different turbulence promoters. Theoretical results which are in accordance with the analytical and numerical resolution of the dispersion model for a closed system are compared with the classical relationships of the normalized outlet concentration for open systems and the validity range of the equations is discussed. The experimental results were well correlated with the dispersion model using glass beads or expanded plastic meshes as turbulence promoters, which have shown the most advantageous performance. The Peclet number was higher than 63. The dispersion coefficient was found to increase linearly with flow velocity in these cases.

  4. The role of Joule heating in dispersive mixing effects in electrophoretic cells: hydrodynamic considerations.

    Science.gov (United States)

    Bosse, M A; Arce, P

    2000-03-01

    The analysis described in this contribution is focused on the effect of Joule heating generation on the hydrodynamics of batch electrophoretic cells (i.e., cells that do not display a forced convective term in the motion equation). The hydrodynamics of these cells is controlled by the viscous forces and by the buoyancy force caused by the temperature gradients due to the Joule heating generation. The analysis is based on differential models that lead to analytical and/or asymptotic solutions for the temperature and velocity profiles of the cell. The results are useful in determining the characteristics of the temperature and velocity profiles inside the cell. Furthermore, the results are excellent tools to be used in the analysis of the dispersive-mixing of solute when Joule heating generation must be accounted for. The analysis is performed by identifying two sequentially coupled problems. Thus, the "carrier fluid problem" and the "solute problem" are outlined. The former is associated with all the factors affecting the velocity profile and the latter is related to the convective-diffusion aspects that control the spreading of the solute inside the cell. The analysis of this contribution is centered on the discussion of the "carrier fluid problem" only. For the boundary conditions selected in the contribution, the study leads to the derivation of an analytical temperature and a "universal" velocity profile that feature the Joule heating number. The Grashof number is a scaling factor of the actual velocity profile. Several characteristics of these profiles are studied and some numerical illustrations have been included.

  5. Parameters Affecting Image-guided, Hydrodynamic Gene Delivery to Swine Liver

    Directory of Open Access Journals (Sweden)

    Kenya Kamimura

    2013-01-01

    Full Text Available Development of a safe and effective method for gene delivery to hepatocytes is a critical step toward gene therapy for liver diseases. Here, we assessed the parameters for gene delivery to the livers of large animals (pigs, 40–65 kg using an image-guided hydrodynamics-based procedure that involves image-guided catheter insertion into the lobular hepatic vein and hydrodynamic injection of reporter plasmids using a computer-controlled injector. We demonstrated that injection parameters (relative position of the catheter in the hepatic vasculature, intravascular pressure upon injection, and injection volume are directly related to the safety and efficiency of the procedure. By optimizing these parameters, we explored for the first time, the advantage of the procedure for sequential injections to multiple lobes in human-sized pigs. The optimized procedure resulted in sustained expression of the human α-1 antitrypsin gene in livers for more than 2 months after gene delivery. In addition, repeated hydrodynamic gene delivery was safely conducted and no adverse events were seen in the entire period of the study. Our results support the clinical applicability of the image-guided hydrodynamic gene delivery method for the treatment of liver diseases.

  6. A smoothed particle hydrodynamics (SPH) study of sediment dispersion on the seafloor

    Science.gov (United States)

    Tran-Duc, Thien; Phan-Thien, Nhan; Khoo, Boo Cheong

    2017-08-01

    Ocean-scale sediment dispersion and sedimentation problems are studied using the Smoothed Particle Hydrodynamics (SPH). A SPH formulation based on a mixture model for two-phase flows is developed to investigate the problem. The sediment mass transport via the settling advection and the turbulent diffusion of the suspended sediment are fully accounted for in the current SPH model. The simulations are carried out in an opened boundary domain with a unidirectional underlined current, with relevant deposition/re-suspension boundary conditions on the seafloor. The factors influencing the sedimentation process, such as the hindering and the bottom shear stress effects, are also considered. The simulation results reveal that the sediment convection near the sediment source location is caused by both the ocean current and secondary density driven flows that are created by the concurrent settling motion of suspended sediment particles, while the downstream sediment transport in the far field is only driven by the ocean current. The peak sediment concentration in the ambient ocean water is found to correlate with the sediment release rate, and the settlement rate is inversely proportional to the initial height of the disturbed sediment.

  7. A Mathematical Model for the Flow Resistance and the Related Hydrodynamic Dispersion Induced by River Dunes

    Directory of Open Access Journals (Sweden)

    Marilena Pannone

    2013-01-01

    Full Text Available Present work is aimed at the derivation of a simply usable equation for the total flow resistance associated with river bedforms, by a unifying approach allowing for bypassing some of the limiting restrictions usually adopted in similar types of studies. Specifically, we focused on the effect induced by the out-of-phase free surface undulations appearing in presence of sand dunes. The proposed expression, obtained by combining the balance of momentum referred to the control volume whose longitudinal dimension coincides with the dune wavelength and the energy balance integrated between its extreme sections, was tested by comparison with some laboratory experimental measurements available in the literature and referred to steady flow past fixed, variably rough bedforms. In terms of shear stress or friction factor, the proposed theory provides estimates in good agreement with the real data, especially if evaluated against the performances provided by other classical similar approaches. Moreover, when analyzed in terms of hydrodynamic dispersive properties as a function of the skin roughness on the basis of a previously derived analytical solution, the dune-covered beds seem to behave like meandering channels, responsible for a globally enhanced fluid particles longitudinal spreading, with a relatively reduced effect in the presence of less pronounced riverbed modelling.

  8. Hydrodynamic Performance Analysis of Propeller-rudder System with the Rudder Parameters Changing

    Institute of Scientific and Technical Information of China (English)

    Lixun Hou; Chao Wang; Xin Chang; Sheng Huang

    2013-01-01

    In order to study the effects of geometric parameters of the rudder on the hydrodynamic performance of the propeller-rudder system, the surface panel method is used to build the numerical model of the steady interaction between the propeller and rudder to analyze the relevant factors. The interaction between the propeller and rudder is considered through the induced velocities, which are circumferentially averaged, so the unsteady problem is translated to steady state. An iterative calculation method is used until the hydrodynamic performance converges. Firstly, the hydrodynamic performance of the chosen propeller-rudder system is calculated, and the comparison between the calculated results and the experimental data indicates that the calculation program is reliable. Then, the variable parameters of rudder are investigated, and the calculation results show that the propeller-rudder spacing has a negative relationship with the efficiency of the propeller-rudder system, and the rudder span has an optimal match range with the propeller diameter. Futhermore, the rudder chord and thickness both have a positive correlation with the hydrodynamic performance of the propeller-rudder system.

  9. Calculating NMR parameters in aluminophosphates: evaluation of dispersion correction schemes.

    Science.gov (United States)

    Sneddon, Scott; Dawson, Daniel M; Pickard, Chris J; Ashbrook, Sharon E

    2014-02-14

    Periodic density functional theory (DFT) calculations have recently emerged as a popular tool for assigning solid-state nuclear magnetic resonance (NMR) spectra. However, in order for the calculations to yield accurate results, accurate structural models are also required. In many cases the structural model (often derived from crystallographic diffraction) must be optimised (i.e., to an energy minimum) using DFT prior to the calculation of NMR parameters. However, DFT does not reproduce weak long-range "dispersion" interactions well, and optimisation using some functionals can expand the crystallographic unit cell, particularly when dispersion interactions are important in defining the structure. Recently, dispersion-corrected DFT (DFT-D) has been extended to periodic calculations, to compensate for these missing interactions. Here, we investigate whether dispersion corrections are important for aluminophosphate zeolites (AlPOs) by comparing the structures optimised by DFT and DFT-D (using the PBE functional). For as-made AlPOs (containing cationic structure-directing agents (SDAs) and framework-bound anions) dispersion interactions appear to be important, with significant changes between the DFT and DFT-D unit cells. However, for calcined AlPOs, where the SDA-anion pairs are removed, dispersion interactions appear much less important, and the DFT and DFT-D unit cells are similar. We show that, while the different optimisation strategies yield similar calculated NMR parameters (providing that the atomic positions are optimised), the DFT-D optimisations provide structures in better agreement with the experimental diffraction measurements. Therefore, it appears that DFT-D calculations can, and should, be used for the optimisation of calcined and as-made AlPOs, in order to provide the closest agreement with all experimental measurements.

  10. Constitutive parameter retrieval for uniaxial metamaterials with spatial dispersion

    Science.gov (United States)

    Mota, Achiles F.; Martins, Augusto; Weiner, John; Teixeira, Fernando L.; Borges, Ben-Hur V.

    2016-09-01

    We propose a constitutive parameter retrieval approach in which all electromagnetic parameters of the medium are obtained taking spatial dispersion into account. Moreover, the constraint on nonmagnetic metal/dielectric metamaterials is relaxed. This procedure is applied to metal/dielectric stacks in order to address the effects of the layer thickness, layer number, and material choice on the spatial dispersion. The results demonstrate that the investigated metal/dielectric stacks have a clear magnetic response, particularly for thicker layers. Moreover, this magnetic response is also a function of the magnitude of the | kx/k0| ratio, where kx is the wave vector parallel to the interface planes and k0 is the free-space wave number. We demonstrate that the real part of the dispersion curve flattens out (with a corresponding large imaginary part being present) as a result of the absence of propagating modes inside the metamaterial. This flat region is strongly dependent on the thickness of the layers and is a direct manifestation of spatial dispersion. Using this parameter retrieval method we calculate the Purcell factor for Rb atoms 10 nm above the surface of a Ag/TiO 2 stack with two filling factors ρ [ρ =l /(l +d ) with l and d as the metal and dielectric layer thicknesses, respectively], ρ =0.3 and ρ =0.5 , and having N =13 layers, for the emission wavelengths of 435 nm and 785 nm. Results are then compared with three different approaches, and we show that if spatial dispersion is not properly taken into account, then the Purcell factor is overestimated. Our approach shows excellent agreement with Purcell factors obtained from precise and accurate numerical calculations of the corresponding nonhomogenized structures.

  11. Hydrodynamic parameters for ErPr cryocooler regenerator fillers under steady and periodic flow conditions

    Science.gov (United States)

    Pathak, M. G.; Patel, V. C.; Ghiaasiaan, S. M.; Mulcahey, T. I.; Helvensteijn, B. P.; Kashani, A.; Feller, J. R.

    2013-12-01

    The regenerator, typically a microporous structure that is subject to periodic flow of a cryogenic fluid, is the most critical component of Pulse Tube or Stirling cryocoolers, which are widely used for high-demand defense and aerospace applications. Despite the critical impact of hydrodynamic irreversibilities in the regenerator on the overall cycle efficiency, the impact of the parameters that influence these losses are poorly understood.

  12. Hansen solubility parameter analysis on the dispersion of zirconia nanocrystals.

    Science.gov (United States)

    Wang, Sho-Hsun; Liu, Jia-Hong; Pai, Chin-Tung; Chen, Chien-Wei; Chung, Pao-Tang; Chiang, Anthony Shiaw-Tseh; Chang, Shinn-Jen

    2013-10-01

    Nanoparticle dispersible in a broad range of solvents is desirable when preparing an organic/inorganic nanocomposite. In this report, the dispersion behavior of carboxylate-grafted zirconia nanoparticle in 25 solvents covering a wide range of polarity was analyzed based on their Hansen solubility parameters (HSP). Particles grafted with alkyl-chain longer than four carbons could only be dispersed in non-polar solvents, while that grafted with acetic acid was dispersible in polar ones. However, particle modified with methacrylic acid (MA) was compatible with both types of solvents, which was rather unexpected. Further NMR analysis showed that the carboxylate-grafted samples contained a trace amount of triethanolamine (TEA) due to the particular ZrO2 synthesis process employed. The combination of the hydrophilic TEA ligand with the short hydrophobic tail of methacrylate broadened the range of compatible solvents from benzene to methanol. Such an extended solvent compatibility was observed previously only for nanoparticles covered with large polymer surfactants having both hydrophilic and hydrophobic groups. Achieving this with two small molecules having separate functional groups is crucial when one needs to maximize the inorganic content in a composite.

  13. Coupled 1D-2D hydrodynamic inundation model for sewer overflow: Influence of modeling parameters

    Directory of Open Access Journals (Sweden)

    Adeniyi Ganiyu Adeogun

    2015-10-01

    Full Text Available This paper presents outcome of our investigation on the influence of modeling parameters on 1D-2D hydrodynamic inundation model for sewer overflow, developed through coupling of an existing 1D sewer network model (SWMM and 2D inundation model (BREZO. The 1D-2D hydrodynamic model was developed for the purpose of examining flood incidence due to surcharged water on overland surface. The investigation was carried out by performing sensitivity analysis on the developed model. For the sensitivity analysis, modeling parameters, such as mesh resolution Digital Elevation Model (DEM resolution and roughness were considered. The outcome of the study shows the model is sensitive to changes in these parameters. The performance of the model is significantly influenced, by the Manning's friction value, the DEM resolution and the area of the triangular mesh. Also, changes in the aforementioned modeling parameters influence the Flood characteristics, such as the inundation extent, the flow depth and the velocity across the model domain.

  14. FEM numerical model study of electrosurgical dispersive electrode design parameters.

    Science.gov (United States)

    Pearce, John A

    2015-01-01

    Electrosurgical dispersive electrodes must safely carry the surgical current in monopolar procedures, such as those used in cutting, coagulation and radio frequency ablation (RFA). Of these, RFA represents the most stringent design constraint since ablation currents are often more than 1 to 2 Arms (continuous) for several minutes depending on the size of the lesion desired and local heat transfer conditions at the applicator electrode. This stands in contrast to standard surgical activations, which are intermittent, and usually less than 1 Arms, but for several seconds at a time. Dispersive electrode temperature rise is also critically determined by the sub-surface skin anatomy, thicknesses of the subcutaneous and supra-muscular fat, etc. Currently, we lack fundamental engineering design criteria that provide an estimating framework for preliminary designs of these electrodes. The lack of a fundamental design framework means that a large number of experiments must be conducted in order to establish a reasonable design. Previously, an attempt to correlate maximum temperatures in experimental work with the average current density-time product failed to yield a good match. This paper develops and applies a new measure of an electrode stress parameter that correlates well with both the previous experimental data and with numerical models of other electrode shapes. The finite element method (FEM) model work was calibrated against experimental RF lesions in porcine skin to establish the fundamental principle underlying dispersive electrode performance. The results can be used in preliminary electrode design calculations, experiment series design and performance evaluation.

  15. Conversion from constitutive parameters to dispersive transmission line parameters for multi-band metamaterials

    Science.gov (United States)

    Ozturk, Yusuf; Egemen Yilmaz, Asim; Ozbay, Ekmel

    2016-04-01

    In this study, we explain an approach including conversion from constitutive parameters to dispersive transmission line parameters using the double-band DNG (double-negative) properties of the circular type fishnet metamaterials. After designing the metamaterial structure, the numerical calculations and the composite right/left-handed (CRLH) modeling of circular-type metamaterials are realized in free space. Detailed dispersion characteristics give us the opportunity to explain the true behavior of the inclusions during the analysis stage. By combining the results coming from the standard retrieval procedure with the conventional CRLH theory, we calculate the actual values of the transmission line parameters for all frequency regimes. The constitutive parameters of an equivalent CRLH transmission line are derived and shown to be negative values. It is shown that the constitutive parameters present the same behavior for all negative refractive index regimes. The double-negative properties and the phase advance/lag behavior of metamaterials are observed based on the dispersive transmission line parameters.

  16. Measurement of Anisotropic Hydrodynamic Parameters of Pulse Tube or Stirling Cryocooler Regenerators

    Science.gov (United States)

    Cha, J. S.; Ghiaasiaan, S. M.; Desai, P. V.

    2006-04-01

    Pulse tube refrigeration (PTR) systems are often modeled as one-dimensional flow fields. However, recent computational fluid dynamics (CFD) — based investigations have shown that multi-dimensional flow effects can be significant in the regenerator of a PTR, especially when the aspect ratio of the regenerator is small. Anisotropic hydrodynamic parameters of regenerators are therefore needed for the realistic simulation of their multi-dimensional flow phenomena. In this paper we report on measurements of the lateral or radial permeability and Forchheimer's inertial coefficient of a widely used PTR regenerator filler. Using helium as the working fluid, steady-state pressure drops were measured over a wide range of flow rates in annular test sections that contained regenerator fillers. The aforementioned hydrodynamic parameters were then obtained by comparing the data with the results of CFD calculations that simulated the test sections and their vicinity. CFD simulations of the experiments were performed iteratively, whereby permeability and Forchheimer coefficient that brought about agreement between data and simulation results were calculated.

  17. Quantification of Single- and Multi-Phase Hydrodynamic Dispersion in Rocks Using Dynamic 3D PET Imaging

    Science.gov (United States)

    Pini, R.; Vandehey, N. T.; O'Neil, J.; Benson, S. M.

    2015-12-01

    We report results of an experimental investigation into the effects of small-scale (mm-cm) heterogeneities and hydrodynamic dispersion on miscible and immiscible displacements in a Berea Sandstone core. Pulse-radiotracer tests were carried out by measuring breakthrough curves at distinct flow rates and gas/water saturation ratios, while simultaneously imaging the internal displacement of the radioactive solution by [11C]PET. Dynamic multidimensional maps of the tracer concentration in the rock sample have been obtained with a spatial resolution of about 10 mm3 and provide evidence for significant macrodispersion effects caused by the presence of heterogeneities at the same scale. The numerical solution of the classic Advection-Dispersion Equation (ADE) applied in 1D form fails to describe the measured breakthrough curves and significantly overestimates longitudinal dispersivity. An excellent agreement with the experiments is attained by explicitly accounting for permeability heterogeneity, while reducing the contribution of "Fickian" dispersivity. Heterogeneity was introduced in the model by discretising the rock sample into independent parallel streamlines, which were generated based on a previously determined 3D permeability map, and by solving the 1D ADE for each of them. The use of streamlines is supported by direct quantitative observations from the PET scans; remarkably, this approach leads to an accurate representation of both the temporal behaviour and spatial distribution of the tracer concentration in the sample. It is shown that when the length-scale of permeability variations is similar in order as the size of the sample, the effect of the former can be as significant as hydrodynamic dispersion. The presence of a second immiscible fluid phase further complicates the flow field and, accordingly, the interpretation of the experiments. The ability to decouple these effects leads to the estimation of dispersion coefficients that aren't sample specific and

  18. Hydrodynamic parameters of micro porous media for steady and oscillatory flow: Application to cryocooler regenerators

    Science.gov (United States)

    Cha, Jeesung Jeff

    Pulse Tube Cryocoolers (PTC) are a class of rugged and high-endurance refrigeration systems that operate without a moving part at their low temperature ends, and are capable of easily reaching 120°K. These devices can also be configured in multiple stages to reach temperatures below 10 °K. PTCs are particularly suitable for applications in space, missile guiding systems, cryosurgery, medicine preservation, superconducting electronics, magnetic resonance imaging, weather observation, and liquefaction of nitrogen. Although various designs of PTCs have been in use for a few decades, they represent a dynamic and developmental field. PTCs ruggedness comes at the price of relatively low efficiency, however, and thus far they have been primarily used in high-end applications. They have the potential of extensive use in consumer products, however, should sufficiently higher efficiencies be achieved. Intense research competition is underway worldwide, and newer designs are continuously introduced. Some of the fundamental processes that are responsible for their performance are at best not fully understood, however, and consequently systematic modeling of PTC systems is difficult. Among the challenges facing the PTC research community, besides improvement in terms of system efficiency, is the possible miniaturization (total fluid volume of few cubic centimeters (cc)) of these systems. The operating characteristics of a PTC are significantly different from the conventional refrigeration cycles. A PTC implements the theory of oscillatory compression and expansion of the gas within a closed volume to achieve desired refrigeration. Regenerators and pulse tubes are often viewed as the two most complex and essential components in cryocoolers. An important deficiency with respect to the state of art models dealing with PTCs is the essentially total lack of understanding about the directional hydrodynamic and thermal transport parameters associated with periodic flow in

  19. Atmospheric-dispersion parameter evaluation in the Po Valley

    Energy Technology Data Exchange (ETDEWEB)

    Bonino, G. (Turin Univ. (Italy). Ist. di Fisica; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica); Anfossi, D. (Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica); Bacci, P.; Brusasca, G.; Longhetto, A. (Ente Nazionale per l' Energia Elettrica, Milan (Italy))

    Comparison of turbulent-diffusion parameters sigmasub(y) and sigmasub(z), evaluated through different experimental tests carried out in the Po Valley in the range (10/sup 2/:10/sup 4/) m downwind the source, under natural and unstable conditions, is presented and discussed. Two kinds of methods of tracer dispersion were adopted. The first one dealt with no-lift balloon diffusion in the range (10/sup 2/:10/sup 3/) m, while the second one was relative to SF/sub 6/ dispersion in the range (10/sup 3/:10/sup 4/) m. In the present paper the two sets of data are joined and a single series of best-fit curves covering the whole measured range (10/sup 2/:10/sup 4/) m is derived. The results show different behaviours for sigmasub(y) and sigmasub(z); in fact, it is possible to extrapolate sigmasub(y) trends from one set of data (SF/sub 6/) to the other one (no-lift balloons) without changing the analytical expression and the values of their coefficients. For sigmasub(z), instead, some new considerations are needed. In fact, for the unstable categories here considered (B/C and C) it is necessary to change the analytical form of the sigmasub(z) trend. This is due to the effect of convection resulting in an increase of dsigmasub(z)/d x. Finally, the exponent of the sampling time tau, in the sigmasub(y) vs. tau relationship, was found equal to 0.2, in the range (16:128) min.

  20. Efficient three-dimensional reconstruction of aquatic vegetation geometry: Estimating morphological parameters influencing hydrodynamic drag

    Science.gov (United States)

    Liénard, Jean; Lynn, Kendra; Strigul, Nikolay; Norris, Benjamin K.; Gatziolis, Demetrios; Mullarney, Julia C.; Bryan, Karin, R.; Henderson, Stephen M.

    2016-09-01

    Aquatic vegetation can shelter coastlines from energetic waves and tidal currents, sometimes enabling accretion of fine sediments. Simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry. However, field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements. Building on recent progress in photogrammetry and computer vision, we present a method for reconstructing three-dimensional canopy geometry. The method was used to survey a dense canopy of aerial mangrove roots, called pneumatophores, in Vietnam's Mekong River Delta. Photogrammetric estimation of geometry required 1) taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats, 2) computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3D point cloud, and 3) extracting pneumatophore locations and diameters from the point cloud data. Step 3) was accomplished by a new 'sector-slice' algorithm, yielding geometric parameters every 5 mm along a vertical profile. Photogrammetric analysis was compared with manual caliper measurements. In all 5 quadrats considered, agreement was found between manual and photogrammetric estimates of stem number, and of number × mean diameter, which is a key parameter appearing in hydrodynamic models. In two quadrats, pneumatophores were encrusted with numerous barnacles, generating a complex geometry not resolved by hand measurements. In remaining cases, moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found. By substantially reducing measurement time in the field while capturing in greater detail the 3D structure, photogrammetry has potential to improve input to hydrodynamic models, particularly for simulations of flow through large-scale, heterogenous canopies.

  1. Average hydrodynamic correction for the Brownian dynamics calculation of flocculation rates in concentrated dispersions

    Science.gov (United States)

    Urbina-Villalba, German; García-Sucre, Máximo; Toro-Mendoza, Jhoan

    2003-12-01

    In order to account for the hydrodynamic interaction (HI) between suspended particles in an average way, Honig et al. [J. Colloid Interface Sci. 36, 97 (1971)] and more recently Heyes [Mol. Phys. 87, 287 (1996)] proposed different analytical forms for the diffusion constant. While the formalism of Honig et al. strictly applies to a binary collision, the one from Heyes accounts for the dependence of the diffusion constant on the local concentration of particles. However, the analytical expression of the latter approach is more complex and depends on the particular characteristics of each system. Here we report a combined methodology, which incorporates the formula of Honig et al. at very short distances and a simple local volume-fraction correction at longer separations. As will be shown, the flocculation behavior calculated from Brownian dynamics simulations employing the present technique, is found to be similar to that of Batchelor’s tensor [J. Fluid. Mech. 74, 1 (1976); 119, 379 (1982)]. However, it corrects the anomalous coalescence found in concentrated systems as a result of the overestimation of many-body HI.

  2. COMPUTER MODELING OF HYDRODYNAMIC PARAMETERS AT BOUNDARIES OF WATER INTAKE AREA WITH FILTERING INTAKE

    Directory of Open Access Journals (Sweden)

    Boronina Lyudmila Vladimirovna

    2012-12-01

    Full Text Available Improvement of water intake technologies are of great importance. These technologies are required to provide high quality water intake and treatment; they must be sufficiently simple and reliable, and they must be easily adjustable to particular local conditions. A mathematical model of a water supply area near the filtering water intake is proposed. On its basis, a software package designated for the calculation of parameters of the supply area along with its graphical representation is developed. To improve the efficiency of water treatment plants, the authors propose a new method of their integration into the landscape by taking account of velocity distributions in the water supply area within the water reservoir where the plant installation is planned. In the proposed relationship, the filtration rate and the scattering rate at the outlet of the supply area are taken into account, and they assure more precise projections of the inlet velocity. In the present study, assessment of accuracy of the mathematical model involving the scattering of a turbulent flow has been done. The assessment procedure is based on verification of the mean values equality hypothesis and on comparison with the experimental data. The results and conclusions obtained by means of the method developed by the authors have been verified through comparison of deviations of specific values calculated through the employment of similar algorithms in MathCAD, Maple and PLUMBING. The method of the water supply area analysis, with the turbulent scattering area having been taken into account, and the software package enable to numerically estimate the efficiency of the pre-purification process by tailoring a number of parameters of the filtering component of the water intake to the river hydrodynamic properties. Therefore, the method and the software package provide a new tool for better design, installation and operation of water treatment plants with respect to filtration and

  3. An Extension of the Rasch Model for Ratings Providing Both Location and Dispersion Parameters.

    Science.gov (United States)

    Andrich, David

    1982-01-01

    An elaboration of a psychometric model for rated data, which belongs to the class of Rasch models, is shown to provide a model with two parameters, one characterizing location and one characterizing dispersion. Characteristics of the dispersion parameter are discussed. (Author/JKS)

  4. Hydrodynamic parameters estimation from self-potential data in a controlled full scale site

    Science.gov (United States)

    Chidichimo, Francesco; De Biase, Michele; Rizzo, Enzo; Masi, Salvatore; Straface, Salvatore

    2015-03-01

    A multi-physical approach developed for the hydrodynamic characterization of porous media using hydrogeophysical information is presented. Several pumping tests were performed in the Hydrogeosite Laboratory, a controlled full-scale site designed and constructed at the CNR-IMAA (Consiglio Nazionale delle Ricerche - Istituto di Metodologia per l'Analisi Ambientale), in Marsico Nuovo (Basilicata Region, Southern Italy), in order to obtain an intermediate stage between laboratory experiments and field survey. The facility consists of a pool, used to study water infiltration processes, to simulate the space and time dynamics of subsurface contamination phenomena, to improve and to find new relationship between geophysical and hydrogeological parameters, to test and to calibrate new geophysical techniques and instruments. Therefore, the Hydrogeosite Laboratory has the advantage of carrying out controlled experiments, like in a flow cell or sandbox, but at field comparable scale. The data collected during the experiments have been used to estimate the saturated hydraulic conductivity ks [ms-1] using a coupled inversion model working in transient conditions, made up of the modified Richards equation describing the water flow in a variably saturated porous medium and the Poisson equation providing the self-potential ϕ [V], which naturally occurs at points of the soil surface owing to the presence of an electric field produced by the motion of underground electrolytic fluids through porous systems. The result obtained by this multi-physical numerical approach, which removes all the approximations adopted in previous works, makes a useful instrument for real heterogeneous aquifer characterization and for predictive analysis of its behavior.

  5. A multiple-relaxation-time lattice-boltzmann model for bacterial chemotaxis: effects of initial concentration, diffusion, and hydrodynamic dispersion on traveling bacterial bands.

    Science.gov (United States)

    Yan, Zhifeng; Hilpert, Markus

    2014-10-01

    Bacterial chemotaxis can enhance the bioremediation of contaminants in aqueous and subsurface environments if the contaminant is a chemoattractant that the bacteria degrade. The process can be promoted by traveling bands of chemotactic bacteria that form due to metabolism-generated gradients in chemoattractant concentration. We developed a multiple-relaxation-time (MRT) lattice-Boltzmann method (LBM) to model chemotaxis, because LBMs are well suited to model reactive transport in the complex geometries that are typical for subsurface porous media. This MRT-LBM can attain a better numerical stability than its corresponding single-relaxation-time LBM. We performed simulations to investigate the effects of substrate diffusion, initial bacterial concentration, and hydrodynamic dispersion on the formation, shape, and propagation of bacterial bands. Band formation requires a sufficiently high initial number of bacteria and a small substrate diffusion coefficient. Uniform flow does not affect the bands while shear flow does. Bacterial bands can move both upstream and downstream when the flow velocity is small. However, the bands disappear once the velocity becomes too large due to hydrodynamic dispersion. Generally bands can only be observed if the dimensionless ratio between the chemotactic sensitivity coefficient and the effective diffusion coefficient of the bacteria exceeds a critical value, that is, when the biased movement due to chemotaxis overcomes the diffusion-like movement due to the random motility and hydrodynamic dispersion.

  6. Anisotropic steady-flow hydrodynamic parameters of microporous media applied to pulse tube and Stirling cryocooler regenerators

    Science.gov (United States)

    Clearman, W. M.; Cha, J. S.; Ghiaasiaan, S. M.; Kirkconnell, C. S.

    2008-03-01

    The hydrodynamic parameters associated with steady longitudinal and lateral (radial) flow of helium in several widely-used pulse tube and Stirling cryocooler regenerator fillers were measured and correlated in this investigation. Pressure drops in test sections packed with regenerator fillers were experimentally measured. Computational fluid dynamics (CFD) models of the regenerator test sections and their vicinities were developed and simulations were performed in which the regenerator test sections were modeled as porous media. By iterative repetition of the simulations, the longitudinal and radial permeability and Forchheimer inertial coefficients were determined such that they would lead to agreement between experimental measurements and the simulations. The regenerator fillers included 325 and 400 mesh stainless steel screens, stainless steel metal foam, sintered 400 mesh stainless steel screens, and a stack of micromachined perforated plates. The hydrodynamic response of the regenerator fillers were also correlated as friction factors. The results confirm that the aforementioned regenerator fillers are anisotropic.

  7. Determining the effective parameters of a Shallow-Water bottom from wideband signal spectra under conditions of hydrodynamic variability

    Science.gov (United States)

    Grigor'ev, V. A.; Katsnel'son, B. G.; Lynch, J. F.

    2016-05-01

    We propose a method for determining the effective parameters of the upper marine sediment layer on extended tracks from the spectra of wideband signals in conditions of hydrodynamic variability. As an example, we consider the Shallow Water 2006 experiment on the Atlantic shelf of the United States, which used signals with a band of 300 ± 30 Hz received by a vertical array. The length of the track was ~20 km at a sea depth of ~80 m. Frequency-mode analysis of the received signals showed that spatiotemporal fluctuations of the wave medium lead to random changes in mode amplitudes while retaining the relative stability of the mode phase difference. This is the basis of the proposed method, which makes it possible to determine the track-averaged values of the sound velocity in the bottom and density of the bottom under conditions of hydrodynamic variability.

  8. Type Ia Supernova Intrinsic Magnitude Dispersion and the Fitting of Cosmological Parameters

    CERN Document Server

    Kim, Alex

    2011-01-01

    I present an analysis for fitting cosmological parameters from a Hubble Diagram of a standard candle with unknown intrinsic magnitude dispersion. The dispersion is determined from the data themselves, simultaneously with the cosmological parameters. This contrasts with the strategies used to date. The advantages of the presented analysis are that it is done in a single fit (it is not iterative), it provides a statistically founded and unbiased estimate of the intrinsic dispersion, and its cosmological-parameter uncertainties account for the intrinsic dispersion uncertainty. Applied to Type Ia supernovae, my strategy provides a statistical measure to test for sub-types and assess the significance of any magnitude corrections applied to the calibrated candle. Parameter bias and differences between likelihood distributions produced by the presented and currently-used fitters are negligibly small for existing and projected supernova data sets.

  9. Torpedo Hydrodynamic Parameter Estimation: Application to Shallow Water Mobile Platform (SWAMP) Sea Run Data

    Science.gov (United States)

    1980-02-01

    maximum likelihood cost\\ DD I JA 7 1473 EDITION Of I NOV 66 IS OBSOLETE UNCLASSIFIED Sh4 012.LF.046601SECURITY CLASSIFICATION OF THIS PAGEt (OW"f Dese ...coefficients. Analytical methods based on these experimental data were also developed for estimating hydrodynamic coefficients of new torpedo...gain matrix. The gain matrix was obtained with some assumptions about the noise statistics and some experimentation with the filter. The remainder of

  10. Comparing a simple methodology to evaluate hydrodynamic parameters with rainfall simulation experiments

    Science.gov (United States)

    Di Prima, Simone; Bagarello, Vincenzo; Bautista, Inmaculada; Burguet, Maria; Cerdà, Artemi; Iovino, Massimo; Prosdocimi, Massimo

    2016-04-01

    Studying soil hydraulic properties is necessary for interpreting and simulating many hydrological processes having environmental and economic importance, such as rainfall partition into infiltration and runoff. The saturated hydraulic conductivity, Ks, exerts a dominating influence on the partitioning of rainfall in vertical and lateral flow paths. Therefore, estimates of Ks are essential for describing and modeling hydrological processes (Zimmermann et al., 2013). According to several investigations, Ks data collected by ponded infiltration tests could be expected to be unusable for interpreting field hydrological processes, and particularly infiltration. In fact, infiltration measured by ponding give us information about the soil maximum or potential infiltration rate (Cerdà, 1996). Moreover, especially for the hydrodynamic parameters, many replicated measurements have to be carried out to characterize an area of interest since they are known to vary widely both in space and time (Logsdon and Jaynes, 1996; Prieksat et al., 1994). Therefore, the technique to be applied at the near point scale should be simple and rapid. Bagarello et al. (2014) and Alagna et al. (2015) suggested that the Ks values determined by an infiltration experiment carried applying water at a relatively large distance from the soil surface could be more appropriate than those obtained with a low height of water pouring to explain surface runoff generation phenomena during intense rainfall events. These authors used the Beerkan Estimation of Soil Transfer parameters (BEST) procedure for complete soil hydraulic characterization (Lassabatère et al., 2006) to analyze the field infiltration experiment. This methodology, combining low and high height of water pouring, seems appropriate to test the effect of intense and prolonged rainfall events on the hydraulic characteristics of the surface soil layer. In fact, an intense and prolonged rainfall event has a perturbing effect on the soil surface

  11. Modelling of tidal hydrodynamics for a tropical ecosystem with implications for pollutant dispersion (Cochin Estuary, Southwest India)

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Reddy, G.S.; Revichandran, C.; Srinivas, K.; Vijayan, P.R.; Thottam, T.J.

    Tidal circulation in the Cochin Estuary, a moderately polluted estuary along the southwest coast of India, was studied using a 2D hydrodynamic model. The predicted tides and currents showed very good agreement with measured tides. Particle...

  12. Study Pulse Parameters versus Cavity Length for Both Dispersion Regimes in FM Mode Locked

    Directory of Open Access Journals (Sweden)

    Bushra Razooky Mhdi

    2015-03-01

    Full Text Available To demonstrate the effect of changing cavity length for  FM mode locked on pulse parameters and make comparison for both dispersion regime , a plot for each pulse parameter as Lr function are presented for normal and anomalous dispersion regimes. The analysis is based on the theoretical study and the results of numerical simulation using MATLAB. The effect of both normal and anomalous dispersion regimes on output pulses is investigate Fiber length effects on pulse parameters are investigated by driving the modulator into different values. A numerical solution for model equations using fourth-fifth order, Runge-Kutta method is performed through MATLAB 7.0 program. Fiber length effect on pulse parameters is investigated by driving the modulator into different values of lengths. Result shows that, the output pulse width from the FM mode locked equals to τ= 501ns anomalous regime and τ=518ns in normal regime.

  13. Study of Parameters Effect on Hydrodynamics of a Gas-Solid Chamber Experimentally and Numerically

    Directory of Open Access Journals (Sweden)

    Rahimzadeh Hassan

    2012-04-01

    Full Text Available In this research, gas velocity, initial static bed height and particle size effect on hydrodynamics of a non-reactive gas–solid fluidized bed chamber were studied experimentally and computationally. A multi fluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this chamber and momentum exchange coefficients were calculated by using the Syamlal- O’Brien drag functions. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops predicted by the simulations at different particle sizes and initial static bed height were in good agreement with experimental measurements at superficial gas velocity higher than the minimum fluidization velocity. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Furthermore, this comparison showed that the model can predict hydrodynamic behavior of gas solid fluidized bed chambers reasonably well.

  14. Hydrodynamic shocks in microroller suspensions

    Science.gov (United States)

    Delmotte, Blaise; Driscoll, Michelle; Chaikin, Paul; Donev, Aleksandar

    2017-09-01

    We combine experiments, large-scale simulations, and continuum models to study the emergence of coherent structures in a suspension of magnetically driven microrollers sedimented near a floor. Collective hydrodynamic effects are predominant in this system, leading to strong density-velocity coupling. We characterize a uniform suspension and show that density waves propagate freely in all directions in a dispersive fashion. When sharp density gradients are introduced in the suspension, we observe the formation of a shock. Unlike Burgers' shocklike structures observed in other active and driven confined hydrodynamic systems, the shock front in our system has a well-defined finite width and moves rapidly compared to the mean suspension velocity. We introduce a continuum model demonstrating that the finite width of the front is due to far-field nonlocal hydrodynamic interactions and governed by a geometric parameter, the average particle height above the floor.

  15. Sediment grain size and hydrodynamics in Mediterranean coastal lagoons: Integrated classification of abiotic parameters

    Indian Academy of Sciences (India)

    Emanuela Molinaroli; Alessandro Sarretta; Christian Ferrarin; Emanuele Masiero; Antonietta Specchiulli; Stefano Guerzoni

    2014-07-01

    Integrated classification maps were produced by combining sediment grain-size and hydrological data (water renewal time, WRT) from two Mediterranean lagoons, Lesina (LL) and Varano (LV), Italy. The geophysical characteristics of the two basins, derived from detailed bathymetric charts, are quite distinct: ∼30% of LL (mean depth ∼1 m) but only 3% of LV (mean depth ∼3 m) is shallower than 1 m. The sediments of both lagoons are mainly composed of mud (∼80%). A detailed multivariate analysis of grainsize data by EntropyMax classified the lagoon beds of LL and LV into five sedimentary facies. WRT data, computed by a hydrodynamic model, indicated different hydrological conditions in the two lagoons: LL showed a sharp west–east gradient, with a basin-wide average of ∼190 days, whilst LV showed a fairly uniform distribution and a higher basin-wide average (∼260 days). The distribution of sedimentary facies and water renewal times were combined in a composite map representing the distribution of environmental patterns. The approach outlined in this study can be used to improve zonation schemes by providing a hydromorphological perspective on transitional and coastal environments.

  16. Optimizing sonication parameters for dispersion of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haibo [Fraunhofer Institute for Electronic Nano Systems (Fraunhofer ENAS), 09126 Chemnitz (Germany); Graduate University of the Chinese Academy of Sciences, Beijing (China); State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, 110016 Shenyang (China); Hermann, Sascha, E-mail: sascha.hermann@zfm.tu-chemnitz.de [Center for Microtechnologies (ZfM), Chemnitz University of Technology, 09126 Chemnitz (Germany); Schulz, Stefan E.; Gessner, Thomas [Fraunhofer Institute for Electronic Nano Systems (Fraunhofer ENAS), 09126 Chemnitz (Germany); Center for Microtechnologies (ZfM), Chemnitz University of Technology, 09126 Chemnitz (Germany); Dong, Zaili [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, 110016 Shenyang (China); Li, Wen J., E-mail: wenjungli@gmail.com [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, 110016 Shenyang (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong SAR (China)

    2012-10-26

    Graphical abstract: We study the dispersing behavior of SWCNTs based on the surfactant and the optimization of sonication parameters including the sonication power and running time. Highlights: Black-Right-Pointing-Pointer We study the optimization of sonication for the surfactant-based dispersion of SWCNTs. Black-Right-Pointing-Pointer The absorption spectrum of SWCNT solution strongly depend on the sonication conditions. Black-Right-Pointing-Pointer The sonication process has an important influence on the average length and diameters of SWCNTs in solution. Black-Right-Pointing-Pointer Centrifugation mainly contributes to the decrease of nonresonant absorption background. Black-Right-Pointing-Pointer Under the same sonication parameters, the large-diameter tip performs dispersion of SWCNTs better than the small-diameter tip. -- Abstract: Non-covalent functionalization based on surfactants has become one of the most common methods for dispersing of single-walled carbon nanotubes (SWCNTs). Previously, efforts have mainly been focused on experimenting with different surfactant systems, varying their concentrations and solvents. However sonication plays a very important role during the surfactant-based dispersion process for SWCNTs. The sonication treatment enables the surfactant molecules to adsorb onto the surface of SWCNTs by overcoming the interactions induced by the hydrophobic, electrostatic and van der Waals forces. This work describes a systematic study of the influence of the sonication power and time on the dispersion of SWCNTs. UV-vis-NIR absorption spectra is used to analyze and to evaluate the dispersion of SWCNTs in an aqueous solution of 1 w/v% sodium deoxycholate (DOC) showing that the resonant and nonresonant background absorption strongly depends on the sonication conditions. Furthermore, the diameter and length of SWCNTs under different sonication parameters are investigated using atomic force microscopy (AFM).

  17. Optical Dispersion Parameters with Different Orientations for SrLaAlO4 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The different optical dispersion parameters of SrLaAlO4 single crystals have been studied by the transmission andreflection measurements at normal incidence for the three orientations 001, 100 and 101 in the spectral range400 nm~2500 nm.The optical absorption data revealed the existance of allowed indirect and direct transition. Therefractive index has abnormal behaviour in the spectral region 400~900 nm, but has a normal one in the higherwavelength region. The optical dispersion parameters, the single oscillator energy Eo and the dispersion energy Edwere determined and indicated the ionic structure of the material. The high-frequency dielectric constant, the latticedielectric constant and the electronic polarizability were determined by the free carriers and the lattice vibrationmodes. The real dielectric constant e1, the dielectric loss tangent (tanδ), the volume (VELF) and the surface energyloss function (SELF) have also been discussed.

  18. Effect of Macroporous on Soil Hydrodynamic Dispersion Coefficient%大孔隙对土壤水动力弥散系数影响的实验研究

    Institute of Scientific and Technical Information of China (English)

    尚熳廷; 冯杰; 刘佩贵

    2009-01-01

    Using the bromine ion as a tracer, hydrodynamic dispersion coefficient and dispersivity of disturbed and undisturbed soil are given more detailed experimental study in this paper. The hydrodynamic dispersion coefficient of disturbed soil is obtained from normal distribution function method. And by analysis the proportional relation between hydrodynamic dispersion coefficient and average porous velocity, its dispersivity is achieved. Besides, comparing on the simulated values with observed values of concentration of bromine ion, the undisturbed soil's hy-drodynamic dispersion coefficient and dispersivity are obtained. Finally, their analysis results show the following two points. The dispersivity of disturbed and undisturbed soil is at the same magnitude. However, because of the average porous velocity influences, the hydrodynamic dispersion coefficient of undisturbed soil is two orders of magnitude higher than that of disturbed soil.%以Br-作示踪剂,于室内实验测定原状土和扰动土的水动力弥散系数和弥散度,并进行了详细地分析研究.其中,用正态分布函数法求出了扰动土的水动力弥散系数,并通过水动力弥散系数与平均孔隙流速成正比的关系求出了其弥散度;然后,根据模拟得到的底孔出流液中离子浓度与实测值对比分析的结果,用反演方法得到原状土的水动力弥散系数及弥散度.结果表明,原状土的弥散度值与扰动土处在同一个数量级上,但其水动力弥散系数却比扰动土大2个数量级.

  19. Determination of Diffusion and Dispersion Parameters for Flow in Porous Media

    OpenAIRE

    Kohno, Iichiro; Nishigaki, Makoto

    1982-01-01

    The purposes of this research is an investigation of the intrusion of sea water into coastal aquifers. For this subject, this paper deals with proposing rational methods of getting diffusion coefficient and dispersion parameter for flow in porous media in a laboratory. These parameters of soil are indispensable in order to apply an analytical approach or a numerical approach to actual salt water intrusion problems. Experimental apparatuses were constructed and test procedures were also develo...

  20. Geometrical parameters dependence towards ultra-flat dispersion square-lattice PCF with selective liquid infiltration

    CERN Document Server

    Maji, Partha Sona

    2014-01-01

    We have performed a numerical analysis of the structural dependence of the PCF parameters towards ultra-flat dispersion in the C-band of communication wavelength. The technique is based on regular square-lattice PCF with all the air-hole of same uniform diameter and the effective size of the air-holes are modified with a selective infiltration of the air-holes with liquids. The dependence of the PCF structural parameters namely air-hole diameter and hole-to-hole distance along with the infiltrating liquid has been investigated in details. It is shown that the infiltrating liquid has critical influence on both the slope and value of dispersion, while pitch only changes the dispersion value whereas air-hole diameter modifies the slope of the dispersion. Our numerical investigation establishes dispersion values as small as 0+-0.58ps/(nm-km) over a bandwidth of 622nm in the communication wavelength band (C-band). The proposed design study will be very helpful in high power applications like broadband smooth super...

  1. Cosmological and astrophysical parameters from the SDSS flux power spectrum and hydrodynamical simulations of the Lyman-alpha forest

    CERN Document Server

    Viel, M; Viel, Matteo; Haehnelt, Martin G.

    2006-01-01

    (abridged) The flux power spectrum of the Lyman-alpha forest in quasar (QSO) absorption spectra is sensitive to a wide range of cosmological and astrophysical parameters and instrumental effects. Modelling the flux power spectrum in this large parameter space to an accuracy comparable to the statistical uncertainty of large samples of QSO spectra is very challenging. We use here a coarse grid of hydrodynamical simulations run with GADGET-2 to obtain a ``best guess'' model around which we calculate a finer grid of flux power spectra using a Taylor expansion of the flux power spectrum to first order. We find that the SDSS flux power spectrum alone is able to constrain a wide range of parameters including the amplitude of the matter power spectrum sigma_8, the matter density Omega_m, the spectral index of primordial density fluctuations n, the effective optical depth tau_eff and its evolution. The thermal history of the Intergalactic Medium (IGM) is, however, poorly constrained and the SDSS data favour either an...

  2. Determination of dispersion parameters of thermally deposited CdTe thin film

    Science.gov (United States)

    Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

    2016-05-01

    Cadmium Telluride (CdTe) thin film was deposited onto glass substrates under a vacuum of 5 × 10-6 torr by using thermal evaporation technique. The prepared film was characterized for dispersion analysis from reflectance spectra within the wavelength range of 300 nm - 1100 nm which was recorded by using UV-Visible spectrophotometer. The dispersion parameters (oscillator strength, oscillator wavelength, high frequency dielectric constant, long wavelength refractive index, lattice dielectric constant and plasma resonance frequency) of CdTe thin film were investigated using single sellimeir oscillator model.

  3. Adjoint Parameter Sensitivity Analysis for the Hydrodynamic Lattice Boltzmann Method with Applications to Design Optimization

    DEFF Research Database (Denmark)

    Pingen, Georg; Evgrafov, Anton; Maute, Kurt

    2009-01-01

    We present an adjoint parameter sensitivity analysis formulation and solution strategy for the lattice Boltzmann method (LBM). The focus is on design optimization applications, in particular topology optimization. The lattice Boltzmann method is briefly described with an in-depth discussion...

  4. Application of the genetic algorithms to the identification of the hydrodynamic parameters

    Directory of Open Access Journals (Sweden)

    Sawadogo Wenddabo Olivier

    2015-01-01

    Full Text Available In this work, we propose an adaptation of the algorithm Non-dominated Sorting Genetic Algorithm-II (NSGA-II proposed by deb. et al. (2002 to solve multi-objective problems to the resolution of mono-objective problem. Contrary to the majority of the genetic algorithms, we did not define a probability of crossing. After having applied our algorithm to functions test, we then used it to identify hydrogeologic parameters where the boundaries values and the source term are supposed to be unknown besides the permeability. The direct problem was solved by using the finite elements of Galerkin on freefem++ and the genetic algorithm  was programmed in Matlab. Then we carried out a coupling of the two codes to identify the parameters.

  5. An explanation of dispersion states of single-walled carbon nanotubes in solvents and aqueous surfactant solutions using solubility parameters.

    Science.gov (United States)

    Ham, Hyeong Taek; Choi, Yeong Suk; Chung, In Jae

    2005-06-01

    Dispersions of single-walled carbon nanotubes in various solvents and aqueous surfactant emulsions were investigated to correlate the degree of dispersion state with Hansen solubility parameters (deltat2=deltad2+deltap2+deltah2). It was found that the nanotubes were dispersed or suspended very well in the solvents with certain dispersive component (deltad) values. They were precipitated in the solvents with high polar component (deltap) values or hydrogen-bonding component (deltah) values. The solvents in the dispersed group occupied a certain region in a 3-dimensional space of three components. The surfactants with a lipophilic group equal to and longer than decyl, containing 9 methylene groups and 1 methyl group, contributed to the dispersion of nanotubes in water. The surfactants in the dispersed group had a lower limit in the dispersive component (deltad) of the Hansen parameter.

  6. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  7. Effect of Various Parameters on the Dispersion of Ultra Fine Iron Ore Slurry. Part-2.

    Directory of Open Access Journals (Sweden)

    M. I. Abro

    2010-12-01

    Full Text Available Among the list of dispersion parameters effect of solid concentration, slurry pH, stirring speed and time were studied in Part I for stablization of Dilband iron ore slurry. In Part II the study is extended to survey most appropriate dispersant and its optimal dose. In present study sodium silicate (SS, sodium hexametaphosphate (SHMP, sodium pyrophosphate (SPP, and ethylene-diamine-tetraacetatic-acid (EDTA dispersants were used. The different doses of these dispersants were studied at solid concentration 7.5%, pH 10.5, stirring speed 2000 rpm, and stirring time 5min, as optimal conditions found in Part I. Marginal improvement in slurry stabilization with addition of SS, SHMP, SPP, and EDTA was noted, however EDTA found to be most effective in stabilizing the slurry as compared to others. For the different doses of EDTA, SPP, SHMP, and SS tested, the best disperse ability was obtained at concentration of 0.135%, 0.025%, 0.2%, and 1.25% respectively.

  8. Hydrodynamic resistance parameters for ErPr rare-earth regenerator material under steady and periodic flow conditions

    Science.gov (United States)

    Pathak, M. G.; Helvensteijn, B. P.; Patel, V. C.; Ghiaasiaan, S. M.; Mulcahey, T. I.; Kashani, A.; Feller, J. R.

    2014-01-01

    The regenerator, typically a microporous structure that is subject to periodic flow of a cryogenic fluid, is a critical component of pulse tube or Stirling cryocoolers, which are widely used for high-demand aerospace and defense applications. In this investigation, experiments were conducted in which steady and oscillatory flows of helium were imposed on ErPr rare-Earth regenerator filler material and mass flow and pressure drop data were recorded under ambient temperature conditions. A computational fluid dynamics (CFD)-assisted method was applied for the analysis and interpretation of the experimental data. The permeability and inertial coefficients that lead to agreement between the experimental data and computational simulations were iteratively obtained. The Darcy permeability and Forchheimer inertial coefficients were obtained and were found to be functions of the system charge pressure, operating frequency, and compressor piston stroke within the studied range of interest. The results also exhibit that the periodic flow hydrodynamic resistance parameters are in general different than steady flow parameters.

  9. Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

    Science.gov (United States)

    Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

    2017-06-01

    An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

  10. Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

    Science.gov (United States)

    Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

    2016-12-01

    An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

  11. Fast hydrodynamic model for medium- and long-term dispersion in seawater in the English Channel and southern North Sea, qualitative and quantitative validation by radionuclide tracers

    Science.gov (United States)

    du Bois, P. Bailly; Dumas, F.

    The database for medium- and long-term model validation using 125Sb released by the La Hague reprocessing plant includes 1400 measurements performed between 1987 and 1994 in the English Channel and the North Sea and data for each release since 1982. Antimony-125 has a conservative behaviour in water masses over a period of several years. These data can be used qualitatively and quantitatively to compare the measured concentrations with the calculated ones and quantities of tracers. Tritium measurements are also available for model calibration. A two-dimensional hydrodynamic model has been developed to allow repetitive long-term simulations. This model uses a database of residual tidal currents calculated using the Lagrangian barycentric method [Salomon, J.C., Guéguéniat, P., Orbi, A., Baron, Y., 1988. A Lagrangian model for long-term tidally induced transport and mixing. Verification by artificial radionuclide concentrations. In: Guary, J.C., Guéguéniat, P., Pentreath, R.J. (Eds.), Radionuclides: A Tool for Oceanography, Cherbourg 1-5 June, 1987. Elsevier Applied Science Publishers, London, New York, pp. 384-394]. The area covered by the model includes the English Channel, the southern North Sea and the Irish Sea with a mesh size of 1 km. The main adjustment parameters of this model are the sources of wind data used and the calculation method for evaluating wind stress at the sea surface. With these parameters, the fluxes of radionuclides and water masses in the English Channel and the North Sea were balanced for the whole period of field measurements (1987-1994). The correlation factor between individual measurements in seawater and calculation results is 0.88 with an average error of ±54%, the error attributable to the measurement process being 15% on average. The mean flux through the Dover Strait is 126,000 m 3 s -1, close from the one obtained from previous studies [Salomon, J.C., Breton, M., Guéguéniat, P. 1993. Computed residual flow through the Dover

  12. Slow modes in the Hermean magnetosphere: effect of the solar wind hydrodynamic parameters and IMF orientation

    CERN Document Server

    Varela, J; Moncuquet, M

    2016-01-01

    The aim of this study is to simulate the slow mode structures in the Hermean magnetosphere. We use a single fluid MHD model and a multipolar expansion of the Northward displaced Hermean magnetic field, to perform simulations with different solar wind parameter to foreseen the most favorable configuration for the formation of slow modes, attending to the solar wind density, velocity, temperature and the interplanetary magnetic field orientation. If the interplanetary magnetic field is aligned with the Mercury-Sun direction, the magnetic axis of Mercury in the Northward direction or the planet orbital plane, slow mode structures are observed nearby the South pole. If the orientation is in the Sun-Mercury or Northward directions, slow mode structures are observed nearby the North pole, but smaller compared with the structures near the South pole. Increase the density or the solar wind velocity avoids the formation of slow modes structures, not observed for a dynamic pressure larger than $6.25 \\cdot 10^{-9}$ Pa i...

  13. Lagrangian model of zooplankton dispersion: numerical schemes comparisons and parameter sensitivity tests

    Institute of Scientific and Technical Information of China (English)

    QIU Zhongfeng; Andrea M. DOGLIOLI; HE Yijun; Francois CARLOTTI

    2011-01-01

    This paper presents two comparisons or tests for a Lagrangian model of zooplankton dispersion: numerical schemes and time steps. Firstly, we compared three numerical schemes using idealized circulations. Results show that the precisions of the advanced Adams-Bashfold-Moulton (ABM) method and the Runge-Kutta (RK) method were in the same order and both were much higher than that of the Euler method. Furthermore, the advanced ABM method is more efficient than the RK method in computational memory requirements and time consumption. We therefore chose the advanced ABM method as the Lagrangian particle-tracking algorithm. Secondly, we performed a sensitivity test for time steps, using outputs of the hydrodynamic model, Symphonie. Results show that the time step choices depend on the fluid response time that is related to the spatial resolution of velocity fields. The method introduced by Oliveira et al. in 2002 is suitable for choosing time steps of Lagrangian particle-tracking models, at least when only considering advection.

  14. Relationships between hydrodynamic parameters and grain size in two contrasting transitional environments: The Lagoons of Venice and Cabras, Italy

    Science.gov (United States)

    Molinaroli, E.; Guerzoni, S.; De Falco, G.; Sarretta, A.; Cucco, A.; Como, S.; Simeone, S.; Perilli, A.; Magni, P.

    2009-07-01

    A comparison was made of shallow water sediments from the Lagoon of Venice (LV) and the Lagoon of Cabras (LC), comparing depositional environments and exploring the relationships between hydrodynamics and sedimentological parameters . The two water bodies are very different in size (LV: 360 km 2; LC: 22 km 2), and the sediments predominantly consist of silty-clay (LV: Mz ≈ 26 μm; LC: Mz ≈ 6 μm). However, there are large differences between the two lagoons with respect to sand (LV: mean 19%; LC: mean ~ 3%) and clay (LV: mean 20%; LC: mean 45%) contents. The Lagoon of Venice (mean depth ~ 1 m) can be considered a tidal basin, whereas the Lagoon of Cabras (mean depth ~ 2 m) has the character of a coastal lake in which wind is the main hydrodynamic forcing factor. A comparison of sediment grain-size distributions with water circulation patterns in different parts of the lagoons highlighted some interesting differences. Grain-size analyses of samples reveal a deficiency of particles around 8 μm in the LC, which is interpreted as reflecting the transition between cohesive flocs/aggregates and non-cohesive coarser silt particles, while the transition limit in the LV is ~ 20 μm. Thus, particles are cohesive below 8 μm in the LC and below ~ 20 μm in the LV. This is probably because of the differences in the clay/silt ratio, which is much lower in the LV (~ 0.3) than in LC (~ 1), conferring a "silt-dominated network structure" on most of the LV sediments. The hydrographical data used were root mean square velocity (RMSV) and water residence time (WRT), computed under the main forcing conditions. The results show a general correlation between RMSV and sortable silt in the LC, and between RMSV and coarser sediments (63-105 μm) in the LV. Some significant differences between the lagoons were detected in the degree of correlation between WRT and grain size. Root mean square velocity (~ 7 cm s - 1 in the LV and ~ 3 cm s - 1 in the LC) was a greater forcing factor in

  15. Modelling of tidal hydrodynamics for a tropical ecosystem with implications for pollutant dispersion (Cohin Estuary, Southwest India)

    Science.gov (United States)

    Balachandran, Kizhakkepat Kalathil; Reddy, Guddemmari Sidha; Revichandran, Chenicherry; Srinivas, Kotamarpi; Vijayan, Panachikkal Ramakrishnan; Thottam, Tony Joseph

    2008-11-01

    Tidal circulation in the Cochin Estuary, a moderately polluted estuary along the southwest coast of India, was studied using a 2D hydrodynamic model. The predicted tides and currents showed very good agreement with measured tides. Particle trajectories and residual currents computed from the model have been used to classify the study region into three zones: northern estuary, central estuary, and southern estuary. The central estuary is dynamic, whereas the other two zones are relatively weak. An amplification of measured tides in the south estuary during March indicates the presence of standing waves caused by the hydraulic barrier at Thanneermukkom. Model results suggest that the northern and southern zones are sensitive to environmental pollution. The present level of pollution in the northern estuary is due to the direct release of industrial effluents into the river Periyar, which can be minimized if they are brought down to central estuary for disposal. The concept of different zones in the estuary will be useful to planners in protecting the vulnerable regions of this productive ecosystem from human interventions.

  16. Influence of preparation conditions on the dispersion parameters of sprayed iron oxide thin films

    Science.gov (United States)

    Akl, Alaa A.

    2010-10-01

    Iron oxide thin films were prepared by spray pyrolysis technique (SPT) at various substrate temperatures ( Tsub) and different deposition time. X-ray diffraction (XRD) analysis showed that, at Tsub ≥ 350 °C, a single phase of α-Fe 2O 3 film is formed which has the rhombohedral structure. Moreover, the crystallinity was improved by increasing Tsub. The effect of Tsub as well as deposition time on the optical dispersion of these films has been investigated. The optical transmittance and reflectance measurements were performed by using spectrophotometer in the wavelength range from 300 to 2500 nm. The refractive index was determined by using Murmann's exact equation. It was observed that, the refractive index increased with increasing in both the Tsub and film thickness. The optical dispersion parameters have been evaluated and analyzed by using Wemple-Didomenico equation. The obtained results showed that, the dielectric properties have weak dependencies of growth temperature and film thickness. At Tsub ≥ 350 °C, the average values of oscillator energy, Eo and dispersion energy, Ed were found to be 5.96 and 34.08 eV. While at different thickness, the average values of dispersion energies were found to be 3.93 and 17.08 eV. Also, the average values of oscillator strength So and single resonant frequency ωo were estimated 10.78 × 10 13 m -2 and 5.99 × 10 15 Hz, while at different thickness were evaluating 4.81 × 10 13 m -2 and 6.11 × 10 15 Hz. Furthermore, the optical parameters such as wavelength of single oscillator λo, plasma frequency ωp, and dielectric constant ɛ have been evaluated. The carrier concentration Nopt by using Drud's theory was obtained the range of 5.07 × 10 25 m -3 to 1.04 × 10 26 m -3.

  17. The influence of paint dispersion parameters on the spectral selectivity of black-pigmented coatings

    Energy Technology Data Exchange (ETDEWEB)

    Gunde, M.K.; Orel, Z.C. [National Institute of Chemistry, Ljubljana (Slovenia); Hutchins, M.G. [Oxford Brookes University, Oxford (United Kingdom). School of Engineering

    2003-10-31

    The optical properties of variously prepared black-pigmented solar absorbing paints were calculated in terms of their effective absorption and scattering abilities. The phenomenological two-parameter Kubelka-Munk effective medium theory was applied. Paints with the same composition were prepared for different degrees of pigment dispersion and characterized by the average size of pigment agglomerates present in the pigment/vehicle system. Prepared paints were applied to aluminium foil in two ways, by coil coating and by spraying. The size of coarse pigment particles and the paint application technique influence the spectral selectivity and thus determine the final performance of spectrally selective surfaces. (author)

  18. NUMEREICAL ANALYSIS OF FOUR WAVE MIXING AND EXTRACTION OF DISPERSION PARAMETERS OF THE FIBRE

    Directory of Open Access Journals (Sweden)

    S.Sugumaran

    2013-04-01

    Full Text Available Four wave mixing generally occurs when two or more different wavelengths from two or more sources are launched into the fibre, resulting in a new wavelength known as idler (different from thegiven wavelengths. Here in this paper the efficiency of the generation of idler and the power of idler will be numerically simulated for two wave fibre transmissions. From this simulation, a curve will be obtained between power of idler and wavelength separation between signal and pump source, which will be used topropose a power independent method for extraction of dispersion parameters of a fibre.

  19. Optimization Design of Double-parameter Shift Schedule of Tracked Vehicle with Hydrodynamic-mechanical Transmission%Optimization Design of Double-parameter Shift Schedule of Tracked Vehicle with Hydrodynamic-mechanical Transmission

    Institute of Scientific and Technical Information of China (English)

    武景燕; 魏巍; 曲婧瑶; 闫清东

    2011-01-01

    A kind of automatic shift schedule optimization method is provided for a tracked vehicle with hydrodynamic-mechanical transmission in order to improve its dynamic performance. A dynamic model of integrated hydrodynamic-mechanical transmission is built in MATLAB/Simdriveline environment, and an optimum shift schedule is derived by using iSight software to call the dynamic model above, then the shift schedule is achieved after optimization. The simulation results show that the method is significant to improve the dynamic performance and gear-shifting smoothness theoretically and practically.

  20. Adaptive Control Parameters for Dispersal of Multi-Agent Mobile Ad Hoc Network (MANET) Swarms

    Energy Technology Data Exchange (ETDEWEB)

    Kurt Derr; Milos Manic

    2013-11-01

    A mobile ad hoc network is a collection of independent nodes that communicate wirelessly with one another. This paper investigates nodes that are swarm robots with communications and sensing capabilities. Each robot in the swarm may operate in a distributed and decentralized manner to achieve some goal. This paper presents a novel approach to dynamically adapting control parameters to achieve mesh configuration stability. The presented approach to robot interaction is based on spring force laws (attraction and repulsion laws) to create near-optimal mesh like configurations. In prior work, we presented the extended virtual spring mesh (EVSM) algorithm for the dispersion of robot swarms. This paper extends the EVSM framework by providing the first known study on the effects of adaptive versus static control parameters on robot swarm stability. The EVSM algorithm provides the following novelties: 1) improved performance with adaptive control parameters and 2) accelerated convergence with high formation effectiveness. Simulation results show that 120 robots reach convergence using adaptive control parameters more than twice as fast as with static control parameters in a multiple obstacle environment.

  1. Parameters effect on heterogeneous photocatalysed degradation of phenol in aqueous dispersion of TiO2

    Institute of Scientific and Technical Information of China (English)

    KASHIF Naeem; OUYANG Feng

    2009-01-01

    In this study, photocatalytic degradation of phenol selected as model compound of organic pollutant had been investigated in aqueous titanium dioxide (TiO2) dispersion under UV irradiation. The effects of various parameters such as pH, catalyst concentration, phenol concentration, anions, metal ions, electron acceptors, and surfactants on the photocatalytic degradation of phenol were investigated. The degradation kinetics was determined by the change in phenol concentration employing UV-Vis spectrometry as a function of irradiation time. The degradation kinetics of phenol follows pseudo first-order kinetics. The results showed a significant dependence of the photocatalytic degradation of phenol on the functional parameters. The probable promising roles of the additives on the degradation process were discussed.

  2. Influence of preparation conditions on the dispersion parameters of sprayed iron oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Akl, Alaa A., E-mail: alaaakl@link.net [Physics Department, Faculty of Science, El-Minia University, El-Minia 111955 (Egypt)

    2010-10-01

    Iron oxide thin films were prepared by spray pyrolysis technique (SPT) at various substrate temperatures (T{sub sub}) and different deposition time. X-ray diffraction (XRD) analysis showed that, at T{sub sub} {>=} 350 deg. C, a single phase of {alpha}-Fe{sub 2}O{sub 3} film is formed which has the rhombohedral structure. Moreover, the crystallinity was improved by increasing T{sub sub}. The effect of T{sub sub} as well as deposition time on the optical dispersion of these films has been investigated. The optical transmittance and reflectance measurements were performed by using spectrophotometer in the wavelength range from 300 to 2500 nm. The refractive index was determined by using Murmann's exact equation. It was observed that, the refractive index increased with increasing in both the T{sub sub} and film thickness. The optical dispersion parameters have been evaluated and analyzed by using Wemple-Didomenico equation. The obtained results showed that, the dielectric properties have weak dependencies of growth temperature and film thickness. At T{sub sub} {>=} 350 deg. C, the average values of oscillator energy, E{sub o} and dispersion energy, E{sub d} were found to be 5.96 and 34.08 eV. While at different thickness, the average values of dispersion energies were found to be 3.93 and 17.08 eV. Also, the average values of oscillator strength S{sub o} and single resonant frequency {omega}{sub o} were estimated 10.78 x 10{sup 13} m{sup -2} and 5.99 x 10{sup 15} Hz, while at different thickness were evaluating 4.81 x 10{sup 13} m{sup -2} and 6.11 x 10{sup 15} Hz. Furthermore, the optical parameters such as wavelength of single oscillator {lambda}{sub o}, plasma frequency {omega}{sub p}, and dielectric constant {epsilon} have been evaluated. The carrier concentration N{sub opt} by using Drud's theory was obtained the range of 5.07 x 10{sup 25} m{sup -3} to 1.04 x 10{sup 26} m{sup -3}.

  3. Computation of probabilistic hazard maps and source parameter estimation for volcanic ash transport and dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Madankan, R. [Department of Mechanical and Aerospace Engineering, University at Buffalo (United States); Pouget, S. [Department of Geology, University at Buffalo (United States); Singla, P., E-mail: psingla@buffalo.edu [Department of Mechanical and Aerospace Engineering, University at Buffalo (United States); Bursik, M. [Department of Geology, University at Buffalo (United States); Dehn, J. [Geophysical Institute, University of Alaska, Fairbanks (United States); Jones, M. [Center for Computational Research, University at Buffalo (United States); Patra, A. [Department of Mechanical and Aerospace Engineering, University at Buffalo (United States); Pavolonis, M. [NOAA-NESDIS, Center for Satellite Applications and Research (United States); Pitman, E.B. [Department of Mathematics, University at Buffalo (United States); Singh, T. [Department of Mechanical and Aerospace Engineering, University at Buffalo (United States); Webley, P. [Geophysical Institute, University of Alaska, Fairbanks (United States)

    2014-08-15

    Volcanic ash advisory centers are charged with forecasting the movement of volcanic ash plumes, for aviation, health and safety preparation. Deterministic mathematical equations model the advection and dispersion of these plumes. However initial plume conditions – height, profile of particle location, volcanic vent parameters – are known only approximately at best, and other features of the governing system such as the windfield are stochastic. These uncertainties make forecasting plume motion difficult. As a result of these uncertainties, ash advisories based on a deterministic approach tend to be conservative, and many times over/under estimate the extent of a plume. This paper presents an end-to-end framework for generating a probabilistic approach to ash plume forecasting. This framework uses an ensemble of solutions, guided by Conjugate Unscented Transform (CUT) method for evaluating expectation integrals. This ensemble is used to construct a polynomial chaos expansion that can be sampled cheaply, to provide a probabilistic model forecast. The CUT method is then combined with a minimum variance condition, to provide a full posterior pdf of the uncertain source parameters, based on observed satellite imagery. The April 2010 eruption of the Eyjafjallajökull volcano in Iceland is employed as a test example. The puff advection/dispersion model is used to hindcast the motion of the ash plume through time, concentrating on the period 14–16 April 2010. Variability in the height and particle loading of that eruption is introduced through a volcano column model called bent. Output uncertainty due to the assumed uncertain input parameter probability distributions, and a probabilistic spatial-temporal estimate of ash presence are computed.

  4. Changes of hydrodynamic parameters on mountain stream bed within the block ramp influence and possibility of their use for integrated river management

    Science.gov (United States)

    Radecki-Pawlik, Artur; Plesiński, Karol

    2016-04-01

    In modern river management practices and philosophy one can notice coming more into use ecological friendly hydraulic structures. Those, which are especially needed for river training works, as far as expectation of Water Framework Directive is concerned, are block ramps which are hydraulic structures working similar to riffles known very well from fluvial geomorphology studies and are natural features in streams and rivers. What is important well designed block ramps do not stop fish and invertebrates against migrating, provide natural and esthetical view being built within the river channel, still working as hydraulic engineering structures and might be used in river management in different river ecosystems. The main aim of the research was to describe changes of values of hydrodynamics parameters upstream and downstream of the block ramps and to find out their influence on hydrodynamics of the stream. The study was undertaken on the Porębianka River in the Gorce Mountains, Polish Carpathians. Observed hydrodynamic parameters within the reach of the block ramps depend on the location of measuring point and the influence of individual part of the structure. We concluded that: 1. Hydrodynamic parameters close to block ramps depend on the location of the measurement points in relation to particular elements of the structure; 2. The highest value of velocities don't cause the highest force values, which acting on the bed of the watercourse, because they are rather related to the water level of the channel; 3. The values of mean velocities, shear velocities and shear stresses were similar upstream and downstream the block ramps, which means that the structures stabilize the river bed. This study was performed within the scope of the Science Activity money from Ministry of High Education and Young Scientist's Activity Money of Department of Hydraulics Engineering and Geotechnique, University of Agriculture, Cracow, Poland

  5. Dry powder inhalers: study of the parameters influencing adhesion and dispersion of fluticasone propionate.

    Science.gov (United States)

    Le, V N P; Hoang Thi, T H; Robins, E; Flament, M P

    2012-06-01

    Interactions between particles are dependent on the physicochemical characteristics of the interacting particles but it is also important to consider the manufacturing process. Blending active pharmaceutical ingredient (API) with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend. The aim of this work was to study parameters that influence the interactions between API and carrier in adhesive mixtures used in DPI and their effect on API dispersion. The study was done with fluticasone propionate blended with lactose 'Lactohale 200'. The study was based on the influence of the operating conditions (speed, mixing time, resting steps during mixing), the size of the carrier and the storage conditions on the blend properties and on the API dispersion. The quality of the blends was examined by analysing the API content uniformity. Adhesion characteristics were evaluated by submitting mixtures to a sieving action by air depression with the Alpine air-jet sieve. Aerodynamic evaluation of fine particle fraction (FPF) was obtained using a Twin Stage Impinger; the FPF being defined as the mass percentage of API below 6.4 μm. For good dispersion and therefore good homogeneity of the API in the carrier particles, speed and powder blending time have to be sufficient, but not too long to prevent the appearance of static electricity, which is not favourable to homogeneity and stability. The FPF increases with the decrease in the carrier size. The storage conditions have also to be taken into consideration. Higher humidity favours the adhesion of API on the carrier and decreases the FPF.

  6. Calibration of the Many-Body Dispersion Range-Separation Parameter

    CERN Document Server

    Markovich, Thomas; Rappoport, Dmitrij; Kim, Dasol; Aspuru-Guzik, Alán

    2016-01-01

    Recent work has shown that a fully many-body treatment of noncovalent interactions, such as that given by the method of many-body dispersion (MBD), is vital to accurately modeling the structure and energetics of many molecular systems with density functional theory (DFT). To avoid double counting the correlation contributions of DFT and the MBD correction, a single-parameter range-separation scheme is typically employed. Coupling the MBD correction to a given exchange-correlation functional therefore requires calibrating the range-separation parameter. We perform this calibration for 24 popular DFT functionals by optimizing against the S66x8 benchmark set. Additionally, we report a linear equation that predicts near optimal range-separation parameters, dependent only on the class of the exchange functional and the value of the gradient enhancement factor. When a calibrated MBD correction is employed, most of the exchange-correlation functionals considered are capable of achieving agreement with CCSD(T)/CBS in...

  7. Determination of Groundwater Velocity and Dispersion Parameters by Borehole Wall Multielectrode Geoelectrics

    Science.gov (United States)

    Kessels, W.; Wuttke, M. W.

    2007-05-01

    A single well technique to determine groundwater flow values and transport parameters is presented. Multielectrode arrays are placed at the filtered casing depth by an inflatable packer or are installed on the borehole wall behind the casing.Tracer water with a higher or lower specific electrical conductivity (salinity) which is injected between the electrodes. This tracer plume then moves into the natural groundwater flow field. The observation of this movement by geoelectric logging enables the determination of the groundwater velocity and salinity. The transport parameters "effective porosity" and "dispersion length" can also be derived. The geoelectric logging uses n borehole electrodes and two grounding electrodes. Thus, either n independent two point measurements or n*(n-1)/2 pole-to-pole measurements can be conducted to obtain a full set of geoelectric measurements. This set is used to derive all electrode combinations by applying the law of superposition and reciprocity. The tracer distribution around the borehole during and after injection depends on the hydraulic and transport parameters of the aquifer and the filter sand. The transport parameter "porosity" plus the total injected tracer volume determines the tracer distribution around the borehole. The transport parameter "dispersivity" determines the abruptness of the tracer front. The method was tested by undertaking measurements in a lab aquifer filled with sand. The results are discussed and the limitations of the method are shown. Multielectrode installations behind casing were tested in situ in the two scientific boreholes CAT-LUD-1 and CAT- LUD-1A drilled in the northern part of Germany. A multielectrode packer system was designed, built and tested in these boreholes. The results are compared with colloid observations in the borehole and hydraulic triangulation in surrounded observation wells. Here, the interpretation of these in situ measurements is mainly restricted to two point geoelectric

  8. Comparative study on dispersion and interfacial properties of single walled carbon nanotube/polymer composites using Hansen solubility parameters.

    Science.gov (United States)

    Ma, Jing; Larsen, Raino Mikael

    2013-02-01

    Dispersion and interfacial strain transfer of single walled carbon nanotubes (SWNTs) are two major challenges for the utilization of SWNTs as reinforcements in polymer composites. Surface modifications could help change the dispersion and interfacial properties. In this study, nanocomposites were fabricated by solution blending 1 wt % SWNTs with various modification (nonmodified, nitric acid functionalized, and amine functionalized SWNTs) and three kinds of polymeric materials (polycarbonate, polyvinylidene fluoride, and epoxy). Chemical compatibilities between SWNTs and solvents or polymers are calculated by the Hansen solubility parameters (HSP) method. The dispersion of the SWNTs in solvents is evaluated by dynamic light scattering. The dispersion of SWNTs in polymers evaluated by a light optical microscope (LOM) generally agrees with the HSP prediction. The strain transfer from the matrix to SWNTs is mainly related to the dispersion, the bundle size, the residual thermal stresses on the sample, and, to lesser degree, the HSP.

  9. Extracting Host Galaxy Dispersion Measure and Constraining Cosmological Parameters using Fast Radio Burst Data

    Science.gov (United States)

    Yang, Yuan-Pei; Zhang, Bing

    2016-10-01

    The excessive dispersion measures (DMs) and high Galactic latitudes of fast radio bursts (FRBs) hint toward a cosmological origin of these mysterious transients. Methods of using measured DM and redshift z to study cosmology have been proposed, but one needs to assume a certain amount of DM contribution from the host galaxy ({{DM}}{HG}) in order to apply those methods. We introduce a slope parameter β (z)\\equiv d{ln} /d{ln}z (where {{DM}}{{E}} is the observed DM subtracting the Galactic contribution), which can be directly measured when a sample of FRBs have z measured. We show that can be roughly inferred from β and the mean values, \\overline{ } and \\bar{z}, of the sample. Through Monte Carlo simulations, we show that the mean value of local host galaxy DM, , along with other cosmological parameters (mass density {{{Ω }}}m in the ΛCDM model, and the IGM portion of the baryon energy density {{{Ω }}}b{f}{IGM}), can be independently measured through Markov Chain Monte Carlo fitting to the data.

  10. Inverse estimation of source parameters of oceanic radioactivity dispersion models associated with the Fukushima accident

    Directory of Open Access Journals (Sweden)

    Y. Miyazawa

    2013-04-01

    Full Text Available With combined use of the ocean–atmosphere simulation models and field observation data, we evaluate the parameters associated with the total caesium-137 amounts of the direct release into the ocean and atmospheric deposition over the western North Pacific caused by the accident of Fukushima Daiichi nuclear power plant (FNPP that occurred in March 2011. The Green's function approach is adopted for the estimation of two parameters determining the total emission amounts for the period from 12 March to 6 May 2011. It is confirmed that the validity of the estimation depends on the simulation skill near FNPP. The total amount of the direct release is estimated as 5.5–5.9 × 1015 Bq, while that of the atmospheric deposition is estimated as 5.5–9.7 × 1015 Bq, which indicates broader range of the estimate than that of the direct release owing to uncertainty of the dispersion widely spread over the western North Pacific.

  11. Inverse estimation of source parameters of oceanic radioactivity dispersion models associated with the Fukushima accident

    Directory of Open Access Journals (Sweden)

    Y. Miyazawa

    2012-10-01

    Full Text Available With combined use of the ocean-atmosphere simulation models and field observation data, we evaluate the parameters associated with the total caesium-137 amounts of the direct release into the ocean and atmospheric deposition over the Western North Pacific caused by the accident of Fukushima Daiichi nuclear power plant (FNPP that occurred in March 2011. The Green's function approach is adopted for the estimation of two parameters determining the total emission amounts for the period from 12 March to 6 May 2011. It is confirmed that the validity of the estimation depends on the simulation skill near FNPP. The total amount of the direct release is estimated as 5.5–5.9 × 1015 Bq, while that of the atmospheric deposition is estimated as 5.5–9.7 × 1015 Bq, which indicates broader range of the estimate than that of the direct release owing to uncertainty of the dispersion widely spread over the Western North Pacific.

  12. Extracting host galaxy dispersion measure and constraining cosmological parameters using fast radio burst data

    CERN Document Server

    Yang, Yuan-Pei

    2016-01-01

    The excessive dispersion measures (DMs) and high Galactic latitudes of fast radio bursts (FRBs) hint toward a cosmological origin of these mysterious transients. Methods of using measured DM and redshift $z$ to study cosmology have been proposed, but one needs to assume a certain amount of DM contribution from the host galaxy (DM$_{\\rm HG}$) in order to apply those methods. We introduce a slope parameter $\\beta(z) \\equiv d \\ln \\left / d \\ln z$ (where DM$_{\\rm E}$ is the observed DM subtracting the Galactic contribution), which can be directly measured when a sample of FRBs have $z$ measured. We show that $\\left$ can be roughly inferred from $\\beta$ and the mean values, $\\overline{\\rm \\left}$ and $\\bar z$, of the sample. Through Monte Carlo simulations, we show that the mean value of local host galaxy DM, $\\left$, along with other cosmological parameters (mass density $\\Omega_m$ in the $\\Lambda$CDM model, and the IGM portion of the baryon energy density $\\Omega_b f_{\\rm IGM}$) can be independently measured thr...

  13. Numerical simulation of groundwater level in a fractured porous medium and sensitivity analysis of the hydrodynamic parameters using grid computing: application of the plain of Gondo (Burkina Faso

    Directory of Open Access Journals (Sweden)

    Wenddabo Olivier Sawadogo

    2012-01-01

    Full Text Available The use of mathematical modeling as a tool for decision support is not common in Africa in solving development problems. In this article we talk about the numerical simulation of groundwater level of the plain of Gondo (Burkina Faso and the sensitivity analysis of the hydrodynamic parameters. The domain has fractures which have hydraulic coefficients lower than those of the rock. Our contribution is to bring brief replies to the real problem posed in the thesis of Mr. KOUSSOUBE [1]. Namely that what causes the appearance of the piezometric level observed and impact of surface water on the piezometry. The mathematical model of the flow was solved by programming the finite element method on FreeFem++[2]. A local refinement of the mesh at fracture was used. We then conduct a sensitivity analysis to see which hydrodynamic parameters influences much of the solution. The method used for the sensitivity analysis is based on the calculation of the gradient by the adjoint equation and requires great computational power. To remedy this, we used a technique of distributed computing and we launched our application to the Moroccan grid (magrid. This allowed us to reduce the computation time. The results allowed to highlight the role of fractures and contributions of surface water on the evolution of the piezometric level of the plain of Gondo and identified the parameters that greatly influence the piezometric level.

  14. Numerical assessment of the dispersion of overspilled sediment from a dredge barge and its sensitivity to various parameters.

    Science.gov (United States)

    Mestres, Marc; Sierra, Joan Pau; Mösso, César; Sánchez-Arcilla, Agustín; Hernáez, Mario; Morales, Jorge

    2014-02-15

    Marine dredging operations are not uncommon in coastal waters since they are necessary for several beneficial uses, such as harbour maintenance, beach nourishment or removal/capping of pollutants, amongst others. They also constitute a significant risk for the environment, changing its physical, chemical and biological characteristics, as evidenced by many authors. In this study, two numerical models are used to simulate the dispersion pattern of fine suspended sediment spilled from a dredge barge, considering different hydrodynamic scenarios, particle sizes and dredging tracks in a mesotidal environment. The results show that, in this particular case, the currents (largely induced by the tide) are the main responsible for the final disposition of the settled particles, being the other variables of secondary importance.

  15. Influence of operating parameters on electrocoagulation of C.I. disperse yellow 3

    Directory of Open Access Journals (Sweden)

    Djamel Ghernaout

    2014-12-01

    Full Text Available This work deals with the electrocoagulation (EC process for an organic dye removal. The chosen organic dye is C.I. disperse yellow 3 (DY which is used in textile industry. Experiments were performed in batch mode using Al electrodes and for comparison purposes Fe electrodes. The experimental set-up was composed of 1 L beaker, two identical electrodes which are separated 2 cm from each other. The main operating parameters influencing EC process were examined such as pH, supporting electrolyte concentration CNaCl, current density i, and DY concentration. High performance EC process was shown during 45 min for 200 mg/L dye concentration at i = 350 A m-2 (applied voltage 12 V and CNaCl = 1 g L-1 reaching 98 % for pHs 3 and 10 and 99 % for pH 6. After 10 min, DY was also efficiently removed (86 % showing that EC process may be conveniently applied for textile industry wastewater treatment. EC using Fe electrodes exhibited slightly lower performance comparing EC using Al electrodes.

  16. CSF monoamine metabolites, cholinesterases and lactate in the adult hydrocephalus syndrome (normal pressure hydrocephalus) related to CSF hydrodynamic parameters.

    Science.gov (United States)

    Malm, J; Kristensen, B; Ekstedt, J; Adolfsson, R; Wester, P

    1991-03-01

    Monoamine metabolites, cholinesterases and lactic acid in lumbar cerebrospinal fluid (CSF) were investigated on patients with the adult hydrocephalus syndrome (idiopathic normal pressure syndrome; AHS, n = 15), Alzheimer's disease (AD, n = 14), multi-infarct dementia (MID, n = 13) and controls (n = 21). Patients had clinical and CSF hydrodynamic investigations. Monoamine concentrations were determined by reversed-phase liquid chromatography, cholinesterases and lactate were determined photometrically. In the AHS patients, CSF monoamine concentrations were not significantly different compared with controls, AD or MID patients. AHS and AD patients showed a similar reduction of CSF acetylcholinesterase activity compared with controls. Positive correlations were found in concentrations of CSF homovanillic acid, CSF 5-hydroxyindoleacetic acid and CSF lactic acid versus CSF outflow conductance (that is, resistance against CSF outflow) in the AHS patients. A similar pattern was observed in a subgroup of MID patients characterised by dilated ventricles and disturbed CSF hydrodynamics. These data suggest that a low CSF outflow conductance may facilitate the clearance of acidic substances from the arachnoid space at the probenecid sensitive active transport site. Alternative explanations would be that a pathologically low CSF outflow conductance is accompanied by an inverse caudorostral flow of CSF or a compromised trans-ependymal diffusion.

  17. Comparative Study on Dispersion and Interfacial Properties of Single Walled Carbon Nanotube/Polymer Composites Using Hansen Solubility Parameters

    DEFF Research Database (Denmark)

    Ma, Jing; Larsen, Mikael

    2013-01-01

    Dispersion and interfacial strain transfer of single walled carbon nanotubes (SWNTs) are two major challenges for the utilization of SWNTs as reinforcements in polymer composites. Surface modifications could help change the dispersion and interfacial properties. In this study, nanocomposites were...... fabricated by solution blending 1 wt % SWNTs with various modification (nonmodified, nitric acid functionalized, and amine functionalized SWNTs) and three kinds of polymeric materials (polycarbonate, polyvinylidene fluoride, and epoxy). Chemical compatibilities between SWNTs and solvents or polymers...... are calculated by the Hansen solubility parameters (HSP) method. The dispersion of the SWNTs in solvents is evaluated by dynamic light scattering. The dispersion of SWNTs in polymers evaluated by a light optical microscope (LOM) generally agrees with the HSP prediction. The strain transfer from the matrix...

  18. Hyperbolic metamaterial lens with hydrodynamic nonlocal response

    DEFF Research Database (Denmark)

    Yan, Wei; Mortensen, N. Asger; Wubs, Martijn

    2013-01-01

    in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we......We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves...... of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens...

  19. Hyperbolic metamaterial lens with hydrodynamic nonlocal response.

    Science.gov (United States)

    Yan, Wei; Mortensen, N Asger; Wubs, Martijn

    2013-06-17

    We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens.

  20. Optimising Drug Solubilisation in Amorphous Polymer Dispersions: Rational Selection of Hot-melt Extrusion Processing Parameters.

    Science.gov (United States)

    Li, Shu; Tian, Yiwei; Jones, David S; Andrews, Gavin P

    2016-02-01

    The aim of this article was to construct a T-ϕ phase diagram for a model drug (FD) and amorphous polymer (Eudragit® EPO) and to use this information to understand the impact of how temperature-composition coordinates influenced the final properties of the extrudate. Defining process boundaries and understanding drug solubility in polymeric carriers is of utmost importance and will help in the successful manufacture of new delivery platforms for BCS class II drugs. Physically mixed felodipine (FD)-Eudragit(®) EPO (EPO) binary mixtures with pre-determined weight fractions were analysed using DSC to measure the endset of melting and glass transition temperature. Extrudates of 10 wt% FD-EPO were processed using temperatures (110°C, 126°C, 140°C and 150°C) selected from the temperature-composition (T-ϕ) phase diagrams and processing screw speed of 20, 100 and 200rpm. Extrudates were characterised using powder X-ray diffraction (PXRD), optical, polarised light and Raman microscopy. To ensure formation of a binary amorphous drug dispersion (ADD) at a specific composition, HME processing temperatures should at least be equal to, or exceed, the corresponding temperature value on the liquid-solid curve in a F-H T-ϕ phase diagram. If extruded between the spinodal and liquid-solid curve, the lack of thermodynamic forces to attain complete drug amorphisation may be compensated for through the use of an increased screw speed. Constructing F-H T-ϕ phase diagrams are valuable not only in the understanding drug-polymer miscibility behaviour but also in rationalising the selection of important processing parameters for HME to ensure miscibility of drug and polymer.

  1. Evaluation of transverse dispersion effects in tank experiments by numerical modeling: parameter estimation, sensitivity analysis and revision of experimental design.

    Science.gov (United States)

    Ballarini, E; Bauer, S; Eberhardt, C; Beyer, C

    2012-06-01

    Transverse dispersion represents an important mixing process for transport of contaminants in groundwater and constitutes an essential prerequisite for geochemical and biodegradation reactions. Within this context, this work describes the detailed numerical simulation of highly controlled laboratory experiments using uranine, bromide and oxygen depleted water as conservative tracers for the quantification of transverse mixing in porous media. Synthetic numerical experiments reproducing an existing laboratory experimental set-up of quasi two-dimensional flow through tank were performed to assess the applicability of an analytical solution of the 2D advection-dispersion equation for the estimation of transverse dispersivity as fitting parameter. The fitted dispersivities were compared to the "true" values introduced in the numerical simulations and the associated error could be precisely estimated. A sensitivity analysis was performed on the experimental set-up in order to evaluate the sensitivities of the measurements taken at the tank experiment on the individual hydraulic and transport parameters. From the results, an improved experimental set-up as well as a numerical evaluation procedure could be developed, which allow for a precise and reliable determination of dispersivities. The improved tank set-up was used for new laboratory experiments, performed at advective velocities of 4.9 m d(-1) and 10.5 m d(-1). Numerical evaluation of these experiments yielded a unique and reliable parameter set, which closely fits the measured tracer concentration data. For the porous medium with a grain size of 0.25-0.30 mm, the fitted longitudinal and transverse dispersivities were 3.49×10(-4) m and 1.48×10(-5) m, respectively. The procedures developed in this paper for the synthetic and rigorous design and evaluation of the experiments can be generalized and transferred to comparable applications.

  2. A Two-Stage Algorithm for Origin-Destination Matrices Estimation Considering Dynamic Dispersion Parameter for Route Choice.

    Directory of Open Access Journals (Sweden)

    Yong Wang

    Full Text Available This paper proposes a two-stage algorithm to simultaneously estimate origin-destination (OD matrix, link choice proportion, and dispersion parameter using partial traffic counts in a congested network. A non-linear optimization model is developed which incorporates a dynamic dispersion parameter, followed by a two-stage algorithm in which Generalized Least Squares (GLS estimation and a Stochastic User Equilibrium (SUE assignment model are iteratively applied until the convergence is reached. To evaluate the performance of the algorithm, the proposed approach is implemented in a hypothetical network using input data with high error, and tested under a range of variation coefficients. The root mean squared error (RMSE of the estimated OD demand and link flows are used to evaluate the model estimation results. The results indicate that the estimated dispersion parameter theta is insensitive to the choice of variation coefficients. The proposed approach is shown to outperform two established OD estimation methods and produce parameter estimates that are close to the ground truth. In addition, the proposed approach is applied to an empirical network in Seattle, WA to validate the robustness and practicality of this methodology. In summary, this study proposes and evaluates an innovative computational approach to accurately estimate OD matrices using link-level traffic flow data, and provides useful insight for optimal parameter selection in modeling travelers' route choice behavior.

  3. Caracterização hidrodinâmica e hidrodispersiva de um latossolo amarelo na microrregião do brejo paraibano Hydrodynamic and hydrodispersive parameters of an oxisol in the wetland region of Paraíba

    Directory of Open Access Journals (Sweden)

    André Maciel Netto

    2013-02-01

    hydrodispersive parameters of some soils in a marshy region, in Areia-PB, in the field, based on single-ring infiltration tests. The experiments were conducted in an area with common bean, in a 50 x 50 m grid. Saturated hydraulic conductivity (Ks and sorptivity (S were estimated by analysis of three- dimensional axisymmetric infiltration for short and long periods. The inert solute (Cl- was used to calculate the mobile water fraction Φ, by measuring solute concentration in the 0-15 cm layer at the end of the infiltration experiment. A numerical model of solute transfer based on the concept of convection-dispersion (CD was used to determine the transport parameters (D and R. Single-ring infiltrometry proved to be a simple and efficient method to obtain the hydrodynamic and hydrodispersive parameters. A good agreement was observed between measured and calculated values (v, D and R with the model CD, based on the coefficients of determination (r².

  4. Influence of laser design parameters on the hydrodynamics of microfusion plasmas; Influencia de los parametros basicos del laser sobre la hidrodinamica de plasmas para microfusion

    Energy Technology Data Exchange (ETDEWEB)

    Sanmartin, J. A.; Barrero, A.

    1976-07-01

    The quasi neutral, one dimensional motion generated in a cold, infinite, uniform plasma of density n{sub 0}, by the absorption, In a given plane, of a linear pulse of energy per unit time and area {phi} - {phi}{sub 0}t/{tau}, 0< t {<=} {tau}, is considered; the analysis allows for thermal conduction and viscosity of ions and electrons, their energy exchange, and an electron thermal flux limiter. The motion is found to be self similar and governed by single non dimensional parameter {alpha} similar{sub t}o(n{sup 2}{sub 0} {tau}/{phi}{sub 0}){sup 2}/3. Detailed asymptotic results are obtained for both {alpha}<<1and {alpha}>>1; the general (behaviour of the solution for arbitrary {alpha} is discussed. The analysis can be easily extended to the case of a plasma initially occupying a half-space, and throws light on the hydrodynamics of laser fusion plasmas. (Author) 51 refs.

  5. Analysis of a Kalman filter based method for on-line estimation of atmospheric dispersion parameters using radiation monitoring data

    DEFF Research Database (Denmark)

    Drews, Martin; Lauritzen, Bent; Madsen, Henrik

    2005-01-01

    A Kalman filter method is discussed for on-line estimation of radioactive release and atmospheric dispersion from a time series of off-site radiation monitoring data. The method is based on a state space approach, where a stochastic system equation describes the dynamics of the plume model...... parameters, and the observables are linked to the state variables through a static measurement equation. The method is analysed for three simple state space models using experimental data obtained at a nuclear research reactor. Compared to direct measurements of the atmospheric dispersion, the Kalman filter...... estimates are found to agree well with the measured parameters, provided that the radiation measurements are spread out in the cross-wind direction. For less optimal detector placement it proves difficult to distinguish variations in the source term and plume height; yet the Kalman filter yields consistent...

  6. Non-Parabolic Hydrodynamic Formulations for the Simulation of Inhomogeneous Semiconductor Devices

    Science.gov (United States)

    Smith, A. W.; Brennan, K. F.

    1996-01-01

    Hydrodynamic models are becoming prevalent design tools for small scale devices and other devices in which high energy effects can dominate transport. Most current hydrodynamic models use a parabolic band approximation to obtain fairly simple conservation equations. Interest in accounting for band structure effects in hydrodynamic device simulation has begun to grow since parabolic models cannot fully describe the transport in state of the art devices due to the distribution populating non-parabolic states within the band. This paper presents two different non-parabolic formulations or the hydrodynamic model suitable for the simulation of inhomogeneous semiconductor devices. The first formulation uses the Kane dispersion relationship ((hk)(exp 2)/2m = W(1 + alphaW). The second formulation makes use of a power law ((hk)(exp 2)/2m = xW(exp y)) for the dispersion relation. Hydrodynamic models which use the first formulation rely on the binomial expansion to obtain moment equations with closed form coefficients. This limits the energy range over which the model is valid. The power law formulation readily produces closed form coefficients similar to those obtained using the parabolic band approximation. However, the fitting parameters (x,y) are only valid over a limited energy range. The physical significance of the band non-parabolicity is discussed as well as the advantages/disadvantages and approximations of the two non-parabolic models. A companion paper describes device simulations based on the three dispersion relationships; parabolic, Kane dispersion and power law dispersion.

  7. Non-Parabolic Hydrodynamic Formulations for the Simulation of Inhomogeneous Semiconductor Devices

    Science.gov (United States)

    Smith, A. W.; Brennan, K. F.

    1996-01-01

    Hydrodynamic models are becoming prevalent design tools for small scale devices and other devices in which high energy effects can dominate transport. Most current hydrodynamic models use a parabolic band approximation to obtain fairly simple conservation equations. Interest in accounting for band structure effects in hydrodynamic device simulation has begun to grow since parabolic models cannot fully describe the transport in state of the art devices due to the distribution populating non-parabolic states within the band. This paper presents two different non-parabolic formulations or the hydrodynamic model suitable for the simulation of inhomogeneous semiconductor devices. The first formulation uses the Kane dispersion relationship ((hk)(exp 2)/2m = W(1 + alphaW). The second formulation makes use of a power law ((hk)(exp 2)/2m = xW(exp y)) for the dispersion relation. Hydrodynamic models which use the first formulation rely on the binomial expansion to obtain moment equations with closed form coefficients. This limits the energy range over which the model is valid. The power law formulation readily produces closed form coefficients similar to those obtained using the parabolic band approximation. However, the fitting parameters (x,y) are only valid over a limited energy range. The physical significance of the band non-parabolicity is discussed as well as the advantages/disadvantages and approximations of the two non-parabolic models. A companion paper describes device simulations based on the three dispersion relationships; parabolic, Kane dispersion and power law dispersion.

  8. Kinetics and Hydrodynamics of Silver Ion Flotation

    OpenAIRE

    2012-01-01

    This paper studies and determines the dispersion properties (Jg, Eg and Db), kinetics parameters and hydrodynamics of the process and its effect on the recovery of silver contained in spent diluted fixers by techniques of ion flotation in columns. The experimental results show silver recoveries of 97 % using sodium isopropyl xanthate (SIX) 0.06 g·L-1 and 0.04 g·L-1 of frother, at a Jg of 1.0 cm·s-1 and Jl of 0.72 cm·s-1. Xanthate-promoter combinations do not improve the separation; however, r...

  9. Analysis of a Kalman filter based method for on-line estimation of atmospheric dispersion parameters using radiation monitoring data

    DEFF Research Database (Denmark)

    Drews, Martin; Lauritzen, Bent; Madsen, Henrik

    2005-01-01

    parameters, and the observables are linked to the state variables through a static measurement equation. The method is analysed for three simple state space models using experimental data obtained at a nuclear research reactor. Compared to direct measurements of the atmospheric dispersion, the Kalman filter...... estimates are found to agree well with the measured parameters, provided that the radiation measurements are spread out in the cross-wind direction. For less optimal detector placement it proves difficult to distinguish variations in the source term and plume height; yet the Kalman filter yields consistent...... scheme are outlined, to account for realistic accident scenarios....

  10. Tuning the physical parameters towards optimal polymer-wrapped single-walled carbon nanotubes dispersions

    NARCIS (Netherlands)

    Gao, J.; Annema, R.; Loi, M. A.

    2012-01-01

    Solubilization of single-walled carbon nanotubes (SWNTs) has been essential for the understanding of their physical properties. Ultrasonication followed by centrifugation has been generally used for the preparation of SWNT dispersion in presence of different surfactants or conjugated polymers. Howev

  11. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    CERN Document Server

    Andreev, Pavel A

    2014-01-01

    We discuss complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider contribution of the annihilation interaction in the quantum hydrodynamic equations and in spectrum of waves in magnetized electron-positron plasmas. We consider propagation of waves parallel and perpendicular to an external magnetic field. We also consider oblique propagation of longitudinal waves. We derive set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory for the linear wave behavior in absence of external fields. We calculate contribution of the Darwin...

  12. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Directory of Open Access Journals (Sweden)

    Juan C. Torres

    2014-05-01

    Full Text Available A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed.

  13. Dispersal of key subplinian-Plinian tephras from Hekla volcano, Iceland: implications for eruption source parameters

    Science.gov (United States)

    Janebo, Maria H.; Thordarson, Thorvaldur; Houghton, Bruce F.; Bonadonna, Costanza; Larsen, Gudrun; Carey, Rebecca J.

    2016-10-01

    Hekla is the most active silicic volcano in Iceland, with 18 subplinian-Plinian eruptions since AD 1104. In the period 1970 to 2000, the frequency of such eruptions increased to once every decade. Hekla is currently inflated to above the levels observed prior to the most recent eruptions in 1991 and 2000. The next eruption could pose a hazard to air traffic between North America and Europe because explosive eruptions of Hekla, independent of size, typically start with a subplinian or Plinian phase that produces a sustained ash plume. We present an overview of five of the largest historical Hekla eruptions (taking place in 1104, 1158, 1300, 1693, and 1766). These eruptions cover a compositional range of rhyolite to andesite, previously estimated Volcanic Explosivity Index (VEI) values of 4-5 and are characterised by contrasting wind dispersal (dispersal axes NW-NE). New isopach maps show both greater deposit thicknesses in the proximal region and wider dispersal than previously inferred, resulting in different volume estimates (minimal values ranging between 0.18 and 0.91 km3). New isopleth maps were also compiled and resulted in inferred plume heights of about 13-25 km. These changes in the estimated values of volume and mass eruption rates have large implications on the forecasting and impacts of future Hekla eruptions.

  14. Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Deo [School of Computer Science & Engineering, Faculty of Engineering, SMVD University, Kakryal, Katra 182320, J& K (India); Shaaban, E.R., E-mail: esam_ramadan2008@yahoo.com [Physics Department, Faculty of Science, Al-Azhar University, Assiut 71542 (Egypt); Shapaan, M. [Department of Physics, Faculty of Science, Al-Azahar University, Cairo (Egypt); Mohamed, S.H. [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Othman, A.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Verma, K.D., E-mail: kdverma1215868@gmail.com [Material Science Research Laboratory, Department of Physics, S. V. College, Aligarh 202001, U.P. (India)

    2016-08-15

    Highlights: • Combined experimental and theoretical researches on ZnSe Thin Films. • The film thickness and refractive index were determined using envelope method. • The absorption coefficient and the energy gap were calculated. • Dispersion parameters were determined using Wemple-DiDomenico relation. • The third order susceptibility and nonlinear refractive index were calculated. - Abstract: Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702 eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.

  15. Slurry bubble column hydrodynamics

    Science.gov (United States)

    Rados, Novica

    Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids

  16. Assessment of Safety Parameters for Radiological Explosion Based on Gaussian Dispersion Model

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Alok [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yu, Hyungjoon; Kim, Hong Suk [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2014-10-15

    These sources if used with explosive (called RDD - radiological dispersion device), can cause dispersion of radioactive material resulting in public exposure and contamination of the environment. Radiological explosion devices are not weapons for the mass destruction like atom bombs, but can cause the death of few persons and contamination of large areas. The reduction of the threat of radiological weapon attack by terrorist groups causing dispersion of radioactive material is one of the priority tasks of the IAEA Nuclear Safety and Security Program.Emergency preparedness is an essential part for reducing and mitigating radiological weapon threat. Preliminary assessment of dispersion study followed by radiological explosion and its quantitative effect will be helpful for the emergency preparedness team for an early response. The effect of the radiological dispersion depends on various factors like radioisotope, its activity, physical form, amount of explosive used and meteorological factors at the time of an explosion. This study aim to determine the area affected by the radiological explosion as pre assessment to provide feedback to emergency management teams for handling and mitigation the situation after an explosion. Most practical scenarios of radiological explosion are considered with conservative approach for the assessment of the area under a threat for emergency handling and management purpose. Radioisotopes under weak security controls can be used for a radiological explosion to create terror and socioeconomic threat for the public. Prior assessment of radiological threats is helpful for emergency management teams to take prompt decision about evacuation of the affected area and other emergency handling actions. Comparable activities of Co-60 source used in radiotherapy and Sr-90 source of disused and orphaned RTGs with two different quantities of TNT were used for the scenario development of radiological explosion. In the Basic Safety Standard (BSS

  17. Reflectance imaging of the human retina at 810 nm does not suffice to optimize the parameters of hydrodynamic rebalancing laser treatment

    Science.gov (United States)

    Piffaretti, Filippo; Ballini, Jean-Pierre; Perotti, Roberto; Zellweger, Matthieu; Vezzola, Edoardo; Sickenberg, Michel; Wagnières, Georges

    2012-11-01

    The hydrodynamic rebalancing laser (HRL) procedure is an ophthalmic therapy based on the administration of subthreshold infrared (810 nm) laser light to selected areas on the retina to treat various retina diseases. Heterogeneities of tissue response are observed, including undesired retinal damages. Variations of tissue absorbance were hypothesized to cause this uneven response. Irradiation parameters (diameter=100 μm power=1 W; irradiation time: 50 to 200 ms), location and tissue response were studied in 16 patients (20 eyes, 2535 laser spots) to discover any correlation between tissue response and normalized fundus reflectance at 810 nm. The results demonstrate a complex relationship between some pathologies and occurrences of retinal damage, but no clear correlation. One possible reason is that the resolution of reflectance images is insufficient to see "small" (40 μm or less) absorption centers, particularly deep-seated ones. Additionally, tissue parameters other than variations of the fundus optical absorption influence heat diffusion and temperature increases. Monitoring or individualizing the light dose in HRL therapy, or any similar infrared diode laser-based therapy will require more sophisticated technologies, including imaging the retina's reflectance with an improved resolution, as well as refined methods to detect complex correlations between retinal damage and specific pathologies.

  18. Intensification of the Reverse Cationic Flotation of Hematite Ores with Optimization of Process and Hydrodynamic Parameters of Flotation Cell

    Science.gov (United States)

    Poperechnikova, O. Yu; Filippov, L. O.; Shumskaya, E. N.; Filippova, I. V.

    2017-07-01

    The demand of high grade iron ore concentrates is a major issue due to the depletion of rich iron-bearing ores and high competitiveness in the iron ore market. Iron ore production is forced out to upgrade flowsheets to decrease the silica content in the pelettes. Different types of ore have different mineral composition and texture-structural features which require different mineral processing methods and technologies. The paper presents a comparative study of the cationic and anionic flotation routes to process a fine-grain oxidized iron ore. The modified carboxymethyl cellulose was found as the most efficient depressant in reverse cationic flotation. The results of flotation optimization of hematite ores using matrix of second-order center rotatable uniform design allowed to define the collector concentration, impeller rotation speed and air flowrate as the main flotation parameters impacting on the iron ore concentrate quality and iron recovery in a laboratory flotation machine. These parameters have been selected as independent during the experiments.

  19. On the method of strained parameters for a KdV type of equation with exact dispersion property

    CERN Document Server

    Karjanto, N

    2016-01-01

    This paper provides an alternative methodology for analysis of three-wave interactions under the exact dispersion relation associated with gravity waves in fluid of intermediate depth. A Korteweg-de Vries type of equation with exact dispersion property is adopted as the governing equation for unidirectional wave packet evolution. Following the idea from Zakharov's seminal paper (Zakharov, V. E. (1968) Stability of periodic waves of finite amplitude on the surface of a deep fluid. \\textit{Journal of Applied Mechanics and Technical Physics}, {\\bf 9}, 190--194), the equation is transformed from the spatial--temporal domain to the wavenumber--temporal domain. The solution of the transformed equation is sought using the perturbation theory, for which the ansatz is expressed in the form of a regular expansion in the increasing order of a small parameter. After implementing the na\\"{i}ve perturbation method, due to nonlinear mode generation and particular combinations of wavenumbers, the third-order solution contain...

  20. Precise determination of the f0(600) and f0(980) pole parameters from a dispersive data analysis

    CERN Document Server

    Garcia-Martin, R; Pelaez, J R; de Elvira, J Ruiz

    2011-01-01

    We use our latest dispersive analysis of pion-pion scattering data and the very recent Kl4 experimental results to obtain the mass, width and couplings of the two lightest scalar-isoscalar resonances. These parameters are defined from their associated poles in the complex plane. The analytic continuation to the complex plane is made in a model independent way by means of once and twice subtracted dispersion relations for the partial waves, without any other theoretical assumption. We find the f0(600) pole at (457^{+14}_{-13})-i(279^{+11}_{-7}) MeV and that of the f0(980) at (996\\pm7)-i(25^{+10}_{-6}) MeV, whereas their respective couplings to two pions are 3.59^{+0.11}_{-0.13} GeV and 2.3\\pm0.2 GeV.

  1. Calculation of Design Parameters for an Equilibrium LEU Core in the NBSR using a U7Mo Dispersion Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Hanson A. L.; Diamond D.

    2014-06-30

    A plan is being developed for the conversion of the NIST research reactor (NBSR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. The LEU fuel may be a monolithic foil (LEUm) of U10Mo (10% molybdenum by weight in an alloy with uranium) or a dispersion of U7Mo in aluminum (LEUd). A previous report provided neutronic calculations for the LEUm fuel and this report presents the neutronics parameters for the LEUd fuel. The neutronics parameters for the LEUd fuel are compared to those previously obtained for the present HEU fuel and the proposed LEUm fuel. The results show no significant differences between the LEUm and the LEUd other than the LEUd fuel requires slightly less uranium than the LEUm fuel due to less molybdenum being present. The calculations include kinetics parameters, reactivity coefficients, reactivity worths of control elements and abnormal configurations, and power distributions under normal operation and with misloaded fuel elements.

  2. Influence of geometric and hydro-dynamic parameters of injector on calculation of spray characteristics of diesel engines

    Directory of Open Access Journals (Sweden)

    Filipović Ivan

    2011-01-01

    Full Text Available The main role in air/fuel mixture formation at the IC diesel engines has the energy introduced by fuel into the IC engine that is the characteristics of spraying fuel into the combustion chamber. The characteristic can be defined by the spray length, the spray cone angle, the physical and the chemical structure of fuel spray by different sections. Having in mind very complex experimental setups for researching in this field, the mentioned characteristics are mostly analyzed by calculations. There are two methods in the literature, the first based on use of the semi-empirical expressions (correlations and the second, the calculations of spray characteristics by use of very complex mathematical methods. The second method is dominant in the modern literature. The main disadvantage of the calculation methods is a correct definition of real state at the end of the nozzle orifice (real boundary conditions. The majority of the researchers in this field use most frequently the coefficient of total losses inside the injector. This coefficient depends on injector design, as well as depends on the level of fuel energy and fuel energy transformation along the injector. Having in mind the importance of the real boundary conditions, the complex methods for calculation of the fuel spray characteristics should have the calculation of fuel flows inside the injector and the calculation of spray characteristics together. This approach is a very complex numerical problem and there are no existing computer programs with satisfactory calculation results. Analysis of spray characteristics by use of the semi-empirical expressions (correlations is presented in this paper. The special attention is dedicated to the analysis of the constant in the semi-empirical expressions and influence parameters on this constant. Also, the method for definition of realistic boundary condition at the end of the nozzle orifice is presented in the paper. By use of this method completely

  3. Hydrodynamical Simulations to Determine the Feeding Rate of Black Holes by the Tidal Disruption of Stars: The Importance of the Impact Parameter and Stellar Structure

    CERN Document Server

    Guillochon, James

    2012-01-01

    The disruption of stars by supermassive black holes has been linked to more than a dozen flares in the cores of galaxies out to redshift $z \\sim 0.4$. Modeling these flares properly requires a prediction of the rate of mass return to the black hole after a disruption. Through hydrodynamical simulation, we show that aside from the full disruption of a solar mass star at the exact limit where the star is destroyed, the common assumptions used to estimate $\\dot{M}(t)$, the rate of mass return to the black hole, are largely invalid. While the analytical approximation to tidal disruption predicts that the least-centrally concentrated stars and the deepest encounters should have more quickly-peaked flares, we find that the most-centrally concentrated stars have the quickest-peaking flares, and the trend between the time of peak and the impact parameter for deeply-penetrating encounters reverses beyond the critical distance at which the star is completely destroyed. We also show that the most-centrally concentrated ...

  4. Relativistic hydrodynamics

    CERN Document Server

    Luciano, Rezzolla

    2013-01-01

    Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solut...

  5. Effect of solution molarity on optical dispersion energy parameters and electrochromic performance of Co3O4 films

    Science.gov (United States)

    Dhas, C. Ravi; Venkatesh, R.; Sivakumar, R.; Raj, A. Moses Ezhil; Sanjeeviraja, C.

    2017-10-01

    Co3O4 films were deposited on glass and FTO (F:SnO2) substrates by different solution molarities (0.05-0.20 M) through nebulizer spray technique. The crystalline quality of the films was evaluated by X-ray diffraction. The morphological variation of Co3O4 films for different solution concentration was observed from scanning electron microscopy. Optical constants (n and k) and dispersion energy parameters were calculated by fitting the transmittance curves using Swanepoel envelope method. The electrical parameters such as sheet resistance and activation energy were estimated using four probe method. The electrochromic performance of the films was analyzed by electrochemical measurements such as cyclic voltammetry, chronoamperometry, chronocoulometry and optical contrast studies.

  6. Focus expansion and stability of the spread parameter estimate of the power law model for dispersal gradients

    Directory of Open Access Journals (Sweden)

    Peter S. Ojiambo

    2017-06-01

    Full Text Available Empirical and mechanistic modeling indicate that pathogens transmitted via aerially dispersed inoculum follow a power law, resulting in dispersive epidemic waves. The spread parameter (b of the power law model, which is an indicator of the distance of the epidemic wave front from an initial focus per unit time, has been found to be approximately 2 for several animal and plant diseases over a wide range of spatial scales under conditions favorable for disease spread. Although disease spread and epidemic expansion can be influenced by several factors, the stability of the parameter b over multiple epidemic years has not been determined. Additionally, the size of the initial epidemic area is expected to be strongly related to the final epidemic extent for epidemics, but the stability of this relationship is also not well established. Here, empirical data of cucurbit downy mildew epidemics collected from 2008 to 2014 were analyzed using a spatio-temporal model of disease spread that incorporates logistic growth in time with a power law function for dispersal. Final epidemic extent ranged from 4.16 ×108 km2 in 2012 to 6.44 ×108 km2 in 2009. Current epidemic extent became significantly associated (P < 0.0332; 0.56 < R2 < 0.99 with final epidemic area beginning near the end of April, with the association increasing monotonically to 1.0 by the end of the epidemic season in July. The position of the epidemic wave-front became exponentially more distant with time, and epidemic velocity increased linearly with distance. Slopes from the temporal and spatial regression models varied with about a 2.5-fold range across epidemic years. Estimates of b varied substantially ranging from 1.51 to 4.16 across epidemic years. We observed a significant b ×time (or distance interaction (P < 0.05 for epidemic years where data were well described by the power law model. These results suggest that the spread parameter b may not be stable over multiple epidemic

  7. Structure, optical spectroscopy and dispersion parameters of ZnGa2Se4 thin films at different annealing temperatures

    Science.gov (United States)

    Fadel, M.; Yahia, I. S.; Sakr, G. B.; Yakuphanoglu, F.; Shenouda, S. S.

    2012-06-01

    Thin films of ZnGa2Se4 were deposited by thermal evaporation method of pre-synthesized ingot material onto highly cleaned microscopic glass substrates. The chemical composition of the investigated compound thin film form was determined by means of energy-dispersive X-ray spectroscopy. X-ray diffraction XRD analysis revealed that the powder compound is polycrystalline and the as-deposited and the annealed films at Ta = 623 and 673 K have amorphous phase, while that annealed at Ta = 700 K is polycrystalline with a single phase of a defective chalcopyrite structure similar to that of the synthesized material. The unit-cell lattice parameters were determined and compared with the reported data. Also, the crystallite size L, the dislocation density δ and the main internal strain ɛ were calculated. Analyses of the AFM images confirm the nanostructure of the prepared annealed film at 700 K. The refractive index n and the film thickness d were determined from optical transmittance data using Swanepoel's method. It was found that the refractive index dispersion data obeys the single oscillator model from which the dispersion parameters were determined. The electric susceptibility of free carriers and the carrier concentration to the effective mass ratio were determined according to the model of Spitzer and Fan. The analysis of the optical absorption revealed both the indirect and direct energy gaps. The indirect optical gaps are presented in the amorphous films (as-deposited, annealed at 623 and 673 K), while the direct energy gap characterized the polycrystalline film at 700 K. Graphical representations of ɛ1, ɛ2, tan δ, - Im[1/ɛ*] and - Im[(1/ɛ* + 1)] are also presented. ZnGa2Se4 is a good candidate for optoelectronic and solar cell devices.

  8. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru [Faculty of Physics, Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-06-15

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.

  9. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    Science.gov (United States)

    Andreev, Pavel A.

    2015-06-01

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.

  10. Dry Powder Inhalers: Study of the Parameters Influencing Adhesion and Dispersion of Fluticasone Propionate

    OpenAIRE

    Le, V. N. P.; Thi, T. H. Hoang; Robins, E.; Flament, M. P.

    2012-01-01

    Interactions between particles are dependent on the physicochemical characteristics of the interacting particles but it is also important to consider the manufacturing process. Blending active pharmaceutical ingredient (API) with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend. The aim of this work was to study parameters that influence the interactions between API and carrier in adhesive mixtures ...

  11. Theoretical hydrodynamics

    CERN Document Server

    Milne-Thomson, L M

    2011-01-01

    This classic exposition of the mathematical theory of fluid motion is applicable to both hydrodynamics and aerodynamics. Based on vector methods and notation with their natural consequence in two dimensions - the complex variable - it offers more than 600 exercises and nearly 400 diagrams. Prerequisites include a knowledge of elementary calculus. 1968 edition.

  12. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  13. Ship Hydrodynamics

    Science.gov (United States)

    Lafrance, Pierre

    1978-01-01

    Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)

  14. A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions

    Science.gov (United States)

    Mastin, L.G.; Guffanti, M.; Servranckx, R.; Webley, P.; Barsotti, S.; Dean, K.; Durant, A.; Ewert, J.W.; Neri, A.; Rose, William I.; Schneider, D.; Siebert, L.; Stunder, B.; Swanson, G.; Tupper, A.; Volentik, A.; Waythomas, C.F.

    2009-01-01

    During volcanic eruptions, volcanic ash transport and dispersion models (VATDs) are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind. Those models use input parameters, called "eruption source parameters", such as plume height H, mass eruption rate ???, duration D, and the mass fraction m63 of erupted debris finer than about 4??{symbol} or 63????m, which can remain in the cloud for many hours or days. Observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected. Moreover, observed plume height may change during an eruption, requiring rapid assignment of new parameters. This paper reports on a group effort to improve the accuracy of source parameters used by VATDs in the early hours of an eruption. We do so by first compiling a list of eruptions for which these parameters are well constrained, and then using these data to review and update previously studied parameter relationships. We find that the existing scatter in plots of H versus ??? yields an uncertainty within the 50% confidence interval of plus or minus a factor of four in eruption rate for a given plume height. This scatter is not clearly attributable to biases in measurement techniques or to well-recognized processes such as elutriation from pyroclastic flows. Sparse data on total grain-size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions (??? 0.01) and large silicic ones (> 0.5). We classify eleven eruption types; four types each for different sizes of silicic and mafic eruptions; submarine eruptions; "brief" or Vulcanian eruptions; and eruptions that generate co-ignimbrite or co-pyroclastic flow plumes. For each eruption type we assign source parameters. We then assign a characteristic eruption type to each of the world's ??? 1500

  15. Radiation Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Castor, J I

    2003-10-16

    The discipline of radiation hydrodynamics is the branch of hydrodynamics in which the moving fluid absorbs and emits electromagnetic radiation, and in so doing modifies its dynamical behavior. That is, the net gain or loss of energy by parcels of the fluid material through absorption or emission of radiation are sufficient to change the pressure of the material, and therefore change its motion; alternatively, the net momentum exchange between radiation and matter may alter the motion of the matter directly. Ignoring the radiation contributions to energy and momentum will give a wrong prediction of the hydrodynamic motion when the correct description is radiation hydrodynamics. Of course, there are circumstances when a large quantity of radiation is present, yet can be ignored without causing the model to be in error. This happens when radiation from an exterior source streams through the problem, but the latter is so transparent that the energy and momentum coupling is negligible. Everything we say about radiation hydrodynamics applies equally well to neutrinos and photons (apart from the Einstein relations, specific to bosons), but in almost every area of astrophysics neutrino hydrodynamics is ignored, simply because the systems are exceedingly transparent to neutrinos, even though the energy flux in neutrinos may be substantial. Another place where we can do ''radiation hydrodynamics'' without using any sophisticated theory is deep within stars or other bodies, where the material is so opaque to the radiation that the mean free path of photons is entirely negligible compared with the size of the system, the distance over which any fluid quantity varies, and so on. In this case we can suppose that the radiation is in equilibrium with the matter locally, and its energy, pressure and momentum can be lumped in with those of the rest of the fluid. That is, it is no more necessary to distinguish photons from atoms, nuclei and electrons, than it is

  16. Multidimensional Absorptive-Dispersive Inverse Scattering and Parameter Leakage at the Linear Step

    Science.gov (United States)

    Innanen, K. A.; Weglein, A. B.; Lira, J. E.

    2008-12-01

    Research is active into the use of inverse scattering to create direct non-linear methods for task-separated imaging, inversion, and Q compensation of primary reflections (Weglein et al., 2008). We will discuss some recent developments within the third of these efforts. First, we will describe an extension of the absorptive inverse scattering equations in multiple dimensions to the case of an absorptive reference medium. This requires a generalized definition of the perturbation as compared to the non-absorptive reference medium case. Second, because of its potential impact on a recently described prototype direct non-linear Q compensation algorithm (Innanen and Weglein, 2005; Innanen and Lira, 2008), we will discuss the issue of leakage of absorptive parameters. Leakage is an inverse phenomenon in which actual variations in one medium parameter lead to variations of the linear estimate of other parameters, especially at large angles and large contrasts. This is a linear issue exclusively; the full non-linear inverse scattering series addresses leakage, and corrects for it. Our prototype non-linear Q compensation algorithm involves the isolated use of some, but not all, of the non-linear terms of the inverse scattering series. The question we wish to address is: does this subset of the full inverse series also manage and correct for leakage, or will it over- or under-compensate at large angles and large contrasts? If the latter, further analysis and collection of inverse series components will likely be indicated. A. B. Weglein, A. C. Ramirez, K. A. Innanen, F. Liu, J. E. Lira and S. Jiang, 'The underlying unity of distinct processing algorithms for (1) the removal of free-surface and internal multiples, (2) Q compensation (without Q) (3) depth imaging, (4) nonlinear AVO, that derive from the inverse scattering series', 2008: Proc. Soc. Expl. Geop. K. A. Innanen and A. B. Weglein, 'Towards non-linear construction of a Q compensation operator directly from measured

  17. HYDRODYNAMIC CHARACTERISTICS OF FLUIDIZED BEDS CONTAINING LARGE POLYDISPERSED PARTICLES

    Directory of Open Access Journals (Sweden)

    K. TANNOUS

    1998-03-01

    Full Text Available This paper presents a hydrodynamic study of fluidized beds containing large polydispersed particles (B and D categories of Geldart’s classification. The experiments have been carried out with particle samples characterized by the Rosin-Rammler-Sperling (RRS size distribution. The parameters analyzed in this study are the dispersion index and the average particle diameter obtained from the RRS size distribution model. Correlations to estimate the initial and complete fluidization velocities and the segregation velocity as a function of these two size distribution parameters have been established.

  18. Achieving concentrated graphene dispersions in water/acetone mixtures by the strategy of tailoring Hansen solubility parameters

    Science.gov (United States)

    Yi, Min; Shen, Zhigang; Zhang, Xiaojing; Ma, Shulin

    2013-01-01

    Although exfoliating graphite to give graphene paves a new way for graphene preparation, a general strategy of low-boiling-point solvents and high graphene concentration is still highly required. In this study, using the strategy of tailoring Hansen solubility parameters (HSP), a method based on exfoliation of graphite in water/acetone mixtures is demonstrated to achieve concentrated graphene dispersions. It is found that in the scope of blending two mediocre solvents, tailoring the HSP of water/acetone mixtures to approach the HSP of graphene could yield graphene dispersions at a high concentration of up to 0.21 mg ml-1. The experimentally determined optimum composition of the mixtures occurs at an acetone mass fraction of ˜75%. The trend of concentration varying with mixture compositions could be well predicated by the model, which relates the concentration to the mixing enthalpy within the scope of HSP theory. The resultant dispersion is highly stabilized. Atomic force microscopic statistical analysis shows that up to ˜50% of the prepared nanosheets are less than 1 nm thick after 4 h sonication and 114g centrifugation. Analyses based on diverse characterizations indicate the graphene sheets to be largely free of basal plane defects and oxidation. The filtered films are also investigated in terms of their electrical and optical properties to show reasonable conductivity and transparency. The strategy of tailoring HSP, which can be easily extended to various solvent systems, and water/acetone mixtures here, extends the scope for large-scale production of graphene in low-boiling-point solutions.

  19. Dispersive Surface Energy and Acid-Base Parameters of Tosylate Functionalized Poly(ethylene glycol via Inverse Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Feyza Sesigur

    2014-01-01

    Full Text Available An inverse gas chromatographic (IGC study of the sorption properties of poly(ethylene glycol modified with tosylate (PEG-TOS was presented. PEG-TOS was synthesized via the tosylation of the corresponding poly(ethylene glycol (PEG with p-toluenesulfonyl chloride in the basic medium. The synthesized PEG-Tos was characterized by FTIR-ATR and 1HNMR techniques. The retention diagrams of n-hexane, n-heptane, n-octane, n-nonane, n-decane, dichloromethane, chloroform, acetone, tetrahydrofuran, ethyl acetate, and ethanol on the PEG and PEG-Tos were plotted at temperatures in K between 303 and 373 by inverse gas chromatography technique. The dispersive component of the surface-free energy, γSD, of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. Thermodynamic parameters of adsorption (free energy, ΔGAS, enthalpy, ΔHAS, and entropy, ΔSAS, dispersive components of the surface energies, γSD, and the acid, KA, and base, KD, constants for the PEG and PEG-Tos were calculated and the results were discussed.

  20. Computer modelling of the meteorological and spraying parameters that influence the aerial dispersion of agrochemical sprays

    Science.gov (United States)

    Mokeba, M. L.; Salt, D. W.; Lee, B. E.; Ford, M. G.

    An insight into the nature of prevailing meteorological conditions and the manner in which they interact with spraying parameters is an important prerequisite in the analysis of the dynamics of agrochemical sprays. Usually, when these sprays are projected from hydraulic nozzles, their initial velocity is greater than that of the ambient wind speed. The flowfield therefore experiences changes in speed and direction which are felt upstream as well as downstream of the spray droplets. The pattern of the droplet flow, i.e. the shape of the streamlines marking typical trajectories, will be determined by a balance of viscous forces related to wind speed, inertial forces resulting from the acceleration of the airstream and pressure forces which can be viewed in terms of the drag forces exerted on the spray droplets themselves. At a certain distance in the ensuing motion, when the initial velocity of the spray droplets has decreased sufficiently for there to be no acceleration, their trajectories will be controlled entirely by the random effects of turbulence. These two transport processes in the atmosphere can be modelled mathematically using computers. This paper presents a model that considers the velocity of spray droplets to consist of a ballistic velocity component superimposed by a random-walk velocity component. The model is used to study the influence of meteorological and spraying parameters on the three-dimensional dynamics of spray droplets projected in specified directions in neutral and unstable weather conditions. The ballistic and random-walk velocity components are scaled by factors of (1-ξ) and ξ respectively, where ξ is the ratio of the sedimentation velocity and the relative velocity between the spray droplets and the surrounding airstream. This ratio increases progressively as the initial velocity of the spray droplet decreases with air resistance and attains a maximum when the sedimentation velocity has been reached. As soon as this occurs, the

  1. Bacterial hydrodynamics

    CERN Document Server

    Lauga, Eric

    2015-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.

  2. Electrochemical noise of the erosion-corrosion of copper in relation with its hydrodynamic parameters; Ruido electroquimico de la erosion-corrosion en cobre: su relacion con los parametros hidrodinamicos

    Energy Technology Data Exchange (ETDEWEB)

    Castaneda, I.; Romero, M.; Malo, J.M.; Uruchurtu, J.

    2010-07-01

    This work presents the electrochemical noise results obtained of the surface degradation on copper, due to erosion corrosion phenomena, which were a function of the hydrodynamic parameters of the system (fluid movement). A modified rotating cylinder (RC) comprising three ring electrodes under two rotating speeds (880 and 1750 rpm with a Reynolds numbers 1486 Re and 2972 Re, respectively) were used. Characteristic electrochemical noise spectra as a function of the hydrodynamic parameters were found, as well as surface attack intensities the noise signal. An increase and a more uniform attack due to particle impact was related to larger particle size and lesser erosion corrosion intensity, in the form of more localized attack over the surface, was obtained for smaller ones. Erosion corrosion attack presents characteristic electrochemical current and potential noise signals, according to the laminar or transitional turbulent regime and particle size added. (Author).

  3. Nanoflow hydrodynamics

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Dyre, Jeppe C.; Daivis, Peter J.;

    2011-01-01

    We show by nonequilibrium molecular dynamics simulations that the Navier-Stokes equation does not correctly describe water flow in a nanoscale geometry. It is argued that this failure reflects the fact that the coupling between the intrinsic rotational and translational degrees of freedom becomes...... important for nanoflows. The coupling is correctly accounted for by the extended Navier-Stokes equations that include the intrinsic angular momentum as an independent hydrodynamic degree of freedom. © 2011 American Physical Society....

  4. Thickness dependence of dispersion parameters of the MoO{sub x} thin films prepared using the vacuum evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Akın, Ümmühan, E-mail: uakin@selcuk.edu.tr; Şafak, Haluk

    2015-10-25

    The optical behaviors of molybdenum oxide thin films are highly important due to their widespread applications. In the present paper, the effect of thickness on the structure, morphology and optical properties of molybdenum oxide (MoO{sub x}) thin films prepared on Corning glass substrates using thermal evaporation technique was studied. The structure and morphology of films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, while their optical properties were investigated by UV-VIS-NIR spectrophotometry in the spectral range from 300 to 2500 nm. It was observed that whole films have amorphous structure and also they showed rather high transmittance values reached nearly up to 90%. Absorption analysis showed two types of electronic transitions; both direct and indirect interband transition energy values of films decrease from 4.47 to 3.45 eV and from 3.00 to 2.75 eV, respectively, with increasing the film thickness, while the width of the localized states tail increases with thickness. This decrease in the band gap value can be attributed to the rising oxygen-ion vacancy densities with the thickness. The refractive indices of films were calculated from Sellmeier coefficients determined by nonlinear curve fitting method based on the measured transmittance spectral data. The dispersion of the refractive index was discussed in terms of the Wemple-DiDomenico single-oscillator model. The dispersion parameters such as average oscillator energy, E{sub o}, the dispersion energy, E{sub d}, and static refractive index n{sub o} were evaluated and they found to vary significantly with the film thickness. - Highlights: • MoO{sub x} thin films with different thickness were prepared using the vacuum evaporation technique. • The variation of fundamental absorption edge with the film thickness was determined. • A detailed dispersion analysis based on the Wemple-DiDomenico model was performed. • The dependence of all

  5. Scalability of Hydrodynamic Simulations

    CERN Document Server

    Tang, Shikui

    2009-01-01

    Many hydrodynamic processes can be studied in a way that is scalable over a vastly relevant physical parameter space. We systematically examine this scalability, which has so far only briefly discussed in astrophysical literature. We show how the scalability is limited by various constraints imposed by physical processes and initial conditions. Using supernova remnants in different environments and evolutionary phases as application examples, we demonstrate the use of the scaling as a powerful tool to explore the interdependence among relevant parameters, based on a minimum set of simulations. In particular, we devise a scaling scheme that can be used to adaptively generate numerous seed remnants and plant them into 3D hydrodynamic simulations of the supernova-dominated interstellar medium.

  6. Wavelength dispersive X-ray fluorescence analysis using fundamental parameter approach of Catha edulis and other related plant samples

    Science.gov (United States)

    Shaltout, Abdallah A.; Moharram, Mohammed A.; Mostafa, Nasser Y.

    2012-01-01

    This work is the first attempt to quantify trace elements in the Catha edulis plant (Khat) with a fundamental parameter approach. C. edulis is a famous drug plant in east Africa and Arabian Peninsula. We have previously confirmed that hydroxyapatite represents one of the main inorganic compounds in the leaves and stalks of C. edulis. Comparable plant leaves from basil, mint and green tea were included in the present investigation as well as trifolium leaves were included as a non-related plant. The elemental analyses of the plants were done by Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectroscopy. Standard-less quantitative WDXRF analysis was carried out based on the fundamental parameter approaches. According to the standard-less analysis algorithms, there is an essential need for an accurate determination of the amount of organic material in the sample. A new approach, based on the differential thermal analysis, was successfully used for the organic material determination. The obtained results based on this approach were in a good agreement with the commonly used methods. Depending on the developed method, quantitative analysis results of eighteen elements including; Al, Br, Ca, Cl, Cu, Fe, K, Na, Ni, Mg, Mn, P, Rb, S, Si, Sr, Ti and Zn were obtained for each plant. The results of the certified reference materials of green tea (NCSZC73014, China National Analysis Center for Iron and Steel, Beijing, China) confirmed the validity of the proposed method.

  7. Introduction to Hydrodynamics

    CERN Document Server

    Jeon, Sangyong

    2015-01-01

    We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.

  8. Wavelength dispersive X-ray fluorescence analysis using fundamental parameter approach of Catha edulis and other related plant samples

    Energy Technology Data Exchange (ETDEWEB)

    Shaltout, Abdallah A., E-mail: shaltout_a@hotmail.com [Spectroscopy Department, Physics Division, National Research Center, El Behooth Str., 12622 Dokki, Cairo (Egypt); Faculty of science, Taif University, 21974 Taif, P.O. Box 888 (Saudi Arabia); Moharram, Mohammed A. [Spectroscopy Department, Physics Division, National Research Center, El Behooth Str., 12622 Dokki, Cairo (Egypt); Mostafa, Nasser Y. [Faculty of science, Taif University, 21974 Taif, P.O. Box 888 (Saudi Arabia); Chemistry Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-01-15

    This work is the first attempt to quantify trace elements in the Catha edulis plant (Khat) with a fundamental parameter approach. C. edulis is a famous drug plant in east Africa and Arabian Peninsula. We have previously confirmed that hydroxyapatite represents one of the main inorganic compounds in the leaves and stalks of C. edulis. Comparable plant leaves from basil, mint and green tea were included in the present investigation as well as trifolium leaves were included as a non-related plant. The elemental analyses of the plants were done by Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectroscopy. Standard-less quantitative WDXRF analysis was carried out based on the fundamental parameter approaches. According to the standard-less analysis algorithms, there is an essential need for an accurate determination of the amount of organic material in the sample. A new approach, based on the differential thermal analysis, was successfully used for the organic material determination. The obtained results based on this approach were in a good agreement with the commonly used methods. Depending on the developed method, quantitative analysis results of eighteen elements including; Al, Br, Ca, Cl, Cu, Fe, K, Na, Ni, Mg, Mn, P, Rb, S, Si, Sr, Ti and Zn were obtained for each plant. The results of the certified reference materials of green tea (NCSZC73014, China National Analysis Center for Iron and Steel, Beijing, China) confirmed the validity of the proposed method. - Highlights: Black-Right-Pointing-Pointer Quantitative analysis of Catha edulis was carried out using standardless WDXRF. Black-Right-Pointing-Pointer Differential thermal analysis was used for determination of the loss of ignition. Black-Right-Pointing-Pointer The existence of hydroxyapatite in Catha edulis plant has been confirmed. Black-Right-Pointing-Pointer The CRM results confirmed the validity of the developed method.

  9. Maximum likelihood estimation of the negative binomial dispersion parameter for highly overdispersed data, with applications to infectious diseases.

    Directory of Open Access Journals (Sweden)

    James O Lloyd-Smith

    Full Text Available BACKGROUND: The negative binomial distribution is used commonly throughout biology as a model for overdispersed count data, with attention focused on the negative binomial dispersion parameter, k. A substantial literature exists on the estimation of k, but most attention has focused on datasets that are not highly overdispersed (i.e., those with k>or=1, and the accuracy of confidence intervals estimated for k is typically not explored. METHODOLOGY: This article presents a simulation study exploring the bias, precision, and confidence interval coverage of maximum-likelihood estimates of k from highly overdispersed distributions. In addition to exploring small-sample bias on negative binomial estimates, the study addresses estimation from datasets influenced by two types of event under-counting, and from disease transmission data subject to selection bias for successful outbreaks. CONCLUSIONS: Results show that maximum likelihood estimates of k can be biased upward by small sample size or under-reporting of zero-class events, but are not biased downward by any of the factors considered. Confidence intervals estimated from the asymptotic sampling variance tend to exhibit coverage below the nominal level, with overestimates of k comprising the great majority of coverage errors. Estimation from outbreak datasets does not increase the bias of k estimates, but can add significant upward bias to estimates of the mean. Because k varies inversely with the degree of overdispersion, these findings show that overestimation of the degree of overdispersion is very rare for these datasets.

  10. Submarine hydrodynamics

    CERN Document Server

    Renilson, Martin

    2015-01-01

    This book adopts a practical approach and presents recent research together with applications in real submarine design and operation. Topics covered include hydrostatics, manoeuvring, resistance and propulsion of submarines. The author briefly reviews basic concepts in ship hydrodynamics and goes on to show how they are applied to submarines, including a look at the use of physical model experiments. The issues associated with manoeuvring in both the horizontal and vertical planes are explained, and readers will discover suggested criteria for stability, along with rudder and hydroplane effectiveness. The book includes a section on appendage design which includes information on sail design, different arrangements of bow planes and alternative stern configurations. Other themes explored in this book include hydro-acoustic performance, the components of resistance and the effect of hull shape. Readers will value the author’s applied experience as well as the empirical expressions that are presented for use a...

  11. Recent development of hydrodynamic modeling

    Science.gov (United States)

    Hirano, Tetsufumi

    2014-09-01

    In this talk, I give an overview of recent development in hydrodynamic modeling of high-energy nuclear collisions. First, I briefly discuss about current situation of hydrodynamic modeling by showing results from the integrated dynamical approach in which Monte-Carlo calculation of initial conditions, quark-gluon fluid dynamics and hadronic cascading are combined. In particular, I focus on rescattering effects of strange hadrons on final observables. Next I highlight three topics in recent development in hydrodynamic modeling. These include (1) medium response to jet propagation in di-jet asymmetric events, (2) causal hydrodynamic fluctuation and its application to Bjorken expansion and (3) chiral magnetic wave from anomalous hydrodynamic simulations. (1) Recent CMS data suggest the existence of QGP response to propagation of jets. To investigate this phenomenon, we solve hydrodynamic equations with source term which exhibits deposition of energy and momentum from jets. We find a large number of low momentum particles are emitted at large angle from jet axis. This gives a novel interpretation of the CMS data. (2) It has been claimed that a matter created even in p-p/p-A collisions may behave like a fluid. However, fluctuation effects would be important in such a small system. We formulate relativistic fluctuating hydrodynamics and apply it to Bjorken expansion. We found the final multiplicity fluctuates around the mean value even if initial condition is fixed. This effect is relatively important in peripheral A-A collisions and p-p/p-A collisions. (3) Anomalous transport of the quark-gluon fluid is predicted when extremely high magnetic field is applied. We investigate this possibility by solving anomalous hydrodynamic equations. We found the difference of the elliptic flow parameter between positive and negative particles appears due to the chiral magnetic wave. Finally, I provide some personal perspective of hydrodynamic modeling of high energy nuclear collisions

  12. The choice of process parameters to obtain a stable dispersion system of plant-based bioactivated dicotyledonous seeds

    Directory of Open Access Journals (Sweden)

    L. A. Samofalova

    2016-01-01

    Full Text Available The article dealswith the search for the unification of technological approaches to increase the efficiency of separation of the protein complex and stability of the plant foundations from seed dicotyledonous economically important crops of soybean, hemp, buckwheat. Uneven localization of nitrogenous substances in the seed largely determines the accessibility of protein complexes for extraction. Natural fermentation of spare proteins in cellular structures when the germination process starts leads to the accumulation of soluble nitrogen, and the change in the salt composition of protoplasm facilitates the transition in the solution of insoluble complexes in the form of colloids. It is shown that fine grinding of dry seeds increases the efficiency of extraction by 1.3–1.6 times, while rough grinding increases bioactivity by 1.6–1.8 times. The dispersion containing 8.1±0.7% of dry matter at buckwheat bases and 9.5±1,3% at hemp and soy bases with the water ratio 1:4 to 1:7 satisfy the requirements of taste sensations and fullness of the chemical composition. Based on the results of the extraction of protein of buckwheat seeds the conclusion has been drawn that there is a need for a differentiated approach to selecting conditions for the creation of food framework. Taking into consideration the fact that the amount of calcium in buckwheat seeds is17–25 times smaller than in oil seeds and the quantity of phosphorus is 1.6–2 times smaller, the contribution of electrostatic forces in the protein solubility is small and the additional actions to activate the protein complex are required. To predict the properties of vegetable bases of bioactivated soybean seeds and hemp, the central composite uniform-rotatable planning was applied and the full factorial experiment with factorial scheme 3×3×3 (33 was selected. The preferred combination of values of the input parameters X1, X2, X3 was discovered. They provide for the maximum of Y

  13. The hydrodynamics of colloidal gelation.

    Science.gov (United States)

    Varga, Zsigmond; Wang, Gang; Swan, James

    2015-12-14

    Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions.

  14. Hydrodynamic characteristics of UASB bioreactors.

    Science.gov (United States)

    John, Siby; Tare, Vinod

    2011-10-01

    The hydrodynamic characteristics of UASB bioreactors operated under different organic loading and hydraulic loading rates were studied, using three laboratory scale models treating concocted sucrose wastewater. Residence time distribution (RTD) analysis using dispersion model and tanks-in-series model was directed towards the characterization of the fluid flow pattern in the reactors and correlation of the hydraulic regime with the biomass content and biogas production. Empty bed reactors followed a plug flow pattern and the flow pattern changed to a large dispersion mixing with biomass and gas production. Effect of increase in gas production on the overall hydraulics was insignificant.

  15. Hydrodynamics of insect spermatozoa

    Science.gov (United States)

    Pak, On Shun; Lauga, Eric

    2010-11-01

    Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.

  16. Hydrodynamics of pedestrians' instability in floodwaters

    Science.gov (United States)

    Arrighi, Chiara; Oumeraci, Hocine; Castelli, Fabio

    2017-01-01

    People's safety is the first objective to be fulfilled by flood risk mitigation measures, and according to existing reports on the causes of casualties, most of the fatalities are due to inappropriate behaviour such as walking or driving in floodwaters. Currently available experimental data on people instability in floodwaters suffer from a large dispersion primarily depending on the large variability of the physical characteristics of the subjects. This paper introduces a dimensionless mobility parameter θP for people partly immersed in flood flows, which accounts for both flood and subject characteristics. The parameter θP is capable of identifying a unique threshold of instability depending on a Froude number, thus reducing the scatter of existing experimental data. Moreover, a three-dimensional (3-D) numerical model describing the detailed geometry of a human body and reproducing a selection of critical pairs of water depth and velocity is presented. The numerical results in terms of hydrodynamic forces and force coefficients are analysed and discussed. Both the mobility parameter θP and the numerical results hint at the crucial role of the Froude number and relative submergence as the most relevant dimensionless numbers to interpret the loss of stability. Finally, the mobility parameter θP is compared with an analogous dimensionless parameter for vehicles' instability in floodwaters, providing a new contribution to support flood risk management and educating people.

  17. Precise determination of the parameters of resonances f0(500 and f0(980 by fitting the data and dispersion relations

    Directory of Open Access Journals (Sweden)

    Pelaez J. R.

    2012-12-01

    Full Text Available The long-standing puzzle in the parameters of the f0(500, as well as the f0(980, is finally being settled [1] thanks to precise dispersive analyses carried out during the last years. Here we report on our very recent dispersive data analysis which allowed for a precise and model independent determination of the amplitudes for the S, P, D and F waves [2–4]. The analytic continuation of once subtracted dispersion relations for the S0 wave to the complex energy plane leads to very precise results for the f0(500 pole: √spole = 457-13+14 - i279-7+11 MeV and for the f0(980 pole: √spole = 996 ± 7 - i25-6+10 MeV.

  18. Anomalous hydrodynamics in two dimensions

    Indian Academy of Sciences (India)

    Rabin Banerjee

    2016-02-01

    A new approach is presented to discuss two-dimensional hydrodynamics with gauge and gravitational anomalies. Exact constitutive relations for the stress tensor and charge current are obtained. Also, a connection between response parameters and anomaly coefficients is discussed. These are new results which, in the absence of the gauge sector, reproduce the results found by the gradient expansion approach.

  19. Investigating the origin of cyclical wind variability in hot massive stars - II. Hydrodynamical simulations of corotating interaction regions using realistic spot parameters for the O giant ξ Persei

    Science.gov (United States)

    David-Uraz, A.; Owocki, S. P.; Wade, G. A.; Sundqvist, J. O.; Kee, N. D.

    2017-09-01

    OB stars exhibit various types of spectral variability historically associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These features have been proposed to be caused either by magnetic fields or non-radial pulsations. In this second paper of this series, we revisit the canonical phenomenological hydrodynamical modelling used to explain the formation of DACs by taking into account modern observations and more realistic theoretical predictions. Using constraints on putative bright spots located on the surface of the O giant ξ Persei derived from high precision space-based broad-band optical photometry obtained with the Microvariability and Oscillations of Stars (MOST) space telescope, we generate 2D hydrodynamical simulations of corotating interaction regions in its wind. We then compute synthetic ultraviolet (UV) resonance line profiles using Sobolev Exact Integration and compare them with historical timeseries obtained by the International Ultraviolet Explorer (IUE) to evaluate if the observed behaviour of ξ Persei's DACs is reproduced. Testing three different models of spot size and strength, we find that the classical pattern of variability can be successfully reproduced for two of them: the model with the smallest spots yields absorption features that are incompatible with observations. Furthermore, we test the effect of the radial dependence of ionization levels on line driving, but cannot conclusively assess the importance of this factor. In conclusion, this study self-consistently links optical photometry and UV spectroscopy, paving the way to a better understanding of cyclical wind variability in massive stars in the context of the bright spot paradigm.

  20. Macrostatistical hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brenner, H.

    1992-01-01

    During the course of these efforts we have been studying suspension of particles in Newtonian and non-Newtonian liquids, embodying a combination of analysis, experiments, and numerical simulations. Experiments primarily involved tracking small balls as they fall slowly through otherwise quiescent suspensions of neutrally buoyant particles. Detailed trajectories of the balls, obtained either with new experimental techniques or by numerical simulation, were statistically interpreted in terms of the mean settling velocity and the dispersion about the mean. We showed that falling-ball rheometry, using small balls relative to the suspended particles, could be a means of measuring the macroscopic zero-shear-rate viscosity without significantly disturbing the original microstructure; therefore, falling-ball rheometry can be a powerful tool for use in studying the effects of microstructures on the macroscopic properties of suspensions. We plan to extend this work to the study of more complex, structured fluids, and to use other tools (e.g., rolling-ball rheometry) to study boundary effects. We also propose to study flowing suspensions to obtain non-zero-shear-rate viscosities. The intent is to develop an understanding of the basic principles needed to treat generic multiphase flow problems, through a detailed study of model systems. 8 refs.

  1. Electro-hydrodynamic generation of monodisperse nanoparticles in the sub-10 nm size range from strongly electrolytic salt solutions: governing parameters of scaling laws

    Energy Technology Data Exchange (ETDEWEB)

    Maisser, Anne, E-mail: a.maisser@tudelft.nl [Delft University of Technology (Netherlands); Attoui, Michel B. [LISA, UMR CNRS University Paris Est Creteil, University Paris-Diderot (France); Ganan-Calvo, Alfonso M. [Universidad de Sevilla, ESI (Spain); Szymanski, Wladyslaw W. [University of Vienna, Faculty of Physics (Austria)

    2013-01-15

    A charge reduced electro-hydrodynamic atomization (EHDA) device has been used to generate airborne salt clusters in the sub 10 nm size range. The focus of this study on that specific sub-micron range of electrospray droplets with relatively high electrical conductivities and permittivities aims to address the still existing controversy on the scaling laws of electrosprayed droplet diameters. In this study different concentrations of sodium chloride and potassium chloride-both show strong electrolytic behavior-have been electrosprayed from solutions in pure water, or from aqueous ammonium acetate buffer liquids of varying concentrations. The dry residue salt cluster diameter generated by the EHDA process have been measured using a differential mobility analyzer. The initial droplet diameter has been determined indirectly from the measured particle size following the steps of Chen et al. (J Aerosol Sci 26:963-977, 1995). Results have been compared to existing scaling laws valid for direct droplet measurements. They can be interpreted concisely on the basis of a realistic hypothesis on possible electrochemical effects taking place and affecting the droplet and thus nanoparticle formation in EHDA. The hypothesis developed in this work and the comparison with the experimental results are shown and discussed in the manuscript.

  2. Characterization of the optical constants and dispersion parameters of chalcogenide Te40Se30S30 thin film: thickness effect

    Science.gov (United States)

    Abd-Elrahman, M. I.; Hafiz, M. M.; Qasem, Ammar; Abdel-Rahim, M. A.

    2016-02-01

    Chalcogenide Te40Se30S30 thin films of different thickness (100-450 nm) are prepared by thermal evaporation of the Te40Se30S30 bulk. X-ray examination of the film shows some prominent peaks relate to crystalline phases indicating the crystallization process. The calculated particles of crystals from the X-ray diffraction peaks are found to be from 11 to 26 nm. As the thickness increases, the transmittance decreases and the reflectance increases. This could be attributed to the increment of the absorption of photons as more states will be available for absorbance in the case of thicker films. The decrease in the direct band gap with thickness is accompanied with an increase in energy of localized states. The obtained data for the refractive index could be fit to the dispersion model based on the single oscillator equation. The single-oscillator energy decreases, while the dispersion energy increases as the thickness increases.

  3. Characterization of optical constants and dispersion parameters of highly transparent Ge20Se76Sn4 amorphous thin film

    Science.gov (United States)

    Abd-Elrahman, M. I.; Hafiz, M. M.; Abdelraheem, A. M.; Abu-Sehly, A. A.

    2015-12-01

    Amorphous chalcogenide Ge20Se76Sn4 thin films of six different thicknesses (50-350 nm) are prepared by the thermal evaporation technique. Optical transmission and reflection spectra, in the wavelength range of the incident photons from 250 to 2500 nm, are used to study the effect of the film thickness on some optical properties. It is found that the effect of film thickness leads to increase in the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The decrease in optical band gap energy with increasing the film thickness is attributed to the formation of a band tail which narrows down the band gap. Dispersion analyses of refractive index reveal a decrease in the single-oscillator energy and an increase in the dispersion energy with increase in film thickness.

  4. Dispersion y dinamica poblacional

    Science.gov (United States)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  5. Precise determination of the f0(500) and f0(980) parameters in dispersive analysis of the pipi data

    CERN Document Server

    Kaminski, R; Pelaez, J R; de Elvira, J Ruiz

    2012-01-01

    We review the use of new and precise dispersive equations, which also implement crossing symmetry, in order to shed further light on the long-standing puzzle in the parameters of the f0(500), as well as the f0(980). This puzzle is finally being settled thanks to several analyses carried out during the last years. In this talk we show how our very recent dispersive data analysis allowed for a precise and model independent determination of the amplitudes for the S,P,D and F waves. In particular, we show how the analytic continuation of once subtracted dispersion relations for the S0 wave to the complex energy plane leads to very precise results for the f0(500) pole: sqrt(s)_pole = 457^(+14)_(-13) - i 279^(+11)_(-7) MeV and for the f0(980) pole: sqrt(s)_pole = 996+/-7 - i 25^(+10)_(-6) MeV. We also comment on how these results have been already used for other practical applications, including a refit of a previous model to the pipi S-wave amplitudes below 1000 MeV, which improves its consistency with the poles f...

  6. Linear Dispersion Relation and Depth Sensitivity to Swell Parameters: Application to Synthetic Aperture Radar Imaging and Bathymetry

    Directory of Open Access Journals (Sweden)

    Valentina Boccia

    2015-01-01

    Full Text Available Long gravity waves or swell dominating the sea surface is known to be very useful to estimate seabed morphology in coastal areas. The paper reviews the main phenomena related to swell waves propagation that allow seabed morphology to be sensed. The linear dispersion is analysed and an error budget model is developed to assess the achievable depth accuracy when Synthetic Aperture Radar (SAR data are used. The relevant issues and potentials of swell-based bathymetry by SAR are identified and discussed. This technique is of particular interest for characteristic regions of the Mediterranean Sea, such as in gulfs and relatively close areas, where traditional SAR-based bathymetric techniques, relying on strong tidal currents, are of limited practical utility.

  7. Linear dispersion relation and depth sensitivity to swell parameters: application to synthetic aperture radar imaging and bathymetry.

    Science.gov (United States)

    Boccia, Valentina; Renga, Alfredo; Rufino, Giancarlo; D'Errico, Marco; Moccia, Antonio; Aragno, Cesare; Zoffoli, Simona

    2015-01-01

    Long gravity waves or swell dominating the sea surface is known to be very useful to estimate seabed morphology in coastal areas. The paper reviews the main phenomena related to swell waves propagation that allow seabed morphology to be sensed. The linear dispersion is analysed and an error budget model is developed to assess the achievable depth accuracy when Synthetic Aperture Radar (SAR) data are used. The relevant issues and potentials of swell-based bathymetry by SAR are identified and discussed. This technique is of particular interest for characteristic regions of the Mediterranean Sea, such as in gulfs and relatively close areas, where traditional SAR-based bathymetric techniques, relying on strong tidal currents, are of limited practical utility.

  8. Hydrodynamic slip in silicon nanochannels

    Science.gov (United States)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-03-01

    Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.

  9. Precise determination of the f{sub 0}(500) and f{sub 0}(980) parameters in dispersive analysis of the ππ data

    Energy Technology Data Exchange (ETDEWEB)

    Kamiński, Robert, E-mail: robert.kaminski@ifj.edu.pl [Institute of Nuclear Physics PAN, Kraków (Poland); Garcia-Martin, R.; Pelaez, J.R.; Ruiz de Elvira, J. [Universidad Complutense de Madrid (Spain)

    2013-01-15

    Use of the new and precise dispersive equations with imposed crossing symmetry condition to solve the long-standing puzzle in the parameters of the f{sub 0}(500), as well as the f{sub 0}(980) is presented. This puzzle is finally being settled thanks to analyzes carried out during the last years [J. Beringer et al. (Particle Data Group), Phys. Rev. D86, (2012) 010001]. In this report we show how our very recent dispersive data analysis allowed for a precise and model independent determination of the amplitudes for the S, P, D and F waves [R. Garcia-Martin, R. Kaminski, J. R. Pelaez, J. Ruiz de Elvira and F.J. Yndurain, Phys. Rev. D83, (2011) 074004; R. Garcia-Martin, R. Kamiński, J.R. Pelaez and J. Ruiz de Elvira, Phys. Rev. Lett. 107, (2011) 072001; R. Kamiński, Phys. Rev. D83, (2011) 076008]. Especially we present that the analytic continuation of once subtracted dispersion relations for the S 0 wave to the complex energy plane leads to very precise results for the f{sub 0}(500) pole: √(s{sub pole})=457{sub −13}{sup +14}−i279{sub −7}{sup +11} MeV and for the f{sub 0}(980) pole: √(s{sub pole})=996±7−i25{sub −6}{sup +10}MeV. We also mention on first (or one of the first) practical application of presented dispersion relations in refitting and in significant improving of the ππ S-wave amplitudes below 1000 MeV.

  10. Hydrodynamics of sediment threshold

    Science.gov (United States)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  11. Fish stocking density impacts tank hydrodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Michael R.; Lunger, Angela; Laursen, Jesper;

    2006-01-01

    hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3......The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank...

  12. Elasto-hydrodynamic lubrication

    CERN Document Server

    Dowson, D; Hopkins, D W

    1977-01-01

    Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented.Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussio

  13. Elementary classical hydrodynamics

    CERN Document Server

    Chirgwin, B H; Langford, W J; Maxwell, E A; Plumpton, C

    1967-01-01

    Elementary Classical Hydrodynamics deals with the fundamental principles of elementary classical hydrodynamics, with emphasis on the mechanics of inviscid fluids. Topics covered by this book include direct use of the equations of hydrodynamics, potential flows, two-dimensional fluid motion, waves in liquids, and compressible flows. Some general theorems such as Bernoulli's equation are also considered. This book is comprised of six chapters and begins by introducing the reader to the fundamental principles of fluid hydrodynamics, with emphasis on ways of studying the motion of a fluid. Basic c

  14. Use of surfactants as plasticizers in preparing solid dispersions of poorly soluble API: selection of polymer-surfactant combinations using solubility parameters and testing the processability.

    Science.gov (United States)

    Ghebremeskel, Alazar N; Vemavarapu, Chandra; Lodaya, Mayur

    2007-01-10

    Formation of solid dispersions as a means to enhance the dissolution rate of poorly soluble Active pharmaceutical ingredients (APIs) typically employs hydrophilic polymer systems and surfactants. While the utility of the surfactant systems in solubilization is well known, the secondary effects of the same on processing and subsequent physical stability of the solid dispersions needs to be studied further. Physical blends of the poorly soluble API and hydrophilic polymers such as PVP-K30, Plasdone-S630, HPMC-E5, HPMCAS, and Eudragit L100 with mass ratio 1:1 were prepared. The surfactants tested in this study included Tween-80, Docusate sodium, Myrj-52, Pluronic-F68 and SLS. Thermal analysis of the API-polymer-surfactant blends suggested that the surfactants caused solvation/plasticization, manifesting in reduction of (i) the melting (T(m)) of API (ii) T(g) of the polymers and (iii) the combined T(g) of the solid dispersion formed from quench cooling. Explanation of these effects of surfactants is attempted based on their physical state (at the temperature of interest), HLB values and similarity of their solubility parameter values with respect to drug-polymer systems. Furthermore, extruded matrices containing different API-polymer (PVP-K30, Plasdone-S630, and HPMC-E5) mixtures prepared with and without surfactants, were produced by feeding the powder blend through a hot-melt extruder. The melt viscosity of the polymer blends was assessed by torque rheometry using a Haake Rheomix. The physicochemical properties of the extruded API-polymer-surfactant were characterized by differential scanning calorimetry, X-ray diffraction, Raman spectroscopy, and polarized microscopy. The results demonstrated that the glass transition temperature of the carrier polymers decreased as direct result of the surfactants in the extrudate, due to an increase in the chain mobility of polymers. A decrease in the melt viscosity was seen due to a plasticization of the polymer. The drug release

  15. Evaluating Chemical Dispersant Efficacy In An Experimental Wave Tank: 1, Dispersant Effectiveness As A Function Of Energy Dissipation Rate

    Science.gov (United States)

    Numerous laboratory test systems have been developed for the comparison of efficacy between various chemical oil dispersant formulations. However, for the assessment of chemical dispersant effectiveness under realistic sea state, test protocols are required to produce hydrodynam...

  16. Investigation and correlation of physical stability, dissolution behaviour and interaction parameter of amorphous solid dispersions of telmisartan: a drug development perspective.

    Science.gov (United States)

    Dukeck, R; Sieger, P; Karmwar, P

    2013-07-16

    The aim of this study was to investigate if amorphous solid dispersions of telmisartan, prepared in presence of different polymers, exhibit different structural and thermodynamic characteristics and whether these differences can be correlated to their physical stability (time to crystallisation) and dissolution behaviour. Amorphous samples were prepared by melt quenching. The resulting amorphous materials were characterised using X-ray diffraction, Raman spectroscopy and differential scanning calorimetry. All freshly prepared samples were completely X-ray amorphous (with a halo being the only feature in the diffractograms). The shape of the halos in the diffractograms varied suggesting structural variations in the near order of the molecules between the different amorphous solid dispersions (ASDs). Principal component analysis of the Raman spectra of the various ASD revealed that the samples clustered in the scores plot, again suggesting structural differences due to the presence of different drug-polymer interaction. The ranking of the samples with respect to physical stability and interaction parameter was: ASD of telmisartan:eudragit>ASD of telmisartan:soluplus>ASD of telmisartan:HPMC>ASD of telmisartan:PVP>amorphous telmisartan. The interaction parameter, calculated by using the Flory Huggins theory, showed a good correlation with the experimentally determined stability whereas a weak correlation was found with dissolution behaviour of different ASD. This study showed that correlation of physical stability and dissolution behaviour with calculated interaction parameter is possible for the same amorphous systems prepared by using different polymers. This could aid in selecting the most appropriate polymer for the development of optimised formulations containing amorphous drugs. It can be concluded that ASD prepared by using different polymers have different structural and thermal properties. These differences affect the physical stability and dissolution

  17. Determination of Hydrodynamic Parameters on Two--Phase Flow Gas - Liquid in Pipes with Different Inclination Angles Using Image Processing Algorithm

    Science.gov (United States)

    Montoya, Gustavo; Valecillos, María; Romero, Carlos; Gonzáles, Dosinda

    2009-11-01

    In the present research a digital image processing-based automated algorithm was developed in order to determine the phase's height, hold up, and statistical distribution of the drop size in a two-phase system water-air using pipes with 0 , 10 , and 90 of inclination. Digital images were acquired with a high speed camera (up to 4500fps), using an equipment that consist of a system with three acrylic pipes with diameters of 1.905, 3.175, and 4.445 cm. Each pipe is arranged in two sections of 8 m of length. Various flow patterns were visualized for different superficial velocities of water and air. Finally, using the image processing program designed in Matlab/Simulink^, the captured images were processed to establish the parameters previously mentioned. The image processing algorithm is based in the frequency domain analysis of the source pictures, which allows to find the phase as the edge between the water and air, through a Sobel filter that extracts the high frequency components of the image. The drop size was found using the calculation of the Feret diameter. Three flow patterns were observed: Annular, ST, and ST&MI.

  18. Dispersive shock waves with nonlocal nonlinearity

    CERN Document Server

    Barsi, Christopher; Sun, Can; Fleischer, Jason W

    2007-01-01

    We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

  19. Dispersive shock waves with nonlocal nonlinearity.

    Science.gov (United States)

    Barsi, Christopher; Wan, Wenjie; Sun, Can; Fleischer, Jason W

    2007-10-15

    We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

  20. Quasiparticle anisotropic hydrodynamics

    CERN Document Server

    Alqahtani, Mubarak

    2016-01-01

    We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.

  1. Prediction of dosage-based parameters from the puff dispersion of airborne materials in urban environments using the CFD-RANS methodology

    Science.gov (United States)

    Efthimiou, G. C.; Andronopoulos, S.; Bartzis, J. G.

    2017-02-01

    One of the key issues of recent research on the dispersion inside complex urban environments is the ability to predict dosage-based parameters from the puff release of an airborne material from a point source in the atmospheric boundary layer inside the built-up area. The present work addresses the question of whether the computational fluid dynamics (CFD)-Reynolds-averaged Navier-Stokes (RANS) methodology can be used to predict ensemble-average dosage-based parameters that are related with the puff dispersion. RANS simulations with the ADREA-HF code were, therefore, performed, where a single puff was released in each case. The present method is validated against the data sets from two wind-tunnel experiments. In each experiment, more than 200 puffs were released from which ensemble-averaged dosage-based parameters were calculated and compared to the model's predictions. The performance of the model was evaluated using scatter plots and three validation metrics: fractional bias, normalized mean square error, and factor of two. The model presented a better performance for the temporal parameters (i.e., ensemble-average times of puff arrival, peak, leaving, duration, ascent, and descent) than for the ensemble-average dosage and peak concentration. The majority of the obtained values of validation metrics were inside established acceptance limits. Based on the obtained model performance indices, the CFD-RANS methodology as implemented in the code ADREA-HF is able to predict the ensemble-average temporal quantities related to transient emissions of airborne material in urban areas within the range of the model performance acceptance criteria established in the literature. The CFD-RANS methodology as implemented in the code ADREA-HF is also able to predict the ensemble-average dosage, but the dosage results should be treated with some caution; as in one case, the observed ensemble-average dosage was under-estimated slightly more than the acceptance criteria. Ensemble

  2. Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

    Directory of Open Access Journals (Sweden)

    Suvachittanont Sirikalaya

    2011-01-01

    Full Text Available Abstract Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25 dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl and divalent (MgCl2 inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure.

  3. Hydrodynamic Analysis to Process of Hydrostatic Extrusion for Tungsten Alloy

    Institute of Scientific and Technical Information of China (English)

    Fuchi WANG; Zhaohui ZHANG; Shukui LI

    2001-01-01

    The hydrodynamic analysis to the process of the hydrostatic extrusion for tungsten alloy is carried through the hydrodynamic lubrication theory and Reynolds equation in this paper. The critical velocity equation when the hydrodynamic lubrication conditions appear between the surfaces of the work- piece and the die is obtained, and the relationship between the critical velocity and the extrusion parameters is discussed, which build the theoretical bases to the application of the hydrostatic extrusion for tungsten alloy.

  4. Hydrodynamics and black holes

    CERN Document Server

    Oz, Yaron

    2015-01-01

    This chapter describes how the AdS/CFT correspondence (the Holographic Principle) relates field theory hydrodynamics to perturbations of black hole (brane) gravitational backgrounds. The hydrodynamics framework is first presented from the field theory point of view, after which the dual gravitational description is outlined, first for relativistic fluids and then for the nonrelativistic case. Further details of the fluid/gravity correspondence are then discussed, including the bulk geometry and the dynamics of the black hole horizon.

  5. Response of runoff-induced sediment discharge to hydrodynamic parameters of rill on loess hillslope%黄土坡面细沟径流输沙对水动力学参数的响应

    Institute of Scientific and Technical Information of China (English)

    谭贞学; 王占礼; 刘俊娥; 袁殷; 陈浩; 王莎; 申楠; 焦念

    2011-01-01

    细沟径流输沙是细沟侵蚀产沙的重要过程,阐明细沟径流输沙与水动力学参数之间的关系可以有效地揭示细沟径流输沙的动力学机制,并为建立细沟侵蚀过程物理模型奠定基础.采用具有定流量人工放水的组合小区模拟降雨试验,研究黄土坡面细沟径流输沙对水动力学参数的响应关系.结果表明:1)一次降雨径流产生的细沟输沙模数对水动力学参数平均值响应关系大小顺序为平均水流断面单位能量(R=0.99)>平均水流功率(R=0.88)>平均水流切应力(R=0.82)>平均单位水流功率(R=0.76);2)降雨径流过程中,细沟输沙率对水动力学参数瞬时值响应关系为水流切应力(R=0.88)>水流功率(R=0.47),水流断面单位能量和单位水流功率的相关性较差,细沟输沙率对水流切应力的响应关系呈幂函数方程关系.%Runoff-induced sediment discharge is one of the most important process of erosion and sediment yield. It is important to clarify the relationships of runoff-induced sediment discharge and hydrodynamic parameters of rill flow on loess hillslope. In this paper, the relationships were studied by experiment of simulated rainfall and constant flow using group plots. Results showed that: 1 ) In single rainfall-runoff event, the response of sediment transport modulus to mean hydrodynamic parameters was given as follows: mean unit energy ( R = 0. 99) > mean stream power ( R = 0. 88) > mean stream shear stress ( R = 0. 82 ) > mean unit stream power ( R = 0. 76 ). 2) During the rainfall-runoff process, theresponse of the sediment transport rate to stream shear stress ( R = 0. 88) was greater than stream power ( R = 0. 47) , and the correlations of sediment transport rate with unit energy and with unit stream power were weak. The relationship of stream shear stress and the sediment transport rate could be expressed by power functions.

  6. Hydrodynamic dispersion and hyporheic exchange in a small urban stream%城市小型河流水动力弥散和潜流交换过程

    Institute of Scientific and Technical Information of China (English)

    于靖; 张华

    2015-01-01

    为研究城市小型河流中污染物的物理迁移过程规律, 分析基流条件下流动水体与暂态存储区之间的滞留交互作用, 采用溴化锂( LiBr )作为保守性示踪剂进行野外现场示踪试验, 结合一维溶质运移存储模型( One-dimensional Transport with Inflow and Storage model, OTIS)定量解析潜流交换特性, 估算纵向弥散系数( D)、 潜流交换面积( As )、 主河道断面面积( A)和潜流交换系数(α). 模型度量指标DaI值和均方根误差值结果表征参数模拟结果可靠性高, 拟合效果理想. 由泵入点O至下游1 300 m设置的A、 B、 C、 D 4处监测点的模拟结果表明, 水文参数D、 As、 A和α均随水文条件而变, OB河段(0~600 m)潜流交换能力较弱, 主要以对流弥散过程为主; BD河段( 600~1 300 m)具有较强的暂态存储能力, 对溶质的滞留时间长; BC( 600~1 000 m)和CD( 1 000~1 300 m)河段交换系数分别为 (3. 42×10-6±0. 65×10-6) s-1和 (2. 87×10-6±0. 81×10-6) s-1; 河段BC存在2. 2×10-5m3/(s·m)的侧向补给流量. 4个河段对比发现, 城市河流渠道化、 河床沉积物贫瘠等特征导致潜流交换能力弱化.%To reveal the physical transport processes in a small urban stream and analyze exchange processes between water column and transient storage zone under base flow, field experiment using LiBr as conservative tracer and nu-merical simulation using One-dimensional Transport with Inflow and Storage model ( OTIS) were carried out to quanti-tatively characterize hyporheic exchange. The longitudinal dispersion coefficient ( D) reach-scale transient storage area (AS), main channel cross section area (A), and the hyporheic exchange coefficient (α) were estimated along a 1 300 m stream reach. Transient storage metrics DaI and ERMS values showed an excellent fit of the model. The results of four stations ( A, B, C and D ) downstream the location of tracer injection demonstrated that hydrological parameters D

  7. Hydrodynamic Modeling and Its Application in AUC.

    Science.gov (United States)

    Rocco, Mattia; Byron, Olwyn

    2015-01-01

    The hydrodynamic parameters measured in an AUC experiment, s(20,w) and D(t)(20,w)(0), can be used to gain information on the solution structure of (bio)macromolecules and their assemblies. This entails comparing the measured parameters with those that can be computed from usually "dry" structures by "hydrodynamic modeling." In this chapter, we will first briefly put hydrodynamic modeling in perspective and present the basic physics behind it as implemented in the most commonly used methods. The important "hydration" issue is also touched upon, and the distinction between rigid bodies versus those for which flexibility must be considered in the modeling process is then made. The available hydrodynamic modeling/computation programs, HYDROPRO, BEST, SoMo, AtoB, and Zeno, the latter four all implemented within the US-SOMO suite, are described and their performance evaluated. Finally, some literature examples are presented to illustrate the potential applications of hydrodynamics in the expanding field of multiresolution modeling.

  8. Physical parameters of late M-type members of Chamaeleon I and TW Hydrae Association: dust settling, age dispersion and activity

    Science.gov (United States)

    Bayo, A.; Barrado, D.; Allard, F.; Henning, T.; Comerón, F.; Morales-Calderón, M.; Rajpurohit, A. S.; Peña Ramírez, K.; Beamín, J. C.

    2017-02-01

    Although mid-to-late type M dwarfs are the most common stars in our stellar neighbourhood, our knowledge of these objects is still limited. Open questions include the evolution of their angular momentum, internal structures, dust settling in their atmospheres and age dispersion within populations. In addition, at young ages, late-type Ms have masses below the hydrogen burning limit and therefore are key objects in the debate on the brown dwarf mechanism of formation. In this work, we determine and study in detail the physical parameters of two samples of young, late M-type sources belonging to either the Chamaeleon I dark cloud or the TW Hydrae Association and compare them with the results obtained in the literature for other young clusters and also for older, field, dwarfs. We used multiwavelength photometry to construct and analyse SEDs to determine general properties of the photosphere and disc presence. We also used low-resolution optical and near-infrared spectroscopy to study activity, accretion, gravity and effective temperature sensitive indicators. We propose a Virtual Observatory-based spectral index that is both temperature and age sensitive. We derived physical parameters using independent techniques confirming the already common feature/problem of the age/luminosity spread. In particular, we highlight two brown dwarfs showing very similar temperatures but clearly different surface gravity (explained invoking extreme early accretion). We also show how, despite large improvement in the dust treatment in theoretical models, there is still room for further progress in the simultaneous reproduction of the optical and near-infrared features of these cold young objects.

  9. Hydrodynamic alignment and assembly of nanofibrils resulting in strong cellulose filaments

    Science.gov (United States)

    Håkansson, Karl M. O.; Fall, Andreas B.; Lundell, Fredrik; Yu, Shun; Krywka, Christina; Roth, Stephan V.; Santoro, Gonzalo; Kvick, Mathias; Prahl Wittberg, Lisa; Wågberg, Lars; Söderberg, L. Daniel

    2014-06-01

    Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. In order to achieve good properties of these materials, the nanostructure must be controlled. Here we present a process combining hydrodynamic alignment with a dispersion-gel transition that produces homogeneous and smooth filaments from a low-concentration dispersion of cellulose nanofibrils in water. The preferential fibril orientation along the filament direction can be controlled by the process parameters. The specific ultimate strength is considerably higher than previously reported filaments made of cellulose nanofibrils. The strength is even in line with the strongest cellulose pulp fibres extracted from wood with the same degree of fibril alignment. Successful nanoscale alignment before gelation demands a proper separation of the timescales involved. Somewhat surprisingly, the device must not be too small if this is to be achieved.

  10. Optical dispersion parameters and stability of poly (9, 9‧-di-n-octylfluorenyl-2.7-diyl)/ZnO nanohybrid films: towards organic photovoltaic applications

    Science.gov (United States)

    El-Bashir, S. M.; Alenazi, W. K.; AlSalhi, M. S.

    2017-02-01

    Conjugated polymer nanohybrid films were prepared from poly (9,9‧-di-n-octylfluorenyl-2.7-diyl) (PFO) and zinc oxide (ZnO) nanoparticles. ZnO nanopowder was prepared by the solgel method, different ratios of PFO/ZnO nanohybrids have been prepared using solution blending method. Then, the blends were spin-coated onto glass substrates at 2000 rpm for 1 min. and subsequently dried at room temperature. XRD and TEM were used to determine the structural properties, while UV–Vis and photoluminescence spectrophotometers were employed to investigate the optical properties of the films. The spectral distribution of specular reflectance were used to calculate the refractive index n (λ) and the optical dispersion parameters were determined according to Wemple and Didomenico (WD) model. The effect of ZnO NPs on the direct and indirect band gap energies, photo- and thermal stability was also discussed. A significant enhancement in the light emitting properties has been observed by increasing the concentration of ZnO NPs.

  11. Physical parameters of late M-type members of Chamaleon I and TW Hydrae Association: Dust settling, age dispersion and activity

    CERN Document Server

    Bayo, A; Allard, F; Henning, T; Comeron, F; Morales-Calderon, M; Rajpurohit, A S; Ramırez, K Pena; Beamın, J C

    2016-01-01

    Although mid-to-late type M dwarfs are the most common stars in our stellar neighborhood, our knowledge of these objects is still limited. Open questions include the evolution of their angular momentum, internal structures, dust settling in their atmospheres, age dispersion within populations. In addition, at young ages, late-type Ms have masses below the hydrogen burning limit and therefore are key objects in the debate on the brown dwarf mechanism of formation. In this work we determine and study in detail the physical parameters of two samples of young, late M-type sources belonging to either the Chamaeleon I Dark Cloud or the TW Hydrae Association and compare them with the results obtained in the literature for other young clusters and also for older, field, dwarfs. We used multi-wavelength photometry to construct and analyze SEDs to determine general properties of the photosphere and disk presence. We also used low resolution optical and near-infrared spectroscopy to study activity, accretion, gravity an...

  12. Dispersive shock waves and modulation theory

    Science.gov (United States)

    El, G. A.; Hoefer, M. A.

    2016-10-01

    There is growing physical and mathematical interest in the hydrodynamics of dissipationless/dispersive media. Since G.B. Whitham's seminal publication fifty years ago that ushered in the mathematical study of dispersive hydrodynamics, there has been a significant body of work in this area. However, there has been no comprehensive survey of the field of dispersive hydrodynamics. Utilizing Whitham's averaging theory as the primary mathematical tool, we review the rich mathematical developments over the past fifty years with an emphasis on physical applications. The fundamental, large scale, coherent excitation in dispersive hydrodynamic systems is an expanding, oscillatory dispersive shock wave or DSW. Both the macroscopic and microscopic properties of DSWs are analyzed in detail within the context of the universal, integrable, and foundational models for uni-directional (Korteweg-de Vries equation) and bi-directional (Nonlinear Schrödinger equation) dispersive hydrodynamics. A DSW fitting procedure that does not rely upon integrable structure yet reveals important macroscopic DSW properties is described. DSW theory is then applied to a number of physical applications: superfluids, nonlinear optics, geophysics, and fluid dynamics. Finally, we survey some of the more recent developments including non-classical DSWs, DSW interactions, DSWs in perturbed and inhomogeneous environments, and two-dimensional, oblique DSWs.

  13. Axial dispersion in flowing red blood cell suspensions

    Science.gov (United States)

    Podgorski, Thomas; Losserand, Sylvain; Coupier, Gwennou

    2016-11-01

    A key parameter in blood microcirculation is the transit time of red blood cells (RBCs) through an organ, which can influence the efficiency of gas exchange and oxygen availability. A large dispersion of this transit time is observed in vivo and is partly due to the axial dispersion in the flowing suspension. In the classic Taylor-Aris example of a solute flowing in a tube, the combination of molecular diffusion and parabolic velocity profile leads to enhanced axial dispersion. In suspensions of non-Brownian deformable bodies such as RBCs, axial dispersion is governed by a combination of shear induced migration and shear-induced diffusion arising from hydrodynamic interactions. We revisit this problem in the case of RBC pulses flowing in a microchannel and show that the axial dispersion of the pulse eventually saturates with a final extension that depends directly on RBC mechanical properties. The result is especially interesting in the dilute limit since the final pulse length depends only on the channel width, exponent of the migration law and dimensionless migration velocity. In continuous flow, the dispersion of transit times is the result of complex cell-cell and cell-wall interactions and is strongy influenced by the polydispersity of the blood sample. The authors acknowledge support from LabEx TEC21 and CNES.

  14. Pulsing frequency induced change in optical constants and dispersion energy parameters of WO{sub 3} films grown by pulsed direct current magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Punitha, K. [Department of Physics, Alagappa University, Karaikudi 630 004 (India); Sivakumar, R., E-mail: krsivakumar1979@yahoo.com [Directorate of Distance Education, Alagappa University, Karaikudi 630 004 (India); Sanjeeviraja, C. [Department of Physics, Alagappa Chettiar College of Engineering and Technology, Karaikudi 630 004 (India)

    2014-03-21

    In this work, we present the pulsing frequency induced change in the structural, optical, vibrational, and luminescence properties of tungsten oxide (WO{sub 3}) thin films deposited on microscopic glass and fluorine doped tin oxide (SnO{sub 2}:F) coated glass substrates by pulsed dc magnetron sputtering technique. The WO{sub 3} films deposited on SnO{sub 2}:F substrate belongs to monoclinic phase. The pulsing frequency has a significant influence on the preferred orientation and crystallinity of WO{sub 3} film. The maximum optical transmittance of 85% was observed for the film and the slight shift in transmission threshold towards higher wavelength region with increasing pulsing frequency revealed the systematic reduction in optical energy band gap (3.78 to 3.13 eV) of the films. The refractive index (n) of films are found to decrease (1.832 to 1.333 at 550 nm) with increasing pulsing frequency and the average value of extinction coefficient (k) is in the order of 10{sup −3}. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (E{sub d}) parameters, dielectric constants, plasma frequency, oscillator strength, and oscillator energy (E{sub o}) of WO{sub 3} films were calculated and reported for the first time due to variation in pulsing frequency during deposition by pulsed dc magnetron sputtering. The E{sub o} is change between 6.30 and 3.88 eV, while the E{sub d} varies from 25.81 to 7.88 eV, with pulsing frequency. The Raman peak observed at 1095 cm{sup −1} attributes the presence of W-O symmetric stretching vibration. The slight shift in photoluminescence band is attributed to the difference in excitons transition. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  15. Anisotropic hydrodynamics -- basic concepts

    CERN Document Server

    Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael

    2013-01-01

    Due to the rapid longitudinal expansion of the quark-gluon plasma created in relativistic heavy ion collisions, potentially large local rest frame momentum-space anisotropies are generated. The magnitude of these momentum-space anisotropies can be so large as to violate the central assumption of canonical viscous hydrodynamical treatments which linearize around an isotropic background. In order to better describe the early-time dynamics of the quark gluon plasma, one can consider instead expanding around a locally anisotropic background which results in a dynamical framework called anisotropic hydrodynamics. In this proceedings contribution we review the basic concepts of the anisotropic hydrodynamics framework presenting viewpoints from both the phenomenological and microscopic points of view.

  16. First Numerical Simulations of Anomalous Hydrodynamics

    CERN Document Server

    Hongo, Masaru; Hirano, Tetsufumi

    2013-01-01

    Anomalous hydrodynamics is a low-energy effective theory that captures effects of quantum anomalies. We develop a numerical code of anomalous hydrodynamics and apply it to dynamics of heavy-ion collisions, where anomalous transports are expected to occur. This is the first attempt to perform fully non-linear numerical simulations of anomalous hydrodynamics. We discuss implications of the simulations for possible experimental observations of anomalous transport effects. From analyses of the charge-dependent elliptic flow parameters ($v_2^\\pm$) as a function of the net charge asymmetry $A_\\pm$, we quantitatively verify that the linear dependence of $\\Delta v_2 \\equiv v_2^- - v_2^+$ on the net charge asymmetry $A_\\pm$ cannot be regarded as a sensitive signal of anomalous transports, contrary to previous studies. We, however, find that the intercept $\\Delta v_2(A_\\pm=0)$ is sensitive to anomalous transport effects.

  17. Hydrodynamics, resurgence and trans-asymptotics

    CERN Document Server

    Basar, Gokce

    2015-01-01

    The second-order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost- invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the non-hydrodynamic modes that are exponentially suppressed at late times, analogous to the quasi-normal-modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semi-classical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these non-hydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with init...

  18. Anisotropic hydrodynamics for conformal Gubser flow

    Energy Technology Data Exchange (ETDEWEB)

    Strickland, Michael; Nopoush, Mohammad [Kent State University, Kent OH 44242 (United States); Ryblewski, Radoslaw [The H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland)

    2016-12-15

    In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3){sub q} symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.

  19. Smoothed Particle Hydrodynamic Simulator

    Energy Technology Data Exchange (ETDEWEB)

    2016-10-05

    This code is a highly modular framework for developing smoothed particle hydrodynamic (SPH) simulations running on parallel platforms. The compartmentalization of the code allows for rapid development of new SPH applications and modifications of existing algorithms. The compartmentalization also allows changes in one part of the code used by many applications to instantly be made available to all applications.

  20. Hydrodynamic aspect of caves

    Directory of Open Access Journals (Sweden)

    Franci Gabrovsek

    2008-01-01

    Full Text Available From a hydrological point of view, active caves are a series of connected conduits which drain water through an aquifer. Water tends to choose the easiest way through the system but different geological and morphological barriers act as flow restrictions. The number and characteristics of restrictions depends on the particular speleogenetic environment, which is a function of geological, geomorphological, climatological and hydrological settings. Such a variety and heterogeneity of underground systems has presented a challenge for human understanding for many centuries. Access to many underground passages, theoretical knowledge and recent methods (modeling, water pressure-resistant dataloggers, precise sensors etc. give us the opportunity to get better insight into the hydrodynamic aspect of caves. In our work we tried to approach underground hydrodynamics from both theoretical and practical points of view. We present some theoretical background of open surface and pressurized flow in underground rivers and present results of some possible scenarios. Moreover, two case studies from the Ljubljanica river basin are presented in more detail: the cave system between Planinsko polje and Ljubljansko barje, and the cave system between Bloško polje and Cerkniško polje. The approach and methodology in each case is somewhat different, as the aims were different at the beginning of exploration. However, they both deal with temporal and spatial hydrodynamics of underground waters. In the case of Bloško polje-Cerkniško polje system we also explain the feedback loop between hydrodynamics and Holocene speleogenesis.

  1. 基于喷管结构参数公差的纵向距离散布%Longitudinal Distant Dispersion Based on Tolerance of Nozzle Structure Parameters

    Institute of Scientific and Technical Information of China (English)

    封锋; 骆晓臣; 陈军

    2015-01-01

    The specific impulse is a comprehensive factor to evaluate the energy characteristics of solid rocket engine (SRE),and it affects the range of rocket greatly.It is relevant to the solid rocket propellant formulations and determined by the design parameters of SRE.The design pa-rameters of long-distance rocket TG-300 engine were used to discuss the effects of manufacturing tolerance from throat diameter,expansion cone half angle and expansion ratio on the dispersions of specific impulse and longitudinal distance.The results show that the effect of manufacturing tolerance from throat diameter on specific impulse is greatest,and the effect of tolerance from ex-pansion cone half angle takes the second place,and the effect of tolerance from expansion ratio is minor.The tolerance discussed in present paper should be controlled rationally in manufacture process,and the results obtained by current paper offer reference for structure design of SRE.%比冲是评价固体火箭发动机能量特性的综合因子,其与固体推进剂配方组成及发动机设计参数有关,对射程具有较大的影响。该文结合某远程TG-300发动机结构参数,针对喷管喉径、扩张半角和膨胀比的制造公差,研究了这些参数对比冲散布及纵向距离散布的影响。结果表明,喷管喉径制造公差对比冲的影响相对较大,扩张半角次之,膨胀比的制造公差对比冲影响较小;这些公差应当在加工过程中合理控制。该文所得结果可对固体火箭发动机结构设计提供参考依据。

  2. Hydrodynamics of the Dirac spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yizhuang, E-mail: yizhuang.liu@stonybrook.edu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Warchoł, Piotr, E-mail: piotr.warchol@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, PL-30348 Krakow (Poland); Zahed, Ismail, E-mail: ismail.zahed@stonybrook.edu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2016-02-10

    We discuss a hydrodynamical description of the eigenvalues of the Dirac spectrum in even dimensions in the vacuum and in the large N (volume) limit. The linearized hydrodynamics supports sound waves. The hydrodynamical relaxation of the eigenvalues is captured by a hydrodynamical (tunneling) minimum configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of unbroken chiral symmetry to a phase of broken chiral symmetry occurs over a time set by the speed of sound.

  3. Wave dispersion of carbon nanotubes conveying fluid supported on linear viscoelastic two-parameter foundation including thermal and small-scale effects

    Science.gov (United States)

    Sina, Nima; Moosavi, Hassan; Aghaei, Hosein; Afrand, Masoud; Wongwises, Somchai

    2017-01-01

    In this paper, for the first time, a nonlocal Timoshenko beam model is employed for studying the wave dispersion of a fluid-conveying single-walled carbon nanotube on Viscoelastic Pasternak foundation under high and low temperature change. In addition, the phase and group velocity for the nanotube are discussed, respectively. The influences of Winkler and Pasternak modulus, homogenous temperature change, steady flow velocity and damping factor of viscoelastic foundation on wave dispersion of carbon nanotubes are investigated. It was observed that the characteristic of the wave for carbon nanotubes conveying fluid is the normal dispersion. Moreover, implying viscoelastic foundation leads to increasing the wave frequencies.

  4. Experimental Study on Variation Process of the Hydrodynamic Parameters in Inland Shallow Salt Water Area%内陆浅层咸水区水动力参数变异过程试验研究

    Institute of Scientific and Technical Information of China (English)

    邢立亭; 王立艳; 张世杰; 黄林显

    2015-01-01

    选取鲁北平原区浅层粉土、浅层咸水和大气降水为供试材料,进行室内雨水-咸水驱替试验,研究驱替过程中的含水介质渗透性变化特征,探讨内陆浅层咸水区水动力、水文地球化学过程对水文地质参数变异影响。试验结果表明:雨水驱替咸水饱和土柱过程中,盐分突变,渗透系数由开始的6.49×10-4 cm/s 最终降至2.28×10-4 cm/s ,并维持相对稳定;第188 d后,咸水再次驱替土柱,且完全穿透土柱后,含水介质孔隙度由开始的43.02%大约降至39.73%;在雨水驱替过程中,水温变化对渗透系数波动性变化的影响较为显著。研究认为,内陆咸水区含水介质黏土矿物含量高,黏粒大量膨胀和释放、扩散及Ca/Mg -Na的离子交换作用引起孔隙度降低是造成含水介质的渗透性下降的主因,咸雨水驱替过程中渗透性的变化具有不可逆性。含水介质水文地质参数的变异对于内陆浅层咸水形成和演化有重要影响。%Shallow silt ,shallow salt water and atmospheric precipitation are selected as materials collected from the North Shandong Plains .The variation characteristics of permeability of aquifer medium are studied by rain-saltwater displacement experiment in labo‐ratory ,further ,mechanisms are explored how hydrodynamic and hydrogeochemical processes affect the variation of hydrogeological parameters in inland shallow saltwater region .The experimental results show that :in the first stage using rainwater to displace the salt water in saturated soil column ,salinity has dramatically changed ,and the permeability has finally dropped 2 .28 × 10-4 cm/s from the initial value 6 .49 × 10-4 cm/s then maintaining a relatively stable value;after 188 days ,in the second stage using salt water as supply and adequately penetrating the soil column ,aquifer medium porosity by the start 43 .02% fell to 39 .73% ;during the process of

  5. Relativistic Hydrodynamics with Wavelets

    CERN Document Server

    DeBuhr, Jackson; Anderson, Matthew; Neilsen, David; Hirschmann, Eric W

    2015-01-01

    Methods to solve the relativistic hydrodynamic equations are a key computational kernel in a large number of astrophysics simulations and are crucial to understanding the electromagnetic signals that originate from the merger of astrophysical compact objects. Because of the many physical length scales present when simulating such mergers, these methods must be highly adaptive and capable of automatically resolving numerous localized features and instabilities that emerge throughout the computational domain across many temporal scales. While this has been historically accomplished with adaptive mesh refinement (AMR) based methods, alternatives based on wavelet bases and the wavelet transformation have recently achieved significant success in adaptive representation for advanced engineering applications. This work presents a new method for the integration of the relativistic hydrodynamic equations using iterated interpolating wavelets and introduces a highly adaptive implementation for multidimensional simulati...

  6. Burst Mechanisms in Hydrodynamics

    CERN Document Server

    Knobloch, E

    1999-01-01

    Different mechanisms believed to be responsible for the generation of bursts in hydrodynamical systems are reviewed and a new mechanism capable of generating regular or irregular bursts of large dynamic range near threshold is described. The new mechanism is present in the interaction between oscillatory modes of odd and even parity in systems of large but finite aspect ratio, and provides an explanation for the bursting behavior observed in binary fluid convection. Additional applications of the new mechanism are proposed.

  7. Relativistic cosmological hydrodynamics

    CERN Document Server

    Hwang, J

    1997-01-01

    We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.

  8. Hydrodynamics of fossil fishes.

    Science.gov (United States)

    Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert

    2014-08-07

    From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.

  9. Porous media grain size distribution and hydrodynamic forces effects on transport and deposition of suspended particles.

    Science.gov (United States)

    Ahfir, Nasre-Dine; Hammadi, Ahmed; Alem, Abdellah; Wang, HuaQing; Le Bras, Gilbert; Ouahbi, Tariq

    2017-03-01

    The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles (2-30μm) and Fluorescein (dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand, Coarse sand, and a third sand (Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection-dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance. A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining. Copyright © 2016. Published by Elsevier B.V.

  10. Application of 3D hydrodynamic and particle tracking models for better environmental management of finfish culture

    Science.gov (United States)

    Moreno Navas, Juan; Telfer, Trevor C.; Ross, Lindsay G.

    2011-04-01

    Hydrographic conditions, and particularly current speeds, have a strong influence on the management of fish cage culture. These hydrodynamic conditions can be used to predict particle movement within the water column and the results used to optimise environmental conditions for effective site selection, setting of environmental quality standards, waste dispersion, and potential disease transfer. To this end, a 3D hydrodynamic model, MOHID, has been coupled to a particle tracking model to study the effects of mean current speed, quiescent water periods and bulk water circulation in Mulroy Bay, Co. Donegal Ireland, an Irish fjard (shallow fjordic system) important to the aquaculture industry. A Lagangrian method simulated the instantaneous release of "particles" emulating discharge from finfish cages to show the behaviour of waste in terms of water circulation and water exchange. The 3D spatial models were used to identify areas of mixed and stratified water using a version of the Simpson-Hunter criteria, and to use this in conjunction with models of current flow for appropriate site selection for salmon aquaculture. The modelled outcomes for stratification were in good agreement with the direct measurements of water column stratification based on observed density profiles. Calculations of the Simpson-Hunter tidal parameter indicated that most of Mulroy Bay was potentially stratified with a well mixed region over the shallow channels where the water is faster flowing. The fjard was characterised by areas of both very low and high mean current speeds, with some areas having long periods of quiescent water. The residual current and the particle tracking animations created through the models revealed an anticlockwise eddy that may influence waste dispersion and potential for disease transfer, among salmon cages and which ensures that the retention time of waste substances from cages is extended. The hydrodynamic model results were incorporated into the ArcView TM GIS

  11. Hydrodynamics of an Electrochemical Membrane Bioreactor

    Science.gov (United States)

    Wang, Ya-Zhou; Wang, Yun-Kun; He, Chuan-Shu; Yang, Hou-Yun; Sheng, Guo-Ping; Shen, Jin-You; Mu, Yang; Yu, Han-Qing

    2015-05-01

    An electrochemical membrane bioreactor (EMBR) has recently been developed for energy recovery and wastewater treatment. The hydrodynamics of the EMBR would significantly affect the mass transfers and reaction kinetics, exerting a pronounced effect on reactor performance. However, only scarce information is available to date. In this study, the hydrodynamic characteristics of the EMBR were investigated through various approaches. Tracer tests were adopted to generate residence time distribution curves at various hydraulic residence times, and three hydraulic models were developed to simulate the results of tracer studies. In addition, the detailed flow patterns of the EMBR were acquired from a computational fluid dynamics (CFD) simulation. Compared to the tank-in-series and axial dispersion ones, the Martin model could describe hydraulic performance of the EBMR better. CFD simulation results clearly indicated the existence of a preferential or circuitous flow in the EMBR. Moreover, the possible locations of dead zones in the EMBR were visualized through the CFD simulation. Based on these results, the relationship between the reactor performance and the hydrodynamics of EMBR was further elucidated relative to the current generation. The results of this study would benefit the design, operation and optimization of the EMBR for simultaneous energy recovery and wastewater treatment.

  12. Non-dissipative hydrodynamics: Effective actions versus entropy current

    CERN Document Server

    Bhattacharya, Jyotirmoy; Rangamani, Mukund

    2012-01-01

    While conventional hydrodynamics incorporating dissipative effects is hard to derive from an action principle, it is nevertheless possible to construct classical actions when the dissipative terms are switched off. In this note we undertake a systematic exploration of such constructions from an effective field theory approach and argue for the existence of non-trivial second order non-dissipative hydrodynamics involving pure energy-momentum transport. We find these fluids to be characterized by five second-order transport coefficients based on the effective action (a three parameter family is Weyl invariant). On the other hand since all flows of such fluids are non-dissipative, they entail zero entropy production; one can therefore understand them using the entropy current formalism which has provided much insight into hydrodynamic transport. An analysis of the most general stress tensor with zero entropy production however turns out to give a seven parameter family of non-dissipative hydrodynamics (a four pa...

  13. Axial dispersion via shear-enhanced diffusion in colloidal suspensions

    KAUST Repository

    Griffiths, I. M.

    2012-03-01

    The familiar example of Taylor dispersion of molecular solutes is extended to describe colloidal suspensions, where the fluctuations that contribute to dispersion arise from hydrodynamic interactions. The generic scheme is illustrated for a suspension of particles in a pressure-driven pipe flow, with a concentration-dependent diffusivity that captures both the shear-induced and Brownian contributions. The effect of the cross-stream migration via shear-induced diffusion is shown to dramatically reduce the axial dispersion predicted by classical Taylor dispersion for a molecular solute. Analytic and numerical solutions are presented that illustrate the effect of the concentration dependence of this nonlinear hydrodynamic mechanism. Copyright © EPLA, 2012.

  14. Hydrodynamic spectrum of a superfluid in an elongated trap

    Science.gov (United States)

    Crépin, Pierre-Philippe; Leyronas, Xavier; Chevy, Frédéric

    2016-06-01

    In this article we study the hydrodynamic spectrum of a superfluid confined in cylindrical trap. We show that the dispersion relation ω(q) of the phonon branch scales like \\sqrt{q} at large q, leading to a vanishingly small superfluid critical velocity. In practice the critical velocity is set by the breakdown of the hydrodynamic approximation. For a broad class of superfluids, this entails a reduction of the critical velocity by a factor (\\hbarω_\\perp/μ_c)1/3 with respect to the free-space prediction (here ω_\\perp is the trapping frequency and μ_\\text{c} the chemical potential of the cloud).

  15. Foundations of radiation hydrodynamics

    CERN Document Server

    Mihalas, Dimitri

    1999-01-01

    Radiation hydrodynamics is a broad subject that cuts across many disciplines in physics and astronomy: fluid dynamics, thermodynamics, statistical mechanics, kinetic theory, and radiative transfer, among others. The theory developed in this book by two specialists in the field can be applied to the study of such diverse astrophysical phenomena as stellar winds, supernova explosions, and the initial phases of cosmic expansion, as well as the physics of laser fusion and reentry vehicles. As such, it provides students with the basic tools for research on radiating flows.Largely self-contained,

  16. Molecular hydrodynamics from memory kernels

    CERN Document Server

    Lesnicki, Dominika; Carof, Antoine; Rotenberg, Benjamin

    2016-01-01

    The memory kernel for a tagged particle in a fluid, computed from molecular dynamics simulations, decays algebraically as $t^{-3/2}$. We show how the hydrodynamic Basset-Boussinesq force naturally emerges from this long-time tail and generalize the concept of hydrodynamic added mass. This mass term is negative in the present case of a molecular solute, at odds with incompressible hydrodynamics predictions. We finally discuss the various contributions to the friction, the associated time scales and the cross-over between the molecular and hydrodynamic regimes upon increasing the solute radius.

  17. Scaling of magneto-quantum-radiative hydrodynamic equations: from laser-produced plasmas to astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Cross, J. E.; Gregori, G. [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Reville, B., E-mail: j.e.cross@physics.ox.ac.uk [Centre for Plasma Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2014-11-01

    We introduce the equations of magneto-quantum-radiative hydrodynamics. By rewriting them in a dimensionless form, we obtain a set of parameters that describe scale-dependent ratios of characteristic hydrodynamic quantities. We discuss how these dimensionless parameters relate to the scaling between astrophysical observations and laboratory experiments.

  18. Scaling of Magneto-quantum-radiative Hydrodynamic Equations: From Laser-produced Plasmas to Astrophysics

    Science.gov (United States)

    Cross, J. E.; Reville, B.; Gregori, G.

    2014-11-01

    We introduce the equations of magneto-quantum-radiative hydrodynamics. By rewriting them in a dimensionless form, we obtain a set of parameters that describe scale-dependent ratios of characteristic hydrodynamic quantities. We discuss how these dimensionless parameters relate to the scaling between astrophysical observations and laboratory experiments.

  19. Hydrodynamics of pronuclear migration

    Science.gov (United States)

    Nazockdast, Ehssan; Needleman, Daniel; Shelley, Michael

    2014-11-01

    Microtubule (MT) filaments play a key role in many processes involved in cell devision including spindle formation, chromosome segregation, and pronuclear positioning. We present a direct numerical technique to simulate MT dynamics in such processes. Our method includes hydrodynamically mediated interactions between MTs and other cytoskeletal objects, using singularity methods for Stokes flow. Long-ranged many-body hydrodynamic interactions are computed using a highly efficient and scalable fast multipole method, enabling the simulation of thousands of MTs. Our simulation method also takes into account the flexibility of MTs using Euler-Bernoulli beam theory as well as their dynamic instability. Using this technique, we simulate pronuclear migration in single-celled Caenorhabditis elegans embryos. Two different positioning mechanisms, based on the interactions of MTs with the motor proteins and the cell cortex, are explored: cytoplasmic pulling and cortical pushing. We find that although the pronuclear complex migrates towards the center of the cell in both models, the generated cytoplasmic flows are fundamentally different. This suggest that cytoplasmic flow visualization during pronuclear migration can be utilized to differentiate between the two mechanisms.

  20. Evolution of dispersal distance.

    Science.gov (United States)

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  1. Study of axial mixing, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column using radiotracer technique

    Energy Technology Data Exchange (ETDEWEB)

    Ghiyas Ud Din [Department of Nuclear Engineering, Pakistan Institute of Engineering and Applied Sciences -PIEAS, P.O Nilore, Islamabad (Pakistan); Isotope Application Division, Pakistan Institute of Nuclear Science and Technology - PINSTECH, P.O Nilore, Islamabad (Pakistan)], E-mail: fac192@pieas.edu.pk; Imran Rafiq Chughtai; Mansoor Hameed Inayat [Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences - PIEAS, P.O Nilore, Islamabad (Pakistan); Iqbal Hussain Khan [Isotope Application Division, Pakistan Institute of Nuclear Science and Technology - PINSTECH, P.O Nilore, Islamabad (Pakistan)

    2009-07-15

    Axial mixing, holdup and slip velocity of dispersed phase which are parameters of fundamental importance in the design and operation of liquid-liquid extraction pulsed sieve plate columns have been investigated. Experiments for residence time distribution (RTD) analysis have been carried out for a range of pulsation frequency and amplitude in a liquid-liquid extraction pulsed sieve plate column with water as dispersed and kerosene as continuous phase using radiotracer technique. The column was operated in emulsion region and {sup 99m}Tc in the form of sodium pertechnetate eluted from a {sup 99}Mo/{sup 99m}Tc generator was used to trace the dispersed phase. Axial dispersed plug flow model with open-open boundary condition and two points measurement method was used to simulate the hydrodynamics of dispersed phase. It has been observed that the axial mixing and holdup of dispersed phase increases with increase in pulsation frequency and amplitude until a maximum value is achieved while slip velocity decreases with increase in pulsation frequency and amplitude until it approaches a minimum value. Short lived and low energy radiotracer {sup 99m}Tc in the form of sodium pertechnetate was found to be a good water tracer to study the hydrodynamics of a liquid-liquid extraction pulsed sieve plate column operating with two immiscible liquids, water and kerosene. Axial dispersed plug flow model with open-open boundary condition was found to be a suitable model to describe the hydrodynamics of dispersed phase in the pulsed sieve plate extraction column.

  2. Microbial and hydrodynamic characterization of a compost biofilter BTX compounds

    Energy Technology Data Exchange (ETDEWEB)

    Rho, D.; Tahraoui, K. [Biotechnical Research Institute, Montreal, Quebec (Canada); Juteau, P. [Biotechnology Research Institute, Montreal, Quebec (Canada)]|[Laval Univ., Sainte-Foy, Quebec (Canada); LeDuy, A. [Laval Univ., Sainte-Foy, Quebec (Canada)

    1995-12-31

    The degradation of toxic aromatic compounds, such as benzene, toluene and xylenes (BTX) in gaseous effluents was studied in a modular biofilter. The reactor was made of two columns separated by a grid. Each column was filled with a mixture of a commercial composted chicken manure and peat moss blend. The effluent gas was prehumidified and the temperature of the bed was maintained around 23{degrees}C. The biofilter was operated at a superficial gas velocity ranging from 10 to 100 m{sup 3}m{sup -2}h{sup 1} and at BTX organic load up to 90 g m{sup -3}h{sup -1}. Special attention was paid to the influence of the superficial gas velocity and the organic load on the filter bed`s elimination capacity. The bed hydrodynamic was also studied in order to determine the gas phase dispersion parameter. The performance and operational criteria of the biofilter were analyzed on the basis of water activity and water content. Respiration (i.e. CO{sub 2} production and O{sub 2} consumption) of the filter bed throughout a biofiltration experiment was followed using a radio-respirometric test and a respirometer.

  3. Effective Hydrodynamic Boundary Conditions for Corrugated Surfaces

    CERN Document Server

    Mongruel, Anne; Asmolov, Evgeny S; Vinogradova, Olga I

    2012-01-01

    We report measurements of the hydrodynamic drag force acting on a smooth sphere falling down under gravity to a plane decorated with microscopic periodic grooves. Both surfaces are lyophilic, so that a liquid (silicone oil) invades the surface texture being in the Wenzel state. A significant decrease in the hydrodynamic resistance force as compared with that predicted for two smooth surfaces is observed. To quantify the effect of roughness we use the effective no-slip boundary condition, which is applied at the imaginary smooth homogeneous isotropic surface located at an intermediate position between top and bottom of grooves. Such an effective condition fully characterizes the force reduction measured with the real surface, and the location of this effective plane is related to geometric parameters of the texture by a simple analytical formula.

  4. Application of hydrodynamics to heavy ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Felsberger, Lukas

    2014-12-02

    The Bjorken model is a simple tool for making rough predictions of the hydrodynamic evolution of the thermalized matter created in a heavy ion collision. The advantage of the model clearly lies in its simplicity, rather than accuracy. As it is still used for making rough estimations 'by hand', in this thesis, I investigate in which cases the Bjorken model gives useful results and in which it is not recommended. For central collisions, I show which critical size the nuclei should have so that the Bjorken model can be applied. For non-central collisions, I demonstrate that using Glauber initial conditions combined with the Bjorken evolution, leads to reasonable results up to large impact parameters. Finally, I study the case of a non-ideal (viscous) description of the thermalized matter which leads to strongly differing results if first- or second-order hydrodynamics is applied.

  5. Hydrodynamic interaction of swimming organisms in an inertial regime

    Science.gov (United States)

    Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M.

    2016-11-01

    We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re˜O (0.1 -100 ) , where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.

  6. Comparison of two ionic liquid dispersive liquid-liquid microextraction approaches for the determination of benzoylurea insecticides in wastewater using liquid chromatography-quadrupole-linear ion trap-mass spectrometry: evaluation of green parameters.

    Science.gov (United States)

    Vázquez, M M Parrilla; Vázquez, P Parrilla; Galera, M Martínez; Moreno, A Uclés

    2014-08-22

    Two dispersive liquid-liquid microextraction (DLLME) approaches including temperature-controlled ionic liquid dispersive liquid-liquid microextraction (TCIL-DLLME) and ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (US-IL-DLLME) were compared for the extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, lufenuron and flufenoxuron) from wastewater samples prior to their determination by high-performance liquid chromatography with a hybrid triple quadrupole-linear ion trap-mass spectrometer (LC-QqLIT-MS/MS). Influential parameters affecting extraction efficiency were systematically studied and optimized and the most significant green parameters were quantified and compared. The best results were obtained using the US-IL-DLLME procedure, which employed the IL 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and methanol (MeOH) as extraction and disperser solvent, respectively. US-IL-DLLME procedure was fast, easy, low environmental toxicity and, it was also able to successfully extract all selected benzoylureas. This method was extensively validated with satisfactory results: limits of detection and quantification were in the range 0.5-1.0 ng L(-1) and 1.5-3.5 ng L(-1), respectively, whereas recovery rates ranged from 89 to 103% and the relative standard deviations were lower than 13.4%. The applicability of the method was assessed with the analysis of effluent wastewater samples from a wastewater treatment plant located in an agricultural zone of Almería (Spain) and the results indicated the presence of teflubenzuron at mean concentration levels of 11.3 ng L(-1). US-IL-DLLME sample treatment in combination with LC-QqLIT-MS/MS has demonstrated to be a sensitive, selective and efficient method to determine benzoylurea insecticides in wastewaters at ultra-trace levels.

  7. Application of solubility parameter to disperse dyeing of polyester fibers (Ⅰ)%溶解度参数在聚酯类纤维分散染色中的应用(一)

    Institute of Scientific and Technical Information of China (English)

    陈荣圻

    2013-01-01

    溶解度参数δ是热力学上衡量非极性溶质与溶剂之间作用力的一种方法,将其用于分散染料对PET聚酯纤维染色中,通过计算PET的δ为10.30~11.6之间,与分散染料有很好的相容性,因此染色性能与牢度性能俱佳.将该方法用于分散染料拼混和染厂拼色,可获得极佳效果.PTT聚酯的δ值为10.50,也可用传统分散染料染色.PLA纤维是一类脂肪族聚酯纤维,性能与PET、PTT不同,其δ值为12.8,传统分散染料达不到很好效果,需研发PLA专用分散染料.%Solubility parameters δ is a thermodynamical parameter to evaluate the action between nonpolar solute and solvent. The 5 value of PET fiber is 10.30 ~ 11.6, so it has good compatibility with disperse dyes, and can obtain good dyeing behavior and color fastness. It can be used to evaluate the compound dyeing results in dye house. The 5 value of PTT fiber is 10.50, and it can be dyed with traditional disperse dyes. PLA fiber is a kind of aromatic polyester fiber, and its properties are different from PET and PTT fiber. The S value of PLA fiber is 12.8, if it is dyed with traditional disperse dyes, PLA fiber can not obtain satisfactory dyeing results, so special disperse dyes for PLA is looked forward to be developed.

  8. Hydrodynamic theory of partially degenerate electron-hole fluids in semiconductors

    Science.gov (United States)

    Akbari-Moghanjoughi, M.; Eliasson, B.

    2016-10-01

    A quantum hydrodynamic theory for high-frequency electron-hole Langmuir and acoustic-like oscillations as well as static charge shielding effects in arbitrarily doped semiconductors is presented. The model includes kinetic corrections to the quantum statistical pressure and to the quantum Bohm potential for partially degenerate electrons and holes at finite temperatures. The holes contribute to the oscillations and screening effects in semiconductors in a similar manner as real particles. The dielectric functions are derived in the high-frequency limit for wave excitations and in the low-frequency limit for the study of static screening. The dispersion relation for the Langmuir and acoustic-like oscillations is examined for different parameters of doped silicon (Si). Some interesting properties and differences of electron hole dynamical behavior in N- and P-type Si are pointed out. Holes are also observed to enhance an attractive charge shielding effect when the semiconductor is highly acceptor-doped.

  9. Fluctuations in Relativistic Causal Hydrodynamics

    CERN Document Server

    Kumar, Avdhesh; Mishra, Ananta P

    2013-01-01

    The formalism to calculate the hydrodynamics fluctuation using the quasi-stationary fluctuation theory of Onsager to the relativistic Navier-Stokes hydrodynamics is already known. In this work we calculate hydrodynamic fluctuations in relativistic causal theory of Muller, Israel and Stewart and other related causal hydrodynamic theories. We show that expressions for the Onsager coefficients and the correlation functions have form similar to the ones obtained by using Navier-Stokes equation. However, temporal evolution of the correlation functions obtained using MIS and the other causal theories can be significantly different than the correlation functions obtained using the Navier-Stokes equation. Finally, as an illustrative example, we explicitly plot the correlation functions obtained using the causal-hydrodynamics theories and compare them with correlation functions obtained by earlier authors using the expanding boost-invariant (Bjorken) flows.

  10. Gradient expansion for anisotropic hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Spaliński, Michał

    2016-01-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.

  11. Lifshitz Superfluid Hydrodynamics

    CERN Document Server

    Chapman, Shira; Oz, Yaron

    2014-01-01

    We construct the first order hydrodynamics of quantum critical points with Lifshitz scaling and a spontaneously broken symmetry. The fluid is described by a combination of two flows, a normal component that carries entropy and a super-flow which has zero viscosity and carries no entropy. We analyze the new transport effects allowed by the lack of boost invariance and constrain them by the local second law of thermodynamics. Imposing time-reversal invariance, we find eight new parity even transport coefficients. The formulation is applicable, in general, to any superfluid/superconductor with an explicit breaking of boost symmetry, in particular to high $T_c$ superconductors. We discuss possible experimental signatures.

  12. Hydrodynamics of Ship Propellers

    DEFF Research Database (Denmark)

    Breslin, John P.; Andersen, Poul

    This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and moments which the propeller generates on the shaft and on the ship hull.The first part of the text is devoted to fundamentals of the flow about hydrofoil sections (with and without cavitation......) and about wings. It then treats propellers in uniform flow, first via advanced actuator disc modelling, and then using lifting-line theory. Pragmatic guidance is given for design and evaluation of performance, including the use of computer modelling.The second part covers the development of unsteady forces...... arising from operation in non-uniform hull wakes. First, by a number of simplifications, various aspects of the problem are dealt with separately until the full problem of a non-cavitating, wide-bladed propeller in a wake is treated by a new and completely developed theory. Next, the complicated problem...

  13. Hydrodynamic effects on coalescence.

    Energy Technology Data Exchange (ETDEWEB)

    Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael (Yale University, New Haven, CT); Gorby, Allen D.; Brooks, Carlton, F.

    2006-10-01

    The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.

  14. Viscous Fluid Conduits as a Prototypical Nonlinear Dispersive Wave Platform

    Science.gov (United States)

    Lowman, Nicholas K.

    This thesis is devoted to the comprehensive characterization of slowly modulated, nonlinear waves in dispersive media for physically-relevant systems using a threefold approach: analytical, long-time asymptotics, careful numerical simulations, and quantitative laboratory experiments. In particular, we use this interdisciplinary approach to establish a two-fluid, interfacial fluid flow setting known as viscous fluid conduits as an ideal platform for the experimental study of truly one dimensional, unidirectional solitary waves and dispersively regularized shock waves (DSWs). Starting from the full set of fluid equations for mass and linear momentum conservation, we use a multiple-scales, perturbation approach to derive a scalar, nonlinear, dispersive wave equation for the leading order interfacial dynamics of the system. Using a generalized form of the approximate model equation, we use numerical simulations and an analytical, nonlinear wave averaging technique, Whitham-El modulation theory, to derive the key physical features of interacting large amplitude solitary waves and DSWs. We then present the results of quantitative, experimental investigations into large amplitude solitary wave interactions and DSWs. Overtaking interactions of large amplitude solitary waves are shown to exhibit nearly elastic collisions and universal interaction geometries according to the Lax categories for KdV solitons, and to be in excellent agreement with the dynamics described by the approximate asymptotic model. The dispersive shock wave experiments presented here represent the most extensive comparison to date between theory and data of the key wavetrain parameters predicted by modulation theory. We observe strong agreement. Based on the work in this thesis, viscous fluid conduits provide a well-understood, controlled, table-top environment in which to study universal properties of dispersive hydrodynamics. Motivated by the study of wave propagation in the conduit system, we

  15. Determination of optical constant and dispersion parameters of Se75Sb10In15 thin film characterized by wide band gap

    Science.gov (United States)

    Abd-Elrahman, M. I.; Abu-Sehly, A. A.; El-sonbaty, Sherouk Sh.; Hafiz, M. M.

    2017-02-01

    Chalcogenide Se75Sb10In15 thin films of different thickness (50-300 nm) are deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se75Sb10In15 is obtained using a differential scanning calorimetry (DSC). The crystallization temperature T c, peak crystallization temperature T p and melting temperature T m, are identified. The X-ray diffraction (XRD) examination indicates the crystallinity of the as-deposited film decreases with increasing of thickness. Optical transmission and reflection spectra are recorded in the wavelength range of the incident photons from 250 to 2500 nm. It is found that the film thickness affects the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The absorption mechanism of the as-deposited films is a direct allowed transition. The optical band gap energy ( E g) decreases from 3.31 to 2.51 eV with increasing the film thickness from 50 to 300 nm. The behavior of E g is explained on the basis of the structure disorders in the thicker films. The effect of the film thickness on the single-oscillator and dispersion energies is studied by the dispersion analyses of the refractive index.

  16. Effect of Nano-TiC Dispersed Particles and Electro-Codeposition Parameters on Morphology and Structure of Hybrid Ni/TiC Nanocomposite Layers

    Directory of Open Access Journals (Sweden)

    Lidia Benea

    2016-04-01

    Full Text Available This research work describes the effect of dispersed titanium carbide (TiC nanoparticles into nickel plating bath on Ni/TiC nanostructured composite layers obtained by electro-codeposition. The surface morphology of Ni/TiC nanostructured composite layers was characterized by scanning electron microscopy (SEM. The composition of coatings and the incorporation percentage of TiC nanoparticles into Ni matrix were studied and estimated by using energy dispersive X-ray analysis (EDX. X-ray diffractometer (XRD has been applied in order to investigate the phase structure as well as the corresponding relative texture coefficients of the composite layers. The results show that the concentration of nano-TiC particles added in the nickel electrolyte affects the inclusion percentage of TiC into Ni/TiC nano strucured layers, as well as the corresponding morphology, relative texture coefficients and thickness indicating an increasing tendency with the increasing concentration of nano-TiC concentration. By increasing the amount of TiC nanoparticles in the electrolyte, their incorporation into nickel matrix also increases. The hybrid Ni/nano-TiC composite layers obtained revealed a higher roughness and higher hardness; therefore, these layers are promising superhydrophobic surfaces for special application and could be more resistant to wear than the pure Ni layers.

  17. Determination of optical constant and dispersion parameters of Se{sub 75}Sb{sub 10}In{sub 15} thin film characterized by wide band gap

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elrahman, M.I.; Abu-Sehly, A.A.; El-sonbaty, Sherouk Sh.; Hafiz, M.M. [Assiut University, Physics Department, Faculty of Science, Assiut (Egypt)

    2017-02-15

    Chalcogenide Se{sub 75}Sb{sub 10}In{sub 15} thin films of different thickness (50-300 nm) are deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se{sub 75}Sb{sub 10}In{sub 15} is obtained using a differential scanning calorimetry (DSC). The crystallization temperature T{sub c}, peak crystallization temperature T{sub p} and melting temperature T{sub m}, are identified. The X-ray diffraction (XRD) examination indicates the crystallinity of the as-deposited film decreases with increasing of thickness. Optical transmission and reflection spectra are recorded in the wavelength range of the incident photons from 250 to 2500 nm. It is found that the film thickness affects the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The absorption mechanism of the as-deposited films is a direct allowed transition. The optical band gap energy (E{sub g}) decreases from 3.31 to 2.51 eV with increasing the film thickness from 50 to 300 nm. The behavior of E{sub g} is explained on the basis of the structure disorders in the thicker films. The effect of the film thickness on the single-oscillator and dispersion energies is studied by the dispersion analyses of the refractive index. (orig.)

  18. Analysis of Hydrodynamic (Landau) Instability in Liquid-Propellant Combustion at Normal and Reduced Gravity

    Science.gov (United States)

    Margolis, Stephen B.

    1997-01-01

    The burning of liquid propellants is a fundamental combustion problem that is applicable to various types of propulsion and energetic systems. The deflagration process is often rather complex, with vaporization and pyrolysis occurring at the liquid/gas interface and distributed combustion occurring either in the gas phase or in a spray. Nonetheless, there are realistic limiting cases in which combustion may be approximated by an overall reaction at the liquid/gas interface. In one such limit, the gas flame occurs under near-breakaway conditions, exerting little thermal or hydrodynamic influence on the burning propellant. In another such limit, distributed combustion occurs in an intrusive regime, the reaction zone lying closer to the liquid/gas interface than the length scale of any disturbance of interest. Finally, the liquid propellant may simply undergo exothermic decomposition at the surface without any significant distributed combustion, such as appears to occur in some types of HydroxylAmmonium Nitrate (HAN)-based liquid propellants at low pressures. Such limiting models have recently been formulated,thereby significantly generalizing earlier classical models that were originally introduced to study the hydrodynamic stability of a reactive liquid/gas interface. In all of these investigations, gravity appears explicitly and plays a significant role, along with surface tension, viscosity, and, in the more recent models, certain reaction-rate parameters associated with the pressure and temperature sensitivities of the reaction itself. In particular, these parameters determine the stability of the deflagration with respect to not only classical hydrodynamic disturbances, but also with respect to reactive/diffusive influences as well. Indeed, the inverse Froude number, representing the ratio of buoyant to inertial forces, appears explicitly in all of these models, and consequently, in the dispersion relation that determines the neutral stability boundaries beyond

  19. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  20. Validity condition of separating dispersion of PCFs into material dispersion and geometrical dispersion

    Institute of Scientific and Technical Information of China (English)

    Wei Wang; Lantian Hou; Zhaolun Liu; Guiyao Zhou

    2009-01-01

    When using normalized dispersion method for the dispersion design of photonic crystal fibers(PCFs),it is vital that the group velocity dispersion of PCF can be seen as the sum of geometrical dispersion and material dispersion.However,the error induced by this way of calculation will deteriorate the final results.Taking 5 ps/(km·nm)and 5% as absolute error and relative error limits,respectively,the structure parameter boundaries of PCFs about when separating total dispersion into geometrical and material components is valid are provided for wavelength shorter than 1700 nm.By using these two criteria together,it is adequate to evaluate the simulatcd dispersion of PCFs when normalized dispersion method is employed.

  1. Influence of temperature on microstructure parameters and microhardness of dispersion-hardened V-Cr-Zr-W alloy after deformation by torsion under pressure

    Science.gov (United States)

    Grinyaev, Konstantin V.; Smirnov, Ivan V.; Radishevsky, Vladislav L.; Ditenberg, Ivan A.; Tyumentsev, Alexander N.; Chernov, Vyacheslav M.; Korznikov, Alexander V.

    2016-11-01

    Study of microstructure transformation and microhardness changes of dispersion-hardened V-Cr-Zr-W alloy after severe plastic deformation by torsion on Bridgman anvils and subsequent heat treatments was conducted. Basic stages of relaxation processes were revealed: at 800°C recovery processes take place and primary recrystallization begins; at 900°C primary recrystallization intensifies; in range of 950-1050°C collective recrystallization processes activate; at 1200°C secondary recrystallization starts. Microhardness measurement and comparison of its values with structural states features were conducted. Strengthening mechanisms and their contribution at various stages of defect substructure relaxation are discussed. It is shown that increase of thermal stability of V-Cr-Zr-W alloy microstructure is a consequence of the formation of high density of thermally stable Zr (O-N-C)-based nanoparticles.

  2. Role of Brownian Motion Hydrodynamics on Nanofluid Thermal Conductivity

    Energy Technology Data Exchange (ETDEWEB)

    W Evans, J Fish, P Keblinski

    2005-11-14

    We use a simple kinetic theory based analysis of heat flow in fluid suspensions of solid nanoparticles (nanofluids) to demonstrate that the hydrodynamics effects associated with Brownian motion have a minor effect on the thermal conductivity of the nanofluid. Our conjecture is supported by the results of molecular dynamics simulations of heat flow in a model nanofluid with well-dispersed particles. Our findings are consistent with the predictions of the effective medium theory as well as with recent experimental results on well dispersed metal nanoparticle suspensions.

  3. Special Relativistic Hydrodynamics with Gravitation

    Science.gov (United States)

    Hwang, Jai-chan; Noh, Hyerim

    2016-12-01

    Special relativistic hydrodynamics with weak gravity has hitherto been unknown in the literature. Whether such an asymmetric combination is possible has been unclear. Here, the hydrodynamic equations with Poisson-type gravity, considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit, are consistently derived from Einstein’s theory of general relativity. An analysis is made in the maximal slicing, where the Poisson’s equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the general hypersurface condition. Our formulation includes the anisotropic stress.

  4. Special relativistic hydrodynamics with gravitation

    CERN Document Server

    Hwang, Jai-chan

    2016-01-01

    The special relativistic hydrodynamics with weak gravity is hitherto unknown in the literature. Whether such an asymmetric combination is possible was unclear. Here, the hydrodynamic equations with Poisson-type gravity considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit are consistently derived from Einstein's general relativity. Analysis is made in the maximal slicing where the Poisson's equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the {\\it general} hypersurface condition. Our formulation includes the anisotropic stress.

  5. Effects of surfactant on bubble hydrodynamic behavior under flotation-related conditions in wastewater.

    Science.gov (United States)

    Li, Yanpeng; Zhu, Tingting; Liu, Yanyan; Tian, Ye; Wang, Huanran

    2012-01-01

    Bubble behavior is fundamental to the performance of froth flotation operations used in wastewater treatment processes. To fully understand and characterize bubble behavior under flotation-related conditions in wastewater, the high-speed photographic method has been employed to examine the motion of single bubbles and size distribution of bubble swarms with intermediate sizes ranging from 1 to 4 mm in the presence of surfactants in a laboratory scale flotation column. Both distilled water and synthetic municipal wastewater have been used to make solutions as well as two types of common surfactants. The instantaneous bubble motion has been recorded by a high speed camera. Subsequently, bubble trajectory, dimensions, velocity and distribution have been determined from the recorded frames using the image analysis software. The experimental results show that the addition of surfactant into wastewater has similar effects on bubble hydrodynamic behavior as in pure water (e.g., improving trajectory stabilization, dampening bubble deformation, slowing down terminal velocity, reducing bubble size and increasing the specific surface area of bubble swarm) due to the Marangoni effect. However, it is interesting to note that surfactant effects on single bubble hydrodynamics in wastewater are slightly stronger than those in pure water while surfactant effects on size parameters of bubble swarms in wastewater are significantly stronger than those in pure water. This finding suggests that besides surfactant, inorganic salts present in synthetic wastewater have an important influence on bubble dispersion.

  6. Semi-relativistic hydrodynamics of three-dimensional and low-dimensional quantum plasma

    CERN Document Server

    Andreev, Pavel; Kuz'menkov, Leonid

    2014-01-01

    Contributions of the current-current and Darwin interactions and weak-relativistic addition to kinetic energy in the quantum hydrodynamic equations are considered. Features of hydrodynamic equations for two-dimensional layer of plasma (two-dimensional electron gas for instance) are described. It is shown that the force fields caused by the Darwin interaction and weak-relativistic addition to kinetic energy are partially reduced. Dispersion of three- and two-dimensional semi-relativistic Langmuir waves is calculated.

  7. Fluidization of Wet Granulates under Hydrodynamic Shear

    CERN Document Server

    Battiato, I

    2012-01-01

    We investigate the fluidization threshold of three-dimensional cohesive granulates under hydrodynamic shear forces exerted by a creeping ow. A continuum model of flow through porous media provides an analytical expression for the average drag force on a single grain. The balance equation for the forces and a force propagation model are then used to investigate the effects of porosity and packing structure on the stability of the pile. We obtain a closed-form expression for the fluidization threshold of a regular packing of mono-disperse frictionless cohesive spherical grains in a planar fracture. The compound effect of structural (packing orientation and porosity) and dynamical properties of the system on its stability is quantified.

  8. Bosonization and quantum hydrodynamics

    Indian Academy of Sciences (India)

    Girish S Setlur

    2006-03-01

    It is shown that it is possible to bosonize fermions in any number of dimensions using the hydrodynamic variables, namely the velocity potential and density. The slow part of the Fermi field is defined irrespective of dimensionality and the commutators of this field with currents and densities are exponentiated using the velocity potential as conjugate to the density. An action in terms of these canonical bosonic variables is proposed that reproduces the correct current and density correlations. This formalism in one dimension is shown to be equivalent to the Tomonaga-Luttinger approach as it leads to the same propagator and exponents. We compute the one-particle properties of a spinless homogeneous Fermi system in two spatial dimensions with long-range gauge interactions and highlight the metal-insulator transition in the system. A general formula for the generating function of density correlations is derived that is valid beyond the random phase approximation. Finally, we write down a formula for the annihilation operator in momentum space directly in terms of number conserving products of Fermi fields.

  9. Engineering Hydrodynamic AUV Hulls

    Science.gov (United States)

    Allen, J.

    2016-12-01

    AUV stands for autonomous underwater vehicle. AUVs are used in oceanography and are similar to gliders. MBARIs AUVs as well as other AUVs map the ocean floor which is very important. They also measure physical characteristics of the water, such as temperature and salinity. My science fair project for 4th grade was a STEM activity in which I built and tested 3 different AUV bodies. I wanted to find out which design was the most hydrodynamic. I tested three different lengths of AUV hulls to see which AUV would glide the farthest. The first was 6 inches. The second was 12 inches and the third was 18 inches. I used clay for the nosecone and cut a ruler into two and made it the fin. Each AUV used the same nosecone and fin. I tested all three designs in a pool. I used biomimicry to create my hypothesis. When I was researching I found that long slim animals swim fastest. So, my hypothesis is the longer AUV will glide farthest. In the end I was right. The longer AUV did glide the farthest.

  10. Reciprocal relations in dissipationless hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Melnikovsky, L. A., E-mail: leva@kapitza.ras.ru [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)

    2014-12-15

    Hidden symmetry in dissipationless terms of arbitrary hydrodynamics equations is recognized. We demonstrate that all fluxes are generated by a single function and derive conventional Euler equations using the proposed formalism.

  11. Relativistic Hydrodynamics on Graphic Cards

    CERN Document Server

    Gerhard, Jochen; Bleicher, Marcus

    2012-01-01

    We show how to accelerate relativistic hydrodynamics simulations using graphic cards (graphic processing units, GPUs). These improvements are of highest relevance e.g. to the field of high-energetic nucleus-nucleus collisions at RHIC and LHC where (ideal and dissipative) relativistic hydrodynamics is used to calculate the evolution of hot and dense QCD matter. The results reported here are based on the Sharp And Smooth Transport Algorithm (SHASTA), which is employed in many hydrodynamical models and hybrid simulation packages, e.g. the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). We have redesigned the SHASTA using the OpenCL computing framework to work on accelerators like graphic processing units (GPUs) as well as on multi-core processors. With the redesign of the algorithm the hydrodynamic calculations have been accelerated by a factor 160 allowing for event-by-event calculations and better statistics in hybrid calculations.

  12. Gradient expansion for anisotropic hydrodynamics

    Science.gov (United States)

    Florkowski, Wojciech; Ryblewski, Radoslaw; Spaliński, Michał

    2016-12-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of nonhydrodynamic modes.

  13. Hydrodynamics of anisotropic quark and gluon fluids

    Science.gov (United States)

    Florkowski, Wojciech; Maj, Radoslaw; Ryblewski, Radoslaw; Strickland, Michael

    2013-03-01

    The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory, with the collisional kernel treated in the relaxation-time approximation, allowing for different relaxation times for quarks and gluons. Baryon number conservation is enforced in the quark and antiquark components of the fluid, but overall parton number nonconservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.

  14. Hydrodynamics of anisotropic quark and gluon fluids

    CERN Document Server

    Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael

    2012-01-01

    The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory with the collisional kernel treated in the relaxation-time approximation. Baryon number conservation is enforced in the quark and anti-quark components of the fluid, but overall parton number non-conservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.

  15. An introduction to astrophysical hydrodynamics

    CERN Document Server

    Shore, Steven N

    1992-01-01

    This book is an introduction to astrophysical hydrodynamics for both astronomy and physics students. It provides a comprehensive and unified view of the general problems associated with fluids in a cosmic context, with a discussion of fluid dynamics and plasma physics. It is the only book on hydrodynamics that addresses the astrophysical context. Researchers and students will find this work to be an exceptional reference. Contents include chapters on irrotational and rotational flows, turbulence, magnetohydrodynamics, and instabilities.

  16. Optical band gap and refractive index dispersion parameters of As x Se70Te30- x (0≤ x≤30 at.%) amorphous films

    Science.gov (United States)

    Aly, Kamal A.

    2010-06-01

    Amorphous As x Se70Te30- x thin films with (0≤ x≤30 at.%) were deposited onto glass substrates by using thermal evaporation method. The transmission spectra T( λ) of the films at normal incidence were measured in the wavelength range 400-2500 nm. A straightforward analysis proposed by Swanepoel based on the use of the maxima and minima of the interference fringes has been used to drive the film thickness, d, the complex index of refraction, n, and the extinction coefficient, k. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model (WDD). Increasing As content is found to affect the refractive index and the extinction coefficient of the As x Se70Te30- x films. With increasing As content the optical band gap increases while the refractive index decreases. The optical absorption is due to allowed indirect transition. The chemical bond approach has been applied successfully to interpret the increase of the optical gap with increasing As content.

  17. Hydrodynamics of coalescing binary neutron stars ellipsoidal treatment

    CERN Document Server

    Lai, D; Lai, Dong; Shapiro, Stu

    1994-01-01

    We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a polytropic equation of state; all internal fluid velocities are assumed to be linear functions of the coordinates. The hydrodynamic equations then reduce to a set of coupled ordinary differential equations for the evolution of the principal axes of the ellipsoids, the internal velocity parameters and the binary orbital parameters. Gravitational radiation reaction and viscous dissipation are both incorporated. We set up exact initial binary equilibrium configurations and follow the transition from the quasi-static, secular decay of the orbit at large separation to the rapid dynamical evolution of the configurations just prior to contact. A hydrodynamical instability resulting from tidal interactions significantly accelerates the coalescence at small separation, leading to app...

  18. Antimicrobial polyethyleneimine-silver nanoparticles in a stable colloidal dispersion.

    Science.gov (United States)

    Lee, Hyun Ju; Lee, Se Guen; Oh, Eun Jung; Chung, Ho Yun; Han, Sang Ik; Kim, Eun Jung; Seo, Song Yi; Ghim, Han Do; Yeum, Jeong Hyun; Choi, Jin Hyun

    2011-11-01

    Excellent colloidal stability and antimicrobial activity are important parameters for silver nanoparticles (AgNPs) in a range of biomedical applications. In this study, polyethyleneimine (PEI)-capped silver nanoparticles (PEI-AgNPs) were synthesized in the presence of sodium borohydride (NaBH(4)) and PEI at room temperature. The PEI-AgNPs had a positive zeta potential of approximately +49 mV, and formed a stable nanocolloid against agglomeration due to electrostatic repulsion. The particle size and hydrodynamic cluster size showed significant correlations with the amount of PEI and NaBH(4). PEI-AgNPs and even PEI showed excellent antimicrobial activity against Staphylococus aureus and Klebsiella pneumoniae. The cytotoxic effects of PEI and PEI-AgNPs were confirmed by an evaluation of the cell viability. The results suggest that the amount of PEI should be minimized to the level that maintains the stability of PEI-AgNPs in a colloidal dispersion.

  19. Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations.

    Science.gov (United States)

    Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K

    2017-09-15

    Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion

  20. Effect of size discrepancy of. gamma. - and. gamma. '-phases crystal lattice parameters on heat resisting dispersion hardening nickel alloys

    Energy Technology Data Exchange (ETDEWEB)

    Petrushin, N.V.; Ignatova, I.A.; Logunov, A.V.; Samojlov, A.I.; Razumovskij, I.M.

    Effect of Cr, Co, Nb and W alloying elements on crystal lattice parameters of ..gamma.. ahd ..gamma..' phases in Ni-Cr-Co-W-Al-Ti- Nb-Hf alloys and on their dimensional misfit at 293 and 1173 K is studied. Alloying at which alloys have the parameter of ..gamma..-solid solution lattice less than that of ..gamma..'-phase results in low heat-resistant properties and in considerable difference of coefficients of thermal expansion of the phases. Definite positive misfit of ..gamma..- and ..gamma..'-phase lattices and a low temperature gradient are the conditions of high heat resistance of complex-alloyed nickel alloys. Possible mechanisms of lattice misfit effect on strength and coalescence kinetics of the second phase in heterogeneous alloys at high temperatures are discussed.

  1. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  2. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set...

  3. CALIBRATED HYDRODYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Sezar Gülbaz

    2015-01-01

    Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.

  4. Absorption and dispersion of ultrasonic waves

    CERN Document Server

    Herzfeld, Karl F; Massey, H S W; Brueckner, Keith A

    1959-01-01

    Absorption and Dispersion of Ultrasonic Waves focuses on the influence of ultrasonics on molecular processes in liquids and gases, including hydrodynamics, energy exchange, and chemical reactions. The book first offers information on the Stokes-Navier equations of hydrodynamics, as well as equations of motion, viscosity, formal introduction of volume viscosity, and linearized wave equation for a nonviscous fluid. The manuscript then ponders on energy exchange between internal and external degrees of freedom as relaxation phenomenon; effect of slow energy exchange on sound propagation; differe

  5. Calculating rotating hydrodynamic and magneto-hydrodynamic waves to understand magnetic effects on dynamical tides

    CERN Document Server

    Wei, Xing

    2016-01-01

    For understanding magnetic effects on dynamical tides, we study the rotating magneto-hydrodynamic (MHD) flow driven by harmonic forcing. The linear responses are analytically derived in a periodic box under the local WKB approximation. Both the kinetic and Ohmic dissipations at the resonant frequencies are calculated and the various parameters are investigated. Although magnetic pressure may be negligible compared to thermal pressure, magnetic field can be important for the first-order perturbation, e.g. dynamical tides. It is found that magnetic field splits the resonant frequency, namely the rotating hydrodynamic flow has only one resonant frequency but the rotating MHD flow has two, one positive and the other negative. In the weak field regime the dissipations are asymmetric around the two resonant frequencies and this asymmetry is more striking with a weaker magnetic field. It is also found that both the kinetic and Ohmic dissipations at the resonant frequencies are inversely proportional to the Ekman num...

  6. HYDRODYNAMICAL MODELS OF TYPE II-P SUPERNOVA LIGHT CURVES

    Directory of Open Access Journals (Sweden)

    M. C. Bersten

    2009-01-01

    Full Text Available We present progress in light curve models of type II-P supernovae (SNe II-P obtained using a newly devel- oped, one-dimensional hydrodynamic code. Using simple initial models (polytropes, we reproduced the global behavior of the observed light curves and we analyzed the sensitivity of the light curves to the variation of free parameters.

  7. [New procedure for protein spinning: the hydrodynamic process].

    Science.gov (United States)

    Castaigne, F; Liber, E; Carbillet, L; Boulet, M; Riel, R R

    1978-01-01

    In this text, we describe a new protein spinning process called hydrodynamic process. Parameters which are related to production of fibers and which can influence diameter and texture are explained extensively. In this process, a spinning dope is extruded through a spinnerette in a moving coagulation bath in which the fibers are coagulated, stretched and carried.

  8. Early developability screen of therapeutic antibody candidates using Taylor dispersion analysis and UV area imaging detection.

    Science.gov (United States)

    Lavoisier, Alexandra; Schlaeppi, Jean-Marc

    2015-01-01

    Therapeutic antibodies represent one of the fastest growing segments in the pharmaceutical market. They are used in a broad range of disease fields, such as autoimmune diseases, cancer, inflammation and infectious diseases. The growth of the segment has necessitated development of new analytical platforms for faster and better antibody selection and characterization. Early quality control and risk assessment of biophysical parameters help prevent failure in later stages of antibody development, and thus can reduce costs and save time. Critical parameters such as aggregation, conformational stability, colloidal stability and hydrophilicity, are measured during the early phase of antibody generation and guide the selection process of the best lead candidates in terms of technical developability. We report on the use of a novel instrument (ActiPix/Viscosizer) for measuring both the hydrodynamic radius and the absolute viscosity of antibodies based on Taylor dispersion analysis and UV area imaging. The looped microcapillary-based method combines low sample consumption, fast throughput and high precision compared to other conventional methods. From a random panel of 130 antibodies in the early selection process, we identified some with large hydrodynamic radius outside the normal distribution and others with non-Gaussian Taylor dispersion profiles. The antibodies with such abnormal properties were confirmed later in the selection process to show poor developability profiles. Moreover, combining these results with those of the viscosity measurements at high antibody concentrations allows screening, with limited amounts of materials, candidates with potential issues in pre-formulation development.

  9. Theoretical Investigation on a Novel Hydrodynamic Journal Bearing

    Institute of Scientific and Technical Information of China (English)

    路长厚; 陈淑江; 张建川

    2004-01-01

    To improve the static and dynamic performance of hydrodynamic journal beatings, a novel bearing is developed, which is a cone-shaped hydrodynamic bearing with spiral oil wedges. The major structural feature of this bearing is the three spiral circular recesses on the beating's surface, leading to improved characteristics. This paper aims to develop a model for design and calculation of the geometric parameters and the oil film thickness, and to provide a theoretical analysis to the static characteristics using a f'mite element method. Some new features are introduced.

  10. Hydrodynamic analysis of heavy ion collisions at RHIC

    CERN Document Server

    Hirano, Tetsufumi

    2008-01-01

    Current status of dynamical modeling of relativistic heavy ion collisions and hydrodynamic description of the quark gluon plasma is reported. We find the hadronic rescattering effect plays an important role in interpretation of mass splitting pattern in the differential elliptic flow data observed at RHIC. To demonstrate this, we predict the elliptic flow parameter for phi mesons to directly observe the flow just after hadronisation. We also discuss recent applications of outputs from hydrodynamic calculations to J/psi suppression, thermal photon radiation and heavy quark diffusion.

  11. HYDRODYNAMICS THEORY AND CALCULATION IN WATER WAVE PUMP DESIGN

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-xue; TAO Yi; LIU Gao-lian

    2005-01-01

    This paper introduces the hydrodynamics theory related to water wave pump.Water wave pump is a new type pump, which uses the particular quality of water wave and re-divides the inflow energy to increase the pressure of one part of the inflow water with the rest water flowing away freely.The research and development of such a pump is of importance and significant value and profitable social interest in that it can fully utilize the residual energy of natural source in industrial and civil water circle systems.Through hydrodynamics research and calculation, a series of valid design parameters were obtained and the predicted results achieved.

  12. Spatial and optical parameters of contrails in the vortex and dispersion regime determined by means of a ground-based scanning lidar

    Energy Technology Data Exchange (ETDEWEB)

    Freudenthaler, V.; Homburg, F.; Jaeger, H. [Fraunhofer-Inst. fuer Atmosphaerische Umweltforschung (IFU), Garmisch-Partenkirchen (Germany)

    1997-12-31

    The spatial growth of individual condensation trails (contrails) of commercial aircrafts in the time range from 15 s to 60 min behind the aircraft is investigated by means of a ground-based scanning backscatter lidar. The growth in width is mainly governed by wind shear and varies between 18 m/min and 140 m/min. The growth of the cross-section varies between 3500 m{sup 2}/min and 25000 m{sup 2}/min. These values are in agreement with results of model calculations and former field measurements. The vertical growth is often limited by boundaries of the humid layer at flight level, but values up to 18 m/min were observed. Optical parameters like depolarization, optical depth and lidar ratio, i.e. the extinction-to-backscatter ratio, have been retrieved from the measurements at a wavelength of 532 nm. The linear depolarization rises from values as low as 0.06 for a young contrail (10 s old) to values around 0.5, typical for aged contrails. The latter indicates the transition from non-crystalline to crystalline particles in persistent contrails within a few minutes. The scatter of depolarization values measured in individual contrails is narrow, independent of the contrails age, and suggests a rather uniform growth of the particles inside a contrail. (author) 18 refs.

  13. Determination of the atrazine migration parameters in Vertisol

    Science.gov (United States)

    Raymundo-Raymundo, E.; Hernandez-Vargas, J.; Nikol'Skii, Yu. N.; Guber, A. K.; Gavi-Reyes, F.; Prado-Pano, B. L.; Figueroa-Sandoval, B.; Mendosa-Hernandez, J. R.

    2010-05-01

    The parameters of the atrazine migration in columns with undisturbed Vertisol sampled from an irrigated plot in Guanajuato, Mexico were determined. A model of the convection-dispersion transport of the chemical compounds accounting for the decomposition and equilibrium adsorption, which is widely applied for assessing the risk of contamination of natural waters with pesticides, was used. The model parameters were obtained by solving the inverse problem of the transport equation on the basis of laboratory experiments on the transport of the 18O isotope and atrazine in soil columns with an undisturbed structure at three filtration velocities. The model adequately described the experimental data at the individual selection of the parameters for each output curve. Physically unsubstantiated parameters of the atrazine adsorption and degradation were obtained when the parameter of the hydrodynamic dispersion was determined from the data on the 18O migration. The simulation also showed that the use of parameters obtained at water content close to saturation in the calculations for an unsaturated soil resulted in the overestimation of the leaching rate and the maximum concentration of atrazine in the output curve compared to the experimental data.

  14. Recent progress in anisotropic hydrodynamics

    CERN Document Server

    Strickland, Michael

    2016-01-01

    The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, . In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.

  15. Numerical Hydrodynamics in Special Relativity

    Directory of Open Access Journals (Sweden)

    Martí José Maria

    2003-01-01

    Full Text Available This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD. Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.

  16. Comparative hydrodynamics of bacterial polymorphism

    CERN Document Server

    Spagnolie, Saverio E

    2011-01-01

    Most bacteria swim through fluids by rotating helical flagella which can take one of twelve distinct polymorphic shapes. The most common helical waveform is the "normal" form, used during forward swimming runs. To shed light on the prevalence of the normal form in locomotion, we gather all available experimental measurements of the various polymorphic forms and compute their intrinsic hydrodynamic efficiencies. The normal helical form is found to be the most hydrodynamically efficient of the twelve polymorphic forms by a significant margin - a conclusion valid for both the peritrichous and polar flagellar families, and robust to a change in the effective flagellum diameter or length. The hydrodynamic optimality of the normal polymorph suggests that, although energetic costs of locomotion are small for bacteria, fluid mechanical forces may have played a significant role in the evolution of the flagellum.

  17. Quantum Plasmas An Hydrodynamic Approach

    CERN Document Server

    Haas, Fernando

    2011-01-01

    This book provides an overview of the basic concepts and new methods in the emerging scientific area known as quantum plasmas. In the near future, quantum effects in plasmas will be unavoidable, particularly in high density scenarios such as those in the next-generation intense laser-solid density plasma experiment or in compact astrophysics objects. Currently, plasmas are in the forefront of many intriguing questions around the transition from microscopic to macroscopic modeling of charged particle systems. Quantum Plasmas: an Hydrodynamic Approach is devoted to the quantum hydrodynamic model paradigm, which, unlike straight quantum kinetic theory, is much more amenable to investigate the nonlinear realm of quantum plasmas. The reader will have a step-by-step construction of the quantum hydrodynamic method applied to plasmas. The book is intended for specialists in classical plasma physics interested in methods of quantum plasma theory, as well as scientists interested in common aspects of two major areas of...

  18. HYDRODYNAMIC INTERACTIONS BETWEEN TWO BODIES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of model tests, potential flow theory, and viscous Computational Fluid Dynamics (CFD) method, the hydrodynamic interactions between two underwater bodies were investigated to determine the influencing factors, changing rule, interaction mechanism, and appropriate methods describing them. Some special phenomena were discovered in two series of near-wall interaction experiments. The mathematical model and predicting methods were presented for interacting forces near wall, and the calculation results agreed well with the experimental ones. From the comparisons among numerical results with respect to nonviscosity, numerical results with respect to viscosity, and measured results, data on the influence of viscosity on hydrodynamic interactions were obtained. For hydrodynamic interaction related to multi-body unsteady motions with six degrees of freedom that is difficult to simulate in tests, numerical predictions of unsteady interacting forces were given.

  19. Numerical Hydrodynamics in Special Relativity.

    Science.gov (United States)

    Martí, José Maria; Müller, Ewald

    2003-01-01

    This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.

  20. Effect of concentration of dispersed organic matter on optical maturity parameters: Interlaboratory results of the organic matter concentration working group of the ICCP.

    Science.gov (United States)

    Mendonca, Filho J.G.; Araujo, C.V.; Borrego, A.G.; Cook, A.; Flores, D.; Hackley, P.; Hower, J.C.; Kern, M.L.; Kommeren, K.; Kus, J.; Mastalerz, Maria; Mendonca, J.O.; Menezes, T.R.; Newman, J.; Ranasinghe, P.; Souza, I.V.A.F.; Suarez-Ruiz, I.; Ujiie, Y.

    2010-01-01

    The main objective of this work was to study the effect of the kerogen isolation procedures on maturity parameters of organic matter using optical microscopes. This work represents the results of the Organic Matter Concentration Working Group (OMCWG) of the International Committee for Coal and Organic Petrology (ICCP) during the years 2008 and 2009. Four samples have been analysed covering a range of maturity (low and moderate) and terrestrial and marine geological settings. The analyses comprise random vitrinite reflectance measured on both kerogen concentrate and whole rock mounts and fluorescence spectra taken on alginite. Eighteen participants from twelve laboratories from all over the world performed the analyses. Samples of continental settings contained enough vitrinite for participants to record around 50 measurements whereas fewer readings were taken on samples from marine setting. The scatter of results was also larger in the samples of marine origin. Similar vitrinite reflectance values were in general recorded in the whole rock and in the kerogen concentrate. The small deviations of the trend cannot be attributed to the acid treatment involved in kerogen isolation but to reasons related to components identification or to the difficulty to achieve a good polish of samples with high mineral matter content. In samples difficult to polish, vitrinite reflectance was measured on whole rock tended to be lower. The presence or absence of rock fabric affected the selection of the vitrinite population for measurement and this also had an influence in the average value reported and in the scatter of the results. Slightly lower standard deviations were reported for the analyses run on kerogen concentrates. Considering the spectral fluorescence results, it was observed that the ??max presents a shift to higher wavelengths in the kerogen concentrate sample in comparison to the whole-rock sample, thus revealing an influence of preparation methods (acid treatment) on

  1. Influence of composition on optical and dispersion parameters of thermally evaporated non-crystalline Cd{sub 50}S{sub 50−x}Se{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hassanien, A.S., E-mail: a.s.hassanien@gmail.com [Engineering Mathematics and Physics Dept., Faculty of Engineering (Shoubra), Benha University (Egypt); Physics Department, Faculty of Science and Humanities in Ad-Dawadmi, Shaqra University, 11911 (Saudi Arabia); Akl, Alaa A. [Physics Department, Faculty of Science and Humanities in Ad-Dawadmi, Shaqra University, 11911 (Saudi Arabia)

    2015-11-05

    Non-crystalline thin films of chalcogenide Cd{sub 50}S{sub 50−x}Se{sub x} system (30 ≤ x ≤ 50) were obtained by thermal evaporation technique onto a pre-cleaned glass substrate at a vacuum of 8.2 × 10{sup −4} Pa. The deposition rate and film thickness were kept constant at about 8 nm/s and 200 nm, respectively. Amorphous/crystalline nature and chemical composition of films have been checked using X-ray diffraction and energy dispersive X-ray spectroscopy (EDX). Optical properties of thin films were investigated and studied using the corrected transmittance, T(λ) and corrected reflectance, R(λ) measurements. Obtained data reveal that, the indirect optical energy gap (E{sub g}) was decreased from 2.21 to 1.57 eV. On the contrary, Urbach energy (band tail width), E{sub U} was found to be increased from 0.29 to 0.45 eV. This behavior is believed to be associated with the increase of Se-content instead of S-content in the thin films of Cd{sub 50}S{sub 50−x}Se{sub x} system. Chemical bond approach model, CBA was used to analyze the obtained values of E{sub g} and E{sub U}. Optical density, skin depth, extinction coefficient, refractive index and optical conductivity of chalcogenide CdSSe thin films were discussed as functions of Se-content. Using Wemple-DiDomenico single oscillator model, the refractive index dispersion and energy parameters and their dependence on Se content were studied. - Highlights: • Amorphous thin films of thickness 200 nm of Cd{sub 50}S{sub 50−x}Se{sub x} (30 ≤ x ≤ 50) have prepared. • Optical properties, indirect optical energy gap and band tail width were studied. • Chemical bond approach, CBA was used to analyze the obtained values of E{sub g} and E{sub U}. • New data of dispersion refractive index parameters were investigated and discussed.

  2. Anisotropic hydrodynamics: Motivation and methodology

    Energy Technology Data Exchange (ETDEWEB)

    Strickland, Michael

    2014-06-15

    In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.

  3. Hydrodynamics of oceans and atmospheres

    CERN Document Server

    Eckart, Carl

    1960-01-01

    Hydrodynamics of Oceans and Atmospheres is a systematic account of the hydrodynamics of oceans and atmospheres. Topics covered range from the thermodynamic functions of an ideal gas and the thermodynamic coefficients for water to steady motions, the isothermal atmosphere, the thermocline, and the thermosphere. Perturbation equations, field equations, residual equations, and a general theory of rays are also presented. This book is comprised of 17 chapters and begins with an introduction to the basic equations and their solutions, with the aim of illustrating the laws of dynamics. The nonlinear

  4. Abnormal pressures as hydrodynamic phenomena

    Science.gov (United States)

    Neuzil, C.E.

    1995-01-01

    So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author

  5. Validation Hydrodynamic Models of Three Topological Models of Secondary Facultative Ponds

    Directory of Open Access Journals (Sweden)

    Aponte-Reyes Alxander

    2014-10-01

    Full Text Available A methodology was developed to analyze boundary conditions, the size of the mesh and the turbulence of a mathematical model of CFD, which could explain hydrodynamic behavior on facultative stabilization ponds, FSP, built to pilot scale: conventional pond, CP, baffled pond, BP, and baffled-mesh pond, BMP. Models dispersion studies were performed in field for validation, taking samples into and out of the FSP, the information was used to carry out CFD model simulations of the three topologies. Evaluated mesh sizes ranged from 500,000 to 2,000,000 elements. The boundary condition in Pared surface-free slip showed good qualitative behavior and the turbulence model κ–ε Low Reynolds yielded good results. The biomass contained in LFS generates interference on dispersion studies and should be taken into account in assessing the CFD modeling, the tracer injection times, its concentration at the entrance, the effect of wind on CFD, and the flow models adopted as a basis for modeling are parameters to be taken into account for the CFD model validation and calibration.

  6. Non-dissipative hydrodynamics: effective actions versus entropy current

    Science.gov (United States)

    Bhattacharya, Jyotirmoy; Bhattacharyya, Sayantani; Rangamani, Mukund

    2013-02-01

    While conventional hydrodynamics incorporating dissipative effects is hard to derive from an action principle, it is nevertheless possible to construct classical actions when the dissipative terms are switched off. In this note we undertake a systematic exploration of such constructions from an effective field theory approach and argue for the existence of non-trivial second order non-dissipative hydrodynamics involving pure energy-momentum transport. We find these fluids to be characterized by five second-order transport coefficients based on the effective action (a three parameter family is Weyl invariant). On the other hand since all flows of such fluids are non-dissipative, they entail zero entropy production; one can therefore understand them using the entropy current formalism which has provided much insight into hydrodynamic transport. An analysis of the most general stress tensor with zero entropy production however turns out to give a seven parameter family of non-dissipative hydrodynamics (a four parameter sub-family being Weyl invariant). The non-dissipative fluids derived from the effective action approach are a special case of the fluid dynamics constrained by conservation of the entropy current. We speculate on the reasons for the mismatch and potential limitations of the effective action approach.

  7. Hydrodynamic Expansion of Pellicles Caused by e-Beam Heating

    CERN Document Server

    Ho, D

    2000-01-01

    Placing a pellicle in front of a x-ray converter target for radiographic applications can confine the backstreaming ions and target plasma to a shorter channel so that the cumulative effect on e-beam focusing is reduced. The pellicle is subject to heating by e-beam since the pellicle is placed upstream of the target. The calculation of the hydrodynamic expansion, caused by the heating, using the radiation hydrodynamics code LASNEX is presented in this report. Calculations show that mylar pellicles disintegrate at the end of a multi-pulse intense e-beam while beryllium and carbon pellicles remain intact. The expansions for the kapton-carbon multi-layered targets are also examined. Hydrodynamic expansions for pellicles with various e-beam spot radii are calculated for DARHT-II beam parameters. All the simulation results indicate that the backstreaming ions can be stopped.

  8. HYDRODYNAMIC ANALYSIS AND SIMULATION OF A SWIMMING BIONIC ROBOT TUNA

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A dynamic model for undulatory locomotion was proposed to study the swimming mechanism of a developed bionic robot tuna. On the basis of inviscid hydrodynamics and rigid-body dynamics, the momentum and propulsive force required for propelling the swimming robot tuna's flexible body was calculated. By solving the established dynamic equations and efficiency formula, the swimming velocity and propulsive efficiency of the bionic robot tuna were obtained. The relationship between the kinematic parameters of the robot tuna's body curve and the hydrodynamic performances was established and discussed after hydrodynamic simulations. The results presented in this article can be used to increase the swimming speed, propulsive thrust, and the efficiency of underwater vehicles effectively.

  9. Dispersion Modeling.

    Science.gov (United States)

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  10. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  11. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  12. Influence of mass transfer on bubble plume hydrodynamics

    Directory of Open Access Journals (Sweden)

    IRAN E. LIMA NETO

    2016-03-01

    Full Text Available ABSTRACT This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities, both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.

  13. Validating hydrodynamic growth in National Ignition Facility implosions

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, J. L., E-mail: peterson76@llnl.gov; Casey, D. T.; Hurricane, O. A.; Raman, K. S.; Robey, H. F.; Smalyuk, V. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2015-05-15

    We present new hydrodynamic growth experiments at the National Ignition Facility, which extend previous measurements up to Legendre mode 160 and convergence ratio 4, continuing the growth factor dispersion curve comparison of the low foot and high foot pulses reported by Casey et al. [Phys. Rev. E 90, 011102(R) (2014)]. We show that the high foot pulse has lower growth factor and lower growth rate than the low foot pulse. Using novel on-capsule fiducial markers, we observe that mode 160 inverts sign (changes phase) for the high foot pulse, evidence of amplitude oscillations during the Richtmyer-Meshkov phase of a spherically convergent system. Post-shot simulations are consistent with the experimental measurements for all but the shortest wavelength perturbations, reinforcing the validity of radiation hydrodynamic simulations of ablation front growth in inertial confinement fusion capsules.

  14. Hydrodynamic theory for quantum plasmonics: Linear-response dynamics of the inhomogeneous electron gas

    DEFF Research Database (Denmark)

    Yan, Wei

    2015-01-01

    We investigate the hydrodynamic theory of metals, offering systematic studies of the linear-response dynamics for an inhomogeneous electron gas. We include the quantum functional terms of the Thomas-Fermi kinetic energy, the von Weizsa¨cker kinetic energy, and the exchange-correlation Coulomb...... response of complex metallic nanostructures, including quantum effects, by adjusting theory parameters appropriately....... energies under the local density approximation. The advantages, limitations, and possible improvements of the hydrodynamic theory are transparently demonstrated. The roles of various parameters in the theory are identified. We anticipate that the hydrodynamic theory can be applied to investigate the linear...

  15. Hydrodynamics of a quark droplet

    DEFF Research Database (Denmark)

    Bjerrum-Bohr, Johan J.; Mishustin, Igor N.; Døssing, Thomas

    2012-01-01

    We present a simple model of a multi-quark droplet evolution based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure and surface tension. The hadron emission from the droplet is described following Weisskopf's statistical...

  16. Numerical Hydrodynamics in General Relativity

    Directory of Open Access Journals (Sweden)

    Font José A.

    2003-01-01

    Full Text Available The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article, the present update provides additional information on numerical schemes, and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes, and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and hydrodynamic equations and the numerical methodology designed to solve them.

  17. Hydrodynamic Noise and Surface Compliance.

    Science.gov (United States)

    1982-09-08

    Lighthill, 3,4 Ffowcs-Wiiliams, 5-7 and Morse and Ingard .8 Ffowcs-Williams’ 7 excellent review identifies five distinctly different theoretical...Williams, "Hydrodynamic Noise," Annual Review of Fluid Mechanics (Annual Reviews, Palo Alto, CA), vol. 1, 1969, pp. 197-222. 8. P. Morse and K. V. Ingard

  18. Breaking of Galilean Invariance in the Hydrodynamic Formulation of Ferromagnetic Thin Films

    Science.gov (United States)

    Iacocca, Ezio; Silva, T. J.; Hoefer, Mark A.

    2017-01-01

    Microwave magnetodynamics in ferromagnets are often studied in the small-amplitude or weakly nonlinear regime corresponding to modulations of a well-defined magnetic state. However, strongly nonlinear regimes, where the aforementioned approximations are not applicable, have become experimentally accessible. By reinterpreting the governing Landau-Lifshitz equation of motion, we derive an exact set of equations of dispersive hydrodynamic form that are amenable to analytical study even when full nonlinearity and exchange dispersion are included. The resulting equations are shown to, in general, break Galilean invariance. A magnetic Mach number is obtained as a function of static and moving reference frames. The simplest class of solutions are termed uniform hydrodynamic states (UHSs), which exhibit fluidlike behavior including laminar flow at subsonic speeds and the formation of a Mach cone and wave fronts at supersonic speeds. A regime of modulational instability is also possible, where the UHS is violently unstable. The hydrodynamic interpretation opens up novel possibilities in magnetic research.

  19. Evaluation of ensemble atmospheric simulations in oil dispersion models at Itaguai Port region; Avaliacao do uso de resultados numericos de previsao atmosferica por conjunto na modelagem da dispersao de oleo na regiao do Porto de Itaguai

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Renato Goncalves dos; Silva, Mariana P.R.; Silva, Ricardo Marcelo da; Torres Junior, Audalio R. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Lab. de Modelagem de Processos Marinhos e Atmosfericos (LAMMA); Landau, Luiz [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Lab. de Metodos Computacinais em Engenharia (LAMCE); Sa, Reginaldo Ventura de; Hochleitner, Fabio; Correa, Eduardo Barbosa [AQUAMET Meteorologia e Projeto de Sistemas, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    This work discusses the use of numerical prediction using ensemble as boundary condition in pollutants dispersion models, applied in a hypothetical case of an oil spill occurrence in Itaguai Port. The Princeton Ocean Model (POM) has been used to simulate hydrodynamics and NICOIL Eulerian model to forecast oil spill dispersion, and ensemble wind forecast from Global Forecast System (GFS), aiming to assess the importance of this parameter variability in oil dispersion at sea. The wind scenarios using ensemble members has showed significant dispersion when compared to control simulation, demonstrating that the uncertainty in the atmospheric modeling can generate considerable variations in the placement of the final spot of oil. The region of interest was the Sepetiba Bay, located on the southern coast of the Rio de Janeiro state; because of port operations carried out around the Port of Itaguai where they can, eventually, oil leaks occur. (author)

  20. Dispersion compensation based on prism compressor

    Science.gov (United States)

    Liu, Hongying; Lan, Tian; Chen, Xiaomei; Ni, Guoqiang

    2017-04-01

    A prism compressor can compensate dispersion of femtosecond light pulses travelling in air for laser ranging. An accurate expression of the group delay dispersion (GDD) of a prism compressor at arbitrary incident angle and at arbitrary incident point is obtained, which is of benefit to finely compensating dispersion of femtosecond pulses. Influences of several parameters on group delay dispersion are analyzed for the active compensation of dispersion of femtosecond pulses. These expressions are convenient to applications of intra- and extra-cavity dispersion compensation of ultra-short laser pulses, as well as fine compensation of satellite laser ranging and laser altimetry.

  1. Two-stage-six-objective calibration of a hydrodynamic-based sediment transport model for the Mekong Delta

    Science.gov (United States)

    Viet Dung, Nguyen; Van Manh, Nguyen; Merz, Bruno; Apel, Heiko

    2014-05-01

    An advection-dispersive (AD) module for cohesive sediment transport modelling is built up based on a quasi-2D hydrodynamic model (HD) for the whole Mekong Delta which has been recently developed by Dung et al. (2011) using the modelling software DHI MIKE 11. As parameter uncertainty is one main epistemic uncertainty source of modelling work, it needs to be reduced via a calibration-validation process in order to improve the modelling skill of the simulation tool. In this large scale two-component (HD-AD) model, many parameters need to be properly estimated. These parameters include the flow resistance coefficient (Manning's roughness coefficient), longitudinal dispersion coefficient, the free settling velocity and the critical shear stress for deposition. It should be noted that they are spatially distributed over the modelling domain which consists of more than 4000 branches and 26000 computational nodes used to model real channels and floodplains for the vast area in the Mekong Delta. We aim at developing a suitable framework for optimizing these parameters automatically. As the model included a real 1D illustration of river and channel networks and quasi-2D presentation of floodplains being able to represent both main flow and inundation processes, the calibration is, hence, seen from a multi-objective viewpoint using in parallel high-temporal, low-spatial resolution data (gauge data) and low-temporal, high spatial resolution data (remote sensing data). The calibration (and validation) data utilized in this study comprise of gauged time series data along the main channel (water level, flow discharge and suspended sediment concentration), satellite-based flood extent maps and monitored sedimentation deposition rates in several locations. In total, six objective functions as calibration criteria are defined based on these data. Learning from the feature that AD module can be simulated using finer computational time step after HD results are computed, we propose to

  2. Hydrodynamics and Mass Transfer Performance in Supercritical Fluid Extraction Columns

    Institute of Scientific and Technical Information of China (English)

    石冰洁; 张泽廷; 等

    2002-01-01

    New models for describing hydrodynamics and mass transfer performance in supercritical fluid extraction columns were proposed.Those models were proved by experimental data,which were obtained in supercritical fluid extraction packed column,spray column and sieve tray column respectively.The inner diameter of those columns areΦ25mm,These experimental systems include supercritical carbon dioxideisopropanol-water and supercritical carbon dioxide-ethanol-water,in which supercritical carbon dioxide was dispersed phase,and another was continuous phase.The extraction processes were operated with continuous countercurrent flow.The predicted values are agreed well with experimental data.

  3. Effects of hydrodynamic interactions in bacterial swimming.

    Science.gov (United States)

    Chattopadhyay, Suddhashil; Lun Wu, Xiao

    2008-03-01

    The lack of precise experimental data has prevented the investigation of the effects of long range hydrodynamic interactions in bacterial swimming. We perform measurements on various strains of bacteria with the aid of optical tweezers to shed light on this aspect of bacterial motility. Geometrical parameters recorded by fluorescence microscopy are used with theories which model flagella propulsion (Resistive force theory & Lighthill's formulation which includes long range interactions). Comparison of the predictions of these theories with experimental data, observed directly from swimming bacterium, led to the conclusion that while long range inetractions were important for single polar flagellated strains (Vibrio Alginolyticus & Caulobacter Crescentus), local force theory was adequate to describe the swimming of multi-flagellated Esherichia Coli. We performed additional measurements on E. Coli minicells (miniature cells with single polar flagellum) to try and determine the cause of this apparent effect of shielding of long range interactions in multiple flagellated bacteria.

  4. Characterization of an electrochemical pilot-plant filter-press reactor by hydrodynamic and mass transport studies

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Garcia, J.; Frias, A.; Exposito, E.; Montiel, V.; Aldaz, A.; Conesa, J.A.

    2000-05-01

    This work deals with the study of the influence of turbulence promoters in the hydrodynamic and mass transport behavior of a pilot-plant filter-press electrolyzer (a homemade UA200.08 with a 200 cm{sup 2} electrode area) in an undivided configuration. A simple experimental arrangement was used to generate data from electrolytic conductivity measurements in a series of impulse-response experiments. The presence and type of turbulence promoters influence the flow distribution inside the reactor. A new design of a model (presented in a previous work) has been used to analyze the residence time distributions. In this study a new parameter, the turbulence factor, given as N{sub {alpha}}{Phi}{sub {beta}}, was employed to classify the turbulence promoters. The optimization of the parameters indicates that the correct model is dispersed plug-flow behavior with a low axial dispersion that considers exchange between the dead and main zones of the reactor. It is also very interesting to highlight that the information obtained by means of the turbulence factors is similar to that obtained from the values of the mass transport coefficients measured using the limiting current technique.

  5. Brain vascular and hydrodynamic physiology

    Science.gov (United States)

    Tasker, Robert C.

    2013-01-01

    Protecting the brain in vulnerable infants undergoing surgery is a central aspect of perioperative care. Understanding the link between blood flow, oxygen delivery and oxygen consumption leads to a more informed approach to bedside care. In some cases, we need to consider how high can we let the partial pressure of carbon dioxide go before we have concerns about risk of increased cerebral blood volume and change in intracranial hydrodynamics? Alternatively, in almost all such cases, we have to address the question of how low can we let the blood pressure drop before we should be concerned about brain perfusion? This review, provides a basic understanding of brain bioenergetics, hemodynamics, hydrodynamics, autoregulation and vascular homeostasis to changes in blood gases that is fundamental to our thinking about bedside care and monitoring. PMID:24331089

  6. Hydrodynamic interactions in two dimensions

    Science.gov (United States)

    di Leonardo, R.; Keen, S.; Ianni, F.; Leach, J.; Padgett, M. J.; Ruocco, G.

    2008-09-01

    We measure hydrodynamic interactions between colloidal particles confined in a thin sheet of fluid. The reduced dimensionality, compared to a bulk fluid, increases dramatically the range of couplings. Using optical tweezers we force a two body system along the eigenmodes of the mobility tensor and find that eigenmobilities change logarithmically with particle separation. At a hundred radii distance, the mobilities for rigid and relative motions differ by a factor of 2, whereas in bulk fluids, they would be practically indistinguishable. A two dimensional counterpart of Oseen hydrodynamic tensor quantitatively reproduces the observed behavior, once the relevant boundary conditions are recognized. These results highlight the importance of dimensionality for transport and interactions in colloidal systems and proteins in biological membranes.

  7. Algorithm refinement for fluctuating hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.

    2007-07-03

    This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.

  8. Hydrodynamics from Landau initial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Abhisek [University of Tennessee, Knoxville (UTK); Gerhard, Jochen [Frankfurt Institute for Advanced Studies (FIAS), Germany; Torrieri, Giorgio [Universidade Estadual de Campinas, Instituto de Física " Gleb Wataghin" (IFGW), Sao Paulo, Brazil; Read jr, Kenneth F. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Wong, Cheuk-Yin [ORNL

    2015-01-01

    We investigate ideal hydrodynamic evolution, with Landau initial conditions, both in a semi-analytical 1+1D approach and in a numerical code incorporating event-by-event variation with many events and transverse density inhomogeneities. The object of the calculation is to test how fast would a Landau initial condition transition to a commonly used boost-invariant expansion. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of O (20 - 30%) expected at freezeout for most scenarios. Moreover, the deviation from boost-invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, 2+1 dimensional hydrodynamics is inadequate to extract transport coefficients of the quark-gluon plasma. Based on [1, 2

  9. Non-boost-invariant dissipative hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Strickland, Michael; Tinti, Leonardo

    2016-01-01

    The one-dimensional non-boost-invariant evolution of the quark-gluon plasma, presumably produced during the early stages of heavy-ion collisions, is analyzed within the frameworks of viscous and anisotropic hydrodynamics. We neglect transverse dynamics and assume homogeneous conditions in the transverse plane but, differently from Bjorken expansion, we relax longitudinal boost invariance in order to study the rapidity dependence of various hydrodynamical observables. We compare the results obtained using several formulations of second-order viscous hydrodynamics with a recent approach to anisotropic hydrodynamics, which treats the large initial pressure anisotropy in a non-perturbative fashion. The results obtained with second-order viscous hydrodynamics depend on the particular choice of the second-order terms included, which suggests that the latter should be included in the most complete way. The results of anisotropic hydrodynamics and viscous hydrodynamics agree for the central hot part of the system, ho...

  10. Experimental study of hydrodynamic and operation start of a baffled anaerobic reactor treating sewage

    Directory of Open Access Journals (Sweden)

    Ana Carolina Silveira Perico

    2009-12-01

    Full Text Available It is important to provide individual sanitation systems for sewage peri-urban communities or rural areas to minimize impacts on the environment and human health caused by sewage discharge in natura into water resources. In this context, the anaerobic digestion of effluent has been one of the main considered technologies due to easy implementation, material minimization and reduction in waste production. The objective of this work was to study a Baffled Anaerobic Reactor (BAR including its hydrodynamic characteristics, percentile of inoculum to be applied and reactor operation start. It was concluded that the flow is dispersed with 3.84% of dead spaces and that 20% of the cow manure provided best results; however, due to the high fiber content of the manure, its use is not recommended as inoculum. The BAR system, composed of four chambers, presented good performance for sewage treatment of a rural community in terms of organic substance removal (COD, turbidity and solids meeting effluent disposal standards of these parameters considering the Federal and Minas Gerais State legislation, in Brazil, even in a transient phase of operation, at temperatures below 20°C. However, the effluents from the BAR can’t be released into water bodies without other parameters such as nitrogen, phosphorus, fecal coliforms, and others are investigated to be conforming to those standards.

  11. Hydrodynamics of catheter biofilm formation

    CERN Document Server

    Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

    2009-01-01

    A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

  12. Soliton propagation in relativistic hydrodynamics

    CERN Document Server

    Fogaça, D A; 10.1016/j.nuclphysa.2007.03.104

    2013-01-01

    We study the conditions for the formation and propagation of Korteweg-de Vries (KdV) solitons in nuclear matter. In a previous work we have derived a KdV equation from Euler and continuity equations in non-relativistic hydrodynamics. In the present contribution we extend our formalism to relativistic fluids. We present results for a given equation of state, which is based on quantum hadrodynamics (QHD).

  13. Hydrodynamic Evolution of GRB Afterglow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We investigate the dynamics of a relativistic fireball which decelerates as it sweeps up ambient matter. Not only the radiative and adiabatic cases, but also the realistic intermediate cases are calculated. We perform numerical calcula-tion for various ambient media and sizes of beaming expansion, and find that the deceleration radius R0 may play an important role for the hydrodynamic evolution of GRB afterglow.

  14. Hydrodynamic waves in an anomalous charged fluid

    Science.gov (United States)

    Abbasi, Navid; Davody, Ali; Hejazi, Kasra; Rezaei, Zahra

    2016-11-01

    We study the collective excitations in a relativistic fluid with an anomalous U (1) current. In 3 + 1 dimensions at zero chemical potential, in addition to ordinary sound modes we find two propagating modes in presence of an external magnetic field. The first one which is a transverse degenerate mode, propagates with a velocity proportional to the coefficient of gravitational anomaly; this is in fact the Chiral Alfvén wave recently found in [1]. Another one is a wave of density perturbation, namely a chiral magnetic wave (CMW). The velocity dependence of CMW on the chiral anomaly coefficient is well known. We compute the dependence of CMW's velocity on the coefficient of gravitational anomaly as well. We also show that the dissipation splits the degeneracy of CAW. At finite chiral charge density we show that in general there may exist five chiral hydrodynamic waves. Of these five waves, one is the CMW while the other four are mixed Modified Sound-Alfvén waves. It turns out that in propagation transverse to the magnetic field no anomaly effect appears while in parallel to the magnetic field we find sound waves become dispersive due to anomaly.

  15. Recent progress in anisotropic hydrodynamics

    Directory of Open Access Journals (Sweden)

    Strickland Michael

    2017-01-01

    Full Text Available The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, 〈 pL2〉 ≪ 〈 pT2〉. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.

  16. Dispersion and stability of titanium dioxide nanoparticles in aqueous suspension: effects of ultrasonication and concentration.

    Science.gov (United States)

    Qi, J; Ye, Y Y; Wu, J J; Wang, H T; Li, F T

    2013-01-01

    The increasing applications of titanium dioxide (TiO(2)) nanoparticles raise concerns about their potential environmental impacts. To investigate the fate and transport of TiO(2) nanoparticles in aqueous suspension, ultrasonication is widely used for the dispersion of TiO(2) nanoparticles in laboratory-scale studies. There is a pressing need for detailed information on the dispersion and stability of TiO(2) nanoparticles. This study investigated the change of size, zeta potential, and pH of TiO(2) nanoparticles aqueous suspension under different conditions of ultrasonication and concentrations. It was found that the hydrodynamic diameter of TiO(2) nanoparticles decreased with increasing suspension concentration and remained stable for more than 1 hour after sonication, which is enough for experimental research. The pH decreased with increasing nanoparticles concentration. Ultrasonication remarkably improved zeta potential to be above 15 mV for all the samples. Therefore, 20 minutes of ultrasonication (180 W) is sufficient for the dispersion of this rutile TiO(2) nanoparticles suspension, which can remain stable for more than 1 hour. However, the optimum sonication time for TiO(2) nanoparticles dispersion is influenced by many factors, such as TiO(2) nanoparticles concentration, solution chemistry, and sonicator parameters.

  17. Analysis of vibration characteristic for helical gear under hydrodynamic conditions

    Directory of Open Access Journals (Sweden)

    Fuhao Liu

    2017-01-01

    Full Text Available Based on the elasto-hydrodynamic lubrication theory, a 2-degree-of-freedom nonlinear dynamic model of helical gears with double-sided film is proposed, in which the minimum film thickness behaves as a function of load parameters, lubricant parameters, and the geometry of the contact. Then, the comparison of the hysteresis loops in different gear models shows the soundness of the presented model. Using numerical method, the time evolution of lubricant normal force, minimum film thickness, and lubricant stiffness is obtained in order to demonstrate the influence of the driving torque and pinion’s velocity. The results obtained in this article can contribute to the root cause for the gear vibration and show that the hydrodynamic flank friction has almost no influence on the gear system.

  18. Tensor classification of structure in smoothed particle hydrodynamics density fields

    CERN Document Server

    Forgan, Duncan; Lucas, William; Rice, Ken

    2016-01-01

    As hydrodynamic simulations increase in scale and resolution, identifying structures with non-trivial geometries or regions of general interest becomes increasingly challenging. There is a growing need for algorithms that identify a variety of different features in a simulation without requiring a "by-eye" search. We present tensor classification as such a technique for smoothed particle hydrodynamics (SPH). These methods have already been used to great effect in N-Body cosmological simulations, which require smoothing defined as an input free parameter. We show that tensor classification successfully identifies a wide range of structures in SPH density fields using its native smoothing, removing a free parameter from the analysis and preventing the need for tesselation of the density field, as required by some classification algorithms. As examples, we show that tensor classification using the tidal tensor and the velocity shear tensor successfully identifies filaments, shells and sheet structures in giant m...

  19. DYNAMIC CORRECTION OF ROUGHNESS IN THE HYDRODYNAMIC MODEL

    Institute of Scientific and Technical Information of China (English)

    BAO Wei-min; ZHANG Xiao-qin; QU Si-min

    2009-01-01

    Based on the hydrodynamic model and the Xinanjiang model, the river stage forecasting model has been proposed. But its performance is not satisfactory as applied to estuary areas. River roughness is a sensitive parameter in the hydrodynamic model, and its value is related to some substantial uncertainties in the tidal river. According to roughness tests, a new method of roughness dynamic correction was developed to improve the performance of the stage model. The method was focused on the usage of observed data for the studied section, and its parameters were analyzed. Nested with the dynamic correction of roughness, the stage model was applied to the tidal reach of the Caoe River. The results demonstrate that the roughness dynamic correction can improve the simulation accuracy of the stage model, and especially has the capacity of reducing the errors at peak stages.

  20. Hydrodynamic provinces and oceanic connectivity from a transport network help designing marine reserves

    Science.gov (United States)

    Rossi, Vincent; Ser-Giacomi, Enrico; López, Cristóbal; Hernández-García, Emilio

    2014-04-01

    Oceanic dispersal and connectivity have been identified as crucial factors for structuring marine populations and designing marine protected areas (MPAs). Focusing on larval dispersal by ocean currents, we propose an approach coupling Lagrangian transport and new tools from Network Theory to characterize marine connectivity in the Mediterranean basin. Larvae of different pelagic durations and seasons are modeled as passive tracers advected in a simulated oceanic surface flow from which a network of connected areas is constructed. Hydrodynamical provinces extracted from this network are delimited by frontiers which match multiscale oceanographic features. By examining the repeated occurrence of such boundaries, we identify the spatial scales and geographic structures that would control larval dispersal across the entire seascape. Based on these hydrodynamical units, we study novel connectivity metrics for existing reserves. Our results are discussed in the context of ocean biogeography and MPAs design, having ecological and managerial implications.

  1. The circular jump as a hydrodynamic white hole

    CERN Document Server

    Jannes, Gil

    2012-01-01

    Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid as well as on the fluid depth and the wavelength regime. We focus on the shallow-water regime, and discuss the experimental proof that the circular hydraulic jump marks the transition between a supercritical and a subcritical flow regime. This finally confirms a theoretical conjecture formulated by Lord Rayleigh nearly 100 years ago. It also confirms that the circular jump corresponds to the spontaneous formation of a hydrodynamic white hole, with interesting characteristics from the point of view of analogue gravity. We study the dispersive regime, mention some lessons about the trans-Planckian issue and describe possible directions for future work.

  2. Non-equilibrium magnetic colloidal dispersions at liquid-air interfaces: dynamic patterns, magnetic order and self-assembled swimmers.

    Science.gov (United States)

    Snezhko, Alexey

    2011-04-20

    Colloidal dispersions of interacting particles subjected to an external periodic forcing often develop nontrivial self-assembled patterns and complex collective behavior. A fundamental issue is how collective ordering in such non-equilibrium systems arises from the dynamics of discrete interacting components. In addition, from a practical viewpoint, by working in regimes far from equilibrium new self-organized structures which are generally not available through equilibrium thermodynamics can be created. In this review spontaneous self-assembly phenomena in magnetic colloidal dispersions suspended at liquid-air interfaces and driven out of equilibrium by an alternating magnetic field are presented. Experiments reveal a new type of nontrivially ordered self-assembled structures emerging in such systems in a certain range of excitation parameters. These dynamic structures emerge as a result of the competition between magnetic and hydrodynamic forces and have complex unconventional magnetic ordering. Nontrivial self-induced hydrodynamic fields accompany each out-of-equilibrium pattern. Spontaneous symmetry breaking of the self-induced surface flows leading to a formation of self-propelled microstructures has been discovered. Some features of the self-localized structures can be understood in the framework of the amplitude equation (Ginzburg-Landau type equation) for parametric waves coupled to the conservation law equation describing the evolution of the magnetic particle density and the Navier-Stokes equation for hydrodynamic flows. To understand the fundamental microscopic mechanisms governing self-assembly processes in magnetic colloidal dispersions at liquid-air interfaces a first-principle model for a non-equilibrium self-assembly is presented. The latter model allows us to capture in detail the entire process of out-of-equilibrium self-assembly in the system and reproduces most of the observed phenomenology.

  3. Emergence of upstream swimming via a hydrodynamic transition.

    Science.gov (United States)

    Tung, Chih-Kuan; Ardon, Florencia; Roy, Anubhab; Koch, Donald L; Suarez, Susan S; Wu, Mingming

    2015-03-13

    We demonstrate that upstream swimming of sperm emerges via an orientation disorder-order transition. The order parameter, the average orientation of the sperm head against the flow, follows a 0.5 power law with the deviation from the critical flow shear rate (γ-γ_{c}). This transition is successfully explained by a hydrodynamic bifurcation theory, which extends the sperm upstream swimming to a broad class of near surface microswimmers that possess front-back asymmetry and circular motion.

  4. Entropy-limited hydrodynamics: a novel approach to relativistic hydrodynamics

    Science.gov (United States)

    Guercilena, Federico; Radice, David; Rezzolla, Luciano

    2017-07-01

    We present entropy-limited hydrodynamics (ELH): a new approach for the computation of numerical fluxes arising in the discretization of hyperbolic equations in conservation form. ELH is based on the hybridisation of an unfiltered high-order scheme with the first-order Lax-Friedrichs method. The activation of the low-order part of the scheme is driven by a measure of the locally generated entropy inspired by the artificial-viscosity method proposed by Guermond et al. (J. Comput. Phys. 230(11):4248-4267, 2011, doi: 10.1016/j.jcp.2010.11.043). Here, we present ELH in the context of high-order finite-differencing methods and of the equations of general-relativistic hydrodynamics. We study the performance of ELH in a series of classical astrophysical tests in general relativity involving isolated, rotating and nonrotating neutron stars, and including a case of gravitational collapse to black hole. We present a detailed comparison of ELH with the fifth-order monotonicity preserving method MP5 (Suresh and Huynh in J. Comput. Phys. 136(1):83-99, 1997, doi: 10.1006/jcph.1997.5745), one of the most common high-order schemes currently employed in numerical-relativity simulations. We find that ELH achieves comparable and, in many of the cases studied here, better accuracy than more traditional methods at a fraction of the computational cost (up to {˜}50% speedup). Given its accuracy and its simplicity of implementation, ELH is a promising framework for the development of new special- and general-relativistic hydrodynamics codes well adapted for massively parallel supercomputers.

  5. Two-valley Hydrodynamical Models for Electron Transport in Gallium Arsenide: Simulation of Gunn Oscillations

    Directory of Open Access Journals (Sweden)

    A. Marcello Anile

    2002-01-01

    Full Text Available To accurately describe non-stationary carrier transport in GaAs devices, it is necessary to use Monte Carlo methods or hydrodynamical (or energy transport models which incorporate population transfer between valleys.We present here simulations of Gunn oscillations in a GaAs diode based on two-valley hydrodynamical models: the classic Bløtekjær model and two recently developed moment expansion models. Scattering parameters within the models are obtained from homogeneous Monte Carlo simulations, and these are compared against expressions in the literature. Comparisons are made between our hydrodynamical results, existing work, and direct Monte Carlo simulations of the oscillator device.

  6. Exchange Coulomb interaction in nanotubes: Dispersion of Langmuir waves

    CERN Document Server

    Andreev, P A

    2015-01-01

    Microscopic derivation of the Coulomb exchange interaction for electrons located on the nanotubes is presented. Our derivation is based on the many-particle quantum hydrodynamic method. We demonstrate the role of the curvature of the nanocylinders on the force of the exchange interaction. We calculate corresponding dispersion dependencies for electron oscillations on the nanotubes.

  7. Constructing higher-order hydrodynamics: The third order

    Science.gov (United States)

    Grozdanov, Sašo; Kaplis, Nikolaos

    2016-03-01

    Hydrodynamics can be formulated as the gradient expansion of conserved currents in terms of the fundamental fields describing the near-equilibrium fluid flow. In the relativistic case, the Navier-Stokes equations follow from the conservation of the stress-energy tensor to first order in derivatives. In this paper, we go beyond the presently understood second-order hydrodynamics and discuss the systematization of obtaining the hydrodynamic expansion to an arbitrarily high order. As an example of the algorithm that we present, we fully classify the gradient expansion at third order for neutral fluids in four dimensions, thus finding the most general next-to-leading-order corrections to the relativistic Navier-Stokes equations in curved space-time. In doing so, we list 20 new transport coefficient candidates in the conformal case and 68 in the nonconformal case. As we do not consider any constraints that could potentially arise from the local entropy current analysis, this is the maximal possible set of neutral third-order transport coefficients. To investigate the physical implications of these new transport coefficients, we obtain the third-order corrections to the linear dispersion relations that describe the propagation of diffusion and sound waves in relativistic fluids. We also compute the corrections to the scalar (spin-2) two-point correlation function of the third-order stress-energy tensor. Furthermore, as an example of a nonlinear hydrodynamic flow, we calculate the third-order corrections to the energy density of a boost-invariant Bjorken flow. Finally, we apply our field theoretic results to the N =4 supersymmetric Yang-Mills fluid at infinite 't Hooft coupling and an infinite number of colors to find the values of five new linear combinations of the conformal transport coefficients.

  8. Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications

    Energy Technology Data Exchange (ETDEWEB)

    R. Paul Drake

    2005-12-01

    We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.

  9. Galaxy clusters as hydrodynamics laboratories

    Science.gov (United States)

    Roediger, Elke; Sheardown, Alexander; Fish, Thomas; ZuHone, John; Hunt, Matthew; Su, Yuanyuan; Kraft, Ralph P.; Nulsen, Paul; Forman, William R.; Churazov, Eugene; Randall, Scott W.; Jones, Christine; Machacek, Marie E.

    2017-08-01

    The intra-cluster medium (ICM) of galaxy clusters shows a wealth of hydrodynamical features that trace the growth of clusters via the infall of galaxies or smaller subclusters. Such hydrodynamical features include the wakes of the infalling objects as well as the interfaces between the host cluster’s ICM and the atmosphere of the infalling object. Furthermore, the cluster dynamics can be traced by merger shocks, bow shocks, and sloshing motions of the ICM.The characteristics of these dynamical features, e.g., the direction, length, brightness, and temperature of the galaxies' or subclusters' gas tails varies significantly between different objects. This could be due to either dynamical conditions or ICM transport coefficients such as viscosity and thermal conductivity. For example, the cool long gas tails of of some infalling galaxies and groups have been attributed to a substantial ICM viscosity suppressing mixing of the stripped galaxy or group gas with the hotter ambient ICM.Using hydrodynamical simulations of minor mergers we show, however, that these features can be explained naturally by the dynamical conditions of each particular galaxy or group infall. Specifically, we identify observable features to distinguish the first and second infall of a galaxy or group into its host cluster as well as characteristics during apocentre passage. Comparing our simulations with observations, we can explain several puzzling observations such as the long and cold tail of M86 in Virgo and the very long and tangentially oriented tail of the group LEDA 87445 in Hydra A.Using our simulations, we also assess the validity of the stagnation pressure method that is widely used to determine an infalling galaxy's velocity. We show that near pericentre passage the method gives reasonable results, but near apocentre it is not easily applicable.

  10. Dispersion of coupled mode-gap cavities

    CERN Document Server

    Lian, Jin; Yüce, Emre; De Rossi, Sylvain Combrié Alfredo; Mosk, Allard P

    2015-01-01

    The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

  11. Disruptive Innovation in Numerical Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Waltz, Jacob I. [Los Alamos National Laboratory

    2012-09-06

    We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.

  12. Turbulence Models of Hydrodynamic Lubrication

    Institute of Scientific and Technical Information of China (English)

    张直明; 王小静; 孙美丽

    2003-01-01

    The main theoretical turbulence models for application to hydrodynamic lubrication problems were briefly reviewed, and the course of their development and their fundamentals were explained. Predictions by these models on flow fields in turbulent Couette flows and shear-induced countercurrent flows were compared to existing measurements, and Zhang & Zhang' s combined k-ε model was shown to have surpassingly satisfactory results. The method of application of this combined k-ε model to high speed journal bearings and annular seals was summarized, and the predicted results were shown to be satisfactory by comparisons with existing experiments of journal bearings and annular seals.

  13. Highly-anisotropic hydrodynamics for central collisions

    CERN Document Server

    Ryblewski, Radoslaw

    2016-01-01

    The framework of leading-order anisotropic hydrodynamics is supplemented with realistic equation of state and self-consistent freeze-out prescription. The model is applied to central proton-nucleus collisions. The results are compared to those obtained within standard Israel-Stewart second-order viscous hydrodynamics. It is shown that the resulting hadron spectra are highly-sensitive to the hydrodynamic approach that has been used.

  14. Dispersed Indeterminacy

    CERN Document Server

    Fayngold, Moses

    2013-01-01

    A state of a single particle can be represented by a quantum blob in the corresponding phase space, or a patch (granule) in its 2-D subspace. Its area is frequently stated to be no less than, implying that such a granule is an indivisible quantum of the 2-D phase space. But this is generally not true, as is evident, for instance, from representation of some states in the basis of innately discrete observables like angular momentum. Here we consider some dispersed states involving the evanescent waves different from that in the total internal reflection. Such states are represented by a set of separated granules with individual areas, but with the total indeterminacy . An idealized model has a discrete Wigner function and is described by a superposition of eigenstates with eigenvalues and forming an infinite periodic array of dots on the phase plane. The question about the total indeterminacy in such state is discussed. We argue that the eigenstates corresponding to the considered EW cannot be singled out by a...

  15. The fractal characteristic change in the Huanghe River Estuary due to the hydrodynamic conditions' variation

    Institute of Scientific and Technical Information of China (English)

    Jia Yonggang; Fu Yuanbin; Xu Guohui; Shan Hongxian; Cao Xueqing

    2003-01-01

    The study area lies in the subaqueous delta, which came into being in 1964~1976. One oil-field road has been built for exploring petroleum to form a wave barrier. The hydrodynamic conditions on the north side of the road are relatively violent, on the contrary the hydrodynamic conditions on the south side of the road are nearly placid. This makes the study area a natural laboratory for studying the influence of the hydrodynamic conditions on the fractal characteristics of the tidal flat. Selecting an area is named Case Ⅰ on the side of stronger hydrodynamic activities and an area is named Case Ⅱ on the other side. Measuring the topography and sampling and analyzing the granulometrical composition, it is found that the hydrodynamic conditions have fatal influence on the surface fractal dimensions and the granulometrical fractal dimensions of the area. In Case Ⅰ, which has strong hydrodynamic conditions, the surface fractal dimensions are obviously larger than those of Case Ⅱ, and the granulometrical fractal dimensions are relatively smaller than those of Case Ⅱ, the surface fractal dimensions of Case Ⅰ decrease quickly with the increase of grid size; the granulometrical fractal dimensions are disperse, while the hydrodynamic conditions of Case Ⅱ are just reverse. A sampling line and a core sampling on each side of the road are selected. It is found that on the south side of the road the granulometrical fractal dimensions vary regularly in the line and with the depth, the farther apart from the road, the smaller the fractal dimensions, and the deeper the sampling position the larger the fractal dimensions, while granulometrical fractal dimensions on the north side of the road have no such regularity pattern. The mechanism of the influence of the hydrodynamic conditions on the fractal characteristics is discussed.

  16. Warm dense mater: another application for pulsed power hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Reinovsky, Robert Emil [Los Alamos National Laboratory

    2009-01-01

    Pulsed Power Hydrodynamics (PPH) is an application of low-impedance pulsed power, and high magnetic field technology to the study of advanced hydrodynamic problems, instabilities, turbulence, and material properties. PPH can potentially be applied to the study of the properties of warm dense matter (WDM) as well. Exploration of the properties of warm dense matter such as equation of state, viscosity, conductivity is an emerging area of study focused on the behavior of matter at density near solid density (from 10% of solid density to slightly above solid density) and modest temperatures ({approx}1-10 eV). Conditions characteristic of WDM are difficult to obtain, and even more difficult to diagnose. One approach to producing WDM uses laser or particle beam heating of very small quantities of matter on timescales short compared to the subsequent hydrodynamic expansion timescales (isochoric heating) and a vigorous community of researchers are applying these techniques. Pulsed power hydrodynamic techniques, such as large convergence liner compression of a large volume, modest density, low temperature plasma to densities approaching solid density or through multiple shock compression and heating of normal density material between a massive, high density, energetic liner and a high density central 'anvil' are possible ways to reach relevant conditions. Another avenue to WDM conditions is through the explosion and subsequent expansion of a conductor (wire) against a high pressure (density) gas background (isobaric expansion) techniques. However, both techniques demand substantial energy, proper power conditioning and delivery, and an understanding of the hydrodynamic and instability processes that limit each technique. In this paper we will examine the challenges to pulsed power technology and to pulsed power systems presented by the opportunity to explore this interesting region of parameter space.

  17. Axial dispersion, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column by radiotracer residence time distribution analysis

    Energy Technology Data Exchange (ETDEWEB)

    Din, Ghiyas Ud [Department of Nuclear Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), P.O. Nilore, Islamabad (Pakistan); Isotope Applications Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad (Pakistan)], E-mail: fac192@pieas.edu.pk; Chughtai, Imran Rafiq; Inayat, Mansoor Hameed [Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), P.O. Nilore, Islamabad (Pakistan); Khan, Iqbal Hussain [Isotope Applications Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad (Pakistan)

    2008-12-15

    Axial dispersion, holdup and slip velocity of dispersed phase have been investigated for a range of dispersed and continuous phase superficial velocities in a pulsed sieve plate extraction column using radiotracer residence time distribution (RTD) analysis. Axial dispersion model (ADM) was used to simulate the hydrodynamics of the system. It has been observed that increase in dispersed phase superficial velocity results in a decrease in its axial dispersion and increase in its slip velocity while its holdup increases till a maximum asymptotic value is achieved. An increase in superficial velocity of continuous phase increases the axial dispersion and holdup of dispersed phase until a maximum value is obtained, while slip velocity of dispersed phase is found to decrease in the beginning and then it increases with increase in superficial velocity of continuous phase.

  18. Modeling the dispersion in electromechanically coupled myocardium

    Science.gov (United States)

    Eriksson, Thomas S. E.; Prassl, Anton J.; Plank, Gernot; Holzapfel, Gerhard A.

    2014-01-01

    SUMMARY We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure–volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases. PMID:23868817

  19. Modeling the dispersion in electromechanically coupled myocardium.

    Science.gov (United States)

    Eriksson, Thomas S E; Prassl, Anton J; Plank, Gernot; Holzapfel, Gerhard A

    2013-11-01

    We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure-volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases.

  20. Some open questions in hydrodynamics

    CERN Document Server

    Dyndal, Mateusz

    2014-01-01

    When speaking of unsolved problems in physics, this is surprising at first glance to discuss the case of fluid mechanics. However, there are many deep open questions that come with the theory of fluid mechanics. In this paper, we discuss some of them that we classify in two categories, the long term behavior of solutions of equations of hydrodynamics and the definition of initial (boundary) conditions. The first set of questions come with the non-relativistic theory based on the Navier-Stokes equations. Starting from smooth initial conditions, the purpose is to understand if solutions of Navier-Stokes equations remain smooth with the time evolution. Existence for just a finite time would imply the evolution of finite time singularities, which would have a major influence on the development of turbulent phenomena. The second set of questions come with the relativistic theory of hydrodynamics. There is an accumulating evidence that this theory may be relevant for the description of the medium created in high en...

  1. Hydrodynamic behaviour of Lattice Boltzmann and Lattice BGK models

    CERN Document Server

    Behrend, O; Warren, P

    1993-01-01

    Abstract: We present a numerical analysis of the validity of classical and generalized hydrodynamics for Lattice Boltzmann Equation (LBE) and Lattice BGK methods in two and three dimensions, as a function of the collision parameters of these models. Our analysis is based on the wave-number dependence of the evolution operator. Good ranges of validity are found for BGK models as long as the relaxation time is chosen smaller than or equal to unity. The additional freedom in the choice of collision parameters for LBE models does not seem to give significant improvement.

  2. Hydrodynamic Behavior of Three-Phase Airlift Loop Slurry Reactor

    Institute of Scientific and Technical Information of China (English)

    任飞; 王金福; 王铁峰; 金涌

    2002-01-01

    A novel fiber optic probe system and a set of commercial ultrasonic Doppler velocimeters have been used to study the hydrodynamic behavior of a three-phase airlift loop (TPAL) slurry reactor. Experiments have been carried out in a loop reactor with 100 mm inner diameter and 2.5 m height, in which air, tap water and silica gel particles are used as the gas, liquid and solid phase, respectively. The radial profile of gas holdup, bubble size, bubble rising velocity, liquid circulating velocity, and the influence of the main operating conditions such as superficial gas velocity and solids concentration have been studied experimentally in the TPAL slurry reactor. The experimental results show that the bubble characteristics are different in various flow regimes and the radial profiles of some hydrodynamic parameters in the TPAL slurry reactor are more uniform than those in traditional three-phase reactors. The distribution of the bubble size and bubble rising velocity can be described by a lognormal function. The influence of superficial gas velocity on the hydrodynamic parameters is more remarkable than that of the solids concentration.

  3. Hydrodynamic Analysis of the Spherical Underwater Robot SUR-II

    Directory of Open Access Journals (Sweden)

    Chunfeng Yue

    2013-05-01

    Full Text Available Abstract This paper describes the development of the second-generation Spherical Underwater Robot (SUR-II. The new SUR-II has an improved propulsion system structure, resulting in better performance compared with the original design. This paper focuses on the characteristics of the water-jet thruster and the spherical hull of the SUR-II. To analyse its hydrodynamic characteristics, the main hydrodynamic parameters of the SUR-II were estimated based on two reasonable assumptions and a reasonable dynamic equation was proposed to describe the relationship between force and velocity. Drag coefficients were calculated separately for vertical and horizontal motions due to the fin on the robot's equator and the holes in the robot's hull. The holes had a particularly adverse effect on the horizontal drag coefficient. A hydrodynamic analysis using computational fluid dynamics was then carried out to verify the estimated parameters. The velocity vectors, pressure contours and drag coefficient for each state of motion were obtained. Finally, the propulsive force was determined experimentally to verify the theoretical calculations and simulation results.

  4. Extreme hydrodynamic atmospheric loss near the critical thermal escape regime

    CERN Document Server

    Erkaev, N V; Odert, P; Kulikov, Yu N; Kislyakova, K G

    2015-01-01

    By considering martian-like planetary embryos inside the habitable zone of solar-like stars we study the behavior of the hydrodynamic atmospheric escape of hydrogen for small values of the Jeans escape parameter $\\beta < 3$, near the base of the thermosphere, that is defined as a ratio of the gravitational and thermal energy. Our study is based on a 1-D hydrodynamic upper atmosphere model that calculates the volume heating rate in a hydrogen dominated thermosphere due to the absorption of the stellar soft X-ray and extreme ultraviolet (XUV) flux. We find that when the $\\beta$ value near the mesopause/homopause level exceeds a critical value of $\\sim$2.5, there exists a steady hydrodynamic solution with a smooth transition from subsonic to supersonic flow. For a fixed XUV flux, the escape rate of the upper atmosphere is an increasing function of the temperature at the lower boundary. Our model results indicate a crucial enhancement of the atmospheric escape rate, when the Jeans escape parameter $\\beta$ decr...

  5. Safety assessment of liver-targeted hydrodynamic gene delivery in dogs.

    Directory of Open Access Journals (Sweden)

    Kenya Kamimura

    Full Text Available Evidence in support of safety of a gene delivery procedure is essential toward gene therapy. Previous studies using the hydrodynamics-based procedure primarily focus on gene delivery efficiency or gene function analysis in mice. The current study focuses on an assessment of the safety of computer-controlled and liver-targeted hydrodynamic gene delivery in dogs as the first step toward hydrodynamic gene therapy in clinic. We demonstrate that the impacts of the hydrodynamic procedure were limited in the injected region and the influences were transient. Histological examination and the hepatic microcirculation measurement using reflectance spectrophotometry reveal that the liver-specific impact of the procedure involves a transient expansion of the liver sinusoids. No systemic damage or toxicity was observed. Physiological parameters, including electrocardiogram, heart rate, blood pressure, oxygen saturation, and body temperature, remained in normal ranges during and after hydrodynamic injection. Body weight was also examined to assess the long-term effects of the procedure in animals who underwent 3 hydrodynamic injections in 6 weeks with 2-week time interval in between. Serum biochemistry analysis showed a transient increase in liver enzymes and a few cytokines upon injection. These results demonstrate that image-guided, liver-specific hydrodynamic gene delivery is safe.

  6. Light dispersion in space

    Science.gov (United States)

    Barbosa, L. C.

    2015-09-01

    Considering an idea of F. Arago in 1853 regarding light dispersion through the light ether in the interstellar space, this paper presents a new idea on an alternative interpretation of the cosmological red shift of the galaxies in the universe. The model is based on an analogy with the temporal material dispersion that occurs with light in the optical fiber core. Since intergalactic space is transparent, according to the model, this phenomenon is related to the gravitational potential existing in the whole space. Thus, it is possible to find a new interpretation to Hubble's constant. In space, light undergoes a dispersion process in its path, which is interpreted by a red shift equation of the type Δz = HL, since H = (d2n/dλ2 Δv Δλ), where H means the Hubble constant, n is the refractive index of the intergalactic space, Δλ is the spectral width of the extragalactic source, and Δv is the variation of the speed of light caused by the gravitational potential. We observe that this "constant" is governed by three new parameters. Light traveling the intergalactic space undergoes red shift due to this mechanism, while light amplitude decreases with time, and the wavelength always increases, thus producing the same type of behavior given by Hubble's Law. It can be demonstrated that the dark matter phenomenon is produced by the apparent speed of light of the stars on the periphery of the galaxies, without the existence of dark energy. Based on this new idea, the model of the universe is static, lacking expansion. Other phenomena may be interpreted based on this new model of the universe. We have what we call temporal gravitational dispersion of light in space produced by the variations of the speed of light, due to the presence of the gravitational potential in the whole space.

  7. Hydrodynamic interaction induced mechanical properties of SGF reinforced polyethersulfone

    Science.gov (United States)

    Munirathnamma, L. M.; Ningaraju, S.; Kumar, K. V. Aneesh; Ravikumar, H. B.

    2016-05-01

    In order to explore the effect of short glass fiber (SGF) reinforcement on the mechanical properties of Polyethersulfone (PES), short glass fibers of different proportion (10 - 40 wt %) are reinforced into PES matrix. The free volume distribution of SGFR-PES composites derived from CONTIN-PALS2 program exhibits the narrow full width at half maximum (FWHM). This is attributed to the improved adhesion resulted by the hydrodynamic interaction between the polymeric chains of PES matrix and SGF. The hydrodynamic interaction parameter (h) decreases as a function of SGF wt% and becomes more negative for 40 wt% SGFR-PES composites suggest the generation of excess friction at the interface. This improves the adhesion between the polymeric chains of PES matrix and SGF and hence the mechanical strength of the SGFR-PES composites.

  8. Dynamics Models of Interacting Torques of Hydrodynamic Retarder Braking Process

    Directory of Open Access Journals (Sweden)

    Wenhao Shen

    2013-01-01

    Full Text Available Hydrodynamic retarder is a kind of assist braking device, which can transfer the vehicle kinetic energy into the heat energy of working medium. There are complicated three-dimensional viscous incompressible turbulent flows in hydrodynamic retarder, so that it is difficult to represent the parameters changing phenomenon and investigate the interactional law. In order to develop a kind of reliable theoretical model for internal flow field, in this study, the dynamics models of interacting torques between impellers and working fluid were constructed based on braking energy transfer principle by using Euler theory to describe the flow state in view of time scale. The model can truly represent the dynamic braking process.

  9. The hydrodynamics of galaxy formation on Kiloparsec scales

    Science.gov (United States)

    Norman, Michael L.; Anninos, Wenbo Yuan; Centrella, Joan

    1993-01-01

    Two dimensional numerical simulations of Zeldovich pancake fragmentation in a dark matter dominated universe were carried out to study the hydrodynamical and gravitational effects on the formation of structures such as protogalaxies. Preliminary results were given in Yuan, Centrella and, Norman (1991). Here we report a more exhaustive study to determine the sensitivity of protogalaxies to input parameters. The numerical code we used for the simulations combines the hydrodynamical code ZEUS-2D (Stone and Norman, 1992) which was modified to include the expansion of the universe and radiative cooling of the gas with a particle-mesh code which follows the motion of dark matter particles. The resulting hybrid code is able to handle highly nonuniform grids which we utilized to obtain a high resolution (much greater than 1 kpc) in the dense region of the pancake.

  10. Probing the Hydrodynamic Limit of (Super)gravity

    CERN Document Server

    Di Dato, Adriana; Pedersen, Andreas Vigand

    2015-01-01

    We study the long-wavelength effective description of two general classes of charged dilatonic (asymptotically flat) black p-branes including D/NS/M-branes in ten and eleven dimensional supergravity. In particular, we consider gravitational brane solutions in a hydrodynamic derivative expansion (to first order) for arbitrary dilaton coupling and for general brane and co-dimension and determine their effective electro-fluid-dynamic descriptions by exacting the characterizing transport coefficients. We also investigate the stability properties of the corresponding hydrodynamic systems by analyzing their response to small long-wavelength perturbations. For branes carrying unsmeared charge, we find that in a certain regime of parameter space there exists a branch of stable charged configurations. This is in accordance with the expectation that D/NS/M-branes have stable configurations, except for the D5, D6, and NS5. In contrast, we find that Maxwell charged brane configurations are Gregory-Laflamme unstable indep...

  11. Hydrodynamic Characteristics in an External Loop Airlift Slurry Reactor

    Institute of Scientific and Technical Information of China (English)

    Bian Qing; Tang Xiaojin; Hu Lifeng; Wang Shaobing; Zhang Zhanzhu

    2016-01-01

    Three different types of gas distributors were used in an external loop airlift slurry reactor to investigate the hydrodynamic characteristics. To predict the important hydrodynamic parameters, such as the total gas holdup, the slurry circulating velocity, the bubble size distribution, and the slip velocity between the gas phase and the slurry phase, the cor-relations are developed. The calculated results fit the experimental data very well. According to the influence of the solid holdup on the bubble size, the fluid flow in the reactor can be divided into two regimes, while a 10% value is regarded as the critical solid holdup value. Whenεs is≤10%, the bubble size is determined by both the gas phase and the slurry phase. Whenεs is ≥10%, the bubble size is determined mainly by the slurry phase. By analyzing the relationship between the slip velocity and the gas holdup, the bubble coalescence plays a key role in the slurry reactor.

  12. A quantification of hydrodynamical effects on protoplanetary dust growth

    CERN Document Server

    Sellentin, E; Windmark, F; Dullemond, C P

    2013-01-01

    Context. The growth process of dust particles in protoplanetary disks can be modeled via numerical dust coagulation codes. In this approach, physical effects that dominate the dust growth process often must be implemented in a parameterized form. Due to a lack of these parameterizations, existing studies of dust coagulation have ignored the effects a hydrodynamical gas flow can have on grain growth, even though it is often argued that the flow could significantly contribute either positively or negatively to the growth process. Aims. We intend to provide a quantification of hydrodynamical effects on the growth of dust particles, such that these effects can be parameterized and implemented in a dust coagulation code. Methods. We numerically integrate the trajectories of small dust particles in the flow of disk gas around a proto-planetesimal, sampling a large parameter space in proto-planetesimal radii, headwind velocities, and dust stopping times. Results. The gas flow deflects most particles away from the pr...

  13. 3-D hydrodynamic simulations of convection in A stars

    CERN Document Server

    Kochukhov, O; Piskunov, N; Steffen, M

    2006-01-01

    Broadening and asymmetry of spectral lines in slowly rotating late A-type stars provide evidence for high-amplitude convective motions. The properties of turbulence observed in the A-star atmospheres are not understood theoretically and contradict results of previous numerical simulations of convection. Here we describe an ongoing effort to understand the puzzling convection signatures of A stars with the help of 3-D hydrodynamic simulations. Our approach combines realistic spectrum synthesis and non-grey hydrodynamic models computed with the CO5BOLD code. We discuss these theoretical predictions and confront them with high-resolution spectra of A stars. Our models have, for the first time, succeeded in reproducing the observed profiles of weak spectral lines without introducing fudge broadening parameters.

  14. Spatial dispersion in two-dimensional plasmonic crystals: Large blueshifts promoted by diffraction anomalies

    Science.gov (United States)

    David, Christin; Christensen, Johan; Mortensen, N. Asger

    2016-10-01

    We develop a methodology to incorporate nonlocal optical response of the free electron gas due to quantum-interaction effects in metal components of periodic two-dimensional plasmonic crystals and study the impact of spatial dispersion on promising building blocks for photonic circuits. Within the framework of the hydrodynamic model, we observe significant changes with respect to the commonly employed local-response approximation, but also in comparison with homogeneous metal films where nonlocal effects have previously been considered. Notable are the emergence of a contribution from nonlocality at normal incidence and the surprisingly large structural parameters at which finite blueshifts are observable, which we attribute to diffraction that offers nonvanishing in-plane wave vector components and increases the penetration depth of longitudinal (nonlocal) modes.

  15. Higher-Harmonic Collective Modes in a Trapped Gas from Second-Order Hydrodynamics

    CERN Document Server

    Lewis, William E

    2016-01-01

    Utilizing a second-order hydrodynamics formalism, the dispersion relations for the frequencies and damping rates of collective oscillations as well as spatial structure of these modes up to the decapole oscillation in both two- and three- dimensional gas geometries are calculated. In addition to higher-order modes, the formalism also gives rise to purely damped "non-hydrodynamic" modes. We calculate the amplitude of the various modes for both symmetric and asymmetric trap quenches, finding excellent agreement with an exact quantum mechanical calculation. We find that higher-order hydrodynamic modes are more sensitive to the value of shear viscosity, which may be of interest for the precision extraction of transport coefficients in Fermi gas systems.

  16. A study on the collective behavior of chiral plasma using first and second order conformal hydrodynamics

    CERN Document Server

    Pandey, Arun Kumar

    2016-01-01

    We study the collective behaviour of a chiral plasma, for the first and second order conformal hydrodynamics. We have shown that in the early Universe, when the Universe was in thermal equilibrium and there was an asymmetry in the number densities of right and left handed particles, few modes grow exponentially for the values of wave number $k \\leq \\xi^B$. However, by using conformal first order hydro, we have shown that in a quasi-equilibrium state of the chiral plasma, waves moving parallel or perpendicular to the background magnetic field, get split into two modes similar to the fast and slow hydrodynamic modes in the standard plasma. However, for the second order conformal hydrodynamics, dispersion relation has a series of terms proportional to different powers of $k$. These terms are in accordance with the results obtained using ADS/CFT correspondence.

  17. Recent extensions of the residence time distribution concept: unsteady state conditions and hydrodynamic model developments

    Directory of Open Access Journals (Sweden)

    S. Claudel

    2000-12-01

    Full Text Available Two recent extensions of the residence time distribution concept are developed. The first one concerns the use of this method under transient conditions, a concept theoretically treated but rarely confirm by relevant experiments. In the present work, two experimental set-ups have been used to verify some limits of the concept. The second extension is devoted to the development of hydrodynamic models. Up to now, the hydrodynamics of the process are either determined by simple models (mixing cells in series, plug flow reactor with axial dispersion or by the complex calculation of the velocity profile obtained via the Navier-Stokes equations. An alternative is to develop a hydrodynamic model by use of a complex network of interconnected elementary reactors. Such models should be simple enough to be derived easily and sufficiently complex to give a good representation of the behavior of the process.

  18. Relativistic Hydrodynamics for Heavy-Ion Collisions

    Science.gov (United States)

    Ollitrault, Jean-Yves

    2008-01-01

    Relativistic hydrodynamics is essential to our current understanding of nucleus-nucleus collisions at ultrarelativistic energies (current experiments at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN Large Hadron Collider). This is an introduction to relativistic hydrodynamics for graduate students. It includes a detailed…

  19. Hydrodynamic models of a Cepheid atmosphere

    Science.gov (United States)

    Karp, A. H.

    1975-01-01

    Instead of computing a large number of coarsely zoned hydrodynamic models covering the entire atmospheric instability strip, the author computed a single model as well as computer limitations allow. The implicit hydrodynamic code of Kutter and Sparks was modified to include radiative transfer effects in optically thin zones.

  20. Hydrodynamic correlation functions in nematic liquid crystals

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.

    1976-01-01

    The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t

  1. Hydrodynamic Overview at Hot Quarks 2016

    CERN Document Server

    Noronha-Hostler, Jacquelyn

    2016-01-01

    This presents an overview of relativistic hydrodynamic modeling in heavy-ion collisions prepared for Hot Quarks 2016, at South Padre Island, TX, USA. The influence of the initial state and viscosity on various experimental observables are discussed. Specific problems that arise in the hydrodynamical modeling at the Beam Energy Scan are briefly discussed.

  2. Measurement of the hydrodynamic resistance of microdroplets.

    Science.gov (United States)

    Jakiela, Slawomir

    2016-10-07

    Here, we demonstrate a novel method of measurement which determines precisely the hydrodynamic resistance of a droplet flowing through a channel. The obtained results show that the hydrodynamic resistance of a droplet in a microchannel achieves its maximum for lengths of the droplet ranging from 3w to 4w and that interactions between beads in a train exist.

  3. Hydrodynamic correlation functions in nematic liquid crystals

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.

    1976-01-01

    The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t

  4. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  5. Zero Dispersion Optical Fibres for High Data Rate Systems

    Directory of Open Access Journals (Sweden)

    V. V. Rampal

    1981-07-01

    Full Text Available The different dispersion parameters that contribute to the pulse spreading in a single mode fibre are discussed with particular reference to the possibility of reducing the total dispersion to zero and increasing the bandwidth and repeater spacing.

  6. Quasiparticle anisotropic hydrodynamics for central collisions

    CERN Document Server

    Alqahtani, Mubarak; Strickland, Michael

    2016-01-01

    We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative...

  7. Hydrodynamic Approaches in Relativistic Heavy Ion Reactions

    CERN Document Server

    de Souza, Rafael Derradi; Kodama, Takeshi

    2016-01-01

    We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation with the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to...

  8. Hydrodynamics research of wastewater treatment bioreactors

    Institute of Scientific and Technical Information of China (English)

    REN Nan-qi; ZHANG Bing; ZHOU Xue-fei

    2009-01-01

    To optimize the design and improve the performance of wastewater treatment bioreactors, the review concerning the hydrodynamics explored by theoretical equations, process experiments, modeling of the hydrody-namics and flow field measurement is presented. Results of different kinds of experiments show that the hydro-dynamic characteristics can affect sludge characteristics, mass transfer and reactor performance significantly. A-long with the development of theoretical equations, turbulence models including large eddy simulation models and Reynolds-averaged Navier-Stokes (RANS) models are widely used at present. Standard and modified k-ε models are the most widely used eddy viscosity turbulence models for simulating flows in bioreactors. Numericalsimulation of hydrodynamics is proved to be efficient for optimizing design and operation. The development of measurement techniques with high accuracy and low intrusion enables the flow filed in the bioreactors to be transparent. Integration of both numerical simulation and experimental measurement can describe the hydrody-namics very well.

  9. Hydrodynamic Nambu Brackets derived by Geometric Constraints

    CERN Document Server

    Blender, Richard

    2015-01-01

    A geometric approach to derive the Nambu brackets for ideal two-dimensional (2D) hydrodynamics is suggested. The derivation is based on two-forms with vanishing integrals in a periodic domain, and with resulting dynamics constrained by an orthogonality condition. As a result, 2D hydrodynamics with vorticity as dynamic variable emerges as a generic model, with conservation laws which can be interpreted as enstrophy and energy functionals. Generalized forms like surface quasi-geostrophy and fractional Poisson equations for the stream-function are also included as results from the derivation. The formalism is extended to a hydrodynamic system coupled to a second degree of freedom, with the Rayleigh-B\\'{e}nard convection as an example. This system is reformulated in terms of constitutive conservation laws with two additive brackets which represent individual processes: a first representing inviscid 2D hydrodynamics, and a second representing the coupling between hydrodynamics and thermodynamics. The results can b...

  10. Hydrodynamics of evaporating sessile drops

    CERN Document Server

    Barash, L Yu

    2010-01-01

    Several dynamical stages of the Marangoni convection of an evaporating sessile drop are obtained. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop and the diffusion of vapor in air. The stages are characterized by different number of vortices in the drop and the spatial location of vortices. During the early stage the array of vortices arises near a surface of the drop and induces a non-monotonic spatial distribution of the temperature over the drop surface. The number of near-surface vortices in the drop is controlled by the Marangoni cell size, which is calculated similar to that given by Pearson for flat fluid layers. The number of vortices quickly decreases with time, resulting in three bulk vortices in the intermediate stage. The vortex structure finally evolves into the single convection vortex in the drop, existing during about 1/2 of the evaporation time.

  11. Decoherent Histories and Hydrodynamic Equations

    CERN Document Server

    Halliwell, J J

    1998-01-01

    For a system consisting of a large collection of particles, a set of variables that will generally become effectively classical are the local densities (number, momentum, energy). That is, in the context of the decoherent histories approach to quantum theory, it is expected that histories of these variables will be approximately decoherent, and that their probabilites will be strongly peaked about hydrodynamic equations. This possibility is explored for the case of the diffusion of the number density of a dilute concentration of foreign particles in a fluid. It is shown that, for certain physically reasonable initial states, the probabilities for histories of number density are strongly peaked about evolution according to the diffusion equation. Decoherence of these histories is also shown for a class of initial states which includes non-trivial superpositions of number density. Histories of phase space densities are also discussed. The case of histories of number, momentum and energy density for more general...

  12. Hydrodynamic stability and stellar oscillations

    Indian Academy of Sciences (India)

    H M Antia

    2011-07-01

    Chandrasekhar’s monograph on Hydrodynamic and hydromagnetic stability, published in 1961, is a standard reference on linear stability theory. It gives a detailed account of stability of fluid flow in a variety of circumstances, including convection, stability of Couette flow, Rayleigh–Taylor instability, Kelvin–Helmholtz instability as well as the Jean’s instability for star formation. In most cases he has extended these studies to include effects of rotation and magnetic field. In a later paper he has given a variational formulation for equations of non-radial stellar oscillations. This forms the basis for helioseismic inversion techniques as well as extension to include the effect of rotation, magnetic field and other large-scale flows using a perturbation treatment.

  13. Integration of quantum hydrodynamical equation

    Science.gov (United States)

    Ulyanova, Vera G.; Sanin, Andrey L.

    2007-04-01

    Quantum hydrodynamics equations describing the dynamics of quantum fluid are a subject of this report (QFD).These equations can be used to decide the wide class of problem. But there are the calculated difficulties for the equations, which take place for nonlinear hyperbolic systems. In this connection, It is necessary to impose the additional restrictions which assure the existence and unique of solutions. As test sample, we use the free wave packet and study its behavior at the different initial and boundary conditions. The calculations of wave packet propagation cause in numerical algorithm the division. In numerical algorithm at the calculations of wave packet propagation, there arises the problem of division by zero. To overcome this problem we have to sew together discrete numerical and analytical continuous solutions on the boundary. We demonstrate here for the free wave packet that the numerical solution corresponds to the analytical solution.

  14. Particle hydrodynamics with tessellation techniques

    CERN Document Server

    Hess, S

    2009-01-01

    Lagrangian smoothed particle hydrodynamics (SPH) is a well-established approach to model fluids in astrophysical problems, thanks to its geometric flexibility and ability to automatically adjust the spatial resolution to the clumping of matter. However, a number of recent studies have emphasized inaccuracies of SPH in the treatment of fluid instabilities. The origin of these numerical problems can be traced back to spurious surface effects across contact discontinuities, and to SPH's inherent prevention of mixing at the particle level. We here investigate a new fluid particle model where the density estimate is carried out with the help of an auxiliary mesh constructed as the Voronoi tessellation of the simulation particles instead of an adaptive smoothing kernel. This Voronoi-based approach improves the ability of the scheme to represent sharp contact discontinuities. We show that this eliminates spurious surface tension effects present in SPH and that play a role in suppressing certain fluid instabilities. ...

  15. Nonstandard Gaits in Unsteady Hydrodynamics

    Science.gov (United States)

    Fairchild, Michael; Rowley, Clarence

    2016-11-01

    Marine biology has long inspired the design and engineering of underwater vehicles. The literature examining the kinematics and dynamics of fishes, ranging from undulatory anguilliform swimmers to oscillatory ostraciiform ones, is vast. Past numerical studies of these organisms have principally focused on gaits characterized by sinusoidal pitching and heaving motions. It is conceivable that more sophisticated gaits could perform better in some respects, for example as measured by thrust generation or by cost of transport. This work uses an unsteady boundary-element method to numerically investigate the hydrodynamics and propulsive efficiency of high-Reynolds-number swimmers whose gaits are encoded by Fourier series or by Jacobi elliptic functions. Numerical results are presented with an emphasis on identifying particular wake structures and modes of motion that are associated with optimal swimming. This work was supported by the Office of Naval Research through MURI Grant N00014-14-1-0533.

  16. Introduction to Magneto-Hydrodynamics

    Science.gov (United States)

    Pelletier, Guy

    Magneto-Hydrodynamics (hereafter MHD) describes plasmas on large scales and more generally electrically conducting fluids. This description does not discriminate between the various fluids that constitute the medium. In laboratory, it allows to globally describe a plasma machine, for instance a toroidal nuclear fusion reactor like a Tokamak. In astrophysics it plays an essential role in the description of cosmic objects and their environments, as well as the media, such as the interstellar or the intergalactic medium. A set of phenomena are specific to MHD description. Some of them will be presented in this lecture such as the tension effect, confinement, magnetic diffusivity, magnetic field freezing, Alfvén waves, magneto-sonic waves, reconnection. A celebrated phenomenon of MHD will not be introduced in this brief lecture, namely the dynamo effect.

  17. Hydrodynamic size distribution of gold nanoparticles controlled by repetition rate during pulsed laser ablation in water

    Science.gov (United States)

    Menéndez-Manjón, Ana; Barcikowski, Stephan

    2011-02-01

    Most investigations on the laser generation and fragmentation of nanoparticles focus on Feret particle size, although the hydrodynamic size of nanoparticles is of great importance, for example in biotechnology for diffusion in living cells, or in engineering, for a tuned rheology of suspensions. In this sense, the formation and fragmentation of gold colloidal nanoparticles using femtosecond laser ablation at variable pulse repetition rates (100-5000 Hz) in deionized water were investigated through their plasmon resonance and hydrodynamic diameter, measured by Dynamic Light Scattering. The increment of the repetition rate does not influence the ablation efficiency, but produces a decrease of the hydrodynamic diameter and blue-shift of the plasmon resonance of the generated gold nanoparticles. Fragmentation, induced by inter-pulse irradiation of the colloids was measured online, showing to be more effective low repetition rates. The pulse repetition rate is shown to be an appropriate laser parameter for hydrodynamic size control of nanoparticles without further influence on the production efficiency.

  18. The hydrodynamics of dolphin drafting

    Directory of Open Access Journals (Sweden)

    Weihs Daniel

    2004-05-01

    Full Text Available Abstract Background Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Results Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in front to move forwards and radially outwards, and water behind the body to move forwards to replace the animal's mass. Thus, the calf can gain a 'free ride' in the forward-moving areas. Utilizing these effects, the neonate can gain up to 90% of the thrust needed to move alongside the mother at speeds of up to 2.4 m/sec. A comparison with observations of eastern spinner dolphins (Stenella longirostris is presented, showing savings of up to 60% in the thrust that calves require if they are to keep up with their mothers. Conclusions A theoretical analysis, backed by observations of free-swimming dolphin schools, indicates that hydrodynamic interactions with mothers play an important role in enabling dolphin calves to keep up with rapidly moving adult school members.

  19. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    Science.gov (United States)

    Caldwell, C. E.; McCarthy, I. G.; Baldry, I. K.; Collins, C. A.; Schaye, J.; Bird, S.

    2016-11-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary cosmic microwave background (CMB) data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g. X-ray luminosity, Sunyaev-Zel'dovich flux, and optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar Λ cold dark matter models. These predictions can be compared with the results from existing redshift surveys such as the highly complete Galaxy And Mass Assembly survey, and upcoming wide-field spectroscopic surveys such as the Wide Area Vista Extragalactic Survey and the Dark Energy Survey Instrument.

  20. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil;

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set the ac...

  1. Hydrodynamic characterization of fluid bed cokers

    Energy Technology Data Exchange (ETDEWEB)

    Knapper, B. [Saskatchewan Univ., Saskatoon, SK (Canada); Berruti, F. [Western Ontario Univ., London, ON (Canada); Grace, J.R.; Bi, H.T.; Lim, C.J. [British Columbia Univ., Vancouver, BC (Canada)

    2002-07-01

    Syncrude Canada Ltd. uses fluid bed cokers for thermal conversion of bitumen from Northern Alberta tar sands into distillates. This paper presents the results of a study that examined the hydrodynamic characteristics of a geometrically and dynamically scaled-down cold flow model of an industrial fluid bed coker. The cold flow model was constructed with Plexiglass with a semi-circular geometry to enable flow visualization of the solid particles. Several operating conditions were examined and measured for key characteristic parameters. Local void fractions were measured with an optical fibre probe, and a suction probe was used to determine the local solids mass fluxes at varying radial and axial locations of the fluidized bed. It was determined that there are large axial and radial variations in both the local voidage and solids mass flux in terms of gas-solids flow. The core-annulus model for dilute riser flow gives unsatisfactory predictions because the model is not able to forecast radial variations in the annular region. A modified core-annulus flow model was developed to address this problem. The modified model has continuous profiles for the gas velocity and solids flux to significantly improve predictions.16 refs., 1 tab., 3 figs.

  2. Hydrodynamic interaction between particles near elastic interfaces

    CERN Document Server

    Daddi-Moussa-Ider, Abdallah

    2016-01-01

    We present an analytical calculation of the hydrodynamic interaction between two spherical particles near an elastic interface such as a cell membrane. The theory predicts the frequency dependent self- and pair-mobilities accounting for the finite particle size up to the 5th order in the ratio between particle diameter and wall distance as well as between diameter and interparticle distance. We find that particle motion towards a membrane with pure bending resistance always leads to mutual repulsion similar as in the well-known case of a hard-wall. In the vicinity of a membrane with shearing resistance, however, we observe an attractive interaction in a certain parameter range which is in contrast to the behavior near a hard wall. This attraction might facilitate surface chemical reactions. Furthermore, we show that there exists a frequency range in which the pair-mobility for perpendicular motion exceeds its bulk value, leading to short-lived superdiffusive behavior. Using the analytical particle mobilities ...

  3. Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets

    CERN Document Server

    Langton, Jonathan

    2007-01-01

    We employ a two-dimensional grid-based hydrodynamic model to simulate upper atmospheric dynamics on extrasolar giant planets. Our model is well-suited to simulate the dynamics of the atmospheres of planets with high orbital eccentricity that are subject to widely-varying irradiation conditions. We identify six such planets, with eccentricities between $e=0.28$ and $e=0.93$ and semimajor axes ranging from $a=0.0508$ A.U. to $a=0.432$ A.U., as particularly interesting objects for study. For each of these planets, we determine the temperature profile and resulting infrared light curves in the 8-$\\mu$m Spitzer bands. Especially notable are the results for HD 80606b, which has the largest eccentricity ($e=0.9321$) of any known planet, and HAT-P-2b, which transits its parent star, so that its physical properties are well-constrained. Despite the variety of orbital parameters, the atmospheric dynamics of these eccentric planets display a number of interesting common properties. In all cases, the atmospheric response...

  4. DBI scalar field theory for QGP hydrodynamics

    Science.gov (United States)

    Nastase, Horatiu

    2016-07-01

    A way to describe the hydrodynamics of the quark-gluon plasma using a Dirac-Born-Infeld (DBI) action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal (η ≃0 ) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well as a bulk viscosity, and regulates the behavior of the energy density at the shock, making it finite. The resulting fluid satisfies the relativistic Navier-Stokes equation with uμ,ρ ,P ,η defined in terms of ϕ and its derivatives. One finds a relation between the parameters of the theory and the quark-gluon plasma thermodynamics, α /β2=η /(s T ), and by fixing α and β from usual (low multiplicity) particle scattering, one finds T ∝mπ.

  5. Hydrodynamics of marine and offshore structures

    Institute of Scientific and Technical Information of China (English)

    FALTINSEN O. M

    2014-01-01

    An overview of hydrodynamic problems related to the broad variety of ships and sea structures involved in transportation, oil and gas exploration and production, marine operations, recovery of oil-spill, renewable energy, infrastructure and aquaculture is given. An approximate hydroelastic model for wave and current induced response of a floating fish farm with circular plastic collar and net cage is discussed. Weakly nonlinear potential-flow problems such as slow-drift motions and stationkeeping, springing of ships and ringing are given special attention. Body-fixed coordinate system is recommended in weakly nonlinear potential-flow ana-lysis of bodies with sharp corners. Dynamic ship instabilities, Mathieu-type instabilities, chaos and two-phase flow involving inter-face instabilities are discussed. It is advocated that slamming must be coupled with structural mechanics in order to find important time scales of the many physical effects associated with slamming and that both water entry and exit matter in describing the global wetdeck slamming effects. Further, sloshing-induced slamming in prismatic LNG tanks is perhaps the most complicated slamming problem because many fluid mechanic and thermodynamic parameters as well as hydroelasticity may matter.

  6. A comparison of cosmological hydrodynamic codes

    Science.gov (United States)

    Kang, Hyesung; Ostriker, Jeremiah P.; Cen, Renyue; Ryu, Dongsu; Hernquist, Lars; Evrard, August E.; Bryan, Greg L.; Norman, Michael L.

    1994-01-01

    We present a detailed comparison of the simulation results of various hydrodynamic codes. Starting with identical initial conditions based on the cold dark matter scenario for the growth of structure, with parameters h = 0.5 Omega = Omega(sub b) = 1, and sigma(sub 8) = 1, we integrate from redshift z = 20 to z = O to determine the physical state within a representative volume of size L(exp 3) where L = 64 h(exp -1) Mpc. Five indenpendent codes are compared: three of them Eulerian mesh-based and two variants of the smooth particle hydrodynamics 'SPH' Lagrangian approach. The Eulerian codes were run at N(exp 3) = (32(exp 3), 64(exp 3), 128(exp 3), and 256(exp 3)) cells, the SPH codes at N(exp 3) = 32(exp 3) and 64(exp 3) particles. Results were then rebinned to a 16(exp 3) grid with the exception that the rebinned data should converge, by all techniques, to a common and correct result as N approaches infinity. We find that global averages of various physical quantities do, as expected, tend to converge in the rebinned model, but that uncertainites in even primitive quantities such as (T), (rho(exp 2))(exp 1/2) persists at the 3%-17% level achieve comparable and satisfactory accuracy for comparable computer time in their treatment of the high-density, high-temeprature regions as measured in the rebinned data; the variance among the five codes (at highest resolution) for the mean temperature (as weighted by rho(exp 2) is only 4.5%. Examined at high resolution we suspect that the density resolution is better in the SPH codes and the thermal accuracy in low-density regions better in the Eulerian codes. In the low-density, low-temperature regions the SPH codes have poor accuracy due to statiscal effects, and the Jameson code gives the temperatures which are too high, due to overuse of artificial viscosity in these high Mach number regions. Overall the comparison allows us to better estimate errors; it points to ways of improving this current generation ofhydrodynamic

  7. Interplay between anisotropy and spatial dispersion in metamaterial waveguide

    CERN Document Server

    Koshelev, Kirill L

    2016-01-01

    We analyze spectrum of waveguide modes of an arbitrary uniaxial anisotropic metamaterial slab with non-local electromagnetic response whose permittivity tensor could be described within Drude approximation. Spatial dispersion was introduced within the hydrodynamical model. Both anisotropy and spatial dispersion were considered as perturbations. This helps to distinguish their effect on the spectrum of the slab and to analyze lifting of the degeneracy of eigenmodes at plasma frequency in detail. Spatial dispersion is shown to result in break of the singularity in the den- sity of optical states in the hyperbolic regime and in suppression of negative dispersion induced by anisotropy. Mutual effect of spatial dispersion and anisotropy can bring light to a complete stop at certain frequencies.

  8. Hydrodynamic profile of young swimmers: changes over a competitive season.

    Science.gov (United States)

    Barbosa, T M; Morais, J E; Marques, M C; Silva, A J; Marinho, D A; Kee, Y H

    2015-04-01

    The aim of this study was to analyze the changes in the hydrodynamic profile of young swimmers over a competitive season and to compare the variations according to a well-designed training periodization. Twenty-five swimmers (13 boys and 12 girls) were evaluated in (a) October (M1); (b) March (M2); and (c) June (M3). Inertial and anthropometrical measures included body mass, swimmer's added water mass, height, and trunk transverse surface area. Swimming efficiency was estimated by the speed fluctuation, stroke index, and approximate entropy. Active drag was estimated with the velocity perturbation method and the passive drag with the gliding decay method. Hydrodynamic dimensionless numbers (Froude and Reynolds numbers) and hull velocity (i.e., speed at Froude number = 0.42) were also calculated. No variable presented a significant gender effect. Anthropometrics and inertial parameters plus dimensionless numbers increased over time. Swimming efficiency improved between M1 and M3. There was a trend for both passive and active drag increase from M1 to M2, but being lower at M3 than at M1. Intra-individual changes between evaluation moments suggest high between- and within-subject variations. Therefore, hydrodynamic changes over a season occur in a non-linear fashion way, where the interplay between growth and training periodization explain the unique path flow selected by each young swimmer. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  9. Modeling the Hydrodynamical Properties of the QGP at RHIC

    Science.gov (United States)

    Garishvili, Irakli; Soltz, Ron; Pratt, Scott; Cheng, Micael; Glenn, Andrew; Newby, Jason; Linden-Levy, Loren; Abelev, Betty

    2010-11-01

    Comparisons of the RHIC data to various theoretical models suggest that the evolution of the QGP, a state of matter believed to be created in early stages of heavy ion collisions at RHIC, is qualitatively well described by hydrodynamics. However, the key properties of the QGP, such as initial temperature, Tinit, and the ratio of shear viscosity to entropy density of matter, η/s, are not precisely known. To constrain these properties we have developed a multi-stage hydrodynamics/hadron cascade model of heavy ion collisions which incorporates Glauber initial state conditions, pre-equilibrium flow, the UVH2+1 viscous hydro model, Cooper-Frye freezeout, and the UrQMD hadronic cascade model. To test the sensitivity of the observables to the equation of state (EoS), we use several different EoS in the hydrodynamic evolution, including those derived from the hadron resonance gas model and lattice QCD. This framework has an ability to predict key QGP observables, such as, elliptic flow, spectra, and HBT radii for various particle species. For each set of model's input parameters (Tinit, η/s and initial flow) we perform a simultaneous comparison to spectra, elliptic flow, and HBT measured at RHIC. Based on this analysis the determinations of Tinit and η/s will be presented.

  10. Calibrating an updated smoothed particle hydrodynamics scheme within gcd+

    Science.gov (United States)

    Kawata, D.; Okamoto, T.; Gibson, B. K.; Barnes, D. J.; Cen, R.

    2013-01-01

    We adapt a modern scheme of smoothed particle hydrodynamics (SPH) to our tree N-body/SPH galactic chemodynamics code gcd+. The applied scheme includes implementations of the artificial viscosity switch and artificial thermal conductivity proposed by Morris & Monaghan, Rosswog & Price and Price to model discontinuities and Kelvin-Helmholtz instabilities more accurately. We first present hydrodynamics test simulations and contrast the results to runs undertaken without artificial viscosity switch or thermal conduction. In addition, we also explore the different levels of smoothing by adopting larger or smaller smoothing lengths, i.e. a larger or smaller number of neighbour particles, Nnb. We demonstrate that the new version of gcd+ is capable of modelling Kelvin-Helmholtz instabilities to a similar level as the mesh code, athena. From the Gresho vortex, point-like explosion and self-similar collapse tests, we conclude that setting the smoothing length to keep Nnb as high as ˜58 is preferable to adopting smaller smoothing lengths. We present our optimized parameter sets from the hydrodynamics tests.

  11. A Displayer of Stellar Hydrodynamics Processes

    Science.gov (United States)

    Vigo, José Antonio Escartín; Senz, Domingo García

    The graphics display tool that we present here was originally developed to meet the needs of the Astronomy and Astrophysics group at the UPC (GAA). At present, it is used to display the plots obtained from hydrodynamic simulations using the SPH (smoothed particle hydrodynamics) method. It is, however, a generic program that can be used for other multidimensional hydrodynamic methods. The application combines the most widely used features of other programs (most of them commercial) such as GnuPlot, Surfer, Grapher, IDL, Voxler, etc.

  12. Non abelian hydrodynamics and heavy ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Calzetta, E. [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, Buenos Aires 1428 (Argentina)

    2014-01-14

    The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.

  13. Quantum ideal hydrodynamics on the lattice

    CERN Document Server

    Burch, Tommy

    2013-01-01

    After discussing the problem of defining the hydrodynamic limit from microscopic scales, we give an introduction to ideal hydrodynamics in the Lagrange picture, and show that it can be viewed as a field theory, which can be quantized using the usual Feynman sum-over-paths prescription. We then argue that this picture can be connected to the usually neglected thermal microscopic scale in the hydrodynamic expansion. After showing that this expansion is generally non-perturbative, we show how the lattice can be used to understand the impact quantum and thermal fluctuations can have on the fluid behavior.

  14. Non abelian hydrodynamics and heavy ion collisions

    CERN Document Server

    Calzetta, Esteban

    2013-01-01

    The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.

  15. Hydrodynamic and longitudinal impedance analysis of cerebrospinal fluid dynamics at the craniovertebral junction in type I Chiari malformation.

    Directory of Open Access Journals (Sweden)

    Bryn A Martin

    Full Text Available Elevated or reduced velocity of cerebrospinal fluid (CSF at the craniovertebral junction (CVJ has been associated with type I Chiari malformation (CMI. Thus, quantification of hydrodynamic parameters that describe the CSF dynamics could help assess disease severity and surgical outcome. In this study, we describe the methodology to quantify CSF hydrodynamic parameters near the CVJ and upper cervical spine utilizing subject-specific computational fluid dynamics (CFD simulations based on in vivo MRI measurements of flow and geometry. Hydrodynamic parameters were computed for a healthy subject and two CMI patients both pre- and post-decompression surgery to determine the differences between cases. For the first time, we present the methods to quantify longitudinal impedance (LI to CSF motion, a subject-specific hydrodynamic parameter that may have value to help quantify the CSF flow blockage severity in CMI. In addition, the following hydrodynamic parameters were quantified for each case: maximum velocity in systole and diastole, Reynolds and Womersley number, and peak pressure drop during the CSF cardiac flow cycle. The following geometric parameters were quantified: cross-sectional area and hydraulic diameter of the spinal subarachnoid space (SAS. The mean values of the geometric parameters increased post-surgically for the CMI models, but remained smaller than the healthy volunteer. All hydrodynamic parameters, except pressure drop, decreased post-surgically for the CMI patients, but remained greater than in the healthy case. Peak pressure drop alterations were mixed. To our knowledge this study represents the first subject-specific CFD simulation of CMI decompression surgery and quantification of LI in the CSF space. Further study in a larger patient and control group is needed to determine if the presented geometric and/or hydrodynamic parameters are helpful for surgical planning.

  16. Biomimetic shark skin: design, fabrication and hydrodynamic function.

    Science.gov (United States)

    Wen, Li; Weaver, James C; Lauder, George V

    2014-05-15

    Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species.

  17. Classical analogue of an interstellar travel through a hydrodynamic wormhole

    Science.gov (United States)

    Euvé, L.-P.; Rousseaux, G.

    2017-09-01

    The classical theory of space-time, namely general relativity, suggests but does not demonstrate the existence of so-called wormholes allowing for interstellar journeys. Alternative proposals such as quantum gravity theories are developed nowadays to allow for wormhole travels by assuming hypothetical trans-Planckian effects at tiny scales. Here we show experimentally that analogue traversable and bidirectional wormholes exist in hydrodynamics following a suggestion by Wheeler. Using a water channel, we sent free surface waves on a countercurrent in an analogue gravity setup aiming at showing that hydrodynamic wormhole travels are controlled by a cascade of dispersive scales including surface tension effects: the capillary wavelength plays the role of a Planckian scale below which long gravity waves are transformed into short capillary waves that are able to move at speeds higher than the "flow" of space-time. Whereas our results do not apply to putative astrophysical wormholes per se, we anticipate that they will trigger new ideas to explore quantum gravity physics.

  18. Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

    Energy Technology Data Exchange (ETDEWEB)

    Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

    2003-07-01

    This document gathers the abstracts of the Euromech 421 colloquium about strongly coupled dispersed two-phase flows. Behaviors specifically due to the two-phase character of the flow have been categorized as: suspensions, particle-induced agitation, microstructure and screening mechanisms; hydrodynamic interactions, dispersion and phase distribution; turbulence modulation by particles, droplets or bubbles in dense systems; collective effects in dispersed two-phase flows, clustering and phase distribution; large-scale instabilities and gravity driven dispersed flows; strongly coupled two-phase flows involving reacting flows or phase change. Topic l: suspensions particle-induced agitation microstructure and screening mechanisms hydrodynamic interactions between two very close spheres; normal stresses in sheared suspensions; a critical look at the rheological experiments of R.A. Bagnold; non-equilibrium particle configuration in sedimentation; unsteady screening of the long-range hydrodynamic interactions of settling particles; computer simulations of hydrodynamic interactions among a large collection of sedimenting poly-disperse particles; velocity fluctuations in a dilute suspension of rigid spheres sedimenting between vertical plates: the role of boundaries; screening and induced-agitation in dilute uniform bubbly flows at small and moderate particle Reynolds numbers: some experimental results. Topic 2: hydrodynamic interactions, dispersion and phase distribution: hydrodynamic interactions in a bubble array; A 'NMR scattering technique' for the determination of the structure in a dispersion of non-brownian settling particles; segregation and clustering during thermo-capillary migration of bubbles; kinetic modelling of bubbly flows; velocity fluctuations in a homogeneous dilute dispersion of high-Reynolds-number rising bubbles; an attempt to simulate screening effects at moderate particle Reynolds numbers using an hybrid formulation; modelling the two

  19. Smoothed particle hydrodynamics and magnetohydrodynamics

    Science.gov (United States)

    Price, Daniel J.

    2012-02-01

    This paper presents an overview and introduction to smoothed particle hydrodynamics and magnetohydrodynamics in theory and in practice. Firstly, we give a basic grounding in the fundamentals of SPH, showing how the equations of motion and energy can be self-consistently derived from the density estimate. We then show how to interpret these equations using the basic SPH interpolation formulae and highlight the subtle difference in approach between SPH and other particle methods. In doing so, we also critique several 'urban myths' regarding SPH, in particular the idea that one can simply increase the 'neighbour number' more slowly than the total number of particles in order to obtain convergence. We also discuss the origin of numerical instabilities such as the pairing and tensile instabilities. Finally, we give practical advice on how to resolve three of the main issues with SPMHD: removing the tensile instability, formulating dissipative terms for MHD shocks and enforcing the divergence constraint on the particles, and we give the current status of developments in this area. Accompanying the paper is the first public release of the NDSPMHD SPH code, a 1, 2 and 3 dimensional code designed as a testbed for SPH/SPMHD algorithms that can be used to test many of the ideas and used to run all of the numerical examples contained in the paper.

  20. Fluctuating hydrodynamics for ionic liquids

    Science.gov (United States)

    Lazaridis, Konstantinos; Wickham, Logan; Voulgarakis, Nikolaos

    2017-04-01

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau-Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids.

  1. Selection of Dispersivity in Groundwater Risk Assessment

    Institute of Scientific and Technical Information of China (English)

    武晓峰; 唐杰

    2004-01-01

    The Domenico model is used in combination with ASTM E 1739 in a Tier 2 risk assessment of chlorinated organic solvents contaminated groundwater sites to predict potential contaminant concentration in groundwater down-gradient from the point of exposure (POE). A knowledge of the dispersivity parameters is necessary for carrying out this calculation. A constant longitudinal dispersivity of 10 m is often used in analytical and numerical calculation. However, because of the scale effect of dispersion, two other main approaches are currently often used. From the viewpoint of conservative principle in risk assessment, it is necessary to determine which dispersivity data will give a higher predicted concentration, corresponding to a more conservative risk calculation. Generally, it is considered that a smaller dispersivity leads to a higher predicted concentration. This assumption is correct when dispersion is the only natural attenuation factor. However, degradation of commonly encountered chlorinated organic solvents in environment under natural condition has been widely reported. Calculations given in this paper of several representative cases show that a general consideration of the influence of dispersivity on concentration prediction is not always correct when a degradation term is included in the calculation. To give a conservative risk calculation, the scale effect of dispersion is considered. Calculations also show that the dispersivity parameters need to be determined by considering the POE distance from the source, the groundwater velocity, and the degradation rate of the contaminant.

  2. Enhanced decolorization of methyl orange using zero-valent copper nanoparticles under assistance of hydrodynamic cavitation.

    Science.gov (United States)

    Li, Pan; Song, Yuan; Wang, Shuai; Tao, Zheng; Yu, Shuili; Liu, Yanan

    2015-01-01

    The rate of reduction reactions of zero-valent metal nanoparticles is restricted by their agglomeration. Hydrodynamic cavitation was used to overcome the disadvantage in this study. Experiments for decolorization of methyl orange azo dye by zero-valent copper nanoparticles were carried out in aqueous solution with and without hydrodynamic cavitation. The results showed that hydrodynamic cavitation greatly accelerated the decolorization rate of methyl orange. The size of nanoparticles was decreased after hydrodynamic cavitation treatment. The effects of important operating parameters such as discharge pressure, initial solution pH, and copper nanoparticle concentration on the degradation rates were studied. It was observed that there was an optimum discharge pressure to get best decolorization performance. Lower solution pH were favorable for the decolorization. The pseudo-first-order kinetic constant for the degradation of methyl orange increased linearly with the copper dose. UV-vis spectroscopic and Fourier transform infrared (FT-IR) analyses confirmed that many degradation intermediates were formed. The results indicated hydroxyl radicals played a key role in the decolorization process. Therefore, the enhancement of decolorization by hydrodynamic cavitation could due to the deagglomeration of nanoparticles as well as the oxidation by the in situ generated hydroxyl radicals. These findings greatly increase the potential of the Cu(0)/hydrodynamic cavitation technique for use in the field of treatment of wastewater containing hazardous materials.

  3. Hydrodynamically driven colloidal assembly in dip coating.

    Science.gov (United States)

    Colosqui, Carlos E; Morris, Jeffrey F; Stone, Howard A

    2013-05-01

    We study the hydrodynamics of dip coating from a suspension and report a mechanism for colloidal assembly and pattern formation on smooth substrates. Below a critical withdrawal speed where the coating film is thinner than the particle diameter, capillary forces induced by deformation of the free surface prevent the convective transport of single particles through the meniscus beneath the film. Capillary-induced forces are balanced by hydrodynamic drag only after a minimum number of particles assemble within the meniscus. The particle assembly can thus enter the thin film where it moves at nearly the withdrawal speed and rapidly separates from the next assembly. The interplay between hydrodynamic and capillary forces produces periodic and regular structures below a critical ratio Ca(2/3)/sqrt[Bo] particles in suspension. The hydrodynamically driven assembly documented here is consistent with stripe pattern formations observed experimentally in dip coating.

  4. Adiabatic hydrodynamics: The eightfold way to dissipation

    CERN Document Server

    Haehl, Felix M; Rangamani, Mukund

    2015-01-01

    We provide a complete solution to hydrodynamic transport at all orders in the gradient expansion compatible with the second law constraint. The key new ingredient we introduce is the notion of adiabaticity, which allows us to take hydrodynamics off-shell. Adiabatic fluids are such that off-shell dynamics of the fluid compensates for entropy production. The space of adiabatic fluids is quite rich, and admits a decomposition into seven distinct classes. Together with the dissipative class this establishes the eightfold way of hydrodynamic transport. Furthermore, recent results guarantee that dissipative terms beyond leading order in the gradient expansion are agnostic of the second law. While this completes a transport taxonomy, we go on to argue for a new symmetry principle, an Abelian gauge invariance that guarantees adiabaticity in hydrodynamics. We suggest that this symmetry is the macroscopic manifestation of the microscopic KMS invariance. We demonstrate its utility by explicitly constructing effective ac...

  5. Lower bound on the electroweak wall velocity from hydrodynamic instability

    Energy Technology Data Exchange (ETDEWEB)

    Mégevand, Ariel; Membiela, Federico Agustín; Sánchez, Alejandro D. [IFIMAR (CONICET-UNMdP), Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Deán Funes (7600) 3350 Mar del Plata (Argentina)

    2015-03-27

    The subsonic expansion of bubbles in a strongly first-order electroweak phase transition is a convenient scenario for electroweak baryogenesis. For most extensions of the Standard Model, stationary subsonic solutions (i.e., deflagrations) exist for the propagation of phase transition fronts. However, deflagrations are known to be hydrodynamically unstable for wall velocities below a certain critical value. We calculate this critical velocity for several extensions of the Standard Model and compare with an estimation of the wall velocity. In general, we find a region in parameter space which gives stable deflagrations as well as favorable conditions for electroweak baryogenesis.

  6. A Higher Order Godunov Method for Radiation Hydrodynamics: Radiation Subsystem

    CERN Document Server

    Sekora, Michael

    2009-01-01

    A higher order Godunov method for the radiation subsystem of radiation hydrodynamics is presented. A key ingredient of the method is the direct coupling of stiff source term effects to the hyperbolic structure of the system of conservation laws; it is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The method is second order accurate in both time and space, unsplit, asymptotically preserving, and uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Numerical tests demonstrate second order convergence across various parameter regimes.

  7. Emergence of upstream swimming through a hydrodynamic transition

    Science.gov (United States)

    Tung, Chih-kuan; Ardon, Florencia; Roy, Anubhab; Koch, Donald L.; Suarez, Susan S.; Wu, Mingming

    2015-01-01

    We demonstrate that upstream swimming of sperm emerges via an orientation disorder-order transition. The order parameter, the average orientation of the sperm head against the flow, follows a 0.5 power law with the deviation from the critical flow shear rate (γ − γc). This transition is successfully explained by a hydrodynamic bifurcation theory, which extends the sperm upstream swimming to a broad class of near surface micro-swimmers that possess front-back asymmetry and circular motion. PMID:25815969

  8. Hydrodynamics in black brane with hyperscaling violation metric background

    CERN Document Server

    Sadeghi, Jafar

    2014-01-01

    In this paper we consider a metric with hyperscaling violation on black brane background. In this background we calculate the ratio of shear viscosity to entropy density with hydrodynamics information. The calculation of this quantity lead us to constraint $\\theta$ as $3\\leq\\theta<4$, and $\\theta\\leq0$. In that case we show that the quantity of $\\frac{\\eta}{s}$ not dependent to hyperscaling violation parameter $\\theta.$ Our results about ratio of shear viscosity to entropy density in direct of $QCD$ point of view agree with other works in literature as $1/4\\pi$.

  9. Hydrodynamic multibead modeling: problems, pitfalls, and solutions. 2. Proteins.

    Science.gov (United States)

    Zipper, Peter; Durchschlag, Helmut

    2010-02-01

    Hydrodynamic models of proteins have been generated by recourse to crystallographic data and applying a filling model strategy in order to predict both hydrodynamic and scattering parameters. The design of accurate protein models retaining the majority of the molecule peculiarities requires usage of many beads and consideration of many serious problems. Applying the expertise obtained with ellipsoid models and pilot tests on proteins, we succeeded in constructing precise models for several anhydrous and hydrated proteins of different shape, size, and complexity. The models constructed consist of many beads (up to about 11,000) for the protein constituents (atoms, amino acid residues, groups) and preferentially bound water molecules. While in the case of small proteins, parameter predictions are straightforward, computations for giant proteins necessitate drastic reductions of the number of initially available beads. Among several auxiliary programs, our advanced hydration programs, HYDCRYST and HYDMODEL, and modified versions of García de la Torre's program HYDRO were successfully employed. This allowed the generation of realistic protein models by imaging details of their fine structure and enabled the prediction of reliable molecular parameters including intrinsic viscosities. The appearance of the models and the agreement of molecular properties and distance distribution functions p(r) of unreduced and reduced models can be used for a meticulous inspection of the data obtained.

  10. Thermo--hydrodynamics As a Field Theory

    CERN Document Server

    Jezierski, Jacek

    2011-01-01

    The field theoretical description of thermo-hydrodynamics is given. It is based on the duality between the physical space--time and the "material space-time" which we construct here. The material space appearing in a natural way in the canonical formulation of the hydrodynamics is completed with a material time playing role of the field potential for temperature. Both Lagrangian and Hamiltonian formulations, the canonical structure, Poisson bracket, N\\"other theorem and conservation laws are discussed.

  11. Hydrodynamics of bacterial colonies: Phase diagrams

    Science.gov (United States)

    Lega, J.; Passot, T.

    2004-09-01

    We present numerical simulations of a recent hydrodynamic model describing the growth of bacterial colonies on agar plates. We show that this model is able to qualitatively reproduce experimentally observed phase diagrams, which relate a colony shape to the initial quantity of nutrients on the plate and the initial wetness of the agar. We also discuss the principal features resulting from the interplay between hydrodynamic motions and colony growth, as described by our model.

  12. Improvements to SOIL: An Eulerian hydrodynamics code

    Energy Technology Data Exchange (ETDEWEB)

    Davis, C.G.

    1988-04-01

    Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs.

  13. Relabeling symmetries in hydrodynamics and magnetohydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Padhye, N.; Morrison, P.J.

    1996-04-01

    Lagrangian symmetries and concomitant generalized Bianchi identities associated with the relabeling of fluid elements are found for hydrodynamics and magnetohydrodynamics (MHD). In hydrodynamics relabeling results in Ertel`s theorem of conservation of potential vorticity, while in MHD it yields the conservation of cross helicity. The symmetries of the reduction from Lagrangian (material) to Eulerian variables are used to construct the Casimir invariants of the Hamiltonian formalism.

  14. Hydrodynamic Forces on Macromolecules Protruding from Lipid Bilayers Due to External Liquid Flows.

    Science.gov (United States)

    Jönsson, Peter; Jönsson, Bengt

    2015-11-24

    It has previously been observed that an externally applied hydrodynamic shear flow above a fluid lipid bilayer can change the local concentration of macromolecules that are associated with the lipid bilayer. The external liquid flow results in a hydrodynamic force on molecules protruding from the lipid bilayer, causing them to move in the direction of the flow. However, there has been no quantitative study about the magnitude of these forces. We here use finite element simulations to investigate how the magnitude of the external hydrodynamic forces varies with the size and shape of the studied macromolecule. The simulations show that the hydrodynamic force is proportional to the effective hydrodynamic area of the studied molecule, Ahydro, multiplied by the mean hydrodynamic shear stress acting on the membrane surface, σhydro. The parameter Ahydro depends on the size and shape of the studied macromolecule above the lipid bilayer and scales with the cross-sectional area of the molecule. We also investigate how hydrodynamic shielding from other surrounding macromolecules decreases Ahydro when the surface coverage of the shielding macromolecules increases. Experiments where the protein streptavidin is anchored to a supported lipid bilayer on the floor of a microfluidic channel were finally performed at three different surface concentrations, Φ = 1%, 6%, and 10%, where the protein is being moved relative to the lipid bilayer by a liquid flow through the channel. From photobleaching measurements of fluorescently labeled streptavidin we found the experimental drift data to be within good accuracy of the simulated results, less than 12% difference, indicating the validity of the results obtained from the simulations. In addition to giving a deeper insight into how a liquid flow can affect membrane-associated molecules in a lipid bilayer, we also see an interesting potential of using hydrodynamic flow experiments together with the obtained results to study the size and

  15. Observation of Dispersive Shock Waves, Solitons, and Their Interactions in Viscous Fluid Conduits.

    Science.gov (United States)

    Maiden, Michelle D; Lowman, Nicholas K; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-04-29

    Dispersive shock waves and solitons are fundamental nonlinear excitations in dispersive media, but dispersive shock wave studies to date have been severely constrained. Here, we report on a novel dispersive hydrodynamic test bed: the effectively frictionless dynamics of interfacial waves between two high viscosity contrast, miscible, low Reynolds number Stokes fluids. This scenario is realized by injecting from below a lighter, viscous fluid into a column filled with high viscosity fluid. The injected fluid forms a deformable pipe whose diameter is proportional to the injection rate, enabling precise control over the generation of symmetric interfacial waves. Buoyancy drives nonlinear interfacial self-steepening, while normal stresses give rise to the dispersion of interfacial waves. Extremely slow mass diffusion and mass conservation imply that the interfacial waves are effectively dissipationless. This enables high fidelity observations of large amplitude dispersive shock waves in this spatially extended system, found to agree quantitatively with a nonlinear wave averaging theory. Furthermore, several highly coherent phenomena are investigated including dispersive shock wave backflow, the refraction or absorption of solitons by dispersive shock waves, and the multiphase merging of two dispersive shock waves. The complex, coherent, nonlinear mixing of dispersive shock waves and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  16. Global sensitivity analysis and Bayesian parameter inference for solute transport in porous media colonized by biofilms

    Science.gov (United States)

    Younes, A.; Delay, F.; Fajraoui, N.; Fahs, M.; Mara, T. A.

    2016-08-01

    The concept of dual flowing continuum is a promising approach for modeling solute transport in porous media that includes biofilm phases. The highly dispersed transit time distributions often generated by these media are taken into consideration by simply stipulating that advection-dispersion transport occurs through both the porous and the biofilm phases. Both phases are coupled but assigned with contrasting hydrodynamic properties. However, the dual flowing continuum suffers from intrinsic equifinality in the sense that the outlet solute concentration can be the result of several parameter sets of the two flowing phases. To assess the applicability of the dual flowing continuum, we investigate how the model behaves with respect to its parameters. For the purpose of this study, a Global Sensitivity Analysis (GSA) and a Statistical Calibration (SC) of model parameters are performed for two transport scenarios that differ by the strength of interaction between the flowing phases. The GSA is shown to be a valuable tool to understand how the complex system behaves. The results indicate that the rate of mass transfer between the two phases is a key parameter of the model behavior and influences the identifiability of the other parameters. For weak mass exchanges, the output concentration is mainly controlled by the velocity in the porous medium and by the porosity of both flowing phases. In the case of large mass exchanges, the kinetics of this exchange also controls the output concentration. The SC results show that transport with large mass exchange between the flowing phases is more likely affected by equifinality than transport with weak exchange. The SC also indicates that weakly sensitive parameters, such as the dispersion in each phase, can be accurately identified. Removing them from calibration procedures is not recommended because it might result in biased estimations of the highly sensitive parameters.

  17. Insulin diffusion and self-association characterized by real-time UV imaging and Taylor dispersion analysis

    DEFF Research Database (Denmark)

    Jensen, Sabrine S; Jensen, Henrik; Cornett, Claus

    2014-01-01

    , self-association, and apparent size of insulin were further characterized by Taylor dispersion analysis, size exclusion chromatography, and dynamic light scattering. At low insulin concentrations and pH 3.0, the hydrodynamic radius of insulin was determined by Taylor dispersion analysis to 1.5±0.1nm...

  18. Hydrodynamics of soft active matter

    Science.gov (United States)

    Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi

    2013-07-01

    This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

  19. Simulation of hydrodynamically interacting particles confined by a spherical cavity

    Science.gov (United States)

    Aponte-Rivera, Christian; Zia, Roseanna N.

    2016-06-01

    We present a theoretical framework to model the behavior of a concentrated colloidal dispersion confined inside a spherical cavity. Prior attempts to model such behavior were limited to a single enclosed particle and attempts to enlarge such models to two or more particles have seen limited success owing to the challenges of accurately modeling many-body and singular hydrodynamic interactions. To overcome these difficulties, we have developed a set of hydrodynamic mobility functions that couple particle motion with hydrodynamic traction moments that, when inverted and combined with near-field resistance functions, form a complete coupling tensor that accurately captures both the far-field and near-field physics and is valid for an arbitrary number of spherical particles enclosed by a spherical cavity of arbitrary relative size a /R , where a and R are the particle and cavity size, respectively. This framework is then utilized to study the effect of spherical confinement on the self- and entrained motion of the colloids, for a range of particle-to-cavity size ratios. The self-motion of a finite-size enclosed particle is studied first, recovering prior results published in the literature: The hydrodynamic mobility of the particle is greatest at the center of the cavity and decays as (a /R ) /(1 -y2) , where y is the particle distance to the cavity center. Near the cavity wall, the no-slip surfaces couple strongly and mobility along the cavity radius vanishes as ξ ≡R -(a +y ) , where y is center-to-center distance from particle to cavity. Corresponding motion transverse to the cavity radius vanishes as [ln(1/ξ ) ] -1. The effect of confinement on entrainment of a particle in the flow created by the motion of others is also studied, where we find that confinement exerts a qualitative effect on the strength and anisotropy of entrainment of a passive particle dragged by the flow of a forced particle. As expected, entrainment strength decays with increased distance

  20. Differential Expression of Extracellular Matrix and Growth Factors by Embryoid Bodies in Hydrodynamic and Static Cultures

    Science.gov (United States)

    Fridley, Krista M.; Nair, Rekha

    2014-01-01

    During development, cell fate specification and tissue development are orchestrated by the sequential presentation of soluble growth factors (GF) and extracellular matrix (ECM) molecules. Similarly, differentiation of stem cells in vitro relies upon the temporal presence of extracellular cues within the microenvironment. Hydrodynamic culture systems are not limited by volume restrictions and therefore offer several practical advantages for scalability over static cultures; however, hydrodynamic cultures expose cells to physical parameters not present in static culture, such as fluid shear stress and mass transfer through convective forces. In this study, the differences between static and hydrodynamic culture conditions on the expression of ECM and GF molecules during the differentiation of mouse embryonic stem cells were examined at both the gene and protein level. The expression of ECM and GF genes exhibited an early decrease in static cultures based on heat map and hierarchical clustering analysis and a relative delayed increase in hydrodynamic cultures. Although the temporal patterns of specific ECM and GF protein expression were comparable between static and hydrodynamic cultures, several notable differences in the magnitudes of expression were observed at similar time points. These results describe the establishment of an analytical framework that can be used to examine the expression patterns of ECM and GF molecules expressed by pluripotent stem cells undergoing differentiation as 3D multicellular aggregates under different culture conditions, and suggest that physical parameters of stem cell microenvironments can alter endogenous ECM and GF expression profiles that may, in turn, influence cell fate decisions. PMID:25423310

  1. Hydrodynamic theory for ion structure and stopping power in quantum plasmas.

    Science.gov (United States)

    Shukla, P K; Akbari-Moghanjoughi, M

    2013-04-01

    We present a theory for the dynamical ion structure factor (DISF) and ion stopping power in an unmagnetized collisional quantum plasma with degenerate electron fluids and nondegenerate strongly correlated ion fluids. Our theory is based on the fluctuation dissipation theorem and the quantum plasma dielectric constant that is deduced from a linearized viscoelastic quantum hydrodynamical (LVQHD) model. The latter incorporates the essential physics of quantum forces, which are associated with the quantum statistical pressure, electron-exchange, and electron-correlation effects, the quantum electron recoil effect caused by the dispersion of overlapping electron wave functions that control the dynamics of degenerate electron fluids, and the viscoelastic properties of strongly correlated ion fluids. Both degenerate electrons and nondegenerate strongly correlated ions are coupled with each other via the space charge electric force. Thus, our LVQHD theory is valid for a collisional quantum plasma at atomic scales with a wide range of the ion coupling parameter, the plasma composition, and plasma number densities that are relevant for compressed plasmas in laboratories (inertial confinement fusion schemes) and in astrophysical environments (e.g., warm dense matter and the cores of white dwarf stars). It is found that quantum electron effects and viscoelastic properties of strongly correlated ions significantly affect the features of the DISF and the ion stopping power (ISP). Unlike previous theories, which have studied ion correlations in terms of the ion coupling parameter, by neglecting the essential physics of collective effects that are competing among each other, we have here developed a method to evaluate the dependence of the plasma static and dynamical features in terms of individual parameters, like the Wigner-Seitz radius, the ion atomic number, and the ion temperature. It is found that due to the complex nature of charge screening in quantum plasmas, the ion

  2. Hydrodynamic theory for ion structure and stopping power in quantum plasmas

    Science.gov (United States)

    Shukla, P. K.; Akbari-Moghanjoughi, M.

    2013-04-01

    We present a theory for the dynamical ion structure factor (DISF) and ion stopping power in an unmagnetized collisional quantum plasma with degenerate electron fluids and nondegenerate strongly correlated ion fluids. Our theory is based on the fluctuation dissipation theorem and the quantum plasma dielectric constant that is deduced from a linearized viscoelastic quantum hydrodynamical (LVQHD) model. The latter incorporates the essential physics of quantum forces, which are associated with the quantum statistical pressure, electron-exchange, and electron-correlation effects, the quantum electron recoil effect caused by the dispersion of overlapping electron wave functions that control the dynamics of degenerate electron fluids, and the viscoelastic properties of strongly correlated ion fluids. Both degenerate electrons and nondegenerate strongly correlated ions are coupled with each other via the space charge electric force. Thus, our LVQHD theory is valid for a collisional quantum plasma at atomic scales with a wide range of the ion coupling parameter, the plasma composition, and plasma number densities that are relevant for compressed plasmas in laboratories (inertial confinement fusion schemes) and in astrophysical environments (e.g., warm dense matter and the cores of white dwarf stars). It is found that quantum electron effects and viscoelastic properties of strongly correlated ions significantly affect the features of the DISF and the ion stopping power (ISP). Unlike previous theories, which have studied ion correlations in terms of the ion coupling parameter, by neglecting the essential physics of collective effects that are competing among each other, we have here developed a method to evaluate the dependence of the plasma static and dynamical features in terms of individual parameters, like the Wigner-Seitz radius, the ion atomic number, and the ion temperature. It is found that due to the complex nature of charge screening in quantum plasmas, the ion

  3. A Comparison Between Measured and Predicted Hydrodynamic Damping for a Jack-Up Rig Model

    DEFF Research Database (Denmark)

    Laursen, Thomas; Rohbock, Lars; Jensen, Jørgen Juncher

    1996-01-01

    methods.In the comparison between the model test results and the theoretical predictions, thehydro-dynamic damping proves to be the most important uncertain parameter. It is shown thata relative large hydrodynamic damping must be assumed in the theoretical calculations in orderto predict the measured...

  4. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  5. Tensor classification of structure in smoothed particle hydrodynamics density fields

    Science.gov (United States)

    Forgan, Duncan; Bonnell, Ian; Lucas, William; Rice, Ken

    2016-04-01

    As hydrodynamic simulations increase in scale and resolution, identifying structures with non-trivial geometries or regions of general interest becomes increasingly challenging. There is a growing need for algorithms that identify a variety of different features in a simulation without requiring a `by eye' search. We present tensor classification as such a technique for smoothed particle hydrodynamics (SPH). These methods have already been used to great effect in N-Body cosmological simulations, which require smoothing defined as an input free parameter. We show that tensor classification successfully identifies a wide range of structures in SPH density fields using its native smoothing, removing a free parameter from the analysis and preventing the need for tessellation of the density field, as required by some classification algorithms. As examples, we show that tensor classification using the tidal tensor and the velocity shear tensor successfully identifies filaments, shells and sheet structures in giant molecular cloud simulations, as well as spiral arms in discs. The relationship between structures identified using different tensors illustrates how different forces compete and co-operate to produce the observed density field. We therefore advocate the use of multiple tensors to classify structure in SPH simulations, to shed light on the interplay of multiple physical processes.

  6. Hydrodynamical Simulations of Colliding Jets: Modeling 3C 75

    Science.gov (United States)

    Molnar, S. M.; Schive, H.-Y.; Birkinshaw, M.; Chiueh, T.; Musoke, G.; Young, A. J.

    2017-01-01

    Radio observations suggest that 3C 75, located in the dumbbell shaped galaxy NGC 1128 at the center of Abell 400, hosts two colliding jets. Motivated by this source, we perform three-dimensional hydrodynamical simulations using a modified version of the GPU-accelerated Adaptive-MEsh-Refinement hydrodynamical parallel code (GAMER) to study colliding extragalactic jets. We find that colliding jets can be cast into two categories: (1) bouncing jets, in which case the jets bounce off each other keeping their identities, and (2) merging jets, when only one jet emerges from the collision. Under some conditions the interaction causes the jets to break up into oscillating filaments of opposite helicity, with consequences for their downstream stability. When one jet is significantly faster than the other and the impact parameter is small, the jets merge; the faster jet takes over the slower one. In the case of merging jets, the oscillations of the filaments, in projection, may show a feature that resembles a double helix, similar to the radio image of 3C 75. Thus we interpret the morphology of 3C 75 as a consequence of the collision of two jets with distinctly different speeds at a small impact parameter, with the faster jet breaking up into two oscillating filaments.

  7. Emergence of multiple synchronization modes in hydrodynamically-coupled cilia

    Science.gov (United States)

    Guo, Hanliang; Kanso, Eva

    2016-11-01

    Motile cilia and flagella exhibit different phase coordinations. For example, closely swimming spermatozoa are observed to synchronize together; bi-flagellates Chlamydomonas regulate the flagella in a "breast-stroke" fashion; cilia on the surface of Paramecium beat in a fixed phase lag in an orchestrated wave like fashion. Experimental evidence suggests that phase coordinations can be achieved solely via hydrodynamical interactions. However, the exact mechanisms behind it remain illusive. Here, adapting a "geometric switch" model, we observe different synchronization modes in pairs of hydrodynamically-coupled cilia by changing physical parameters such as the strength of the cilia internal motor and the separation distance between cilia. Interestingly, we find regions in the parameter space where the coupled cilia reach stable phase coordinations and regions where the phase coordinations are sensitive to perturbations. We also find that leaning into the fluid reduces the sensitivity to perturbations, and produces stable phase coordination that is neither in-phase nor anti-phase, which could explain the origin of metachronal waves in large cilia populations.

  8. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and redu

  9. Numerical simulations of magnetic suspensions with hydrodynamic and dipole-dipole magnetic interactions

    Science.gov (United States)

    Gontijo, R. G.; Cunha, F. R.

    2017-06-01

    volume fraction increased. This work is the first involving a magnetic suspension under the influence of both magnetic and hydrodynamic particle interactions. The mean sedimentation velocity and the suspension magnetization are examined under the steady-state condition over several realizations. Simulation results for the fluid magnetization are compared with a modified mean field theory, and a very good agreement for semi-dilute suspensions is observed. Additionally, the motion and shape transition of an initially spherical blob composed of magnetic spherical particles are investigated by computer simulations. We show the existence of velocity fluctuations due to the interplay of magnetically induced aggregates and their hydrodynamic dispersion. We find that the collective hydrodynamic interactions play a dispersive role opposite to the aggregative contribution of the magnetic dipole-dipole interactions.

  10. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  11. Experimental study on hydrodynamic behaviors of high-speed gas jets in still water

    Institute of Scientific and Technical Information of China (English)

    Zhenqing Dai; Boyi Wang; Longxi Qi; Honghui Shi

    2006-01-01

    The present paper describes experimental investigation on the flow pattern and hydrodynamic effect of underwater gas jets from supersonic and sonic nozzles operated in correct- and imperfect expansion conditions. The flow visualizations show that jetting is the flow regime for the submerged gas injection at a high speed in the parameter range under consideration. The obtained results indicate that high-speed gas jets in still water induce large pressure pulsations upstream of the nozzle exit and the presence of shock-cell structure in the over-and under-expanded jets leads to an increase in the intensity of the jet-induced hydrodynamic pressure.

  12. Integrated methodology for constructing a quantified hydrodynamic model for application to clastic petroleum reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Honarpour, M. M.; Schatzinger, R. A.; Szpakiewicz, M. J.; Jackson, S. R.; Sharma, B.; Tomutsa, L.; Chang, M. M.

    1990-01-01

    A comprehensive, multidisciplinary, stepwise methodology is developed for constructing and integration geological and engineering information for predicting petroleum reservoir performance. This methodology is based on our experience in characterizing shallow marine reservoirs, but it should also apply to other deposystems. The methodology is presented as Part 1 of this report. Three major tasks that must be studied to facilitate a systematic approach for constructing a predictive hydrodynamic model for petroleum reservoirs are addressed: (1) data collection, organization, evaluation, and integration; (2) hydrodynamic model construction and verification; and (3) prediction and ranking of reservoir parameters by numerical simulation using data derived from the model. 39 refs., 62 figs., 13 tabs.

  13. Hydrodynamics of pair-annihilating disclinations in SmC films.

    Science.gov (United States)

    Svensek, D; Zumer, S

    2003-04-18

    The pair annihilation of smectic c-director defects with winding numbers +/-1 in a freestanding SmC film as a representative of the XY model is studied numerically, considering a full coupling of orientational degrees of freedom and hydrodynamics. A reduction of the annihilation time compared to the nonhydrodynamic treatment is observed. It is demonstrated that the +1 disclination moves considerably faster than the -1 one primarily due to hydrodynamic flow, weakly assisted also by elastic anisotropy. The stress tensor terms and material parameters relevant for this effect are identified.

  14. Stochastic-hydrodynamic model of halo formation in charged particle beams

    Directory of Open Access Journals (Sweden)

    Nicola Cufaro Petroni

    2003-03-01

    Full Text Available The formation of the beam halo in charged particle accelerators is studied in the framework of a stochastic-hydrodynamic model for the collective motion of the particle beam. In such a stochastic-hydrodynamic theory the density and the phase of the charged beam obey a set of coupled nonlinear hydrodynamic equations with explicit time-reversal invariance. This leads to a linearized theory that describes the collective dynamics of the beam in terms of a classical Schrödinger equation. Taking into account space-charge effects, we derive a set of coupled nonlinear hydrodynamic equations. These equations define a collective dynamics of self-interacting systems much in the same spirit as in the Gross-Pitaevskii and Landau-Ginzburg theories of the collective dynamics for interacting quantum many-body systems. Self-consistent solutions of the dynamical equations lead to quasistationary beam configurations with enhanced transverse dispersion and transverse emittance growth. In the limit of a frozen space-charge core it is then possible to determine and study the properties of stationary, stable core-plus-halo beam distributions. In this scheme the possible reproduction of the halo after its elimination is a consequence of the stationarity of the transverse distribution which plays the role of an attractor for every other distribution.

  15. Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

    Directory of Open Access Journals (Sweden)

    Parmeshwar L. Shrestha

    2014-02-01

    Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.

  16. Phenomenological predictions of 3+1d anisotropic hydrodynamics

    CERN Document Server

    Nopoush, Mohammad; Ryblewski, Radoslaw

    2016-01-01

    We make phenomenological predictions for particle spectra and elliptic flow in heavy-ion collisions using 3+1d anisotropic hydrodynamics (aHydro) including the effects of both shear and bulk viscosities. The dynamical equations necessary are derived by taking moments of the Boltzmann equation allowing for three distinct (diagonal) momentum-space anisotropy parameters. The formulation is based on relaxation-time approximation for the collisional kernel and a lattice-QCD-based equation of state. Evolving the system to late times, we calculate particle production using THERMINATOR 2, modified to account for an ellipsoidal distribution function. We obtain particle spectra for different particle species such as pions, kaons, and protons, and elliptic flow $v_2$ as a function of centrality, transverse momentum, and rapidity. In our model, we have four free parameters, i.e. freeze-out temperature, initial central energy density, initial momentum-space anisotropies, and shear viscosity to entropy density ratio. Using...

  17. Taylor dispersion analysis of mixtures.

    Science.gov (United States)

    Cottet, Hervé; Biron, Jean-Philippe; Martin, Michel

    2007-12-01

    Taylor dispersion analysis (TDA) is a fast and simple method for determining hydrodynamic radii. In the case of sample mixtures, TDA, as the other nonseparative methods, leads to an average diffusion coefficient on the different molecules constituting the mixture. We set in this work the equations giving, on a consistent basis, the average values obtained by TDA with detectors with linear response functions. These equations confronted TDA experiments of sample mixtures containing different proportions of a small molecule and a polymer standard. Very good agreement between theory and experiment was obtained. In a second part of this work, on the basis of monomodal or bimodal molar mass distributions of polymers, the different average diffusion coefficients corresponding to TDA were compared to the z-average diffusion coefficient (D(z)) obtained from dynamic light scattering (DLS) experiments and to the weight average diffusion coefficient (D(w)). This latter value is sometimes considered as the most representative of the sample mixture. From these results, it appears that, for monomodal distribution and relatively low polydispersity (I = 1.15), the average diffusion coefficient generally derived from TDA is very close to Dw. However, for highly polydisperse samples (e.g., bimodal polydisperse distributions), important differences could be obtained (up to 35% between TDA and D(w)). In all the cases, the average diffusion coefficient obtained by TDA for a mass concentration detector was closer to the Dw value than the z-average obtained by DLS.

  18. Status and future of hydrodynamical model atmospheres

    CERN Document Server

    Ludwig, H G

    2004-01-01

    Since about 25 years ago work has been dedicated to the development of hydrodynamical model atmospheres for cool stars (of A to T spectral type). Despite their obviously sounder physical foundation in comparison with standard hydrostatic models, their general application has been rather limited. In order to understand why this is, and how to progress, we review the present status of hydrodynamical modelling of cool star atmospheres. The development efforts were and are motivated by the theoretical interest of understanding the dynamical processes operating in stellar atmospheres. To show the observational impact, we discuss examples in the fields of spectroscopy and stellar structure where hydrodynamical modelling provided results on a level qualitatively beyond standard models. We stress present modelling challenges, and highlight presently possible and future observations that would be particularly valuable in the interplay between model validation and interpretation of observables, to eventually widen the ...

  19. Hydrodynamics of a unitary Bose gas

    Science.gov (United States)

    Man, Jay; Fletcher, Richard; Lopes, Raphael; Navon, Nir; Smith, Rob; Hadzibabic, Zoran

    2016-05-01

    In general, normal-phase Bose gases are well described by modelling them as ideal gases. In particular, hydrodynamic flow is usually not observed in the expansion dynamics of normal gases, and is more readily observable in Bose-condensed gases. However, by preparing strongly-interacting clouds, we observe hydrodynamic behaviour in normal-phase Bose gases, including the `maximally' hydrodynamic unitary regime. We avoid the atom losses that often hamper experimental access of this regime by using radio-frequency injection, which switches on interactions much faster than trap or loss timescales. At low phase-space densities, we find excellent agreement with a collisional model based on the Boltzmann equation. At higher phase-space densities our results show a deviation from this model in the vicinity of an Efimov resonance, which cannot be accounted for by measured losses.

  20. Hydrodynamics of the Chiral Dirac Spectrum

    CERN Document Server

    Liu, Yizhuang; Zahed, Ismail

    2016-01-01

    We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.

  1. Hydrodynamics of bacterial colonies: A model

    Science.gov (United States)

    Lega, J.; Passot, T.

    2003-03-01

    We propose a hydrodynamic model for the evolution of bacterial colonies growing on soft agar plates. This model consists of reaction-diffusion equations for the concentrations of nutrients, water, and bacteria, coupled to a single hydrodynamic equation for the velocity field of the bacteria-water mixture. It captures the dynamics inside the colony as well as on its boundary and allows us to identify a mechanism for collective motion towards fresh nutrients, which, in its modeling aspects, is similar to classical chemotaxis. As shown in numerical simulations, our model reproduces both usual colony shapes and typical hydrodynamic motions, such as the whirls and jets recently observed in wet colonies of Bacillus subtilis. The approach presented here could be extended to different experimental situations and provides a general framework for the use of advection-reaction-diffusion equations in modeling bacterial colonies.

  2. Dynamo efficiency controlled by hydrodynamic bistability.

    Science.gov (United States)

    Miralles, Sophie; Herault, Johann; Herault, Johann; Fauve, Stephan; Gissinger, Christophe; Pétrélis, François; Daviaud, François; Dubrulle, Bérengère; Boisson, Jean; Bourgoin, Mickaël; Verhille, Gautier; Odier, Philippe; Pinton, Jean-François; Plihon, Nicolas

    2014-06-01

    Hydrodynamic and magnetic behaviors in a modified experimental setup of the von Kármán sodium flow-where one disk has been replaced by a propeller-are investigated. When the rotation frequencies of the disk and the propeller are different, we show that the fully turbulent hydrodynamic flow undergoes a global bifurcation between two configurations. The bistability of these flow configurations is associated with the dynamics of the central shear layer. The bistable flows are shown to have different dynamo efficiencies; thus for a given rotation rate of the soft-iron disk, two distinct magnetic behaviors are observed depending on the flow configuration. The hydrodynamic transition controls the magnetic field behavior, and bifurcations between high and low magnetic field branches are investigated.

  3. Holography, Hydrodynamization and Heavy-Ion Collisions

    CERN Document Server

    Heller, Michal P

    2016-01-01

    In the course of the past several years holography has emerged as an ab initio tool in exploring strongly-time-dependent phenomena in gauge theories. These lecture notes overview recent developments in this area driven by phenomenological questions concerning applicability of hydrodynamics under extreme conditions occurring in ultrarelativistic heavy-ion collisions at RHIC and LHC. The topics include equilibration time scales, holographic collisions and hydrodynamization from the point of view of the asymptotic character of the hydrodynamic gradient expansion. The emphasis is put on concepts rather than calculational techniques and particular attention is devoted to present these developments in the context of the most recent advances and some of the open problems.

  4. The RAGE radiation-hydrodynamic code

    CERN Document Server

    Gittings, Michael; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W Rob; Ranta, Dale; Stefan, Ryan

    2008-01-01

    We describe RAGE, the ``Radiation Adaptive Grid Eulerian'' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm.

  5. Hydrodynamic simulations with the Godunov SPH

    CERN Document Server

    Murante, Giuseppe; Brunino, Riccardo; Cha, Suneg-Hoon

    2011-01-01

    We present results based on an implementation of the Godunov Smoothed Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical implementation of these equations are (a) the appearance of fluid velocity and pressure obtained from the solution of the Riemann problem between each pair of particles, and (b the absence of an artificial viscosity term. We carry out three different controlled hydrodynamical three-dimensional tests, namely the Sod shock tube, the development of Kelvin-Helmholtz instabilities in a shear flow test, and the "blob" test describing the evolution of a cold cloud moving against a hot wind. The results of our tests confirm and extend in a number of aspects those recently obtained by Cha (2010): (i) GSPH provi...

  6. Radiation hydrodynamics integrated in the PLUTO code

    Science.gov (United States)

    Kolb, Stefan M.; Stute, Matthias; Kley, Wilhelm; Mignone, Andrea

    2013-11-01

    Aims: The transport of energy through radiation is very important in many astrophysical phenomena. In dynamical problems the time-dependent equations of radiation hydrodynamics have to be solved. We present a newly developed radiation-hydrodynamics module specifically designed for the versatile magnetohydrodynamic (MHD) code PLUTO. Methods: The solver is based on the flux-limited diffusion approximation in the two-temperature approach. All equations are solved in the co-moving frame in the frequency-independent (gray) approximation. The hydrodynamics is solved by the different Godunov schemes implemented in PLUTO, and for the radiation transport we use a fully implicit scheme. The resulting system of linear equations is solved either using the successive over-relaxation (SOR) method (for testing purposes) or using matrix solvers that are available in the PETSc library. We state in detail the methodology and describe several test cases to verify the correctness of our implementation. The solver works in standard coordinate systems, such as Cartesian, cylindrical, and spherical, and also for non-equidistant grids. Results: We present a new radiation-hydrodynamics solver coupled to the MHD-code PLUTO that is a modern, versatile, and efficient new module for treating complex radiation hydrodynamical problems in astrophysics. As test cases, either purely radiative situations, or full radiation-hydrodynamical setups (including radiative shocks and convection in accretion disks) were successfully studied. The new module scales very well on parallel computers using MPI. For problems in star or planet formation, we added the possibility of irradiation by a central source.

  7. A hydrodynamic approach to the study of anisotropic instabilities in dissipative relativistic plasmas

    Science.gov (United States)

    Calzetta, Esteban; Kandus, Alejandra

    2016-12-01

    We develop a purely hydrodynamic formalism to describe collisional, anisotropic instabilities in a relativistic plasma, that are usually described with kinetic theory tools. Our main motivation is the fact that coarse-grained models of high particle number systems give more clear and comprehensive physical descriptions of those systems than purely kinetic approaches, and can be more easily tested experimentally as well as numerically. Also they make it easier to follow perturbations from linear to nonlinear regimes. In particular, we aim at developing a theory that describes both a background nonequilibrium fluid configurations and its perturbations, to be able to account for the backreaction of the latter on the former. Our system of equations includes the usual conservation laws for the energy-momentum tensor and for the electric current, and the equations for two new tensors that encode the information about dissipation. To make contact with kinetic theory, we write the different tensors as the moments of a nonequilibrium one-particle distribution function (1pdf) which, for illustrative purposes, we take in the form of a Grad-like ansatz. Although this choice limits the applicability of the formalism to states not far from equilibrium, it retains the main features of the underlying kinetic theory. We assume the validity of the Vlasov-Boltzmann equation, with a collision integral given by the Anderson-Witting prescription, which is more suitable for highly relativistic systems than Marle’s (or Bhatnagar, Gross and Krook) form, and derive the conservation laws by taking its corresponding moments. We apply our developments to study the emergence of instabilities in an anisotropic, but axially symmetric background. For small departures of isotropy we find the dispersion relation for normal modes, which admit unstable solutions for a wide range of values of the parameter space.

  8. Bounce-free Spherical Hydrodynamic Implosion

    CERN Document Server

    Kagan, Grigory; Hsu, Scott C; Awe, Thomas J

    2011-01-01

    In a bounce-free spherical hydrodynamic implosion, the post-stagnation hot core plasma does not expand against the imploding flow. Such an implosion scheme has the advantage of improving the dwell time of the burning fuel, resulting in a higher fusion burn-up fraction. The existence of bounce-free spherical implosions is demonstrated by explicitly constructing a family of self-similar solutions to the spherically symmetric ideal hydrodynamic equations. When applied to a specific example of plasma liner driven magneto-inertial fusion, the bounce-free solution is found to produce at least a factor of four improvement in dwell time and fusion energy gain.

  9. Introduction to physics mechanics, hydrodynamics thermodynamics

    CERN Document Server

    Frauenfelder, P

    2013-01-01

    Introduction of Physics: Mechanics , Hydrodynamics, Thermodynamics covers the principles of matter and its motion through space and time, as well as the related concepts of energy and force. This book is composed of eleven chapters, and begins with an introduction to the basic principles of mechanics, hydrodynamics, and thermodynamics. The subsequent chapters deal with the statics of rigid bodies and the dynamics of particles and rigid bodies. These topics are followed by discussions on elasticity, mechanics of fluids, the basic concept of thermodynamic, kinetic theory, and crystal structure o

  10. Supernova hydrodynamics experiments using the Nova laser

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)

    1997-04-01

    We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.

  11. Broken Lifshitz invariance, spin waves and hydrodynamics

    CERN Document Server

    Roychowdhury, Dibakar

    2016-01-01

    In this paper, based on the basic principles of thermodynamics, we explore the hydrodynamic regime of interacting Lifshitz field theories in the presence of broken rotational invariance. We compute the entropy current and discover new dissipative effects those are consistent with the principle of local entropy production in the fluid. In our analysis, we consider both the parity even as well as the parity odd sector upto first order in the derivative expansion. Finally, we argue that the present construction of the paper could be systematically identified as that of the hydrodynamic description associated with \\textit{spin waves} (away from the domain of quantum criticality) under certain limiting conditions.

  12. Colliding shockwaves and hydrodynamics in extreme conditions

    CERN Document Server

    Chesler, Paul M

    2015-01-01

    Using numerical holography, we study the collision of a planar sheet of energy with a bounded localized distribution of energy. The collision, which mimics proton-nucleus collisions, produces a localized lump of debris with transverse size $R \\sim 1/T_{\\rm eff}$ with $T_{\\rm eff}$ the effective temperature, and has large gradients and large transverse flow. Nevertheless, the post-collision evolution is well-described by viscous hydrodynamics. Our results bolster the notion that debris produced in proton-nucleus collisions may be modeled using hydrodynamics.

  13. Hydrodynamic interactions between nearby slender filaments

    CERN Document Server

    Man, Yi; Lauga, Eric

    2016-01-01

    Cellular biology abound with filaments interacting through fluids, from intracellular microtubules, to rotating flagella and beating cilia. While previous work has demonstrated the complexity of capturing nonlocal hydrodynamic interactions between moving filaments, the problem remains difficult theoretically. We show here that when filaments are closer to each other than their relevant length scale, the integration of hydrodynamic interactions can be approximately carried out analytically. This leads to a set of simplified local equations, illustrated on a simple model of two interacting filaments, which can be used to tackle theoretically a range of problems in biology and physics.

  14. Holography and hydrodynamics in small systems

    Science.gov (United States)

    Chesler, Paul M.

    2016-12-01

    Using holographic duality, we present results for the off-center collision of Gaussian wave packets in strongly coupled N = 4 supersymmetric Yang-Mills theory. The wave packets are thin along the collision axis and superficially at least resemble Lorentz contracted colliding protons. The collision results in the formation of a droplet of liquid of size R ∼ 1 /Teff where Teff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as proton-proton collisions.

  15. Degradation of diclofenac sodium using combined processes based on hydrodynamic cavitation and heterogeneous photocatalysis.

    Science.gov (United States)

    Bagal, Manisha V; Gogate, Parag R

    2014-05-01

    Diclofenac sodium, a widely detected pharmaceutical drug in wastewater samples, has been selected as a model pollutant for degradation using novel combined approach of hydrodynamic cavitation and heterogeneous photocatalysis. A slit venturi has been used as cavitating device in the hydrodynamic cavitation reactor. The effect of various operating parameters such as inlet fluid pressure (2-4 bar) and initial pH of the solution (4-7.5) on the extent of degradation have been studied. The maximum extent of degradation of diclofenac sodium was obtained at inlet fluid pressure of 3 bar and initial pH as 4 using hydrodynamic cavitation alone. The loadings of TiO2 and H2O2 have been optimised to maximise the extent of degradation of diclofenac sodium. Kinetic study revealed that the degradation of diclofenac sodium fitted first order kinetics over the selected range of operating protocols. It has been observed that combination of hydrodynamic cavitation with UV, UV/TiO2 and UV/TiO2/H2O2 results in enhanced extents of degradation as compared to the individual schemes. The maximum extent of degradation as 95% with 76% reduction in TOC has been observed using hydrodynamic cavitation in conjunction with UV/TiO2/H2O2 under the optimised operating conditions. The diclofenac sodium degradation byproducts have been identified using LC/MS analysis.

  16. Evolution of Hydrodynamic Field, Oil-Gas Migration and Accumulation in Songliao Basin, China

    Institute of Scientific and Technical Information of China (English)

    楼章华; 朱蓉; 金爱民; 孙毛明; 蔡希源; 迟元林

    2004-01-01

    The oil-gas migration and accumulation in the Songliao Basin were analyzed in the view of fluid dynamics by the authors. The key point of fluid dynamics is hydrodynamics. Oil-gas migration and accumulation are related closely with formation and evolution of hydrodynamic field. Based on abundant data, initial formation pressure and other parameters, such as water head were studied. They can be used to understand the present distribution of hydrodynamic field and its hydrochemical features. Generally, the hydrodynamic field in the basin is obviously asymmetrical. In its north and east part, there are the areas of centripetal flow caused by topographic relief when meteoric water permeate downwards. Its south part is an evaporation-concentration area. The central depression is an area of centrifugal flow driven by sediment compaction and its cross-formational flow area. Only at the basin margin and in the local uplifted and denudated area are the meteoric water permeating downwards areas. The centrifugal flow driven by sediment compaction is the main dynamic factor that induces oil-gas migration and accumulation and its formation period corresponding to the main stage of oil-gas migration and accumulation. Moreover, the evolution of hydrodynamic field has the cyclic property, which results in phased oil-gas migration by stages, and further dominates the terraced annular oil and gas distribution, concentric with their corresponding sags.

  17. Kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion

    Science.gov (United States)

    Akamatsu, Yukinao; Mazeliauskas, Aleksas; Teaney, Derek

    2017-01-01

    We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydrokinetic equations can be coupled to existing second-order hydrodynamic codes to incorporate the physics of these fluctuations. We first show that the kinetic response precisely reproduces the renormalization of the shear viscosity and the fractional power (∝ω3 /2) which characterizes equilibrium correlators of energy and momentum for a static fluid. Then we use the hydrokinetic equations to analyze thermal fluctuations for a Bjorken expansion, evaluating the contribution of thermal noise from the earliest moments and at late times. In the Bjorken case, the solution to the kinetic equations determines the coefficient of the first fractional power of the gradient expansion (∝1 /(τT ) 3 /2) for the expanding system. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is larger than second-order hydrodynamics for typical medium parameters used to simulate heavy ion collisions.

  18. DISPERSION OF CYLINDRICAL PARTICLES IN TURBULENT FLOWS

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-yu; LIN Jian-zhong

    2004-01-01

    With consideration of the Stokes drag and virtual mass force, the equations for mean and fluctuating velocities in rotation and translation were given for rigid cylindrical particles moving in a turbulent flow. Then the rotational and translational dispersion coefficients of particle were derived. The relationships between the dispersion coefficients and flow length scale as well as particle characteristic parameters were analyzed. The resulting dispersion coefficients were proved to decrease as the particle length increases. The conclusions are helpful for the further research on the motion of cylindrical particles in turbulent flows.

  19. Inverse scattering of dispersive stratified structures

    CERN Document Server

    Skaar, Johannes

    2012-01-01

    We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology.

  20. Physical models of polarization mode dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Menyuk, C.R.; Wai, P.K.A. [Univ. of Maryland, Baltimore, MD (United States)

    1995-12-31

    The effect of randomly varying birefringence on light propagation in optical fibers is studied theoretically in the parameter regime that will be used for long-distance communications. In this regime, the birefringence is large and varies very rapidly in comparison to the nonlinear and dispersive scale lengths. We determine the polarization mode dispersion, and we show that physically realistic models yield the same result for polarization mode dispersion as earlier heuristic models that were introduced by Poole. We also prove an ergodic theorem.

  1. ``Oenodynamic'': hydrodynamic of wine swirling

    Science.gov (United States)

    Reclari, Martino; Dreyer, Matthieu; Tissot, Stephanie; Obreschkow, Danail; Wurm, Florian; Farhat, Mohamed

    2011-11-01

    A crucial step in wine tasting is the so called ``swirling,'' necessary to release the bouquet of the wine: a gentle circular movement of the glass generates a wave propagating along the glass walls, enhancing oxygenation and mixing. Although being used in a large variety of other applications (e.g. cells cultures in orbital shaken bioreactors) this motion is not yet well understood. Using a simplified model we experimentally investigated the shape of the free surface and the mixing, and we identified a group of dimensionless parameters governing the flow. SNSF Grant CRSII2_125444.

  2. "Oenodynamic": Hydrodynamic of wine swirling

    CERN Document Server

    Reclari, Martino; Tissot, Stephanie; Obreschkow, Danail; Wurm, Florian; Farhat, Mohamed

    2011-01-01

    A crucial step in wine tasting is the so called swirling, necessary to release the bouquet of the wine: a gentle circular movement of the glass generates a wave propagating along the glass walls, enhancing oxygenation and mixing. Although being used in a large variety of other applications (e.g. cells cultures in orbital shaken bioreactors) this motion is not yet well understood. In this fluid dynamics video we show the large variety of waves shapes generated by this simple movement, and we identify a group of dimensionless parameters governing the flow.

  3. Tidal and subtidal hydrodynamics and energetics in a constricted estuary

    Science.gov (United States)

    Zarzuelo, Carmen; López-Ruiz, Alejandro; Díez-Minguito, Manuel; Ortega-Sánchez, Miguel

    2017-02-01

    The dynamics of coastal plain estuaries are mainly associated with variable tidal forcing and local winds in combination with bathymetric complexity and coastline irregularity. Specific features, such as constricted areas, can potentially affect and energize the hydrodynamics of these types of systems. Particularly, tidal range and tidal currents can be significantly amplified where the incoming tidal wave becomes constricted. In this work, the impact of a narrow constriction on a mesotidal estuary was analysed at tidal and subtidal time scales. Tidal hydrodynamics, energy fluxes and energy dissipation were determined for the entire Cádiz Bay (southwestern Spain) using the Delft3D numerical model. Field observations were used to analyse tidal propagation and energy dissipation along the bay constriction and to calibrate and test the numerical model. The results indicate that the presence of the constriction transformed and distorted the tide and increased the tidal range and flow velocities along the channel, with implications on energy dissipation. The tidal currents were oriented along-channel at the central part of the constriction, although abrupt bathymetric changes at the channel inner boundary provoked a sudden rotation of the flow. Although the energy fluxes were higher for spring tides and were strongly influenced by winds, the energy dissipation was controlled by bed shear stresses and vertical dispersion. The significance of this energy dissipation was that it destabilized the water column, which resulted in a weakly stratified system with implications on water quality. At a subtidal scale, the residual water volume exchange was the result of the combined effects of the neap/spring tides, wind and waves, whereas tides were dominant at the tidal scale.

  4. Higher-harmonic collective modes in a trapped gas from second-order hydrodynamics

    Science.gov (United States)

    Lewis, W. E.; Romatschke, P.

    2017-02-01

    Utilizing a second-order hydrodynamics formalism, the dispersion relations for the frequencies and damping rates of collective oscillations as well as spatial structure of these modes up to the decapole oscillation in both two- and three- dimensional gas geometries are calculated. In addition to higher-order modes, the formalism also gives rise to purely damped ‘non-hydrodynamic’ modes. We calculate the amplitude of the various modes for both symmetric and asymmetric trap quenches, finding excellent agreement with an exact quantum mechanical calculation. We find that higher-order hydrodynamic modes are more sensitive to the value of shear viscosity, which may be of interest for the precision extraction of transport coefficients in Fermi gas systems.

  5. Hydrodynamic evaluation of aortic cardiopulmonary bypass cannulae using particle image velocimetry.

    Science.gov (United States)

    McDonald, C I; Bolle, E; Lang, H F; Ribolzi, C; Thomson, B; Tansley, G D; Fraser, J F; Gregory, S D

    2016-01-01

    The high velocity jet from aortic arterial cannulae used during cardiopulmonary bypass potentially causes a "sandblasting" injury to the aorta, increasing the possibility of embolisation of atheromatous plaque. We investigated a range of commonly available dispersion and non-dispersion cannulae, using particle image velocimetry. The maximum velocity of the exit jet was assessed 20 and 40 mm from the cannula tip at flow rates of 3 and 5 L/min. The dispersion cannulae had lower maximum velocities compared to the non-dispersion cannulae. Dispersion cannulae had fan-shaped exit profiles and maximum velocities ranged from 0.63 to 1.52 m/s when measured at 20 mm and 5 L/min. Non-dispersion cannulae had maximum velocities ranging from 1.52 to 3.06 m/s at 20 mm and 5 L/min, with corresponding narrow velocity profiles. This study highlights the importance of understanding the hydrodynamic performance of these cannulae as it may help in selecting the most appropriate cannula to minimize the risk of thromboembolic events or aortic injury.

  6. Utilizing dimensional analysis with observed data to determine the significance of hydrodynamic solutions in coastal hydrology

    Science.gov (United States)

    Swain, Eric D.; Decker, Jeremy D.; Hughes, Joseph D.

    2014-01-01

    In this paper, the authors present an analysis of the magnitude of the temporal and spatial acceleration (inertial) terms in the surface-water flow equations and determine the conditions under which these inertial terms have sufficient magnitude to be required in the computations. Data from two South Florida field sites are examined and the relative magnitudes of temporal acceleration, spatial acceleration, and the gravity and friction terms are compared. Parameters are derived by using dimensionless numbers and applied to quantify the significance of the hydrodynamic effects. The time series of the ratio of the inertial and gravity terms from field sites are presented and compared with both a simplified indicator parameter and a more complex parameter called the Hydrodynamic Significance Number (HSN). Two test-case models were developed by using the SWIFT2D hydrodynamic simulator to examine flow behavior with and without the inertial terms and compute the HSN. The first model represented one of the previously-mentioned field sites during gate operations of a structure-managed coastal canal. The second model was a synthetic test case illustrating the drainage of water down a sloped surface from an initial stage while under constant flow. The analyses indicate that the times of substantial hydrodynamic effects are sporadic but significant. The simplified indicator parameter correlates much better with the hydrodynamic effect magnitude for a constant width channel such as Miami Canal than at the non-uniform North River. Higher HSN values indicate flow situations where the inertial terms are large and need to be taken into account.

  7. A Systematic Approach of Employing Quality by Design Principles: Risk Assessment and Design of Experiments to Demonstrate Process Understanding and Identify the Critical Process Parameters for Coating of the Ethylcellulose Pseudolatex Dispersion Using Non-Conventional Fluid Bed Process.

    Science.gov (United States)

    Kothari, Bhaveshkumar H; Fahmy, Raafat; Claycamp, H Gregg; Moore, Christine M V; Chatterjee, Sharmista; Hoag, Stephen W

    2016-07-14

    The goal of this study was to utilize risk assessment techniques and statistical design of experiments (DoE) to gain process understanding and to identify critical process parameters for the manufacture of controlled release multiparticulate beads using a novel disk-jet fluid bed technology. The material attributes and process parameters were systematically assessed using the Ishikawa fish bone diagram and failure mode and effect analysis (FMEA) risk assessment methods. The high risk attributes identified by the FMEA analysis were further explored using resolution V fractional factorial design. To gain an understanding of the processing parameters, a resolution V fractional factorial study was conducted. Using knowledge gained from the resolution V study, a resolution IV fractional factorial study was conducted; the purpose of this IV study was to identify the critical process parameters (CPP) that impact the critical quality attributes and understand the influence of these parameters on film formation. For both studies, the microclimate, atomization pressure, inlet air volume, product temperature (during spraying and curing), curing time, and percent solids in the coating solutions were studied. The responses evaluated were percent agglomeration, percent fines, percent yield, bead aspect ratio, median particle size diameter (d50), assay, and drug release rate. Pyrobuttons® were used to record real-time temperature and humidity changes in the fluid bed. The risk assessment methods and process analytical tools helped to understand the novel disk-jet technology and to systematically develop models of the coating process parameters like process efficiency and the extent of curing during the coating process.

  8. Hydrodynamics and transport in low-dimensional interacting systems

    Science.gov (United States)

    Kulkarni, Manas

    Recent ground-breaking experiments have realized strongly interacting quantum degenerate Fermi gas in a cold atomic system with tunable interactions. This has provided a table-top system which is extremely hydrodynamic in nature. This experimental realization helps us to investigate several aspects such as the interplay between nonlinearity, dissipation and dispersion. We find, for instance, that the dynamics in such a system shows near perfect agreement with a hydrodynamic theory. In collaboration with the group of John Thomas at Duke we interpreted studies of collision of two strongly interacting Fermi gases that led to shock waves which are a hallmark of nonlinear physics. Due to reasons such as the nature of interactions, higher dimensionality, these cold atomic systems are non-integrable and moreover the underlying field theory construction is mostly phenomenological in nature. On the other hand there are certain one-dimensional systems which are not only integrable but also facilitate more formal and rigorous ways of deriving the corresponding integrable field theories. One such family of models is the family of Calogero models (and their generalizations). They provide an extraordinary insight into the field of strongly correlated systems and hydrodynamics. We study the collective field theory of such models and address aspects of nonlinear physics such as Spin-Charge Interaction, Emptiness Formation Probability, Solitons etc; We derive a two-component nonlinear, nonlocal, integrable field theory. We also show that the Calogero family which is integrable even in an external harmonic trap (usually unavoidable in cold atom setups) is relatively "short ranged" thereby qualifying as a toy model for cold atom experiments. Transport in certain strongly correlated systems (impurity models) was studied using few low-dimensional techniques such as a 1/N diagrammatic expansion, Slave Boson Mean Field Theory and the Bethe Ansatz. A mesoscopic setup such as parallel

  9. Hydrodynamic discrimination of wakes caused by objects of different size or shape in a harbour seal (Phoca vitulina)

    DEFF Research Database (Denmark)

    Wieskotten, S.; Mauck, B.; Miersch, L.

    2011-01-01

    Harbour seals can use their mystacial vibrissae to detect and track hydrodynamic wakes. We investigated the ability of a harbour seal to discriminate objects of different size or shape by their hydrodynamic signature and used particle image velocimetry to identify the hydrodynamic parameters...... to the arrangement of the vortices. We tested whether the seal used highest velocities, the steepness of the gradients and the spatial extension of the wake in a second set of experiments by varying moving speed and paddle size, respectively. The subject was still able to discriminate between the respective object...... that a seal may be using to do so. Hydrodynamic trails were generated by different sized or shaped paddles that were moved in the calm water of an experimental box to produce a characteristic signal. In a two-alternative forced-choice procedure the blindfolded subject was able to discriminate size differences...

  10. Tachyonic Dispersion in Coherent Networks

    CERN Document Server

    Chong, Y D

    2015-01-01

    We propose a technique to realize a tachyonic band structure in a coherent network, such as an array of coupled ring resonators. This is achieved by adding "PT symmetric" spatially-balanced gain and loss to each node of the network. In a square-lattice network, the quasi-energy bandstructure exhibits a tachyonic dispersion relation, centered at either the center or corner of the Brillouin zone. There is one tachyonic hyperboloid in each gap, unlike in PT-symmetric tight-binding honeycomb lattices where the hyperboloids occur in pairs. The dispersion relation can be probed by measuring the peaks in transmission across a finite network as the gain/loss parameter is varied.

  11. Stabilizing geometry for hydrodynamic rotary seals

    Science.gov (United States)

    Dietle, Lannie L.; Schroeder, John E.

    2010-08-10

    A hydrodynamic sealing assembly including a first component having first and second walls and a peripheral wall defining a seal groove, a second component having a rotatable surface relative to said first component, and a hydrodynamic seal comprising a seal body of generally ring-shaped configuration having a circumference. The seal body includes hydrodynamic and static sealing lips each having a cross-sectional area that substantially vary in time with each other about the circumference. In an uninstalled condition, the seal body has a length defined between first and second seal body ends which varies in time with the hydrodynamic sealing lip cross-sectional area. The first and second ends generally face the first and second walls, respectively. In the uninstalled condition, the first end is angulated relative to the first wall and the second end is angulated relative to the second wall. The seal body has a twist-limiting surface adjacent the static sealing lip. In the uninstalled condition, the twist-limiting surface is angulated relative to the peripheral wall and varies along the circumference. A seal body discontinuity and a first component discontinuity mate to prevent rotation of the seal body relative to the first component.

  12. Hydrodynamic modelling of hydrostatic magnesium extrusion

    NARCIS (Netherlands)

    Moodij, E.; Rooij, de M.B.; Schipper, D.J.

    2006-01-01

    Wilson’s hydrodynamic model of the hydrostatic extrusion process is extended to meet the geometry found on residual billets. The transition from inlet to work zone of the process is not considered sharp as in the model of Wilson but as a rounded edge, modelled by a parabolic function. It is shown th

  13. Hydrodynamic limits of the Vlasov equation

    Energy Technology Data Exchange (ETDEWEB)

    Caprino, S. (Universita' de L' Aquila Coppito (Italy)); Esposito, R.; Marra, R. (Universita' di Roma tor Vergata, Roma (Italy)); Pulvirenti, M. (Universita' di Roma la Sapienza, Roma (Italy))

    1993-01-01

    In the present work, the authors study the Vlasov equation for repulsive forces in the hydrodynamic regime. For initial distributions at zero temperature the limit equations turn out to be the compressible and incompressible Euler equations under suitable space-time scalings. 17 refs.

  14. Microflow Cytometers with Integrated Hydrodynamic Focusing

    Directory of Open Access Journals (Sweden)

    Martin Schmidt

    2013-04-01

    Full Text Available This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex principle. The sample—A suspension of micro particles or blood cells—is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.

  15. Hydrodynamics and Roughness of Irregular Boundaries

    Science.gov (United States)

    2011-01-01

    principle component analysis (PCA) similar to that used by Preston (2009) for ship- mounted multibeam data. Several variables derived from the...complex boundaries as well as characterization of acoustic and optical processes. Turbulent processes at the seabed are at the foundation of littoral...nearshore hydrodynamics, turbulence over rough beds influences optical and acoustic properties. Bed roughness also directly affects acoustic propagation in

  16. Impact of Hydrodynamics on Oral Biofilm Strength

    NARCIS (Netherlands)

    Paramonova, E.; Kalmykowa, O. J.; van der Mei, H. C.; Busscher, H. J.; Sharma, P. K.

    2009-01-01

    Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of S

  17. Hydrodynamic erosion process of undisturbed clay

    NARCIS (Netherlands)

    Zhao, G.; Visser, P.J.; Vrijling, J.K.

    2011-01-01

    This paper describes the hydrodynamic erosion process of undisturbed clay due to the turbulent flow, based on theoretical analysis and experimental results. The undisturbed clay has the unique and complicated characteristics of cohesive force among clay particles, which are highly different from dis

  18. Hydrodynamic impact response, a flexible view

    NARCIS (Netherlands)

    Vredeveldt, A.W.; Hoogeland, M.; Janssen, G.Th.M.

    2001-01-01

    The popularity of high-speed craft is steadily increasing. Until now, much attention has been focussed on the hydrodynamic aspects of these craft. The structural design of these vessels is usually considered in a quasi static sense. However, due to the requirement of light ship structures, fast ship

  19. Hydrodynamic behavior of a combined anaerobic-aerobic system employed in the treatment of vinasse

    Directory of Open Access Journals (Sweden)

    Fátima Resende Luiz Fia

    Full Text Available ABSTRACT The understanding of reactor hydrodynamics is essential for improving the performance of a reactor and biogas production. This study sought to evaluate the hydrodynamic behavior of a combined anaerobic-aerobic system at a laboratory scale for treating vinasse. The experiment was conducted in a system using two UASB reactors connected in series, followed by an Aerated Submerged Biological Filter (ASBF. The flow rates applied to the system and the corresponded theoretical HRTs in the UASB1, UASB2 and ASBF were respectively: 15.6 L d-1 and 1.2 d, 1.2 d and 1.0 d (Phase I - first year; 8.5 L d-1 and 2.1 d; 2.1 d and 1.8 d (Phase II - first year, 14.6 L d-1 and 1.1 d, 1.1 d and 1.0 d (Phase III - second year; 29.5 L d-1 and 0.6 d, 0.6 d and 0.5 d (Phase IV - second year. The hydrodynamic studies were carried out using pulse type stimulus-response tests, employing LiCl as a tracer. The coefficients of determination for the dispersion models (R2 indicate a close approximation of a continuous stirred tank reactor in series (multi-CSTR model, with an average of 2.5, 2.3 and 1.2 (first year, and 1.1, 1.4 and 0.9 (second year multi-CSTR for UASB1, UASB2 and ASBF, respectively. Results of the hydrodynamic tests carried out in UASB1, UASB2 and ASBF indicated strong tendency for flow in the complete mixture hydraulic regime, detecting a wide dispersion in the units, in addition to the presence of short circuits and dead zones.

  20. Hydrodynamics: Fluctuating initial conditions and two-particle correlations

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, R.P.G.; Grassi, F. [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Hama, Y., E-mail: hama@fma.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Qian, W.-L. [Instituto de Fisica, Universidade de Sao Paulo (Brazil)

    2011-03-15

    Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations.

  1. Dispersion management with metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  2. Vowel dispersion in Truku

    OpenAIRE

    Chiang, Wen-yu; Chiang, Fang-mei

    2013-01-01

    This study investigates the dispersion of vowel space in Truku, an endangered Austronesian language in Taiwan. Adaptive Dispersion (Liljencrants and Lindblom, 1972; Lindblom, 1986, 1990) proposes that the distinctive sounds of a language tend to be positioned in phonetic space in a way that maximizes perceptual contrast. For example, languages with large vowel inventories tend to expand the overall acoustic vowel space. Adaptive Dispersion predicts that the distance between the point vowels w...

  3. Refining a relativistic, hydrodynamic solver: Admitting ultra-relativistic flows

    Science.gov (United States)

    Bernstein, J. P.; Hughes, P. A.

    2009-09-01

    We have undertaken the simulation of hydrodynamic flows with bulk Lorentz factors in the range 102-106. We discuss the application of an existing relativistic, hydrodynamic primitive variable recovery algorithm to a study of pulsar winds, and, in particular, the refinement made to admit such ultra-relativistic flows. We show that an iterative quartic root finder breaks down for Lorentz factors above 102 and employ an analytic root finder as a solution. We find that the former, which is known to be robust for Lorentz factors up to at least 50, offers a 24% speed advantage. We demonstrate the existence of a simple diagnostic allowing for a hybrid primitives recovery algorithm that includes an automatic, real-time toggle between the iterative and analytical methods. We further determine the accuracy of the iterative and hybrid algorithms for a comprehensive selection of input parameters and demonstrate the latter’s capability to elucidate the internal structure of ultra-relativistic plasmas. In particular, we discuss simulations showing that the interaction of a light, ultra-relativistic pulsar wind with a slow, dense ambient medium can give rise to asymmetry reminiscent of the Guitar nebula leading to the formation of a relativistic backflow harboring a series of internal shockwaves. The shockwaves provide thermalized energy that is available for the continued inflation of the PWN bubble. In turn, the bubble enhances the asymmetry, thereby providing positive feedback to the backflow.

  4. Hydrodynamic modeling of ferrofluid flow in magnetic targeting drug delivery

    Institute of Scientific and Technical Information of China (English)

    LIU Han-dan; XU Wei; WANG Shi-gang; KE Zun-ji

    2008-01-01

    Among the proposed techniques for delivering drugs to specific locations within human body, magnetic drug targeting prevails due to its non-invasive character and its high targeting efficiency. Magnetic targeting drug delivery is a method of carrying drug-loaded magnetic nanoparticles to a target tissue target under the applied magnetic field. This method increases the drug concentration in the target while reducing the adverse side-effects. Although there have been some theoretical analyses for magnetic drug targeting, very few researchers have addressed the hydrodynamic models of magnetic fluids in the blood vessel. A mathematical model is presented to describe the hydrodynamics of ferrofluids as drug carriers flowing in a blood vessel under the applied magnetic field. In this model, magnetic force and asymmetrical force are added, and an angular momentum equation of magnetic nanoparticles in the applied magnetic field is modeled. Engineering approximations are achieved by retaining the physically most significant items in the model due to the mathematical complexity of the motion equations. Numerical simulations are performed to obtain better insight into the theoretical model with computational fluid dynamics. Simulation results demonstrate the important parameters leading to adequate drug delivery to the target site depending on the magnetic field intensity, which coincident with those of animal experiments. Results of the analysis provide important information and suggest strategies for improving delivery in clinical application.

  5. Numerical Study on Hydrodynamic Performance of Bionic Caudal Fin

    Directory of Open Access Journals (Sweden)

    Kai Zhou

    2016-01-01

    Full Text Available In this work, numerical simulations are conducted to reveal the hydrodynamic mechanism of caudal fin propulsion. In the modeling of a bionic caudal fin, a universal kinematics model with three degrees of freedom is adopted and the flexible deformation in the spanwise direction is considered. Navier-Stokes equations are used to solve the unsteady fluid flow and dynamic mesh method is applied to track the locomotion. The force coefficients, torque coefficient, and flow field characteristics are extracted and analyzed. Then the thrust efficiency is calculated. In order to verify validity and feasibility of the algorithm, hydrodynamic performance of flapping foil is analyzed. The present results of flapping foil compare well with those in experimental researches. After that, the influences of amplitude of angle of attack, amplitude of heave motion, Strouhal number, and spanwise flexibility are analyzed. The results show that, the performance can be improved by adjusting the motion and flexibility parameters. The spanwise flexibility of caudal fin can increase thrust force with high propulsive efficiency.

  6. Performance characteristics in hydrodynamic water cooled thrust bearings

    Directory of Open Access Journals (Sweden)

    Farooq Ahmad Najar

    2016-09-01

    Full Text Available This paper deals with the study of the influence on performance characteristics of a thrust bearing with the introduction of cooling circuit and flow velocity of coolant within the designed thrust bearings is described. New method of cooling circuit configuration is taken into consideration and water has been chosen as a coolant here in the present work. Flow velocity of coolant, ranging from 0.5m/s to 2.0m/s is proposed. The Finite difference based numerical model has been developed in order to notice the effect on the heat transfer on a large hydrodynamic lubrication thrust bearing in-terms of its performance characteristics. In the present work, the solution of Reynolds equation, an energy equation with viscosity variation and Fourier heat conduction equations, applied with appropriate boundary conditions. From the present investigation, it is observed significant amount of heat content is removed from the bearing with the increase of flow velocity of coolant in an embedded cooling duct within the pad. An important parameter among performance characteristics has prevailed a significant increase in hydrodynamic pressure generation which in turn subsequently increases the load carrying capacity which has been never ever documented in the background literature.

  7. Hydrodynamics of gas-solids downflow fluidized bed (downer) reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.

    1999-07-01

    This study presents a semi-empirical model for the hydrodynamic flow structure in a circulating fluidized bed downer reactor. Circulating fluidized bed, or riser reactors are used in the petroleum industry for many applications including catalytic cracking, polyethylene production, calcination operations and combustion of a variety of fuels. The work in this thesis involved the development of a circulating fluidized bed riser and downer system that enables hydrodynamic studies to be carried out. The system was designed to incorporate both a riser and a downer in the same circulating operation, making it possible to conduct experimental studies on the riser and the downer separately or simultaneously. The hydrodynamics of the gas-solids downflow fluidized bed reactor were studied in a 9.3 m tall and 0.1 m i.d. circulating fluidized bed downer reactor using fluidized cracking catalyst (FCC) particles. In order to characterize the gas-solids flow structures, the following three parameters were measured: the radial distributions of the local solids holdups, the local particle velocities, and the pressure gradients along the downer column. The hydrodynamics in the co-current downflow reactor was also studied under a wide range of operating conditions. The gas-solids flow structure under zero superficial gas velocity conditions was characterized by measuring the radial distribution of the local solids holdups and particle velocities along the downer column with the superficial gas velocity set to zero. The results indicate that two basic flow regimes exist in the FCC downer system depending on the superficial gas velocity. The downer reactor was shown to have a more uniform radial flow structure compared to the riser. It also has a more uniform radial distribution of solids holdup and particle velocity as well as solids flux in both the development and fully developed zones. The highly uniform radial flow structure provides a nearly ideal plug flow condition in the

  8. An integrated Boltzmann+hydrodynamics approach to heavy ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, Hannah

    2009-04-22

    In this thesis the first fully integrated Boltzmann+hydrodynamics approach to relativistic heavy ion reactions has been developed. After a short introduction that motivates the study of heavy ion reactions as the tool to get insights about the QCD phase diagram, the most important theoretical approaches to describe the system are reviewed. The hadron-string transport approach that this work is based on is the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) approach. Predictions for the charged particle multiplicities at LHC energies are made. The next step is the development of a new framework to calculate the baryon number density in a transport approach. Time evolutions of the net baryon number and the quark density have been calculated at AGS, SPS and RHIC energies. Studies of phase diagram trajectories using hydrodynamics are performed. The hybrid approach that has been developed as the main part of this thesis is based on the UrQMD transport approach with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. The full (3+1) dimensional ideal relativistic one fluid dynamics evolution is solved using the SHASTA algorithm. Three different equations of state have been used, namely a hadron gas equation of state without a QGP phase transition, a chiral EoS and a bag model EoS including a strong first order phase transition. For the freeze-out transition from hydrodynamics to the cascade calculation two different set-ups are employed. The parameter dependences of the model are investigated and the time evolution of different quantities is explored. The hybrid model calculation is able to reproduce the experimentally measured integrated as well as transverse momentum dependent v{sub 2} values for charged particles. The multiplicity and mean transverse mass excitation function is calculated for pions, protons and kaons in the energy range from E{sub lab}=2-160 A GeV. The HBT correlation of the negatively charged pion source

  9. Simulation of Helical Flow Hydrodynamics in Meanders and Advection-Turbulent Diffusion Using Smoothed Particle Hydrodynamics

    Science.gov (United States)

    Gusti, T. P.; Hertanti, D. R.; Bahsan, E.; Soeryantono, H.

    2013-12-01

    Particle-based numerical methods, such as Smoothed Particle Hydrodynamics (SPH), may be able to simulate some hydrodynamic and morphodynamic behaviors better than grid-based numerical methods. This study simulates hydrodynamics in meanders and advection and turbulent diffusion in straight river channels using Microsoft Excel and Visual Basic. The simulators generate three-dimensional data for hydrodynamics and one-dimensional data for advection-turbulent diffusion. Fluid at rest, sloshing, and helical flow are simulated in the river meanders. Spill loading and step loading are done to simulate concentration patterns associated with advection-turbulent diffusion. Results indicate that helical flow is formed due to disturbance in morphology and particle velocity in the stream and the number of particles does not have a significant effect on the pattern of advection-turbulent diffusion concentration.

  10. Scaling supernova hydrodynamics to the laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Kane, J.O.

    1999-06-01

    Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al., Astrophys. J.478, L75 (1997) The Nova laser is used to shock two-layer targets, producing Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the interfaces between the layers, analogous to instabilities seen at the interfaces of SN 1987A. Because the hydrodynamics in the laser experiments at intermediate times (3-40 ns) and in SN 1987A at intermediate times (5 s-10{sup 4} s) are well described by the Euler equations, the hydrodynamics scale between the two regimes. The experiments are modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS, thus serving as a benchmark for PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike and bubble velocities in the experiment using potential flow theory and a modified Ott thin shell theory is presented. A numerical study of 2D vs. 3D differences in instability growth at the O-He and He-H interface of SN 1987A, and the design for analogous laser experiments are presented. We discuss further work to incorporate more features of the SN in the experiments, including spherical geometry, multiple layers and density gradients. Past and ongoing work in laboratory and laser astrophysics is reviewed, including experimental work on supernova remnants (SNRs). A numerical study of RM instability in SNRs is presented.

  11. Flow induced dispersion analysis rapidly quantifies proteins in human plasma samples

    DEFF Research Database (Denmark)

    Poulsen, Nicklas N; Andersen, Nina Z; Østergaard, Jesper;

    2015-01-01

    to cumbersome and expensive assay development. In this work a new approach for quantification based on changes in diffusivity is presented. The apparent diffusivity of an indicator molecule interacting with the protein of interest is determined by Taylor Dispersion Analysis (TDA) in a hydrodynamic flow system...

  12. Size-dispersity effects in two-dimensional melting.

    Science.gov (United States)

    Watanabe, Hiroshi; Yukawa, Satoshi; Ito, Nobuyasu

    2005-01-01

    In order to investigate the effect of size dispersity on two-dimensional melting transitions, hard-disk systems with equimolar bidispersity are studied by means of particle dynamics simulations. From the nonequilibrium relaxation behaviors of bond-orientational order parameters, we find that (i) there is a critical dispersity at which the melting transition of the hexagonal solid vanishes and (ii) the quadratic structure is metastable in a certain region of the dispersity-density parameter space. These results suggest that the dispersity not only destroys order but produces new structures under certain specific conditions.

  13. Seed dispersal in fens

    Science.gov (United States)

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  14. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  15. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  16. Perfect Dispersive Medium

    CERN Document Server

    Gupta, Shulabh

    2015-01-01

    Dispersion is at the heart of all ultrafast real-time signal processing systems across the entire electromagnetic spectrum ranging from radio-frequencies to optics. However, following Kramer-Kronig relations, these signal processing systems have been plagued with the parasitic amplitude distortions due to frequency dependent, and non-flat amplitude transmission of naturally dispersive media. This issue puts a serious limitation on the applicability and performance of these signal processing systems. To solve the above mentioned issue, a perfect dispersive medium is proposed in this work, which artificially violates the Kramer-Kronig relations, while satisfying all causality requirements. The proposed dispersive metamaterial is based on loss-gain metasurface pairs and exhibit a perfectly flat transmission response along with arbitrary dispersion in a broad bandwidth, thereby solving a seemingly unavoidable issue in all ultrafast signal processing systems. Such a metamaterial is further shown using sub-waveleng...

  17. Absorption and eigenmode calculation for one-dimensional periodic metallic structures using the hydrodynamic approximation

    DEFF Research Database (Denmark)

    Yanai, Avner; Mortensen, N. Asger; Levy, Uriel

    2013-01-01

    We develop a modal method that solves Maxwell's equations in the presence of the linearized hydrodynamic correction. Using this approach, it is now possible to calculate the full diffraction for structures with a period of the order of the plasma wavelength, including not only the transverse......, an examination of the propagation constants of these modes reveals that the absorption peaks and dips are directly related to the direction of phase propagation of the longitudinal modes. Furthermore, we formulate a variant of the plane wave expansion method, and use it to calculate the dispersion diagram...

  18. Trying to understand the ridge effect in hydrodynamic model

    CERN Document Server

    Hama, Yogiro; Grassi, Frederique; Qian, Wei-Liang

    2009-01-01

    In a recent paper, the hydrodynamic code NeXSPheRIO was used in conjunction with STAR analysis methods to study two-particle correlations as function of Delta_eta and Delta_phi. Both the ridge-like near-side and the double-hump away-side structures were obtained. However, the mechanism of ridge production was not clear. In order to understand it, we study a simple model with only one high-energy density peripheral tube in a smooth cylindrical back-ground, with longitudinal boost invariance. The results are rather surprising, but the model does produce the triple-ridge structure with one high ridge plus two lower ones placed symmetrically with respect to the former one. The shape of this structure is rather stable in a wide range of parameters.

  19. A new insight into the consistency of smoothed particle hydrodynamics

    CERN Document Server

    Sigalotti, Leonardo Di G; Klapp, Jaime; Vargas, Carlos A; Campos, Kilver

    2016-01-01

    In this paper the problem of consistency of smoothed particle hydrodynamics (SPH) is solved. A novel error analysis is developed in $n$-dimensional space using the Poisson summation formula, which enables the treatment of the kernel and particle approximation errors in combined fashion. New consistency integral relations are derived for the particle approximation which correspond to the cosine Fourier transform of the classically known consistency conditions for the kernel approximation. The functional dependence of the error bounds on the SPH interpolation parameters, namely the smoothing length $h$ and the number of particles within the kernel support ${\\cal{N}}$ is demonstrated explicitly from which consistency conditions are seen to follow naturally. As ${\\cal{N}}\\to\\infty$, the particle approximation converges to the kernel approximation independently of $h$ provided that the particle mass scales with $h$ as $m\\propto h^{\\beta}$, with $\\beta >n$. This implies that as $h\\to 0$, the joint limit $m\\to 0$, $...

  20. The Quantum Hydrodynamics System in Two Space Dimensions

    KAUST Repository

    Antonelli, Paolo

    2011-09-16

    In this paper we study global existence of weak solutions for the quantum hydrodynamics system in two-dimensional energy space. We do not require any additional regularity and/or smallness assumptions on the initial data. Our approach replaces the WKB formalism with a polar decomposition theory which is not limited by the presence of vacuum regions. In this way we set up a self consistent theory, based only on particle density and current density, which does not need to define velocity fields in the nodal regions. The mathematical techniques we use in this paper are based on uniform (with respect to the approximating parameter) Strichartz estimates and the local smoothing property. © 2011 Springer-Verlag.