Buoyant densities of phototrophic sulfur bacteria and cyanobacteria
Guerrero, R.
1985-01-01
The buoyant densities of bacterial cells are greatly influenced by the accumulation of intracellular reserve material. The buoyant density of phototrophic bacteria that are planktonic is of particular interest, since these organisms must remain in the photic zone of the water column for optimal growth. Separation of cells by their buoyant density may also be of use in separating and identifying organisms from a natural population. The bacteria used were obtained from pure cultures, enrichments, or samples taken directly from the environment.
Density Driven Removal of Sediment from a Buoyant Muddy Plume
Rouhnia, M.; Strom, K.
2014-12-01
Experiments were conducted to study the effect of settling driven instabilities on sediment removal from hypopycnal plumes. Traditional approaches scale removal rates with particle settling velocity however, it has been suggested that the removal from buoyant suspensions happens at higher rates. The enhancement of removal is likely due to gravitational instabilities, such as fingering, at two-fluid interface. Previous studies have all sought to suppress flocculation, and no simple model exists to predict the removal rates under the effect of such instabilities. This study examines whether or not flocculation hampers instability formation and presents a simple removal rate model accounting for gravitational instabilities. A buoyant suspension of flocculated Kaolinite overlying a base of clear saltwater was investigated in a laboratory tank. Concentration was continuously measured in both layers with a pair of OBS sensors, and interface was monitored with digital cameras. Snapshots from the video were used to measure finger velocity. Samples of flocculated particles at the interface were extracted to retrieve floc size data using a floc camera. Flocculation did not stop creation of settling-driven fingers. A simple cylinder-based force balance model was capable of predicting finger velocity. Analogy of fingering process of fine grained suspensions to thermal plume formation and the concept of Grashof number enabled us to model finger spacing as a function of initial concentration. Finally, from geometry, the effective cross-sectional area was correlated to finger spacing. Reformulating the outward flux expression was done by substitution of finger velocity, rather than particle settling velocity, and finger area instead of total area. A box model along with the proposed outward flux was used to predict the SSC in buoyant layer. The model quantifies removal flux based on the initial SSC and is in good agreement with the experimental data.
A change in a single gene of Salmonella typhimurium can dramatically change its buoyant density.
Baldwin, W W; Kirkish, M A; Koch, A L
1994-01-01
The growth rates and buoyant densities of a Salmonella typhimurium mutant, TL126 (proB74A+), with enhanced osmotolerance caused by proline overproduction were measured and compared with the growth rates and buoyant densities of an isogenic (wild-type) strain, TL128 (proB+ A+), with normal control of proline production. Growth rates were determined in a rich medium (Luria broth) with added NaCl to produce various osmotic strengths ranging from 300 to 2,000 mosM. At low concentrations of NaCl, ...
Evidence for osmoregulation of cell growth and buoyant density in Escherichia coli.
Baldwin, W W; Kubitschek, H. E.
1984-01-01
The buoyant density of cells of Escherichia coli B/r NC32 increased with the osmolarity of the growth medium. Growth rate and its variability were also dependent upon the osmolarity of the medium. Maximum growth rates and minimum variability of these rates were obtained in Luria broth by addition of NaCl to a concentration of about 0.23 M.
El-Amin, M.F.; Kanayama, H. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-02-15
In this paper, the integral method is used to derive a complete set of results and expressions for selected physical turbulent properties of a non-buoyant jet or momentum-dominated buoyant jet regime of small-scale hydrogen leakage. Several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), dominant turbulent kinetic energy production term, turbulent eddy viscosity and turbulent eddy diffusivity are obtained. In addition, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. Throughout this paper, experimental results from Schefer et al. [Schefer RW, Houf WG, Williams TC. Investigation of small-scale unintended releases of hydrogen: momentum-dominated regime. Int J Hydrogen Energy 2008;33(21):6373-84] and other works for the momentum-dominated jet resulting from small-scale hydrogen leakage are used in the integral method. For a non-buoyant jet or momentum-dominated regime of a buoyant jet, both the centerline velocity and centerline concentration are proportional with z{sup -1}. The effects of buoyancy-generated momentum are assumed to be small, and the Reynolds number is sufficient for fully developed turbulent flow. The hydrogen-air momentum-dominated regime or non-buoyant jet is compared with the air-air jet as an example of non-buoyant jets. Good agreement was found between the current results and experimental results from the literature. In addition, the turbulent Schmidt number was shown to depend solely on the ratio of the momentum spread rate to the material spread rate. (author)
Protoplast water content of bacterial spores determined by buoyant density sedimentation.
Lindsay, J A; Beaman, T C; Gerhardt, P
1985-01-01
Protoplast wet densities (1.315 to 1.400 g/ml), determined by buoyant density sedimentation in Metrizamide gradients, were correlated inversely with the protoplast water contents (26.4 to 55.0 g of water/100 g of wet protoplast) of nine diverse types of pure lysozyme-sensitive dormant bacterial spores. The correlation equation provided a precise method for obtaining the protoplast water contents of other spore types with small impure samples and indicated that the average protoplast dry densi...
Theoretical analysis and semianalytical solutions for a turbulent buoyant hydrogen-air jet
El-Amin, M.F.
2012-01-01
Semianalytical solutions are developed for turbulent hydrogen-air plume. We derived analytical expressions for plume centerline variables (radius, velocity, and density deficit) in terms of a single universal function, called plume function. By combining the obtained analytical expressions of centerline variables with empirical Gaussian expressions of the mean variables, we obtain semianalytical expressions for mean quantities of hydrogen-air plume (velocity, density deficit, and mass fraction).
Theoretical Analysis and Semianalytical Solutions for a Turbulent Buoyant Hydrogen-Air Jet
El-Amin, M. F.; Shuyu Sun; Amgad Salama
2012-01-01
Semianalytical solutions are developed for turbulent hydrogen-air plume. We derived analytical expressions for plume centerline variables (radius, velocity, and density deficit) in terms of a single universal function, called plume function. By combining the obtained analytical expressions of centerline variables with empirical Gaussian expressions of the mean variables, we obtain semianalytical expressions for mean quantities of hydrogen-air plume (velocity, density deficit, and mass fraction).
Unsteady turbulent buoyant plumes
Woodhouse, Mark J; Hogg, Andrew J
2015-01-01
We model the unsteady evolution of turbulent buoyant plumes following temporal changes to the source conditions. The integral model is derived from radial integration of the governing equations expressing the conservation of mass, axial momentum and buoyancy. The non-uniform radial profiles of the axial velocity and density deficit in the plume are explicitly described by shape factors in the integral equations; the commonly-assumed top-hat profiles lead to shape factors equal to unity. The resultant model is hyperbolic when the momentum shape factor, determined from the radial profile of the mean axial velocity, differs from unity. The solutions of the model when source conditions are maintained at constant values retain the form of the well-established steady plume solutions. We demonstrate that the inclusion of a momentum shape factor that differs from unity leads to a well-posed integral model. Therefore, our model does not exhibit the mathematical pathologies that appear in previously proposed unsteady i...
Harvey, R.W.; Metge, D.W.; Kinner, N.; Mayberry, N.
1997-01-01
Buoyant densities were determined for groundwater bacteria and microflagellates (protozoa) from a sandy aquifer (Cape Cod, MA) using two methods: (1) density-gradient centrifugation (DGC) and (2) Stoke's law approximations using sedimentation rates observed during natural-gradient injection and recovery tests. The dwarf (average cell size, 0.3 ??m), unattached bacteria inhabiting a pristine zone just beneath the water table and a majority (~80%) of the morphologically diverse community of free- living bacteria inhabiting a 5-km-long plume of organically-contaminated groundwater had DGC-determined buoyant densities <1.019 g/cm3 before culturing. In the aquifer, sinking rates for the uncultured 2-??m size class of contaminant plume bacteria were comparable to that of the bromide tracer (1.9 x 10-3 M), also suggesting a low buoyant density. Culturing groundwater bacteria resulted in larger (0.8-1.3 ??m), less neutrally- buoyant (1.043-1.081 g/cm3) cells with potential sedimentation rates up to 64-fold higher than those predicted for the uncultured populations. Although sedimentation generally could be neglected in predicting subsurface transport for the community of free-living groundwater bacteria, it appeared to be important for the cultured isolates, at least until they readapt to aquifer conditions. Culturing-induced alterations in size of the contaminant-plume microflagellates (2-3 ??m) were ameliorated by using a lower nutrient, acidic (pH 5) porous growth medium. Buoyant densities of the cultured microflagellates were low, i.e., 1.024-1.034 g/cm3 (using the DGC assay) and 1.017-1.039 g/cm3 (estimated from in-situ sedimentation rates), suggesting good potential for subsurface transport under favorable conditions.
Evidence that platelet buoyant density, but not size, correlates with platelet age in man
Following infusion of 51Cr-labeled autologous platelets into normal subjects, high-density (HD) and low-density (LD) platelet cohorts were isolated by prolonged centrifugation in isosmotic arabino-galactan (Stractan). Specific radio-activity of LD platelets declined rapidly post-infusion (T1/2 . 1.5 days), but specific radioactivity of HD platelets remained constant or increased over a 3--4-day period and gradually declined for 6--7 days thereafter. These differences were exaggerated when platelet cohorts enriched in LD or HD cells by slow centrifugation in high-density albumin were labeled and transfused. Mean survival of a platelet cohort enriched with HD cells was significantly (P less than 0.02) shorter (7.73 days) than that of a cohort enriched with LD cells (9.33) days). In normal subjects treated with aspirin, capacity for thromboxane synthesis was regained more rapidly (P less than 0.05) in LD than in HD platelets. HD and LD platelets differed only slightly in mean volume (HD platelets . 7.57 mu3, LD platelets . 6.87 mu3, 0.05 less than P less than 0.01). We believe the most logical interpretation of these findings is that under normal conditions in man, newly formed platelets are less dense on the average than total platelets and become more dense as they age in the circulation. Thus, specific radioactivity of LD platelets declines rapidly as these platelets move into a more dense compartment and are replaced by newly formed, unlabelled cells; specific radioactivity of HD platelets remains constant or increases as labelled platelets enter this compartment in numbers equal to or greater than the number leaving it at the end of their life span. The similarity in mean volumes of LD and HD platelets suggests that platelet size is unrelated to platelet age under normal conditions
Buoyant Norbury's vortex rings
Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder
2014-11-01
Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.
Non-Boussinesq turbulent buoyant jet of a low-density gas leaks into high-density ambient
El-Amin, Mohamed
2010-12-01
In this article, we study the problem of low-density gas jet injected into high-density ambient numerically which is important in applications such as fuel injection and leaks. It is assumed that the local rate of entrainment is consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some similarity transformations. The resulting system is solved to determine the centerline quantities which are used to get the mean axial velocity, mean concentration and mean density of the jet. Therefore, the centerline and mean quantities are used together with the governing equation to determine some important turbulent quantities such as, cross-stream velocity, Reynolds stress, velocity- concentration correlation, turbulent eddy viscosity and turbulent eddy diffusivity. Throughout this paper the developed model is verified by comparing the present results with experimental results and jet/plume theory from the literature. © 2010 Elsevier Inc. All rights reserved.
Pivovarov, M.A.; Zhang, H.; Ramakev, D.E.; Tatem, P.A.; Williams, F.W. (George Washington Univ., Washington, DC (United States). Dept. of Chemistry)
1993-02-01
This paper considers the applicability of different versions of the k-[epsilon] hypothesis of turbulence for flame modeling. Utilizing similarity solutions, the authors find that the k-[epsilon] hypothesis gives a finite radius for a weak axisymmetric plume above the heat source. The radius of this plume is defined as an eigenvalue of the boundary value problem with unknown boundary. Solving this problem with an adjusted set of parameters from the standard version of the k-[epsilon] hypothesis gives excellent agreement with experimental data for center line and radial profiles of the mean and turbulent quantities, and also for the radius of the plume and entrainment level. In contrast, the standard set of parameters, widely utilized in flame modeling, gives inaccurate predictions. Specifically, this set of parameters yields underestimates of the radius of the plume and the entrainment level. Since this same trend has been extensively observed in flame modeling, the authors conclude that the standard set of parameters for the k-[epsilon] hypothesis is inadequate, and that this is the main reason for the shortcomings of previous numerical models.
The analysis on a density stratification layer consisting of multiple gases in the reactor containment vessel is important for the safety assessment of sever accidents. The Japan Atomic Energy Agency (JAEA) has started the project on the containment thermal hydraulics. We carried out Computational Fluid Dynamics (CFD) analyses in order to investigate the erosion of the density stratification layer by a vertical buoyant jet under this project. We used the Reynolds averaged numerical simulation (RANS) and Large eddy simulation (LES) models to analyze the erosion of a density stratification layer by a vertical buoyant jet in a small vessel which represents a containment vessel. This numerical study calculates the turbulent mixing of a two-component (air and helium) gas mixture. The turbulence models used for the RANS analyses are two types of k-ε models. The first model is the low Reynolds number k-ε model developed by Launder and Sharma. The second model is revised from the first model in order to accurately consider the turbulent production and damping in a stratification layer. The results have indicated that both the RANS and LES models simulate almost the same behavior of the erosion of the density stratification layer. While the erosion rate calculated by the low-Re k-ε model was faster than that of the LES model, the modified k-ε model could calculate the erosion rate similar to the LES result. (author)
Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S-K; Turner, John Stewart
2015-10-01
Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015)], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers. PMID:26565349
Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S.-K.; Turner, John Stewart
2015-10-01
Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015), 10.1017/jfm.2015.126], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers.
Turbulent Buoyant Jets in Flowing Ambients
Chen, Hai-Bo; Larsen, Torben; Petersen, Ole
1991-01-01
The mean behaviour of horizontal turbulent buoyant jets in co-flowing currents is investigated experimentally and numerically, in terms of jet trajectory, dilution and centerline density deficit and velocity decay. It is demonstrated in the paper that the laboratory data on the jet trajectory...... of turbulent buoyant jet in the presence of arnbient current and provide a ready tool for the purpose of sea outfall design....
Turbulent buoyant jets and plumes
Rodi, Wolfgang
The Science & Applications of Heat and Mass Transfer: Reports, Reviews, & Computer Programs, Volume 6: Turbulent Buoyant Jets and Plumes focuses on the formation, properties, characteristics, and reactions of turbulent jets and plumes. The selection first offers information on the mechanics of turbulent buoyant jets and plumes and turbulent buoyant jets in shallow fluid layers. Discussions focus on submerged buoyant jets into shallow fluid, horizontal surface or interface jets into shallow layers, fundamental considerations, and turbulent buoyant jets (forced plumes). The manuscript then exami
NUMERICAL PREDICTION OF LINE BUOYANT JETS IN CROSS FLOWS
无
2001-01-01
The k-ε turbulence model was used to establish the mathematicalmodel of two-dimensional line buoyant jets in crossflow. The hybrid finite analytic method and staggered grid were applied to the calculation of line buoyant jets. Only receiving water with uniform density is considered. The distribution of velocity, temperature and turbulent kinetic energy were analyzed, and the variation of the maximum velocity was given. The effect of velocity ratio and densimetric Froude number on line buoyant jets was considered.
Abe, Satoshi, E-mail: abe.satoshi@jaea.go.jp; Ishigaki, Masahiro; Sibamoto, Yasuteru; Yonomoto, Taisuke
2015-08-15
Highlights: . • The third international benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in the reactor containment vessel. • Two types turbulence model modification were applied in order to accurately simulate the turbulence helium transportation in the density stratification. • The analysis result in case with turbulence model modification is good agreement with the experimental data. • There is a major difference of turbulence helium–mass transportation between in case with and without the turbulence model modification. - Abstract: Density stratification in the reactor containment vessel is an important phenomenon on an issue of hydrogen safety. The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project on containment thermal hydraulics. As a part of the activity, we participated in the third international CFD benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in containment vessel. This paper shows our approach for the IBE-3, focusing on the turbulence transport phenomena in eroding the density stratification and introducing modified turbulence models for improvement of the CFD analyses. For this analysis, we modified the CFD code OpenFOAM by using two turbulence models; the Kato and Launder modification to estimate turbulent kinetic energy production around a stagnation point, and the Katsuki model to consider turbulence damping in density stratification. As a result, the modified code predicted well the experimental data. The importance of turbulence transport modeling is also discussed using the calculation results.
Highlights: . • The third international benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in the reactor containment vessel. • Two types turbulence model modification were applied in order to accurately simulate the turbulence helium transportation in the density stratification. • The analysis result in case with turbulence model modification is good agreement with the experimental data. • There is a major difference of turbulence helium–mass transportation between in case with and without the turbulence model modification. - Abstract: Density stratification in the reactor containment vessel is an important phenomenon on an issue of hydrogen safety. The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project on containment thermal hydraulics. As a part of the activity, we participated in the third international CFD benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in containment vessel. This paper shows our approach for the IBE-3, focusing on the turbulence transport phenomena in eroding the density stratification and introducing modified turbulence models for improvement of the CFD analyses. For this analysis, we modified the CFD code OpenFOAM by using two turbulence models; the Kato and Launder modification to estimate turbulent kinetic energy production around a stagnation point, and the Katsuki model to consider turbulence damping in density stratification. As a result, the modified code predicted well the experimental data. The importance of turbulence transport modeling is also discussed using the calculation results
Density of aqueous solutions of CO2
Garcia, Julio E.
2001-10-10
In this report, we present a numerical representation for the partial molar volume of CO2 in water and the calculation of the corresponding aqueous solution density. The motivation behind this work is related to the importance of having accurate representations for aqueous phase properties in the numerical simulation of carbon dioxide disposal into aquifers as well as in geothermal applications. According to reported experimental data the density of aqueous solutions of CO2 can be as much as 2-3% higher than pure water density. This density variation might produce an influence on the groundwater flow regime. For instance, in geologic sequestration of CO2, convective transport mixing might occur when, several years after injection of carbon dioxide has stopped, the CO2-rich gas phase is concentrated at the top of the formation, just below an overlaying caprock. In this particular case the heavier CO2 saturated water will flow downward and will be replaced by water with a lesser CO2 content.
Analytical Solution for Stellar Density in Globular Clusters
M. A. Sharaf; A. M. Sendi
2011-09-01
In this paper, four parameters analytical solution will be established for the stellar density function in globular clusters. The solution could be used for any arbitrary order of outward decrease of the cluster’s density.
Negatively buoyant starting jets
Marugán-Cruz, C.; Rodríguez-Rodríguez, Javier; Martínez-Bazán, C.
2009-01-01
The initial development of negatively buoyant jets has been investigated experimentally and numerically, focusing on the role played by gravity in the evolution of the leading vortex ring. Under the experimental conditions considered in this work, the densimetric Froude number, Fr= ρjU²j/[(ρ₀ − ρj) gD] , which represents the ratio between the jet momentum and the buoyancy forces, emerges as the most relevant parameter characterizing the dynamics of the flow. Two different flow regimes h...
Dynamics of buoyant bubbles in clusters of galaxies
Pavlovski, Georgi; Pope, Edward C D
2007-01-01
We present a phenomenological model of the dynamics of buoyant bubbles in the atmosphere of a cluster of galaxies. The derived equations describe velocity, size, mass, temperature and density of the buoyant bubbles as functions of time based on several simple approximations. The constructed model is then used to interpret results of a numerical experiment of heating of the cluster core with buoyant bubbles in a hydrodynamical approximation (i.e. in the absence of magnetic fields, viscosity, and thermal diffusion). Based on the model parameters we discuss possible limitations of the numerical treatment of the problem, and highlight the main physical processes that govern the dynamics of bubbles in the intracluster medium.
Viscosity and density tables of sodium chloride solutions
Fair, J.A.; Ozbek, H. (comps.)
1977-04-01
A file is presented containing tabulated data extracted from the scientific literature on the density and viscosity of aqueous sodium chloride solutions. Also included is a bibliography of the properties of aqueous sodium chloride solutions. (MHR)
Turbulence Statistics of a Buoyant Jet in a Stratified Environment
McCleney, Amy Brooke
Using non-intrusive optical diagnostics, turbulence statistics for a round, incompressible, buoyant, and vertical jet discharging freely into a stably linear stratified environment is studied and compared to a reference case of a neutrally buoyant jet in a uniform environment. This is part of a validation campaign for computational fluid dynamics (CFD). Buoyancy forces are known to significantly affect the jet evolution in a stratified environment. Despite their ubiquity in numerous natural and man-made flows, available data in these jets are limited, which constrain our understanding of the underlying physical processes. In particular, there is a dearth of velocity field data, which makes it challenging to validate numerical codes, currently used for modeling these important flows. Herein, jet near- and far-field behaviors are obtained with a combination of planar laser induced fluorescence (PLIF) and multi-scale time-resolved particle image velocimetry (TR-PIV) for Reynolds number up to 20,000. Deploying non-intrusive optical diagnostics in a variable density environment is challenging in liquids. The refractive index is strongly affected by the density, which introduces optical aberrations and occlusions that prevent the resolution of the flow. One solution consists of using index matched fluids with different densities. Here a pair of water solutions - isopropanol and NaCl - are identified that satisfy these requirements. In fact, they provide a density difference up to 5%, which is the largest reported for such fluid pairs. Additionally, by design, the kinematic viscosities of the solutions are identical. This greatly simplifies the analysis and subsequent simulations of the data. The spectral and temperature dependence of the solutions are fully characterized. In the near-field, shear layer roll-up is analyzed and characterized as a function of initial velocity profile. In the far-field, turbulence statistics are reported for two different scales, one
Static solutions in general relativity with infinite central density
Flammer, Philip David
2016-01-01
This paper presents full general relativistic simulations of uniformly rotating polytropes. A logarithm is taken of the radial coordinate, which enables the study of more static solutions than previously possible. In particular, static solutions out to the limit of infinite central energy density are found for a range of adiabatic exponents. The analytic behavior for large central energy density near the origin is determined by solving Einstein's equations in spherical symmetry assuming the pressure is proportional to the energy; this agrees well with the numerical results. The allowed space of static solutions, which extends from zero central energy density to infinity, is bounded at low adiabatic exponents as gravity loses its ability to bind the matter (the radius and mass go to infinity). The stability of the solution space is studied in the case of spherical symmetry. In addition to the usual region of stability bounded by low central energy densities, we find two other separate possible regions of stabi...
Bomfimsilva, Carlos; Jorge, Joao Paulo Carrijo; Schmid, Dominique; Gomes, Rodrigo Klim [INTECSEA, Sao Paulo, SP (Brazil); Lima, Alexander Piraja [GDK, Salvador, BA (Brazil)
2009-12-19
Worldwide shipments of plastic pipes are forecasted to increase 5.2% per year since 2008, being commonly used for water supply and sewage disposal. The HDPE (High Density Polyethylene) pipes have been applied recently to deliver potable water and fire fighting water for the main pier of the LNG system in Guanabara Bay, Rio de Janeiro. The system contains three sizes of pipe outside diameter, 110 mm and 160 mm for water supply, and 500 mm for the fire fighting system. The main design challenges of the pipeline system included providing on-bottom stability, a suitable installation procedure and a proper riser design. The on-bottom stability calculations, which are quite different from the conventional steel pipelines, were developed by designing concrete blocks to be assembled on the pipeline in a required spacing to assure long term stability, knowing that plastic pipes are buoyant even in flooded conditions. The installation procedure was developed considering the lay down methodology based on surface towing technique. The riser was designed to be installed together with additional steel support structure to allow the entire underwater system to have the same plastic pipe specification up to the surface. This paper presents the main challenges that were faced during the design of the HDPE pipelines for the LNG system in Guanabara Bay, addressing the solutions and recommendations adopted for the plastic underwater pipeline system.
A solution density model for hanford waste treatment plant supernatants
The density of nuclear waste solution is used as a process control parameter in the Hanford Waste Treatment Plant pretreatment process and is crucial to tank utilization evaluations. The supernatants, however, have many different dissolved sodium salts, including nitrate, nitrite, carbonate, sulfate, phosphate, hydroxide, and aluminate. The large concentrations and diversity of salts in the waste has made the predictions of solution densities difficult historically. The purpose of this study is to determine if a new model of multi-component electrolyte solution densities, recently published in the literature, is effective at predicting the density of nuclear waste supernatants. A statistically designed set of solution densities containing the most prevalent electrolytes in Hanford tank waste was used for model validation. The densities of the simulants were calculated by the model and compared to the experimentally determined densities. The average model error was just 0.1%. These results indicate that the model can be used to accurately predict the density of nuclear waste processed at the Hanford Waste Treatment Plant. (authors)
Mixing by turbulent buoyant jets in slender containers
Voropayev, S.I., E-mail: s.voropayev@nd.edu [Environmental Fluid Dynamics Laboratories, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, 117851 (Russian Federation); Nath, C.; Fernando, H.J.S. [Environmental Fluid Dynamics Laboratories, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States)
2012-10-01
A turbulent buoyant jet injected vertically into a slender cylinder containing a stratified fluid is investigated experimentally. The working fluid is water, and salt is used to change its density to obtain either a positively or negatively buoyant jet. The interest is the vertical density distribution in container and its dependence on time and other parameters. For each case (lighter or heavier jet) the experimental data could be collapsed into a ‘universal’ time dependent behavior, when properly non-dimensionalized. A theoretical model is advanced to explain the results. Possible applications include refilling of crude oil into U.S. strategic petroleum reserves caverns. -- Highlights: ► We addresses a critical issue on refill of Strategic Petroleum Reserves. ► We conduct experiments on negatively/positively buoyant turbulent jets in long cavern. ► Basing on results of experiments we developed theoretical model for refill operations.
Laboratory Study of Dispersion of Buoyant Surface Plumes
Petersen, Ole; Larsen, Torben
1990-01-01
A laboratory a study on surface dispersion of buoyant plumes in open channel turbulence in made, where the buoyancy is due to both salinity and heat. The measured parameters are the downstream derivative of a plume width and height, which are integral-characteristics of the distributions of density......-differences. Other methods as infra-red sensing are used for visualizing purpose. The results are used to calibrate an integral model of the dispersion. Conclusions are that the dispersion of a buoyant surface plume can be treated the superposition of a buoyancy induced stretching and turbulent diffusion, reduced in...
Densities concentrations of aqueous of uranyl nitrate solutions
The ratio density-concentration of aqueous uranyl nitrate solutions expressed as U3O8 grams/liter, U grams/liter and hexahydrate uranyl nitrate weight percent at different temperatures, are established. Experimental values are graphically correlated and compared whit some published data. (Author) 2 refs
EFFECTIVE POROSITY IMPLIES EFFECTIVE BULK DENSITY IN SORBING SOLUTE TRANSPORT
Flach, G.
2012-02-27
The concept of an effective porosity is widely used in solute transport modeling to account for the presence of a fraction of the medium that effectively does not influence solute migration, apart from taking up space. This non-participating volume or ineffective porosity plays the same role as the gas phase in single-phase liquid unsaturated transport: it increases pore velocity, which is useful towards reproducing observed solute travel times. The prevalent use of the effective porosity concept is reflected by its prominent inclusion in popular texts, e.g., de Marsily (1986), Fetter (1988, 1993) and Zheng and Bennett (2002). The purpose of this commentary is to point out that proper application of the concept for sorbing solutes requires more than simply reducing porosity while leaving other material properties unchanged. More specifically, effective porosity implies the corresponding need for an effective bulk density in a conventional single-porosity model. The reason is that the designated non-participating volume is composed of both solid and fluid phases, both of which must be neglected for consistency. Said another way, if solute does not enter the ineffective porosity then it also cannot contact the adjoining solid. Conceptually neglecting the fluid portion of the non-participating volume leads to a lower (effective) porosity. Likewise, discarding the solid portion of the non-participating volume inherently leads to a lower or effective bulk density. In the author's experience, practitioners virtually never adjust bulk density when adopting the effective porosity approach.
Buoyant Nanoparticles: Implications for Nano-Biointeractions in Cellular Studies.
Watson, C Y; DeLoid, G M; Pal, A; Demokritou, P
2016-06-01
In the safety and efficacy assessment of novel nanomaterials, the role of nanoparticle (NP) kinetics in in vitro studies is often ignored although it has significant implications in dosimetry, hazard ranking, and nanomedicine efficacy. It is demonstrated here that certain nanoparticles are buoyant due to low effective densities of their formed agglomerates in culture media, which alters particle transport and deposition, dose-response relationships, and underestimates toxicity and bioactivity. To investigate this phenomenon, this study determines the size distribution, effective density, and assesses fate and transport for a test buoyant NP (polypropylene). To enable accurate dose-response assessment, an inverted 96-well cell culture platform is developed in which adherent cells are incubated above the buoyant particle suspension. The effect of buoyancy is assessed by comparing dose-toxicity responses in human macrophages after 24 h incubation in conventional and inverted culture systems. In the conventional culture system, no adverse effects are observed at any NP concentration tested (up to 250 μg mL(-1) ), whereas dose-dependent decreases in viability and increases in reactive oxygen species are observed in the inverted system. This work sheds light on an unknown issue that plays a significant role in vitro hazard screening and proposes a standardized methodology for buoyant NP assessments. PMID:27135209
Buoyant currents arrested by convective dissolution
MacMinn, Christopher W.; Juanes, Ruben
2013-05-01
When carbon dioxide (CO2) dissolves into water, the density of water increases. This seemingly insubstantial phenomenon has profound implications for geologic carbon sequestration. Here we show, by means of laboratory experiments with analog fluids, that the up-slope migration of a buoyant current of CO2 is arrested by the convective dissolution that ensues from a fingering instability at the moving CO2-groundwater interface. We consider the effectiveness of convective dissolution as a large-scale trapping mechanism in sloping aquifers, and we show that a small amount of slope is beneficial compared to the horizontal case. We study the development and coarsening of the fingering instability along the migrating current and predict the maximum migration distance of the current with a simple sharp-interface model. We show that convective dissolution exerts a powerful control on CO2 plume dynamics and, as a result, on the potential of geologic carbon sequestration.
Anharmonic densities of states: A general dynamics-based solution
Jellinek, Julius; Aleinikava, Darya
2016-06-01
Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.
Fast Density Inversion Solution for Full Tensor Gravity Gradiometry Data
Hou, Zhenlong; Wei, Xiaohui; Huang, Danian
2016-02-01
We modify the classical preconditioned conjugate gradient method for full tensor gravity gradiometry data. The resulting parallelized algorithm is implemented on a cluster to achieve rapid density inversions for various scenarios, overcoming the problems of computation time and memory requirements caused by too many iterations. The proposed approach is mainly based on parallel programming using the Message Passing Interface, supplemented by Open Multi-Processing. Our implementation is efficient and scalable, enabling its use with large-scale data. We consider two synthetic models and real survey data from Vinton Dome, US, and demonstrate that our solutions are reliable and feasible.
Solvent density mode instability in non-polar solutions
Susmita Kar; Ranjit Biswas; J Chakrabarti
2008-08-01
We analyse the origin of the multiple long time scales associated with the long time decay observed in non-polar solvation dynamics by linear stability analysis of solvent density modes where the effects of compressibility and solvent structure are systematically incorporated. The coupling of the solute–solvent interactions at both ground and excited states of the solute with the compressibility and solvent structure is found to have important effects on the time scales. The present theory suggests that the relatively longer time constant is controlled by the solvent compressibility, while the solvent structure at the nearest-neighbour length scale dominates the shorter time constant.
In order to calculate criticality parameters of nuclear fuel solution systems, number density of nuclides are needed and they are generally estimated from density equations. Most of the relations allowing the calculation of the density of aqueous solutions containing the electrolytes HNO3-UO2(NO3)2-Pu(NO3)4, usually called 'nitrate dilution laws' are strictly empirical. They are obtained from a fit of assumed polynomial expressions on experimental density data. Out of their interpolation range, such mathematical expressions show discrepancies between calculated and experimental data appearing in the high concentrations range. In this study, a physico-chemical approach based on the isopiestic mixtures rule is suggested. The behaviour followed by these mixtures was first observed in 1936 by Zdanovskii and expressed as: 'Binary solutions (i.e. one electrolyte in water) having a same water activity are mixed without variation of this water activity value'. With regards to this behaviour, a set of basic thermodynamic expressions has been pointed out by Ryazanov and Vdovenko in 1965 concerning enthalpy, entropy, volume of mixtures, activity and osmotic coefficient of the components. In particular, a very simple relation for the density is obtained from the volume mixture expression depending on only two physico-chemical variables: i) concentration of each component in the mixture and in their respectively binary solutions having the same water activity as the mixture and ii), density of each component respectively in the binary solution having the same water activity as the mixture. Therefore, the calculation needs the knowledge of binary data (water activity, density and concentration) of each component at the same temperature as the mixture. Such experimental data are largely published in the literature and are available for nitric acid and uranyl nitrate. Nevertheless, nitric acid binary data show large discrepancies between the authors and need to be revised. In the
An Experimental Investigation on Inclined Negatively Buoyant Jets
Bashitialshaaer, Raed; Larson, Magnus; Persson, Kenneth M.
2012-01-01
An experimental study was performed to investigate the behavior of inclined negatively buoyant jets. Such jets arise when brine is discharged from desalination plants. A turbulent jet with a specific salinity was discharged through a circular nozzle at an angle to the horizontal into a tank with fresh water and the spatial evolution of the jet was recorded. Four different initial jet parameters were changed, namely the nozzle diameter, the initial jet inclination, the jet density and the flow...
Hydrodynamic modeling of towed buoyant submarine antenna's in multidirectional seas.
Geiger, Sam R.
2000-01-01
A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a three-dimensional random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions (significant wave height, development of sea), tow angle, and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model...
Compressibility effects in some buoyant flows
Gauthier, S; Lafay, M-A; Lombard, V; Boudesocque-Dubois, C; Clarisse, J-M; Le Creurer, B [CEA, DIF, F-91297 Arpajon Cedex (France)], E-mail: Serge.Gauthier@cea.fr
2008-12-15
Compressibility effects in buoyant flows are studied on three examples: the classical Rayleigh-Taylor instability (RTI) for compressible miscible flows, the ablation front instability and the thermal convection of Rayleigh-Benard. The linear analysis of the classical RTI for viscous flows is performed and the opposite effects of stratification and compressibility on the growth rate are pointed out. Some investigations in the nonlinear regime have also been carried out and show that the trend observed in the linear regime usually holds. On the other hand, a 2D simulation, started from rest and pursued until the return toward mechanical equilibrium of the mixing exhibits a typical compressibility effect, an acoustic wave, damped by the physical viscosity. The ablation front instability is detailed on the 'laser imprint' problem of direct drive irradiation. The linear stability analysis is performed on an unsteady mean flow given by the self-similar solutions of gas dynamics equations with nonlinear heat conduction. Compressibility effects are studied through the Kovasznay modes. It appears that maximum amplitudes are achieved for zero wave number, and complex wave-like structures are observed. Analogy with the large-scale instability, which occurs in compressible thermal convection, is suggested. These results have been obtained with an autoadaptive dynamical multidomain Chebyshev method.
Modified density equation for aqueous solution with plutonium(IV) and nitric acid
In order to calculate criticality parameters for solution systems, the number densities of nuclides are needed and usually calculated by use of density equations. For the system of aqueous solution with Pu(IV) and nitric acid, Maimoni's equation based on Hofstetters' density data was often used, but its reliability was not thoroughly examined. The author, therefore, derived a modified density equation by regression analysis for Hofstetters' data, adding the authors' density data of aqueous solution with nitric acid. Comparison between both equations showed that the modified density equation gives more reliable densities in the wide range of temperature and concentration. (author)
Wind influence on a coastal buoyant outflow
Whitney, Michael M.; Garvine, Richard W.
2005-03-01
This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.
Classification and prediction of buoyant surface discharges
This paper reports on effluents that are often discharged into riverine, estuarine, and costal waters at or near the surface of the receiving water body. Although government regulations generally limit or prohibit surface discharges containing industrial or municipal pollutants, several exceptions exist, such as the discharge of heated water from power plants, and the discharge of effluent from combined sewer overflows. Past efforts to predict the dilution and geometric characteristics of buoyant surface flows have relied on integral modelling techniques involving the solution of a series of differential equations. Although these models have proven successful in predicting simple surface flows, they are extremely limited in applicability due to their inability to account for boundary interaction, strong buoyancy, and recirculating. The proposed method is a two step process involving: classification of the flow depending on the most significant discharge and ambient characteristics, and quantitative prediction of flow through use of simple analytical expressions applied to limited regions within the flow. Classification of the flow is used to distinguish between the great variety of flow patterns that exist under widely differing ambient and discharge conditions. Mathematical prediction of dilution and geometric parameters of the flow (width, depth and centerline trajectory) requires the use of length scales to delineate subregions within the flow. Analytical expressions based on perturbation solutions of the governing equations are applied to each subregion. Although the proposed methodology could be done in any of several frameworks, the authors have chose that of a computer expert system which provides a practical engineering tool for both design and regulatory use
Dilution of Buoyant Surface Plumes
Larsen, Torben; Petersen, Ole
The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls.......The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls....
Duer, W. C.; And Others
1977-01-01
Discusses comparisons of packing densities derived from known molar volume data of liquids and solutions. Suggests further studies for using assemblies of spheres as models for simple liquids and solutions. (MLH)
Singh Aurora, Tarlok
2013-04-01
In introductory physics, students verify Archimedes' principle by immersing an object in water in a container, with a side-spout to collect the displaced water, resulting in a large uncertainty, due to surface tension. A modified procedure was introduced, in which a plastic bucket is suspended from a force sensor, and an object hangs underneath the bucket. The object is immersed in water in a glass beaker (without any side spout), and the weight loss is measured with a computer-controlled force sensor. Instead of collecting the water displaced by the object, tap water was added to the bucket to compensate for the weight loss, and the Archimedes' principle was verified within less than a percent. With this apparatus, buoyant force was easily studied as a function of volume of displaced water; as well as a function of density of saline solution. By graphing buoyant force as a function of volume (or density of liquid), value of g was obtained from slope. Apparatus and sources of error will be discussed.
Experimental investigations in turbulent buoyant jets of sodium
Axisymmetric, turbulent buoyant jets are investigated in the sodium test section TEFLU. The character of the flow is divided into three regimes depending on the densimetric Froude number: the pure jet, the buoyant jet in the transition regime and the pure plume. By means of a temperature compensated Miniature Permanentmagnet Flowmeter Probe the mean velocity, mean temperature and intensity of temperature fluctuations are measured simultaneously at axial distances between 3 and 40 initial jet diameters from the orifice. The functional principle of the Miniature Permanentmagnet Flowmeter Probe which allows velocity measurements to be made in the presence of a temperature gradient is described in detail. For all three regimes both the decay laws of the quantities measured along the axis of the containment pipe and the radial profiles are indicated and discussed. With the help of the radial profiles of the mean quantities the axial development of the half-width radii and the axial development of the momentum, buoyancy and volume fluxes are calculated. In addition, the time history of the temperature fluctuations is recorded at several radial positions. The data are analysed according to characteristic values of statistical signal analysis such as minimum value, maximum value, skewness, flatness and according to characteristic functions such as probability density function, autopower spectrum density and autocorrelation function. The experimental results for the axisymmetric, turbulent buoyant jets of sodium are compared with experimental results from the literature and with fluids of molecular Prandtl numbers greater than or equal to 0.7. The basic differences betwen the experimental results obtained for water and for sodium are outlined. Statements are formulated which allow thermo- and fluiddynamic diffusion processes to be transferred from water to sodium. (orig.)
Ions in solution: Density Corrected Density Functional Theory (DC-DFT)
Kim, Min-Cheol; Burke, Kieron
2014-01-01
Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to identify such cases, and how DC-DFT applies more generally. To illustrate, we calculate potential energy surfaces of HO$\\cdot$Cl$^-$ and HO$\\cdot$H$_2$O complexes using various common approximate functionals, with and without this density correction. Commonly used approximations yield wrongly shaped surfaces and/or incorrect minima when calculated self consistently, while yielding almost identical shapes and minima when density corrected. This improvement is retained even in the presence of implicit solvent.
Infrared Sensing of Buoyant Surface Plumes
Petersen, Ole; Larsen, Torben
1988-01-01
This paper is concerned with laboratory experiments on buoyant surface plumes where heat is the source of buoyancy. Temperature distributions were measured at the water surface using infra-red sensing, and inside the waterbody a computer based measurement system was applied. The plume is described...
46 CFR 160.010-3 - Inflatable buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Inflatable buoyant apparatus. 160.010-3 Section 160.010-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-3 Inflatable buoyant apparatus. (a)...
46 CFR 160.010-6 - Capacity of buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Capacity of buoyant apparatus. 160.010-6 Section 160.010-6 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-6 Capacity of buoyant apparatus. (a)...
Spatial DNS of flow transition of a rectangular buoyant reacting free-jet*
Jiang, X.; Luo, K. H.
2001-10-01
This paper describes a spatial direct numerical simulation (DNS) of the flow transition of a buoyant diffusion flame established on a rectangular nozzle with an aspect ratio of 2:1. Combustion is represented by a one-step finite-rate Arrhenius chemistry. Without applying external perturbations, large vortical structures develop naturally in the flow field due to buoyancy effects. The vortex dynamics of the rectangular buoyant reacting jet has been analysed. The interaction between density gradients and gravity initiates the flow vorticity in the cross-streamwise directions. The streamwise vorticity is mainly generated by the vortex stretching. Downstream of the reacting jet, a more disorganized flow regime characterized by small scales has been observed, following the breakdown of the large vortical structures due to three-dimensional vortex interactions. Analysis of the energy spectra shows that the spatially developing reacting jet has a tendency of transition to turbulence under the effects of combustion-induced buoyancy. Buoyancy effects are found to be very important to the formation, development, interaction and breakdown of vortices. In contrast with the relaminarization effects of chemical exothermicity on non-buoyant jet diffusion flames via volumetric expansion and viscous damping, the tendency towards transition to turbulence in buoyant reacting jets is greatly enhanced by the overwhelming buoyancy effects. Calculations of the mean flow property show that the rectangular buoyant reacting jet has a higher entrainment rate than its non-reacting counterpart.
Simulated Annealing of Two Electron Density Solution Systems
Neto, Mario de Oliveira; Alonso, Ronaldo Luiz; Leite, Fabio Lima; Jr, Osvaldo N. Oliveira; Polikarpov, Igor; Mascarenhas, Yvonne Primerano
2008-01-01
Many structural studies have been performed with a combination of SAXS and simulated annealing to reconstruct three dimensional models. Simulated annealing is suitable for the study of monodisperse, diluted and two-electron densities systems. In this chapter we showed how the simulated annealing procedure can be used to minimize the discrepancy between two functions: the simulated intensity and the experimental one-dimensional SAXS curve. The goal was to find the most probable form for a prot...
Settling of almost neutrally buoyant particles in homogeneous isotropic turbulence
van Hinsberg, Michel; Clercx, Herman; Toschi, Federico
2015-11-01
Settling of particles in a turbulent flow occurs in various industrial and natural phenomena, examples are clouds and waste water treatment. It is well known that turbulence can enhance the settling velocity of particles. Many studies have been done, numerically and experimentally to investigate this behavior for the case of ``heavy'' particles, with particle to fluid density ratios above 100. Here we investigate the case of almost neutrally buoyant particles, i.e. density ratios between 1 and 100. In the case of light particles the Maxey-Riley equations cannot be simplified to only the Stokes drag and gravity force as pressure gradient, added mass and Basset history force are important as well. We investigate the influence of these forces on the settling velocity of particles and show that the extra forces can both increase or decrease the settling velocity, depending on the combination of the Stokes number and gravity applied.
Investigations of a turbulent buoyant sodium jet
The paper describes an experimental investigation of a turbulent buoyant sodium jet which was discharging into a slowly moving ambient. Measurements of mean velocity, mean temperature and temperature fluctuations were made using a miniature permanent magnet flowmeter probe for a range of conditions encompassing forced convection jets, buoyant jets and plumes. The geometrical arrangement departed from that for a classical free jet in that the jet emerged into a confined co-flow but the essential characteristics of free jet behaviour were observed. The decay of axial velocity was broadly the same as for fluid of higher Prandtl number. The decay of mean temperature differences and temperature fluctuations were different from that for fluids of higher Prandtl number due to the importance of molecular diffusion in heat transport. (author)
ROUNDED FLOWING STATES OF OBSTRUCTED BUOYANT JET
HUAI Wen-xin; FANG Shen-guang
2006-01-01
The mutual relationships of three effective factors, the diameter D/d (d is the diameter of exit) of obstructed plate, exit densimetric Froude number and the distance H/d of the plate from jet orifice for obstructed buoyant jet in static ambient, are analyzed to explain normal and abnormal rounded flowing (reverberated and bifurcated flowing).The critical Froude numbers for obstructed buoyant jets with H/d=2, 4, 6, 8 which distinguished normal and abnormal flowing pattern are obtained. Normal rounded flowing is found only for a plate under a special value of H/d. A fitted formula of critical Froude numbers with H/d and D/d is presented to distinguish rounded flowing types. The occurring of reverberated or bifurcated flowing in abnormal rounded flow is analyzed. Based on the results of obstructed buoyant jets with D/d=1, normal rounded flowing occurred only for all conditions and axial dilution behind the plate under different H/D is obtained.
Ruxu Lian; Lan Huang; Jian Liu
2012-01-01
We consider the exterior problem and the initial boundary value problem for the spherically symmetric isentropic compressible Navier-Stokes equations with density-dependent viscosity coefficient in this paper. For regular initial density, we show that there exists a unique global strong solution to the exterior problem or the initial boundary value problem, respectively. In particular, the strong solution tends to the equilibrium state as $t\\to +\\infty $ .
LI Zhi-Bing; WANG Wei-Liang
2006-01-01
We derive the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external Geld parallel to the tube axis.
Li, Zhibing; Wang, Weiliang
2006-01-01
We derived the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external field parallel to the tube axis.
46 CFR 108.697 - Buoyant work vests.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Buoyant work vests. 108.697 Section 108.697 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Miscellaneous Equipment § 108.697 Buoyant work vests. (a) Each buoyant work vest on a unit must be approved under Subpart 160.053 or...
Analytical solutions of the problem of violent explosions in a plasma of varying density
Analytical solutions of the non-linear problem of violent explosions in a plasma of varying density under power law have been obtained. A critical law for a medium of decreasing density from the source of explosion is determined for which the problem admits a very simple solution but beyond this critical line analytical solutions admit another discontinuity automatically occuring inside a blast wave region. It is assumed that a disturbance caused by violent explosion due to sudden release of immense amount of energy is expanding very rapidly and is headed by a strong MHD shock wave. It is found that the discontinuity appearing inside a blast wave region causes a violation of continuum theory in the physical plane and consequently a cavity is formed. Analytical solutions predict that just before a discontinuity appears, the gas pressure falls to zero and the solution breaks down and can not be extended further. (Auth.)
Probing Ionic Liquid Aqueous Solutions Using Temperature of Maximum Density Isotope Effects
Mohammad Tariq
2013-03-01
Full Text Available This work is a new development of an extensive research program that is investigating for the first time shifts in the temperature of maximum density (TMD of aqueous solutions caused by ionic liquid solutes. In the present case we have compared the shifts caused by three ionic liquid solutes with a common cation—1-ethyl-3-methylimidazolium coupled with acetate, ethylsulfate and tetracyanoborate anions—in normal and deuterated water solutions. The observed differences are discussed in terms of the nature of the corresponding anion-water interactions.
A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π(1+√w-1), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at "maximum power density operating pressure" requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.
Reimund, Kevin K. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; McCutcheon, Jeffrey R. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; Wilson, Aaron D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-08-01
A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π/(1+√w⁻¹), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at “maximum power density operating pressure” requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.
Do finite size neutrally buoyant particles cluster?
Fiabane, Lionel; Pinton, Jean-Francois; Monchaux, Romain; Cartellier, Alain; Bourgoin, Mickael
2012-01-01
We investigate the preferential concentration of particles which are neutrally buoyant but with a diameter significantly larger than the dissipation scale of the carrier flow. Such particles are known not to behave as flow tracers (Qureshi et al., Phys. Re. Lett. 2007) but whether they do cluster or not remains an open question. For this purpose, we take advantage of a new turbulence generating apparatus, the Lagrangian Exploration Module which produces homogeneous and isotropic turbulence in a closed water flow. The flow is seeded with neutrally buoyant particles with diameter 700\\mum, corresponding to 4.4 to 17 times the turbulent dissipation scale when the rotation frequency of the impellers driving the flow goes from 2 Hz to 12 Hz, and spanning a range of Stokes numbers from 1.6 to 24.2. The spatial structuration of these inclusions is then investigated by a Voronoi tesselation analysis, as recently proposed by Monchaux et al. (Phys. Fluids 2010), from images of particle concentration field taken in a las...
Buoyant jet and two-phase jet-plume modeling for application to large water pools
Norman, Timothy L. [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Westinghouse Nuclear, Madison, PA 15663 (United States); Revankar, Shripad T., E-mail: shripad@ecn.purdue.ed [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-780 (Korea, Republic of)
2011-05-15
Highlights: A two-phase jet-plume model was developed to predict pool thermal response, pool surface temperature and consequently the pool cover gas pressure in enclosed spaces such as nuclear reactor wetwell. The jet-plume half-width, centerline velocity and temperature along the axis defining the plume's trajectory were solved as variables along the path. The pool surface temperature prediction is comparable to experimental data within 0.5 {sup o}C. - Abstract: Models of a single-phase liquid-into-liquid buoyant jet and a two-phase vapor-into-liquid turbulent jet-plume injected in horizontal orientation were developed for analyzing the dynamics of the mixing characteristics and thermal response for shallow submergence of the source in large pools. These models were developed from the Reynolds averaged Navier-Stokes equations in the cylindrical system for steady axisymmetric flow and incorporated the integral plume theory. The bases for the general assumptions such as self-similarity and use of Gaussian profiles to represent the velocity field across the effluent cross-section are examined. Subroutines were developed to reproduce the governing differential equations formulated from the continuity, momentum and conservation of buoyancy or energy equations which treats the jet-plume's half-width, velocity and temperature as variables and seek solutions of these variables along the jet-plume trajectory. Information on empirical closure relations obtained from experimental data such as the coefficient-of-entrainment, bubble slip velocity, momentum amplification factor, and plume spread-ratios for buoyancy and density-defect which are available for adiabatic cases were applied to the case of steam-into-water. Solutions were obtained without cross-flow in a linearly stratified ambient and then with cross-flow in a homogeneously mixed ambient for the single-phase formulation that represents a complete condensation scenario of a buoyant jet. The model was
Rudnicki, M. D.; Elderfield, H.
1993-07-01
The kinetics of iron particle formation in the neutrally buoyant plume above the TAG vent field (26 degrees N, Mid-Atlantic Ridge) have been calculated from submersible-collected CTD data within the initial 150 m of plume rise. Results show that particles form by a two-stage process: about half the iron in the high temperature vent fluid is removed as sulfides within a few seconds of venting and the remainder is removed by Fe 2+ oxidation. The pseudo-first-order rate constant for the second process has been calculated ( k1 = 0.329min -1, similar to literature values for seawater) and gives a halflife time for Fe 2+ in solution of 2.1 minutes. The kinetics of iron particle formation have been used in a conceptual model of the chemistry of the TAG plume. The average dilution at which iron oxyhydroxide particles form, E¯ Fe, is ˜ 570 from which element/Fe ratios of particles at the top of the buoyant plume have been predicted. Oxyanion/Fe ratios can be chiefly accounted for by coprecipitation for Cr (71%), V (67%), As (45%) and P (42%) but Mo (0.1%) and U (0.02%) show anomalously low coprecipitation. Th/Fe and REE/Fe ratios are greater than can be accounted for by coprecipitation, demonstrating that scavenging occurs in the buoyant plume for these elements. 98% of the Th uptake and 15-75% of the REE uptake is by scavenging. Scavenging rate constants are 3.1 * 10 -6 (nmol/kg) -1 s -1 for Th and 1.4-33* 10 -8 (nmol/kg) -1 s -1 for the REE. A scavenging model has been fitted to trace metal data previously reported for neutrally buoyant hydrothermal plume particulate samples collected above the TAG vent field. The model is based on the assumption that there is a characteristic t1/2 for the dilution of the neutrally buoyant plume and this value has been calculated, by comparing 228Th and 230Th with 234Th isotope data, as fourty-one days (λ p = 0.0170 day -1). Scavenging rate constants are 2* 10 -9 (nmol/kg) -1 s -1 for Th and 3.5-16*10 -11 (nmol/kg) -1 s -1 for the REE
Rajamane, N. P.; Nataraja, M. C.; Jeyalakshmi, R.; Nithiyanantham, S.
2016-02-01
Geopolymer concrete is zero-Portland cement concrete containing alumino-silicate based inorganic polymer as binder. The polymer is obtained by chemical activation of alumina and silica bearing materials, blast furnace slag by highly alkaline solutions such as hydroxide and silicates of alkali metals. Sodium hydroxide solutions of different concentrations are commonly used in making GPC mixes. Often, it is seen that sodium hydroxide solution of very high concentration is diluted with water to obtain SHS of desired concentration. While doing so it was observed that the solute particles of NaOH in SHS tend to occupy lower volumes as the degree of dilution increases. This aspect is discussed in this paper. The observed phenomenon needs to be understood while formulating the GPC mixes since this influences considerably the relationship between concentration and density of SHS. This paper suggests an empirical formula to relate density of SHS directly to concentration expressed by w/w.
Borrero-Echeverry, Daniel
2016-01-01
We show that aqueous solutions of ammonium thiocyanate (NH4SCN) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize some of the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.
46 CFR 131.870 - Life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Life floats and buoyant apparatus. 131.870 Section 131.870 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly...
Similarity consideration of the buoyant jet resulting from hydrogen leakage
El-Amin, M.F.; Kanayama, H. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-07-15
In this paper, the similarity form is developed of a hydrogen-air buoyant jet 'forced plume' resulting from an unignited small-scale hydrogen leakage in the air. As the domain temperature is assumed to be constant and therefore the density of the mixture is a function of the concentration only, the hydrogen-air mixture is assumed to be of a linear mixing type. The rate of entrainment is assumed to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. The local rate of entrainment may be considered to be consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. Consequently, the entrainment coefficient is taken as a variable not constant. The density will be considered as a variable in all terms of the equations of continuity, momentum and concentration. The integral models of the mass, momentum and concentration fluxes are obtained. Non-dimensional transformations known as similarity transformations and used to transform the integral model to a set of ordinary differential equations called similarity equations which are solved numerically. Under various values of Froude number, the hydrogen centerline mass fraction, jet width and centerline velocity are introduced and compared with published experimental results for a slow leak vertical hydrogen jet. (author)
Subgrid Scale Modeling for Large Eddy Simulation of Buoyant Turbulent Flows
Ghaisas, Niranjan Shrinivas
2013-01-01
Buoyancy effects due to small density differences commonly exist in turbulent fluid flows occurring in nature and in engineering applications. The large eddy simulation (LES) technique, which is being increasingly used for simulating buoyant turbulent flows, requires accurate modeling of the subgrid sclae (SGS) momentum and buoyancy fluxes. This thesis presents a series of LES and direct numerical simulation (DNS) studies towards a priori and a posteriori evaluation of existing SGS models, an...
Numerical solution for Nagumo's equation for the electron density in photorefractive materials
Magaña, Fernando
2005-03-01
We study the distribution of the electron density in a photorefractive material, using a set of nonlinear partial differential equations, that describes the physical response of photorefractive systems under inhomogeneous ilumination based on the band transport model, proposed by Kukhtarev et al. (Ferroelectrics, vol. 22, 949 (1979)). Assuming that the electron density only depends of x coordinate and taking a constant external electric field E in the same x coordinate we find that the electron density obeys a Nagumo's equation whose solution is soliton type.
Deosarkar, S. D.; Kalyankar, T. M.
2013-06-01
Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.
Turbulence attenuation by large neutrally buoyant particles
Cisse, Mamadou; Gibert, Mathieu; Bodenschatz, Eberhard; Bec, Jeremie
2015-01-01
Turbulence modulation by inertial-range-size, neutrally-buoyant particles is investigated experimentally in a von K\\'arm\\'an flow. Increasing the particle volume fraction $\\Phi_\\mathrm{v}$, maintaining constant impellers Reynolds number attenuates the fluid turbulence. The inertial-range energy transfer rate decreases as $\\propto\\Phi_\\mathrm{v}^{2/3}$, suggesting that only particles located on a surface affect the flow. Small-scale turbulent properties, such as structure functions or acceleration distribution, are unchanged. Finally, measurements hint at the existence of a transition between two different regimes occurring when the average distance between large particles is of the order of the thickness of their boundary layers.
Simulations of Buoyant Bubbles in Galaxy Clusters
Brüggen, M
2003-01-01
It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.
D. K. Narvilkar
1979-07-01
Full Text Available In the present paper, the equations of internal ballistics of composite charge consisting of N component charge with quadratic form are solved. Largange density approximation and hydrodynamic flow behaviour, have been assumed and the solutions are obtained for the composite charge for these assumptions.
D. K. Narvilkar
1977-10-01
Full Text Available This paper gives the solution of the equations of internal ballistics of a gun by taking the exact form of density of the propellent gases obtained on the basis of lagrange approximation. A general quadratic form functions is used.
Effect of current density on distribution coefficient of solute at solid-liquid interface
常国威; 王自东; 吴春京; 胡汉起
2003-01-01
When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interfaceenergy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between thedistribution of solute at solid-liquid interface and current density was established, and the effect of current on thedistribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and theradius of curvature at the dendritic tip was discussed. The results show that as the current density increases, thedistribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm2 , thelatter varies significantly.
Boutelier, D.; Cruden, A.; Saumur, B.
2016-05-01
Analogue models often require that materials with specific physical properties be engineered to satisfy scaling conditions. To achieve this goal we investigate the rheology of aqueous solutions of Natrosol 250 HH, a rheology modifier employed in various industries to thicken viscous solutions. We report the rheological properties as functions of the concentration and temperature and discuss the advantages and limitations of these materials in view of their use in analogue modelling experiments. The solutions are linear visco-elastic for low stresses (or strain-rates), becoming shear-thinning for larger stresses. For the typically slow analogue experiments of tectonics, the solutions can be considered linear visco-elastic with a Maxwell relaxation time much smaller than the characteristic observation time. This simplification is even more appropriate when the solutions are employed at temperatures higher than 20 °C, since the solutions then display a behaviour that is more viscous, less elastic at the same shear-rate, while the Newtonian viscosity reduces and the shear-rate limit between Newtonian and shear-thinning behaviours increases. The Newtonian viscosity is shown to increase non-linearly with concentration and decrease non-linearly with temperature. With concentrations between 0 and 3% and temperature between 20 and 40 °C, the viscosity varied between 10-1 and 4000 Pa s, while the density remained close to the density of water. Natrosol 250 HH thus offers the possibility to control the viscosity of a solution without significantly affecting the density, thereby facilitating the design and setup of analogue experiments.
A modeling of buoyant gas plume migration
Silin, D.; Patzek, T.; Benson, S.M.
2008-12-01
This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. Ideally, the injected greenhouse gas stays in the injection zone for a geologic time, eventually dissolves in the formation brine and remains trapped by mineralization. However, one of the potential problems associated with the geologic method of sequestration is that naturally present or inadvertently created conduits in the cap rock may result in a gas leakage from primary storage. Even in a supercritical state, the carbon dioxide viscosity and density are lower than those of the formation brine. Buoyancy tends to drive the leaked CO{sub 2} plume upward. Theoretical and experimental studies of buoyancy-driven supercritical CO{sub 2} flow, including estimation of time scales associated with plume evolution and migration, are critical for developing technology, monitoring policy, and regulations for safe carbon dioxide geologic sequestration. In this study, we obtain simple estimates of vertical plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. We describe buoyancy-driven countercurrent flow of two immiscible phases by a Buckley-Leverett type model. The model predicts that a plume of supercritical carbon dioxide in a homogeneous water-saturated porous medium does not migrate upward like a bubble in bulk water. Rather, it spreads upward until it reaches a seal or until it becomes immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration (Silin et al., 2007). In a layered reservoir, the simplified solution predicts a slower plume front propagation relative to a homogeneous formation with the same harmonic mean permeability. In contrast, the model yields much higher
Genetic search for an optimal power flow solution from a high density cluster
Amarnath, R.V. [Hi-Tech College of Engineering and Technology, Hyderabad (India); Ramana, N.V. [JNTU College of Engineering, Jagityala (India)
2008-07-01
This paper proposed a novel method to solve optimal power flow (OPF) problems. The method is based on a genetic algorithm (GA) search from a High Density Cluster (GAHDC). The algorithm of the proposed method includes 3 stages, notably (1) a suboptimal solution is obtained via a conventional analytical method, (2) a high density cluster, which consists of other suboptimal data points from the first stage, is formed using a density-based cluster algorithm, and (3) a genetic algorithm based search is carried out for the exact optimal solution from a low population sized, high density cluster. The final optimal solution thoroughly satisfies the well defined fitness function. A standard IEEE 30-bus test system was considered for the simulation study. Numerical results were presented and compared with the results of other approaches. It was concluded that although there is not much difference in numerical values, the proposed method has the advantage of minimal computational effort and reduced CPU time. As such, the method would be suitable for online applications such as the present Optimal Power Flow problem. 24 refs., 2 tabs., 4 figs.
Iterative solutions to the steady-state density matrix for optomechanical systems.
Nation, P D; Johansson, J R; Blencowe, M P; Rimberg, A J
2015-01-01
We present a sparse matrix permutation from graph theory that gives stable incomplete lower-upper preconditioners necessary for iterative solutions to the steady-state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse and is the only method found to be stable at large Hilbert space dimensions. This allows for steady-state solutions to otherwise intractable quantum optomechanical systems. PMID:25679739
Iterative solutions to the steady state density matrix for optomechanical systems
Nation, P D; Blencowe, M P; Rimberg, A J
2014-01-01
We present a sparse matrix permutation from graph theory that gives stable incomplete Lower-Upper (LU) preconditioners necessary for iterative solutions to the steady state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse, and is the only method found to be stable at large Hilbert space dimensions. This allows for steady state solutions to otherwise intractable quantum optomechanical systems.
The shape and behaviour of a horizontal buoyant jet adjacent to a surface
Burridge, Henry; Hunt, Gary
2015-11-01
We investigate the incompressible turbulent buoyant jet formed when fluid is steadily ejected horizontally from a circular source into a quiescent environment of uniform density. As our primary focus, we introduce a horizontal boundary. For sufficiently large source-boundary separations, the buoyant jet is `free' to rise under the action of the buoyancy force. For smaller source-boundary separations, the jet attaches and `clings' to the boundary before, further downstream, pulling away from the boundary. Based on measurements of saline jets in freshwater we deduce the conditions required for a jet to cling. We present data for the variation in volume flux, flow envelope and centreline for both `clinging' and `free' jets. For source Froude numbers fr0 >= 12 the data collapses when scaled, identifying universal behaviours for both clinging jets and for free jets. The support and funding from Dyson Technology Ltd is gratefully acknowledged.
Wake-driven dynamics of finite-sized buoyant spheres in turbulence
Mathai, Varghese; Brons, Jon; Sun, Chao; Lohse, Detlef
2015-01-01
Particles suspended in turbulent flows are affected by the turbulence, and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation on finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multi-physics based models that account for particle wake effects for a faithful representation of buoyant sphere dynamics in turbulence.
Wake-Driven Dynamics of Finite-Sized Buoyant Spheres in Turbulence.
Mathai, Varghese; Prakash, Vivek N; Brons, Jon; Sun, Chao; Lohse, Detlef
2015-09-18
Particles suspended in turbulent flows are affected by the turbulence and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation of finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multiphysics based models that account for particle wake effects for a faithful representation of buoyant-sphere dynamics in turbulence. PMID:26430995
Buoyant Bubbles and the Disturbed Cool Core of Abell 133
Randall, Scott W.; Clarke, T.; Nulsen, P.; Owers, M.; Sarazin, C.; Forman, W.; Jones, C.; Murray, S.
2010-03-01
X-ray cavities, often filled with radio-emitting plasma, are routinely observed in the intracluster medium of clusters of galaxies. These cavities, or "bubbles", are evacuated by jets from central AGN and subsequently rise buoyantly, playing a vital role in the "AGN feedback" model now commonly evoked to explain the balance between heating and radiative cooling in cluster cores. As the bubbles rise, they can displace cool central gas, promoting mixing and the redistribution of metals. I will show a few examples of buoyant bubbles, then argue that the peculiar morphology of the Abell 133 is due to buoyant lifting of cool central gas by a radio-filled bubble.
无
2010-01-01
To analyze the effect of basic variable on failure probability in reliability analysis,a moment-independent importance measure of the basic random variable is proposed,and its properties are analyzed and verified.Based on this work,the importance measure of the basic variable on the failure probability is compared with that on the distribution density of the response.By use of the probability density evolution method,a solution is established to solve two importance measures,which can efficiently avoid the difficulty in solving the importance measures.Some numerical examples and engineering examples are used to demonstrate the proposed importance measure on the failure probability and that on the distribution density of the response.The results show that the proposed importance measure can effectively describe the effect of the basic variable on the failure probability from the distribution density of the basic variable.Additionally,the results show that the established solution on the probability density evolution is efficient for the importance measures.
Some Exact Self-Similar Solutions to a Density-Dependent Reaction-Diffusion Model
Ngamsaad, Waipot
2012-01-01
In this paper, we investigated a density-dependent reaction-diffusion equation, $u_t = (u^{m})_{xx} + u - u^{m}$. This equation is known as the extension of the Fisher or Kolmogoroff-Petrovsky-Piscounoff equation which is widely used in the population dynamics, combustion theory and plasma physics. By employing the suitable transformation, this equation was mapped to the anomalous diffusion equation where the nonlinear reaction term was eliminated. Due to its simpler form, some exact self-similar solutions with the compact support have been obtained. The solutions, evolving from an initial state, converge to the usual traveling wave at a certain transition time. Hence, it is quite clear the connection between self-similar solution and the traveling wave solution from these results. Moreover, the solutions were found in the manner that either propagates to the right or propagates to the left. Furthermore, the two solutions form a symmetric solution, expanding in both directions. The application on the spatiote...
Intravaia, F; Messina, Andrea
2003-01-01
An original method to exactly solve the non-Markovian Master Equation describing the interaction of a single harmonic oscillator with a quantum environment in the weak coupling limit is reported. By using a superoperatorial approach we succeed in deriving the operatorial solution for the density matrix of the system. Our method is independent of the physical properties of the environment. We show the usefulness of our solution deriving explicit expressions for the dissipative time evolution of some observables of physical interest for the system, such as, for example, its mean energy.
Li, Jinkai
2016-01-01
In this paper, we consider the initial-boundary value problem to the nonhomogeneous incompressible Navier-Stokes equations. Local strong solutions are established, for any initial data $(\\rho_0, u_0)\\in (W^{1,\\gamma} \\cap L^\\infty)\\times H_{0,\\sigma}^1$, with $\\gamma>1$, and if $\\gamma\\geq2$, then the strong solution is unique. The initial density is allowed to be nonnegative, and in particular, the initial vacuum is allowed. The assumption on the initial data is weaker than the previous wide...
CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR
Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...
On polynomial solutions to Fokker–Planck and sinked density evolution equations
We analytically solve for the time dependent solutions of various density evolution models. With specific forms of the diffusion, drift and sink coefficients, the eigenfunctions can be expressed in terms of hypergeometric functions. We obtain the relevant discrete and continuous spectra for the eigenfunctions. With non-zero sink terms the discrete spectra eigenfunctions are generalizations of well known orthogonal polynomials: the so-called associated-Laguerre, Bessel, Fisher–Snedecor and Romanovski functions. We use MacRobert’s proof to obtain closed form expressions for the continuous normalization of the Romanovski density function. Finally, we apply our results to obtain the analytical solutions associated with the Bertalanffy–Richards–Langevin equation. (paper)
Ohsaku, T; Yamaki, D; Yamaguchi, K
2002-01-01
For studying the group theoretical classification of the solutions of the density functional theory in relativistic framework, we propose quantum electrodynamical density-matrix functional theory (QED-DMFT). QED-DMFT gives the energy as a functional of a local one-body $4\\times4$ matrix $Q(x)\\equiv -$, where $\\psi$ and $\\bar{\\psi}$ are 4-component Dirac field and its Dirac conjugate, respectively. We examine some characters of QED-DMFT. After these preparations, by using Q(x), we classify the solutions of QED-DMFT under O(3) rotation, time reversal and spatial inversion. The behavior of Q(x) under nonrelativistic and ultrarelativistic limits are also presented. Finally, we give plans for several extensions and applications of QED-DMFT.
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Sosa Vazquez, Xochitl A.; Isborn, Christine M., E-mail: cisborn@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States)
2015-12-28
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.
The Multiphase Buoyant Plume Solution of the Dusty Gas Model
Cerminara, Matteo
2015-01-01
Starting from the balance equations of mass, momentum and energy we formulate an integral 1D model for a poly-disperse mixture injected in the atmosphere. We write all the equations, either in their most general formulation or in the more simplified, taking particular care in considering all the underlying hypothesis in order to make clear when it is possible and appropriate to use them. Moreover, we put all the equations in a non-dimensional form, making explicit all the dimensionless parameters that drive the dynamics of these phenomena. In particular, we find parameters to measure: the goodness of the Boussinesq approximation, the injected mass flow, the column stability and his eventual collapse, and the importance of the atmospheric stratification, the initial kinetic energy and the gravitational potential energy. We show that setting to zero some of these parameters, it is possible to recover some of the existing jet and plume models for single-phase flows. Moreover, we write a simplified set of equatio...
Polar-solvation classical density-functional theory for electrolyte aqueous solutions near a wall
Warshavsky, Vadim; Marucho, Marcelo
2016-04-01
A precise description of the structural and dielectric properties of liquid water is critical to understanding the physicochemical properties of solutes in electrolyte solutions. In this article, a mixture of ionic and dipolar hard spheres is considered to account for water crowding and polarization effects on ionic electrical double layers near a uniformly charged hard wall. As a unique feature, solvent hard spheres carrying a dipole at their centers were used to model water molecules at experimentally known concentration, molecule size, and dipolar moment. The equilibrium ionic and dipole density profiles of this electrolyte aqueous model were calculated using a polar-solvation classical density-functional theory (PSCDFT). These profiles were used to calculate the charge density distribution, water polarization, dielectric permittivity function, and mean electric potential profiles as well as differential capacitance, excess adsorptions, and wall-fluid surface tension. These results were compared with those corresponding to the pure dipolar model and unpolar primitive solvent model of electrolyte aqueous solutions to understand the role that water crowding and polarization effects play on the structural and thermodynamic properties of these systems. Overall, PSCDFT predictions are in agreement with available experimental data.
In this paper, we analyze two semiconductor optical amplifier (SOA) structures, traveling-wave and reflective, with the active region made of the bulk material. The model is based on the stationary traveling-wave equations for forward and backward propagating photon densities of the signal and the amplified spontaneous emission, along with the stationary carrier rate equation. We start by introducing linear approximation of the carrier density spatial distribution, which enables us to find solutions for the photon densities in a closed analytical form. An analytical approach ensures a low computational resource occupation and an easy analysis of the parameters influencing the SOA’s response. The comparison of the analytical and numerical results shows high agreement for a wide range of the input optical powers and bias currents. (paper)
An Experimental Investigation on Inclined Negatively Buoyant Jets
Raed Bashitialshaaer
2012-09-01
Full Text Available An experimental study was performed to investigate the behavior of inclined negatively buoyant jets. Such jets arise when brine is discharged from desalination plants. A turbulent jet with a specific salinity was discharged through a circular nozzle at an angle to the horizontal into a tank with fresh water and the spatial evolution of the jet was recorded. Four different initial jet parameters were changed, namely the nozzle diameter, the initial jet inclination, the jet density and the flow rate. Five geometric quantities describing the jet trajectory that are useful in the design of brine discharge systems were determined. Dimensional analysis demonstrated that the geometric jet quantities studied, if normalized with the jet exit diameter, could be related to the densimetric Froude number. Analysis of the collected data showed that this was the case for a Froude number less than 100, whereas for larger values of the Froude number the scatter in the data increased significantly. As has been observed in some previous investigations, the slope of the best-fit straight line through the data points was a function of the initial jet angle (θ, where the slope increased with θ for the maximum levels (Y_{m} studied, but had a more complex behavior for horizontal distances.
The Centaurus A Northern Middle Lobe as a Buoyant Bubble
Saxton, C J; Bicknell, G V; Saxton, Curtis J.; Sutherland, Ralph S.; Bicknell, Geoffrey V.
2001-01-01
We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment into the precursor radio lobe. Using the morphology of the lobe to date the beginning of its rise through the atmosphere of Centaurus A, we conclude that the bubble has been rising for approximately 140Myr. This time scale is consistent with that proposed by Quillen et al. (1993) for the settling of post-merger gas into the presently observed large scale disk in NGC 5128, suggesting a strong connection between the delayed re-establishment of radio emission and the merger of NGC 5128 with a small gas-rich galaxy. This suggests a connection, for radio galaxies in general, between mergers and the delayed onset of radio emission. In our model, the elongated X-...
Mass transport by buoyant bubbles in galaxy clusters
Pope, Edward C D; Pavlovski, Georgi; Bower, Richard G; Dotter, Aaron; Victoria, University of; Southampton, University of; Durham, University of
2010-01-01
We investigate the effect of three important processes by which AGN-blown bubbles transport material: drift, wake transport and entrainment. The first of these, drift, occurs because a buoyant bubble pushes aside the adjacent material, giving rise to a net upward displacement of the fluid behind the bubble. For a spherical bubble, the mass of upwardly displaced material is roughly equal to half the mass displaced by the bubble, and should be ~ 10^{7-9} solar masses depending on the local ICM and bubble parameters. We show that in classical cool core clusters, the upward displacement by drift may be a key process in explaining the presence of filaments behind bubbles. A bubble also carries a parcel of material in a region at its rear, known as the wake. The mass of the wake is comparable to the drift mass and increases the average density of the bubble, trapping it closer to the cluster centre and reducing the amount of heating it can do during its ascent. Moreover, material dropping out of the wake will also ...
Density and activity of perrhenic acid aqueous solutions at T = 298.15 K
Highlights: • Water activity and osmolality measurements on highly concentrated perrhenic acid binary solutions have been carried out. • The study led to a new expression of the stoichiometric activity coefficient γ±vs. m. • The parameters of the two most frequently referenced Pitzer and specific interaction theory models have been determined. • The partial molar volume has been calculated. • The density law of the binary solution as a function of its concentration has been determined. - Abstract: Published isopiestic molalities for aqueous HReO4 solutions at T = 298.15 K are completed. Binary data (variation of the osmotic coefficient and activity coefficient of the electrolyte in solution in the water) at T = 298.15 K for perrhenic acid HReO4 are determined by direct water activity and osmolality measurements. The variation of the osmotic coefficient of this acid in water is represented mathematically according to a model recommended by the National Institute of Standards and Technology and according to the specific interaction theory. The data are also used to evaluate the parameters of the standard three-parameters of Pitzer’s ion-interaction model, along with the parameters of Archer’s four-parameter extended ion-interaction model, to higher molalities than previously advised. Experimental thermodynamic data are well represented by these models. Density variations at T = 298.15 K are also established and used to express the activity coefficient values on both the molar and molal concentration scales
Soliton solutions of an improved quark mass density-dependent model at finite temperature
The improved quark mass density-dependent model (IQMDD) based on soliton bag model is studied at finite temperature. Applying the finite temperature field theory, the effective potential of the IQMDD model and the bag constant B(T) have been calculated at different temperatures. It is shown that there is a critical temperature TC≅110 MeV. We also calculate the soliton solutions of the IQMDD model at finite temperature. It turns out that when TC, there is a bag constant B(T) and the soliton solutions are stable. However, when T>TC the bag constant B(T)=0 and there is no soliton solution, therefore, the confinement of quarks are removed quickly
Highlights: • We study flow structure in highly buoyant jet with inflow. • Three-dimensional velocity field is measured by scanning stereo PIV. • We examine flow structure by three-dimensional POD analysis. • Magnitude and scale of velocity fluctuation in POD mode is discussed. • Role of cross-flow across longitudinal structure is reported. - Abstract: The flow characteristics and the structure of highly buoyant jet of low density fluid issuing into a stagnant surrounding of high density fluid is studied by scanning stereo PIV combined with proper orthogonal decomposition (POD) analysis. The experiment is carried out at Froude number of 0.3 and Reynolds number of 200, which satisfies the inflow condition due to the unstable density gradient near the nozzle exit. An increase in the maximum mean velocity occurs and the vertical velocity fluctuation is highly amplified near the nozzle exit, which suggests the influence of inflow due to the unstable density gradient. The POD analysis indicates that the vertical velocity fluctuation is the major source of fluctuating energy contributing to the development of the highly buoyant jet. The examination of the POD modes show that the longitudinal structure of the vertical velocity fluctuation is generated along the jet axis having the opposite sign of velocity fluctuation on both sides of the jet axis. The vertical scale of the POD mode decreases with increasing the mode number and results in the frequent appearance of cross-flow across the buoyant jet. The reconstruction flow from the POD modes indicates that the vortex structure is caused by the highly sheared layer between the upward and downward velocity and the inflow is induced by the vortex structure. The magnitude of the vortex structure seems to be weakened with an increase in the distance from the nozzle and the buoyant jet approaches to an asymptotic state in the further downstream
Peterson, Karen I.
2008-01-01
The experiment developed in this article addresses the concept of equipment calibration for reducing systematic error. It also suggests simple student-prepared sucrose solutions for which accurate densities are known, but not readily available to students. Densities are measured with simple glassware that has been calibrated using the density of…
Csörgö, T; Csanad, M
2007-01-01
A new class of accelerating, exact, explicit and simple solutions of relativistic hydrodynamics is presented. Since these new solutions yield a finite rapidity distribution, they lead to an advanced estimate of the initial energy density and life-time of high energy heavy ion reactions. Accelerating solutions are also given for spherical expansions in arbitrary number of spatial dimensions.
Mass transport by buoyant bubbles in galaxy clusters
Pope, Edward C. D.; Babul, Arif; Pavlovski, Georgi; Bower, Richard G.; Dotter, Aaron
2010-08-01
We investigate the effect of three important processes by which active galactic nuclei (AGN)-blown bubbles transport material: drift, wake transport and entrainment. The first of these, drift, occurs because a buoyant bubble pushes aside the adjacent material, giving rise to a net upward displacement of the fluid behind the bubble. For a spherical bubble, the mass of upwardly displaced material is roughly equal to half the mass displaced by the bubble and should be ~ 107-9 Msolar depending on the local intracluster medium (ICM) and bubble parameters. We show that in classical cool-core clusters, the upward displacement by drift may be a key process in explaining the presence of filaments behind bubbles. A bubble also carries a parcel of material in a region at its rear, known as the wake. The mass of the wake is comparable to the drift mass and increases the average density of the bubble, trapping it closer to the cluster centre and reducing the amount of heating it can do during its ascent. Moreover, material dropping out of the wake will also contribute to the trailing filaments. Mass transport by the bubble wake can effectively prevent the buildup of cool material in the central galaxy, even if AGN heating does not balance ICM cooling. Finally, we consider entrainment, the process by which ambient material is incorporated into the bubble. Studies of observed bubbles show that they subtend an opening angle much larger than predicted by simple adiabatic expansion. We show that bubbles that entrain ambient material as they rise will expand faster than the adiabatic prediction; however, the entrainment rate required to explain the observed opening angle is large enough that the density contrast between the bubble and its surroundings would disappear rapidly. We therefore conclude that entrainment is unlikely to be a dominant mass transport process. Additionally, this also suggests that the bubble surface is much more stable against instabilities that promote
A three-parameter equation, describing with a high accuracy the density and reduced (molar, specific) volumes (V) of individual substances and solutions in any aggregate state as the function of temperature and pressure, is suggested. By the equation differentiation analytic expressions for actual coefficient of isobaric thermal expansion and coefficient of isothermal compression of substances and solutions are obtained. The calculated and table values of the coefficients for water under atmospheric pressure and temperatures of 283-353K are compared. Applicability of the equation V(T, p) is illustrated using concrete examples, i.e. Th, U, Pu, uranium fluorides and nitrates, TBP and other substances, essential for the practice of extraction reprocessing of irradiated fuel and other processes of nuclear fuel cycle
Morrison, Benjamin C.; Borrero-Echeverry, Daniel
2015-11-01
Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH4SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water (ν ~ 1 . 6 cSt and ρ ~ 1 . 1 g/cc). We present an empirical model for predicting the refractive index of aqueous NH4SCN solutions as a function of temperature and NH4SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. This work was supported by the National Science Foundation (CBET-0853691) and by the James Borders Physics Student Fellowship at Reed College.
Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
Nelson, Nicholas J; Brun, A Sacha; Miesch, Mark S; Toomre, Juri
2012-01-01
Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much larger values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength o...
Densities and solubilities of Glycylglycine and Glycyl-L-Alanine in Aqueous Electrolyte Solutions
Breil, Martin Peter; Mollerup, Jørgen; Rudolph, E. Susanne J.;
2004-01-01
higher salt concentrations in NaCl and Na2SO4, and in (NH4)(2)SO4 the solubility is almost constant. The densities of the solutions have been determined experimentally, and the volume expansions by dissolving salt and dipeptide in water have been calculated. (C) 2003 Elsevier B.V. All rights reserved....... 1.74 and 4.78 mol/kg of water, respectively. The solubility of glycylglycine in salt solutions of NaCl, Na2SO4, and (NH4)(2)SO4 show a moderate salting-in effect. The solubility of glycyl-L-alanine show a minor or no salting-in effect at low salt concentrations and a moderate salting-out effect at......Solubilities of glycylglycine and glycyl-L-alanine in aqueous electrolyte solutions containing 0-6 molal NaCl, 0-1 molal Na2SO4, and 0-1 molal (NH4)(2)SO4, have been determined experimentally at 298.15 K and atmospheric pressure. The solubility of glycylglycine and glycyl-L-alanine in pure water is...
Thompson, Alex J; Eniola-Adefeso, Omolola
2015-07-01
For vascular-targeting carrier (VTC) systems to be effective, carriers must be able to localize and adhere to the vascular wall at the target site. Research suggests that neutrally buoyant nanoparticles are limited by their inability to localize to the endothelium, making them sub-optimal as carriers. This study examines whether particle density can be exploited to improve the targeting (localization and adhesion) efficiency of nanospheres to the vasculature. Silica spheres with 500 nm diameter, which have a density roughly twice that of blood, exhibit improved adhesion to inflamed endothelium in an in vitro model of human vasculature compared to neutrally buoyant polystyrene spheres of the same size. Silica spheres also display better near-wall localization in the presence of red blood cells than they do in pure buffer, likely resulting in the observed improvement in adhesion. Titania spheres (4 times more dense than blood) adhere at levels higher than polystyrene, but only in conditions when gravity or centrifugal force acts in the direction of adhesion. In light of the wide array of materials proposed for use as carrier systems for drug delivery and diagnostics, particle density may be a useful tool for improving the targeting of diseased tissues. PMID:25870170
On the near field behavior of inclined negatively buoyant jets
Besalduch L.A.
2014-03-01
Full Text Available We have performed an experimental campaign in the laboratory on the near field behavior of inclined negatively buoyant jets, issuing from a circular sharp-edged orifice, in order to investigate the symmetry properties of this phenomenon. The velocity measurements were obtained via a non intrusive image analysis technique, namely Feature Tracking Velocimetry. We present here both first and second order statistics, showing that the asymmetry of inclined negatively buoyant jets cannot be considered only a far field feature of this phenomenon, as it arises very close to the release point.
Horizontal H 2-air turbulent buoyant jet resulting from hydrogen leakage
El-Amin, Mohamed
2012-02-01
The current article is devoted to introducing mathematical and physical analyses with numerical investigation of a buoyant jet resulting from hydrogen leakage in air from a horizontal round source. H 2-air jet is an example of the non-Boussinesq buoyant jet in which a low-density gas jet is injected/leak into a high-density ambient. The density of the mixture is a function of the concentration only, the binary gas mixture is assumed to be of a linear mixing type and the rate of entrainment is assumed to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. On the other hand, the local rate of entrainment consists of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The top-hat profile assumption is used to obtain the mean centerline velocity, width, density and concentration of the H 2-air horizontal jet in addition to kinematic relations which govern the jet trajectories. A set of ordinary differential equations is obtained and solved numerically using Runge-Kutta method. In the second step, the mean axial velocity, mean concentration and mean density of the jet are obtained based on Gaussian model. Finally, several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), turbulent eddy viscosity and turbulent eddy diffusivity, are obtained by solving the governing partial differential equations. Additionally, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Accuracy of wind tunnel modeling of buoyant plume rise around buildings
Dispersion modeling of buoyant exhausts in the vicinity of building clusters, such as from boilers, incinerators, and diesel generators, is often conducted using wind tunnel modeling. The receptors of interest are usually air intakes within the building clusters. Exact wind tunnel modeling of buoyant plume rise requires stack exhaust Froude number scaling between model simulations and the full scale, along with undistorted exit densities and ratios of exit velocity to approach wind speed. The Froude number requirements constrains the air speed in the tunnel to be lower than 0.5 m/s for typical geometric scale reductions. Such low air speeds can make the air flow around the buildings Reynolds number dependent, an undesirable result. Distortions of exhaust density ratios and of exit diameters have been suggested in the past to maintain higher tunnel speeds. Davidson has presented an analytical plume rise equation which combines the 1/3 and 2/3 exponent laws for momentum-dominated and buoyancy-dominated plume rise. The analytical model was reported to compare well with water flume data. Davidson also recommends that the equation can be used to predict the errors in modeled plume rise when various wind tunnel modeling schemes are used to avoid the Froude number modeling requirement. This paper extends the work of Davidson by comparing the analytical equation to several wind tunnel and field plume rise databases. The analytical equation is then used to examine wind tunnel modeling schemes for two types of buoyant exhausts commonly modeled near buildings: emergency diesel generators and boilers
Suspension of buoyant drops at low and moderate areal fractions is studied at non-zero Reynolds numbers in simple shear flow. The flow is studied as a function of the Capillary number, the Reynolds number, the Froude number and the density ratio. It is found that the effective viscosity decreases with Capillary number. The normal stress difference increases with Capillary number. The effective viscosity and normal stress difference also depend on the Reynolds number. At a relatively low area fraction (ϕ = 0.22 ) the normal stress difference decreases with Froude number and becomes negative at large Froude numbers. At a moderate areal fraction (ϕ = 0.44 ) the behavior of the suspension is similar to the relatively low areal fraction, except that the normal stress difference is always positive. Also, the flow weakly depends on the Froude number at moderate areal fraction. The density distribution of buoyant drops across the channel is non-uniform. (paper)
Goodarzi, S; Mortazavi, S, E-mail: s.goodarzi@me.iut.ac.ir, E-mail: saeedm@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)
2013-08-01
Suspension of buoyant drops at low and moderate areal fractions is studied at non-zero Reynolds numbers in simple shear flow. The flow is studied as a function of the Capillary number, the Reynolds number, the Froude number and the density ratio. It is found that the effective viscosity decreases with Capillary number. The normal stress difference increases with Capillary number. The effective viscosity and normal stress difference also depend on the Reynolds number. At a relatively low area fraction (#Greek Phi Symbol# = 0.22 ) the normal stress difference decreases with Froude number and becomes negative at large Froude numbers. At a moderate areal fraction (#Greek Phi Symbol# = 0.44 ) the behavior of the suspension is similar to the relatively low areal fraction, except that the normal stress difference is always positive. Also, the flow weakly depends on the Froude number at moderate areal fraction. The density distribution of buoyant drops across the channel is non-uniform. (paper)
Chen Mingtao
2011-01-01
Full Text Available Abstract This article is concerned with global strong solutions of the micro-polar, compressible flow with density-dependent viscosity coefficients in one-dimensional bounded intervals. The important point in this article is that the initial density may vanish in an open subset.
We study the pressureless Navier–Stokes–Poisson equations with density-dependent viscosity. With the extension of the blowup solutions for the Euler–Poisson equations, the analytical blowup solutions, in radial symmetry, in RN (N ≥ 2) are constructed
Jacob, Shery; Nair, Anroop B; Patil, Pandurang N
2011-01-01
An inert hydrophobic buoyant coated–core was developed as floating drug delivery system (FDDS) for sustained release of cisapride using direct compression technology. Core contained low density, porous ethyl cellulose, which was coated with an impermeable, insoluble hydrophobic coating polymer such as rosin. It was further seal coated with low viscosity hydroxypropyl methyl cellulose (HPMC E15) to minimize moisture permeation and better adhesion with an outer drug layer. It was found that sta...
Current-sheet formation near a hyperbolic magnetic neutral line in the MHD model is investigated. In this model, the magnetic field lines are swept by the plasma flow toward the X-point. Effects of density-variation of the plasma are included. An exact analytic solution is given. This solution exhibits a finite-time singularity that is peculiar to the variable-density plasma case and this finite-time singularity occurs when there is a plasma density build-up near the magnetic neutral line
MSW Solutions to the Solar Neutrino Problem in Presence of Noisy Matter Density Fluctuations
Bykov, A A; Peña-Garay, C; Popov, V Yu; Semikoz, V B
2000-01-01
We study the effect of random matter density fluctuations in the sun on resonant neutrino conversion in matter by solving numerically the evolution equation for the neutrino system including the full effect of the random matter density fluctuations of given amplitude and correlation length. In order to establish the possible effect on the MSW solutions to the solar neutrino problem we perform a global analysis of all the existing observables including the measured total rates as well as the Super-Kamiokande measurement on the time dependence of the event rates during the day and night and the recoil electron energy spectrum. We find the effects of random noise to be larger for small mixing angles and they are mostly important for correlation lengths in the range few 100 km $\\lesssim L_0\\lesssim$ few 1000 km. They can be understood as due to a parametric resonance occuring when the phase acquired by the oscillating neutrino state on one fluctuation length L_0 is a multiple of 2$\\pi$. We find that this resonant...
PREDICTION OF CHARACTERISTICS FOR VERTICAL ROUND NEGATIVE BUOYANT JETS IN HOMOGENEOUS AMBIENT
无
2001-01-01
The k-ε turbulence model is used to establish a mathematicalmodel of a vertical round jet with negative buoyancy in a static homogeneous ambient. The hybrid finite analytic method, with a non-uniform staggered grid, is used to calculate the whole flow field. The variations of centerline velocity, density and turbulent kinetic energy along the axial line for a given exit densimetric Froude number are found to converge to single curves under the unified scaling law derived by Chen and Rodi. The profiles of mean velocities, mean density difference and the half-width of negative buoyant jets for velocity and density are given. The calculation confirmed that the maximum height of rise is proportional to M03/4B0-1/2 ,where M0 and B0 are the momentum flux and the buoyancy flux at the source, respectively.
Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
Nelson, Nicholas J.; Brown, Benjamin P.; Sacha Brun, A.; Miesch, Mark S.; Toomre, Juri
2014-02-01
Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much higher values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength of the axisymmetric toroidal field is not a good predictor of the production rate for buoyant loops or the amount of magnetic flux in the loops that are produced.
Surface Intermediate Zone of Submerged Turbulent Buoyant Jet in Current
Chen, H. B.; Larsen, Torben
1995-01-01
This paper deals with the intermediate zone between the jet and plume stages of a submerged buoyant discharge from sea outfall in current. The stability criteria, plume width and height after the intermediate zone and the dilution within the intermediate region have been studied theoretically...
46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section 160.010-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-5 Buoyant apparatus...
Small dense LDL is more susceptible to glycation than more buoyant LDL in Type 2 diabetes.
Younis, Nahla N; Soran, Handrean; Pemberton, Philip; Charlton-Menys, Valentine; Elseweidy, Mohamed M; Durrington, Paul N
2013-03-01
Glycation of apoB (apolipoprotein B) of LDL (low-density lipoprotein) increases its atherogenicity. Concentrations of both serum glyc-apoB (glycated apoB) and SD-LDL (small dense LDL) (syn LDL3; D=1.044-1.063 g/ml) are increased in diabetes and are closely correlated. We studied whether SD-LDL is more susceptible to glycation in vitro than more buoyant LDL in statin- and non-statin-treated Type 2 diabetes mellitus. Serum SD-LDL apoB and glyc-apoB on statins was 20±2 (means±S.D.) and 3.6±0.41 compared with 47±3 and 5.89±0.68 mg/dl in those not receiving statins (P<0.001 and <0.01, respectively). There was a dose-dependent increase in glycation on incubation of LDL subfractions with glucose, which was accompanied by an increase in LPO (lipid peroxide) and electrophoretic mobility and a decrease in free amino groups. SD-LDL was more susceptible to these changes than more buoyant LDL. Both SD-LDL and more buoyant LDL from statin-treated patients were less susceptible to glycation. There were fewer free amino groups on LDL subfractions from statin-treated patients, which may contribute to this resistance. In conclusion, greater susceptibility of SD-LDL to glycation is likely to contribute to the raised levels of circulating glyc-apoB in diabetes. Statins are associated with lower levels of both SD-LDL and glyc-apoB. PMID:22985435
Near field characteristics of buoyant helium plumes
Kuchimanchi K Bharadwaj; Debopam Das; Pavan K Sharma
2015-05-01
Puffing and entrainment characteristics of helium plumes emanating out into ambient air from a circular orifice are investigated in the present study. Velocity and density fields are measured across a diametric plane using Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) respectively in phase resolved manner. Experiments are performed in Froude numbers range 0.2–0.4 and for Reynolds numbers 58–248. Puffing frequency measurements reveal that the plume puffing frequencies are insensitive to the plume exit conditions, since the instability is buoyancy driven. The frequencies obtained in the present case are in agreement with frequencies obtained by Cetegen & Kasper (1996) for plumes originating from circular nozzles of various L/D ratios. Velocity and density measurements reveal that toroidal vortex formed during a puffing cycle entrains ambient air as it traverses downstream and this periodic engulfment governs the entrainment mechanism in pulsating plumes. The obtained velocity and density fields are used to calculate mass entrainment rates. It is revealed that though the flow is unsteady, the contribution of unsteady term in mass conservation to entrainment is negligible, and it becomes zero over a puff cycle. Finally, an empirical relation for variation of mass entrainment with height has been proposed, in which the non-dimensional mass entrainment is found to follow a power law with the non-dimensional height.
Simulations of Buoyant Plumes in Solar Prominences
Hurlburt, Neal
2012-01-01
Observations of solar prominences reveal a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long ``threads'' and dark ``bubbles'' that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. We present results of various configurations and discuss the nonlinear behavior of the resulting dynamics.
Simulations of Buoyant Plumes in Solar Prominences
Hurlburt, N.; Berger, T.
2012-08-01
Observations of solar prominences reveal a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long "threads" and dark "bubbles" that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. We present results of various configurations and discuss the nonlinear behavior of the resulting dynamics.
Integral models for buoyant plume calculations
Integral models have been proven to be successful and inexpensive tools for the solution of a variety of jet-type environmental flow problems. In the Sonderforschungsbereich 80, a family of integral models has been developed for several applications as, e.g., the mixing of waste water and cooling water plumes discharged into lakes and coastal waters for the dispersion of pollutants and heat emitted by chimneys, cooling towers and urban heat islands into the atmosphere. The common features of these integral models are discussed. Finally, the quality of model results is demonstrated by comparing predictions with experimental data. (orig.)
Chen Xiao-Gang; Guo Zhi-Ping; Song Jin-Bao
2008-01-01
In the present paper,the random interfacial waves in N-layer density-stratified fluids moving at different steady uniform speeds are researched by using an expansion technique,and the second-order asymptotic solutions of the random displacements of the density interfaces and the associated velocity potentials in N-layer fluid are presented based on the small amplitude wave theory.The obtained results indicate that the wave-wave second-order nonlinear interactions of the wave components and the second-order nonlinear interactions between the waves and currents are described.As expected,the solutions include those derived by Chen(2006)as a special case where the steady uniform currents of the N-layer fluids are taken as zero,and the solutions also reduce to those obtained by Song(2005)for second-order solutions for random interracial waves with steady uniform currents if N=2.
Electronic state density distributions in TiC-VC and TiC-TiN solid solutions
Using the earlier obtained calculation results of the TiC, VC and TiN band structure the state density histograms of the TiCsub(x)Nsub(1-x) and Tisub(x)Vsub(1-x)C solid solutions are constructed. The different character of the state density variation at the Fermi level with different solid solutions of the TiC-VC and TiC-TiN systems is established, and nonapplicability of the ''hard band'' model for description of their physical properties is shown
Beauty of lotus is more than skin deep: highly buoyant superhydrophobic films.
Choi, Yuri; Brugarolas, Teresa; Kang, Sung-Min; Park, Bum Jun; Kim, Byeong-Su; Lee, Chang-Soo; Lee, Daeyeon
2014-05-28
We develop highly buoyant superhydrophobic films that mimic the three-dimensional structure of lotus leaves. The high buoyancy of these structure stems from mechanically robust bubbles that significantly reduce the density of the superhydrophobic films. These highly buoyant superhydrophobic films stay afloat on water surface while carrying a load that is more than 200 times their own weight. In addition to imparting high buoyancy, the incorporation of robust hydrophilic bubbles enables the formation of free-standing structures that mimic the water-collection properties of Namib Desert beetle. We believe the incorporation of robust bubbles is a general method that opens up numerous possibilities in imparting high buoyancy to different structures that needs to stay afloat on water surfaces and can potentially be used for the fabrication of lightweight materials. (Image on the upper left reproduced with permission from Yong, J.; Yang, Q.; Chen, F.; Zhang, D.; Du, G.; Si, J.; Yun, F.; Hou, X. A Bioinspired Planar Superhydrophobic Microboat. J. Micromech. Microeng. 2014, 24, 035006). PMID:24801001
Wang, Weike; Xu, Xin
2016-06-01
In this paper, the Cauchy problem for the nonisentropic Euler-Maxwell system with a nonconstant background density is studied. The global existence of classical solution is constructed in three space dimensions provided the initial perturbation is sufficiently small. The proof is mainly based on classical energy estimate and the techniques of symmetrizer. And the time decay of the solution is also established by combining the decay estimate of the Green's function with some time-weighted estimate.
Analysis of a turbulent buoyant confined jet modeled using realizable k-ε model
El-Amin, Mohamed
2010-06-13
Through this paper, analyses of components of the unheated/heated turbulent confined jet are introduced and some models to describe them are developed. Turbulence realizable k-ε model is used to model the turbulence of this problem. Numerical simulations of 2D axisymmetric vertical hot water confined jet into a cylindrical tank have been done. Solutions are obtained for unsteady flow while velocity, pressure, temperature and turbulence distributions inside the water tank are analyzed. For seeking verification, an experiment was conducted for measuring of the temperature of the same system, and comparison between the measured and simulated temperature shows a good agreement. Using the simulated results, some models are developed to describe axial velocity, centerline velocity, radial velocity, dynamic pressure, mass flux, momentum flux and buoyancy flux for both unheated (non-buoyant) and heated (buoyant) jet. Finally, the dynamics of the heated jet in terms of the plume function which is a universal quantity and the source parameter are studied and therefore the maximum velocity can be predicted theoretically. © 2010 Springer-Verlag.
Chen Xiao-Gang; Guo Zhi-Ping; Song Jin-Bao; He Xiao-Dong; Guo Jun-Ming; Bao Shu-Hong; Cui Wei
2009-01-01
Interfacial internal waves in a three-layer density-stratified fluid are investigated using a singular perturbation method, and third-order asymptotic solutions of the velocity potentials and third-order Stokes wave solutions of the associated elevations of the interracial waves are presented based on the small amplitude wave theory. As expected, the third-order solutions describe the third-order nonlinear modification and the third-order nonlinear interactions between the interracial waves. The wave velocity depends on not only the wave number and the depth of each layer but also on the wave amplitude.
In this paper, we investigate the analytical solutions of the compressible Navier-Stokes equations with dependent-density viscosity. By using the characteristic method, we successfully obtain a class of drifting solutions with elliptic symmetry for the Navier-Stokes model wherein the velocity components are governed by a generalized Emden dynamical system. In particular, when the viscosity variables are taken the same as Yuen [M. W. Yuen, “Analytical solutions to the Navier-Stokes equations,” J. Math. Phys. 49, 113102 (2008)], our solutions constitute a generalization of that obtained by Yuen. Interestingly, numerical simulations show that the analytical solutions can be used to explain the drifting phenomena of the propagation wave like Tsunamis in oceans
An, Hongli, E-mail: kaixinguoan@163.com [College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Yuen, Manwai, E-mail: nevetsyuen@hotmail.com [Department of Mathematics and Information Technology, The Hong Kong Institute of Education, 10 Po Ling Road, Tai Po, New Territories (Hong Kong)
2014-05-15
In this paper, we investigate the analytical solutions of the compressible Navier-Stokes equations with dependent-density viscosity. By using the characteristic method, we successfully obtain a class of drifting solutions with elliptic symmetry for the Navier-Stokes model wherein the velocity components are governed by a generalized Emden dynamical system. In particular, when the viscosity variables are taken the same as Yuen [M. W. Yuen, “Analytical solutions to the Navier-Stokes equations,” J. Math. Phys. 49, 113102 (2008)], our solutions constitute a generalization of that obtained by Yuen. Interestingly, numerical simulations show that the analytical solutions can be used to explain the drifting phenomena of the propagation wave like Tsunamis in oceans.
Sawale, R. T.; Deosarkar, S. D.; Kalyankar, T. M.
2015-07-01
Density ( ρ), viscosity ( η) and refractive index ( n D) of an antiemetic drug metoclopramide (4-amino-5-chloro- N-(2-(diethylamino)ethyl)-2-methoxybenzamide hydrochloride) solutions containing amino acids (glycine, D-alanine, L-cystine and L-histidine) were measured in the concentration range 0.01-0.17 mol/dm3 at 303.15 K. The apparent molar volume (φv) of this drug in aqueous amino acid solutions was calculated from the density data and fitted to the Massons relation, and the partial molar volume φ{v/0} of the drug was determined graphically. The partial molar volumes of transfer (Δtrφ{v/0}) of drug at infinite dilution from pure water to aqueous amino acid solutions were calculated and interpreted in terms of different interactions between the drug and amino acids.
Video Image Analysis of Turbulent Buoyant Jets Using a Novel Laboratory Apparatus
Crone, T. J.; Colgan, R. E.; Ferencevych, P. G.
2012-12-01
Turbulent buoyant jets play an important role in the transport of heat and mass in a variety of environmental settings on Earth. Naturally occurring examples include the discharges from high-temperature seafloor hydrothermal vents and from some types of subaerial volcanic eruptions. Anthropogenic examples include flows from industrial smokestacks and the flow from the damaged well after the Deepwater Horizon oil leak of 2010. Motivated by a desire to find non-invasive methods for measuring the volumetric flow rates of turbulent buoyant jets, we have constructed a laboratory apparatus that can generate these types of flows with easily adjustable nozzle velocities and fluid densities. The jet fluid comprises a variable mixture of nitrogen and carbon dioxide gas, which can be injected at any angle with respect to the vertical into the quiescent surrounding air. To make the flow visible we seed the jet fluid with a water fog generated by an array of piezoelectric diaphragms oscillating at ultrasonic frequencies. The system can generate jets that have initial densities ranging from approximately 2-48% greater than the ambient air. We obtain independent estimates of the volumetric flow rates using well-calibrated rotameters, and collect video image sequences for analysis at frame rates up to 120 frames per second using a machine vision camera. We are using this apparatus to investigate several outstanding problems related to the physics of these flows and their analysis using video imagery. First, we are working to better constrain several theoretical parameters that describe the trajectory of these flows when their initial velocities are not parallel to the buoyancy force. The ultimate goal of this effort is to develop well-calibrated methods for establishing volumetric flow rates using trajectory analysis. Second, we are working to refine optical plume velocimetry (OPV), a non-invasive technique for estimating flow rates using temporal cross-correlation of image
Long-term tracking of neutrally buoyant tracer particles in two-dimensional fluid flows
Pervez, M. S.; Solomon, T. H.
1994-07-01
An experimental technique has been developed to produce and to track neutrally buoyant particles in a two-dimensional fluid flow. The key aspect of the technique is the ability to track particles for extended intervals (over an hour), which is essential for quantitative studies of transport and mixing. The approach is composed of two stages. In the first stage, digital image processing hardware partially processes the images, reducing the data rate to 50 kbyte/s (typically) and allowing several hours of data to be stored on a conventional computer disk. In the second stage, programs extract particle trajectories from the reduced data. The approach is tested in an experiment on planetary-type flows in a rotating annulus. In an appendix, a technique is discussed for fabricating wax or crayon particles with arbitrary density.
The stability of buoyant bubbles in the atmospheres of galaxy clusters
Kaiser, C R; Pope, E C D; Fangohr, H
2005-01-01
The buoyant rise of hot plasma bubbles inflated by AGN outflows in galaxy clusters can heat the cluster gas and thereby compensate radiative energy losses of this material. Numerical simulations of this effect often show the complete disruption of the bubbles followed by the mixing of the bubble material with the surrounding cluster gas due to fluid instabilities on the bubble surface. This prediction is inconsistent with the observations of apparently coherent bubble structures in clusters. We derive a general description in the linear regime of the growth of instabilities on the surface between two fluids under the influence of a gravitational field, viscosity, surface tension provided by a magnetic field and relative motion of the two fluids with respect to each other. We demonstrate that Kelvin-Helmholtz instabilities are always suppressed, if the fluids are viscous. They are also suppressed in the inviscid case for fluids of very different mass densities. We show that the effects of shear viscosity as we...
Measurements of Accelerations of Large Neutrally-buoyant Particles in Intense Turbulence
Brown, Rachel D; Voth, Greg A
2009-01-01
We measure acceleration statistics of neutrally buoyant spherical particles with diameter 0.4 , clearly resolve the transition from the tracer like behavior of small particles to the much smaller accelerations of large particles. For d>5 eta, decreases with diameter as d^{-2/3} in agreement with inertial range scaling arguments. A model relating to the pressure structure functions matches the transition from small to large particle behavior if the particles respond to pressure differences over (1.7 +- 0.3) d. A model relating to the fluid acceleration averaged over the particle diameter predicts the transition with no free parameters, but does not show clean inertial range scaling in the size range studied. Consistent with earlier work, we find that the scaled acceleration probability density function shows very little dependence on particle size.
Experiments on the fragmentation of a buoyant liquid volume in another liquid
Landeau, Maylis; Olson, Peter
2014-01-01
We present experiments on the instability and fragmentation of volumes of heavier liquid released into lighter immiscible liquids. We focus on the regime defined by small Ohnesorge numbers, density ratios of order one, and variable Weber numbers. The observed stages in the fragmentation process include deformation of the released fluid by either Rayleigh-Taylor instability or vortex ring roll-up and destabilization, formation of filamentary structures, capillary instability, and drop formation. At low and intermediate Weber numbers, a wide variety of fragmentation regimes is identified. Those regimes depend on early deformations, which mainly result from a competition between the growth of Rayleigh-Taylor instabilities and the roll-up of a vortex ring. At high Weber numbers, turbulent vortex ring formation is observed. We have adapted the standard theory of turbulent entrainment to buoyant vortex rings with initial momentum. We find consistency between this theory and our experiments, indicating that the conc...
Effect of Side Wind on the Directional Stability and Aerodynamics of a Hybrid Buoyant Aircraft
Haque Anwar U
2016-01-01
Full Text Available Directional stability characteristics explain the capabilities of a hybrid buoyant aircraft’s performance against the side wind, which induces flow separation that is chaotic in nature and may lead to oscillations of the aerodynamic surfaces. A numerical study is carried out to estimate the effect of side wind. The boundary conditions for the computational domain are set to velocity inlet and pressure outlet. Due to the incompressible flow at the cruise velocity, the density is taken to be constant. For these steady state simulations, the time is discretized in first order implicit and the SIMPLE scheme is employed for pressure velocity coupling alongwith k-ω SST model. Based on the results obtained so far, it is concluded that voluminous hybrid lifting fuselage is the major cause of directional.
Ion-water wires in imidazolium-based ionic liquid/water solutions induce unique trends in density.
Ghoshdastidar, Debostuti; Senapati, Sanjib
2016-03-28
Ionic liquid/water binary mixtures are rapidly gaining popularity as solvents for dissolution of cellulose, nucleobases, and other poorly water-soluble biomolecules. Hence, several studies have focused on measuring the thermophysical properties of these versatile mixtures. Among these, 1-ethyl-3-methylimidazolium ([emim]) cation-based ILs containing different anions exhibit unique density behaviours upon addition of water. While [emim][acetate]/water binary mixtures display an unusual rise in density with the addition of low-to-moderate amounts of water, those containing the [trifluoroacetate] ([Tfa]) anion display a sluggish decrease in density. The density of [emim][tetrafluoroborate] ([emim][BF4])/water mixtures, on the other hand, declines rapidly in close accordance with the experimental reports. Here, we unravel the structural basis underlying this unique density behavior of [emim]-based IL/water mixtures using all-atom molecular dynamics (MD) simulations. The results revealed that the distinct nature of anion-water hydrogen bonded networks in the three systems was a key in modulating the observed unique density behaviour. Vast expanses of uninterrupted anion-water-anion H-bonded stretches, denoted here as anion-water wires, induced significant structuring in [emim][Ac]/water mixtures that resulted in the density rise. Conversely, the presence of intermittent large water clusters disintegrated the anion-water wires in [emim][Tfa]/water and [emim][BF4]/water mixtures to cause a monotonic density decrease. The differential nanostructuring affected the dynamics of the solutions proportionately, with the H-bond making and breaking dynamics found to be greatly retarded in [emim][Ac]/water mixtures, while it exhibited a faster relaxation in the other two binary solutions. PMID:26911708
Experimental insights on the development of buoyant plumes injected into a porous media
Lyu, Xiaoying; Woods, Andrew W.
2016-01-01
We describe a series of new laboratory experiments which examine the rise of a two-dimensional buoyancy-driven plume of freshwater through a porous layer initially saturated with aqueous saline solution. Measurements show that the plume head accounts for a constant fraction of about 0.7 of the buoyancy supplied at the source and that it grows as it rises through the porous layer. However, the morphology of the plume head becomes increasingly complex as the ratio of the injection speed to the buoyancy rise speed increases, with the fluid spreading laterally and developing localized buoyant fingers which intermingle with the ambient fluid. Behind the plume head, a tail of nearly constant width develops providing a pathway from the source to the plume head. These starting plume dynamics may be relevant for buoyancy-driven contaminant dispersal and also for the convection which develops during CO2 sequestration as CO2 dissolves into aquifer water.
Magnetic Cycles and Buoyant Loops in Convective Dynamos
Nelson, Nicholas J.
2013-01-01
Solar-type stars display a rich spectrum of magnetic activity. Seeking to explore convective dynamo action in solar-like stars with the anelastic spherical harmonic (ASH) code, we have carried out a series of global 3-D MHD simulations. Here we report on the dynamo mechanisms realized in a series of numerical models of a sun-like star which explore the effects of decreasing diffusion. While these models nominally rotate at three times the current solar rate (3Ω), the results may be more widely applicable as both these simulations and the solar convection zone achieve similar levels of rotationally constrained convection. Previous simulations at 3Ω have shown that convective dynamos can build persistent wreath-like structures of strong toroidal magnetic field in the convection zone (Brown et al. 2010). Here we find that magnetic reversals and cycles can be realized at 3Ω by decreasing the explicit diffusion and thereby making the resolved flows more turbulent. In these more turbulent models, diffusive processes no longer play a primary role in the key dynamical balances which maintain differential rotation and generate the global-scale wreaths. With reduced resistive diffusion of magnetic fields, the axisymmetric poloidal fields can no longer achieve a steady state and this triggers reversals in global magnetic polarity. Additionally, the enhanced levels of turbulence lead to greater intermittency in the toroidal magnetic wreaths, which can create buoyant magnetic loops that rise from the deep interior to the upper regions of our simulated domain. Turbulence-enabled magnetic buoyancy in our most turbulent simulation yields large numbers of buoyant loops, enabling us to examine the distribution of the characteristics of buoyant magnetic loops, such as twist, tilt angle, and relation to axisymmetric fields. These models provide a pathway towards linking convective dynamo models and the emergence of magnetic flux in the Sun and sun-like stars.
Densities of L-Glutamic Acid HCl Drug in Aqueous NaCl and KCl Solutions at Different Temperatures
Ryshetti, Suresh; Raghuram, Noothi; Rani, Emmadi Jayanthi; Tangeda, Savitha Jyostna
2016-04-01
Densities (ρ ) of (0.01 to 0.07) {mol}{\\cdot } {kg}^{-1} L-Glutamic acid HCl (L-HCl) drug in water, and in aqueous NaCl and KCl (0.5 and 1.0) {mol}{\\cdot } {kg}^{-1} solutions have been reported as a function of temperature at T = (298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure. The accurate density (ρ ) values are used to estimate the various parameters such as the apparent molar volume (V_{2,{\\upphi }}), the partial molar volume (V2^{∞}), the isobaric thermal expansion coefficient (α 2), the partial molar expansion (E2^{∞}), and Hepler's constant (partial 2V2^{∞}/partial T2)P. The Cosphere overlap model is used to understand the solute-solvent interactions in a ternary mixture (L-HCl drug + NaCl or KCl + water). Hepler's constant (partial 2V2^{∞}/partial T2)_P is utilized to interpret the structure-making or -breaking ability of L-HCl drug in aqueous NaCl and KCl solutions, and the results are inferred that L-HCl drug acts as a structure maker, i.e., kosmotrope in aqueous NaCl solutions and performs as a structure breaker, i.e., chaotrope in aqueous KCl solutions.
Iasiello, Marcello; Vafai, Kambiz; Andreozzi, Assunta; Bianco, Nicola
2016-01-25
An analytical solution for Low-Density Lipoprotein transport through an arterial wall under hyperthermia conditions is established in this work. A four-layer model is used to characterize the arterial wall. Transport governing equations are obtained as a combination between Staverman-Kedem-Katchalsky membrane equations and volume-averaged porous media equations. Temperature and solute transport fields are coupled by means of Ludwig-Soret effect. Results are in excellent agreement with numerical and analytical literature data under isothermal conditions, and with numerical literature data for the hyperthermia case. Effects of hypertension combined with hyperthermia, are also analyzed in this work. PMID:26806687
Teodorescu, Razvan [Los Alamos National Laboratory; Lee, S - Y [MONTREAL, CANADA; Wiegmann, P [UNIV OF CHICAGO
2008-01-01
We investigate the hydrodynamics of a Hele-Shaw flow as the free boundary evolves from smooth initial conditions into a generic cusp singularity (of local geometry type x{sup 3} {approx} y{sup 2}), and then into a density shock wave. This novel solution preserves the integrability of the dynamics and, unlike all the weak solutions proposed previously, is not underdetermined. The evolution of the shock is such that the net vorticity remains zero, as before the critical time, and the shock can be interpreted as a singular line distribution of fluid deficit.
Dynamics of finite size neutrally buoyant particles in isotropic turbulence
Elhimer, M; Jean, A; Praud, O; Bazile, R; Marchal, M; Couteau, G, E-mail: elhimer@imft.fr [Universite de Toulouse, INPT, UPS, IMFT - Institut de Mecanique des Fluides de Toulouse, Allee Camille Soula, F-31400 Toulouse (France); CNRS, IMFT, F-31400 Toulouse (France)
2011-12-22
The dynamics of neutrally buoyant particles suspended in a turbulent flow is investigated experimentally, with particles having diameters larger than the Kolmogorov length scale. To that purpose, a turbulence generator have been constructed and the resulting flow characterized. The fluid was then seeded with polystyrene particles of diameter about 1 mm and their velocity measured separately and simultaneously with the surrounding fluid. Comparison of the velocities statistics between the two phases shows no appreciable discrepancy. However, simultaneous velocity measurement shows that particles may move in different direction from the underlying flow.
Self-concentrating buoyant glass microbubbles for high sensitivity immunoassays.
Juang, Duane S; Hsu, Chia-Hsien
2016-02-01
Here, we report the novel application of a material with self-concentrating properties for enhancing the sensitivity of immunoassays. Termed as glass microbubbles, they are antibody functionalized buoyant hollow glass microspheres that simultaneously float and concentrate into a dense monolayer when dispensed in a liquid droplet. This self-concentrating charactaristic of the microbubbles allow for autonomous signal localization, which translates to a higher sensitivity compared to other microparticle-based immunoassays. We then demonstrated a "microbubble array" platform consisting of the glass microbubbles floating in a microfluidic liquid hemisphere array for performing multiplex immunoassays. PMID:26620967
Buoyant triacylglycerol-filled green algae and methods therefor
Goodenough, Ursula; Goodson, Carrie
2015-04-14
Cultures of Chlamydomonas are disclosed comprising greater than 340 mg/l triacylglycerols (TAG). The cultures can include buoyant Chlamydomonas. Methods of forming the cultures are also disclosed. In some embodiments, these methods comprise providing Chlamydomonas growing in log phase in a first culture medium comprising a nitrogen source and acetate, replacing the first culture medium with a second medium comprising acetate but no nitrogen source, and subsequently supplementing the second medium with additional acetate. In some embodiments, a culture can comprise at least 1,300 mg/l triacyglycerols. In some embodiments, cultures can be used to produce a biofuel such as biodiesel.
Entrainment and mixing in vertical buoyant light-gas plumes
A simple model is developed to determine the entrainment coefficient and the spread of a light-gas plume in a quiescent atmosphere. Experiments performed with low-velocity saltwater/freshwater and helium-in-air jets indicate that buoyant gas plumes spread significantly faster than thermal plumes. The calculated effluent concentrations are in excellent agreement with those measured when an entrainment coefficient of 0.15 is used in the plume equations. This is significantly higher than the entrainment coefficients of 0.075 to 0.093 reported for thermal plumes
A study has been made of anodic dissolution of rhenium using potentiodynamic dissolution curves for a rotating disk electrode made of vacuum-melted rhenium. Dissolution of rhenium at 23 deg starts at potentials of approximately + 0.2 V for alkaline solutions (NaOH) and at potentials of approximately +0.1 V for neutral solutions (2N NaCl and NaNO3). No limitation of the process rate is observed during dissolution in neutral solutions unlike dissolution in alkalies for which a limiting current strength is characteristic
Luo, Tao; Xin, Zhouping; Zeng, Huihui
2015-01-01
The nonlinear asymptotic stability of Lane-Emden solutions is proved in this paper for spherically symmetric motions of viscous gaseous stars with the density dependent shear and bulk viscosities which vanish at the vacuum, when the adiabatic exponent $\\gamma$ lies in the stability regime $(4/3, 2)$, by establishing the global-in-time regularity uniformly up to the vacuum boundary for the vacuum free boundary problem of the compressible Navier-Stokes-Poisson systems with spherical symmetry, w...
Evolution of the buoyant bubbles in M87
Churazov, E; Kaiser, C R; Böhringer, H; Forman, W R
2000-01-01
The morphology of the X-ray and radio emitting features in the central 50 kpc region around the galaxy M87 strongly suggests that buoyant bubbles of cosmic rays (inflated by an earlier nuclear active phase of the galaxy) are slowly rising through the cooling gas. In the absence of strong surface tension, an intrinsic property of initially spherical bubbles is their transformation into tori as they rise through an external medium. Such structures can be identified in the radio images of the halo of M87. During their rise the bubbles uplift relatively cool X-ray emitting ambient gas from the central regions of the cooling flow to larger distances. This gas is colder than the ambient gas and has a higher volume emissivity. As a result, rising "radio" bubbles may be trailed by elongated X-ray features as indeed is observed in M87. We performed simple hydrodynamical simulations in order to qualitatively illustrate the evolution of the buoyant bubbles in the M87 environment.
Steady thermocapillary-buoyant convection in a shallow annular pool.Part 2: Two immiscible fluids
You-Rong Li; Shuang-Cheng Wang; Chun-Mei Wu
2011-01-01
This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios e → 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide (lower layer) and boron oxide (upper layer),the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.
Sebestíková, L
2013-09-01
Buoyantly unstable 3D chemical fronts were seen traveling through an iodate-arsenous acid reaction solution. The experiments were performed in channel reactors with rectangular cross sections, where the top of the reaction solution was in contact with air. A concave or convex meniscus was pinned to reactor lateral walls. Influence of the meniscus shape on front development was investigated. For the concave meniscus, an asymptotic shape of fronts holding negative curvature was observed. On the other hand, fronts propagating in the solution with the convex meniscus kept only positive curvature. Those fronts were also a bit faster than fronts propagating in the solution with the concave meniscus. A relation between the meniscus shape, flow distribution, velocity, and shape is discussed. PMID:24125360
Non-Boussinesq turbulent buoyant jet resulting from hydrogen leakage in air
El-Amin, M.F. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-09-15
This paper is devoted to introduce a numerical investigation of a vertical axisymmetric non-Boussinesq buoyant jet resulting from hydrogen leakage in air as an example of injecting a low-density gas jet into high-density ambient. As the domain temperature is assumed to be constant and therefore the density of the mixture is a function of the concentration only, the binary gas mixture is assumed to be of a linear mixing type. Also, it is assumed that the rate of entrainment to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. On the other hand, the local rate of entrainment may be considered to be consisted from two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. Firstly, the integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some non-dimensional transformations known as similarity transformations. The given ordinary differential system is integrated numerically and the mean centerline mass fraction, jet width and mean centerline velocity are obtained. In the second step, the mean axial velocity, mean concentration and mean density of the jet are obtained. Finally in the third step of this article, several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), turbulent eddy viscosity and turbulent eddy diffusivity, are obtained. In addition, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. (author)
46 CFR 131.865 - Inflatable liferafts and inflatable buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Inflatable liferafts and inflatable buoyant apparatus. 131.865 Section 131.865 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.865 Inflatable liferafts and inflatable buoyant apparatus....
46 CFR 160.010-4 - General requirements for buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false General requirements for buoyant apparatus. 160.010-4 Section 160.010-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-4 General requirements...
A series of approximations are usually made in deriving integral model equations for the dispersion of a round turbulent buoyant jet into a stagnant neutrally-stratified ambient fluid. The magnitudes of differences in model predictions caused by making four of these approximations are calculated as a function of the initial densimetric Froude number and the initial relative density difference. The four approximations studied are (1) the Boussinesq approximation, (2) the use of a common Gaussian width for both mean axial velocity and mean temperature (or concentration) excess, (3) the neglect of fluctuation-correlation terms, and (4) the assumption of a linear relationship between excess density and excess temperature (or concentration). The four approximations are studied singly and then cumulatively as the predictions of the two models, one with and one without all approximations, are compared to seven low Froude number data cases. Results show that the Boussinesq approximation produces percentage differences in predictions which are about half of the initial relative density difference expressed in percentage. Use of a common Gaussian width for velocity and temperature produces differences from 6% to 30% depending on the entrainment assumption used. Fluctuation correlation effects rarely exceed 8%. Lastly, at Froude numbers below about 10 the correct nonlinear equation of state must often be used for heated waste jets to acheive accurate results, and the correct air equation of state may also be needed for low Froude number heated air jets, depending on the initial diameter and velocity
Optimal unambiguous state discrimination of two density matrices: A second class of exact solutions
L"utkenhaus, P R N
2007-01-01
We consider the Unambiguous State Discrimination (USD) of two mixed quantum states. We study the rank and the spectrum of the elements of an optimal USD measurement. This naturally leads to a partial fourth reduction theorem. This theorem shows that either the failure probability equals its overall lower bound given in term of the fidelity or a two dimensional subspace can be split off from the original Hilbert space. We then use this partial reduction theorem to derive the optimal solution for any two Geometrically Uniform (GU) states $\\rho_0$ and $\\rho_1=U\\rho_0 U^\\dagger$, $U^2={\\openone}$, in a four dimensional Hilbert space. This represents a second class of analytical solutions for USD problems that cannot be reduced to some pure state cases. We apply our result to answer two questions that are relevant in implementations of the Bennett and Brassard 1984 quantum key distribution protocol using weak coherent states.
Turbulent buoyant confined jet with variable source temperature
El-Amin, M F; Sun, S
2013-01-01
In this work, experimental and numerical investigations are considered for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-epsilon turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear variation that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during whole time. Numerical exp...
Flow behaviour of negatively buoyant jets in immiscible ambient fluid
Geyer, A. [CIMNE International Center for Numerical Models in Engineering, Barcelona (Spain); CSIC, Institute of Earth Sciences Jaume Almera, Barcelona (Spain); Phillips, J.C. [University of Bristol, Department of Earth Sciences, Bristol (United Kingdom); Mier-Torrecilla, M.; Idelsohn, S.R.; Onate, E. [CIMNE International Center for Numerical Models in Engineering, Barcelona (Spain)
2012-01-15
In this paper we investigate experimentally the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid. Experiments are carried out by injecting a jet of dyed fresh water through a nozzle in the base of a cylindrical tank containing rapeseed oil. The fountain inlet flow rate and nozzle diameter were varied to cover a wide range of Richardson Ri (8 x 10{sup -4}
Numerical simulations of buoyant reactive jets with sidewall effects
ZHANG Heping; JIANG Xi; WANG Wei; YANG Yun; XU Liang; FAN Weicheng
2004-01-01
The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient environment in a corner configuration with sidewall boundaries. Simulation results are presented for two cases with different jet nozzle geometries: a corner-round reactive jet and a corner-square reactive jet with the same cross-sectional area on the nozzle plane. Buoyancy-induced large vortical structures evolve spatially in the flow field and transition to turbulence occurs downstream. Calculation of the mean flow properties shows that entrainment of the corner-round jet is stronger than that of the corner-square jet due to the stronger vortex deformation in the corner-round case.
NATO Advanced Study Institute on Buoyant Convection in Geophysical Flows
Fedorovich, E; Viegas, D; Wyngaard, J
1998-01-01
Studies of convection in geophysical flows constitute an advanced and rapidly developing area of research that is relevant to problems of the natural environment. During the last decade, significant progress has been achieved in the field as a result of both experimental studies and numerical modelling. This led to the principal revision of the widely held view on buoyancy-driven turbulent flows comprising an organised mean component with superimposed chaotic turbulence. An intermediate type of motion, represented by coherent structures, has been found to play a key role in geophysical boundary layers and in larger scale atmospheric and hydrospheric circulations driven by buoyant forcing. New aspects of the interaction between convective motions and rotation have recently been discovered and investigated. Extensive experimental data have also been collected on the role of convection in cloud dynamics and microphysics. New theoretical concepts and approaches have been outlined regarding scaling and parameteriz...
Sampling and analysis of particles from buoyant hydrothermal plumes
Mottl, Michael J.
The objective of our studies has been to identify the chemical processes that occur in the buoyant part of hydrothermal plumes and to evaluate their role in determining the ultimate fate of the hydrothermal input to the oceans. Our first such effort is described by Mottl and McConachy [1990]. Because the buoyant plume is a small feature that contains very large physical and chemical gradients, we have sampled it from manned submersibles. We have used two different samplers, both manufactured by General Oceanics in Miami: the Go-Flo bottle and the Chopstick sampler. Four Go-Flo bottles of 1.7 L capacity can readily be mounted on most submersibles, vertically and in a forward position in sight of the pilot's viewport and video cameras, without interfering with other operations on a dive. On Alvin they have typically been mounted on the outside starboard edge of the basket. On Turtle they were mounted on the outside edge of the port manipulator. We chose Go-Flo rather than Niskin bottles because the latter are prone to spillage when the rods attached to the end caps are bumped against an object such as the seafloor, as often happens on a submersible dive. Go-Flo bottles are also more easily rigged for pressure filtration than are Niskins. The main disadvantage of Go-Flo bottles vs. Niskins for this application is the internal silicone rubber ring that holds the ball valves in place on each end of the Go-Flo. This ring tends to trap large particles that are then difficult to dislodge and collect. The rings are also difficult to clean between dives.
A mechanism capable to provide a natural solution to two major cosmological problems, i.e. the cosmic acceleration and the coincidence problem, is proposed. A specific brane-bulk energy exchange mechanism produces a total dark pressure, arising when adding all normal to the brane negative pressures in the interior of galactic core black holes. This astrophysically produced negative dark pressure explains cosmic acceleration and why the dark energy today is of the same order to the matter density for a wide range of the involved parameters. An exciting result of the analysis is that the recent rise of the galactic core black hole mass density causes the recent passage from cosmic deceleration to acceleration. Finally, it is worth mentioning that this work corrects a wide spread fallacy among brane cosmologists, i.e. that escaping gravitons result in positive dark pressure. (orig.)
Highlights: ► Density of amino acid salt and amine amino acid salt. ► Viscosity of amino acid salt and amine amino acid salt. ► Henry’s law constant/N2O solubility of amino acid salt and amine amino acid salt. ► Schumpe model. Correlations for density, viscosity, and N2O solubility. - Abstract: Physicochemical properties of aqueous amino acid salt (AAS), potassium salt of sarcosine (KSAR) and aqueous amine amino acid salt (AAAS), 3-(methylamino)propylamine/sarcosine (SARMAPA) have been studied. Densities of KSAR were measured for sarcosine mole fraction 0.02 to 0.25 for temperature range 298.15 K to 353.15 K, the viscosities were measured for 0.02 to 0.10 mole fraction sarcosine (293.15 K to 343.15 K) while the N2O solubilities were measured from 0.02 to 0.10 mole fraction sarcosine solutions (298.15 K to 363.15 K). Densities of SARMAPA were measured for sarcosine mole fraction 0.02 to 0.23 for temperature range (298.15 K to 353.15 K), viscosities were measured for 0.02 to 0.16 mole fraction sarcosine (293.15 K to 343.15 K) while the N2O solubilities were measured from 0.02 to 0.16 mole fraction sarcosine solutions (298.15 K to 343.15 K). Experimental results were correlated well with empirical correlations and N2O solubility results for KSAR were predicted adequately by a Schumpe model. The solubilities of N2O in AAS and AAAS are significantly lower than values for amines. The solubilities vary as: amine > AAAS > AAS.
Tiilikainen, J; Bosund, V; Mattila, M; Hakkarainen, T; Sormunen, J; Lipsanen, H [Micro and Nanosciences Laboratory, Helsinki University of Technology, Micronova, PO Box 3500, FI-02015 TKK (Finland)
2007-07-21
Nonunique solutions of the x-ray reflectivity (XRR) curve fitting problem were studied by modelling layer structures with neural networks and designing a fitness function to handle the nonidealities of measurements. Modelled atomic-layer-deposited aluminium oxide film structures were used in the simulations to calculate XRR curves based on Parratt's formalism. This approach reduced the dimensionality of the parameter space and allowed the use of fitness landscapes in the study of nonunique solutions. Fitness landscapes, where the height in a map represents the fitness value as a function of the process parameters, revealed tracks where the local fitness optima lie. The tracks were projected on the physical parameter space thus allowing the construction of the crosserror equation between weakly determined parameters, i.e. between the mass density and the surface roughness of a layer. The equation gives the minimum error for the other parameters which is a consequence of the nonuniqueness of the solution if noise is present. Furthermore, the existence of a possible unique solution in a certain parameter range was found to be dependent on the layer thickness and the signal-to-noise ratio.
Nonunique solutions of the x-ray reflectivity (XRR) curve fitting problem were studied by modelling layer structures with neural networks and designing a fitness function to handle the nonidealities of measurements. Modelled atomic-layer-deposited aluminium oxide film structures were used in the simulations to calculate XRR curves based on Parratt's formalism. This approach reduced the dimensionality of the parameter space and allowed the use of fitness landscapes in the study of nonunique solutions. Fitness landscapes, where the height in a map represents the fitness value as a function of the process parameters, revealed tracks where the local fitness optima lie. The tracks were projected on the physical parameter space thus allowing the construction of the crosserror equation between weakly determined parameters, i.e. between the mass density and the surface roughness of a layer. The equation gives the minimum error for the other parameters which is a consequence of the nonuniqueness of the solution if noise is present. Furthermore, the existence of a possible unique solution in a certain parameter range was found to be dependent on the layer thickness and the signal-to-noise ratio
The study on density change of carbon dioxide seawater solution at high pressure and low temperature
It has been widely considered that the global warming, induced by the increasing concentration of carbon dioxide and other greenhouse gases in the atmosphere, is an environmental task affecting the world economic development. In order to mitigate the concentration of CO2 in the atmosphere, the sequestration of carbon dioxide into the ocean had been investigated theoretically and experimentally over the last 10 years. In addition to ocean dynamics, ocean geological, and biological information on large space and long time scales, the physical-chemistry properties of seawater-carbon dioxide system at high pressure (P>5.0 MPa) and lower temperature (274.15 K3, which is approximately same with that of carbon dioxide freshwater solution, the slope of which is 0.275 g/cm3
The investigation of the scattering of lower-hybrid waves by density fluctuations arising from drift waves in tokamaks is distinguished by the presence in the wave equation of a large, random, derivative-coupling term. The propagation of the lower-hybrid waves is well represented by a radiative transfer equation when the scale size of the density fluctuations is small compared to the overall plasma size. The radiative transfer equation is solved in two limits: first, the forward scattering limit, where the scale size of density fluctuations is large compared to the lower-hybrid perpendicular wavelength, and second, the large-angle scattering limit, where this inequality is reversed. The most important features of these solutions are well represented by analytical formulas derived by simple arguments. Based on conventional estimates for density fluctuations arising from drift waves and a parabolic density profile, the optical depth tau for scattering through a significant angle, is given by tauroughly-equal(2/N2/sub parallel/) (#betta#/sub p/i0/#betta#)2 (m/sub e/c2/2T/sub i/)/sup 1/2/ [c/α(Ω/sub i/Ω/sub e/)/sup 1/2/ ], where #betta#/sub p/i0 is the central ion plasma frequency and T/sub i/ denotes the ion temperature near the edge of the plasma. Most of the scattering occurs near the surface. The transmission through the scattering region scales as tau-1 and the emerging intensity has an angular spectrum proportional to cos theta, where sin theta = k/sub perpendicular/xB/sub p//(k/sub perpendicular/B/sub p/), and B/sub p/ is the poloidal field
Studies of a roll-front uranium deposit in Shirley Basin Wyoming indicate that preliminary evaluation of the reserve potential of an ore body is possible with less drilling than currently practiced in industry. Estimating ore reserves from sparse drilling is difficult because most reserve calculation techniques do not give the accuracy of the estimate. A study of several deposits with a variety of drilling densities shows that geostatistics consistently provides a method of assessing the accuracy of an ore reserve estimate. Geostatistics provides the geologist with an additional descriptive technique - one which is valuable in the economic assessment of a uranium deposit. Closely spaced drilling on past properties provides both geological and geometric insight into the occurrence of uranium in roll-front type deposits. Just as the geological insight assists in locating new ore bodies and siting preferential drill locations, the geometric insight can be applied mathematically to evaluate the accuracy of a new ore reserve estimate. By expressing the geometry in numerical terms, geostatistics extracts important geological characteristics and uses this information to aid in describing the unknown characteristics of a property. (author)
Dutta, Urmi; Baruah, Amiya; Mandal, Nibir
2016-04-01
Diapiric structure owing to gravity instabilities, triggered by density inversion in the rock sequences, is a unique geodynamic manifestation. High-density layers that rest upon low-density layers tend to sink, forcing the latter to squeeze up in the form of domal shapes, called buoyant diapirs. Using two-layer viscous model experiments, we investigated the effects of source-layer tilt (β) in controlling the ascent behaviour of buoyant diapirs initiated by a Rayleigh-Taylor instability. Results from our laboratory experiments, performed with a buoyant viscous layer (PDMS; density: 965.0 kg/m3) underlying a denser fluid (water; density: 998.2 kg/m3) suggest that the diapir shape is highly sensitive to β. The results suggest that diapirs growing from a tilted source layer ascend with contrasting lateral spreading rates in the up and down slope directions, resulting in axi-asymmetric geometry. Conversely, diapirs initiated from a horizontal source layer always maintain axi- symmetric shape as they grow. Interestingly, diapir heads retain a circular outline on the horizontal top surface irrespective of their degree of symmetry. However, for the axi-asymmetric cases, the upwelling axis is shifted more in the up-slope direction, i.e. away from the centre of this circular geometry. We show a spectrum of the axi-symmetric to -asymmetric geometrical transitions as a function of the source-layer tilt (β). For large β (> 4o), the diapirs become unstable, and their stems undergo a continuous drift in the upslope direction during their vertical growth. Whilst, several studies have shown the development of axi-asymmetric diapirs, the underlain flow kinematics in the viscous layers as a function of source layer tilt leading to such shape transition remains unclear. With this objective we ran computational fluid dynamic (CFD) simulations, by employing the volume of fluid (VOF) method, to investigate the role of underlying dynamics for axi-asymmetric diapiric growth. This study
Energy density of marine pelagic fish eggs
Riis-Vestergaard, J.
2002-01-01
Analysis of the literature on pelagic fish eggs enabled generalizations to be made of their energy densities, because the property of being buoyant in sea water appears to constrain the proximate composition of the eggs and thus to minimize interspecific variation. An energy density of 1.34 J mul...
Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames
Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.
1997-01-01
Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient
Factors affecting the density of Brassica napus seeds
Young, L.; Jalink, H.; Denkert, R.; Reaney , M
2006-01-01
Brassica napus seed is composed of low density oil (0.92 g.cm(-3)) and higher density solids (1.3-1.45 g.cm(-3)). Seed buoyant density may potentially be used to determine seed oil content and to separate seeds with different oil contents, however, we have found that seeds with the lowest buoyant density had lower than expected oil contents. It is proposed that the low oil content observed in the lowest density seed is a function of air gaps or pockets within the seed coat with sufficient vol...
Highly buoyant bent-over plumes in a boundary layer
Tohidi, Ali; Kaye, Nigel B.
2016-04-01
Highly buoyant plumes, such as wildfire plumes, in low to moderate wind speeds have initial trajectories that are steeper than many industrial waste plumes. They will rise further into the atmosphere before bending significantly. In such cases the plume's trajectory will be influenced by the vertical variation in horizontal velocity of the atmospheric boundary layer. This paper examined the behavior of a plume in an unstratified environment with a power-law ambient velocity profile. Examination of previously published experimental measurements of plume trajectory show that inclusion of the boundary layer velocity profile in the plume model often provides better predictions of the plume trajectory compared to algebraic expressions developed for uniform flow plumes. However, there are many cases in which uniform velocity profile algebraic expressions are as good as boundary layer models. It is shown that it is only important to model the role of the atmospheric boundary layer velocity profile in cases where either the momentum length (square root of source momentum flux divided by the reference wind speed) or buoyancy length (buoyancy flux divided by the reference wind speed cubed) is significantly greater than the plume release height within the boundary layer. This criteria is rarely met with industrial waste plumes, but it is important in modeling wildfire plumes.
Role of buoyant flame dynamics in wildfire spread.
Finney, Mark A; Cohen, Jack D; Forthofer, Jason M; McAllister, Sara S; Gollner, Michael J; Gorham, Daniel J; Saito, Kozo; Akafuah, Nelson K; Adam, Brittany A; English, Justin D
2015-08-11
Large wildfires of increasing frequency and severity threaten local populations and natural resources and contribute carbon emissions into the earth-climate system. Although wildfires have been researched and modeled for decades, no verifiable physical theory of spread is available to form the basis for the precise predictions needed to manage fires more effectively and reduce their environmental, economic, ecological, and climate impacts. Here, we report new experiments conducted at multiple scales that appear to reveal how wildfire spread derives from the tight coupling between flame dynamics induced by buoyancy and fine-particle response to convection. Convective cooling of the fine-sized fuel particles in wildland vegetation is observed to efficiently offset heating by thermal radiation until convective heating by contact with flames and hot gasses occurs. The structure and intermittency of flames that ignite fuel particles were found to correlate with instabilities induced by the strong buoyancy of the flame zone itself. Discovery that ignition in wildfires is critically dependent on nonsteady flame convection governed by buoyant and inertial interaction advances both theory and the physical basis for practical modeling. PMID:26183227
Buoyant dispersal of CO2 during geological storage
Hesse, M. A.; Woods, A. W.
2010-01-01
Carbon capture and storage is currently the only technology that may allow significant reductions in CO2 emissions from large point sources. Seismic images of geological CO2 storage show the rise of CO2 is influenced by horizontal shales. The buoyant CO2 spreads beneath impermeable barriers until a gap allows its upward migration. The large number and small scale of these barriers makes the prediction of the CO2 migration path and hence the magnitude of CO2 trapping very challenging. We show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events. This approach allows the analysis of two-dimensional plume dispersal from a horizontal injection well. We show that the plume spreads laterally with height y above the source according to (y/h)1/2 L, where L is the width of the shales and h is their vertical separation. The fluid volume below successive shale layers, and therefore the magnitude of trapped CO2, increase as (y/h)5/4 above the source, so that every additional layer of barriers traps more CO2 than the one below. Upscaling small scale flow barriers by reducing the vertical permeability, common in numerical simulations of CO2 storage, does not capture the dispersion and trapping of the CO2 plume by the flow barriers.
Buoyant Magnetic Flux Ropes and Convection: Evolution Prior to Emergence
Dorch, S. B. F.
2003-10-01
We have performed detailed numerical 3-d simulations of the interaction of buoyantly ascending twisted magnetic flux ropes and solar-like stratified convection (with surface cells similar to solar supergranules in size). Results are presented for three different cases -- corresponding to different amounts of initial field line twist -- that represents fundamentally different types of instabilities: the magnetic Rayleigh-Taylor instability in which case the flux rope disrupts and network patches are formed at surface cell boundaries; the kink instability that has been proposed as a mechanism for forming tightly packed δ-type spots; a stable flux rope where neither of the former instabilities arise, and the behavior of which is similar to classical text book flux tubes, except from a flux-loss due to the advective action of the convective flows. The simulations thus support the idea that the magnetic flux observed at the surface in bipolar regions are smaller, ceteris paribus, than that of the dynamo generated flux ropes near the bottom of the convection zone. Please note that this material is also available as an online htmladdnormallink{web-talk}{http://www.astro.su.se/ dorch/talks/01_CS12/}
The vertical distribution of buoyant plastics at sea
J. Reisser
2014-11-01
Full Text Available Millimeter-sized plastics are numerically abundant and widespread across the world's ocean surface. These buoyant macroscopic particles can be mixed within the upper water column due to turbulent transport. Models indicate that the largest decrease in their concentration occurs within the first few meters of water, where subsurface observations are very scarce. By using a new type of multi-level trawl at 12 sites within the North Atlantic accumulation zone, we measured concentrations and physical properties of plastics from the air–seawater interface to a depth of 5 m, at 0.5 m intervals. Our results show that plastic concentrations drop exponentially with water depth, but decay rates decrease with increasing Beaufort scale. Furthermore, smaller pieces presented lower rise velocities and were more susceptible to vertical transport. This resulted in higher depth decays of plastic mass concentration (mg m−3 than numerical concentration (pieces m−3. Further multi-level sampling of plastics will improve our ability to predict at-sea plastic load, size distribution, drifting pattern, and impact on marine species and habitats.
Entrainment and mixing in vertical buoyant light-gas plumes
Hydrogen has great potential as a future fuel because of its nearly pollution-free combustion. However, it is highly diffusive and can easily leak through joints, cracks and defective valves if care is not taken. Accidental release of hydrogen into surrounding air and its subsequent mixing are of concern in evaluating the safe transport of hydrogen in buildings through piping. Hydrogen release into air is of importance in nuclear reactor safety analysis also. During certain postulated accidents in nuclear reactors, hydrogen may be produced by high temperature metal-steam reactions and released into the containment building. A simple model is developed to determine the entrainment coefficient and the spread of a light-gas plume in a quiescent atmosphere. Experiments performed with low velocity salt water/fresh-water and helium-in-air jets indicate that buoyant gas plumes spread significantly faster than thermal plumes. The calculated effluent concentrations are in excellent agreement with those measured when an entrainment coefficient of 0.15 is used in the plume equations. This is significantly higher than the entrainment coefficients of 0.075 to 0.093 reported for thermal plumes
Baluja, Shipra; Vaishnani, K. P.
2013-08-01
Density, ultrasonic velocity and viscosity of some Schiff bases of 4-aminophenol have been measured in dimethyl sulfoxide solutions over a wide range of concentration at 308.15 K. From these experimental data, some acoustical parameters have been evaluated, which helps in understanding the molecular interactions occurring in these solutions.
NUMERICAL STUDY ON THE STABILITY AND MIXING OF VERTICAL ROUNE BUOYANT JET IN SHALLOW WATER
曾玉红; 槐文信
2005-01-01
The k-epsilon model was applied to establish the mathematical model of vertical round buoyant jet discharging into confined depth, and it was solved using the Hybrid Finite Analytic Method ( HFAM ). The numerical predictions demonstrate two generic flow patterns for different jet discharge and environmental parameters: ( i ) a stable buoyant flow discharge with the mixed fluid leaving the near-field warm in a surface warm water layer;( ii ) an unstable buoyant flow discharge with recirculation and re-entrainment of warm water in the near field. Furthermore, the mixing characters of vertical round buoyant jet were numerically predicted. Both the stability criterion and numerical predictions of bulk dilutions are in excellent agreement with Lee and Jirka ' s experiments and theory.
The Melt Segregation During Ascent of Buoyant Diapirs in Subduction Zones
Zhang, N.; Behn, M. D.; Parmentier, E. M.; Kincaid, C. R.
2014-12-01
Cold, low-density diapirs arising from hydrated mantle and/or subducted sediments on the top of subducting slabs may transport key chemical signatures from the slab to the shallow source region for arc magmas. These chemical signatures are strongly influenced by melting of this buoyant material during its ascent. However, to date there have been relatively few quantitative models to constrain melting and melt segregation in an ascending diapir, as well as the induced geochemical signature. Here, we use a two-phase Darcy-Stokes-energy model to investigate thermal evolution, melting, and melt segregation in buoyant diapirs as they ascend through the mantle wedge. Using a simplified 2-D axi-symmetric circular geometry we investigate diapir evolution in three scenarios with increasing complexity. First, we consider a case without melting in which the thermal evolution of the diapir is controlled solely by thermal diffusion during ascent. Our results show that for most cases (e.g., diapir radius ≤ 3.7 km and diapir generation depths of ~ 75 km) thermal diffusion times are smaller than the ascent time—implying that the diapir will thermal equilibrate with the mantle wedge. Secondly, we parameterize melting within the diapir, but without melt segregation, and add the effect of latent heat to the thermal evolution of the diapir. Latent heat significantly buffers heating of the diapir. For the diapir with radius ~3.7 km, the heating from the outside is slowed down ~30%. Finally, we include melt segregation within the diapir in the model. Melting initiates at the boundaries of the diapir as the cold interior warms in response to thermal equilibration with the hot mantle wedge. This forms a high porosity, high permeability rim around the margin of the diapir. As the diapir continues to warm and ascend, new melts migrate into this rim and are focused upward, accumulating at the top of the diapir. The rim thus acts like an annulus melt channel isolating the central part of
Guevara, Carlos; Graf, Thomas
2013-04-01
Subsurface water systems are endangered due to salt water intrusion in coastal aquifers, leachate infiltration from waste disposal sites and salt transport in agricultural sites. This leads to the situation where more dense fluid overlies a less dense fluid creating a density gradient. Under certain conditions this density gradient produces instabilities in form dense plume fingers that move downwards. This free convection increases solute transport over large distances and shorter times. In cases where a significantly larger density gradient exists, the effect of free convection on transport is non-negligible. The assumption of a constant density distribution in space and time is no longer valid. Therefore variable-density flow must be considered. The flow equation and the transport equation govern the numerical modeling of variable-density flow and solute transport. Computer simulation programs mathematically describe variable-density flow using the Oberbeck-Boussinesq Approximation (OBA). Three levels of simplifications can de considered, which are denoted by OB1, OB2 and OB3. OB1 is the usually applied simplification where variable density is taken into account in the hydraulic potential. In OB2 variable density is considered in the flow equation and in OB3 variable density is additionally considered in the transport equation. Using the results from a laboratory-scale experiment of variable-density flow and solute transport (Simmons et al., Transp. Porous Medium, 2002) it is investigated which level of mathematical accuracy is required to represent the physical experiment the most accurate. Differences between the physical and mathematical model are evaluated using qualitative indicators (e.g. mass fluxes, Nusselt number). Results show that OB1 is required for small density gradients and OB3 is required for large density gradients.
Wave-induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
M. Drivdal
2014-12-01
Full Text Available This study focuses on how wave–current and wave–turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis–Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory. Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.
Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Drivdal, M.; Broström, G.; Christensen, K. H.
2014-05-01
The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory). Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.
Wave-induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Drivdal, M.; Broström, G.; Christensen, K. H.
2014-12-01
This study focuses on how wave-current and wave-turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis-Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.
Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
M. Drivdal
2014-05-01
Full Text Available The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis–Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory. Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.
Blandford, Edward D., E-mail: edb@unm.edu [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131-0001 (United States); Peterson, Per F. [Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1730 (United States)
2013-09-15
Highlights: • We develop a novel buoyantly-driven shutdown rod concept for a FHR. • Shutdown rod system can be actively or passively activated during transients. • Response of the rod was computationally simulated and experimentally validated. • Initial results indicate rod could provide effective transient reactivity control. -- Abstract: This paper presents a novel buoyantly-driven shutdown rod concept for use in Fluoride salt-cooled High-temperature Reactors (FHRs). The baseline design considered here is a 900 MWth modular version of the FHR class called the Pebble Bed Advanced High-Temperature Reactor (PB-AHTR) that uses pebble fuel. Due to the high volumetric heat capacity of the primary coolant, the FHRs operate with a high power density core with a similar average coolant temperature as in modular helium reactors. The reactivity control system for the baseline PB-AHTR uses a novel buoyantly-driven shutdown rod system that can be actively or passively activated during reactor transients. In addition to a traditional active insertion mechanism, the new shutdown rod system is designed to also operate passively, fulfilling the role of a reserve shutdown system. The physical response of the shutdown rod was simulated both computationally and experimentally, using scaling arguments where applicable, with an emphasis on key phenomena identified by a preliminary Phenomena Identification and Ranking Table (PIRT) study. This paper presents results from both the pre-predicted simulation and experimental validation efforts.
Highlights: • We develop a novel buoyantly-driven shutdown rod concept for a FHR. • Shutdown rod system can be actively or passively activated during transients. • Response of the rod was computationally simulated and experimentally validated. • Initial results indicate rod could provide effective transient reactivity control. -- Abstract: This paper presents a novel buoyantly-driven shutdown rod concept for use in Fluoride salt-cooled High-temperature Reactors (FHRs). The baseline design considered here is a 900 MWth modular version of the FHR class called the Pebble Bed Advanced High-Temperature Reactor (PB-AHTR) that uses pebble fuel. Due to the high volumetric heat capacity of the primary coolant, the FHRs operate with a high power density core with a similar average coolant temperature as in modular helium reactors. The reactivity control system for the baseline PB-AHTR uses a novel buoyantly-driven shutdown rod system that can be actively or passively activated during reactor transients. In addition to a traditional active insertion mechanism, the new shutdown rod system is designed to also operate passively, fulfilling the role of a reserve shutdown system. The physical response of the shutdown rod was simulated both computationally and experimentally, using scaling arguments where applicable, with an emphasis on key phenomena identified by a preliminary Phenomena Identification and Ranking Table (PIRT) study. This paper presents results from both the pre-predicted simulation and experimental validation efforts
Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi
2015-06-16
Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the "elements strategy", we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced science and technology could create higher-performance materials even while replacing or reducing minor or harmful elements through the combination of more abundant elements. The properties of elements are correlated directly with their electronic states. In a solid, the magnitude of the density of states (DOS) at the Fermi level affects the physical and chemical properties. In the present age, more attention has been paid to improving the properties of materials by means of alloying elements. In particular, the solid-solution-type alloy is advantageous because the properties can be continuously controlled by tuning the compositions and/or combinations of the constituent elements. However, the majority of bulk alloys are of the phase-separated type under ambient conditions, where constituent elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect and developed methods involving "nonequilibrium synthesis" or "a process of hydrogen absorption/desorption". We propose a new concept of "density-of-states engineering" for the design of materials having the most desirable and suitable properties by means of "interelement fusion". In this Account, we describe novel solid-solution alloys of Pd-Pt, Ag-Rh, and Pd-Ru systems in which the constituent elements are immiscible in the bulk state. The homogeneous solid-solution alloys of Pd and Pt were created from Pd core/Pt shell nanoparticles using a
Modelling thermal radiation and soot formation in buoyant diffusion flames
The radiative heat transfer plays an important role in fire problems since it is the dominant mode of heat transfer between flames and surroundings. It controls the pyrolysis, and therefore the heat release rate, and the growth rate of the fire. In the present work a numerical study of buoyant diffusion flames is carried out, with the main objective of modelling the thermal radiative transfer and the soot formation/destruction processes. In a first step, different radiative property models were tested in benchmark configurations. It was found that the FSCK coupled with the Modest and Riazzi mixing scheme was the best compromise in terms of accuracy and computational requirements, and was a good candidate to be implemented in CFD codes dealing with fire problems. In a second step, a semi-empirical soot model, considering acetylene and benzene as precursor species for soot nucleation, was validated in laminar co flow diffusion flames over a wide range of hydrocarbons (C1-C3) and conditions. In addition, the optically-thin approximation was found to produce large discrepancies in the upper part of these small laminar flames. Reliable predictions of soot volume fractions require the use of an advanced radiation model. Then the FSCK and the semi-empirical soot model were applied to simulate laboratory-scale and intermediate-scale pool fires of methane and propane. Predicted flame structures as well as the radiant heat flux transferred to the surroundings were found to be in good agreement with the available experimental data. Finally, the interaction between radiation and turbulence was quantified. (author)
Persistence of Strain in Buoyant and Nonbuoyant Turbulent Nonpremixed Flames
Boratav, O.; Elghobashi, S.; Zhong, R.
1997-11-01
The effects of chemical reaction and buoyancy on the persistence of strain are studied in three different flows: i) Nonbuoyant flame, ii) Buoyant flame with gravity perpendicular to the initial fuel-oxidant interface (horizontal flame) and iii) Same as (ii), but gravity is parallel to the initial interface (vertical flame). The magnitude of the rate of strain S_ij relative to vorticity ω is measured by the angle ψ = tan-1(2 S_ijS_ij/ω \\cdot ω). Three mixture fraction, F, regions of distinct ψ characteristics are identified: 1) F>F_st, 2) Fflames, regions and (2) are vorticity-dominated due to the large baroclinic vorticity production, i.e. ψ arrow 0, resulting in shifting the pdf's of the ω-strain eigendirection more towards the β direction than the α. In region (3), the vorticity production is negligible for all three flows and at all times, thus resulting in the persistence of strain dominance over vorticity, i.e. ψ ≈ π/2, enforcing the alignment of ω with the α eigendirection. Consequently, the nabla F transport equation shows that nabla F will be located in the β-γ plane near F_st. Since |γ| > |β|, the largest straining of nabla F will be mostly along the direction of the most compressive strain direction γ near F_st as observed in all three cases. Our DNS results show that in reacting flows, the peak scalar dissipation ɛF will be near F_st regardless of the presence of buoyancy.
Numerical simulation of turbulent buoyant flows in horizontal channels
A numerical method is presented, to calculate the three-dimensional, time-dependent large scale structure of turbulent buoyant flows. The subject of the study is the Rayleigh-Benard-convection with air (Pr=0.71, Ra=2.5 106, 107) and sodium (Pr=0.006, Ra=8.4 104, 2.5 105, 106, 107) and a fluid layer with water and an internal heat source (Pr=7.0, RaI=1.5 1010) at moderate and high Rayleigh-numbers. The goal of the work is both, the analysis of structures of instantaneous as well as the statistical analysis of spatially and/or time averaged data, to give a contribution to the investigation of the characteristics of turbulent natural convection mainly in fluids with small Prandtl-numbers. The large eddy simulation of natural convection requires the development of appropriate momentum and heat subgrid scale models and the formulation of new boundary conditions. The used energy-length-models in the computer code TURBIT are extended methodically by modification of the characteristic length scales of the sub scale turbulence. The reduction or the increase of the sub scale turbulence correlations, caused by the influence of solid boundaries or the stratification, is considered. In the same way the new boundary conditions for the diffusive terms of the conservation equations are seen to be necessary, when the thermal or in the case of liquid metals the more critical hydrodynamic boundary layer is resolved insufficiently or not at all. The extended and new methods, models and boundary conditions, which enabled the realization of the planned simulations, are presented. (orig.)
Supergranulation as the Sun's largest buoyantly driven mode of convection
Cossette, Jean-Francois; Rast, Mark
2016-05-01
Solar supergranulation has been characterized as horizontally divergent flow motions having a typical scale of 32 Mm using Doppler imaging, granule tracking and helioseismology. Unlike granules, the size of which is comparable to both the thickness of the radiative boundary layer and local scale height at the photosphere, supergranules do not appear to correspond to any particular length scale of the flow. Possible explanations ranging from convection theories involving Helium ionization to spatial correlation or self-organization of granular flows have been proposed as physical mechanisms to explain solar supergranulation. However, its existence remains largely a mystery. Remarkably, horizontal velocity power spectra obtained from Doppler imaging and correlation tracking of flow features at the solar surface reveal the presence of peaks corresponding to granular and supergranular scales, followed by a monotonic decrease in power at scales larger than supergranulation, which suggests that large-scale modes in the deep layers of the convection zone may be suppressed. Using 3D anelastic simulations of solar convection we investigate whether supergranulation may reflect the largest buoyantly driven mode of convection inside the Sun. Results show that the amount of kinetic energy contained in the largest flow scales relative to that associated with supergranular motions is a function of the depth of the transition from a convectively unstable to convectively stable mean stratification inside the simulation. This suggests that the observed monotonic decrease in power at scales larger than supergranulation may be explained by rapid cooling in the subphotospheric layers and an essentially isentropic solar interior, wherein convective driving is effectively suppressed.
Sasaki, Koichi; Ishigame, Hiroaki; Nishiyama, Shusuke
2015-01-01
This paper reports the density distributions of OH, Na, water vapor and water mist in atmospheric-pressure dc helium glow plasmas in contact with NaCl solution. The densities of OH, Na and H2O had different spatial distributions, while the Na density had a similar distribution to mist, suggesting that mist is the source of Na in the gas phase. When the flow rate of helium toward the electrolyte surface was increased, the distributions of all the species densities concentrated in the neighbori...
Lv, Boqiang; Shi, Xiaoding; Zhong, Xin
2015-01-01
We are concerned with the Cauchy problem of the two-dimensional (2D) nonhomogeneous incompressible Navier-Stokes equations with vacuum as far-field density. It is proved that if the initial density decays not too slow at infinity, the 2D Cauchy problem of the density-dependent Navier-Stokes equations on the whole space $\\mathbb{R}^2$ admits a unique global strong solution. Note that the initial data can be arbitrarily large and the initial density can contain vacuum states and even have compa...
Elmahdy, Mahdy M; Drechsler, Astrid; Uhlmann, Petra; Stamm, Manfred
2016-06-01
In previous studies, the authors found that end-grafted layers of the weak polybase poly(2-vinylpyridine) (P2VP) in aqueous solutions do not only swell and collapse if the pH value and salt concentration are varied but also exhibit a pH- and salinity-dependent adhesion to microsized silica spheres. For a better understanding of these effects, in situ force measurements using the AFM colloidal probe technique were applied to end-grafted P2VP layers of different grafting densities in NaCl solutions at pH 2.5. Although a mushroom-to-brush transition could be seen in the dry state, the layers were in the brush regime in aqueous solutions at all NaCl concentrations and grafting densities. We observed an increase of the brush height with increasing grafting density and a salinity-dependent collapse and reswelling of the brushes. The adhesion between the P2VP layer and a silica sphere depended on both grafting density and salinity. At low salt concentrations, the adhesion reached its highest value at the intermediate grafting density and disappeared with denser brushes. Maximum adhesion was obtained for high NaCl concentrations and the lowest grafting density. From a detailed analysis of the experiments, we gained insight into chain stretching and density profiles under complex ionic conditions and into the mechanism of adhesion of polyelectrolytes to solid surfaces. PMID:27172173
Highlights: • Apparent and partial molar volumes of aqueous AAILs at T = (293.15 to 313.15) K. • Isothermal and adiabatic compressibilities of AAILs in aqueous solution at T = 298.15 K. • Method for direct estimation of hydration numbers due to electrostriction is given. • Internal pressure and hydration numbers for AAILs at T = 298.15 K. • Results obtained demonstrate kosmotropic behavior of AAILs. - Abstract: Amino acid ionic liquids (AAILs) have huge potential in the field of protein chemistry, enzymatic reactions, templates for synthetic study etc. which is due to their distinctive properties like unique acid-base characteristics, tunable hydrophobicity, hydrogen bonding ability and strong hydration effects. To explore the field of bio-ionic liquids for its real life applications and sustainable technology development, it is essential to have better understanding of these newly researched liquid salts in life’s most chosen medium, i.e. in aqueous medium, through study of their physicochemical properties in aqueous solutions. In this context, we are reporting herewith measurements and analysis of volumetric properties in the temperature range of (293.15 to 313.25) K and acoustic properties at 298.15 K in the concentration range of (0.05 to 0.5) mol · kg−1 for aqueous solutions of 1-butyl-3-methylimidazolium [Bmim] based amino acid ionic liquids, prepared from glycine, L-alanine, L-valine, L-leucine and L-isoleucine. The experimental density and sound speed data were used to obtain apparent, partial and limiting molar volumes as well as isentropic and isothermal compressibility properties. These data have been further used to understand electrostriction as well as concentration dependence of internal pressure. The hydration numbers for AAILs in aqueous medium were estimated from compressibility data using Passynski method and the estimated ionic hydration numbers are compared with those obtained using activity data. The results are explained in
Highlights: ► Molecular recognition properties of metal bis-porphyrins at high concentration. ► The formation of the complex causes the disruption of the aggregates. ► High sensitivity for the optical detection of low amount of amino acids. ► Potential applications as a selective molecular sensor of amino acids. - Abstract: Small angle X-ray measurements on concentrated solutions of Cobalt-bis-porphyrins showed, at all the investigated concentration values, the presence of small aggregates which possess a sphere-like shape with a homogeneous electron density distribution. Such an aggregation, however, is proven not to affect the binding properties of the molecules with amino acids. Indeed, the Cobalt ion of the bis-porphyrins are available for coordinating the nitrogen atom of the amino acid to form a stable complex, as indicated by UV–vis and circular dichroism spectroscopy. The ability of these uncharged water-soluble bis-porphyrins to act as molecular sensors of amino acids in a wide concentration range takes great relevance in biosensing applications for which high concentration might be required.
Deeney, F A; O' Leary, J P [Physics Department, National University of Ireland, Cork, Republic of Ireland (Ireland)], E-mail: f.a.deeney@ucc.ie
2008-09-15
The connection between quantum zero point fluctuations and a density maximum in water and in liquid He{sup 4} has recently been established. Here we present a description of a simple and rapid method of determining the temperatures at which maximum densities in water and aqueous solutions occur. The technique is such as to allow experiments to be carried out in one session of an undergraduate laboratory thereby introducing students to the concept of quantum zero point energy.
Guru, Pravat Ranjan; Nayak, Amit Kumar; Sahu, Rajendra Kumar
2013-04-01
The current investigation deals with the development and optimization of oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac by ionotropic emulsion-gelation technique using 3(2) factorial design. The effect of polymer to drug ratio and sodium alginate to sterculia gum ratio on the drug entrapment efficiency (%), and cumulative drug release after 7 h (%) was optimized. The optimized oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac (F-O) showed drug entrapment efficiency of 90.92±2.34%, cumulative drug release of 41.65±3.97% after 7 h in simulated gastric fluid (pH 1.2), and well buoyancy over 8 h in simulated gastric fluid (pH 1.2) with 5.20 min buoyant lag-time. The in vitro drug release from these buoyant beads followed Korsmeyer-Peppas model (R(2)=0.9866-0.9995) with anomalous (non-Fickian) diffusion drug release mechanism. These new sterculia gum-alginate buoyant beads containing aceclofenac were also characterized using SEM, FTIR, and P-XRD analysis. PMID:23334180
Cao, Siqin [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Sheong, Fu Kit [Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Huang, Xuhui, E-mail: xuhuihuang@ust.hk [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Division of Biomedical Engineering, Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)
2015-08-07
Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute.
Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute
Powering of cool filaments in cluster cores by buoyant bubbles - I. Qualitative model
Churazov, E.; Ruszkowski, M.; Schekochihin, A.
2013-11-01
Cool-core clusters (e.g. Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, infrared, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. Active galactic nucleus (AGN)-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of β = 8πPgas/B2 ˜ 1. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or to the Earth's magnetotail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.
Powering of cool filaments in cluster cores by buoyant bubbles. I. Qualitative model
Churazov, E; Schekochihin, A
2013-01-01
Cool-core clusters (e.g., Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, IR, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. AGN-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of $\\beta =8\\pi P_{gas}/B^2\\sim 1$. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or the Earth magneto-tail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.
Perturbation and stability analyses of nonlinear buoyant flow in mushy layers
Okhuysen, B S [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Riahi, D N, E-mail: driahi@utpa.ed [Department of Mathematics, 1201 West University Drive, University of Texas-Pan American, Edinburg, TX 78541-2999 (United States)
2010-10-15
We consider the problem of weakly nonlinear buoyant flow and its stability in horizontal dendrite layers, often referred to as mushy layers, during solidification of binary alloys. A mushy layer is a layer that is formed adjacent to the solidification front and is composed of both solid dendrites and melt. Understanding the convective flow driven by the buoyancy force within the mushy layer is known to be important for proper production of high-quality solidified alloy. In the present study, no restriction is imposed on the thickness of the mushy layer, and a number of simplifying assumptions made in previous related nonlinear analyses are lifted here in order to determine the results on the basis of a more realistic model. Using perturbation and stability analyses and some numerical approaches, we determine the steady stable solutions to the weakly nonlinear problem under a certain range of the parameter values where such analyses are valid. The relevant parameters for the present problem are the Rayleigh number representing the buoyancy, the Stefan number representing the latent heat of solidification, a concentration ratio parameter representing the composition of the solid dendrites in the mushy layer, and the far-field temperature parameter. We found, in particular, that depending on the range of parameter values, stable convective flow is possible in the form of subcritical or supercritical down-hexagons, with down-flow at the cells' centers and up-flow at the cells' boundaries, and subcritical or supercritical up-hexagons, with up-flow at the cells' centers and down-flow at the cells' boundaries, supercritical rectangles, supercritical squares and supercritical rolls.
Willige, van R.W.G.; Linssen, J.P.H.; Legger, A.; Voragen, A.G.J.
2003-01-01
The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic f
Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation.
Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong
2014-12-01
A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire. PMID:25554341
STABILITY AND MIXING CHARACTER FOR BUOYANT JETS IN QUIESCENT SHALLOW WATER
ZENG Yu-hong
2005-01-01
The near field stability and mixing characteristics of buoyant jets produced by thermal diffuse in quiescent shallow water are investigated numerically to predict under what combinations of discharge and ambient characteristics the near field will be stable or unstable.Analyses for different discharging types show that the discharge stability is purely dependent on the near-field behavior of the jets, or the dynamic interaction of the buoyant jet region, the surface impingement region and the internal hydraulic jump region, and is independent of the far-field geometry of the receiving water.The stability criterion is a function of the relative submerged depth, and source densimetric Froude number.
Sindt CW
2012-03-01
Full Text Available Christine W Sindt1, Trudy K Grout1, D Brice Critser1, Jami R Kern2, David L Meadows21University of Iowa Hospitals and Clinics, Iowa City, IA; 2Alcon Research Ltd, Fort Worth, TX, USABackground: The purpose of this study was to assess whether differences in central corneal dendritic immune cell densities associated with combinations of soft contact lenses and lens care solutions could be detected by in vivo confocal microscopy.Methods: Participants were adults naïve to contact lens wear (n = 10 or who wore soft contact lenses habitually on a daily-wear schedule (n = 38 or on a study-assigned schedule for 30 days with daily disposable silicone hydrogel lenses (n = 15. Central corneas were scanned using an in vivo confocal microscope. Cell densities were compared among groups by demographic parameters, lens materials, and lens care solutions (polyhexamethylene biguanide [PHMB], polyquaternium-1 and myristamidopropyl dimethylamine [PQ/MAPD], peroxide, or blister pack solution [for daily disposable lenses].Results: Among lens wearers, no associations were observed between immune cell densities and age, gender, or years of lens-wearing experience. Mean cell density was significantly lower (P < 0.01 in nonwearers (29 ± 23 cells/mm2, n = 10 than in lens wearers (64 ± 71 cells/mm2, n = 53. Mean cell density was lower (P = 0.21 with traditional polymer lenses (47 ± 44 cells/mm2, n = 12 than with silicone hydrogel lenses (69 ± 77 cells/mm2, n = 41. Lowest to highest mean density of immune cells among lens wearers was as follows: PQ/MAPD solution (49 ± 28 cells/mm2, blister pack solution (63 ± 81 cells/mm2, PHMB solution (66 ± 44 cells/mm2, and peroxide solution (85 ± 112 cells/mm2.Conclusion: In this pilot study, in vivo confocal microscopy was useful for detecting an elevated immune response associated with soft contact lenses, and for identifying lens-related and solution-related immune responses that merit further research.Keywords: Clear Care
Stec, Marcin; Tatarczuk, Adam; Spiewak, Dariusz; Wilk, Andrzej
2014-01-01
The densities of aqueous mixtures of aminoethylethanolamine (CAS #000111-41-1) were measured over the entire compositional range at temperatures of 283.15-343.15 K. The results of these measurements were used to calculate excess molar volumes and isobaric thermal expansion coefficients, and partial molar and apparent molar volumes and excess isobaric thermal expansion coefficients were subsequently derived. The excess molar volumes were correlated as a function of the mole fraction using the Redlich-Kister equation. Temperature dependences of the Redlich-Kister coefficients are also presented. The partial molar volumes at infinite dilution of AEEA in water were determined using two different methods. In addition, the solution density was correlated using a Joubian-Acree model. Aqueous solutions of AEEA exhibit similar properties to the aqueous solutions of other alkanolamines (like monoethanolamine) used in acid gas sweetening. PMID:24899753
Novel solution-soaking method for adding dopants to YBa2Cu3O7-x to achieve higher sintered densities
YBa2Cu3O7-x was doped with various metal ions by a new technique in which a pellet (after binder burnout) was soaked in a solution containing the appropriate ions and then dried. The sintered density of the treated pellets depended on the dopant in the solution,and in many cases it was much higher than that obtained for pure YBa2Cu3O7-x (93% to 96% as compared with 85% to 90%). A study of the microstructure revealed that, in those cases where higher sintered densities were obtained, the grain size was much smaller. The grain morphology, however, did not change. It is likely that the high concentration of dopant adsorbed on the grain surface during solution soaking enhanced the rate of sintering
The aim of this research program is to improve our knowledge and predictive capability of buoyant plume dispersion in the convective boundary layer (CBL) with emphasis on the mean (C) and root-mean-square (?c) concentration fields. The CBL turbulence leads to large random fluc...
46 CFR 117.137 - Stowage of life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Stowage of life floats and buoyant apparatus. 117.137 Section 117.137 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE THAN 150 PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS LIFESAVING EQUIPMENT AND ARRANGEMENTS...
Brown, Richard S.; Pflugrath, Brett D.; Carlson, Thomas J.; Deng, Zhiqun
2012-02-03
On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing through hydroturbines experience a rapid decrease in pressure as they pass by the turbine blade and the severity of this decompression can be highly variable. This rapid decrease in pressure can result in injuries such as swim bladder rupture, exophthalmia, and emboli and hemorrhaging in the fins and tissues. However, recent research indicates that the presence of a telemetry tag (acoustic, radio, inductive) implanted inside the coelom of a juvenile salmon increases the likelihood that the fish will be injured or die during turbine passage. Thus, previous research conducted using telemetry tags implanted into the coelom of fish may have been inaccurate. Thus, a new technique is needed to provide unbiased estimates of survival through turbines. This research provides an evaluation of the effectiveness of a neutrally buoyant externally attached acoustic transmitter. Both nontagged fish and fish tagged with a neutrally buoyant external transmitter were exposed to a range of rapid decompressions simulating turbine passage. Juvenile Chinook salmon tagged with a neutrally buoyant externally attached acoustic transmitter did not receive a higher degree of barotrauma than their nontagged counterparts. We suggest that future research include field-based comparisons of survival and behavior among fish tagged with a neutrally buoyant external transmitter and those internally implanted with transmitters.
46 CFR 180.137 - Stowage of life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 7 2010-10-01 2010-10-01 false Stowage of life floats and buoyant apparatus. 180.137 Section 180.137 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) LIFESAVING EQUIPMENT AND ARRANGEMENTS Survival Craft Arrangements and Equipment § 180.137 Stowage of life floats...
Sumi, Tomonari; Maruyama, Yutaka; Mitsutake, Ayori; Koga, Kenichiro
2016-06-01
In the conventional classical density functional theory (DFT) for simple fluids, an ideal gas is usually chosen as the reference system because there is a one-to-one correspondence between the external field and the density distribution function, and the exact intrinsic free-energy functional is available for the ideal gas. In this case, the second-order density functional Taylor series expansion of the excess intrinsic free-energy functional provides the hypernetted-chain (HNC) approximation. Recently, it has been shown that the HNC approximation significantly overestimates the solvation free energy (SFE) for an infinitely dilute Lennard-Jones (LJ) solution, especially when the solute particles are several times larger than the solvent particles [T. Miyata and J. Thapa, Chem. Phys. Lett. 604, 122 (2014)]. In the present study, we propose a reference-modified density functional theory as a systematic approach to improve the SFE functional as well as the pair distribution functions. The second-order density functional Taylor series expansion for the excess part of the intrinsic free-energy functional in which a hard-sphere fluid is introduced as the reference system instead of an ideal gas is applied to the LJ pure and infinitely dilute solution systems and is proved to remarkably improve the drawbacks of the HNC approximation. Furthermore, the third-order density functional expansion approximation in which a factorization approximation is applied to the triplet direct correlation function is examined for the LJ systems. We also show that the third-order contribution can yield further refinements for both the pair distribution function and the excess chemical potential for the pure LJ liquids.
Highlights: ► Di- and tri-glycine in aqueous PEG400 solutions were investigated thermodynamically. ► Density and ultrasound speed of glycine oligomer-PEG400-water systems were measured. ► Apparent molar volumes and isentropic compressions were calculated. ► Apparent molar isobaric expansions were derived. ► Results were interpreted in terms of water–glycine oligomer-PEG400 interactions. -- Abstract: Density and ultrasound speed were measured accurately for diglycine + water, triglycine + water, diglycine + water-polyethylene glycol 400 (PEG400) and triglycine + water-PEG400 solutions at T = (293.15, 298.15, 303.15 and 308.15) K. The results were used in evaluating thermodynamic properties as apparent molar volumes (VØ) and apparent molar isentropic compressions (KSΦ) of diglycine and triglycine in water and in PEG400 solutions. Infinite dilution values of these parameters, VoØ, and KoSΦ, were obtained from their plots as a function of molality by extrapolation and have been utilized in obtaining transfer volumes and transfer compressions at infinite dilution. All transfer volumes and transfer compressions were found to increase with increasing molality of PEG400. Apparent molar isobaric expansions were derived from the temperature dependence of VØ values at infinite dilution and at finite concentrations. All the results were interpreted in terms of solute (diglycine or triglycine) and co-solute (PEG400) and solvent (H2O) interactions
Fan, Jianke; Zhao, Dapeng; Dong, Dongdong
2016-02-01
We determined P-wave tomographic images by inverting a large number of arrival-time data from 2749 local earthquakes and 1462 teleseismic events, which are used to depict the three-dimensional morphology of the subducted Eurasian Plate along the northern segment of the Manila Trench. Dramatic changes in the dip angle of the subducted Eurasian Plate are revealed from the north to the south, being consistent with the partial subduction of a buoyant plateau beneath the Luzon Arc. Slab tears may exist along the edges of the buoyant plateau within the subducted plate induced by the plateau subduction, and the subducted lithosphere may be absent at depths greater than 250 km at ˜19°N and ˜21°N. The subducted buoyant plateau is possibly oriented toward NW-SE, and the subducted plate at ˜21°N is slightly steeper than that at ˜19°N. These results may explain why the western and eastern volcanic chains in the Luzon Arc are separated by ˜50 km at ˜18°N, whereas they converge into a single volcanic chain northward, which may be related to the oblique subduction along the Manila Trench caused by the northwestern movement of the Philippine Sea Plate. A low-velocity zone is revealed at depths of 20-200 km beneath the Manila Accretionary Prism at ˜22°N, suggesting that the subduction along the Manila Trench may stop there and the collision develops northward. The Taiwan Orogeny may originate directly from the subduction of the buoyant plateau, because the initial time of the Taiwan Orogeny is coincident with that of the buoyant plateau subduction.
Influence of cooling on dynamics of buoyant jet
Goncharov, V P
2016-01-01
The Rayleigh--Taylor instability which is responsible for the occurrence of narrow upward jets are studied in the scope of the nonhydrostatic model with horizontally--nonuniform density and the Newtonian cooling. As analysis shows, the total hierarchy of instabilities in this model consists of three regimes -- collapse, algebraic instability, and inertial motion. Realization of these stages, mutual transitions and interference depend on a ratio between two characteristic time scales -- collapse time and cooling time.
This paper provides for various cases of 235U enrichment or Pu isotopic vectors, and different reflectors, new minimum critical values of uranyl nitrate and plutonium nitrate solutions (H+=0) obtained by the standard IRSN calculation route and the new isopiestic density laws. Comparisons are also made with other more accurate routes showing that the standard one's results are most often conservative and usable for criticality safety assessments. (author)
Mamyrbekova, A. K.
2013-03-01
Physicochemical properties (density, dynamic viscosity, refraction index) of the DMSO-Cu(NO3)2 · 3H2O system are studied in the concentration range of 0.01-2 M at 298 K. The refraction index of a solution of copper(II) nitrate in dimethylsulfoxide (DMSO) is measured at 288-318 K. The excess and partial molar volumes of the solvent and dissolved substance are calculated analytically.
Adiabatic density surface, neutral density surface, potential density surface, and mixing path
HUANG Rui-xin
2014-01-01
In this paper, adiabatic density surface, neutral density surface and potential density surface are compared. The adiabatic density surface is defined as the surface on which a water parcellcan move adiabatically, without changing its potential temperature and salinity. For a water parcelltaken at a given station and pressure level, the corresponding adiabatic density surface can be determined through simple calculations. This family of surface is neutrally buoyant in the world ocean, and different from other surfaces that are not truly neutrally buoyant. In order to explore mixing path in the ocean, a mixing ratio m is introduced, which is defined as the portion of potential temperature and salinity of a water parcellthat has exchanged with the environment during a segment of migration in the ocean. Two extreme situations of mixing path in the ocean are m=0 (no mixing), which is represented by the adiabatic density curve, and m=1, where the original information is completely lost through mixing. The latter is represented by the neutral density curve. The reality lies in between, namely, 0
Highlights: • The densities, refractive indices, and viscosities of aqueous DES solutions were measured. • DES are made from N,N-diethylethanol ammonium chloride + glycerol or ethylene glycol. • The temperature studied was (298.15 to 343.15) K. • The measured data were reported as functions of temperature and composition. • The measured data were represented satisfactorily by the applied correlations. -- Abstract: In this work, we report new experimental data on density, ρ, refractive index, nD, and viscosity, η, of two deep eutectic solvents, N,N-diethylethanol ammonium chloride–glycerol (DEACG) and N,N-diethylethanol ammonium chloride–ethylene glycol (DEACEG), and their aqueous solutions, over the complete composition range, at temperatures from (298.15 to 343.15) K. Densities and viscosities were measured using the vibrating tube and the falling ball techniques, respectively, while the refractive index at the sodium D line was measured using an automatic refractometer. We aimed to represent the measured properties as a function of temperature and composition, and correlated them using the Redlich–Kister-type equation, for density, a polynomial function, for refractive index, and the Vogel–Fulcher–Tammann (VFT) equation, for viscosity
Morphology of flows and buoyant bubbles in the Virgo cluster
Pavlovski, Georgi; Pope, Edward C D; Fangohr, Hans
2007-01-01
There is growing evidence that the active galactic nuclei (AGN) associated with the central elliptical galaxy in clusters of galaxies are playing an important role in the evolution of the intracluster medium (ICM) and clusters themselves. We use high resolution three-dimensional simulations to study the interaction of the cavities created by AGN outflows (bubbles) with the ambient ICM. The gravitational potential of the cluster is modelled using the observed temperature and density profiles of the Virgo cluster. We demonstrate the importance of the hydrodynamical Kutta-Zhukovsky forces associated with the vortex ring structure of the bubbles, and discuss possible effects of diffusive processes on their evolution.
ZHANG Baoqiang; CHEN Guoping; GUO Qintao
2012-01-01
An improved method using kernel density estimation (KDE) and confidence level is presented for model validation with small samples.Decision making is a challenging problem because of input uncertainty and only small samples can be used due to the high costs of experimental measurements.However,model validation provides more confidence for decision makers when improving prediction accuracy at the same time.The confidence level method is introduced and the optimum sample variance is determined using a new method in kernel density estimation to increase the credibility of model validation.As a numerical example,the static frame model validation challenge problem presented by Sandia National Laboratories has been chosen.The optimum bandwidth is selected in kernel density estimation in order to build the probability model based on the calibration data.The model assessment is achieved using validation and accreditation experimental data respectively based on the probability model.Finally,the target structure prediction is performed using validated model,which are consistent with the results obtained by other researchers.The results demonstrate that the method using the improved confidence level and kernel density estimation is an effective approach to solve the model validation problem with small samples.
Fleischer, F.; Weber, T.; Deloudi, S.; Palatinus, Lukáš; Steurer, W.
2010-01-01
Roč. 43, - (2010), s. 89-100. ISSN 0021-8898 Institutional research plan: CEZ:AV0Z10100521 Keywords : phase retrieval * charge flipping * low-density elimination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.794, year: 2010
The Heads and Tails of Buoyant Autocatalytic Balls
Rogers, Michael C
2012-01-01
Buoyancy produced by autocatalytic reaction fronts can produce fluid flows that advect the front position, giving rise to interesting feedback between chemical and hydrodynamic effects. In a large diameter, extended cylinder that is relatively free of boundary constraints, localized initiation of an iodate-arsenous acid (IAA) reaction front on the bottom boundary generates a rising autocatalytic plume. Such plumes have several differences from their non-reactive counterparts. Using numerical simulation, we have found that if reaction is initiated using a spherical ball of product solution well above the bottom boundary, the subsequent flow can evolve much like an autocatalytic plume: the ball develops a reacting head and tail that is akin to the head and conduit of an autocatalytic plume, except that the tail is disconnected from the boundary. In the limit of large initial autocatalytic balls, however, growth of a reacting tail is suppressed and the resemblance to plumes disappears. Conversely, very small bal...
Two hypotheses for the dissolution of SiO2 in ionic solutions are investigated via ab initio molecular dynamics (AIMD) simulations. The hypotheses are (1) that the presence of ions induces orientations in H2O molecules at the surface, which favor proton transfer to bridging oxygen (BO) atoms, and (2) the presence of ions induces stronger H-bonding between terminal hydroxyl (TH) groups and BO atoms, allowing proton transfer. It is found that the model structures produced by density functional theory simulations do not support the former hypothesis and are more consistent with the latter. (paper)
Generating buoyant magnetic flux ropes in solar-like convective dynamos
Nelson, Nicholas J
2014-01-01
Our Sun exhibits strong convective dynamo action which results in magnetic flux bundles emerging through the stellar surface as magnetic spots. Global-scale dynamo action is believed to generate large-scale magnetic structures in the deep solar interior through the interplay of convection, rotation, and shear. Portions of these large-scale magnetic structures are then believed to rise through the convective layer, forming magnetic loops which then pierce the photosphere as sunspot pairs. Previous global simulations of 3D MHD convection in rotating spherical shells have demonstrated mechanisms whereby large-scale magnetic wreaths can be generated in the bulk of the convection zone. Our recent simulations have achieved sufficiently high levels of turbulence to permit portions of these wreaths to become magnetically buoyant and rise through the simulated convective layer through a combination of magnetic buoyancy and advection by convective giant cells. These buoyant magnetic loops are created in the bulk of the...
Characteristics of flammable, buoyant hydrogen plumes rising from open vertical containers
Fardisi, S.; Karim, Ghazi A. [University of Calgary, Mechanical and Manufacturing Engineering Department, 2500 University Drive, NW, Calgary, Alberta (Canada)
2009-08-15
The dynamics of the dispersion of a fixed mass of the highly buoyant hydrogen when exposed to overlaying atmosphere with a negligible pressure difference from open vertical cylindrical enclosures are examined. Features of the rapid formation and dispersion of flammable mixtures both inside and immediate outside of the enclosure and their corresponding propagation rates were examined using a 3-D CFD model. For the cases considered, the puffs of the fuel-air mixture appear to produce lean flammable boundaries that move mainly at a near constant rate for much of the time. A similar simulation that used an axis-symmetrical 2-D model tended to under-predict the dynamics of the lean and rich mixture boundaries. Hydrogen plume characteristics were compared with that of the less buoyant methane and helium release. Unlike methane, helium propagation rate was found fairly close to that of hydrogen. (author)
Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun
Nelson, Nicholas J; Brun, Allan Sacha; Miesch, Mark S; Toomre, Juri
2011-01-01
The current dynamo paradigm for the Sun and sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and star-spots on sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here we present the first 3-D global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise...
Influence of viscosity contrast on buoyantly unstable miscible fluids in porous media
Pramanik, Satyajit; Mishra, Manoranjan
2015-01-01
The influence of viscosity contrast on buoyantly unstable miscible fluids in a porous medium is investigated through a linear stability analysis (LSA) as well as direct numerical simulations (DNS). The linear stability method implemented in this paper is based on an initial value approach, which helps to capture the onset of instability more accurately than the quasi-steady state analysis. In the absence of displacement, we show that viscosity contrast delays the onset of instability in buoyantly unstable miscible fluids. Further, it is observed that suitably choosing the viscosity contrast and injection velocity a gravitationally unstable miscible interface can be stabilized completely. Through LSA we draw a phase diagram, which shows three distinct stability regions in a parameter space spanned by the displacement velocity and the viscosity contrast. DNS are performed corresponding to parameters from each regime and the results obtained are in accordance with the linear stability results. Moreover, the conv...
Canepa, Edward S.
2012-09-01
This article presents a new mixed integer programming formulation of the traffic density estimation problem in highways modeled by the Lighthill Whitham Richards equation. We first present an equivalent formulation of the problem using an Hamilton-Jacobi equation. Then, using a semi-analytic formula, we show that the model constraints resulting from the Hamilton-Jacobi equation result in linear constraints, albeit with unknown integers. We then pose the problem of estimating the density at the initial time given incomplete and inaccurate traffic data as a Mixed Integer Program. We then present a numerical implementation of the method using experimental flow and probe data obtained during Mobile Century experiment. © 2012 IEEE.
Gennaro, A M; Luquita, A; Rasia, M
1996-01-01
The hypothesis that the internal viscosity of erythrocytes is governed by the intracellular hemoglobin (Hb) concentration is examined. Here viscosity is determined by labeling of the cytoplasmic reduced glutathione with the spin label maleimido-Tempo. Erythrocyte populations with different Hb concentrations in isosmotic conditions were obtained through incomplete lysis, followed by cell resealing, and discontinuous density gradient separation. This procedure maintains normal cell shape and vo...