Recent progress in anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Strickland, Michael
2017-03-01
The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, < pL2> ≪ < pT2>. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.
Progress in smooth particle hydrodynamics
Wingate, C.A.; Dilts, G.A.; Mandell, D.A.; Crotzer, L.A.; Knapp, C.E.
1998-07-01
Smooth Particle Hydrodynamics (SPH) is a meshless, Lagrangian numerical method for hydrodynamics calculations where calculational elements are fuzzy particles which move according to the hydrodynamic equations of motion. Each particle carries local values of density, temperature, pressure and other hydrodynamic parameters. A major advantage of SPH is that it is meshless, thus large deformation calculations can be easily done with no connectivity complications. Interface positions are known and there are no problems with advecting quantities through a mesh that typical Eulerian codes have. These underlying SPH features make fracture physics easy and natural and in fact, much of the applications work revolves around simulating fracture. Debris particles from impacts can be easily transported across large voids with SPH. While SPH has considerable promise, there are some problems inherent in the technique that have so far limited its usefulness. The most serious problem is the well known instability in tension leading to particle clumping and numerical fracture. Another problem is that the SPH interpolation is only correct when particles are uniformly spaced a half particle apart leading to incorrect strain rates, accelerations and other quantities for general particle distributions. SPH calculations are also sensitive to particle locations. The standard artificial viscosity treatment in SPH leads to spurious viscosity in shear flows. This paper will demonstrate solutions for these problems that they and others have been developing. The most promising is to replace the SPH interpolant with the moving least squares (MLS) interpolant invented by Lancaster and Salkauskas in 1981. SPH and MLS are closely related with MLS being essentially SPH with corrected particle volumes. When formulated correctly, JLS is conservative, stable in both compression and tension, does not have the SPH boundary problems and is not sensitive to particle placement. The other approach to
General Relativistic Smoothed Particle Hydrodynamics code developments: A progress report
NASA Astrophysics Data System (ADS)
Faber, Joshua; Silberman, Zachary; Rizzo, Monica
2017-01-01
We report on our progress in developing a new general relativistic Smoothed Particle Hydrodynamics (SPH) code, which will be appropriate for studying the properties of accretion disks around black holes as well as compact object binary mergers and their ejecta. We will discuss in turn the relativistic formalisms being used to handle the evolution, our techniques for dealing with conservative and primitive variables, as well as those used to ensure proper conservation of various physical quantities. Code tests and performance metrics will be discussed, as will the prospects for including smoothed particle hydrodynamics codes within other numerical relativity codebases, particularly the publicly available Einstein Toolkit. We acknowledge support from NSF award ACI-1550436 and an internal RIT D-RIG grant.
Progress and Challenges in Coupled Hydrodynamic-Ecological Estuarine Modeling
Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational po...
Progress and challenges in coupled hydrodynamic-ecological estuarine modeling
Ganju, Neil K.; Brush, Mark J.; Rashleigh, Brenda; Aretxabaleta, Alfredo L.; del Barrio, Pilar; Grear, Jason S.; Harris, Lora A.; Lake, Samuel J.; McCardell, Grant; O’Donnell, James; Ralston, David K.; Signell, Richard P.; Testa, Jeremy M.; Vaudrey, Jamie M.P.
2016-01-01
Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear, because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy. PMID:27721675
Buchanan, Cara; Rylander, Marissa Nichole
2013-08-01
The integration of tissue engineering strategies with microfluidic technologies has enabled the design of in vitro microfluidic culture models that better adapt to morphological changes in tissue structure and function over time. These biomimetic microfluidic scaffolds accurately mimic native 3D microenvironments, as well as permit precise and simultaneous control of chemical gradients, hydrodynamic stresses, and cellular niches within the system. The recent application of microfluidic in vitro culture models to cancer research offers enormous potential to aid in the development of improved therapeutic strategies by supporting the investigation of tumor angiogenesis and metastasis under physiologically relevant flow conditions. The intrinsic material properties and fluid mechanics of microfluidic culture models enable high-throughput anti-cancer drug screening, permit well-defined and controllable input parameters to monitor tumor cell response to various hydrodynamic conditions or treatment modalities, as well as provide a platform for elucidating fundamental mechanisms of tumor physiology. This review highlights recent developments and future applications of microfluidic culture models to study tumor progression and therapeutic targeting under conditions of hydrodynamic stress relevant to the complex tumor microenvironment.
Hydrodynamic models for slurry bubble column reactors. Fifth technical progress report
Gidaspow, D.
1995-10-01
The objective of this work is to convert our `learning gas-solid-liquid` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid, and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values.
Gidaspow, D.
1996-04-01
The objective of this investigation is to convert our ``learning gas solid-liquid`` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phase. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. A hydrodynamic model for multiphase flows, based on the principles of mass, momentum and energy conservation for each phase, was developed and applied to model gas-liquid, gas-liquid-solid fluidization and gas-solid-solid separation. To simulate the industrial slurry bubble column reactors, a computer program based on the hydrodynamic model was written with modules for chemical reactions (e.g. the synthesis of methanol), phase changes and heat exchangers. In the simulations of gas-liquid two phases flow system, the gas hold-ups, computed with a variety of operating conditions such as temperature, pressure, gas and liquid velocities, agree well with the measurements obtained at Air Products` pilot plant. The hydrodynamic model has more flexible features than the previous empirical correlations in predicting the gas hold-up of gas-liquid two-phase flow systems. In the simulations of gas-liquid-solid bubble column reactors with and without slurry circulation, the code computes volume fractions, temperatures and velocity distributions for the gas, the liquid and the solid phases, as well as concentration distributions for the species (CO, H{sub 2}, CH{sub 3}0H, ... ), after startup from a certain initial state. A kinetic theory approach is used to compute a solid viscosity due to particle collisions. Solid motion and gas-liquid-solid mixing are observed on a color PCSHOW movie made from computed time series data. The steady state and time average catalyst concentration profiles, the slurry height and the rates of methanol production agree well with the measurements obtained at an Air Products` pilot plant.
Silliman, S.E.; Babic, M.
1993-09-28
Sophisticated models of the movement of particles, particularly bacteria and viruses, through porous media have been developed, but have met with limited success when compared to field observations some argue that the poor predictive capabilities of the models are due in part to the fact that most of the sophisticated models are tied to an assumptions of homogeneity within the flow field. In previous work, the structure of random percolation fields has been investigated and suggests application of percolation theory to heterogeneous porous media. One conclusion from this study as applied to particle transport is that as the distribution of pore throat sizes takes on variation in the third dimension, the probability of finding a continuous flow path with large throat size increases. One interpretation of this work, within the current context, leads to an argument that a saturated medium will become more open to transport of particles as the medium takes on three dimensional structure. The central hypothesis of the current project is therefore be stated: Particles which are suspended within the pore fluids of media demonstrating three-dimensional heterogeneities will be transported at higher average velocities and with less trapping than particles which are suspended in the pore fluids of media demonstrating one- or two-dimensional heterogeneities. This dependence on dimension is a function of the dimensional character of the heterogeneity, the length scales of the heterogeneity, the size of the particles, the hydrodynamics of the flow field, the degree of saturation of the medium, and the medium/particle interaction.
Ishii, M.; Revankar, S.T.; Babelli, I.; Lele, S.
1992-06-01
Recently, the safety of low pressure liquid cooled nuclear reactors has become a very important issue with reference to the operation of the heavy water reactors at Savannah River Plant. Under accident conditions such as loss-of-flow or loss-of-coolant, these reactors typically encounter unstable two-phase flow which may lead to the occurrence of dryout and subsequent fuel failure. An analytical study using the one-dimensional drift flux model was carried out to investigate the two-phase flow instability for Westinghouse Savannah River Site reactor. The analysis indicates that the first and higher order instabilities exist in the possible transient operational conditions. The instabilities are encountered at higher heat fluxes or lower flow rates. The subcooling has a stabilizing effect except at very low subcooling. An experimental loop has been designed and constructed to study the CBF induced by various flow instabilities. Details of this test loop are presented. Initial test results have been presented. The two-phase flow regimes and hydrodynamic behaviors in the post dryout region have been studied under propagating rewetting conditions. The effect of subcooling and inlet velocity on flow transition as well as on the quench front propagation was investigated. The test liquid was Freon 113 which was introduced into the bottom of the quartz test section whose walls were maintained well above the film boiling temperature of the test liquid, via a transparent heat transfer fluid. The flow regimes observed down stream of the upward moving quench front were the rough wavy, the agitated, and the dispersed droplet/ligaments. A correlation for the flow regime transition between the inverted annular and the dispersed droplet/ligament flow patterns was developed. The correlation showed a marked dependence on the void fraction at the CBF location and hence on the flow regime encountered in the pre-CBF region.
Dudukovic, M.P.; Fan, L.S.; Chang, Min
1997-05-01
The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research and Engineering Company is to improve the basis for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. The first year of this three year program was spent on developing and tuning the experimental tools that can provide accurate measurement of pertinent hydrodynamic quantities, such as velocity field and holdup distribution, for validation of hydrodynamic models. Advances made in preparing the unique Computer Automated Radioactive Particle Tracing (CARPT) technique for use in high pressure systems are described in this report The work done on developing a reliable beat transfer coefficient measurement probe at operating conditions of interest is also described. Finally, the work done in preparing the Exxon pilot plant facilities for high pressure runs and pertinent hydrodynamic measurements is outlined together with preliminary studies of matching the fluid dynamics program predictions and data in a two dimensional column.
Jashnsaz, Hossein; Al Juboori, Mohammed; Weistuch, Corey; Miller, Nicholas; Nguyen, Tyler; Meyerhoff, Viktoria; McCoy, Bryan; Perkins, Stephanie; Wallgren, Ross; Ray, Bruce D; Tsekouras, Konstantinos; Anderson, Gregory G; Pressé, Steve
2017-03-28
The Gram-negative Bdellovibrio bacteriovorus (BV) is a model bacterial predator that hunts other bacteria and may serve as a living antibiotic. Despite over 50 years since its discovery, it is suggested that BV probably collides into its prey at random. It remains unclear to what degree, if any, BV uses chemical cues to target its prey. The targeted search problem by the predator for its prey in three dimensions is a difficult problem: it requires the predator to sensitively detect prey and forecast its mobile prey's future position on the basis of previously detected signal. Here instead we find that rather than chemically detecting prey, hydrodynamics forces BV into regions high in prey density, thereby improving its odds of a chance collision with prey and ultimately reducing BV's search space for prey. We do so by showing that BV's dynamics are strongly influenced by self-generated hydrodynamic flow fields forcing BV onto surfaces and, for large enough defects on surfaces, forcing BV in orbital motion around these defects. Key experimental controls and calculations recapitulate the hydrodynamic origin of these behaviors. While BV's prey (Escherichia coli) are too small to trap BV in hydrodynamic orbit, the prey are also susceptible to their own hydrodynamic fields, substantially confining them to surfaces and defects where mobile predator and prey density is now dramatically enhanced. Colocalization, driven by hydrodynamics, ultimately reduces BV's search space for prey from three to two dimensions (on surfaces) even down to a single dimension (around defects). We conclude that BV's search for individual prey remains random, as suggested in the literature, but confined, however-by generic hydrodynamic forces-to reduced dimensionality.
ERIC Educational Resources Information Center
Lafrance, Pierre
1978-01-01
Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)
Castor, J I
2003-10-16
The discipline of radiation hydrodynamics is the branch of hydrodynamics in which the moving fluid absorbs and emits electromagnetic radiation, and in so doing modifies its dynamical behavior. That is, the net gain or loss of energy by parcels of the fluid material through absorption or emission of radiation are sufficient to change the pressure of the material, and therefore change its motion; alternatively, the net momentum exchange between radiation and matter may alter the motion of the matter directly. Ignoring the radiation contributions to energy and momentum will give a wrong prediction of the hydrodynamic motion when the correct description is radiation hydrodynamics. Of course, there are circumstances when a large quantity of radiation is present, yet can be ignored without causing the model to be in error. This happens when radiation from an exterior source streams through the problem, but the latter is so transparent that the energy and momentum coupling is negligible. Everything we say about radiation hydrodynamics applies equally well to neutrinos and photons (apart from the Einstein relations, specific to bosons), but in almost every area of astrophysics neutrino hydrodynamics is ignored, simply because the systems are exceedingly transparent to neutrinos, even though the energy flux in neutrinos may be substantial. Another place where we can do ''radiation hydrodynamics'' without using any sophisticated theory is deep within stars or other bodies, where the material is so opaque to the radiation that the mean free path of photons is entirely negligible compared with the size of the system, the distance over which any fluid quantity varies, and so on. In this case we can suppose that the radiation is in equilibrium with the matter locally, and its energy, pressure and momentum can be lumped in with those of the rest of the fluid. That is, it is no more necessary to distinguish photons from atoms, nuclei and electrons, than it is to distinguish
NASA Astrophysics Data System (ADS)
Lauga, Eric
2016-01-01
Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells, yet they represent the bulk of the world's biomass and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micrometer scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically complex environments. Using hydrodynamics as an organizing framework, I review the biomechanics of bacterial motility and look ahead to future challenges.
NASA Astrophysics Data System (ADS)
Tsubota, Makoto; Kobayashi, Michikazu; Takeuchi, Hiromitsu
2013-01-01
Quantum hydrodynamics in superfluid helium and atomic Bose-Einstein condensates (BECs) has been recently one of the most important topics in low temperature physics. In these systems, a macroscopic wave function (order parameter) appears because of Bose-Einstein condensation, which creates quantized vortices. Turbulence consisting of quantized vortices is called quantum turbulence (QT). The study of quantized vortices and QT has increased in intensity for two reasons. The first is that recent studies of QT are considerably advanced over older studies, which were chiefly limited to thermal counterflow in 4He, which has no analog with classical traditional turbulence, whereas new studies on QT are focused on a comparison between QT and classical turbulence. The second reason is the realization of atomic BECs in 1995, for which modern optical techniques enable the direct control and visualization of the condensate and can even change the interaction; such direct control is impossible in other quantum condensates like superfluid helium and superconductors. Our group has made many important theoretical and numerical contributions to the field of quantum hydrodynamics of both superfluid helium and atomic BECs. In this article, we review some of the important topics in detail. The topics of quantum hydrodynamics are diverse, so we have not attempted to cover all these topics in this article. We also ensure that the scope of this article does not overlap with our recent review article (arXiv:1004.5458), “Quantized vortices in superfluid helium and atomic Bose-Einstein condensates”, and other review articles.
Chabchoub, A; Hoffmann, N; Onorato, M; Genty, G; Dudley, J M; Akhmediev, N
2013-08-02
We report the experimental observation of multi-bound-soliton solutions of the nonlinear Schrödinger equation (NLS) in the context of hydrodynamic surface gravity waves. Higher-order N-soliton solutions with N=2, 3 are studied in detail and shown to be associated with self-focusing in the wave group dynamics and the generation of a steep localized carrier wave underneath the group envelope. We also show that for larger input soliton numbers, the wave group experiences irreversible spectral broadening, which we refer to as a hydrodynamic supercontinuum by analogy with optics. This process is shown to be associated with the fission of the initial multisoliton into individual fundamental solitons due to higher-order nonlinear perturbations to the NLS. Numerical simulations using an extended NLS model described by the modified nonlinear Schrödinger equation, show excellent agreement with experiment and highlight the universal role that higher-order nonlinear perturbations to the NLS play in supercontinuum generation.
Bruinsma, Robijn; Grosberg, Alexander Y; Rabin, Yitzhak; Zidovska, Alexandra
2014-05-06
Following recent observations of large scale correlated motion of chromatin inside the nuclei of live differentiated cells, we present a hydrodynamic theory-the two-fluid model-in which the content of a nucleus is described as a chromatin solution with the nucleoplasm playing the role of the solvent and the chromatin fiber that of a solute. This system is subject to both passive thermal fluctuations and active scalar and vector events that are associated with free energy consumption, such as ATP hydrolysis. Scalar events drive the longitudinal viscoelastic modes (where the chromatin fiber moves relative to the solvent) while vector events generate the transverse modes (where the chromatin fiber moves together with the solvent). Using linear response methods, we derive explicit expressions for the response functions that connect the chromatin density and velocity correlation functions to the corresponding correlation functions of the active sources and the complex viscoelastic moduli of the chromatin solution. We then derive general expressions for the flow spectral density of the chromatin velocity field. We use the theory to analyze experimental results recently obtained by one of the present authors and her co-workers. We find that the time dependence of the experimental data for both native and ATP-depleted chromatin can be well-fitted using a simple model-the Maxwell fluid-for the complex modulus, although there is some discrepancy in terms of the wavevector dependence. Thermal fluctuations of ATP-depleted cells are predominantly longitudinal. ATP-active cells exhibit intense transverse long wavelength velocity fluctuations driven by force dipoles. Fluctuations with wavenumbers larger than a few inverse microns are dominated by concentration fluctuations with the same spectrum as thermal fluctuations but with increased intensity.
Pedersen, Lea; Wogensen, Lise; Marcussen, Niels; Cecchi, Claudia R; Dalsgaard, Trine; Dagnæs-Hansen, Frederik
2015-01-01
Erythropoietin, Epo, is a 30.4 kDa glycoprotein hormone produced primarily by the fetal liver and the adult kidney. Epo exerts its haematopoietic effects by stimulating the proliferation and differentiation of erythrocytes with subsequent improved tissue oxygenation. Epo receptors are furthermore expressed in non-haematopoietic tissue and today, Epo is recognised as a cytokine with many pleiotropic effects. We hypothesize that hydrodynamic gene therapy with Epo can restore haemoglobin levels in anaemic transgenic mice and that this will attenuate the extracellular matrix accumulation in the kidneys. The experiment is conducted by hydrodynamic gene transfer of a plasmid encoding murine Epo in a transgenic mouse model that overexpresses TGF-β1 locally in the kidneys. This model develops anaemia due to chronic kidney disease characterised by thickening of the glomerular basement membrane, deposition of mesangial matrix and mild interstitial fibrosis. A group of age matched wildtype littermates are treated accordingly. After a single hydrodynamic administration of plasmid DNA containing murine EPO gene, sustained high haemoglobin levels are observed in both transgenic and wildtype mice from 7.5 ± 0.6 mmol/L to 9.4 ± 1.2 mmol/L and 10.7 ± 0.3 mmol/L to 15.5 ± 0.5 mmol/L, respectively. We did not observe any effects in the thickness of glomerular or tubular basement membrane, on the expression of different collagen types in the kidneys or in kidney function after prolonged treatment with Epo. Thus, Epo treatment in this model of chronic kidney disease normalises haemoglobin levels but has no effect on kidney fibrosis or function.
HYDRODYNAMIC COMPRESSIVE FORGING.
HYDRODYNAMICS), (*FORGING, COMPRESSIVE PROPERTIES, LUBRICANTS, PERFORMANCE(ENGINEERING), DIES, TENSILE PROPERTIES, MOLYBDENUM ALLOYS , STRAIN...MECHANICS), BERYLLIUM ALLOYS , NICKEL ALLOYS , CASTING ALLOYS , PRESSURE, FAILURE(MECHANICS).
Resurgence in extended hydrodynamics
NASA Astrophysics Data System (ADS)
Aniceto, Inês; Spaliński, Michał
2016-04-01
It has recently been understood that the hydrodynamic series generated by the Müller-Israel-Stewart theory is divergent and that this large-order behavior is consistent with the theory of resurgence. Furthermore, it was observed that the physical origin of this is the presence of a purely damped nonhydrodynamic mode. It is very interesting to ask whether this picture persists in cases where the spectrum of nonhydrodynamic modes is richer. We take the first step in this direction by considering the simplest hydrodynamic theory which, instead of the purely damped mode, contains a pair of nonhydrodynamic modes of complex conjugate frequencies. This mimics the pattern of black brane quasinormal modes which appear on the gravity side of the AdS/CFT description of N =4 supersymmetric Yang-Mills plasma. We find that the resulting hydrodynamic series is divergent in a way consistent with resurgence and precisely encodes information about the nonhydrodynamic modes of the theory.
Smoothed Particle Hydrodynamic Simulator
2016-10-05
This code is a highly modular framework for developing smoothed particle hydrodynamic (SPH) simulations running on parallel platforms. The compartmentalization of the code allows for rapid development of new SPH applications and modifications of existing algorithms. The compartmentalization also allows changes in one part of the code used by many applications to instantly be made available to all applications.
Skew resisting hydrodynamic seal
Conroy, William T.; Dietle, Lannie L.; Gobeli, Jeffrey D.; Kalsi, Manmohan S.
2001-01-01
A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing material, provides a relatively stiff integral spring effect to minimize pressure-induced shuttling of the seal within the gland, and also maintains interfacial contact pressure within the dynamic sealing interface in an optimum range for efficient hydrodynamic lubrication and environment exclusion. The seal geometry also provides for complete support about the circumference of the seal to receive environmental pressure, as compared the interrupted character of seal support set forth in U.S. Pat. Nos. 5,873,576 and 6,036,192 and provides a hydrodynamic seal which is suitable for use with non-Newtonian lubricants.
Hydrodynamics of Turning Flocks.
Yang, Xingbo; Marchetti, M Cristina
2015-12-18
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The continuum equations controlled by only two dimensionless parameters, orientational inertia and alignment strength, are derived by coarse-graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields anisotropic spin waves that mediate the propagation of turning information throughout the flock. The coupling between spin-current density to the local vorticity field through a nonlinear friction gives rise to a hydrodynamic mode with angular-dependent propagation speed at long wavelengths. This mode becomes unstable as a result of the growth of bend and splay deformations augmented by the spin wave, signaling the transition to complex spatiotemporal patterns of continuously turning and swirling flocks.
Hydrodynamics of Turning Flocks
NASA Astrophysics Data System (ADS)
Yang, Xingbo; Marchetti, M. Cristina
2015-12-01
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The continuum equations controlled by only two dimensionless parameters, orientational inertia and alignment strength, are derived by coarse-graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields anisotropic spin waves that mediate the propagation of turning information throughout the flock. The coupling between spin-current density to the local vorticity field through a nonlinear friction gives rise to a hydrodynamic mode with angular-dependent propagation speed at long wavelengths. This mode becomes unstable as a result of the growth of bend and splay deformations augmented by the spin wave, signaling the transition to complex spatiotemporal patterns of continuously turning and swirling flocks.
Hydrodynamics of fossil fishes
Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert
2014-01-01
From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms. PMID:24943377
Hydrodynamics of insect spermatozoa
NASA Astrophysics Data System (ADS)
Pak, On Shun; Lauga, Eric
2010-11-01
Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.
Hydrodynamics of fossil fishes.
Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert
2014-08-07
From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.
Numerical Hydrodynamics and Magnetohydrodynamics in General Relativity.
Font, José A
2008-01-01
This article presents a comprehensive overview of numerical hydrodynamics and magneto-hydrodynamics (MHD) in general relativity. Some significant additions have been incorporated with respect to the previous two versions of this review (2000, 2003), most notably the coverage of general-relativistic MHD, a field in which remarkable activity and progress has occurred in the last few years. Correspondingly, the discussion of astrophysical simulations in general-relativistic hydrodynamics is enlarged to account for recent relevant advances, while those dealing with general-relativistic MHD are amply covered in this review for the first time. The basic outline of this article is nevertheless similar to its earlier versions, save for the addition of MHD-related issues throughout. Hence, different formulations of both the hydrodynamics and MHD equations are presented, with special mention of conservative and hyperbolic formulations well adapted to advanced numerical methods. A large sample of numerical approaches for solving such hyperbolic systems of equations is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. As previously stated, a comprehensive summary of astrophysical simulations in strong gravitational fields is also presented. These are detailed in three basic sections, namely gravitational collapse, black-hole accretion, and neutron-star evolutions; despite the boundaries, these sections may (and in fact do) overlap throughout the discussion. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances in the formulation of the gravitational field, hydrodynamics and MHD equations and the numerical methodology designed to solve them. To keep the length of this article reasonable, an effort has
Hydrodynamics of Ship Propellers
NASA Astrophysics Data System (ADS)
Breslin, John P.; Andersen, Poul
1996-11-01
This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and movements that the propeller generates on the shaft and on the ship hull. The first part of the book is devoted to fundamentals of the flow about hydrofoil sections and wings, and to propellers in uniform flow, with guidance for design and pragmatic analysis of performance. The second part covers the development of unsteady forces arising from operation in nonuniform hull wakes. A final chapter discusses the optimization of efficiency of compound propulsors. Researchers in ocean technology and naval architecture will find this book appealing.
How to fake hydrodynamic signals
NASA Astrophysics Data System (ADS)
Romatschke, Paul
2016-12-01
Flow signatures in experimental data from relativistic ion collisions, are usually interpreted as a fingerprint of the presence of a hydrodynamic phase during the evolution of these systems. I review some theoretical ideas to 'fake' this hydrodynamic behavior in p+A and A+A collisions. I find that transverse flow and femtoscopic measurements can easily be forged through non-hydrodynamic evolution, while large elliptic flow requires some non-vanishing interactions in the hot phase.
Hydrodynamic synchronization of flagellar oscillators
NASA Astrophysics Data System (ADS)
Friedrich, Benjamin
2016-11-01
In this review, we highlight the physics of synchronization in collections of beating cilia and flagella. We survey the nonlinear dynamics of synchronization in collections of noisy oscillators. This framework is applied to flagellar synchronization by hydrodynamic interactions. The time-reversibility of hydrodynamics at low Reynolds numbers requires swimming strokes that break time-reversal symmetry to facilitate hydrodynamic synchronization. We discuss different physical mechanisms for flagellar synchronization, which break this symmetry in different ways.
Molecular Hydrodynamics from Memory Kernels
NASA Astrophysics Data System (ADS)
Lesnicki, Dominika; Vuilleumier, Rodolphe; Carof, Antoine; Rotenberg, Benjamin
2016-04-01
The memory kernel for a tagged particle in a fluid, computed from molecular dynamics simulations, decays algebraically as t-3 /2 . We show how the hydrodynamic Basset-Boussinesq force naturally emerges from this long-time tail and generalize the concept of hydrodynamic added mass. This mass term is negative in the present case of a molecular solute, which is at odds with incompressible hydrodynamics predictions. Lastly, we discuss the various contributions to the friction, the associated time scales, and the crossover between the molecular and hydrodynamic regimes upon increasing the solute radius.
Hydrodynamics of Bacterial Cooperation
NASA Astrophysics Data System (ADS)
Petroff, A.; Libchaber, A.
2012-12-01
Over the course of the last several decades, the study of microbial communities has identified countless examples of cooperation between microorganisms. Generally—as in the case of quorum sensing—cooperation is coordinated by a chemical signal that diffuses through the community. Less well understood is a second class of cooperation that is mediated through physical interactions between individuals. To better understand how the bacteria use hydrodynamics to manipulate their environment and coordinate their actions, we study the sulfur-oxidizing bacterium Thiovulum majus. These bacteria live in the diffusive boundary layer just above the muddy bottoms of ponds. As buried organic material decays, sulfide diffuses out of the mud. Oxygen from the pond diffuses into the boundary layer from above. These bacteria form communities—called veils— which are able to transport nutrients through the boundary layer faster than diffusion, thereby increasing their metabolic rate. In these communities, bacteria attach to surfaces and swim in place. As millions of bacteria beat their flagella, the community induces a macroscopic fluid flow, which mix the boundary layer. Here we present experimental observations and mathematical models that elucidate the hydrodynamics linking the behavior of an individual bacterium to the collective dynamics of the community. We begin by characterizing the flow of water around an individual bacterium swimming in place. We then discuss the flow of water and nutrients around a small number of individuals. Finally, we present observations and models detailing the macroscopic dynamics of a Thiovulum veil.
Load responsive hydrodynamic bearing
Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.
2002-01-01
A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.
NASA Astrophysics Data System (ADS)
Bush, John W. M.
2015-01-01
Yves Couder, Emmanuel Fort, and coworkers recently discovered that a millimetric droplet sustained on the surface of a vibrating fluid bath may self-propel through a resonant interaction with its own wave field. This article reviews experimental evidence indicating that the walking droplets exhibit certain features previously thought to be exclusive to the microscopic, quantum realm. It then reviews theoretical descriptions of this hydrodynamic pilot-wave system that yield insight into the origins of its quantum-like behavior. Quantization arises from the dynamic constraint imposed on the droplet by its pilot-wave field, and multimodal statistics appear to be a feature of chaotic pilot-wave dynamics. I attempt to assess the potential and limitations of this hydrodynamic system as a quantum analog. This fluid system is compared to quantum pilot-wave theories, shown to be markedly different from Bohmian mechanics and more closely related to de Broglie's original conception of quantum dynamics, his double-solution theory, and its relatively recent extensions through researchers in stochastic electrodynamics.
General formulation of transverse hydrodynamics
Ryblewski, Radoslaw; Florkowski, Wojciech
2008-06-15
General formulation of hydrodynamics describing transversally thermalized matter created at the early stages of ultrarelativistic heavy-ion collisions is presented. Similarities and differences with the standard three-dimensionally thermalized relativistic hydrodynamics are discussed. The role of the conservation laws as well as the thermodynamic consistency of two-dimensional thermodynamic variables characterizing transversally thermalized matter is emphasized.
Hydrocyclone separation hydrodynamics
Ivanov, A.A.; Ruzanov, S.R.; Lunyushkina, I.A.
1987-10-20
The lack of an adequate hydrodynamic model for a hydrocyclone has so far been the main obstacle to devising a general method for designing such apparatus. The authors present a method of calculating the liquid flow in the working zone. The results have been used to calculate the separating power in application to dilute suspensions. The Navier-Stokes equations and the equation of continuity are used in examining the behavior together with assumptions based on experiment: the conditions for stationary axisymmetric flow, constant turbulent viscosity, and a constant radial profile for the tangential low speed at all the heights. The boundary conditions are those for liquid slip at the side walls and absence of vortex drainage at the axis. The results enable one to choose the dimensions for particular separations.
Synchronization and hydrodynamic interactions
NASA Astrophysics Data System (ADS)
Powers, Thomas; Qian, Bian; Breuer, Kenneth
2008-03-01
Cilia and flagella commonly beat in a coordinated manner. Examples include the flagella that Volvox colonies use to move, the cilia that sweep foreign particles up out of the human airway, and the nodal cilia that set up the flow that determines the left-right axis in developing vertebrate embryos. In this talk we present an experimental study of how hydrodynamic interactions can lead to coordination in a simple idealized system: two nearby paddles driven with fixed torques in a highly viscous fluid. The paddles attain a synchronized state in which they rotate together with a phase difference of 90 degrees. We discuss how synchronization depends on system parameters and present numerical calculations using the method of regularized stokeslets.
Hydrodynamics, resurgence, and transasymptotics
NASA Astrophysics Data System (ADS)
Başar, Gökçe; Dunne, Gerald V.
2015-12-01
The second order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost-invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the nonhydrodynamic modes that are exponentially suppressed at late times, analogous to the quasinormal modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semiclassical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these nonhydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with initial conditions.
Hydrodynamics of Turning Flocks
NASA Astrophysics Data System (ADS)
Yang, Xingbo; Marchetti, M. Cristina
2015-03-01
We present a hydrodynamic model of flocking that generalizes the familiar Toner-Tu equations to incorporate turning inertia of well polarized flocks. The continuum equations are derived by coarse graining the inertial spin model recently proposed by Cavagna et al. The interplay between orientational inertia and bend elasticity of the flock yields spin waves that mediate the propagation of turning information throughout the flock. When the inertia is large, we find a novel instability that signals the transition to complex spatio-temporal patterns of continuously turning and swirling flocks. This work was supported by the NSF Awards DMR-1305184 and DGE-1068780 at Syracuse University and NSF Award PHY11-25915 and the Gordon and Betty Moore Foundation Grant No. 2919 at the KITP at the University of California, Santa Barbara.
Hydrodynamics of Peristaltic Propulsion
NASA Astrophysics Data System (ADS)
Athanassiadis, Athanasios; Hart, Douglas
2014-11-01
A curious class of animals called salps live in marine environments and self-propel by ejecting vortex rings much like jellyfish and squid. However, unlike other jetting creatures that siphon and eject water from one side of their body, salps produce vortex rings by pumping water through siphons on opposite ends of their hollow cylindrical bodies. In the simplest cases, it seems like some species of salp can successfully move by contracting just two siphons connected by an elastic body. When thought of as a chain of timed contractions, salp propulsion is reminiscent of peristaltic pumping applied to marine locomotion. Inspired by salps, we investigate the hydrodynamics of peristaltic propulsion, focusing on the scaling relationships that determine flow rate, thrust production, and energy usage in a model system. We discuss possible actuation methods for a model peristaltic vehicle, considering both the material and geometrical requirements for such a system.
Hydrodynamic effects on coalescence.
Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael; Gorby, Allen D.; Brooks, Carlton, F.
2006-10-01
The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.
Hydrodynamics of sediment threshold
NASA Astrophysics Data System (ADS)
Ali, Sk Zeeshan; Dey, Subhasish
2016-07-01
A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.
Hydrodynamical noise and Gubser flow
NASA Astrophysics Data System (ADS)
Yan, Li; Grönqvist, Hanna
2016-03-01
Hydrodynamical noise is introduced on top of Gubser's analytical solution to viscous hydrodynamics. With respect to the ultra-central collision events of Pb-Pb, p-Pb and p-p at the LHC energies, we solve the evolution of noisy fluid systems and calculate the radial flow velocity correlations. We show that the absolute amplitude of the hydrodynamical noise is determined by the multiplicity of the collision event. The evolution of azimuthal anisotropies, which is related to the generation of harmonic flow, receives finite enhancements from hydrodynamical noise. Although it is strongest in the p-p systems, the effect of hydrodynamical noise on flow harmonics is found to be negligible, especially in the ultra-central Pb-Pb collisions. For the short-range correlations, hydrodynamical noise contributes to the formation of a near-side peak on top of the correlation structure originated from initial state fluctuations. The shape of the peak is affected by the strength of hydrodynamical noise, whose height and width grow from the Pb-Pb system to the p-Pb and p-p systems.
Recent development of hydrodynamic modeling
NASA Astrophysics Data System (ADS)
Hirano, Tetsufumi
2014-09-01
In this talk, I give an overview of recent development in hydrodynamic modeling of high-energy nuclear collisions. First, I briefly discuss about current situation of hydrodynamic modeling by showing results from the integrated dynamical approach in which Monte-Carlo calculation of initial conditions, quark-gluon fluid dynamics and hadronic cascading are combined. In particular, I focus on rescattering effects of strange hadrons on final observables. Next I highlight three topics in recent development in hydrodynamic modeling. These include (1) medium response to jet propagation in di-jet asymmetric events, (2) causal hydrodynamic fluctuation and its application to Bjorken expansion and (3) chiral magnetic wave from anomalous hydrodynamic simulations. (1) Recent CMS data suggest the existence of QGP response to propagation of jets. To investigate this phenomenon, we solve hydrodynamic equations with source term which exhibits deposition of energy and momentum from jets. We find a large number of low momentum particles are emitted at large angle from jet axis. This gives a novel interpretation of the CMS data. (2) It has been claimed that a matter created even in p-p/p-A collisions may behave like a fluid. However, fluctuation effects would be important in such a small system. We formulate relativistic fluctuating hydrodynamics and apply it to Bjorken expansion. We found the final multiplicity fluctuates around the mean value even if initial condition is fixed. This effect is relatively important in peripheral A-A collisions and p-p/p-A collisions. (3) Anomalous transport of the quark-gluon fluid is predicted when extremely high magnetic field is applied. We investigate this possibility by solving anomalous hydrodynamic equations. We found the difference of the elliptic flow parameter between positive and negative particles appears due to the chiral magnetic wave. Finally, I provide some personal perspective of hydrodynamic modeling of high energy nuclear collisions
Special Relativistic Hydrodynamics with Gravitation
NASA Astrophysics Data System (ADS)
Hwang, Jai-chan; Noh, Hyerim
2016-12-01
Special relativistic hydrodynamics with weak gravity has hitherto been unknown in the literature. Whether such an asymmetric combination is possible has been unclear. Here, the hydrodynamic equations with Poisson-type gravity, considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit, are consistently derived from Einstein’s theory of general relativity. An analysis is made in the maximal slicing, where the Poisson’s equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the general hypersurface condition. Our formulation includes the anisotropic stress.
Constraining relativistic viscous hydrodynamical evolution
Martinez, Mauricio; Strickland, Michael
2009-04-15
We show that by requiring positivity of the longitudinal pressure it is possible to constrain the initial conditions one can use in second-order viscous hydrodynamical simulations of ultrarelativistic heavy-ion collisions. We demonstrate this explicitly for (0+1)-dimensional viscous hydrodynamics and discuss how the constraint extends to higher dimensions. Additionally, we present an analytic approximation to the solution of (0+1)-dimensional second-order viscous hydrodynamical evolution equations appropriate to describe the evolution of matter in an ultrarelativistic heavy-ion collision.
Image-Guided Hydrodynamic Gene Delivery: Current Status and Future Directions
Kamimura, Kenya; Yokoo, Takeshi; Abe, Hiroyuki; Kobayashi, Yuji; Ogawa, Kohei; Shinagawa, Yoko; Inoue, Ryosuke; Terai, Shuji
2015-01-01
Hydrodynamics-based delivery has been used as an experimental tool to express transgene in small animals. This in vivo gene transfer method is useful for functional analysis of genetic elements, therapeutic effect of oligonucleotides, and cancer cells to establish the metastatic cancer animal model for experimental research. Recent progress in the development of image-guided procedure for hydrodynamics-based gene delivery in large animals directly supports the clinical applicability of this technique. This review summarizes the current status and recent progress in the development of hydrodynamics-based gene delivery and discusses the future directions for its clinical application. PMID:26308044
Hydrodynamics of soft active matter
NASA Astrophysics Data System (ADS)
Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi
2013-07-01
This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.
Lotic Water Hydrodynamic Model
Judi, David Ryan; Tasseff, Byron Alexander
2015-01-23
Water-related natural disasters, for example, floods and droughts, are among the most frequent and costly natural hazards, both socially and economically. Many of these floods are a result of excess rainfall collecting in streams and rivers, and subsequently overtopping banks and flowing overland into urban environments. Floods can cause physical damage to critical infrastructure and present health risks through the spread of waterborne diseases. Los Alamos National Laboratory (LANL) has developed Lotic, a state-of-the-art surface water hydrodynamic model, to simulate propagation of flood waves originating from a variety of events. Lotic is a two-dimensional (2D) flood model that has been used primarily for simulations in which overland water flows are characterized by movement in two dimensions, such as flood waves expected from rainfall-runoff events, storm surge, and tsunamis. In 2013, LANL developers enhanced Lotic through several development efforts. These developments included enhancements to the 2D simulation engine, including numerical formulation, computational efficiency developments, and visualization. Stakeholders can use simulation results to estimate infrastructure damage and cascading consequences within other sets of infrastructure, as well as to inform the development of flood mitigation strategies.
Astrophysical smooth particle hydrodynamics
NASA Astrophysics Data System (ADS)
Rosswog, Stephan
2009-04-01
The paper presents a detailed review of the smooth particle hydrodynamics (SPH) method with particular focus on its astrophysical applications. We start by introducing the basic ideas and concepts and thereby outline all ingredients that are necessary for a practical implementation of the method in a working SPH code. Much of SPH's success relies on its excellent conservation properties and therefore the numerical conservation of physical invariants receives much attention throughout this review. The self-consistent derivation of the SPH equations from the Lagrangian of an ideal fluid is the common theme of the remainder of the text. We derive a modern, Newtonian SPH formulation from the Lagrangian of an ideal fluid. It accounts for changes of the local resolution lengths which result in corrective, so-called "grad-h-terms". We extend this strategy to special relativity for which we derive the corresponding grad-h equation set. The variational approach is further applied to a general-relativistic fluid evolving in a fixed, curved background space-time. Particular care is taken to explicitly derive all relevant equations in a coherent way.
Reciprocal relations in dissipationless hydrodynamics
Melnikovsky, L. A.
2014-12-15
Hidden symmetry in dissipationless terms of arbitrary hydrodynamics equations is recognized. We demonstrate that all fluxes are generated by a single function and derive conventional Euler equations using the proposed formalism.
Slurry bubble column hydrodynamics
NASA Astrophysics Data System (ADS)
Rados, Novica
Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids
The hydrodynamics of colloidal gelation.
Varga, Zsigmond; Wang, Gang; Swan, James
2015-12-14
Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions.
Group-invariant solutions of hydrodynamics and radiation hydrodynamics
Coggeshall, S.V.
1993-08-01
Using the property of invariance under Lie groups of transformations, the equations of hydrodynamics are transformed from partial differential equations to ordinary differential equations, for which special analytic solutions can be found. These particular solutions can be used for (1) numerical benchmarks, (2) the basis for analytic models, and (3) insight into more general solutions. Additionally, group transformations can be used to construct new solutions from existing ones. A space-time projective group is used to generate complicated solutions from simpler solutions. Discussion of these procedures is presented along with examples of analytic of 1,2 and 3-D hydrodynamics.
Numerical Hydrodynamics in Special Relativity.
Martí, José Maria; Müller, Ewald
2003-01-01
This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.
Hydrodynamic behavior of fractal aggregates
NASA Astrophysics Data System (ADS)
Wiltzius, Pierre
1987-02-01
Measurements of the radius of gyration RG and the hydrodynamic radius RH of colloidal silica aggregates are reported. These aggregates have fractal geometry and RH is proportional to RG for 500 Å<=RH<=7000 Å, with a ratio RH/RG=0.72+/-0.02. The results are compared with predictions for macromolecules of various shapes. The proportionality of the two radii can be understood with use of the pair correlation function of fractal objects and hydrodynamic interactions on the Oseen level. The value of the ratio remains to be explained.
Abnormal pressures as hydrodynamic phenomena
Neuzil, C.E.
1995-01-01
So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author
Hydrodynamically mediated macrophyte silica dynamics.
Schoelynck, J; Bal, K; Puijalon, S; Meire, P; Struyf, E
2012-11-01
In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distributions and abundance of aquatic plants. Resisting stress and keeping an upright position often relies on investment in tissue reinforcement, which is costly to produce. Silica could provide a more economical alternative. Two laboratory experiments were conducted to measure the response of two submerged species, Egeria densa Planch. and Limnophila heterophylla (Roxb.) Benth., to dissolved silicic acid availability and exposure to hydrodynamic stress. The results were verified with a third species in a field study (Nuphar lutea (L.) Smith). Biogenic silica (BSi) concentration in both stems and leaves increases with increasing dissolved silica availability but also with the presence of hydrodynamic stress. We suggest that the inclusion of extra silica enables the plant to alternatively invest its energy in the production of lignin and cellulose. Although we found no significant effects of hydrodynamic stress on cellulose or lignin concentrations either in the laboratory or in the field, BSi was negatively correlated with cellulose concentration and positively correlated with lignin concentration in samples collected in the field study. This implies that the plant might perform with equal energy efficiency in both standing and running water environments. This could provide submerged species with a tool to respond to abiotic factors, to adapt to new ecological conditions and hence potentially colonise new environments.
Hydrodynamic slip in silicon nanochannels
NASA Astrophysics Data System (ADS)
Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.
2016-03-01
Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.
Anomalous hydrodynamics of fractional quantum Hall states
Wiegmann, P.
2013-09-15
We propose a comprehensive framework for quantum hydrodynamics of the fractional quantum Hall (FQH) states. We suggest that the electronic fluid in the FQH regime can be phenomenologically described by the quantized hydrodynamics of vortices in an incompressible rotating liquid. We demonstrate that such hydrodynamics captures all major features of FQH states, including the subtle effect of the Lorentz shear stress. We present a consistent quantization of the hydrodynamics of an incompressible fluid, providing a powerful framework to study the FQH effect and superfluids. We obtain the quantum hydrodynamics of the vortex flow by quantizing the Kirchhoff equations for vortex dynamics.
Hydrodynamical Modeling of the Local Interstellar Medium
NASA Astrophysics Data System (ADS)
Slavin, Jonathan David
2017-01-01
Studies of the Local Interstellar Medium (LISM) provide us with the opportunity to make progress in understanding a wide range of physical processes that operate in the diffuse insterstellar medium (ISM) of galaxies. The LISM includes a large bubble of hot, supernova created gas, known as the Local Bubble, and several low density, warm clouds close to the Sun, known as the Complex of Local Insterstellar Clouds (CLIC). The CLIC includes the Local Interstellar Cloud that surrounds and confines the heliosphere and is the source of neutral H and He that has been detected flowing into the Solar System. Several important questions remain unanswered about the LISM including how the Local Bubble formed, how the CLIC got to be inside the Local Bubble, and what are the ongoing interactions of the hot gas with the CLIC gas. We report on our progress in creating numerical hydrodynamical models of the LISM that aim to help us to understand the wide range of observations we have of the CLIC and the Local Bubble and the origins and evolution of the LISM.
Hydrodynamics from Landau initial conditions
Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read jr, Kenneth F.; Wong, Cheuk-Yin
2015-01-01
We investigate ideal hydrodynamic evolution, with Landau initial conditions, both in a semi-analytical 1+1D approach and in a numerical code incorporating event-by-event variation with many events and transverse density inhomogeneities. The object of the calculation is to test how fast would a Landau initial condition transition to a commonly used boost-invariant expansion. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of O (20 - 30%) expected at freezeout for most scenarios. Moreover, the deviation from boost-invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, 2+1 dimensional hydrodynamics is inadequate to extract transport coefficients of the quark-gluon plasma. Based on [1, 2
Microscopic derivation of discrete hydrodynamics.
Español, Pep; Anero, Jesús G; Zúñiga, Ignacio
2009-12-28
By using the standard theory of coarse graining based on Zwanzig's projection operator, we derive the dynamic equations for discrete hydrodynamic variables. These hydrodynamic variables are defined in terms of the Delaunay triangulation. The resulting microscopically derived equations can be understood, a posteriori, as a discretization on an arbitrary irregular grid of the Navier-Stokes equations. The microscopic derivation provides a set of discrete equations that exactly conserves mass, momentum, and energy and the dissipative part of the dynamics produces strict entropy increase. In addition, the microscopic derivation provides a practical implementation of thermal fluctuations in a way that the fluctuation-dissipation theorem is satisfied exactly. This paper points toward a close connection between coarse-graining procedures from microscopic dynamics and discretization schemes for partial differential equations.
Algorithm refinement for fluctuating hydrodynamics
Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.
2007-07-03
This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.
Hydrodynamic Viscosity in Accretion Disks
NASA Astrophysics Data System (ADS)
Duschl, Wolfgang J.; Strittmatter, Peter A.; Biermann, Peter L.
We propose a generalized accretion disk viscosity prescription based on hydrodynamically driven turbulence at the critical effective Reynolds number. This approach is consistent with recent re-analysis by Richard & Zahn (1999) of experimental results on turbulent Couette-Taylor flows. This new β-viscosity formulation applies to both selfgravitating and non-selfgravitating disks and is shown to yield the standard α-disk prescription in the case of shock dissipation limited, non-selfgravitating disks.
Hydrodynamic Simulations of Planetary Rings
NASA Astrophysics Data System (ADS)
Miller, Jacob; Stewart, G. R.; Esposito, L. W.
2013-10-01
Simulations of rings have traditionally been done using N-body methods, granting insight into the interactions of individual ring particles on varying scales. However, due to the scale of a typical ring system and the sheer number of particles involved, a global N-body simulation is too computationally expensive, unless particle collisions are replaced by stochastic forces (Bromley & Kenyon, 2013). Rings are extraordinarily flat systems and therefore are well-suited to existing geophysical shallow-water hydrodynamics models with well-established non-linear advection methods. By adopting a general relationship between pressure and surface density such as a polytropic equation of state, we can modify the shallow-water formula to treat a thin, compressible, self-gravitating, shearing fluid. Previous hydrodynamic simulations of planetary rings have been restricted to axisymmetric flows and therefore have not treated the response to nonaxisymmetric perturbations by moons (Schmidt & Tscharnuter 1999, Latter & Ogilvie 2010). We seek to expand on existing hydrodynamic methods and, by comparing our work with complementary N-body simulations and Cassini observations, confirm the veracity of our results at small scales before eventually moving to a global domain size. We will use non-Newtonian, dynamically variable viscosity to model the viscous transport caused by unresolved self-gravity wakes. Self-gravity will be added to model the dynamics of large-scale structures, such as density waves and edge waves. Support from NASA Outer Planets and Planetary Geology and Geophysics programs is gratefully acknowledged.
Particle hydrodynamics with tessellation techniques
NASA Astrophysics Data System (ADS)
Heß, Steffen; Springel, Volker
2010-08-01
Lagrangian smoothed particle hydrodynamics (SPH) is a well-established approach to model fluids in astrophysical problems, thanks to its geometric flexibility and ability to automatically adjust the spatial resolution to the clumping of matter. However, a number of recent studies have emphasized inaccuracies of SPH in the treatment of fluid instabilities. The origin of these numerical problems can be traced back to spurious surface effects across contact discontinuities, and to SPH's inherent prevention of mixing at the particle level. We here investigate a new fluid particle model where the density estimate is carried out with the help of an auxiliary mesh constructed as the Voronoi tessellation of the simulation particles instead of an adaptive smoothing kernel. This Voronoi-based approach improves the ability of the scheme to represent sharp contact discontinuities. We show that this eliminates spurious surface tension effects present in SPH and that play a role in suppressing certain fluid instabilities. We find that the new `Voronoi Particle Hydrodynamics' (VPH) described here produces comparable results to SPH in shocks, and better ones in turbulent regimes of pure hydrodynamical simulations. We also discuss formulations of the artificial viscosity needed in this scheme and how judiciously chosen correction forces can be derived in order to maintain a high degree of particle order and hence a regular Voronoi mesh. This is especially helpful in simulating self-gravitating fluids with existing gravity solvers used for N-body simulations.
Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications
R. Paul Drake
2005-12-01
We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.
Forced wetting and hydrodynamic assist
NASA Astrophysics Data System (ADS)
Blake, Terence D.; Fernandez-Toledano, Juan-Carlos; Doyen, Guillaume; De Coninck, Joël
2015-11-01
Wetting is a prerequisite for coating a uniform layer of liquid onto a solid. Wetting failure and air entrainment set the ultimate limit to coating speed. It is well known in the coating art that this limit can be postponed by manipulating the coating flow to generate what has been termed "hydrodynamic assist," but the underlying mechanism is unclear. Experiments have shown that the conditions that postpone air entrainment also reduce the apparent dynamic contact angle, suggesting a direct link, but how the flow might affect the contact angle remains to be established. Here, we use molecular dynamics to compare the outcome of steady forced wetting with previous results for the spontaneous spreading of liquid drops and apply the molecular-kinetic theory of dynamic wetting to rationalize our findings and place them on a quantitative footing. The forced wetting simulations reveal significant slip at the solid-liquid interface and details of the flow immediately adjacent to the moving contact line. Our results confirm that the local, microscopic contact angle is dependent not simply only on the velocity of wetting but also on the nature of the flow that drives it. In particular, they support an earlier suggestion that during forced wetting, an intense shear stress in the vicinity of the contact line can assist surface tension forces in promoting dynamic wetting, thus reducing the velocity-dependence of the contact angle. Hydrodynamic assist then appears as a natural consequence of wetting that emerges when the contact line is driven by a strong and highly confined flow. Our theoretical approach also provides a self-consistent model of molecular slip at the solid-liquid interface that enables its magnitude to be estimated from dynamic contact angle measurements. In addition, the model predicts how hydrodynamic assist and slip may be influenced by liquid viscosity and solid-liquid interactions.
Hydrodynamic instability experiments and simulations
Dimonte, G.; Schneider, M.; Frerking, C.E.
1995-07-01
Richtmyer-Meshkov experiments are conducted on the Nova laser with strong radiatively driven shocks (Mach > 20) in planar, two-fluid targets with Atwood number A < 0. Single mode interfacial perturbations are used to test linear theory and 3D random perturbations are used to study turbulent mix. Rayleigh-Taylor experiments are conducted on a new facility called the Linear Electric Motor (LEM) in which macroscopic fluids are accelerated electromagnetically with arbitrary acceleration profiles. The initial experiments are described. Hydrodynamic simulations in 2D are in reasonable agreement with the experiments, but these studies show that simulations in 3D with good radiation transport and equation of state are needed.
Hydrodynamic Synchronisation of Model Microswimmers
NASA Astrophysics Data System (ADS)
Putz, V. B.; Yeomans, J. M.
2009-12-01
We define a model microswimmer with a variable cycle time, thus allowing the possibility of phase locking driven by hydrodynamic interactions between swimmers. We find that, for extensile or contractile swimmers, phase locking does occur, with the relative phase of the two swimmers being, in general, close to 0 or π, depending on their relative position and orientation. We show that, as expected on grounds of symmetry, self T-dual swimmers, which are time-reversal covariant, do not phase-lock. We also discuss the phase behaviour of a line of tethered swimmers, or pumps. These show oscillations in their relative phases reminiscent of the metachronal waves of cilia.
Hydrodynamics of post CHF region
Ishii, M.; De Jarlais, G.
1984-04-01
Among various two-phase flow regimes, the inverted flow in the post-dryout region is relatively less well understood due to its special heat transfer conditions. The review of existing data indicates further research is needed in the areas of basic hydrodynamics related to liquid core disintegration mechanisms, slug and droplet formations, entrainment, and droplet size distributions. In view of this, the inverted flow is studied in detail both analytically and experimentally. Criteria for initial flow regimes in the post-dryout region are given. Preliminary models for subsequent flow regime transition criteria are derived together with correlations for a mean droplet diameter based on the adiabatic simulation data.
Numerical Hydrodynamics in General Relativity.
Font, José A
2000-01-01
The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A representative sample of available numerical schemes is discussed and particular emphasis is paid to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of relevant astrophysical simulations in strong gravitational fields, including gravitational collapse, accretion onto black holes and evolution of neutron stars, is also presented.
Disruptive Innovation in Numerical Hydrodynamics
Waltz, Jacob I.
2012-09-06
We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.
Swimming hydrodynamics: ten questions and the technical approaches needed to resolve them
NASA Astrophysics Data System (ADS)
Lauder, George V.
2011-07-01
Recent experimental and computational studies of swimming hydrodynamics have contributed significantly to our understanding of how animals swim, but much remains to be done. Ten questions are presented here as an avenue to discuss some of the arenas in which progress still is needed and as a means of considering the technical approaches to address these questions. 1. What is the three-dimensional structure of propulsive surfaces? 2. How do propulsive surfaces move in three dimensions? 3. What are the hydrodynamic effects of propulsor deformation during locomotion? 4. How are locomotor kinematics and dynamics altered during unsteady conditions? 5. What is the three-dimensional structure of aquatic animal vortex wakes? 6. To what extent are observed propulsor deformations actively controlled? 7. What is the response of the body and fins of moving animals to external perturbations? 8. How can robotic models help us understand locomotor dynamics of organisms? 9. How do propulsive surfaces interact hydrodynamically during natural motions? 10. What new computational approaches are needed to better understand locomotor hydrodynamics? These ten questions point, not exclusively, toward areas in which progress would greatly enhance our understanding of the hydrodynamics of swimming organisms, and in which the application of new technology will allow continued progress toward understanding the interaction between organisms and the aquatic medium in which they live and move.
Foundation of Hydrodynamics of Strongly Interacting Systems
Wong, Cheuk-Yin
2014-01-01
Hydrodynamics and quantum mechanics have many elements in common, as the density field and velocity fields are common variables that can be constructed in both descriptions. Starting with the Schroedinger equation and the Klein-Gordon for a single particle in hydrodynamical form, we examine the basic assumptions under which a quantum system of particles interacting through their mean fields can be described by hydrodynamics.
Microscale hydrodynamics near moving contact lines
NASA Technical Reports Server (NTRS)
Garoff, Stephen; Chen, Q.; Rame, Enrique; Willson, K. R.
1994-01-01
The hydrodynamics governing the fluid motions on a microscopic scale near moving contact lines are different from those governing motion far from the contact line. We explore these unique hydrodynamics by detailed measurement of the shape of a fluid meniscus very close to a moving contact line. The validity of present models of the hydrodynamics near moving contact lines as well as the dynamic wetting characteristics of a family of polymer liquids are discussed.
Thermal transport in a noncommutative hydrodynamics
Geracie, M. Son, D. T.
2015-03-15
We find the hydrodynamic equations of a system of particles constrained to be in the lowest Landau level. We interpret the hydrodynamic theory as a Hamiltonian system with the Poisson brackets between the hydrodynamic variables determined from the noncommutativity of space. We argue that the most general hydrodynamic theory can be obtained from this Hamiltonian system by allowing the Righi-Leduc coefficient to be an arbitrary function of thermodynamic variables. We compute the Righi-Leduc coefficient at high temperatures and show that it satisfies the requirements of particle-hole symmetry, which we outline.
Hydrodynamic Agents in the Littoral Environment. Phase 1 Progress Report
2007-07-06
the Virginia Coast Reserve, which is near the mouth of the Chesapeake Bay. Mangrove trees are generally found on coastlines between 25...very high salinity and very anoxic conditions. White mangrove trees have an affinity for lower salinity areas. All species need gentle wave/tidal...features (morphology) for the study sites. This effort focuses on the sediment dynamics ring of the morphodynamical corridor. NGA is responsible
Hydromechanical transmission with hydrodynamic drive
Orshansky, Jr., deceased, Elias; Weseloh, William E.
1979-01-01
This transmission has a first planetary gear assembly having first input means connected to an input shaft, first output means, and first reaction means, and a second planetary gear assembly having second input means connected to the first input means, second output means, and second reaction means connected directly to the first reaction means by a reaction shaft. First clutch means, when engaged, connect the first output means to an output shaft in a high driving range. A hydrodynamic drive is used; for example, a torque converter, which may or may not have a stationary case, has a pump connected to the second output means, a stator grounded by an overrunning clutch to the case, and a turbine connected to an output member, and may be used in a starting phase. Alternatively, a fluid coupling or other type of hydrodynamic drive may be used. Second clutch means, when engaged, for connecting the output member to the output shaft in a low driving range. A variable-displacement hydraulic unit is mechanically connected to the input shaft, and a fixed-displacement hydraulic unit is mechanically connected to the reaction shaft. The hydraulic units are hydraulically connected together so that when one operates as a pump the other acts as a motor, and vice versa. Both clutch means are connected to the output shaft through a forward-reverse shift arrangement. It is possible to lock out the torque converter after the starting phase is over.
Inducer Hydrodynamic Load Measurement Devices
NASA Technical Reports Server (NTRS)
Skelley, Stephen E.; Zoladz, Thomas F.
2002-01-01
Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This "rotating balance" was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.
The hydrodynamics of lamprey locomotion
NASA Astrophysics Data System (ADS)
Leftwich, Megan C.
The lamprey, an anguilliform swimmer, propels itself by undulating most of its body. This type of swimming produces flow patterns that are highly three-dimensional in nature and not very well understood. However, substantial previous work has been done to understand two-dimensional unsteady propulsion, the possible wake structures and thrust performance. Limited studies of three-dimensional propulsors with simple geometries have displayed the importance of the third dimension in designing unsteady swimmers. Some of the results of those studies, primarily the ways in which vorticity is organized in the wake region, are seen in lamprey swimming as well. In the current work, the third dimension is not the only important factor, but complex geometry and body undulations also contribute to the hydrodynamics. Through dye flow visualization, particle induced velocimetry and pressure measurements, the hydrodynamics of anguilliform swimming are studied using a custom built robotic lamprey. These studies all indicate that the undulations of the body are not producing thrust. Instead, it is the tail which acts to propel the animal. This conclusion led to further investigation of the tail, specifically the role of varying tail flexibility on hydrodymnamics. It is found that by making the tail more flexible, one decreases the coherence of the vorticity in the lamprey's wake. Additional flexibility also yields less thrust.
Fluctuating Hydrodynamics of Electrolytes Solutions
NASA Astrophysics Data System (ADS)
Peraud, Jean-Philippe; Nonaka, Andy; Chaudhri, Anuj; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.
2016-11-01
In this work, we develop a numerical method for multicomponent solutions featuring electrolytes, in the context of fluctuating hydrodynamics as modeled by the Landau-Lifshitz Navier Stokes equations. Starting from a previously developed numerical scheme for multicomponent low Mach number fluctuating hydrodynamics, we study the effect of the additional forcing terms induced by charged species. We validate our numerical approach with additional theoretical considerations and with examples involving sodium-chloride solutions, with length scales close to Debye length. In particular, we show how charged species modify the structure factors of the fluctuations, both in equilibrium and non-equilibrium (giant fluctuations) systems, and show that the former is consistent with Debye-Huckel theory. We also discuss the consistency of this approach with the electroneutral approximation in regimes where characteristic length scales are significantly larger than the Debye length. Finally, we use this method to explore a type of electrokinetic instability. This work was supported by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research,.
Inducer Hydrodynamic Load Measurement Devices
NASA Technical Reports Server (NTRS)
Skelley, Stephen E.; Zoladz, Thomas F.; Turner, Jim (Technical Monitor)
2002-01-01
Marshall Space Flight Center (MSFC) has demonstrated two measurement devices for sensing and resolving the hydrodynamic loads on fluid machinery. The first - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining both the amplitude and frequency content associated with operating in various cavitation modes. The second device - a high frequency response pressure transducer surface mounted on a rotating component - was merely an extension of existing technology for application in water. MSFC has recently completed experimental evaluations of both the rotating balance and surface-mount transducers in a water test loop. The measurement bandwidth of the rotating balance was severely limited by the relative flexibility of the device itself, resulting in an unexpectedly low structural bending mode and invalidating the higher-frequency response data. Despite these limitations, measurements confirmed that the integrated loads on the four-bladed inducer respond to both cavitation intensity and cavitation phenomena. Likewise, the surface-mount pressure transducers were subjected to a range of temperatures and flow conditions in a non-rotating environment to record bias shifts and transfer functions between the transducers and a reference device. The pressure transducer static performance was within manufacturer's specifications and dynamic response accurately followed that of the reference.
Hydrodynamic dispersion within porous biofilms
NASA Astrophysics Data System (ADS)
Davit, Y.; Byrne, H.; Osborne, J.; Pitt-Francis, J.; Gavaghan, D.; Quintard, M.
2013-01-01
Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher's equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels' network; (2) the solute's diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport.
Hydrodynamic models for slurry bubble column reactors
Dimitri Gidaspow
1996-10-01
The objective of this investigation is to convert learning gas-solid-liquid fluidization model into a predictive design model. The IIT hydrodynamic model computers the phase velocities and the volume fi-actions of gas, liquid and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. As promised in the SIXTH TECHNICAL PROGRESS REPORT, January 1996, this report presents measurements of radial distribution function for 450 micron glass particles in liquid-solid fluidized bed. The report is in the form of a preliminary paper. The authors need the radial distribution function to compute the viscosity and the equation of state for particles. The principal results are as follows: (1) The measured radial distribution function, g{sub 0}, is a monotonic function of the solid volume fraction. The values of the radial distribution function g{sub 0} are in the range of the predictions from Bagnold equation and Carnahan and Starling equation. (2) The position of the first peak of the radial distribution function does not lie at r = d at contact (d is particle diameter). This differs from the predications from the hard sphere model and the measurements in the gas-solid system (Gidaspow and Huilin, 1996). This is due to a liquid film lubrication effect in the liquid-solid system.
Black Widow Pulsar radiation hydrodynamics simulation using Castro: Methodology
NASA Astrophysics Data System (ADS)
Barrios Sazo, Maria; Zingale, Michael; Zhang, Weiqun
2017-01-01
A black widow pulsar (BWP) is a millisecond pulsar in a tight binary system with a low mass star. The fast rotating pulsar emits intense radiation, which injects energy and ablates the companion star. Observation of the ablation is seen as pulsar eclipses caused by a larger object than the companion star Roche lobe. This phenomenon is attributed to a cloud surrounding the evaporating star. We will present the methodology for modeling the interaction between the radiation coming from the pulsar and the companion star using the radiation hydrodynamics code Castro. Castro is an adaptive mesh refinement (AMR) code that solves the compressible hydrodynamic equations for astrophysical flows with simultaneous refinement in space and time. The code also includes self-gravity, nuclear reactions and radiation. We are employing the gray-radiation solver, which uses a mixed-frame formulation of radiation hydrodynamics under the flux-limited diffusion approximation. In our setup, we are modeling the companion star with the radiation field as a boundary condition, coming from one side of the domain. In addition to a model setup in 2-d axisymmetry, we also have a 3-d setup, which is more physical given the nature of the system considering the companion is facing the pulsar on one side. We discuss the progress of our calculations, first results, and future work.The work at Stony Brook was supported by DOE/Office of Nuclear Physics grant DE-FG02-87ER40317
Hydrodynamics, Fungal Physiology, and Morphology.
Serrano-Carreón, L; Galindo, E; Rocha-Valadéz, J A; Holguín-Salas, A; Corkidi, G
2015-01-01
Filamentous cultures, such as fungi and actinomycetes, contribute substantially to the pharmaceutical industry and to enzyme production, with an annual market of about 6 billion dollars. In mechanically stirred reactors, most frequently used in fermentation industry, microbial growth and metabolite productivity depend on complex interactions between hydrodynamics, oxygen transfer, and mycelial morphology. The dissipation of energy through mechanically stirring devices, either flasks or tanks, impacts both microbial growth through shearing forces on the cells and the transfer of mass and energy, improving the contact between phases (i.e., air bubbles and microorganisms) but also causing damage to the cells at high energy dissipation rates. Mechanical-induced signaling in the cells triggers the molecular responses to shear stress; however, the complete mechanism is not known. Volumetric power input and, more importantly, the energy dissipation/circulation function are the main parameters determining mycelial size, a phenomenon that can be explained by the interaction of mycelial aggregates and Kolmogorov eddies. The use of microparticles in fungal cultures is also a strategy to increase process productivity and reproducibility by controlling fungal morphology. In order to rigorously study the effects of hydrodynamics on the physiology of fungal microorganisms, it is necessary to rule out the possible associated effects of dissolved oxygen, something which has been reported scarcely. At the other hand, the processes of phase dispersion (including the suspended solid that is the filamentous biomass) are crucial in order to get an integral knowledge about biological and physicochemical interactions within the bioreactor. Digital image analysis is a powerful tool for getting relevant information in order to establish the mechanisms of mass transfer as well as to evaluate the viability of the mycelia. This review focuses on (a) the main characteristics of the two most
Hydrodynamic models of a Cepheid atmosphere
NASA Technical Reports Server (NTRS)
Karp, A. H.
1975-01-01
Instead of computing a large number of coarsely zoned hydrodynamic models covering the entire atmospheric instability strip, the author computed a single model as well as computer limitations allow. The implicit hydrodynamic code of Kutter and Sparks was modified to include radiative transfer effects in optically thin zones.
Relativistic Hydrodynamics for Heavy-Ion Collisions
ERIC Educational Resources Information Center
Ollitrault, Jean-Yves
2008-01-01
Relativistic hydrodynamics is essential to our current understanding of nucleus-nucleus collisions at ultrarelativistic energies (current experiments at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN Large Hadron Collider). This is an introduction to relativistic hydrodynamics for graduate students. It includes a detailed…
Hydrodynamic description for ballistic annihilation systems
Garcia de Soria, Maria Isabel; Trizac, Emmanuel; Maynar, Pablo; Schehr, Gregory; Barrat, Alain
2009-01-21
The problem of the validity of a hydrodynamic description for a system in which there are no collisional invariants is addressed. Hydrodynamic equations have been derived and successfully tested against simulation data for a system where particles annihilate with a probability p, or collide elastically otherwise. The response of the system to a linear perturbation is analyzed as well.
Non-boost-invariant dissipative hydrodynamics
NASA Astrophysics Data System (ADS)
Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael; Tinti, Leonardo
2016-12-01
The one-dimensional non-boost-invariant evolution of the quark-gluon plasma, presumably produced during the early stages of heavy-ion collisions, is analyzed within the frameworks of viscous and anisotropic hydrodynamics. We neglect transverse dynamics and assume homogeneous conditions in the transverse plane but, differently from Bjorken expansion, we relax longitudinal boost invariance in order to study the rapidity dependence of various hydrodynamical observables. We compare the results obtained using several formulations of second-order viscous hydrodynamics with a recent approach to anisotropic hydrodynamics, which treats the large initial pressure anisotropy in a nonperturbative fashion. The results obtained with second-order viscous hydrodynamics depend on the particular choice of the second-order terms included, which suggests that the latter should be included in the most complete way. The results of anisotropic hydrodynamics and viscous hydrodynamics agree for the central hot part of the system, however, they differ at the edges where the approach of anisotropic hydrodynamics helps to control the undesirable growth of viscous corrections observed in standard frameworks.
The hydrodynamic theory of detonation
NASA Technical Reports Server (NTRS)
Langweiler, Heinz
1939-01-01
This report derives equations containing only directly measurable constants for the quantities involved in the hydrodynamic theory of detonation. The stable detonation speed, D, is revealed as having the lowest possible value in the case of positive material velocity, by finding the minimum of the Du curve (u denotes the speed of the gases of combustion). A study of the conditions of energy and impulse in freely suspended detonating systems leads to the disclosure of a rarefaction front traveling at a lower speed behind the detonation front; its velocity is computed. The latent energy of the explosive passes into the steadily growing detonation zone - the region between the detonation front and the rarefaction front. The conclusions lead to a new definition of the concept of shattering power. The calculations are based on the behavior of trinitrotoluene.
Nonstandard Gaits in Unsteady Hydrodynamics
NASA Astrophysics Data System (ADS)
Fairchild, Michael; Rowley, Clarence
2016-11-01
Marine biology has long inspired the design and engineering of underwater vehicles. The literature examining the kinematics and dynamics of fishes, ranging from undulatory anguilliform swimmers to oscillatory ostraciiform ones, is vast. Past numerical studies of these organisms have principally focused on gaits characterized by sinusoidal pitching and heaving motions. It is conceivable that more sophisticated gaits could perform better in some respects, for example as measured by thrust generation or by cost of transport. This work uses an unsteady boundary-element method to numerically investigate the hydrodynamics and propulsive efficiency of high-Reynolds-number swimmers whose gaits are encoded by Fourier series or by Jacobi elliptic functions. Numerical results are presented with an emphasis on identifying particular wake structures and modes of motion that are associated with optimal swimming. This work was supported by the Office of Naval Research through MURI Grant N00014-14-1-0533.
Hydrodynamics and phases of flocks
Toner, John; Tu Yuhai . E-mail: yuhai@us.ibm.com; Ramaswamy, Sriram
2005-07-01
We review the past decade's theoretical and experimental studies of flocking: the collective, coherent motion of large numbers of self-propelled 'particles' (usually, but not always, living organisms). Like equilibrium condensed matter systems, flocks exhibit distinct 'phases' which can be classified by their symmetries. Indeed, the phases that have been theoretically studied to date each have exactly the same symmetry as some equilibrium phase (e.g., ferromagnets, liquid crystals). This analogy with equilibrium phases of matter continues in that all flocks in the same phase, regardless of their constituents, have the same 'hydrodynamic'-that is, long-length scale and long-time behavior, just as, e.g., all equilibrium fluids are described by the Navier-Stokes equations. Flocks are nonetheless very different from equilibrium systems, due to the intrinsically nonequilibrium self-propulsion of the constituent 'organisms'. This difference between flocks and equilibrium systems is most dramatically manifested in the ability of the simplest phase of a flock, in which all the organisms are, on average moving in the same direction (we call this a 'ferromagnetic' flock; we also use the terms 'vector-ordered' and 'polar-ordered' for this situation) to exist even in two dimensions (i.e., creatures moving on a plane), in defiance of the well-known Mermin-Wagner theorem of equilibrium statistical mechanics, which states that a continuous symmetry (in this case, rotation invariance, or the ability of the flock to fly in any direction) can not be spontaneously broken in a two-dimensional system with only short-ranged interactions. The 'nematic' phase of flocks, in which all the creatures move preferentially, or are simply oriented preferentially, along the same axis, but with equal probability of moving in either direction, also differs dramatically from its equilibrium counterpart (in this case, nematic liquid crystals). Specifically, it shows enormous number fluctuations, which
Stellar Explosions: Hydrodynamics and Nucleosynthesis
NASA Astrophysics Data System (ADS)
Jose, Jordi
2016-01-01
Stars are the main factories of element production in the universe through a suite of complex and intertwined physical processes. Such stellar alchemy is driven by multiple nuclear interactions that through eons have transformed the pristine, metal-poor ashes leftover by the Big Bang into a cosmos with 100 distinct chemical species. The products of stellar nucleosynthesis frequently get mixed inside stars by convective transport or through hydrodynamic instabilities, and a fraction of them is eventually ejected into the interstellar medium, thus polluting the cosmos with gas and dust. The study of the physics of the stars and their role as nucleosynthesis factories owes much to cross-fertilization of different, somehow disconnected fields, ranging from observational astronomy, computational astrophysics, and cosmochemistry to experimental and theoretical nuclear physics. Few books have simultaneously addressed the multidisciplinary nature of this field in an engaging way suitable for students and young scientists. Providing the required multidisciplinary background in a coherent way has been the driving force for Stellar Explosions: Hydrodynamics and Nucleosynthesis. Written by a specialist in stellar astrophysics, this book presents a rigorous but accessible treatment of the physics of stellar explosions from a multidisciplinary perspective at the crossroads of computational astrophysics, observational astronomy, cosmochemistry, and nuclear physics. Basic concepts from all these different fields are applied to the study of classical and recurrent novae, type I and II supernovae, X-ray bursts and superbursts, and stellar mergers. The book shows how a multidisciplinary approach has been instrumental in our understanding of nucleosynthesis in stars, particularly during explosive events.
Stellar Explosions: Hydrodynamics and Nucleosynthesis
NASA Astrophysics Data System (ADS)
José, Jordi
2015-12-01
Stars are the main factories of element production in the universe through a suite of complex and intertwined physical processes. Such stellar alchemy is driven by multiple nuclear interactions that through eons have transformed the pristine, metal-poor ashes leftover by the Big Bang into a cosmos with 100 distinct chemical species. The products of stellar nucleosynthesis frequently get mixed inside stars by convective transport or through hydrodynamic instabilities, and a fraction of them is eventually ejected into the interstellar medium, thus polluting the cosmos with gas and dust. The study of the physics of the stars and their role as nucleosynthesis factories owes much to cross-fertilization of different, somehow disconnected fields, ranging from observational astronomy, computational astrophysics, and cosmochemistry to experimental and theoretical nuclear physics. Few books have simultaneously addressed the multidisciplinary nature of this field in an engaging way suitable for students and young scientists. Providing the required multidisciplinary background in a coherent way has been the driving force for Stellar Explosions: Hydrodynamics and Nucleosynthesis. Written by a specialist in stellar astrophysics, this book presents a rigorous but accessible treatment of the physics of stellar explosions from a multidisciplinary perspective at the crossroads of computational astrophysics, observational astronomy, cosmochemistry, and nuclear physics. Basic concepts from all these different fields are applied to the study of classical and recurrent novae, type I and II supernovae, X-ray bursts and superbursts, and stellar mergers. The book shows how a multidisciplinary approach has been instrumental in our understanding of nucleosynthesis in stars, particularly during explosive events.
The hydrodynamics of dolphin drafting
Weihs, Daniel
2004-01-01
Background Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Results Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in front to move forwards and radially outwards, and water behind the body to move forwards to replace the animal's mass. Thus, the calf can gain a 'free ride' in the forward-moving areas. Utilizing these effects, the neonate can gain up to 90% of the thrust needed to move alongside the mother at speeds of up to 2.4 m/sec. A comparison with observations of eastern spinner dolphins (Stenella longirostris) is presented, showing savings of up to 60% in the thrust that calves require if they are to keep up with their mothers. Conclusions A theoretical analysis, backed by observations of free-swimming dolphin schools, indicates that hydrodynamic interactions with mothers play an important role in enabling dolphin calves to keep up with rapidly moving adult school members. PMID:15132740
Hydrodynamic Instabilities in High-Energy-Density Settings
NASA Astrophysics Data System (ADS)
Smalyuk, Vladimir
2016-10-01
Our understanding of hydrodynamic instabilities, such as the Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities, in high-energy-density (HED) settings over past two decades has progressed enormously. The range of conditions where hydrodynamic instabilities are experimentally observed now includes direct and indirect drive inertial confinement fusion (ICF) where surprises continue to emerge, linear and nonlinear regimes, classical interfaces vs. stabilized ablation fronts, tenuous ideal plasmas vs. high density Fermi degenerate plasmas, bulk fluid interpenetration vs. mixing down to the atomic level, in the presence of magnetic fields and/or intense radiation, and in solid state plastic flow at high pressures and strain rates. Regimes in ICF can involve extreme conditions of matter with temperatures up to kilovolts, densities of a thousand times solid densities, and time scales of nanoseconds. On the other hand, scaled conditions can be generated that map to exploding stars (supernovae) with length and time scales of millions of kilometers and hours to days or even years of instability evolution, planetary formation dynamics involving solid-state plastic flow which severely modifies the RT growth and continues to challenge reliable theoretical descriptions. This review will look broadly at progress in probing and understanding hydrodynamic instabilities in these very diverse HED settings, and then will examine a few cases in more depth to illustrate the detailed science involved. Experimental results on large-scale HED facilities such as the Omega, Nike, Gekko, and Shenguang lasers will be reviewed and the latest developments at the National Ignition Facility (NIF) and Z machine will be covered. Finally, current overarching questions and challenges will be summarized to motivate research directions for future. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.
Mass flux in extended and classical hydrodynamics.
Grmela, Miroslav
2014-06-01
In classical hydrodynamics, the mass flux is universally chosen to be the momentum field. In extended hydrodynamics, the mass flux acquires different terms. The extended hydrodynamics introduced and investigated in this paper uses a one-particle distribution function as the extra state variable chosen to characterize the microstructure. We prove that the extended hydrodynamics is fully autonomous in the sense that it is compatible with thermodynamics (i.e., the entropy does not decrease during the time evolution) and with mechanics (i.e., the part of the time evolution that leaves the entropy unchanged is Hamiltonian). Subsequently, we investigate its possible reductions. In some situations the emerging reduced dynamical theory is the classical hydrodynamics that is fully autonomous (i.e., all the structure that makes the extended theory fully autonomous is kept in the reduced theory). In other situations (for example, when the fluids under investigation have large density gradients) the reduced theories are not fully autonomous. In such a case the reduced theories constitute a family of mutually related dynamical theories (each of them involving a different amount of detail) that we consider to be a mathematical formulation of multiscale (or multilevel) hydrodynamics. It is in the reduced theories belonging to the multiscale hydrodynamics where the terms that emerge in the mass flux take the form of self-diffusion.
Simulating hydrodynamics on tidal mudflats
NASA Astrophysics Data System (ADS)
Cook, S.; Lippmann, T. C.
2014-12-01
Biogeochemical cycling in estuaries is governed by fluxes from both riverine sources and through estuarine sediment deposits. Although estimates from river sources are relatively common and easily sampled, estimates of nutrient fluxes through the fluid-sediment interface are less common and limited to deeper portions of the bays away from intertidal areas. Lack of quantifiable shear stress estimates over intertidal areas limits our overall understanding of nutrient budgets in estuaries. Unfortunately, observation of intertidal hydrodynamics and nutrient fluxes over tidal flats and near the water's edge is difficult owing to the temporally varying and spatially extensive region where the tides inundate, and thus numerical modeling is often employed. In this work, the Regional Ocean Modeling System (ROMS), a three dimensional numerical hydrodynamic model was used to investigate the shear stresses over intertidal mudflats in the Great Bay, a tidally-dominated New England estuary cut by several tidal channels and with over 50% of the estuary exposed at low tide. The ROMS wetting and drying scheme was used to simulate the rising and falling tide on the flats, a successful approach adapted in other regions of the world but not always inclusive of tidal channels. Bathymetric data obtained in 2009 and 2013 was used to define the model grid. Predicted tides are forced at Adam's Pt., a natural constriction in the estuary about 20 km upstream of the mouth and at the entrance to the Great Bay. Of particular interest are fluxes of material on-to and off-of the tidal flats which contribute to water quality conditions in the estuary, and are largely governed by shear stresses that drive nutrient fluxes at the fluid-sediment interface. Basin wide estimates of near-bottom shear stresses can be used to estimate first order nutrient fluxes over a tidal cycle and hence describe general biogeochemical dynamics of the estuary. Future work will include enhanced forcing of currents by
A Displayer of Stellar Hydrodynamics Processes
NASA Astrophysics Data System (ADS)
Vigo, José Antonio Escartín; Senz, Domingo García
The graphics display tool that we present here was originally developed to meet the needs of the Astronomy and Astrophysics group at the UPC (GAA). At present, it is used to display the plots obtained from hydrodynamic simulations using the SPH (smoothed particle hydrodynamics) method. It is, however, a generic program that can be used for other multidimensional hydrodynamic methods. The application combines the most widely used features of other programs (most of them commercial) such as GnuPlot, Surfer, Grapher, IDL, Voxler, etc.
Non abelian hydrodynamics and heavy ion collisions
Calzetta, E.
2014-01-14
The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.
Flanagan, Michael F.
2015-01-01
The craniocervical junction (CCJ) is a potential choke point for craniospinal hydrodynamics and may play a causative or contributory role in the pathogenesis and progression of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, MS, and ALS, as well as many other neurological conditions including hydrocephalus, idiopathic intracranial hypertension, migraines, seizures, silent-strokes, affective disorders, schizophrenia, and psychosis. The purpose of this paper is to provide an overview of the critical role of the CCJ in craniospinal hydrodynamics and to stimulate further research that may lead to new approaches for the prevention and treatment of the above neurodegenerative and neurological conditions. PMID:26770824
NASA Astrophysics Data System (ADS)
Clark, D. S.; Robey, H. F.; Smalyuk, V. A.
2015-05-01
Encouraging progress is being made in demonstrating control of ablation front hydrodynamic instability growth in inertial confinement fusion implosion experiments on the National Ignition Facility [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, and R. Al-Ayat, Phys. Plasmas 16, 041006 (2009)]. Even once ablation front stabilities are controlled, however, instability during the stagnation phase of the implosion can still quench ignition. A scheme is proposed to reduce the growth of stagnation phase instabilities through the reverse of the "adiabat shaping" mechanism proposed to control ablation front growth. Two-dimensional radiation hydrodynamics simulations confirm that improved stagnation phase stability should be possible without compromising fuel compression.
Detonation waves in relativistic hydrodynamics
Cissoko, M. )
1992-02-15
This paper is concerned with an algebraic study of the equations of detonation waves in relativistic hydrodynamics taking into account the pressure and the energy of thermal radiation. A new approach to shock and detonation wavefronts is outlined. The fluid under consideration is assumed to be perfect (nonviscous and nonconducting) and to obey the following equation of state: {ital p}=({gamma}{minus}1){rho} where {ital p}, {rho}, and {gamma} are the pressure, the total energy density, and the adiabatic index, respectively. The solutions of the equations of detonation waves are reduced to the problem of finding physically acceptable roots of a quadratic polynomial {Pi}({ital X}) where {ital X} is the ratio {tau}/{tau}{sub 0} of dynamical volumes behind and ahead of the detonation wave. The existence and the locations of zeros of this polynomial allow it to be shown that if the equation of state of the burnt fluid is known then the variables characterizing the unburnt fluid obey well-defined physical relations.
Hydrodynamic aspects of fish olfaction
Cox, Jonathan P.L
2008-01-01
Flow into and around the olfactory chamber of a fish determines how odorant from the fish's immediate environment is transported to the sensory surface (olfactory epithelium) lining the chamber. Diffusion times in water are long, even over comparatively short distances (millimetres). Therefore, transport from the external environment to the olfactory epithelium must be controlled by processes that rely on convection (i.e. the bulk flow of fluid). These include the beating of cilia lining the olfactory chamber and the relatively inexpensive pumping action of accessory sacs. Flow through the chamber may also be induced by an external flow. Flow over the olfactory epithelium appears to be laminar. Odorant transfer to the olfactory epithelium may be facilitated in several ways: if the olfactory organs are mounted on stalks that penetrate the boundary layer; by the steep velocity gradients generated by beating cilia; by devices that deflect flow into the olfactory chamber; by parallel arrays of olfactory lamellae; by mechanical agitation of the chamber (or olfactory stalks); and by vortices. Overall, however, our knowledge of the hydrodynamics of fish olfaction is far from complete. Several areas of future research are outlined. PMID:18184629
Hydrodynamic Instabilities Produced by Evaporation
NASA Astrophysics Data System (ADS)
Romo-Cruz, Julio Cesar Ruben; Hernandez-Zapata, Sergio; Ruiz-Chavarria, Gerardo
2012-11-01
When a liquid layer (alcohol in the present work) is in an environment where its relative humidity is less than 100 percent evaporation appears. When RH is above a certain threshold the liquid is at rest. If RH decreases below this threshold the flow becomes unstable, and hydrodynamic cells develop. The aim of this work is to understand the formation of those cells and its main features. Firstly, we investigate how the cell size depends on the layer width. We also study how temperature depends on the vertical coordinate when the cells are present. An inverse temperature gradient is found, that is, the bottom of liquid layer is colder than the free surface. This shows that the intuitive idea that the cells are due to a direct temperature gradient, following a Marangoni-like process, does not work. We propose the hypothesis that the evaporation produce a pressure gradient that is responsible of the cell development. On the other hand, using a Schlieren technique we study the topography of the free surface when cells are present. Finally the alcohol vapor layer adjacent to the liquid surface is explored using scattering experiments, giving some insight on the plausibility of the hypothesis described previously. Authors acknowledge support by DGAPA-UNAM under project IN116312 ``Vorticidad y ondas no lineales en fluidos.''
Hydrodynamically enforced entropic Brownian pump
NASA Astrophysics Data System (ADS)
Ai, Bao-quan; He, Ya-feng; Li, Feng-guo; Zhong, Wei-rong
2013-04-01
Transport of overdamped Brownian particles in a finite hydrodynamical channel is investigated in the presence of the ac driving force and the pressure-driven flow. The system is bounded by two particle reservoirs. With the help of the Fick-Jacobs method, we obtain the directed current of Brownian particles and the pumping capacity of the system. The directed transport is determined by the competitions among the asymmetry of the channel, the ac driving force, the pressure-driven flow, and the concentration difference. Their interplays can exhibit the peculiar properties. Remarkably, the particles can be pumped through the channel from the lower concentration reservoir to the higher concentration one, or from the lower pressure side to the higher pressure one. In addition, due to the existence of the pressure drop, ac driving force still plays the significant role on directed transport even in a completely symmetric channel. Our results could be implemented in constrained structures with narrow channels or pores where the particles are suspended in a solvent.
The hydrodynamics of swimming microorganisms
NASA Astrophysics Data System (ADS)
Lauga, Eric; Powers, Thomas R.
2009-09-01
Cell motility in viscous fluids is ubiquitous and affects many biological processes, including reproduction, infection and the marine life ecosystem. Here we review the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming, tens of micrometers and below. At this scale, inertia is unimportant and the Reynolds number is small. Our emphasis is on the simple physical picture and fundamental flow physics phenomena in this regime. We first give a brief overview of the mechanisms for swimming motility, and of the basic properties of flows at low Reynolds number, paying special attention to aspects most relevant for swimming such as resistance matrices for solid bodies, flow singularities and kinematic requirements for net translation. Then we review classical theoretical work on cell motility, in particular early calculations of swimming kinematics with prescribed stroke and the application of resistive force theory and slender-body theory to flagellar locomotion. After examining the physical means by which flagella are actuated, we outline areas of active research, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers and the optimization of locomotion strategies.
Fluctuating hydrodynamics for ionic liquids
NASA Astrophysics Data System (ADS)
Lazaridis, Konstantinos; Wickham, Logan; Voulgarakis, Nikolaos
2017-04-01
We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau-Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids.
Low Reynolds number hydrodynamics and mesoscale simulations
NASA Astrophysics Data System (ADS)
Winkler, Roland G.
2016-11-01
Hydrodynamics and hydrodynamic interactions are fundamental for the motility of microswimmers. This includes the propulsion mechanism itself, the synchronized motion of flagella in flagellar bundles and beating cilia of cilia arrays, and even extends to collective behaviors. The general importance of hydrodynamics has stimulated the development of mesoscale simulation approaches to efficiently study dynamical properties of objects embedded in a fluid. In this minireview, the properties of flows at low Reynolds numbers are discussed, thereby the unsteady acceleration term is typically taken into account (Landau-Lifshitz Navier-Stokes equations). Specifically, the synchronization of microrotors by time-dependent hydrodynamic interactions is discussed and the propulsion of a rotating helix. Moreover, the multiparticle collisions dynamics method (MPC), a mesoscale simulation approach for fluids, is outlined. Simulation results for the flow field of a model E. Coli bacterium and its swimming behavior next to a surface are presented.
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Quasiparticle anisotropic hydrodynamics for central collisions
NASA Astrophysics Data System (ADS)
Alqahtani, Mubarak; Nopoush, Mohammad; Strickland, Michael
2017-03-01
We use quasiparticle anisotropic hydrodynamics to study an azimuthally symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state (EoS). We compare results obtained by using the quasiparticle method with the standard method of imposing the EoS in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio η /s . We find that the three methods agree well for small shear viscosity to entropy density ratio η /s , but differ at large η /s , with the standard anisotropic EoS method showing suppressed production at low transverse-momentum compared with the other two methods considered. Finally, we demonstrate explicitly that, when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative at large pT. Such behavior is not seen in either anisotropic hydrodynamics approach, irrespective of the value of η /s .
Experimental hydrodynamics of fish locomotion: functional insights from wake visualization.
Drucker, Eliot G; Lauder, George V
2002-04-01
Despite enormous progress during the last twenty years in understanding the mechanistic basis of aquatic animal propulsion-a task involving the construction of a substantial data base on patterns of fin and body kinematics and locomotor muscle function-there remains a key area in which biologists have little information: the relationship between propulsor activity and water movement in the wake. How is internal muscular force translated into external force exerted on the water? What is the pattern of fluid force production by different fish fins (e.g., pectoral, caudal, dorsal) and how does swimming force vary with speed and among species? These types of questions have received considerable attention in analyses of terrestrial locomotion where force output by limbs can be measured directly with force plates. But how can forces exerted by animals moving through fluid be measured? The advent of digital particle image velocimetry (DPIV) has provided an experimental hydrodynamic approach for quantifying the locomotor forces of freely moving animals in fluids, and has resulted in significant new insights into the mechanisms of fish propulsion. In this paper we present ten "lessons learned" from the application of DPIV to problems of fish locomotion over the last five years. (1) Three-dimensional DPIV analysis is critical for reconstructing wake geometry. (2) DPIV analysis reveals the orientation of locomotor reaction forces. (3) DPIV analysis allows calculation of the magnitude of locomotor forces. (4) Swimming speed can have a major impact on wake structure. (5) DPIV can reveal interspecific differences in vortex wake morphology. (6) DPIV analysis can provide new insights into the limits to locomotor performance. (7) DPIV demonstrates the functional versatility of fish fins. (8) DPIV reveals hydrodynamic force partitioning among fins. (9) DPIV shows that wake interaction among fins may enhance thrust production. (10) Experimental hydrodynamic analysis can provide
Scaling supernova hydrodynamics to the laboratory
Kane, J O; Remington, B A; Arnett, D; Fryxell, B A; Drake, R P
1998-11-10
Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, they are attempting to rigorously scale the physics of the laboratory in supernova. The scaling of hydrodynamics on microscopic laser scales to hydrodynamics on the SN-size scales is presented and requirements established. Initial results were reported in [1]. Next the appropriate conditions are generated on the NOVA laser. 10-15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth, due to the Richtmyer-Meshkov instability and to the Rayleigh-Taylor instability as the interface decelerates is generated. This scales the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few x10{sup 3} s. The experiment is modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike bubble velocities using potential flow theory and Ott thin shell theory is presented, as well as a study of 2D vs. 3D difference in growth at the He-H interface of Sn 1987A.
On the definition of discrete hydrodynamic variables.
Español, Pep; Zúñiga, Ignacio
2009-10-28
The Green-Kubo formula for discrete hydrodynamic variables involves information about not only the fluid transport coefficients but also about discrete versions of the differential operators that govern the evolution of the discrete variables. This gives an intimate connection between discretization procedures in fluid dynamics and coarse-graining procedures used to obtain hydrodynamic behavior of molecular fluids. We observed that a natural definition of discrete hydrodynamic variables in terms of Voronoi cells leads to a Green-Kubo formula which is divergent, rendering the full coarse-graining strategy useless. In order to understand this subtle issue, in the present paper we consider the coarse graining of noninteracting Brownian particles. The discrete hydrodynamic variable for this problem is the number of particles within Voronoi cells. Thanks to the simplicity of the model we spot the origin of the singular behavior of the correlation functions. We offer an alternative definition, based on the concept of a Delaunay cell that behaves properly, suggesting the use of the Delaunay construction for the coarse graining of molecular fluids at the discrete hydrodynamic level.
Anisotropic hydrodynamics for conformal Gubser flow
NASA Astrophysics Data System (ADS)
Strickland, Michael; Nopoush, Mohammad; Ryblewski, Radoslaw
2016-12-01
In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.
New formulation of leading order anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Tinti, Leonardo
2015-05-01
Anisotropic hydrodynamics is a reorganization of the relativistic hydrodynamics expansion, with the leading order already containing substantial momentum-space anisotropies. The latter are a cause of concern in the traditional viscous hydrodynamics, since large momentum anisotropies generated in ultrarelativistic heavy-ion collisions are not consistent with the hypothesis of small deviations from an isotropic background, i.e., from the local equilibrium distribution. We discuss the leading order of the expansion, presenting a new formulation for the (1+1)- dimensional case, namely, for the longitudinally boost invariant and cylindrically symmetric flow. This new approach is consistent with the well established framework of Israel and Stewart in the close to equilibrium limit (where we expect viscous hydrodynamics to work well). If we consider the (0+1)-dimensional case, that is, transversally homogeneous and longitudinally boost invariant flow, the new form of anisotropic hydrodynamics leads to better agreement with known solutions of the Boltzmann equation than the previous formulations, especially when we consider massive particles.
Hydrodynamic approaches in relativistic heavy ion reactions
NASA Astrophysics Data System (ADS)
Derradi de Souza, R.; Koide, T.; Kodama, T.
2016-01-01
We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation to the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to be answered to clarify the physics of collective phenomena in the relativistic heavy ion collisions are pointed out.
Development of hydrodynamic micro-bearings
NASA Astrophysics Data System (ADS)
Wang, P.; Zhang, J.; Spikes, H. A.; Reddyhoff, T.; Holmes, A. S.
2016-11-01
This paper describes the modelling and testing of mm-scale hydrodynamic bearings which are being developed to improve the efficiency of a cm-scale turbine energy harvester, whose efficiency was previously limited by poorly lubricated commercial jewel-bearings. The bearings were fabricated using DRIE and their performance was assessed using a custom built MEMS tribometer. Results demonstrate that acceptably low friction is achieved when low viscosity liquid lubricants are used in combination with an appropriate choice of friction modifier additive. Further reduction in friction is demonstrated when the step height of bearing is adjusted in accordance with hydrodynamic theory. In parallel with the experiments, hydrodynamic lubricant modelling has been carried out to predict and further optimize film thickness and friction performance. Modelling results are presented and validated against experimental friction data.
Nondecaying hydrodynamic interactions along narrow channels
NASA Astrophysics Data System (ADS)
Misiunas, Karolis; Pagliara, Stefano; Lauga, Eric; Lister, John R.; Keyser, Ulrich
Particle-particle interactions are of paramount importance in every multi-body system as they determine the collective behaviour and coupling strength. Many well-known interactions like electro-static, van der Waals or screened Coulomb, decay exponentially or with negative powers of the particle spacing r. Similarly, hydrodynamic interactions between particles undergoing Brownian motion decay as 1 / r in bulk, and are assumed to decay in small channels. Such interactions are ubiquitous in biological and technological systems. Here we confine two particles undergoing Brownian motion in narrow, microfluidic channels and study their coupling through hydrodynamic interactions. Our experiments show that the hydrodynamic particle-particle interactions are distance-independent in these channels. This finding is of fundamental importance for the interpretation of experiments where dense mixtures of particles or molecules diffuse through finite length, water-filled channels or pore networks.
Relativistic hydrodynamics from the projection operator method.
Minami, Yuki; Hidaka, Yoshimasa
2013-02-01
We study relativistic hydrodynamics in the linear regime, based on Mori's projection operator method. In relativistic hydrodynamics, it is considered that an ambiguity about the fluid velocity occurs from the choice of a local rest frame: the Landau and Eckart frames. We find that the difference of the frames is not the choice of the local rest frame, but rather that of dynamic variables in the linear regime. We derive hydrodynamic equations in both frames by the projection operator method. We show that the natural derivation gives the linearized Landau equation. Also we find that, even for the Eckart frame, the slow dynamics is actually described by the dynamic variables for the Landau frame.
On the hydrodynamics of swimming enzymes.
Bai, Xiaoyu; Wolynes, Peter G
2015-10-28
Several recent experiments suggest that rather generally the diffusion of enzymes may be augmented through their activity. We demonstrate that such swimming motility can emerge from the interplay between the enzyme energy landscape and the hydrodynamic coupling of the enzyme to its environment. Swimming thus occurs during the transit time of a transient allosteric change. We estimate the velocity during the transition. The analysis of such a swimming motion suggests the final stroke size is limited by the hydrodynamic size of the enzyme. This limit is quite a bit smaller than the values that can be inferred from the recent experiments. We also show that one proposed explanation of the experiments based on reaction heat effects can be ruled out using an extended hydrodynamic analysis. These results lead us to propose an alternate explanation of the fluorescence correlation measurements.
Hydrodynamical comparison test of solar models
NASA Astrophysics Data System (ADS)
Bach, K.; Kim, Y.-C.
2012-12-01
We present three dimensional radiation-hydrodynamical (RHD) simulations for solar surface convection based on three most recent solar mixtures: Grevesse & Sauval (1998), Asplund, Grevesse & Sauval (2005), and Asplund, Grevesse, Sauval & Scott (2009). The outer convection zone of the Sun is an extremely turbulent region composed of partly ionized compressible gases at high temperature. The super-adiabatic layer (SAL) is the transition region where the transport of energy changes drastically from convection to radiation. In order to describe physical processes accurately, a realistic treatment of radiation should be considered as well as convection. However, newly updated solar mixtures that are established from radiation-hydrodynamics do not generate properly internal structures estimated by helioseismology. In order to address this fundamental problem, solar models are constructed consistently based on each mixture and used as initial configurations for radiation-hydrodynamical simulations. From our simulations, we find that the turbulent flows in each model are statistically similar in the SAL.
Dynamo efficiency controlled by hydrodynamic bistability
NASA Astrophysics Data System (ADS)
Miralles, Sophie; Hérault, Johann; Fauve, Stephan; Gissinger, Christophe; Pétrélis, François; Daviaud, François; Dubrulle, Bérengère; Boisson, Jean; Bourgoin, Mickaël; Verhille, Gautier; Odier, Philippe; Pinton, Jean-François; Plihon, Nicolas
2014-06-01
Hydrodynamic and magnetic behaviors in a modified experimental setup of the von Kármán sodium flow—where one disk has been replaced by a propeller—are investigated. When the rotation frequencies of the disk and the propeller are different, we show that the fully turbulent hydrodynamic flow undergoes a global bifurcation between two configurations. The bistability of these flow configurations is associated with the dynamics of the central shear layer. The bistable flows are shown to have different dynamo efficiencies; thus for a given rotation rate of the soft-iron disk, two distinct magnetic behaviors are observed depending on the flow configuration. The hydrodynamic transition controls the magnetic field behavior, and bifurcations between high and low magnetic field branches are investigated.
Hydrodynamic stellar interactions in dense star clusters
NASA Technical Reports Server (NTRS)
Rasio, Frederic A.
1993-01-01
Highly detailed HST observations of globular-cluster cores and galactic nuclei motivate new theoretical studies of the violent dynamical processes which govern the evolution of these very dense stellar systems. These processes include close stellar encounters and direct physical collisions between stars. Such hydrodynamic stellar interactions are thought to explain the large populations of blue stragglers, millisecond pulsars, X-ray binaries, and other peculiar sources observed in globular clusters. Three-dimensional hydrodynamics techniques now make it possible to perform realistic numerical simulations of these interactions. The results, when combined with those of N-body simulations of stellar dynamics, should provide for the first time a realistic description of dense star clusters. Here I review briefly current theoretical work on hydrodynamic stellar interactions, emphasizing its relevance to recent observations.
Determining hydrodynamic boundary conditions from equilibrium fluctuations
NASA Astrophysics Data System (ADS)
Chen, Shuyu; Wang, Han; Qian, Tiezheng; Sheng, Ping
2015-10-01
The lack of a first-principles derivation has made the hydrodynamic boundary condition a classical issue for the past century. The fact that the fluid can have interfacial structures adds additional complications and ambiguities to the problem. Here we report the use of molecular dynamics to identify from equilibrium thermal fluctuations the hydrodynamic modes in a fluid confined by solid walls, thereby extending the application of the fluctuation-dissipation theorem to yield not only the accurate location of the hydrodynamic boundary at the molecular scale, but also the relevant parameter value(s) for the description of the macroscopic boundary condition. We present molecular dynamics results on two examples to illustrate the application of this approach—one on the hydrophilic case and one on the hydrophobic case. It is shown that the use of the orthogonality condition of the modes can uniquely locate the hydrodynamic boundary to be inside the fluid in both cases, separated from the molecular solid-liquid interface by a small distance Δ that is a few molecules in size. The eigenvalue equation of the hydrodynamic modes directly yields the slip length, which is about equal to Δ in the hydrophilic case but is larger than Δ in the hydrophobic case. From the decay time we also obtain the bulk viscosity which is in good agreement with the value obtained from dynamic simulations. To complete the picture, we derive the Green-Kubo relation for a finite fluid system and show that the boundary fluctuations decouple from the bulk only in the infinite-fluid-channel limit; and in that limit we recover the interfacial fluctuation-dissipation theorem first presented by Bocquet and Barrat. The coupling between the bulk and the boundary fluctuations provides both the justification and the reason for the effectiveness of the present approach, which promises broad utility for probing the hydrodynamic boundary conditions relevant to structured or elastic interfaces, as well as
Supernova hydrodynamics experiments using the Nova laser
Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A.; Kane, J.; Arnett, D.; Drake, R.P.; McCray, R.
1997-04-01
We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.
CSF hydrodynamics in superior sagittal sinus thrombosis.
Kristensen, B; Malm, J; Markgren, P; Ekstedt, J
1992-01-01
Cerebrospinal fluid hydrodynamics were investigated with a constant pressure infusion method in patients with superior sagittal sinus thrombosis. Ten patients were studied with serial examinations up to 15 years after the onset of the disease. A total of 70 CSF hydrodynamic examinations were performed. A clear increase in intracranial pressure due to raised pressure in the major dural sinus was seen in all patients. A striking feature was the persistent intracranial pressure increase that declined only gradually. This had no obvious clinical impact. Change in CSF resorption facility played only a minor role in the intracranial pressure elevation. None of the patients developed hydrocephalus. PMID:1583513
Hydrodynamic interactions between nearby slender filaments
NASA Astrophysics Data System (ADS)
Man, Yi; Koens, Lyndon; Lauga, Eric
2016-10-01
Cellular biology abound with filaments interacting through fluids, from intracellular microtubules, to rotating flagella and beating cilia. While previous work has demonstrated the complexity of capturing nonlocal hydrodynamic interactions between moving filaments, the problem remains difficult theoretically. We show here that when filaments are closer to each other than their relevant length scale, the integration of hydrodynamic interactions can be approximately carried out analytically. This leads to a set of simplified local equations, illustrated on a simple model of two interacting filaments, which can be used to tackle theoretically a range of problems in biology and physics.
Integration of hydrodynamic interactions between filaments
NASA Astrophysics Data System (ADS)
Man, Yi; Lauga, Eric
2015-11-01
In many biological situations, slender filaments interact through a viscous fluid, and these hydrodynamic interactions play a crucial cellular role. Examples include the ability of peritrichous bacteria to bundle their flagella or the generation of metachronal waves in cilia arrays. In most cases of interest, three distinct length scales characterize the filaments, their typical thickness a, relative distance h, and length L, which are asymptotically separated as a << h << L . In this talk, we demonstrate how to analytically develop a long-wavelength integration of hydrodynamic singularities in this biologically-relevant limit.
Hydrodynamic trap for single particles and cells
Tanyeri, Melikhan; Johnson-Chavarria, Eric M.; Schroeder, Charles M.
2010-01-01
Trapping and manipulation of microscale and nanoscale particles is demonstrated using the sole action of hydrodynamic forces. We developed an automated particle trap based on a stagnation point flow generated in a microfluidic device. The hydrodynamic trap enables confinement and manipulation of single particles in low viscosity (1–10 cP) aqueous solution. Using this method, we trapped microscale and nanoscale particles (100 nm–15 μm) for long time scales (minutes to hours). We demonstrate particle confinement to within 1 μm of the trap center, corresponding to a trap stiffness of ∼10−5–10−4 pN∕nm. PMID:20585593
Holography and hydrodynamics in small systems
NASA Astrophysics Data System (ADS)
Chesler, Paul M.
2016-12-01
Using holographic duality, we present results for the off-center collision of Gaussian wave packets in strongly coupled N = 4 supersymmetric Yang-Mills theory. The wave packets are thin along the collision axis and superficially at least resemble Lorentz contracted colliding protons. The collision results in the formation of a droplet of liquid of size R ∼ 1 /Teff where Teff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as proton-proton collisions.
Circumstellar Hydrodynamics and Spectral Radiation in ALGOLS
NASA Astrophysics Data System (ADS)
Terrell, Dirk Curtis
1994-01-01
Algols are the remnants of binary systems that have undergone large scale mass transfer. This dissertation presents the results of the coupling of a hydrodynamical model and a radiative model of the flow of gas from the inner Lagrangian point. The hydrodynamical model is a fully Lagrangian, three-dimensional scheme with a novel treatment of viscosity and an implementation of the smoothed particle hydrodynamics method to compute pressure gradients. Viscosity is implemented by allowing particles within a specified interaction length to share momentum. The hydrodynamical model includes a provision for computing the self-gravity of the disk material, although it is not used in the present application to Algols. Hydrogen line profiles and equivalent widths computed with a code by Drake and Ulrich are compared with observations of both short and long period Algols. More sophisticated radiative transfer computations are done with the escape probability code of Ko and Kallman which includes the spectral lines of thirteen elements. The locations and velocities of the gas particles, and the viscous heating from the hydro program are supplied to the radiative transfer program, which computes the equilibrium temperature of the gas and generates its emission spectrum. Intrinsic line profiles are assumed to be delta functions and are properly Doppler shifted and summed for gas particles that are not eclipsed by either star. Polarization curves are computed by combining the hydro program with the Wilson-Liou polarization program. Although the results are preliminary, they show that polarization observations show great promise for studying circumstellar matter.
Simple Waves in Ideal Radiation Hydrodynamics
Johnson, B M
2008-09-03
In the dynamic diffusion limit of radiation hydrodynamics, advection dominates diffusion; the latter primarily affects small scales and has negligible impact on the large scale flow. The radiation can thus be accurately regarded as an ideal fluid, i.e., radiative diffusion can be neglected along with other forms of dissipation. This viewpoint is applied here to an analysis of simple waves in an ideal radiating fluid. It is shown that much of the hydrodynamic analysis carries over by simply replacing the material sound speed, pressure and index with the values appropriate for a radiating fluid. A complete analysis is performed for a centered rarefaction wave, and expressions are provided for the Riemann invariants and characteristic curves of the one-dimensional system of equations. The analytical solution is checked for consistency against a finite difference numerical integration, and the validity of neglecting the diffusion operator is demonstrated. An interesting physical result is that for a material component with a large number of internal degrees of freedom and an internal energy greater than that of the radiation, the sound speed increases as the fluid is rarefied. These solutions are an excellent test for radiation hydrodynamic codes operating in the dynamic diffusion regime. The general approach may be useful in the development of Godunov numerical schemes for radiation hydrodynamics.
Hydrodynamic dispersion of microswimmers in suspension
NASA Astrophysics Data System (ADS)
Martin, Matthieu; Rafaï, Salima; Peyla, Philippe
2014-11-01
In our laboratory, we study hydrodynamics of suspensions of micro-swimmers. These micro-organisms are unicellular algae Chlamydomonas Rheinhardii which are able to swim by using their flagella. The swimming dynamics of these micro-swimmers can be seen as a random walk, in absence of any kind of interaction. In addition, these algae have the property of being phototactic, i.e. they swim towards the light. Combining this property with a hydrodynamic flow, we were able to reversibly separate algae from the rest of the fluid. But for sufficiently high volume fraction, these active particles interact with each other. We are now interested in how the coupling of hydrodynamic interactions between swimmers and phototaxis can modify the swimming dynamics at the scale of the suspension. To this aim, we conduct experiments in microfluidic devices to study the dispersion of the micro-organisms in a the liquid phase as a function of the volume fraction. We show that the dispersion of an assembly of puller type microswimmers is quantitatively affected by hydrodynamics interactions. Phd student.
Superreflection of waves in hydrodynamic flows
Fabrikant, A.L.
1987-08-01
The amplification mechanism of various type waves in hydrodynamics in analyzed for reflection from planar and cylindrical tangential discontinuities. The problem of wave momentum and energy in a medium is discussed. The amplification is related to the presence of negative energy waves.
Boundary conditions in tunneling via quantum hydrodynamics
NASA Technical Reports Server (NTRS)
Nassar, Antonio B.
1993-01-01
Via the hydrodynamical formulation of quantum mechanics, an approach to the problem of tunneling through sharp-edged potential barriers is developed. Above all, it is shown how more general boundary conditions follow from the continuity of mass, momentum, and energy.
Impact modeling with Smooth Particle Hydrodynamics
Stellingwerf, R.F.; Wingate, C.A.
1992-01-01
Smooth Particle Hydrodynamics (SPH) is a new computational technique uniquely suited to computation of hypervelocity impact phenomena. This paper reviews the characteristics, philosophy, and a bit of the derivation of the method. As illustrations of the technique, several test case computations and several application computations are shown.
Impact modeling with Smooth Particle Hydrodynamics
Stellingwerf, R.F.; Wingate, C.A.
1992-09-01
Smooth Particle Hydrodynamics (SPH) is a new computational technique uniquely suited to computation of hypervelocity impact phenomena. This paper reviews the characteristics, philosophy, and a bit of the derivation of the method. As illustrations of the technique, several test case computations and several application computations are shown.
Dilepton production in schematic causal viscous hydrodynamics
NASA Astrophysics Data System (ADS)
Song, Taesoo; Han, Kyong Chol; Ko, Che Ming
2011-02-01
Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of 1/4π for the initial quark-gluon plasma (QGP) phase and of 10 times this value for the later hadron-gas (HG) phase. Using the production rate evaluated with particle distributions that take into account the viscous effect, we study dilepton production in central heavy-ion collisions. Compared with results from the ideal hydrodynamics, we find that although the dilepton invariant mass spectra from the two approaches are similar, the transverse momentum spectra are significantly enhanced at high transverse momenta by the viscous effect. We also study the transverse momentum dependence of dileptons produced from QGP for a fixed transverse mass, which is essentially absent in the ideal hydrodynamics, and find that this so-called transverse mass scaling is violated in the viscous hydrodynamics, particularly at high transverse momenta.
Resonant frequencies of the hydrodynamic vortex
NASA Astrophysics Data System (ADS)
Vieira, H. S.
We study the sound perturbation of the hydrodynamic vortex geometry and present an exact expression for the resonant frequencies (quasispectrum) of this geometry. Exact solution for the radial part of the covariant Klein-Gordon equation in this spacetime is obtained, and is given in terms of the double confluent Heun functions. We found that the resonant frequencies are complex number.
Using Pulsed Power for Hydrodynamic Code Validation
2001-06-01
Air Force Research Laboratory ( AFRL ). A...bank at the Air Force Research Laboratory ( AFRL ). A cylindrical aluminum liner that is magnetically imploded onto a central target by self-induced...James Degnan, George Kiuttu Air Force Research Laboratory Albuquerque, NM 87117 Abstract As part of ongoing hydrodynamic code
Microflow cytometers with integrated hydrodynamic focusing.
Frankowski, Marcin; Theisen, Janko; Kummrow, Andreas; Simon, Peter; Ragusch, Hülya; Bock, Nicole; Schmidt, Martin; Neukammer, Jörg
2013-04-09
This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex) principle. The sample--A suspension of micro particles or blood cells--is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.
Hydrodynamic focusing--a versatile tool.
Golden, Joel P; Justin, Gusphyl A; Nasir, Mansoor; Ligler, Frances S
2012-01-01
The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application.
Hydrodynamic simulations of the core helium flash
NASA Astrophysics Data System (ADS)
Mocák, Miroslav; Müller, Ewald; Weiss, Achim; Kifonidis, Konstantinos
2008-10-01
We desribe and discuss hydrodynamic simulations of the core helium flash using an initial model of a 1.25 M⊙ star with a metallicity of 0.02 near at its peak. Past research concerned with the dynamics of the core helium flash is inconclusive. Its results range from a confirmation of the standard picture, where the star remains in hydrostatic equilibrium during the flash (Deupree 1996), to a disruption or a significant mass loss of the star (Edwards 1969; Cole & Deupree 1980). However, the most recent multidimensional hydrodynamic study (Dearborn et al. 2006) suggests a quiescent behavior of the core helium flash and seems to rule out an explosive scenario. Here we present partial results of a new comprehensive study of the core helium flash, which seem to confirm this qualitative behavior and give a better insight into operation of the convection zone powered by helium burning during the flash. The hydrodynamic evolution is followed on a computational grid in spherical coordinates using our new version of the multi-dimensional hydrodynamic code HERAKLES, which is based on a direct Eulerian implementation of the piecewise parabolic method.
Stabilizing geometry for hydrodynamic rotary seals
Dietle, Lannie L.; Schroeder, John E.
2010-08-10
A hydrodynamic sealing assembly including a first component having first and second walls and a peripheral wall defining a seal groove, a second component having a rotatable surface relative to said first component, and a hydrodynamic seal comprising a seal body of generally ring-shaped configuration having a circumference. The seal body includes hydrodynamic and static sealing lips each having a cross-sectional area that substantially vary in time with each other about the circumference. In an uninstalled condition, the seal body has a length defined between first and second seal body ends which varies in time with the hydrodynamic sealing lip cross-sectional area. The first and second ends generally face the first and second walls, respectively. In the uninstalled condition, the first end is angulated relative to the first wall and the second end is angulated relative to the second wall. The seal body has a twist-limiting surface adjacent the static sealing lip. In the uninstalled condition, the twist-limiting surface is angulated relative to the peripheral wall and varies along the circumference. A seal body discontinuity and a first component discontinuity mate to prevent rotation of the seal body relative to the first component.
Hydrodynamic coupling between two fluid membranes.
Ramachandran, Sanoop; Komura, Shigeyuki
2011-02-23
The coupled in-plane diffusion dynamics between point-particles embedded in stacked fluid membranes is investigated. We calculate the contributions to the coupling longitudinal and transverse diffusion coefficients due to particle motion within the different as well as the same membranes. The stacked geometry leads to a hydrodynamic coupling between the two membranes.
Does Suspension Crowding Screen Hydrodynamic Interactions?
NASA Astrophysics Data System (ADS)
Su, Yu; Zia, Roseanna N.; Swan, James W.
2015-03-01
Resistance and mobility functions describe linear couplings between moments of the hydrodynamic traction on a suspended particle and the motion of that or other particles. For two isolated spheres, these functions are well known and have been applied directly in the solution of many important problems for dilute colloidal dispersions. We have devised a new stochastic technique to calculate an analogous set of functions for two spheres immersed in a suspension that are then used to model the near-equilibrium dynamics of concentrated dispersions, including viscoelasticity and long-time diffusion. Of interest is the degree of screening of hydrodynamic interactions by the intervening medium. We find that the mobility is unscreened at the pair level, even in suspensions of high concentration, confirming that hydrodynamic interactions are an essential part of the dynamics of crowded systems and cannot be neglected in favor of simple renormalization schemes. We compare our results for the hydrodynamic interactions between suspended particles to predictions from two-point microrheology. This technique can be used to infer the complex viscosity from long-ranged decay of the pair mobility in viscoelastic materials.
Does Suspension Crowding Screen Hydrodynamic Interactions?
NASA Astrophysics Data System (ADS)
Zia, Roseanna; Swan, James; Su, Yu
2014-11-01
Resistance and mobility functions describe linear couplings between moments of the hydrodynamic traction on a suspended particle and the motion of that or other suspended particles. For two isolated spheres, these functions are well known and have been applied directly in the solution of many important problems for dilute colloidal dispersions. We have devised a new stochastic technique to calculate an analogous set of functions for two spheres immersed in a suspension that are then used to model the near-equilibrium dynamics of concentrated dispersions, including viscoelasticity and long-time diffusion. Of interest is the degree of screening of hydrodynamic interactions by the intervening medium. We find that the mobility is unscreened at the pair level, even in suspensions of high concentration, confirming that hydrodynamic interactions are an essential part of the dynamics of crowded systems and cannot be neglected in favor of simple renormalization schemes. We compare our results for the hydrodynamic interactions between suspended particles to predictions from two-point microrheology. This technique can be used to infer the complex viscosity from long-ranged decay of the pair mobility in viscoelastic materials. Its validity when not in the continuum limit is addressed.
Hydrodynamics and Roughness of Irregular Boundaries
2011-01-01
principle component analysis (PCA) similar to that used by Preston (2009) for ship- mounted multibeam data. Several variables derived from the...complex boundaries as well as characterization of acoustic and optical processes. Turbulent processes at the seabed are at the foundation of littoral...nearshore hydrodynamics, turbulence over rough beds influences optical and acoustic properties. Bed roughness also directly affects acoustic propagation in
Macroscopic liquid-state molecular hydrodynamics
Keanini, R. G.; Tkacik, Peter T.; Fleischhauer, Eric; Shahinian, Hossein; Sholar, Jodie; Azimi, Farzad; Mullany, Brid
2017-01-01
Experimental evidence and theoretical modeling suggest that piles of confined, high-restitution grains, subject to low-amplitude vibration, can serve as experimentally-accessible analogs for studying a range of liquid-state molecular hydrodynamic processes. Experiments expose single-grain and multiple-grain, collective dynamic features that mimic those either observed or predicted in molecular-scale, liquid state systems, including: (i) near-collision-time-scale hydrodynamic organization of single-molecule dynamics, (ii) nonequilibrium, long-time-scale excitation of collective/hydrodynamic modes, and (iii) long-time-scale emergence of continuum, viscous flow. In order to connect directly observable macroscale granular dynamics to inaccessible and/or indirectly measured molecular hydrodynamic processes, we recast traditional microscale equilibrium and nonequilibrium statistical mechanics for dense, interacting microscale systems into self-consistent, macroscale form. The proposed macroscopic models, which appear to be new with respect to granular physics, and which differ significantly from traditional kinetic-theory-based, macroscale statistical mechanics models, are used to rigorously derive the continuum equations governing viscous, liquid-like granular flow. The models allow physically-consistent interpretation and prediction of observed equilibrium and non-equilibrium, single-grain, and collective, multiple-grain dynamics. PMID:28139711
Karsch,F.; Kharzeev, D.; Molnar, K.; Petreczky, P.; Teaney, D.
2008-04-21
The interpretation of relativistic heavy-ion collisions at RHIC energies with thermal concepts is largely based on the relative success of ideal (nondissipative) hydrodynamics. This approach can describe basic observables at RHIC, such as particle spectra and momentum anisotropies, fairly well. On the other hand, recent theoretical efforts indicate that dissipation can play a significant role. Ideally viscous hydrodynamic simulations would extract, if not only the equation of state, but also transport coefficients from RHIC data. There has been a lot of progress with solving relativistic viscous hydrodynamics. There are already large uncertainties in ideal hydrodynamics calculations, e.g., uncertainties associated with initial conditions, freezeout, and the simplified equations of state typically utilized. One of the most sensitive observables to the equation of state is the baryon momentum anisotropy, which is also affected by freezeout assumptions. Up-to-date results from lattice quantum chromodynamics on the transition temperature and equation of state with realistic quark masses are currently available. However, these have not yet been incorporated into the hydrodynamic calculations. Therefore, the RBRC workshop 'Hydrodynamics in Heavy Ion Collisions and QCD Equation of State' aimed at getting a better understanding of the theoretical frameworks for dissipation and near-equilibrium dynamics in heavy-ion collisions. The topics discussed during the workshop included techniques to solve the dynamical equations and examine the role of initial conditions and decoupling, as well as the role of the equation of state and transport coefficients in current simulations.
NASA Astrophysics Data System (ADS)
Gusti, T. P.; Hertanti, D. R.; Bahsan, E.; Soeryantono, H.
2013-12-01
Particle-based numerical methods, such as Smoothed Particle Hydrodynamics (SPH), may be able to simulate some hydrodynamic and morphodynamic behaviors better than grid-based numerical methods. This study simulates hydrodynamics in meanders and advection and turbulent diffusion in straight river channels using Microsoft Excel and Visual Basic. The simulators generate three-dimensional data for hydrodynamics and one-dimensional data for advection-turbulent diffusion. Fluid at rest, sloshing, and helical flow are simulated in the river meanders. Spill loading and step loading are done to simulate concentration patterns associated with advection-turbulent diffusion. Results indicate that helical flow is formed due to disturbance in morphology and particle velocity in the stream and the number of particles does not have a significant effect on the pattern of advection-turbulent diffusion concentration.
Scaling supernova hydrodynamics to the laboratory
Kane, J. O.
1999-06-01
Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al., Astrophys. J.478, L75 (1997) The Nova laser is used to shock two-layer targets, producing Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the interfaces between the layers, analogous to instabilities seen at the interfaces of SN 1987A. Because the hydrodynamics in the laser experiments at intermediate times (3-40 ns) and in SN 1987A at intermediate times (5 s-10^{4} s) are well described by the Euler equations, the hydrodynamics scale between the two regimes. The experiments are modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS, thus serving as a benchmark for PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike and bubble velocities in the experiment using potential flow theory and a modified Ott thin shell theory is presented. A numerical study of 2D vs. 3D differences in instability growth at the O-He and He-H interface of SN 1987A, and the design for analogous laser experiments are presented. We discuss further work to incorporate more features of the SN in the experiments, including spherical geometry, multiple layers and density gradients. Past and ongoing work in laboratory and laser astrophysics is reviewed, including experimental work on supernova remnants (SNRs). A numerical study of RM instability in SNRs is presented.
Scaling supernova hydrodynamics to the laboratory
Kane, J.; Arnett, D.; Remington, B.A.; Glendinning, S.G.; Bazan, G.; Drake, R.P.; Fryxell, B.A.; Teyssier, R.
1999-05-01
Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane {ital et al.} [Astrophys. J. {bold 478}, L75 (1997) and B. A. Remington {ital et al.}, Phys. Plasmas {bold 4}, 1994 (1997)]. The Nova laser is used to generate a 10{endash}15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth due to the Richtmyer{endash}Meshkov instability, and to the Rayleigh{endash}Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few {times}10{sup 3}s. The scaling of hydrodynamics on microscopic laser scales to the SN-size scales is presented. The experiment is modeled using the hydrodynamics codes HYADES [J. T. Larson and S. M. Lane, J. Quant. Spect. Rad. Trans. {bold 51}, 179 (1994)] and CALE [R. T. Barton, {ital Numerical Astrophysics} (Jones and Bartlett, Boston, 1985), pp. 482{endash}497], and the supernova code PROMETHEUS [P. R. Woodward and P. Collela, J. Comp. Phys. {bold 54}, 115 (1984)]. Results of the experiments and simulations are presented. Analysis of the spike-and-bubble velocities using potential flow theory and Ott thin-shell theory is presented, as well as a study of 2D versus 3D differences in perturbation growth at the He-H interface of SN 1987A.
Scaling supernova hydrodynamics to the laboratory
NASA Astrophysics Data System (ADS)
Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Bazan, G.; Drake, R. P.; Fryxell, B. A.; Teyssier, R.; Moore, K.
1999-05-01
Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al. [Astrophys. J. 478, L75 (1997) and B. A. Remington et al., Phys. Plasmas 4, 1994 (1997)]. The Nova laser is used to generate a 10-15 Mbar shock at the interface of a two-layer planar target, which triggers perturbation growth due to the Richtmyer-Meshkov instability, and to the Rayleigh-Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few ×103 s. The scaling of hydrodynamics on microscopic laser scales to the SN-size scales is presented. The experiment is modeled using the hydrodynamics codes HYADES [J. T. Larson and S. M. Lane, J. Quant. Spect. Rad. Trans. 51, 179 (1994)] and CALE [R. T. Barton, Numerical Astrophysics (Jones and Bartlett, Boston, 1985), pp. 482-497], and the supernova code PROMETHEUS [P. R. Woodward and P. Collela, J. Comp. Phys. 54, 115 (1984)]. Results of the experiments and simulations are presented. Analysis of the spike-and-bubble velocities using potential flow theory and Ott thin-shell theory is presented, as well as a study of 2D versus 3D differences in perturbation growth at the He-H interface of SN 1987A.
Yang, Zhaoqing; Khangaonkar, Tarang; Wang, Taiping
2010-08-01
In this report we describe the 1) the expansion of the PNNL hydrodynamic model domain to include the continental shelf along the coasts of Washington, Oregon, and Vancouver Island; and 2) the approach and progress in developing the online/Internet disseminations of model results and outreach efforts in support of the Puget Sound Operational Forecast System (PS-OPF). Submittal of this report completes the work on Task 2.1.2, Effects of Physical Systems, Subtask 2.1.2.1, Hydrodynamics, for fiscal year 2010 of the Environmental Effects of Marine and Hydrokinetic Energy project.
1986-12-01
Version 00 The MEDUSA-IB code performs implosion and thermonuclear burn calculations of an ion beam driven ICF target, based on one-dimensional plasma hydrodynamics and transport theory. It can calculate the following values in spherical geometry through the progress of implosion and fuel burnup of a multi-layered target. (1) Hydrodynamic velocities, density, ion, electron and radiation temperature, radiation energy density, Rs and burn rate of target as a function of coordinates and time, (2) Fusion gain as a function of time, (3) Ionization degree, (4) Temperature dependent ion beam energy deposition, (5) Radiation, -particle and neutron spectra as a function of time.
A two-dimensional hydrodynamic model of a tidal estuary
Walters, Roy A.; Cheng, Ralph T.
1979-01-01
A finite element model is described which is used in the computation of tidal currents in an estuary. This numerical model is patterned after an existing algorithm and has been carefully tested in rectangular and curve-sided channels with constant and variable depth. One of the common uncertainties in this class of two-dimensional hydrodynamic models is the treatment of the lateral boundary conditions. Special attention is paid specifically to addressing this problem. To maintain continuity within the domain of interest, ‘smooth’ curve-sided elements must be used at all shoreline boundaries. The present model uses triangular, isoparametric elements with quadratic basis functions for the two velocity components and a linear basis function for water surface elevation. An implicit time integration is used and the model is unconditionally stable. The resultant governing equations are nonlinear owing to the advective and the bottom friction terms and are solved iteratively at each time step by the Newton-Raphson method. Model test runs have been made in the southern portion of San Francisco Bay, California (South Bay) as well as in the Bay west of Carquinez Strait. Owing to the complex bathymetry, the hydrodynamic characteristics of the Bay system are dictated by the generally shallow basins which contain deep, relict river channels. Great care must be exercised to ensure that the conservation equations remain locally as well as globally accurate. Simulations have been made over several representative tidal cycles using this finite element model, and the results compare favourably with existing data. In particular, the standing wave in South Bay and the progressive wave in the northern reach are well represented.
Scaling Laws for Hydrodynamically Equivalent Implosions
NASA Astrophysics Data System (ADS)
Murakami, Masakatsu
2001-10-01
The EPOC (equivalent physics of confinement) scenario for the proof of principle of high gain inertial confinement fusion is presented, where the key concept "hydrodynamically equivalent implosions" plays a crucial role. Scaling laws on the target and confinement parameters are derived by applying the Lie group analysis to the PDE (partially differential equations) chain of the hydrodynamic system. It turns out that the conventional scaling law based on adiabatic approximation significantly differs from one which takes such energy transport effect as electron heat conduction into account. Confinement plasma parameters of the hot spot such as the central temperature and the areal mass density at peak compression are obtained with a self-similar solution for spherical implosions.
HYDRODYNAMIC SIMULATION OF THE UPPER POTOMAC ESTUARY.
Schaffranck, Raymond W.
1986-01-01
Hydrodynamics of the upper extent of the Potomac Estuary between Indian Head and Morgantown, Md. , are simulated using a two-dimensional model. The model computes water-surface elevations and depth-averaged velocities by numerically integrating finite-difference forms of the equations of mass and momentum conservation using the alternating direction implicit method. The fundamental, non-linear, unsteady-flow equations, upon which the model is formulated, include additional terms to account for Coriolis acceleration and meteorological influences. Preliminary model/prototype data comparisons show agreement to within 9% for tidal flow volumes and phase differences within the measured-data-recording interval. Use of the model to investigate the hydrodynamics and certain aspects of transport within this Potomac Estuary reach is demonstrated. Refs.
Anisotropic hydrodynamic turbulence in accretion disks
NASA Astrophysics Data System (ADS)
Stoll, Moritz H. R.; Kley, Wilhelm; Picogna, Giovanni
2017-03-01
Recently, the vertical shear instability (VSI) has become an attractive purely hydrodynamic candidate for the anomalous angular momentum transport required for weakly ionized accretion disks. In direct three-dimensional numerical simulations of VSI turbulence in disks, a meridional circulation pattern was observed that is opposite to the usual viscous flow behavior. Here, we investigate whether this feature can possibly be explained by an anisotropy of the VSI turbulence. Using three-dimensional hydrodynamical simulations, we calculate the turbulent Reynolds stresses relevant for angular momentum transport for a representative section of a disk. We find that the vertical stress is significantly stronger than the radial stress. Using our results in viscous disk simulations with different viscosity coefficients for the radial and vertical direction, we find good agreement with the VSI turbulence for the stresses and meridional flow; this provides additional evidence for the anisotropy. The results are important with respect to the transport of small embedded particles in disks.
Filter-less submicron hydrodynamic size sorting.
Fouet, M; Mader, M-A; Iraïn, S; Yanha, Z; Naillon, A; Cargou, S; Gué, A-M; Joseph, P
2016-02-21
We propose a simple microfluidic device able to separate submicron particles (critical size ∼0.1 μm) from a complex sample with no filter (minimum channel dimension being 5 μm) by hydrodynamic filtration. A model taking into account the actual velocity profile and hydrodynamic resistances enables prediction of the chip sorting properties for any geometry. Two design families are studied to obtain (i) small sizes within minutes (low-aspect ratio, two-level chip) and (ii) micron-sized sorting with a μL flow rate (3D architecture based on lamination). We obtain quantitative agreement of sorting performances both with experiments and with numerical solving, and determine the limits of the approach. We therefore demonstrate a passive, filter-less sub-micron size sorting with a simple, robust, and easy to fabricate design.
Structure and hydrodynamics of colloidal systems
Hayter, J.B.
1985-07-01
Colloidal phases (for example, micellar solutions, latex suspensions, ferrofluids and microemulsions) provide excellent model systems with which to test structural and hydrodynamic theories of the liquid state. Interparticle potentials may be attractive or repulsive, and the experimentalist is often free to control the strength, range and symmetry of the interactions. Small-angle neutron scattering (SANS) and small-angle neutron spin-echo (SANSE) provide excellent complementary tools for studying the structure and time-dependence of these systems, where correlation lengths typically vary from about one to several tens of nm. Correlation times are usually in the nsec to ..mu..sec range, but may be of order minutes in certain systems. This paper will review some of the current theories and their recent experimental tests, using colloidal systems in which the direct interaction potentials may have spherical, dipolar or cylindrical symmetry and the hydrodynamic interactions may be weak or strong.
SPHGR: Smoothed-Particle Hydrodynamics Galaxy Reduction
NASA Astrophysics Data System (ADS)
Thompson, Robert
2015-02-01
SPHGR (Smoothed-Particle Hydrodynamics Galaxy Reduction) is a python based open-source framework for analyzing smoothed-particle hydrodynamic simulations. Its basic form can run a baryonic group finder to identify galaxies and a halo finder to identify dark matter halos; it can also assign said galaxies to their respective halos, calculate halo & galaxy global properties, and iterate through previous time steps to identify the most-massive progenitors of each halo and galaxy. Data about each individual halo and galaxy is collated and easy to access. SPHGR supports a wide range of simulations types including N-body, full cosmological volumes, and zoom-in runs. Support for multiple SPH code outputs is provided by pyGadgetReader (ascl:1411.001), mainly Gadget (ascl:0003.001) and TIPSY (ascl:1111.015).
Cerebrospinal fluid hydrodynamic studies in children.
Blomquist, H K; Sundin, S; Ekstedt, J
1986-01-01
CSF-hydrodynamic investigation using the constant pressure infusion method was used in children. The CSF resting pressure was recorded and the CSF formation rate was measured. The conductance of the CSF outflow pathways and the pressure in the sagittal sinus were calculated. The method was used in children with suspicion of disturbed CSF hydrodynamics due to various neurological and other conditions. The method is applicable in paediatric neurological diagnostics and provides information for further understanding of the mechanisms behind cranial hypertension. The following mean values are offered as reference values in clinical work and in further research in this field: CSF-resting pressure 1.3 kPa, sagittal sinus pressure 1.1 kPa, pressure difference across arachnoid villi 0.5 kPa, conductance of CSF outflow pathways 22.6 mm3 kPa-1s-1, CSF formation rate 6.8 m3s-1. PMID:3711916
Hydrodynamic synchronisation of optically driven rotors
NASA Astrophysics Data System (ADS)
Debono, Luke J.; Box, Stuart; Phillips, David B.; Simpson, Stephen H.; Hanna, Simon
2015-08-01
Hydrodynamic coupling is thought to play a role in the coordinated beating of cilia and flagella, and may inform the future design of artificial swimmers and pumps. In this study, optical tweezers are used to investigate the hydrodynamic coupling between a pair of driven oscillators. The theoretical model of Lenz and Ryskin [P. Lenz and A. Ryskin, Phys. Biol. 3, 285{294 (2006)] is experimentally recreated, in which each oscillator consists of a sphere driven in a circular trajectory. The optical trap position is maintained ahead of the sphere to provide a tangential driving force. The trap is also moved radially to harmonically constrain the sphere to the circular trajectory. Analytically, it has been shown that two oscillators of this type are able to synchronise or phase-lock under certain conditions. We explore the interplay between synchronisation mechanisms and find good agreement between experiment, theory and Brownian dynamics simulations.
Hydrodynamics with spin in bacterial suspensions
NASA Astrophysics Data System (ADS)
Belovs, M.; CÄ`bers, A.
2016-06-01
We describe a kind of self-propelling motion of bacteria based on the cooperative action of rotating flagella on the surface of bacteria. Describing the ensemble of rotating flagella in the framework of the hydrodynamics with spin, the reciprocal theorem of Stokesian hydrodynamics is generalized accordingly. The velocity of the self-propulsion is expressed in terms of the characteristics of the vector field of flagella orientation and it is shown that the unusually high velocities of Thiovulum majus bacteria may be explained by the cooperative action of the rotating flagella. The expressions obtained enable us to estimate the torque created by the rotary motors of the bacterium and show quantitative agreement with the existing experimental data.
Hydrodynamic interaction of bacterial flagella - flagellar bundling
NASA Astrophysics Data System (ADS)
Lim, Sookkyung
2013-11-01
Flagellar bundling is an important aspect of locomotion in bacteria such as Escherichia coli. To study the hydrodynamic behavior of helical flagella, we present a computational model that is based on the geometry of the bacterial flagellar filament at the micrometer scale. We consider two model flagella, each of which has a rotary motor at its base with the rotation rate of the motor set at 100 Hz. Bundling occurs when both flagella are left-handed helices turning counterclockwise (when viewed from the nonmotor end of the flagellum looking back toward the motor) or when both flagella are right-handed helices turning clockwise. Helical flagella of the other combinations of handedness and rotation direction do not bundle. In this work we use the generalized immersed boundary method combined with the unconstrained Kirchhoff rod theory, which allows us to study the complicated hydrodynamics of flagellar behavior. This is a joint work with Charlie Peskin at NYU. NSF
Hyperbolic metamaterial lens with hydrodynamic nonlocal response.
Yan, Wei; Mortensen, N Asger; Wubs, Martijn
2013-06-17
We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens.
Supernova hydrodynamics experiments using the Nova laser*
NASA Astrophysics Data System (ADS)
Remington, B. A.; Glendinning, S. G.; Estabrook, K. G.; London, R. A.; Wallace, R. J.; Kane, J.; Arnett, D.; Drake, R. P.; Liang, E.; McCray, R.; Rubenchik, A.
1997-04-01
We are developing experiments using the Nova laser [1,2] to investigate two areas of physics relevant to core-collapse supernovae (SN): compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications will be discussed. *Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48. [1] J. Kane et al., in press, Astrophys. J. Lett. (March-April, 1997). [2] B.A. Remington et al., in press, Phys. Plasmas (May, 1997).
TORUS: Radiation transport and hydrodynamics code
NASA Astrophysics Data System (ADS)
Harries, Tim
2014-04-01
TORUS is a flexible radiation transfer and radiation-hydrodynamics code. The code has a basic infrastructure that includes the AMR mesh scheme that is used by several physics modules including atomic line transfer in a moving medium, molecular line transfer, photoionization, radiation hydrodynamics and radiative equilibrium. TORUS is useful for a variety of problems, including magnetospheric accretion onto T Tauri stars, spiral nebulae around Wolf-Rayet stars, discs around Herbig AeBe stars, structured winds of O supergiants and Raman-scattered line formation in symbiotic binaries, and dust emission and molecular line formation in star forming clusters. The code is written in Fortran 2003 and is compiled using a standard Gnu makefile. The code is parallelized using both MPI and OMP, and can use these parallel sections either separately or in a hybrid mode.
The Radiation Transport Conundrum in Radiation Hydrodynamics
Castor, J I
2005-03-18
The summary of this paper is: (1) The conundrum in the title is whether to treat radiation in the lab frame or the comoving frame in a radiation-hydrodynamic problem; (2) Several of the difficulties are associated with combining a somewhat relativistic treatment of radiation with a non-relativistic treatment of hydrodynamics; (3) The principal problem is a tradeoff between easily obtaining the correct diffusion limit and describing free-streaming radiation with the correct wave speed; (4) The computational problems of the comoving-frame formulation in more than one dimension, and the difficulty of obtaining both exact conservation and full u/c accuracy argue against this method; (5) As the interest in multi-D increases, as well as the power of computers, the lab-frame method is becoming more attractive; and (6) The Monte Carlo method combines the advantages of both lab-frame and comoving-frame approaches, its only disadvantage being cost.
The hydrodynamics of water-walkers
NASA Astrophysics Data System (ADS)
Hu, David L.; Bush, John W. M.
2004-11-01
Legged propulsion on the water surface is accomplished through a variety of means by birds, reptiles and insects. Examples include walking, rowing, hopping and capillary locomotion via deformation of the free surface. We here present experimental observations that yield insight into the scaling of water-walking. Particular attention is given to categorizing water-walking creatures and their modes of propulsion according to the relative magnitudes of the hydrodynamic forces generated by their driving stroke.
Novel techniques for slurry bubble column hydrodynamics
Dudukovic, M.P.
1999-05-14
The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research Engineering Company was to improve the knowledge base for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. During the first year (July 1, 1995--June 30, 1996) of this three year program novel experimental tools (computer aided radioactive particle tracking (CARPT), particle image velocimetry (PIV), heat probe, optical fiber probe and gamma ray tomography) were developed and tuned for measurement of pertinent hydrodynamic quantities, such as velocity field, holdup distribution, heat transfer and bubble size. The accomplishments were delineated in the First Technical Annual Report. The second year (July, 1996--June 30, 1997) was spent on further development and tuning of the novel experimental tools (e.g., development of Monte Carlo calibration for CARPT, optical probe development), building up the hydrodynamic data base using these tools and comparison of the two techniques (PIV and CARPT) for determination of liquid velocities. A phenomenological model for gas and liquid backmixing was also developed. All accomplishments were summarized in the Second Annual Technical Report. During the third and final year of the program (July 1, 1997--June 30, 1998) and during the nine months no cost extension, the high pressure facility was completed and a set of data was taken at high pressure conditions. Both PIV, CT and CARPT were used. More fundamental hydrodynamic modeling was also undertaken and model predictions were compared to data. The accomplishments for this period are summarized in this report.
Hydrodynamic Flow Control in Marine Mammals
2008-05-06
Hydrodynamic flow control in marine mammals Frank E. Fish,1,* Laurens E. Howle† and Mark M. Murray§ Department of Biology, West Chester University...the flow of water around the body dictates the performance of marine mammals in the aquatic environment. Morphological specializations of marine mammals ...and maneuverability. The morphological features of marine mammals for flow control can be utilized in the biomimetic design of engineered structures
Hydrodynamic Noise from Flexible Roughness Elements
2015-06-29
of a sparse distribution of fibers that are hydrodynamically uncoupled, the influences of fiber bending and a background flow on the far field sound ...with companion experiments performed by Dr. William Devenport of Virginia Tech. 15. SUBJECT TERMS vortex sound , flexible rougnness, conformal mapping...aeroacoustic Green’s functions to find the far-field sound due to vortex motion. A separate analysis concerning noise suppression by the presence of
UV Polymerization of Hydrodynamically Shaped Fibers
2011-01-01
parallel.17 One other example of non-round fibers was originally reported in 199518 and was produced by co -extrusion of polymers with different...ordinary as there is a minimum required exposure to initiate polymerization as shown with other polymers .25 It was desirable to maintain the same exposure...UV polymerization of hydrodynamically shaped fibers† Abel L. Thangawng, Peter B. Howell, Jr, Christopher M. Spillmann, Jawad Naciri and Frances S
The Quantum Hydrodynamic Description of Tunneling
Kendrick, Brian K.
2012-06-15
The quantum hydrodynamic approach is based on the de Broglie-Bohm formulation of quantum mechanics. The resulting fluid-like equations of motion describe the flow of probability and an accurate solution to these equations is equivalent to solving the time-dependent Schroedinger equation. Furthermore, the hydrodynamic approach provides new insight into the mechanisms as well as an alternative computational approach for treating tunneling phenomena. New concepts include well-defined 'quantum trajectories', 'quantum potential', and 'quantum force' all of which have classical analogues. The quantum potential and its associated force give rise to all quantum mechanical effects such as zero point energy, tunneling, and interference. A new numerical approach called the Iterative Finite Difference Method (IFDM) will be discussed. The IFDM is used to solve the set of non-linear coupled hydrodynamic equations. It is 2nd-order accurate in both space and time and exhibits exponential convergence with respect to the iteration count. The stability and computational efficiency of the IFDM is significantly improved by using a 'smart' Eulerian grid which has the same computational advantages as a Lagrangian or Arbitrary Lagrangian Eulerian (ALE) grid. The IFDM is also capable of treating anharmonic potentials. Example calculations using the IFDM will be presented which include: a one-dimensional Gaussian wave packet tunneling through an Eckart barrier, a one-dimensional bound-state Morse oscillator, and a two-dimensional (2D) model collinear reaction using an anharmonic potential energy surface. Approximate treatments of the quantum hydrodynamic equations will also be discussed which could allow scaling of the calculations to hundreds of degrees of freedom which is important for treating tunneling phenomena in condensed phase systems.
Hydrodynamic Forces on Microbubbles under Ultrasound Excitation
NASA Astrophysics Data System (ADS)
Clark, Alicia; Aliseda, Alberto
2014-11-01
Ultrasound (US) pressure waves exert a force on microbubbles that can be used to steer them in a flow. To control the motion of microbubbles under ultrasonic excitation, the coupling between the volume oscillations induced by the ultrasound pressure and the hydrodynamic forces needs to be well understood. We present experimental results for the motion of small, coated microbubbles, with similar sizes and physico-chemical properties as clinically-available ultrasound contrast agents (UCAs). The size distribution for the bubbles, resulting from the in-house manufacturing process, was characterized by analysis of high magnification microscopic images and determined to be bimodal. More than 99% of the volume is contained in microbubbles less than 10 microns in diameter, the size of a red blood cell. The motion of the microbubbles in a pulsatile flow, at different Reynolds and Womersley numbers, is studied from tracking of high-speed shadowgraphy. The influence of ultrasound forcing, at or near the resonant frequency of the bubbles, on the hydrodynamic forces due to the pulsatile flow is determined from the experimental measurements of the trajectories. Previous evidence of a sign reversal in Saffman lift is the focus of particular attention, as this is frequently the only hydrodynamic force acting in the direction perpendicular to the flow pathlines. Application of the understanding of this physical phenomenon to targeted drug delivery is analyzed in terms of the transport of the microbubbles. NSF GRFP.
Hydrodynamics of an Electrochemical Membrane Bioreactor
Wang, Ya-Zhou; Wang, Yun-Kun; He, Chuan-Shu; Yang, Hou-Yun; Sheng, Guo-Ping; Shen, Jin-You; Mu, Yang; Yu, Han-Qing
2015-01-01
An electrochemical membrane bioreactor (EMBR) has recently been developed for energy recovery and wastewater treatment. The hydrodynamics of the EMBR would significantly affect the mass transfers and reaction kinetics, exerting a pronounced effect on reactor performance. However, only scarce information is available to date. In this study, the hydrodynamic characteristics of the EMBR were investigated through various approaches. Tracer tests were adopted to generate residence time distribution curves at various hydraulic residence times, and three hydraulic models were developed to simulate the results of tracer studies. In addition, the detailed flow patterns of the EMBR were acquired from a computational fluid dynamics (CFD) simulation. Compared to the tank-in-series and axial dispersion ones, the Martin model could describe hydraulic performance of the EBMR better. CFD simulation results clearly indicated the existence of a preferential or circuitous flow in the EMBR. Moreover, the possible locations of dead zones in the EMBR were visualized through the CFD simulation. Based on these results, the relationship between the reactor performance and the hydrodynamics of EMBR was further elucidated relative to the current generation. The results of this study would benefit the design, operation and optimization of the EMBR for simultaneous energy recovery and wastewater treatment. PMID:25997399
Testing hydrodynamics schemes in galaxy disc simulations
NASA Astrophysics Data System (ADS)
Few, C. G.; Dobbs, C.; Pettitt, A.; Konstandin, L.
2016-08-01
We examine how three fundamentally different numerical hydrodynamics codes follow the evolution of an isothermal galactic disc with an external spiral potential. We compare an adaptive mesh refinement code (RAMSES), a smoothed particle hydrodynamics code (SPHNG), and a volume-discretized mesh-less code (GIZMO). Using standard refinement criteria, we find that RAMSES produces a disc that is less vertically concentrated and does not reach such high densities as the SPHNG or GIZMO runs. The gas surface density in the spiral arms increases at a lower rate for the RAMSES simulations compared to the other codes. There is also a greater degree of substructure in the SPHNG and GIZMO runs and secondary spiral arms are more pronounced. By resolving the Jeans length with a greater number of grid cells, we achieve more similar results to the Lagrangian codes used in this study. Other alterations to the refinement scheme (adding extra levels of refinement and refining based on local density gradients) are less successful in reducing the disparity between RAMSES and SPHNG/GIZMO. Although more similar, SPHNG displays different density distributions and vertical mass profiles to all modes of GIZMO (including the smoothed particle hydrodynamics version). This suggests differences also arise which are not intrinsic to the particular method but rather due to its implementation. The discrepancies between codes (in particular, the densities reached in the spiral arms) could potentially result in differences in the locations and time-scales for gravitational collapse, and therefore impact star formation activity in more complex galaxy disc simulations.
Hydrodynamics of an electrochemical membrane bioreactor.
Wang, Ya-Zhou; Wang, Yun-Kun; He, Chuan-Shu; Yang, Hou-Yun; Sheng, Guo-Ping; Shen, Jin-You; Mu, Yang; Yu, Han-Qing
2015-05-22
An electrochemical membrane bioreactor (EMBR) has recently been developed for energy recovery and wastewater treatment. The hydrodynamics of the EMBR would significantly affect the mass transfers and reaction kinetics, exerting a pronounced effect on reactor performance. However, only scarce information is available to date. In this study, the hydrodynamic characteristics of the EMBR were investigated through various approaches. Tracer tests were adopted to generate residence time distribution curves at various hydraulic residence times, and three hydraulic models were developed to simulate the results of tracer studies. In addition, the detailed flow patterns of the EMBR were acquired from a computational fluid dynamics (CFD) simulation. Compared to the tank-in-series and axial dispersion ones, the Martin model could describe hydraulic performance of the EBMR better. CFD simulation results clearly indicated the existence of a preferential or circuitous flow in the EMBR. Moreover, the possible locations of dead zones in the EMBR were visualized through the CFD simulation. Based on these results, the relationship between the reactor performance and the hydrodynamics of EMBR was further elucidated relative to the current generation. The results of this study would benefit the design, operation and optimization of the EMBR for simultaneous energy recovery and wastewater treatment.
Hydrodynamic slip length as a surface property
NASA Astrophysics Data System (ADS)
Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.
2016-02-01
Equilibrium and nonequilibrium molecular dynamics simulations were conducted in order to evaluate the hypothesis that the hydrodynamic slip length is a surface property. The system under investigation was water confined between two graphite layers to form nanochannels of different sizes (3-8 nm). The water-carbon interaction potential was calibrated by matching wettability experiments of graphitic-carbon surfaces free of airborne hydrocarbon contamination. Three equilibrium theories were used to calculate the hydrodynamic slip length. It was found that one of the recently reported equilibrium theories for the calculation of the slip length featured confinement effects, while the others resulted in calculations significantly hindered by the large margin of error observed between independent simulations. The hydrodynamic slip length was found to be channel-size independent using equilibrium calculations, i.e., suggesting a consistency with the definition of a surface property, for 5-nm channels and larger. The analysis of the individual trajectories of liquid particles revealed that the reason for observing confinement effects in 3-nm nanochannels is the high mobility of the bulk particles. Nonequilibrium calculations were not consistently affected by size but by noisiness in the smallest systems.
Astrophysically relevant hydrodynamics experiments using intense lasers
NASA Astrophysics Data System (ADS)
Remington, B. A.; Budil, K. S.; Estabrook, K.; Glendinning, S. G.; Gold, D.; Ryutov, D.; Kane, J.; Arnett, D.; Drake, R. P.; Smith, T.; Carroll, J.; McCray, R.; Liang, E.; Keilty, K.; Rubenchik, A.
1998-04-01
In a broad-based collaboration, we are developing a series of astrophysically relevant hydrodynamics experiments on the Nova and PetaWatt lasers at Lawrence Livermore National Laboratory. Issues that we are or planning to investigate are deep nonlinear hydrodynamic instabilities in 2D versus 3D, relevant to core-collapse supernova explosions [J. Kane et al., Ap. J. (1997); B.A. Remington et al., Phys. Plasmas (1997).]; strong-shock hydrodynamics relevant to supernova remnant formation [R.P. Drake et al., submitted, Ap. J. (1997).]; radiative blast wave development, of potential interest to gamma-ray burst models [E. Liang et al., 2nd Int. Workshop on LaboratoryAstrophysics using Intense Lasers, Mar. 19-21, 1998, Univ. of AZ.]; and cratering experiments, of possible interest to hypervelocity meteoroid impacts [A. Rubenchik et al., 2nd Int. Workshop on Laboratory Astrophysics using Intense Lasers, Mar. 19-21, 1998, Univ. of AZ.]. An overview of this work will be given, and the issue of scaling will be addressed [D. Ryutov et al., in preparation for submittal to Ap. J. (1998).].
Hydrodynamic fluctuations in thermostatted multiparticle collision dynamics.
Híjar, Humberto; Sutmann, Godehard
2011-04-01
In this work we study the behavior of mesoscopic fluctuations of a fluid simulated by Multiparticle Collision Dynamics when this is applied together with a local thermostatting procedure that constrains the strength of temperature fluctuations. We consider procedures in which the thermostat interacts with the fluid at every simulation step as well as cases in which the thermostat is applied only at regular time intervals. Due to the application of the thermostat temperature fluctuations are forced to relax to equilibrium faster than they do in the nonthermostatted, constant-energy case. Depending on the interval of application of the thermostat, it is demonstrated that the thermodynamic state changes gradually from isothermal to adiabatic conditions. In order to exhibit this effect we compute from simulations diverse correlation functions of the hydrodynamic fluctuating fields. These correlation functions are compared with those predicted by a linearized hydrodynamic theory of a simple fluid in which a thermostat is applied locally. We find a good agreement between the model and the numerical results, which confirms that hydrodynamic fluctuations in Multiparticle Collision Dynamics in the presence of the thermostat have the properties expected for spontaneous fluctuations in fluids in contact with a heat reservoir.
Modeling multiphase flow using fluctuating hydrodynamics.
Chaudhri, Anuj; Bell, John B; Garcia, Alejandro L; Donev, Aleksandar
2014-09-01
Fluctuating hydrodynamics provides a model for fluids at mesoscopic scales where thermal fluctuations can have a significant impact on the behavior of the system. Here we investigate a model for fluctuating hydrodynamics of a single-component, multiphase flow in the neighborhood of the critical point. The system is modeled using a compressible flow formulation with a van der Waals equation of state, incorporating a Korteweg stress term to treat interfacial tension. We present a numerical algorithm for modeling this system based on an extension of algorithms developed for fluctuating hydrodynamics for ideal fluids. The scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several nonequilibrium examples to illustrate the capability of the algorithm to model multiphase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches.
MUFASA: galaxy formation simulations with meshless hydrodynamics
NASA Astrophysics Data System (ADS)
Davé, Romeel; Thompson, Robert; Hopkins, Philip F.
2016-11-01
We present the MUFASA suite of cosmological hydrodynamic simulations, which employs the GIZMO meshless finite mass (MFM) code including H2-based star formation, nine-element chemical evolution, two-phase kinetic outflows following scalings from the Feedback in Realistic Environments zoom simulations, and evolving halo mass-based quenching. Our fiducial (50 h-1 Mpc)3 volume is evolved to z = 0 with a quarter billion elements. The predicted galaxy stellar mass functions (GSMFs) reproduces observations from z = 4 → 0 to ≲ 1.2σ in cosmic variance, providing an unprecedented match to this key diagnostic. The cosmic star formation history and stellar mass growth show general agreement with data, with a strong archaeological downsizing trend such that dwarf galaxies form the majority of their stars after z ˜ 1. We run 25 and 12.5 h-1 Mpc volumes to z = 2 with identical feedback prescriptions, the latter resolving all hydrogen-cooling haloes, and the three runs display fair resolution convergence. The specific star formation rates broadly agree with data at z = 0, but are underpredicted at z ˜ 2 by a factor of 3, re-emphasizing a longstanding puzzle in galaxy evolution models. We compare runs using MFM and two flavours of smoothed particle hydrodynamics, and show that the GSMF is sensitive to hydrodynamics methodology at the ˜×2 level, which is sub-dominant to choices for parametrizing feedback.
Caporaso, G J
2000-09-27
This presentation will be a broad survey of progress in induction technology over the past four years. Much work has been done on accelerators for hydrodynamic test radiography and other applications. Solid-state pulsers have been developed which can provide unprecedented flexibility and precision in pulse format and accelerating voltage for both ion and electron induction machines. Induction linacs can now be built which can operate with MHz repetition rates. Solid-state technology has also made possible the development of fast kickers for precision control of high current beams. New insulator technology has been developed which will improve conventional induction linacs in addition to enabling a new class of high gradient induction linacs.
Clark, D. S.; Robey, H. F.; Smalyuk, V. A.
2015-05-15
Encouraging progress is being made in demonstrating control of ablation front hydrodynamic instability growth in inertial confinement fusion implosion experiments on the National Ignition Facility [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, and R. Al-Ayat, Phys. Plasmas 16, 041006 (2009)]. Even once ablation front stabilities are controlled, however, instability during the stagnation phase of the implosion can still quench ignition. A scheme is proposed to reduce the growth of stagnation phase instabilities through the reverse of the “adiabat shaping” mechanism proposed to control ablation front growth. Two-dimensional radiation hydrodynamics simulations confirm that improved stagnation phase stability should be possible without compromising fuel compression.
Desroy, N; Retière, C
2000-06-01
Coupling effects of hydrodynamics and predatory activity of Nepthys hombergii (Savigny) (Polychaeta: Nephtyidae) on emigration of Hediste diversicolor (O.F. Müller) (Polychaeta: Nereidae) recruits were assessed in a flume. Experiments carried out in still water conditions and in the flume flow showed that predatory activity of N. hombergii is independent of the presence or the absence of flow and does not statistically influence the recruit emigration rate. It appears, however, that hydrodynamics is an inhibiting factor for the emigration of H. diversicolor which occurs in the absence of flow. The comparison of these results with literature data suggests that recruits could use hydrodynamics to leave an unsuitable habitat according to the species mobility range.
Towards modeling hydrodynamic stress limitations on transpiration
NASA Astrophysics Data System (ADS)
Matheny, A. M.; Bohrer, G.; Ivanov, V. Y.; Stoy, P. C.
2011-12-01
Evapotranspiration is one of the major forcing functions of Earth's climate, providing the link for the soil-plant-water continuum. Current models for transpiration assume a coupling between stomatal conductance and soil moisture through empirical relationships that do not resolve the hydrodynamic process of water movement from the soil to the leaves. This approach does not take advantage of recent advances in our understanding of water flow and storage in the trees, or of tree and canopy structure. It has been suggested that stomata respond to water potential in the leaf and branch, and that this hydrodynamic response is a mechanism for hydraulic limitation of stomatal conductance. Hydraulic limitations in forest ecosystems are common and are known to control transpiration when the soil is drying or when vapor pressure deficit (VPD) is very large. Hydraulic limitation can also impact stomatal apertures under conditions of adequate soil moisture and lower evaporative demand. Hydrodynamic stresses at the tree level act at several time scales, including the fast, minute-hour scale. These dynamics are faster than the time scales of hours to days at which drying soil will affect stomata conductance. The lack of representation of the tree-hydrodynamic process should therefore lead to atypical intra-daily patterns of error in results of current models. We use a large-scale comparison between observations and land-surface models to characterize the patterns of intra-daily error in simulated water flux. Through the use of the North American Carbon Program (NACP) dataset, more than 10 years of water flux data for 35 Fluxnet sites in the US and Canada have been analyzed. The diurnal error for each of the 24 models represented in this dataset allows the models to be categorized and evaluated on their ability to accurately predict the fast temporal dynamics of transpiration in different ecosystems and atmospheric forcing. Among well calibrated models, two general error
A hybrid Godunov method for radiation hydrodynamics
Sekora, Michael D.; Stone, James M.
2010-09-20
From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density E{sub r} and flux F{sub r} as well as a modified Godunov scheme for the material density {rho}, momentum density m, and energy density E. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati and Colella (2007) . Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.
Newtonian Hydrodynamics with Arbitrary Volumetric Sources
Lowrie, Robert Byron
2015-11-12
In this note, we derive how to handle mass, momentum, and energy sources for Newtonian hydrodynamics. Much of this is classic, although we’re unaware of a reference that treats mass sources, necessary for certain physics and the method of manufactured solutions. In addition, we felt it important to emphasize that the integral form of the governing equations results in a straightforward treatment of the sources. With the integral form, we’ll demonstrate that there’s no ambiguity between the Lagrangian and Eulerian form of the equations, which is less clear with the differential forms.
Hydrodynamic interaction between two helical swimmers
NASA Astrophysics Data System (ADS)
Ruiz Esparza, Alejandro; Godinez, Francisco; Lauga, Eric; Zenit, Roberto
2016-11-01
Many motile bacteria, such as E. coli, possess several helical flagellar filaments that bundle together to form a coherent helical element for propulsion. In order to understand the process of bundling, we study the interaction between two identical helical magnetic swimmers that self propel in a highly viscous Newtonian fluid due to the rotation of an external magnetic field. Our experiments reveal that hydrodynamic interactions lead to nontrivial collective and relative effects, both in translation and rotation. We will present our experimental results and discuss the physical mechanisms responsible for our observations.
Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics
Mendoza, M.; Herrmann, H. J.; Boghosian, B. M.; Succi, S.
2010-07-02
A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows.
2D Hydrodynamic Investigation of Olmsted Cofferdams
2013-07-01
USGS) used RMA-Z (Wagner 2004) to predict effects of the ITW phased construction and operation on mussel beds located downstream (RMA-Z 2004...Then in 2008, CHL used an Adaptive Hydraulics model (AdH) to further evaluate potential impacts on mussel beds. In 2012, LRL used a HEC-RAS model to...were created. This model extends from RM 974.5 to 962.6 allowing inclu- sion of downstream mussel beds. In the USGS study, hydrodynamics, sediment
Hydrodynamic Phase Locking in Mouse Node Cilia
NASA Astrophysics Data System (ADS)
Takamatsu, Atsuko; Shinohara, Kyosuke; Ishikawa, Takuji; Hamada, Hiroshi
2013-06-01
Rotational movement of mouse node cilia generates leftward fluid flow in the node cavity, playing an important role in left-right determination in the embryo. Although rotation of numerous cilia was believed necessary to trigger the determination, recent reports indicate the action of two cilia to be sufficient. We examine cooperative cilia movement via hydrodynamic interaction. Results show cilia to be cooperative, having phases locked in a certain relation; a system with a pair of nonidentical cilia can achieve phase-locked states more easily than one with a pair of identical cilia.
The frontal method in hydrodynamics simulations
Walters, R.A.
1980-01-01
The frontal solution method has proven to be an effective means of solving the matrix equations resulting from the application of the finite element method to a variety of problems. In this study, several versions of the frontal method were compared in efficiency for several hydrodynamics problems. Three basic modifications were shown to be of value: 1. Elimination of equations with boundary conditions beforehand, 2. Modification of the pivoting procedures to allow dynamic management of the equation size, and 3. Storage of the eliminated equations in a vector. These modifications are sufficiently general to be applied to other classes of problems. ?? 1980.
Hydrodynamics and Rheology of Active Liquid Crystals
NASA Astrophysics Data System (ADS)
Cui, Zhenlu
2012-02-01
Active liquid crystals such as swimming bacteria, active gels and assemblies of motors and filaments are active complex fluids. Such systems differ from their passive counterparts in that particles absorb energy and generate motion. They are interesting from a more fundamental perspective as their dynamic phenomenons are both physically fascinating and potentially of great biological significance. In this talk, I will present a continuum model for active liquid crystals and analyze the behavior of a suspension subjected to a weak Poiseuille flow. Hydrodynamics, stability and rheology will also be discussed.
Klein-Gordon Equation in Hydrodynamical Form
Wong, Cheuk-Yin
2010-01-01
We follow and modify the Feshbach-Villars formalism by separating the Klein-Gordon equation into two coupled time-dependent Schroedinger equations for the particle and antiparticle wave functions with positive probability densities. We find that the equation of motion for the probability densities is in the form of relativistic hydrodynamics where various forces have their physical and classical counterparts. An additional element is the presence of the quantum stress tensor that depends on the derivatives of the amplitude of the wave function.
Numerical calculations of protostellar hydrodynamic collapse
NASA Technical Reports Server (NTRS)
Bodenheimer, P.; Black, D. C.
1978-01-01
Although 1-D (spherically symmetric) experiments of protostar collapse are highly idealized, they are the only ones which have been carried to a stage where a 'stellar' object is formed. Experiments have shown that the parameters (e.g., radius and luminosity) of the visible stellar core are sensitive to the assumed initial conditions, particularly the initial density. One of the major findings of 2-D numerical experiments is the formation of rings. Three-dimensional hydrodynamical calculations indicate that a collapsing cloud will break up into two or more orbiting subcondensations with the possible subsequent development of a stellar multiple system.
Electrical Discharges in Water. A Hydrodynamic Description
1974-12-23
6ary of the liquid as a consequence of a chang-e in the nature of the ex- JrnorJnf- the proe.;sure of the gas insioe the cavity, correct f’or thc...Condit.ions of g•rk equilitrium In the dischargu channel. 63 Section 5. Compos*!-on of the gas in a discharge channel. 69 Section 6. Kinetic coefflcients of...the gas in the discha.rge channel. 77 Section 7. Temperature of the plasma In a channel. Energy balance equation. 88 Chapter 4. Hydrodynamic Problems
Postexplosion hydrodynamics of supernovae in red supergiants
NASA Technical Reports Server (NTRS)
Herant, Marc; Woosley, S. E.
1994-01-01
Shock propagation, mixing, and clumping are studied in the explosion of red supergiants as Type II supernovae using a two-dimensional smooth particle hydrodynamic (SPH) code. We show that extensive Rayleigh-Talor instabilities develop in the ejecta in the wake of the reverse shock wave. In all cases, the shell structure of the progenitor is obliterated to leave a clumpy, well-mixed supernova remnant. However, the occurrence of mass loss during the lifetime of the progenitor can significantly reduce the amount of mixing. These results are independent of the Type II supernova explosion mechanism.
Classes of Hydrodynamic and Magnetohydrodynamic Turbulent Decay
NASA Astrophysics Data System (ADS)
Brandenburg, Axel; Kahniashvili, Tina
2017-02-01
We perform numerical simulations of decaying hydrodynamic and magnetohydrodynamic turbulence. We classify our time-dependent solutions by their evolutionary tracks in parametric plots between instantaneous scaling exponents. We find distinct classes of solutions evolving along specific trajectories toward points on a line of self-similar solutions. These trajectories are determined by the underlying physics governing individual cases, while the infrared slope of the initial conditions plays only a limited role. In the helical case, even for a scale-invariant initial spectrum (inversely proportional to wave number k ), the solution evolves along the same trajectory as for a Batchelor spectrum (proportional to k4).
Anomalous transport in second order hydrodynamics
NASA Astrophysics Data System (ADS)
Megías, Eugenio; Valle, Manuel
2016-11-01
We study the non-dissipative transport effects appearing at second order in the hydrodynamic expansion for a non-interacting gas of chiral fermions by using the partition function formalism. We discuss some features of the corresponding constitutive relations, derive the explicit expressions for the conductivities and compare with existing results in the literature. Talk given by E. Megías at the 4th International Conference on New Frontiers in Physics (ICNFP 2015), 23-30 August 2015, Kolymbari, Crete, Greece.
Vertical hydrodynamic focusing in glass microchannels.
Lin, Tony A; Hosoi, A E; Ehrlich, Daniel J
2009-01-08
Vertical hydrodynamic focusing in microfluidic devices is investigated through simulation and through direct experimental verification using a confocal microscope and a novel form of stroboscopic imaging. Optimization for microfluidic cytometry of biological cells is examined. By combining multiple crossing junctions, it is possible to confine cells to a single analytic layer of interest. Subtractive flows are investigated as a means to move the analysis layer vertically in the channel and to correct the flatness of this layer. The simulation software (ADINA and Coventor) is shown to accurately capture the complex dependencies of the layer interfaces, which vary strongly with channel geometry and relative flow rates.
Rapidity Correlation Structures from Causal Hydrodynamics
NASA Astrophysics Data System (ADS)
Gavin, Sean; Moschelli, George; Zin, Christopher
2016-08-01
Viscous diffusion can broaden the rapidity dependence of two-particle transverse momentum fluctuations. Surprisingly, measurements at RHIC by the STAR collaboration demonstrate that this broadening is accompanied by the appearance of unanticipated structure in the rapidity distribution of these fluctuations in the most central collisions. Although a first order classical Navier-Stokes theory can roughly explain the rapidity broadening, it cannot explain the additional structure. We propose that the rapidity structure can be explained using the second order causal Israel-Stewart hydrodynamics with stochastic noise.
Impact modeling with Smooth Particle Hydrodynamics
Stellingwerf, R.F.; Wingate, C.A.
1993-07-01
Smooth Particle Hydrodynamics (SPH) can be used to model hypervelocity impact phenomena via the addition of a strength of materials treatment. SPH is the only technique that can model such problems efficiently due to the combination of 3-dimensional geometry, large translations of material, large deformations, and large void fractions for most problems of interest. This makes SPH an ideal candidate for modeling of asteroid impact, spacecraft shield modeling, and planetary accretion. In this paper we describe the derivation of the strength equations in SPH, show several basic code tests, and present several impact test cases with experimental comparisons.
Sensitivity analysis of hydrodynamic stability operators
NASA Technical Reports Server (NTRS)
Schmid, Peter J.; Henningson, Dan S.; Khorrami, Mehdi R.; Malik, Mujeeb R.
1992-01-01
The eigenvalue sensitivity for hydrodynamic stability operators is investigated. Classical matrix perturbation techniques as well as the concept of epsilon-pseudoeigenvalues are applied to show that parts of the spectrum are highly sensitive to small perturbations. Applications are drawn from incompressible plane Couette, trailing line vortex flow and compressible Blasius boundary layer flow. Parametric studies indicate a monotonically increasing effect of the Reynolds number on the sensitivity. The phenomenon of eigenvalue sensitivity is due to the non-normality of the operators and their discrete matrix analogs and may be associated with large transient growth of the corresponding initial value problem.
Dynamic coupling of three hydrodynamic models
NASA Astrophysics Data System (ADS)
Hartnack, J. N.; Philip, G. T.; Rungoe, M.; Smith, G.; Johann, G.; Larsen, O.; Gregersen, J.; Butts, M. B.
2008-12-01
The need for integrated modelling is evidently present within the field of flood management and flood forecasting. Engineers, modellers and managers are faced with flood problems which transcend the classical hydrodynamic fields of urban, river and coastal flooding. Historically the modeller has been faced with having to select one hydrodynamic model to cover all the aspects of the potentially complex dynamics occurring in a flooding situation. Such a single hydrodynamic model does not cover all dynamics of flood modelling equally well. Thus the ideal choice may in fact be a combination of models. Models combining two numerical/hydrodynamic models are becoming more standard, typically these models combine a 1D river model with a 2D overland flow model or alternatively a 1D sewer/collection system model with a 2D overland solver. In complex coastal/urban areas the flood dynamics may include rivers/streams, collection/storm water systems along with the overland flow. The dynamics within all three areas is of the same time scale and there is feedback in the system across the couplings. These two aspects dictate a fully dynamic three way coupling as opposed to running the models sequentially. It will be shown that the main challenges of the three way coupling are time step issues related to the difference in numerical schemes used in the three model components and numerical instabilities caused by the linking of the model components. MIKE FLOOD combines the models MIKE 11, MIKE 21 and MOUSE into one modelling framework which makes it possible to couple any combination of river, urban and overland flow fully dynamically. The MIKE FLOOD framework will be presented with an overview of the coupling possibilities. The flood modelling concept will be illustrated through real life cases in Australia and in Germany. The real life cases reflect dynamics and interactions across all three model components which are not possible to reproduce using a two-way coupling alone. The
Superradiance from hydrodynamic vortices: A numerical study
Federici, F.; Tosi, M. P.; Cherubini, C.; Succi, S.
2006-03-15
The scattering of sound-wave perturbations from vortex excitations in hydrodynamic systems with typical Bose-Einstein-condensate (BEC) parameters is investigated by numerical integration of the associated Klein-Gordon equation. The simulations indicate that at sufficiently high angular speeds, in the perturbative limit where back-reaction effects can be neglected, sound wave packets can extract a sizable fraction of the vortex energy through a mechanism of superradiant scattering. It is conjectured that this superradiant regime may be detectable in BEC experiments.
Hydrodynamic Methods for Monitoring Underground Nuclear Tests
1992-04-01
Stancdard For," 298 (Rey 2-89) 0’ v b" bV S .I%1%d zl9.’S 2 9S I. OBJECTIVES The overall objective of the project was to improve the analysis and...the pressure p, the specific volume V = l/p, step in the curve ak ut = 2 kms- I reflects a phase transformation that and the specific internal energy...hydrodynamic. The curve on the equation of state surface p = p( V ,i) that is rel- evant for determining the thermodynarmic state of rock subjected to shock
Hydrodynamic and Spectral Simulations of HMXB Winds
Mauche, C W; Liedahl, D A; Akiyama, S; Plewa, T
2007-03-30
We describe preliminary results of a global model of the radiatively-driven photoionized wind and accretion flow of the high-mass X-ray binary Vela X-1. The full model combines FLASH hydrodynamic calculations, XSTAR photoionization calculations, HULLAC atomic data, and Monte Carlo radiation transport. We present maps of the density, temperature, velocity, and ionization parameter from a FLASH two-dimensional time-dependent simulation of Vela X-1, as well as maps of the emissivity distributions of the X-ray emission lines.
Hydrodynamics Versus Intracellular Coupling in the Synchronization of Eukaryotic Flagella
NASA Astrophysics Data System (ADS)
Quaranta, Greta; Aubin-Tam, Marie-Eve; Tam, Daniel
2015-12-01
The influence of hydrodynamic forces on eukaryotic flagella synchronization is investigated by triggering phase locking between a controlled external flow and the flagella of C. reinhardtii. Hydrodynamic forces required for synchronization are over an order of magnitude larger than hydrodynamic forces experienced in physiological conditions. Our results suggest that synchronization is due instead to coupling through cell internal fibers connecting the flagella. This conclusion is confirmed by observations of the vfl3 mutant, with impaired mechanical connection between the flagella.
Hydrodynamics Versus Intracellular Coupling in the Synchronization of Eukaryotic Flagella.
Quaranta, Greta; Aubin-Tam, Marie-Eve; Tam, Daniel
2015-12-04
The influence of hydrodynamic forces on eukaryotic flagella synchronization is investigated by triggering phase locking between a controlled external flow and the flagella of C. reinhardtii. Hydrodynamic forces required for synchronization are over an order of magnitude larger than hydrodynamic forces experienced in physiological conditions. Our results suggest that synchronization is due instead to coupling through cell internal fibers connecting the flagella. This conclusion is confirmed by observations of the vfl3 mutant, with impaired mechanical connection between the flagella.
Consistent description of kinetics and hydrodynamics of dusty plasma
Markiv, B.; Tokarchuk, M.
2014-02-15
A consistent statistical description of kinetics and hydrodynamics of dusty plasma is proposed based on the Zubarev nonequilibrium statistical operator method. For the case of partial dynamics, the nonequilibrium statistical operator and the generalized transport equations for a consistent description of kinetics of dust particles and hydrodynamics of electrons, ions, and neutral atoms are obtained. In the approximation of weakly nonequilibrium process, a spectrum of collective excitations of dusty plasma is investigated in the hydrodynamic limit.
Voulgarakis, Nikolaos K; Shang, Barry Z; Chu, Jhih-Wei
2013-08-01
The development of a hybrid fluctuating hydrodynamics (FHD) and molecular dynamics (MD) simulation method that combines the molecular dynamics of moving particles with the fluctuating hydrodynamics of solvent fields on Eulerian grid cells is presented. This method allows resolution of solute-solvent interfaces and realization of excluded volumes of particles in the presence of hydrodynamic coupling. With these capabilities, we show that the ubiquitous forces mediated by the solvent, hydrophobicity and hydrodynamics, can be linked in a mesoscopic simulation. The strategies we devise to overcome the numerical issues of mixing variables in the Eulerian and Lagrangian coordinate systems, i.e., using a pair of auxiliary fluids to realize the excluded volumes of particles and assigning collocating gridding systems on solutes to interface with solvent fields, are also presented. Simulation results show that the hybrid FHD and MD method can reproduce the solvation free energies and scaling laws of particles dynamics for hydrophobes of different sizes. The collapse of two hydrophobic particles was also simulated to illustrate that the hybrid FHD and MD method has the potential to be generally applied to study nanoscale self-assembly and dynamics-structure-function relationships of biomolecules.
NASA Technical Reports Server (NTRS)
Sholes, G.
1975-01-01
The condition of the equipment retained from the Saturn V hydrodynamic support (HDS) is described along with the work necessary to supplement, modify, and refurbish it for the space shuttle mated vehicle ground vibration test (MVGVT). The design changes necessary to adapt the Saturn V HDS design for the space shuttle are described and the results of the inventory and inspection are given.
Mitamura, Yoshinori; Kido, Kazuyuki; Yano, Tetsuya; Sakota, Daisuke; Yambe, Tomoyuki; Sekine, Kazumitsu; OKamoto, Eiji
2007-03-01
To overcome the drive shaft seal and bearing problem in rotary blood pumps, a hydrodynamic bearing, a magnetic fluid seal, and a brushless direct current (DC) motor were employed in an axial flow pump. This enabled contact-free rotation of the impeller without material wear. The axial flow pump consisted of a brushless DC motor, an impeller, and a guide vane. The motor rotor was directly connected to the impeller by a motor shaft. A hydrodynamic bearing was installed on the motor shaft. The motor and the hydrodynamic bearing were housed in a cylindrical casing and were waterproofed by a magnetic fluid seal, a mechanically noncontact seal. Impeller shaft displacement was measured using a laser sensor. Axial and radial displacements of the shaft were only a few micrometers for motor speed up to 8500 rpm. The shaft did not make contact with the bearing housing. A flow of 5 L/min was obtained at 8000 rpm at a pressure difference of 100 mm Hg. In conclusion, the axial flow blood pump consisting of a hydrodynamic bearing, a magnetic fluid seal, and a brushless DC motor provided contact-free rotation of the impeller without material wear.
Hydrodynamics in a Degenerate, Strongly Attractive Fermi Gas
NASA Technical Reports Server (NTRS)
Thomas, John E.; Kinast, Joseph; Hemmer, Staci; Turlapov, Andrey; O'Hara, Ken; Gehm, Mike; Granade, Stephen
2004-01-01
In summary, we use all-optical methods with evaporative cooling near a Feshbach resonance to produce a strongly interacting degenerate Fermi gas. We observe hydrodynamic behavior in the expansion dynamics. At low temperatures, collisions may not explain the expansion dynamics. We observe hydrodynamics in the trapped gas. Our observations include collisionally-damped excitation spectra at high temperature which were not discussed above. In addition, we observe weakly damped breathing modes at low temperature. The observed temperature dependence of the damping time and hydrodynamic frequency are not consistent with collisional dynamics nor with collisionless mean field interactions. These observations constitute the first evidence for superfluid hydrodynamics in a Fermi gas.
Hydrodynamic interactions between two semiflexible inextensible filaments in Stokes flow.
Young, Y-N
2009-04-01
Hydrodynamic interactions between two semiflexible inextensible filaments are shown to have a significant impact on filament buckling and their subsequent motion in Stokesian fluids. In linear shear flow, hydrodynamic interactions lead to filament shear dispersion that depends on the filament aspect ratio and the initial filament separation. In linear extensional flow, hydrodynamic interactions lead to complex filament dynamics around the stagnation point. These results suggest that hydrodynamic interactions need to be taken into account to determine the self-diffusion of non-Brownian semiflexible filaments in a cellular flow [Y.-N. Young and M. J. Shelley, Phys. Rev. Lett. 99, 058303 (2007)].
Multithread Hydrodynamic Modeling of a Solar Flare
NASA Astrophysics Data System (ADS)
Warren, Harry P.
2006-01-01
Past hydrodynamic simulations have been able to reproduce the high temperatures and densities characteristic of solar flares. These simulations, however, have not been able to account for the slow decay of the observed flare emission or the absence of blueshifts in high spectral resolution line profiles. Recent work has suggested that modeling a flare as a sequence of independently heated threads instead of as a single loop may resolve the discrepancies between the simulations and observations. In this paper, we present a method for computing multithread, time-dependent hydrodynamic simulations of solar flares and apply it to observations of the Masuda flare of 1992 January 13. We show that it is possible to reproduce the temporal evolution of high temperature thermal flare plasma observed with the instruments on the GOES and Yohkoh satellites. The results from these simulations suggest that the heating timescale for a individual thread is on the order of 200 s. Significantly shorter heating timescales (20 s) lead to very high temperatures and are inconsistent with the emission observed by Yohkoh.
Hydrodynamic Synchronization of Light Driven Microrotors
NASA Astrophysics Data System (ADS)
Di Leonardo, R.; Búzás, A.; Kelemen, L.; Vizsnyiczai, G.; Oroszi, L.; Ormos, P.
2012-07-01
Hydrodynamic synchronization is a fundamental physical phenomenon by which self-sustained oscillators communicate through perturbations in the surrounding fluid and converge to a stable synchronized state. This is an important factor for the emergence of regular and coordinated patterns in the motions of cilia and flagella. When dealing with biological systems, however, it is always hard to disentangle internal signaling mechanisms from external purely physical couplings. We have used the combination of two-photon polymerization and holographic optical trapping to build a mesoscale model composed of chiral propellers rotated by radiation pressure. The two microrotors can be synchronized by hydrodynamic interactions alone although the relative torques have to be finely tuned. Dealing with a micron sized system we treat synchronization as a stochastic phenomenon and show that the phase lag between the two microrotors is distributed according to a stationary Fokker-Planck equation for an overdamped particle over a tilted periodic potential. Synchronized states correspond to minima in this potential whose locations are shown to depend critically on the detailed geometry of the propellers.
Flagellar synchronization through direct hydrodynamic interactions.
Brumley, Douglas R; Wan, Kirsty Y; Polin, Marco; Goldstein, Raymond E
2014-07-29
Flows generated by ensembles of flagella are crucial to development, motility and sensing, but the mechanisms behind this striking coordination remain unclear. We present novel experiments in which two micropipette-held somatic cells of Volvox carteri, with distinct intrinsic beating frequencies, are studied by high-speed imaging as a function of their separation and orientation. Analysis of time series shows that the interflagellar coupling, constrained by lack of connections between cells to be hydrodynamical, exhibits a spatial dependence consistent with theory. At close spacings it produces robust synchrony for thousands of beats, while at increasing separations synchrony is degraded by stochastic processes. Manipulation of the relative flagellar orientation reveals in-phase and antiphase states, consistent with dynamical theories. Flagellar tracking with exquisite precision reveals waveform changes that result from hydrodynamic coupling. This study proves unequivocally that flagella coupled solely through a fluid can achieve robust synchrony despite differences in their intrinsic properties.DOI: http://dx.doi.org/10.7554/eLife.02750.001.
Particle Mesh Hydrodynamics for Astrophysics Simulations
NASA Astrophysics Data System (ADS)
Chatelain, Philippe; Cottet, Georges-Henri; Koumoutsakos, Petros
We present a particle method for the simulation of three dimensional compressible hydrodynamics based on a hybrid Particle-Mesh discretization of the governing equations. The method is rooted on the regularization of particle locations as in remeshed Smoothed Particle Hydrodynamics (rSPH). The rSPH method was recently introduced to remedy problems associated with the distortion of computational elements in SPH, by periodically re-initializing the particle positions and by using high order interpolation kernels. In the PMH formulation, the particles solely handle the convective part of the compressible Euler equations. The particle quantities are then interpolated onto a mesh, where the pressure terms are computed. PMH, like SPH, is free of the convection CFL condition while at the same time it is more efficient as derivatives are computed on a mesh rather than particle-particle interactions. PMH does not detract from the adaptive character of SPH and allows for control of its accuracy. We present simulations of a benchmark astrophysics problem demonstrating the capabilities of this approach.
Statistical mechanics and hydrodynamics of bacterial suspensions.
Baskaran, Aparna; Marchetti, M Cristina
2009-09-15
Unicellular living organisms, such as bacteria and algae, propel themselves through a medium via cyclic strokes involving the motion of cilia and flagella. Dense populations of such "active particles" or "swimmers" exhibit a rich collective behavior at large scales. Starting with a minimal physical model of a stroke-averaged swimmer in a fluid, we derive a continuum description of a suspension of active organisms that incorporates fluid-mediated, long-range hydrodynamic interactions among the swimmers. Our work demonstrates that hydrodynamic interactions provide a simple, generic origin for several nonequilibrium phenomena predicted or observed in the literature. The continuum model derived here does not depend on the microscopic physical model of the individual swimmer. The details of the large-scale physics do, however, differ for "shakers" (particles that are active but not self-propelled, such as melanocytes) and "movers" (self-propelled particles), "pushers" (most bacteria) and "pullers" (algae like Chlamydomonas). Our work provides a classification of the large-scale behavior of all these systems.
On the hydrodynamics of fish schooling
NASA Astrophysics Data System (ADS)
Borazjani, Iman; Daghooghi, Mohsen
2013-11-01
A Considerable number of fish species swim in a coordinated manner within approximately constant and equal distance from each other, forming a pattern which is referred to as a fish school. It is believed that fish schooling results in more efficient swimming. However, no experimental evidence has conclusively shown the hydrodynamic effects of neighboring fish on swimming, probably due to the challenges involved in measuring the performance under controlled conditions in a school. We investigate possible hydrodynamical effects of fish schooling by constructing an infinite school of virtual swimmers based on a mackerel fish body and carangiform kinematics. We carry out our self-propelled simulation based on prescribed undulations of the fish body (assuming that all of the fish in the school move in exact same manner) and calculating motion of the center of mass. One of the most important geometrical factors of the fish schooling pattern seems to be the distance between two adjacent fish in the school. Therefore, we examined fish schools with different distances of two adjacent fish. This work was partly supported by the Center for Computational Research (CCR), University at Buffalo.
Supernova hydrodynamics experiments on the Nova laser
NASA Astrophysics Data System (ADS)
Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Rubenchik, A.; Drake, R. P.; Fryxell, B. A.; Muller, E.
1997-12-01
The critical roles of hydrodynamic instabilities in SN 1987A and in ICF are well known; 2D-3D differences are important in both areas. In a continuing project at Lawrence Livermore National Laboratory (LLNL), the Nova Laser is being used in scaled laboratory experiments of hydrodynamic mixing under supernova-relevant conditions. Numerical simulations of the experiments are being done, using LLNL hydro codes, and astrophysics codes used to model supernovae. Initial investigations with two-layer planar packages having 2D sinusoidal interface perturbations are described in Ap.J. 478, L75 (1997). Early-time simulations done with the LLNL 1D radiation transport code HYADES are mapped into the 2D LLNL code CALE and into the multi-D supernova code PROMETHEUS. Work is underway on experiments comparing interface instability growth produced by 2D sinusoidal versus 3D cross-hatch and axisymmetric cylindrical perturbations. Results of the simulations will be presented and compared with experiment. Implications for interpreting supernova observations and for supernova modelling will be discussed. * Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.
Hydrodynamics of Sperm Cells near Surfaces
Elgeti, Jens; Kaupp, U. Benjamin; Gompper, Gerhard
2010-01-01
Sperm are propelled by an actively beating tail, and display a wide variety of swimming patterns. When confined between two parallel walls, sperm swim either in circles or on curvilinear trajectories close to the walls. We employ mesoscale hydrodynamics simulations in combination with a mechanical sperm model to study the swimming behavior near walls. The simulations show that sperm become captured at the wall due to the hydrodynamic flow fields which are generated by the flagellar beat. The circular trajectories are determined by the chiral asymmetry of the sperm shape. For strong (weak) chirality, sperm swim in tight (wide) circles, with the beating plane of the flagellum oriented perpendicular (parallel) to the wall. For comparison, we also perform simulations based on a local anisotropic friction of the flagellum. In this resistive force approximation, surface adhesion and circular swimming patterns are obtained as well. However, the adhesion mechanism is now due to steric repulsion, and the orientation of the beating plane is different. Our model provides a theoretical framework that explains several distinct swimming behaviors of sperm near and far from a wall. Moreover, the model suggests a mechanism by which sperm navigate in a chemical gradient via a change of their shape. PMID:20712984
Detailed simulation of morphodynamics: 1. Hydrodynamic model
NASA Astrophysics Data System (ADS)
Nabi, M.; de Vriend, H. J.; Mosselman, E.; Sloff, C. J.; Shimizu, Y.
2012-12-01
We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The grid can be locally refined and adapted to the bed geometry, managing the Cartesian grid cells and faces using a hierarchical tree data approach. A ghost-cell immersed-boundary technique is applied to cells intersecting the bed topography. The governing equations have been discretized using a finite-volume method on a staggered grid, conserving second-order accuracy in time and space. The solution advances in time using the fractional step approach. Large-eddy simulation is used as turbulence closure. We validate the model against several experiments and other results from literature. Model results for Stokes flow around a cylinder in the vicinity of a moving wall agree well with Wannier's analytical solution. At higher Reynolds numbers, computed trailing bubble length, separation angle, and drag coefficient compare favorably with experimental and previous computational results. Results for the flow over two- and three-dimensional dunes agree well with published data, including a fair reproduction of recirculation zones, horse-shoe structures, and boiling effects. This shows that the model is suitable for being used as a hydrodynamic submodel in the high-resolution modeling of sediment transport and formation and evolution of subaqueous ripples and dunes.
Quasiparticle equation of state for anisotropic hydrodynamics
NASA Astrophysics Data System (ADS)
Alqahtani, Mubarak; Nopoush, Mohammad; Strickland, Michael
2015-11-01
We present a new method for imposing a realistic equation of state in anisotropic hydrodynamics. The method relies on the introduction of a single finite-temperature quasiparticle mass which is fit to lattice data. By taking moments of the Boltzmann equation, we obtain a set of coupled partial differential equations which can be used to describe the 3+1-dimensional (3+1d) spacetime evolution of an anisotropic relativistic system. We then specialize to the case of a 0+1d system undergoing boost-invariant Bjorken expansion and subject to the relaxation-time approximation collisional kernel. Using this setup, we compare results obtained using the new quasiparticle equation of state method with those obtained using the standard method for imposing the equation of state in anisotropic hydrodynamics. We demonstrate that the temperature evolution obtained using the two methods is nearly identical and that there are only small differences in the pressure anisotropy. However, we find that there are significant differences in the evolution of the bulk pressure correction.
Smoothed particle hydrodynamics with GRAPE-1A
NASA Technical Reports Server (NTRS)
Umemura, Masayuki; Fukushige, Toshiyuki; Makino, Junichiro; Ebisuzaki, Toshikazu; Sugimoto, Daiichiro; Turner, Edwin L.; Loeb, Abraham
1993-01-01
We describe the implementation of a smoothed particle hydrodynamics (SPH) scheme using GRAPE-1A, a special-purpose processor used for gravitational N-body simulations. The GRAPE-1A calculates the gravitational force exerted on a particle from all other particles in a system, while simultaneously making a list of the nearest neighbors of the particle. It is found that GRAPE-1A accelerates SPH calculations by direct summation by about two orders of magnitudes for a ten thousand-particle simulation. The effective speed is 80 Mflops, which is about 30 percent of the peak speed of GRAPE-1A. Also, in order to investigate the accuracy of GRAPE-SPH, some test simulations were executed. We found that the force and position errors are smaller than those due to representing a fluid by a finite number of particles. The total energy and momentum were conserved within 0.2-0.4 percent and 2-5 x 10 exp -5, respectively, in simulations with several thousand particles. We conclude that GRAPE-SPH is quite effective and sufficiently accurate for self-gravitating hydrodynamics.
Dissipation in ferrofluids: mesoscopic versus hydrodynamic theory.
Müller, H W; Engel, A
1999-12-01
Part of the field dependent dissipation in ferrofluids occurs due to the rotational motion of the ferromagnetic grains relative to the viscous flow of the carrier fluid. The classical theoretical description due to Shliomis (Zh. Eksp. Teor. Fiz. 61, 2411 (1971) [Sov. Phy JETP 34, 1291 (1972)]) uses a mesoscopic treatment of the particle motion to derive a relaxation equation for the nonequilibrium part of the magnetization. Complementary, the hydrodynamic approach of Liu [Phys. Rev. Lett. 70, 3580 (1993)] involves only macroscopic quantities and results in dissipative Maxwell equations for the magnetic fields in the ferrofluid. Different stress tensors and constitutive equations lead to deviating theoretical predictions in those situations, where the magnetic relaxation processes cannot be considered instantaneous on the hydrodynamic time scale. We quantify these differences for two situations of experimental relevance, namely, a resting fluid in an oscillating oblique field and the damping of parametrically excited surface waves. The possibilities of an experimental differentiation between the two theoretical approaches is discussed.
Low Mach number fluctuating hydrodynamics for electrolytes
NASA Astrophysics Data System (ADS)
Péraud, Jean-Philippe; Nonaka, Andy; Chaudhri, Anuj; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.
2016-11-01
We formulate and study computationally the low Mach number fluctuating hydrodynamic equations for electrolyte solutions. We are interested in studying transport in mixtures of charged species at the mesoscale, down to scales below the Debye length, where thermal fluctuations have a significant impact on the dynamics. Continuing our previous work on fluctuating hydrodynamics of multicomponent mixtures of incompressible isothermal miscible liquids [A. Donev et al., Phys. Fluids 27, 037103 (2015), 10.1063/1.4913571], we now include the effect of charged species using a quasielectrostatic approximation. Localized charges create an electric field, which in turn provides additional forcing in the mass and momentum equations. Our low Mach number formulation eliminates sound waves from the fully compressible formulation and leads to a more computationally efficient quasi-incompressible formulation. We demonstrate our ability to model saltwater (NaCl) solutions in both equilibrium and nonequilibrium settings. We show that our algorithm is second order in the deterministic setting and for length scales much greater than the Debye length gives results consistent with an electroneutral approximation. In the stochastic setting, our model captures the predicted dynamics of equilibrium and nonequilibrium fluctuations. We also identify and model an instability that appears when diffusive mixing occurs in the presence of an applied electric field.
Kinetic and hydrodynamic models of chemotactic aggregation
NASA Astrophysics Data System (ADS)
Chavanis, Pierre-Henri; Sire, Clément
2007-10-01
We derive general kinetic and hydrodynamic models of chemotactic aggregation that describe certain features of the morphogenesis of biological colonies (like bacteria, amoebae, endothelial cells or social insects). Starting from a stochastic model defined in terms of N coupled Langevin equations, we derive a nonlinear mean-field Fokker-Planck equation governing the evolution of the distribution function of the system in phase space. By taking the successive moments of this kinetic equation and using a local thermodynamic equilibrium condition, we derive a set of hydrodynamic equations involving a damping term. In the limit of small frictions, we obtain a hyperbolic model describing the formation of network patterns (filaments) and in the limit of strong frictions we obtain a parabolic model which is a generalization of the standard Keller-Segel model describing the formation of clusters (clumps). Our approach connects and generalizes several models introduced in the chemotactic literature. We discuss the analogy between bacterial colonies and self-gravitating systems and between the chemotactic collapse and the gravitational collapse (Jeans instability). We also show that the basic equations of chemotaxis are similar to nonlinear mean-field Fokker-Planck equations so that a notion of effective generalized thermodynamics can be developed.
Hydrodynamic theory of diffusion in two-temperature multicomponent plasmas
Ramshaw, J.D.; Chang, C.H.
1995-12-31
Detailed numerical simulations of multicomponent plasmas require tractable expressions for species diffusion fluxes, which must be consistent with the given plasma current density J{sub q} to preserve local charge neutrality. The common situation in which J{sub q} = 0 is referred to as ambipolar diffusion. The use of formal kinetic theory in this context leads to results of formidable complexity. We derive simple tractable approximations for the diffusion fluxes in two-temperature multicomponent plasmas by means of a generalization of the hydrodynamical approach used by Maxwell, Stefan, Furry, and Williams. The resulting diffusion fluxes obey generalized Stefan-Maxwell equations that contain driving forces corresponding to ordinary, forced, pressure, and thermal diffusion. The ordinary diffusion fluxes are driven by gradients in pressure fractions rather than mole fractions. Simplifications due to the small electron mass are systematically exploited and lead to a general expression for the ambipolar electric field in the limit of infinite electrical conductivity. We present a self-consistent effective binary diffusion approximation for the diffusion fluxes. This approximation is well suited to numerical implementation and is currently in use in our LAVA computer code for simulating multicomponent thermal plasmas. Applications to date include a successful simulation of demixing effects in an argon-helium plasma jet, for which selected computational results are presented. Generalizations of the diffusion theory to finite electrical conductivity and nonzero magnetic field are currently in progress.
Fish biorobotics: kinematics and hydrodynamics of self-propulsion.
Lauder, George V; Anderson, Erik J; Tangorra, James; Madden, Peter G A
2007-08-01
As a result of years of research on the comparative biomechanics and physiology of moving through water, biologists and engineers have made considerable progress in understanding how animals moving underwater use their muscles to power movement, in describing body and appendage motion during propulsion, and in conducting experimental and computational analyses of fluid movement and attendant forces. But it is clear that substantial future progress in understanding aquatic propulsion will require new lines of attack. Recent years have seen the advent of one such new avenue that promises to greatly broaden the scope of intellectual opportunity available to researchers: the use of biorobotic models. In this paper we discuss, using aquatic propulsion in fishes as our focal example, how using robotic models can lead to new insights in the study of aquatic propulsion. We use two examples: (1) pectoral fin function, and (2) hydrodynamic interactions between dorsal and caudal fins. Pectoral fin function is characterized by considerable deformation of individual fin rays, as well as spanwise (along the length) and chordwise (across the fin) deformation and area change. The pectoral fin can generate thrust on both the outstroke and instroke. A robotic model of the pectoral fin replicates this result, and demonstrates the effect of altering stroke kinematics on the pattern of force production. The soft dorsal fin of fishes sheds a distinct vortex wake that dramatically alters incoming flow to the tail: the dorsal fin and caudal fin act as dual flapping foils in series. This design can be replicated with a dual-foil flapping robotic device that demonstrates this phenomenon and allows examination of regions of the flapping performance space not available to fishes. We show how the robotic flapping foil device can also be used to better understand the significance of flexible propulsive surfaces for locomotor performance. Finally we emphasize the utility of self
Measurement of biofilm growth and local hydrodynamics using optical coherence tomography
Weiss, Nicolás; Obied, Khalid El Tayeb El; Kalkman, Jeroen; Lammertink, Rob G.H.; van Leeuwen, Ton G.
2016-01-01
We report on localized and simultaneous measurement of biofilm growth and local hydrodynamics in a microfluidic channel using optical coherence tomography. We measure independently with high spatio-temporal resolution the longitudinal flow velocity component parallel to the imaging beam and the transverse flow velocity component perpendicular to the imaging beam. Based on the measured velocities we calculate the shear-rates in the flow channel. We show the relation between the measured biofilm structure and flow velocities as biofilm growth progresses over the course of 48 hours. PMID:27699116
Spatial patterns in coastal lagoons related to the hydrodynamics of seawater intrusion.
Fiandrino, Annie; Ouisse, Vincent; Dumas, Franck; Lagarde, Franck; Pete, Romain; Malet, Nathalie; Le Noc, Sandrine; de Wit, Rutger
2017-03-24
Marine intrusion was simulated in a choked and in a restricted coastal lagoon by using a 3D-hydrodynamic model. To study the spatiotemporal progression of seawater intrusion and its mixing efficiency with lagoon waters we define Marine Mixed Volume (VMM) as a new hydrodynamic indicator. Spatial patterns in both lagoons were described by studying the time series and maps of VMM taking into account the meteorological conditions encountered during a water year. The patterns comprised well-mixed zones (WMZ) and physical barrier zones (PBZ) that act as hydrodynamic boundaries. The choked Bages-Sigean lagoon comprises four sub-basins: a PBZ at the inlet, and two WMZ's separated by another PBZ corresponding to a constriction zone. The volumes of the PBZ were 2.1 and 5.4 millions m(3) with characteristic mixing timescale of 68 and 84days, respectively. The WMZ were 12.3 and 43.3 millions m(3) with characteristics mixing timescale of 70 and 39days, respectively.
NASA Astrophysics Data System (ADS)
Prabhakar, Ranganathan; Sasmal, Chandi; Nguyen, Duc At; Sridhar, Tam; Prakash, J. Ravi
2017-01-01
Extensional rheometry and Brownian dynamics simulations of flexible polymer solutions confirm predictions based on blob concepts that coil-stretch hysteresis in extensional flows increases with concentration, reaching a maximum at the critical overlap concentration c* before progressively vanishing in the semidilute regime. These observations demonstrate that chain stretching strengthens intermolecular hydrodynamic screening in dilute solutions, but weakens it in semidilute solutions. Flow can thus strongly modify the concentration dependence of viscoelastic properties of polymer solutions.
Hydrodynamic Scalings: from Astrophysics to Laboratory
NASA Astrophysics Data System (ADS)
Ryutov, D. D.; Remington, B. A.
2000-05-01
A surprisingly general hydrodynamic similarity has been recently described in Refs. [1,2]. One can call it the Euler similarity because it works for the Euler equations (with MHD effects included). Although the dissipation processes are assumed to be negligible, the presence of shocks is allowed. For the polytropic medium (i.e., the medium where the energy density is proportional to the pressure), an evolution of an arbitrarily chosen 3D initial state can be scaled to another system, if a single dimensionless parameter (the Euler number) is the same for both initial states. The Euler similarity allows one to properly design laboratory experiments modeling astrophysical phenomena. We discuss several examples of such experiments related to the physics of supernovae [3]. For the problems with a single spatial scale, the condition of the smallness of dissipative processes can be adequately described in terms of the Reynolds, Peclet, and magnetic Reynolds numbers related to this scale (all three numbers must be large). However, if the system develops small-scale turbulence, dissipation may become important at these smaller scales, thereby affecting the gross behavior of the system. We analyze the corresponding constraints. We discuss also constraints imposed by the presence of interfaces between the substances with different polytropic index. Another set of similarities governs evolution of photoevaporation fronts in astrophysics. Convenient scaling laws exist in situations where the density of the ablated material is very low compared to the bulk density. We conclude that a number of hydrodynamical problems related to such objects as the Eagle Nebula can be adequately simulated in the laboratory. We discuss also possible scalings for radiative astrophysical jets (see Ref. [3] and references therein). This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48
RECENT ADVANCES IN MACROMOLECULAR HYDRODYNAMIC MODELING
Aragon, Sergio R.
2010-01-01
The modern implementation of the boundary element method (S.R. Aragon, J. Comput. Chem. 25(2004)1191–12055) has ushered unprecedented accuracy and precision for the solution of the Stokes equations of hydrodynamics with stick boundary conditions. This article begins by reviewing computations with the program BEST of smooth surface objects such as ellipsoids, the dumbbell, and cylinders that demonstrate that the numerical solution of the integral equation formulation of hydrodynamics yields very high precision and accuracy. When BEST is used for macromolecular computations, the limiting factor becomes the definition of the molecular hydrodynamic surface and the implied effective solvation of the molecular surface. Studies on 49 different proteins, ranging in molecular weight from 9 to over 400 kDa, have shown that a model using a 1.1 A thick hydration layer describes all protein transport properties very well for the overwhelming majority of them. In addition, this data implies that the crystal structure is an excellent representation of the average solution structure for most of them. In order to investigate the origin of a handful of significant discrepancies in some multimeric proteins (over −20% observed in the intrinsic viscosity), the technique of Molecular Dynamics simulation (MD) has been incorporated into the research program. A preliminary study of dimeric α-chymotrypsin using approximate implicit water MD is presented. In addition I describe the successful validation of modern protein force fields, ff03 and ff99SB, for the accurate computation of solution structure in explicit water simulation by comparison of trajectory ensemble average computed transport properties with experimental measurements. This work includes small proteins such as lysozyme, ribonuclease and ubiquitin using trajectories around 10 ns duration. We have also studied a 150 kDa flexible monoclonal IgG antibody, trastuzumab, with multiple independent trajectories encompassing over
Hydrodynamics of a Multistage Wet Scrubber Incineration Conditions
ERIC Educational Resources Information Center
Said, M. M.; Manyele, S. V.; Raphael, M. L.
2012-01-01
The objective of the study was to determine the hydrodynamics of the two stage counter-current cascade wet scrubbers used during incineration of medical waste. The dependence of the hydrodynamics on two main variables was studied: Inlet air flow rate and inlet liquid flow rate. This study introduces a new wet scrubber operating features, which are…
Hydrodynamic Models for Multicomponent Plasmas with Collisional-Radiative Kinetics
2014-12-01
is lovingly dedicated to my mother, Mai Hoang, for everything she has given to me and her unconditional love. v Table of Contents 1 Introduction ...15 2 Hydrodynamic Equations . . . . . . . . . . . . . . . . . . . . . . . 17 2.1 Introduction ...reactive hydrodynamics . . . . 29 3 Numerical Formulation . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.1 Introduction
Elasto-hydrodynamic network analysis of colloidal gels
NASA Astrophysics Data System (ADS)
Swan, James; Varga, Zsigmond
Colloidal gels formed at low particle volume fractions result from a competition between two rate processes: aggregation of colloids and compaction of pre-gel aggregates. Recent work has shown that the former process is highly sensitive to the nature of the hydrodynamic interactions between suspended colloids. This same sensitivity to hydrodynamic flows within the gel leads to pronounced differences in the spectrum of relaxation times and response to deformation of the gel. This talk explores those differences and their consequences through computational simulations and the framework of elasto-hydrodynamic network analysis. We demonstrate a significant impact of hydrodynamic interactions between gelled colloids on macroscopic gel dynamics and rheology as well as the effect of hydrodynamic screening in gelled materials.
A Modeling Study of Hydrodynamic Circulation in a Fjord of the Pacific Northwest
Wang, Taiping; Yang, Zhaoqing
2012-10-01
Increased eutrophication and degraded water quality in estuarine and coastal waters have been a worldwide environmental concern. While it is commonly accepted that anthropogenic impact plays a major role in many emerging water quality issues, natural conditions such as restricted water circulations controlled by geometry may also substantially contribute to unfavorable water quality in certain ecosystems. To elucidate the contributions from different factors, a hydrodynamic-water quality model that integrates both physical transport and pollutant loadings is particularly warranted. A preliminary modeling study using the Environmental Fluid Dynamic Code (EFDC) is conducted to investigate hydrodynamic circulation and low dissolved oxygen (DO) in Hood Canal, a representative fjord in the U.S. Pacific Northwest. Because the water quality modeling work is still ongoing, this paper focuses on the progress in hydrodynamic modeling component. The hydrodynamic model has been set up using the publicly available forcing data and was calibrated against field observations or NOAA predictions for tidal elevation, current, salinity and temperature. The calibrated model was also used to estimate physical transport timescales such as residence time in the estuary. The preliminary model results demonstrate that the EFDC Hood Canal model is capable of capturing the general circulation patterns in Hood Canal, including weak tidal current and strong vertical stratification. The long residence time (i.e., on the order of 100 days for the entire estuary) also indicates that restricted water circulation could contribute to low DO in the estuary and also makes the system especially susceptible to anthropogenic disturbance, such as excess nutrient input.
Deformation of DNA molecules by hydrodynamic focusing
NASA Astrophysics Data System (ADS)
Wong, Pak Kin; Lee, Yi-Kuen; Ho, Chih-Ming
2003-12-01
The motion of a DNA molecule in a solvent flow reflects the deformation of a nano/microscale flexible mass spring structure by the forces exerted by the fluid molecules. The dynamics of individual molecules can reveal both fundamental properties of the DNA and basic understanding of the complex rheological properties of long-chain molecules. In this study, we report the dynamics of isolated DNA molecules under homogeneous extensional flow. Hydrodynamic focusing generates homogeneous extensional flow with uniform velocity in the transverse direction. The deformation of individual DNA molecules in the flow was visualized with video fluorescence microscopy. A coil stretch transition was observed when the Deborah number (De) is larger than 0.8. With a sudden stopping of the flow, the DNA molecule relaxes and recoils. The longest relaxation time of T2 DNA was determined to be 0.63 s when scaling viscosity to 0.9 cP.
A new hydrodynamic analysis of double layers
NASA Technical Reports Server (NTRS)
Hora, Heinrich
1987-01-01
A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic (not necessarily static) electric fields and double layers inside of plasmas including oscillations and damping. For the first time a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitous and inverted double layers in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. Results are the rotation of plasmas in magnetic fields and a new second harmonic resonance, explanation of the measured inverted double layers, explanation of the observed density-independent, second harmonics emission from laser-produced plasmas, and a laser acceleration scheme by the very high fields of the double layers.
Computational brittle fracture using smooth particle hydrodynamics
Mandell, D.A.; Wingate, C.A.; Schwalbe, L.A.
1996-10-01
We are developing statistically based, brittle-fracture models and are implementing them into hydrocodes that can be used for designing systems with components of ceramics, glass, and/or other brittle materials. Because of the advantages it has simulating fracture, we are working primarily with the smooth particle hydrodynamics code SPBM. We describe a new brittle fracture model that we have implemented into SPBM. To illustrate the code`s current capability, we have simulated a number of experiments. We discuss three of these simulations in this paper. The first experiment consists of a brittle steel sphere impacting a plate. The experimental sphere fragment patterns are compared to the calculations. The second experiment is a steel flyer plate in which the recovered steel target crack patterns are compared to the calculated crack patterns. We also briefly describe a simulation of a tungsten rod impacting a heavily confined alumina target, which has been recently reported on in detail.
Hydrodynamics of primordial black hole formation
NASA Technical Reports Server (NTRS)
Nadezhin, D. K.; Novikov, I. D.; Polnarev, A. G.
1979-01-01
The hydrodynamic picture of the formation of primordial black holes (PBH) at the early stages of expansion of the Universe is considered. It is assumed that close to singularity, expansion occurs in a quasi-isotropic way. Using an EVM, a spherically symmetrical nonlinear problem of the evolution of primary strong deviation from the Fridman solution was solved. What these deviations must be, so that the formation of PBH occurred was clarified. Attention was devoted to the role of pressure gradients. It is pointed out that at the moment of formation of PBH, only a small part of matter enters into it, primarily the component of perturbation. It is also pointed out that at this moment, the mass of PBH essentially is smaller than the mass considered within the cosmic horizon. The possibility of changing the mass of the PBH as a result of accretion is analyzed.
Cosmological Hydrodynamics on a Moving Mesh
NASA Astrophysics Data System (ADS)
Hernquist, Lars
We propose to construct a model for the visible Universe using cosmological simulations of structure formation. Our simulations will include both dark matter and baryons, and will employ two entirely different schemes for evolving the gas: smoothed particle hydrodynamics (SPH) and a moving mesh approach as incorporated in the new code, AREPO. By performing simulations that are otherwise nearly identical, except for the hydrodynamics solver, we will isolate and understand differences in the properties of galaxies, galaxy groups and clusters, and the intergalactic medium caused by the computational approach that have plagued efforts to understand galaxy formation for nearly two decades. By performing simulations at different levels of resolution and with increasingly complex treatments of the gas physics, we will identify the results that are converged numerically and that are robust with respect to variations in unresolved physical processes, especially those related to star formation, black hole growth, and related feedback effects. In this manner, we aim to undertake a research program that will redefine the state of the art in cosmological hydrodynamics and galaxy formation. In particular, we will focus our scientific efforts on understanding: 1) the formation of galactic disks in a cosmological context; 2) the physical state of diffuse gas in galaxy clusters and groups so that they can be used as high-precision probes of cosmology; 3) the nature of gas inflows into galaxy halos and the subsequent accretion of gas by forming disks; 4) the co-evolution of galaxies and galaxy clusters with their central supermassive black holes and the implications of related feedback for galaxy evolution and the dichotomy between blue and red galaxies; 5) the physical state of the intergalactic medium (IGM) and the evolution of the metallicity of the IGM; and 6) the reaction of dark matter around galaxies to galaxy formation. Our proposed work will be of immediate significance for
Separation of blood cells using hydrodynamic lift
NASA Astrophysics Data System (ADS)
Geislinger, T. M.; Eggart, B.; Braunmüller, S.; Schmid, L.; Franke, T.
2012-04-01
Using size and deformability as intrinsic biomarkers, we separate red blood cells (RBCs) from other blood components based on a repulsive hydrodynamic cell-wall-interaction. We exploit this purely viscous lift effect at low Reynolds numbers to induce a lateral migration of soft objects perpendicular to the streamlines of the fluid, which closely follows theoretical prediction by Olla [J. Phys. II 7, 1533, (1997)]. We study the effects of flow rate and fluid viscosity on the separation efficiency and demonstrate the separation of RBCs, blood platelets, and solid microspheres from each other. The method can be used for continuous and label-free cell classification and sorting in on-chip blood analysis.
Off-shell hydrodynamics from holography
Crossley, Michael; Glorioso, Paolo; Liu, Hong; ...
2016-02-18
In this article, we outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual. As a first step, in this paper we restrict to systems with a non-dissipative horizon. By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces. At zeroth order, this action reduces tomore » that proposed by Dubovsky et al. as an off-shell formulation of ideal fluid dynamics.« less
Thermal waves in an extended hydrodynamic approach
NASA Astrophysics Data System (ADS)
Vasconcellos, Áurea R.; Luzzi, Roberto; Jou, David; Casas-Vazquez, José
1994-12-01
A study of the question of heat propagation in an extended quantum hydrodynamic approach is presented. We consider a fluid of Fermi particles in interaction with a thermal bath of bosons. The equation of evolution for the flux of energy, which is incorporated as a basic thermodynamic variable thus extending the space of variables of linear thermodynamics, is derived via the nonequilibrium statistical operator method. We obtain an equation of propagation of thermal waves with damping. This hyperbolic equation, which replaces Fourier's heat law removing associated inconsistencies, depends on several thermodynamic forces that include the space variation of the flux itself. The equation allows for the propagation of damped thermal excitations that are of the type of a second sound. The dispersion relation is derived with the transport coefficients given at a microscopic (mechano-statistical)level. The limiting conditions that allow to go from the damped-wave regime of propagation to the diffusive regime are discussed.
Generalized hydrodynamic correlations and fractional memory functions
NASA Astrophysics Data System (ADS)
Rodríguez, Rosalio F.; Fujioka, Jorge
2015-12-01
A fractional generalized hydrodynamic (GH) model of the longitudinal velocity fluctuations correlation, and its associated memory function, for a complex fluid is analyzed. The adiabatic elimination of fast variables introduces memory effects in the transport equations, and the dynamic of the fluctuations is described by a generalized Langevin equation with long-range noise correlations. These features motivate the introduction of Caputo time fractional derivatives and allows us to calculate analytic expressions for the fractional longitudinal velocity correlation function and its associated memory function. Our analysis eliminates a spurious constant term in the non-fractional memory function found in the non-fractional description. It also produces a significantly slower power-law decay of the memory function in the GH regime that reduces to the well-known exponential decay in the non-fractional Navier-Stokes limit.
Preliminary study of disc hydrodynamic polishing.
Li, Yan; Lin, Bin; Zhang, XiaoFeng; Liu, PengFei
2016-10-01
In this paper, a developed polishing method based on elastic emission machining and Jules Verne-a variation on fluid jet polishing-is presented. This method is named disc hydrodynamic polishing (DHDP). A computational fluid dynamics (CFD)-based model that consists of a CFD model and an erosion model is introduced to predict the surface roughness obtained by DHDP. The performance of DHDP is studied by experiments. The slurry used in the experiments comprises 95% deionized water and 5% cerium oxide particles. Fused-silica glass is chosen as the workpiece. After the experiments, an ultrasmooth surface without cracks is obtained. The simulation results principally coincide with the experimental results. The experimental results show that the actual roughness is slightly less than the prediction and smaller particles are more favorable for obtaining a better surface roughness.
Hydrodynamics and control of microbial locomotion
NASA Astrophysics Data System (ADS)
Dunkel, Jorn; Kantsler, Vasily; Polin, Marco; Wioland, Hugo; Goldstein, Raymond
2014-03-01
Interactions between swimming cells, surfaces and fluid flow are essential to many microbiological processes, from the formation of biofilms to the fertilization of human egg cells. Yet, relatively little remains known quantitatively about the physical mechanisms that govern the response of bacteria, algae and sperm cells to flow velocity gradients and solid surfaces. A better understanding of cell-surface and cell-flow interactions promises new biological insights and may advance microfluidic techniques for controlling microbial and sperm locomotion, with potential applications in diagnostics and therapeutic protein synthesis. Here, we report new experimental measurements that quantify surface interactions of bacteria, unicellular green algae and mammalian spermatozoa. These experiments show that the subtle interplay of hydrodynamics and surface interactions can stabilize collective bacterial motion, that direct ciliary contact interactions dominate surface scattering of eukaryotic biflagellate algae, and that rheotaxis combined with steric surface interactions provides a robust long-range navigation mechanism for sperm cells.
Hydrodynamic models for slurry bubble column reactors
Gidaspow, D.
1995-12-31
The objective of this investigation is to convert a {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. This model is capable of predicting local gas, liquid and solids hold-ups and the basic flow regimes: the uniform bubbling, the industrially practical churn-turbulent (bubble coalescence) and the slugging regimes. Current reactor models incorrectly assume that the gas and the particle hold-ups (volume fractions) are uniform in the reactor. They must be given in terms of empirical correlations determined under conditions that radically differ from reactor operation. In the proposed hydrodynamic approach these hold-ups are computed from separate phase momentum balances. Furthermore, the kinetic theory approach computes the high slurry viscosities from collisions of the catalyst particles. Thus particle rheology is not an input into the model.
Hydrodynamic optical alignment for microflow cytometry.
Kennedy, Matthew J; Stelick, Scott J; Sayam, Lavanya G; Yen, Andrew; Erickson, David; Batt, Carl A
2011-03-21
A microfabricated flow cytometer has been developed that is capable of detecting nearly all of the microparticles in an aqueous suspension. Current design allows for integrated coupling between an optical fiber-based detection system and the particle stream via hydrodynamic focusing. By adjusting the relative flow-rates at the auxiliary inputs of the focusing manifold, the particle stream can be steered out-of-plane relative to the illuminating laser, and similarly the particle stream can be squeezed or expanded. The microfabricated device was constructed in polydimethylsiloxane with cross-sectional microfluidic dimensions of 125 µm×125 µm. Using the present device and method, fluorescent microparticles in aqueous solution were counted at an absolute counting efficiency of 91±4%. The coefficient of variation of the fluorescence pulse-heights for far-red fluorescent microparticles was 15%. The device exhibited a linear response to fluorescence intensity calibration microparticles as shown by comparison with a commercial cytometer instrument.
Study of hydrodynamic characteristics in tubular photobioreactors.
Zhang, Qinghua; Wu, Xia; Xue, Shengzhang; Liang, Kehong; Cong, Wei
2013-02-01
In this work, the hydrodynamic characteristics in tubular photobioreactors with a series of helical static mixers built-in were numerically investigated using computational fluid dynamics (CFD). The influences of height and screw pitch of the helical static mixer and fluid inlet velocity on the cell trajectories, swirl numbers and energy consumption were examined. In order to verify the actual results for cultivation of microalgae, cultivation experiments of freshwater Chlorella sp. were carried out in photobioreactor with and without helical static mixer built-in at the same time. It was shown that with built-in helical static mixer, the mixing of fluid could be intensified, and the light/dark cycle could also be achieved which is of benefit for the growth of microalgae. The biomass productivity of Chlorella sp. in tubular photobioreactor with helical static mixer built-in was 37.26 % higher than that in the photobioreactor without helical static mixer.
Hydrodynamical simulations of detonations in superbursts
NASA Astrophysics Data System (ADS)
Noël, Claire; Busegnies, Yves; Papalexandris, Miltiadis V.; Goriely, Stephane
2008-07-01
A new hydrodynamical algorithm to study astrophysical detonations is presented. A prime motivation of this development is the description of a carbon detonation in conditions relevant to superbursts, which are thought to result from the propagation of a detonation front around the surface of a neutron star in the carbon layer underlying the atmosphere. The algorithm we have developed is a finite-volume method inspired by the original MUSCL scheme of van Leer (1979). The one-dimensional calculations we have performed demonstrate that the carbon detonation at the surface of a neutron star is a multiscale phenomenon. The length scale of liberation of energy is 106 times smaller than the total reaction length. We show that a multi-resolution approach can be used to solve all the reaction lengths. For mixed H/He accreting systems, we have introduced a new reduced network to study the impact of the photodisintegration of the heavy elements on the detonation.
Ratchets in hydrodynamic flow: more than waterwheels
Sturm, James C.; Cox, Edward C.; Comella, Brandon; Austin, Robert H.
2014-01-01
The transport of objects in microfluidic arrays of obstacles is a surprisingly rich area of physics and statistical mechanics. Tom Duke's mastery of these areas had a major impact in the development of biotechnology which uses these ideas at an increasing scale. We first review how biological objects are transported in fluids at low Reynolds numbers, including a discussion of electrophoresis, then concentrate on the separation of objects in asymmetric arrays, sometimes called Brownian ratchets when diffusional symmetry is broken by the structures. We move beyond this to what are called deterministic arrays where non-hydrodynamic forces in asymmetric arrays allow for extraordinary separation, and we look to the future of using these unusual arrays at the nanoscale and at the hundreds of micrometre scale. The emphasis is on how the original ideas of Tom Duke drove this work forward. PMID:25485086
Tears of Venom: Hydrodynamics of Reptilian Envenomation
NASA Astrophysics Data System (ADS)
Young, Bruce A.; Herzog, Florian; Friedel, Paul; Rammensee, Sebastian; Bausch, Andreas; van Hemmen, J. Leo
2011-05-01
In the majority of venomous snakes, and in many other reptiles, venom is conveyed from the animal’s gland to the prey’s tissue through an open groove on the surface of the teeth and not through a tubular fang. Here we focus on two key aspects of the grooved delivery system: the hydrodynamics of venom as it interacts with the groove geometry, and the efficiency of the tooth-groove-venom complex as the tooth penetrates the prey’s tissue. We show that the surface tension of the venom is the driving force underlying the envenomation dynamics. In so doing, we explain not only the efficacy of the open groove, but also the prevalence of this mechanism among reptiles.
Off-shell hydrodynamics from holography
Crossley, Michael; Glorioso, Paolo; Liu, Hong; Wang, Yifan
2016-02-18
In this article, we outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual. As a first step, in this paper we restrict to systems with a non-dissipative horizon. By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces. At zeroth order, this action reduces to that proposed by Dubovsky et al. as an off-shell formulation of ideal fluid dynamics.
Hydrodynamics of Microbial Filter-Feeding
NASA Astrophysics Data System (ADS)
Andersen, Anders; Nielsen, Lasse Tor; Dolger, Julia; Kiorboe, Thomas
2016-11-01
Microbial filter-feeders form an important group of plankton with significance to the aquatic food webs. While the concept of filter-feeding is straightforward, our quantitative understanding of microbial filter-feeding leaves a lot to be desired. As a model organism, we focus on the filter-feeding choanoflagellate Diaphanoeca grandis. We quantify the feeding flow using particle tracking, and demonstrate that hydrodynamic theory underestimates the observed clearance rate by an order of magnitude. We find similar discrepancies for other choanoflagellate species, highlighting an apparent paradox. To resolve the paradox we argue that D. grandis and other choanoflagellates must have so far unbeknownst morphological features. Specifically, we suggest a flagellar vane that connects the flagellum to the filter, as known in choanocytes of sponges, creating a radically different, and order of magnitude more capable, pumping mechanism. The Centre for Ocean Life is a VKR Centre of Excellence supported by the Villum Foundation.
An analysis of smoothed particle hydrodynamics
Swegle, J.W.; Attaway, S.W.; Heinstein, M.W.; Mello, F.J.; Hicks, D.L.
1994-03-01
SPH (Smoothed Particle Hydrodynamics) is a gridless Lagrangian technique which is appealing as a possible alternative to numerical techniques currently used to analyze high deformation impulsive loading events. In the present study, the SPH algorithm has been subjected to detailed testing and analysis to determine its applicability in the field of solid dynamics. An important result of the work is a rigorous von Neumann stability analysis which provides a simple criterion for the stability or instability of the method in terms of the stress state and the second derivative of the kernel function. Instability, which typically occurs only for solids in tension, results not from the numerical time integration algorithm, but because the SPH algorithm creates an effective stress with a negative modulus. The analysis provides insight into possible methods for removing the instability. Also, SPH has been coupled into the transient dynamics finite element code PRONTO, and a weighted residual derivation of the SPH equations has been obtained.
Phonon hydrodynamics in two-dimensional materials
NASA Astrophysics Data System (ADS)
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-03-01
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.
On some hydrodynamical aspects of quantum mechanics
NASA Astrophysics Data System (ADS)
Spera, Mauro
2010-02-01
In this note we first set up an analogy between spin and vorticity of a perfect 2d-fluid flow, based on the complex polynomial ( i.e. Borel-Weil) realization of the irreducible unitary representations of SU(2), and looking at the Madelung-Bohm velocity attached to the ensuing spin wave functions. We also show that, in the framework of finite dimensional geometric quantum mechanics, the Schrödinger velocity field on projective Hilbert space is divergence-free (being Killing with respect to the Fubini-Study metric) and fulfils the stationary Euler equation, with pressure proportional to the Hamiltonian uncertainty (squared). We explicitly determine the critical points of the pressure of this “Schrödinger fluid”, together with its vorticity, which turns out to depend on the spacings of the energy levels. These results follow from hydrodynamical properties of Killing vector fields valid in any (finite dimensional) Riemannian manifold, of possible independent interest.
On some hydrodynamical aspects of quantum mechanics
NASA Astrophysics Data System (ADS)
Spera, Mauro
2010-02-01
In this note we first set up an analogy between spin and vorticity of a perfect 2d-fluid flow, based on the complex polynomial (i.e. Borel-Weil) realization of the irreducible unitary representations of SU(2), and looking at the Madelung-Bohm velocity attached to the ensuing spin wave functions. We also show that, in the framework of finite dimensional geometric quantum mechanics, the Schrödinger velocity field on projective Hilbert space is divergence-free (being Killing with respect to the Fubini-Study metric) and fulfils the stationary Euler equation, with pressure proportional to the Hamiltonian uncertainty (squared). We explicitly determine the critical points of the pressure of this "Schrödinger fluid", together with its vorticity, which turns out to depend on the spacings of the energy levels. These results follow from hydrodynamical properties of Killing vector fields valid in any (finite dimensional) Riemannian manifold, of possible independent interest.
Geometry and starvation effects in hydrodynamic lubrication
NASA Technical Reports Server (NTRS)
Brewe, D. E.; Hamrock, B. J.
1982-01-01
Numerical methods were used to determine the effects of lubricant starvation on the minimum film thickness under conditions of a hydrodynamic point contact. Starvation was effected by varying the fluid inlet level. The Reynolds boundary conditions were applied at the cavitation boundary and zero pressure was stipulated at the meniscus or inlet boundary. A minimum-film-thickness equation as a function of both the ratio of dimensionless load to dimensionless speed and inlet supply level was determined. By comparing the film generated under the starved inlet condition with the film generated from the fully flooded inlet, an expression for the film reduction factor was obtained. Based on this factor a starvation threshold was defined as well as a critically starved inlet. The changes in the inlet pressure buildup due to changing the available lubricant supply are presented in the form of three dimensional isometric plots and also in the form of contour plots.
Explicit 2-D Hydrodynamic FEM Program
Lin, Jerry
1996-08-07
DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.
[Hydrodynamic properties of exopolysaccharide-acrylamide copolymer].
Votselko, S K
2000-01-01
The method for producing copolymer EPAA of exopolysaccharide (EPS)--polyacrylamide (PAA) has been presented which was based on microbial exopolysaccharides (enposane, xampane), their mixture and model EPS (xanthane sigma, rodopol P-23). The copolymer was produced by acrylamide polymerization in 1-2% water solutions of polysaccharides, the concentration of acrylamide in the reaction mixture being 4.7-2% and that of polysaccharides 0.1-1% of the weight. Hydrodynamic parameters of the studied polymers have been determined, their heterogenity as to molecular-weight characteristics has been demonstrated. Molecular-weight distribution of copolymers showed that the content of low-molecular fractions decreased, thus the Mw values were (0.08-0.2) x 10(6) Da in contrast to that of exopolysaccharides possessing Mw (1.2-0.4) x 10(6) Da and of polyacrylamide possessing Mw within (2-30) x 10(6) Da. The value of efficient viscosity of copolymers ranged from 120 to 131 mPa.s that was lower than that of polyacrylamide (500 mPa.s), and higher than that of exopolysaccharides (42 mPa.s), and it depended on the sample, raw material, production conditions. A possibility has been shown to produce a new copolymer based on microbial polysaccharides enposane and xampane in the process of acrylamide polymerization. It has been found out that the studied copolymers EPAA differ from initial ones as to their hydrodynamical properties, which determines their preference: better solubility, good glueing properties, prolonged term of preservation, resistance to bacterial pollution.
Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets
NASA Astrophysics Data System (ADS)
Langton, Jonathan; Laughlin, Gregory
2008-02-01
We employ a two-dimensional, grid-based hydrodynamic model to simulate upper atmospheric dynamics on extrasolar giant planets. The hydrodynamic equations of motion are integrated on a rotating, irradiated sphere using a pseudospectral algorithm. We use a two-frequency, two-stream approximation of radiative transfer to model the temperature forcing. This model is well suited to simulate the dynamics of the atmospheres of planets with high orbital eccentricity, which are subject to widely varying irradiation conditions. We identify six such planets, with eccentricities between e = 0.28 and e = 0.93 and semimajor axes from a = 0.0508 AU to a = 0.432 AU, as particularly interesting. For each, we determine the temperature profile and resulting infrared light curves in the 8 μm Spitzer band. Especially notable are the results for HD 80606b, which has the largest eccentricity (e = 0.9321) of any known planet, and HAT-P-2b, which transits its parent star, so that its physical properties are well constrained. Despite the varied orbital parameters, the atmospheric dynamics of these planets display a number of interesting common properties. In all cases, the atmospheric response is primarily driven by the intense irradiation at periastron. The resulting expansion of heated air produces high-velocity turbulent flow, including long-lived circumpolar vortices. In addition, a superrotating acoustic front develops on some planets; the strength of this disturbance depends on both the eccentricity and the temperature gradient from uneven heating. The specifics of the resulting infrared light curves depend strongly on the orbital geometry. We show, however, that the variations on HD 80606b and HAT-P-2b should be readily detectable at 4.5 and 8 μm using Spitzer. These two objects present the most attractive observational targets of all known high-e exoplanets.
On the Hydrodynamical Structure of Superwinds
NASA Astrophysics Data System (ADS)
Rodríguez-González, A.; Tenorio-Tagle, G.; Silich, S.
2006-06-01
We present the hydrodynamical stucture of superwinds (SWs) driven by super star clusters (SSCs). We show the impact of the radiative cooling in the SW properties (Silich et al. 2003, ApJ, 590, 796; Silich et al. 2004, ApJ, 610, 226; Tenorio-Tagle et al. 2005, ApJ, 620, 217). The SSCs recently found by HST in a large variety of starburst galaxies present a typical radius and masses that range from to several times. These are now believed to be the unit of violent star formation in starburst galaxies. The mass and energy injected by stellar winds and SN explosions (in the SSC volume) is totally thermalized via random interactions. This generates the large central over pressure that continuously accelerates the ejected gas and eventually blows it out of the SSC volume. This outflow is called SW. An adiabatic steady wind solution was proposed by Chevalier & Clegg (1985, Nature, 317, 44). However, this solution is not applicable in the case of massive and concentrated cluster. The radiative cooling changes the temperature distribution, it makes that the temperature drops faster to in a very tiny radius than in the adiabatic case. For more energetic clusters, strong radiative cooling promotes the sudden leakage of thermal energy right within the star cluster volume itself, and for the cases in which the radiative losses exceed of stellar energy deposition rate, the cooling becomes catastrophic. For that case the stationary superwind solution is totally inhibited. We solved the hydrodynamics properties of the ejected gas driven by massive stars (via stellar winds and SN) in function of star formation lifetime, and found 3 important stages. And we show the observational signature for each super star cluster stages.
Hydrodynamics of a vertical hydraulic fracture
Narasimhan, T.N.
1987-03-24
We have developed a numerical algorithm, HUBBERT, to simulate the hydrodynamics of a propagating vertical, rectangular fracture in an elastic porous medium. Based on the IFD method, this algorithm assumes fracture geometry to be prescribed. The breakdown and the creation of the incipient fracture is carried out according to the Hubbert-Willis theory. The propagation of the fracture is based on the criterion provided by Griffith, based on energy considerations. The deformation properties of the open fracture are based on simple elasticity solutions. The fracture is assumed to have an elliptical shape to a distance equal to the fracture height, beyond which the shape is assumed to be parallel plate. A consequence of Griffith's criterion is that the fracture must propagate in discrete steps. The parametric studies carried out suggest that for a clear understanding of the hydrodynamics of the hydraulic fracture many hitherto unrecognized parameters must be better understood. Among these parameters one might mention, efficiency, aperture of the newly formed fracture, stiffness of the newly formed fracture, relation between fracture aperture and permeability, and well bore compliance. The results of the studies indicate that the patterns of pressure transients and the magnitudes of fracture length appear to conform to field observations. In particular, the discrete nature of fracture propagation as well as the relevant time scales of interest inferred from the present work seem to be corroborated by seismic monitoring in the field. The results suggest that the estimation of least principal stress can be reliably made either with shut in data or with reinjection data provided that injection rates are very small.
Kinetic simulation of hydrodynamic equivalent capsule implosions
NASA Astrophysics Data System (ADS)
Kwan, Thomas; Le, Ari; Schmitt, Mark; Herrmann, Hans
2016-10-01
We have carried out simulations of direct-drive hydrodynamic equivalent capsule implosion experiments conducted on Omega laser facility at the Laboratory of Laser Energetics of the University of Rochester. The capsules had a glass shell (SiO2) 4.87 μm with an inner diameter of 1086 μm. One was filled with deuterium (D) and tritium (T) at 6.635 and 2.475 atmospheric pressure respectively. The other capsule with D, T, and He-3 at 2.475, 2.475, and 5.55 atmospheric pressure respectively. The capsules were imploded with 60 laser beams with a square pulse length of 0.6ns of total energy of 15.6 kJ. One-dimensional radiation hydrodynamic calculations with HYDRA and kinetic particle/hybrid simulations with LSP are carried out for the post-shot analysis. HYDRA outputs at 0.6ns are linked to LSP, in which the electrons are treated as a fluid while all the ion dynamics is simulated by the standard particle-in-cell technique. Additionally, simulations with the new photon package in LSP are initiated at the beginning of the implosion to include the implosion phase of the capsule. The simulation results of density, temperature, and velocity profiles of the electrons, D, T, He-3, and SiO2species are compared with HYDRA. Detail comparisons among the kinetic simulations, rad-hydro simulations, and experimental results of neutron yield, yield ratio, fusion burn histories, and shell convergence will be presented to assess plasma kinetic effects. Work performed under the auspices of the US DOE by the Los Alamos National Laboratory under Contract No. W7405-ENG-36.
Axially symmetric pseudo-Newtonian hydrodynamics code
NASA Astrophysics Data System (ADS)
Kim, Jinho; Kim, Hee Il; Choptuik, Matthew William; Lee, Hyung Mok
2012-08-01
We develop a numerical hydrodynamics code using a pseudo-Newtonian formulation that uses the weak-field approximation for the geometry, and a generalized source term for the Poisson equation that takes into account relativistic effects. The code was designed to treat moderately relativistic systems such as rapidly rotating neutron stars. The hydrodynamic equations are solved using a finite volume method with high-resolution shock-capturing techniques. We implement several different slope limiters for second-order reconstruction schemes and also investigate higher order reconstructions such as the piecewise parabolic method, essentially non-oscillatory method (ENO) and weighted ENO. We use the method of lines to convert the mixed spatial-time partial differential equations into ordinary differential equations (ODEs) that depend only on time. These ODEs are solved using second- and third-order Runge-Kutta methods. The Poisson equation for the gravitational potential is solved with a multigrid method, and to simplify the boundary condition, we use compactified coordinates which map spatial infinity to a finite computational coordinate using a tangent function. In order to confirm the validity of our code, we carry out four different tests including one- and two-dimensional shock tube tests, stationary star tests of both non-rotating and rotating models, and radial oscillation mode tests for spherical stars. In the shock tube tests, the code shows good agreement with analytic solutions which include shocks, rarefaction waves and contact discontinuities. The code is found to be stable and accurate: for example, when solving a stationary stellar model the fractional changes in the maximum density, total mass, and total angular momentum per dynamical time are found to be 3 × 10-6, 5 × 10-7 and 2 × 10-6, respectively. We also find that the frequencies of the radial modes obtained by the numerical simulation of the steady-state star agree very well with those obtained by
Design of Fiber Optic Sensors for Measuring Hydrodynamic Parameters
NASA Technical Reports Server (NTRS)
Lyons, Donald R.; Quiett, Carramah; Griffin, DeVon (Technical Monitor)
2001-01-01
The science of optical hydrodynamics involves relating the optical properties to the fluid dynamic properties of a hydrodynamic system. Fiber-optic sensors are being designed for measuring the hydrodynamic parameters of various systems. As a flowing fluid makes an encounter with a flat surface, it forms a boundary layer near this surface. The region between the boundary layer and the flat plate contains information about parameters such as viscosity, compressibility, pressure, density, and velocity. An analytical model has been developed for examining the hydrodynamic parameters near the surface of a fiber-optic sensor. An analysis of the conservation of momentum, the continuity equation and the Navier-Stokes equation for compressible flow were used to develop expressions for the velocity and the density as a function of the distance along the flow and above the surface. When examining the flow near the surface, these expressions are used to estimate the sensitivity required to perform direct optical measurements and to derive the shear force for indirect optical measurements. The derivation of this result permits the incorporation of better design parameters for other fiber-based sensors. Future work includes analyzing the optical parametric designs of fiber-optic sensors, modeling sensors to utilize the parameters for hydrodynamics and applying different mixtures of hydrodynamic flow. Finally, the fabrication of fiber-optic sensors for hydrodynamic flow applications of the type described in this presentation could enhance aerospace, submarine, and medical technology.
Two-field radiation hydrodynamics in n spatial dimensions
NASA Astrophysics Data System (ADS)
Larecki, Wieslaw; Banach, Zbigniew
2016-03-01
The two-field radiation hydrodynamics in n spatial dimensions is derived from the kinetic theory of radiation. Both the full-moment (frequency-independent) and spectral (frequency-dependent) formulations of radiation hydrodynamics are considered. The derivation is based on the entropy principle of extended thermodynamics of gases. In the case of the full-moment hydrodynamics, the formulation of the entropy principle introduced by Boillat and Ruggeri (1997 Contin. Mech. Thermodyn. 9 205) is adapted and this suffices to determine the radiation pressure tensor. In the full-moment formulation, the equations of radiation hydrodynamics take the same form for all possible types of radiation statistics. In the spectral formulation, the different radiation pressure tensors are assigned to Bose-Einstein, Fermi-Dirac and Maxwell-Boltzmann statistics, and consequently the different hydrodynamic equations are obtained for each of those statistics types. In order to derive the equations of the spectral radiation hydrodynamics, the relations for the radiation pressure tensor implied by the entropy principle must be supplemented by the additional conditions. Considering the limit of small heat flux, we arrive at the linearized equations of radiation hydrodynamics which assume the same form in both the full-moment and spectral formulations.
Inducer Hydrodynamic Forces in a Cavitating Environment
NASA Technical Reports Server (NTRS)
Skelley, Stephen E.
2004-01-01
Marshall Space Flight Center has developed and demonstrated a measurement device for sensing and resolving the hydrodynamic loads on fluid machinery. The device - a derivative of the six-component wind tunnel balance - senses the forces and moments on the rotating device through a weakened shaft section instrumented with a series of strain gauges. This rotating balance was designed to directly measure the steady and unsteady hydrodynamic loads on an inducer, thereby defining the amplitude and frequency content associated with operating in various cavitation modes. The rotating balance was calibrated statically using a dead-weight load system in order to generate the 6 x 12 calibration matrix later used to convert measured voltages to engineering units. Structural modeling suggested that the rotating assembly first bending mode would be significantly reduced with the balance s inclusion. This reduction in structural stiffness was later confirmed experimentally with a hammer-impact test. This effect, coupled with the relatively large damping associated with the rotating balance waterproofing material, limited the device s bandwidth to approximately 50 Hertz Other pre-test validations included sensing the test article rotating assembly built-in imbalance for two configurations and directly measuring the assembly mass and buoyancy while submerged under water. Both tests matched predictions and confirmed the device s sensitivity while stationary and rotating. The rotating balance was then demonstrated in a water test of a full-scale Space Shuttle Main Engine high-pressure liquid oxygen pump inducer. Experimental data was collected a scaled operating conditions at three flow coefficients across a range of cavitation numbers for the single inducer geometry and radial clearance. Two distinct cavitation modes were observed symmetric tip vortex cavitation and alternate-blade cavitation. Although previous experimental tests on the same inducer demonstrated two additional
Onsager and the theory of hydrodynamic turbulence
NASA Astrophysics Data System (ADS)
Eyink, Gregory L.; Sreenivasan, Katepalli R.
2006-01-01
Lars Onsager, a giant of twentieth-century science and the 1968 Nobel Laureate in Chemistry, made deep contributions to several areas of physics and chemistry. Perhaps less well known is his ground-breaking work and lifelong interest in the subject of hydrodynamic turbulence. He wrote two papers on the subject in the 1940s, one of them just a short abstract. Unbeknownst to Onsager, one of his major results was derived a few years earlier by A. N. Kolmogorov, but Onsager’s work contains many gems and shows characteristic originality and deep understanding. His only full-length article on the subject in 1949 introduced two novel ideas—negative-temperature equilibria for two-dimensional ideal fluids and an energy-dissipation anomaly for singular Euler solutions—that stimulated much later work. However, a study of Onsager’s letters to his peers around that time, as well as his private papers of that period and the early 1970s, shows that he had much more to say about the problem than he published. Remarkably, his private notes of the 1940s contain the essential elements of at least four major results that appeared decades later in the literature: (1) a mean-field Poisson-Boltzmann equation and other thermodynamic relations for point vortices; (2) a relation similar to Kolmogorov’s 4/5 law connecting singularities and dissipation; (3) the modern physical picture of spatial intermittency of velocity increments, explaining anomalous scaling of the spectrum; and (4) a spectral turbulence closure quite similar to the modern eddy-damped quasinormal Markovian equations. This paper is a summary of Onsager’s published and unpublished contributions to hydrodynamic turbulence and an account of their place in the field as the subject has evolved through the years. A discussion is also given of the historical context of the work, especially of Onsager’s interactions with his contemporaries who were acknowledged experts in the subject at the time. Finally, a brief
A multiscale hybrid algorithm for fluctuating hydrodynamics
NASA Astrophysics Data System (ADS)
Williams, Sarah Anne
We develop an algorithmic hybrid for simulating multiscale fluid flow with microscopic fluctuations. Random fluctuations occur in fluids at microscopic scales, and these microscopic fluctuations can lead to macroscopic system effects. For example, in the Rayleigh-Taylor problem, where a relatively heavy gas sits on top of a relatively light gas, spontaneous microscopic fluctuation at the interface of the gases leads to turbulent mixing. Given near-term computational power, the physical and temporal domain on which these systems can be studied using traditional particle simulations is extremely limited. Therefore, we seek algorithmic solutions to increase the effective computing power available to study such problems. We develop an explicit numerical solver for the Landau-Lifshitz Navier-Stokes (LLNS) equations, which incorporate thermal fluctuations into macroscopic hydrodynamics via stochastic; fluxes. A major goal is to correctly preserve the influence of the microscopic fluctuations on the behavior of the system. We show that several classical approaches fail to accurately reproduce fluctuations in energy or density, and we introduce a customized conservative centered scheme with a third-order Runge-Kutta temporal integrator that is specficially designed to produce correct fluctuations in all conserved quantities. We then use the adaptive mesh and algorithm refinement (AMAR) paradigm to create a multiscale hybrid method by coupling our LLNS solver with the direct simulation Monte Carlo (DSMC) particle method. We present numerical tests of systems in and out of equilibrium, including time-dependent systems, and demonstrate dynamic adaptive refinement. Mean system behavior and second moment statistics of our simulations match theoretical values and benchmarks well. We find that particular attention should be paid to the spectrum of the flux at the interface between the particle and continuum methods, specifically at non-hydrodynamic time scales. As an extension of
A comparison of cosmological hydrodynamic codes
NASA Technical Reports Server (NTRS)
Kang, Hyesung; Ostriker, Jeremiah P.; Cen, Renyue; Ryu, Dongsu; Hernquist, Lars; Evrard, August E.; Bryan, Greg L.; Norman, Michael L.
1994-01-01
We present a detailed comparison of the simulation results of various hydrodynamic codes. Starting with identical initial conditions based on the cold dark matter scenario for the growth of structure, with parameters h = 0.5 Omega = Omega(sub b) = 1, and sigma(sub 8) = 1, we integrate from redshift z = 20 to z = O to determine the physical state within a representative volume of size L(exp 3) where L = 64 h(exp -1) Mpc. Five indenpendent codes are compared: three of them Eulerian mesh-based and two variants of the smooth particle hydrodynamics 'SPH' Lagrangian approach. The Eulerian codes were run at N(exp 3) = (32(exp 3), 64(exp 3), 128(exp 3), and 256(exp 3)) cells, the SPH codes at N(exp 3) = 32(exp 3) and 64(exp 3) particles. Results were then rebinned to a 16(exp 3) grid with the exception that the rebinned data should converge, by all techniques, to a common and correct result as N approaches infinity. We find that global averages of various physical quantities do, as expected, tend to converge in the rebinned model, but that uncertainites in even primitive quantities such as (T), (rho(exp 2))(exp 1/2) persists at the 3%-17% level achieve comparable and satisfactory accuracy for comparable computer time in their treatment of the high-density, high-temeprature regions as measured in the rebinned data; the variance among the five codes (at highest resolution) for the mean temperature (as weighted by rho(exp 2) is only 4.5%. Examined at high resolution we suspect that the density resolution is better in the SPH codes and the thermal accuracy in low-density regions better in the Eulerian codes. In the low-density, low-temperature regions the SPH codes have poor accuracy due to statiscal effects, and the Jameson code gives the temperatures which are too high, due to overuse of artificial viscosity in these high Mach number regions. Overall the comparison allows us to better estimate errors; it points to ways of improving this current generation ofhydrodynamic
Ion holes in the hydrodynamic regime in ultracold neutral plasmas
McQuillen, P.; Castro, J.; Strickler, T.; Bradshaw, S. J.; Killian, T. C.
2013-04-15
We describe the creation of localized density perturbations, or ion holes, in an ultracold neutral plasma in the hydrodynamic regime, and show that the holes propagate at the local ion acoustic wave speed. We also observe the process of hole splitting, which results from the formation of a density depletion initially at rest in the plasma. One-dimensional, two-fluid hydrodynamic simulations describe the results well. Measurements of the ion velocity distribution also show the effects of the ion hole and confirm the hydrodynamic conditions in the plasma.
Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway
2012-09-01
ER D C/ CH L TR -1 2 -2 0 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway C oa st al a n d H yd ra u lic s La b or at...distribution is unlimited. ERDC/CHL TR-12-20 September 2012 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway Stephen H. Scott, Jeremy A...A two-dimensional Adaptive Hydraulics (AdH) hydrodynamic model was developed to simulate the Moose Creek Floodway. The Floodway is located
Nucleation and chiral symmetry breaking under controlled hydrodynamic flows
NASA Technical Reports Server (NTRS)
Wu, Xiao-Lun; Martin, Brian; Tharrington, Arnold
1994-01-01
The effects of hydrodynamic convection on nucleation and broken chiral symmetry have been investigated for a simple inorganic molecule, sodium chlorate (NaClO3). Our experiment suggests that the symmetry breaking is a result of hydrodynamic amplification of rare nucleation events. The effect is more pronounced when the primary nucleation occurs on the solute-vapor interface, where mixing in the surface sublayer becomes important. The transition from the achiral to the chiral states appears to be smooth as the hydrodynamic parameters, such as flow rate, are varied.
Heat and mass transfer and hydrodynamics in swirling flows (review)
NASA Astrophysics Data System (ADS)
Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.
2017-02-01
Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.
DBI scalar field theory for QGP hydrodynamics
NASA Astrophysics Data System (ADS)
Nastase, Horatiu
2016-07-01
A way to describe the hydrodynamics of the quark-gluon plasma using a Dirac-Born-Infeld (DBI) action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal (η ≃0 ) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well as a bulk viscosity, and regulates the behavior of the energy density at the shock, making it finite. The resulting fluid satisfies the relativistic Navier-Stokes equation with uμ,ρ ,P ,η defined in terms of ϕ and its derivatives. One finds a relation between the parameters of the theory and the quark-gluon plasma thermodynamics, α /β2=η /(s T ), and by fixing α and β from usual (low multiplicity) particle scattering, one finds T ∝mπ.
Hydrodynamics of micro-swimmers in films
NASA Astrophysics Data System (ADS)
Mathijssen, A. J. T. M.; Doostmohammadi, A.; Yeomans, J. M.; Shendruk, T. N.
2016-11-01
One of the principal mechanisms by which surfaces and interfaces affect microbial life is by perturbing the hydrodynamic flows generated by swimming. By summing a recursive series of image systems we derive a numerically tractable approximation to the three-dimensional flow fields of a Stokeslet (point force) within a viscous film between a parallel no-slip surface and no-shear interface and, from this Green's function, we compute the flows produced by a force- and torque-free micro-swimmer. We also extend the exact solution of Liron & Mochon (1976) to the film geometry, which demonstrates that the image series gives a satisfactory approximation to the swimmer flow fields if the film is sufficiently thick compared to the swimmer size, and we derive the swimmer flows in the thin-film limit. Concentrating on the thick film case, we find that the dipole moment induces a bias towards swimmer accumulation at the no-slip wall rather than the water-air interface, but that higher-order multipole moments can oppose this. Based on the analytic predictions we propose an experimental method to find the multipole coefficient that induces circular swimming trajectories, allowing one to analytically determine the swimmer's three-dimensional position under a microscope.
Hydrodynamic characteristics of sailfish and swordfish
NASA Astrophysics Data System (ADS)
Sagong, Woong; Jeon, Woo-Pyung; Choi, Haecheon
2009-11-01
The sailfish and swordfish are known as fastest sea animals, reaching their maximum speeds of more than 100km/h. Recently, Sagong et al. (2008, Phys. Fluids) investigated the role of V- shaped protrusions existing on the sailfish skin in the skin-friction reduction but those protrusions did not make a direct role in reducing drag. On the other hand, the long bill has been regarded as a device of reducing drag by separation delay through turbulence generation. In the present study, we investigate the hydrodynamic characteristics of sailfish and swordfish by installing the stuffed ones in a wind tunnel and measuring the drag on their bodies and boundary-layer velocities above the body surfaces. The drag coefficients of sailfish and swordfish are 0.0075 and 0.009 based on the free-stream velocity and wetted area, respectively. They are comparable to or smaller than those of other kinds of fish such as the dogfish, tuna and trout. Next, the role of bill on the drag is studied. The drag without bill or with an artificial short bill is lower than that with the original long bill, indicating that the bill does not reduce the drag at all. From the velocity measurement near the body surfaces, we found that flow separation does not occur even without bill, and thus the conjecture that the flow separation is delayed through turbulence generation by the bill is not valid.
Hydrodynamic design of the humpback whale flipper.
Fish, F E; Battle, J M
1995-07-01
The humpback whale (Megaptera novaeangliae) is reported to use its elongate pectoral flippers during swimming maneuvers. The morphology of the flipper from a 9.02-m whale was evaluated with regard to this hydrodynamic function. The flipper had a wing-like, high aspect ratio planform. Rounded tubercles were regularly interspersed along the flipper's leading edge. The flipper was cut into 71 2.5-cm cross-sections and photographed. Except for sections near the distal tip, flipper sections were symmetrical with no camber. Flipper sections had a blunt, rounded leading edge and a highly tapered trailing edge. Placement of the maximum thickness placement for each cross-section varied from 49% of chord at the tip to 19% at mid-span. Section thickness ratio averaged 0.23 with a range of 0.20-0.28. The humpback whale flipper had a cross-sectional design typical of manufactured aerodynamic foils for lift generation. The morphology and placement of leading edge tubercles suggest that they function as enhanced lift devices to control flow over the flipper and maintain lift at high angles of attack. The morphology of the humpback whale flipper suggests that it is adapted for high maneuverability associated with the whale's unique feeding behavior.
An analytical model of flagellate hydrodynamics
NASA Astrophysics Data System (ADS)
Dölger, Julia; Bohr, Tomas; Andersen, Anders
2017-04-01
Flagellates are unicellular microswimmers that propel themselves using one or several beating flagella. We consider a hydrodynamic model of flagellates and explore the effect of flagellar arrangement and beat pattern on swimming kinematics and near-cell flow. The model is based on the analytical solution by Oseen for the low Reynolds number flow due to a point force outside a no-slip sphere. The no-slip sphere represents the cell and the point force a single flagellum. By superposition we are able to model a freely swimming flagellate with several flagella. For biflagellates with left–right symmetric flagellar arrangements we determine the swimming velocity, and we show that transversal forces due to the periodic movements of the flagella can promote swimming. For a model flagellate with both a longitudinal and a transversal flagellum we determine radius and pitch of the helical swimming trajectory. We find that the longitudinal flagellum is responsible for the average translational motion whereas the transversal flagellum governs the rotational motion. Finally, we show that the transversal flagellum can lead to strong feeding currents to localized capture sites on the cell surface.
Hydrodynamics of pedestrians' instability in floodwaters
NASA Astrophysics Data System (ADS)
Arrighi, Chiara; Oumeraci, Hocine; Castelli, Fabio
2017-01-01
People's safety is the first objective to be fulfilled by flood risk mitigation measures, and according to existing reports on the causes of casualties, most of the fatalities are due to inappropriate behaviour such as walking or driving in floodwaters. Currently available experimental data on people instability in floodwaters suffer from a large dispersion primarily depending on the large variability of the physical characteristics of the subjects. This paper introduces a dimensionless mobility parameter θP for people partly immersed in flood flows, which accounts for both flood and subject characteristics. The parameter θP is capable of identifying a unique threshold of instability depending on a Froude number, thus reducing the scatter of existing experimental data. Moreover, a three-dimensional (3-D) numerical model describing the detailed geometry of a human body and reproducing a selection of critical pairs of water depth and velocity is presented. The numerical results in terms of hydrodynamic forces and force coefficients are analysed and discussed. Both the mobility parameter θP and the numerical results hint at the crucial role of the Froude number and relative submergence as the most relevant dimensionless numbers to interpret the loss of stability. Finally, the mobility parameter θP is compared with an analogous dimensionless parameter for vehicles' instability in floodwaters, providing a new contribution to support flood risk management and educating people.
Rheological and fractal hydrodynamics of aerobic granules.
Tijani, H I; Abdullah, N; Yuzir, A; Ujang, Zaini
2015-06-01
The structural and hydrodynamic features for granules were characterized using settling experiments, predefined mathematical simulations and ImageJ-particle analyses. This study describes the rheological characterization of these biologically immobilized aggregates under non-Newtonian flows. The second order dimensional analysis defined as D2=1.795 for native clusters and D2=1.099 for dewatered clusters and a characteristic three-dimensional fractal dimension of 2.46 depicts that these relatively porous and differentially permeable fractals had a structural configuration in close proximity with that described for a compact sphere formed via cluster-cluster aggregation. The three-dimensional fractal dimension calculated via settling-fractal correlation, U∝l(D) to characterize immobilized granules validates the quantitative measurements used for describing its structural integrity and aggregate complexity. These results suggest that scaling relationships based on fractal geometry are vital for quantifying the effects of different laminar conditions on the aggregates' morphology and characteristics such as density, porosity, and projected surface area.
Hydrodynamic optimality of ribbon fin shapes
NASA Astrophysics Data System (ADS)
Bale, Rahul; Maciver, Malcolm; Patankar, Neelesh
2011-11-01
The primary mode of propulsion in gymnotiform and balistiform swimmers is via the undulation of anal and/or dorsal fins, commonly referred to as ribbon fins, attached to a more or less rigid body. Ribbon fins usually have a convex shape as opposed to a rectangular or concave profile. In this work we investigate if there is a hydrodynamic basis underlying this observation. Fully resolved fluid dynamics computations are performed to calculate the mechanical cost of transport (COT) as a measure of swimming efficiency of the fin. We find that the ribbon fin of a black ghost knifefish has lower COT compared to a hypothetical rectangular ribbon fin. In order to quantify this difference in COT between the two fin shapes, we obtain scaling for COT in terms of various parameters which affect the swimming performance of the fin. Using scaling arguments we address the question of how a convex profile, commonly observed in gymnotiform and balistiform swimmers, is optimal compared to rectangular or concave shapes. NSF support is gratefully acknowledged.
Radiation Hydrodynamics: Numerical Aspects and Applications
NASA Astrophysics Data System (ADS)
Dorfi, Ernst A.
Introduction General Remarks on the Numerical Method Time Scales Length Scales Interaction Between Matter and Radiation Moving Fronts Basic Equations Radiation Hydrodynamics (RHD) Coupling Terms Closure Condition Opacity Equation of State Transport Theorem Solution Strategy Integral Form of the RHD Equations Symbolic Notation Moving Coordinates Implicit Discretization Time-centering Adaptive RHD Equations Discretization of Gradients and Divergence Terms Diffusion Advection Initial Conditions Boundary Conditions Artificial Viscosity Discrete RHD Equations Radiative Closure Condition Radiative Boundary Conditions Eddington Factor Adaptive Grids Basic Grid Properties Desired Resolution Spatial and Temporal Smoothing Grid Equation Grid Boundary Conditions Grid Motion Remarks on the Grid Equation First Example: Simple Test Function Second Example: Shock Tube Problem Initial Grid Distributions Further Computational Needs Rational Spline Interpolation CPU-Time Requirements Iteration Procedure and Matrix Inversion Structure of the Jacobi Matrix Time-Step Control Computational Examples Evolution of Supernova Remnants (SNRs) Nonlinear Stellar Pulsations Protostellar Collapse Dust-Driven Winds Radiative Transfer Discussion Internal Accuracy Problems Advantages and Disadvantages of the implict formulation Nuclear and Chemical Networks and Convection Multidimensional Versions Improvements and Further Recommendations References
Hydrodynamically enforced entropic trapping of Brownian particles
NASA Astrophysics Data System (ADS)
Martens, Steffen; Schmid, Gerhard; Straube, Arthur; Schimansky-Geier, Lutz; Hänggi, Peter
2014-03-01
In small systems on length scales spatial confinement causes entropic forces that in turn implies spectacular consequences for the control for mass and charge transport. In view of its importance, recent efforts in theory triggered activities which allow for an approximate description that involves a reduction of dimensionality; thus making detailed predictions tractable. Up to present days, the focus was on the role of conservative forces and its interplay with confinement. Within the presented work, we overcome this limitation and succeeded in considering also non-conservative forces that derive from a vector potential [S. Martens et al., PRL 110, 010601 (2013)]. A relevant application is the fluid flow across microfluidic structures where a solute of Brownian particles is subject to both, an external bias and a pressure-driven flow. Then a new phenomenon emerges; namely, the intriguing finding of identically vanishing average particle flow which is accompanied by a colossal suppression of diffusion. This entropy-induced phenomenon, which we termed hydrodynamically enforced entropic trapping, offers the unique opportunity to separate particles of the same size in a tunable manner [S. Martens et al., Eur. Phys. ST 222, 2453-2463 (2013)].
A Smoothed Particle Hydrodynamics approach for poroelasticity
NASA Astrophysics Data System (ADS)
Osorno, Maria; Steeb, Holger
2016-04-01
Within the framework of the SHynergie project we look to investigate hydraulic fracturing and crack evolving in poroelastic media. We model biphasic media assuming incompressible solid grain and incompressible pore liquid. Modeling evolving fractures and fracture networks in elastic and poroelastic media by mesh-based numerical approaches, like X-FEM, is especially in 3-dim a challenging task. Therefore, we propose a meshless particle method for fractured media based on the Smoothed Particle Hydrodynamics (SPH) approach. SPH is a meshless Lagrangian method highly suitable for the simulation of large deformations including free surfaces and/or interfaces. Within the SPH method, the computational domain is discretized with particles, avoiding the computational expenses of meshing. Our SPH solution is implemented in a parallel computational framework, which allows to simulate large domains more representative of the scale of our study cases. Our implementation is carefully validated against classical mesh-based approaches and compared with classical solutions for consolidation problems. Furthermore, we discuss fracture initiation and propagation in poroelastic rocks at the reservoir scale.
An implicit Smooth Particle Hydrodynamic code
Knapp, Charles E.
2000-05-01
An implicit version of the Smooth Particle Hydrodynamic (SPH) code SPHINX has been written and is working. In conjunction with the SPHINX code the new implicit code models fluids and solids under a wide range of conditions. SPH codes are Lagrangian, meshless and use particles to model the fluids and solids. The implicit code makes use of the Krylov iterative techniques for solving large linear-systems and a Newton-Raphson method for non-linear corrections. It uses numerical derivatives to construct the Jacobian matrix. It uses sparse techniques to save on memory storage and to reduce the amount of computation. It is believed that this is the first implicit SPH code to use Newton-Krylov techniques, and is also the first implicit SPH code to model solids. A description of SPH and the techniques used in the implicit code are presented. Then, the results of a number of tests cases are discussed, which include a shock tube problem, a Rayleigh-Taylor problem, a breaking dam problem, and a single jet of gas problem. The results are shown to be in very good agreement with analytic solutions, experimental results, and the explicit SPHINX code. In the case of the single jet of gas case it has been demonstrated that the implicit code can do a problem in much shorter time than the explicit code. The problem was, however, very unphysical, but it does demonstrate the potential of the implicit code. It is a first step toward a useful implicit SPH code.
Hydrodynamic waves in an anomalous charged fluid
NASA Astrophysics Data System (ADS)
Abbasi, Navid; Davody, Ali; Hejazi, Kasra; Rezaei, Zahra
2016-11-01
We study the collective excitations in a relativistic fluid with an anomalous U (1) current. In 3 + 1 dimensions at zero chemical potential, in addition to ordinary sound modes we find two propagating modes in presence of an external magnetic field. The first one which is a transverse degenerate mode, propagates with a velocity proportional to the coefficient of gravitational anomaly; this is in fact the Chiral Alfvén wave recently found in [1]. Another one is a wave of density perturbation, namely a chiral magnetic wave (CMW). The velocity dependence of CMW on the chiral anomaly coefficient is well known. We compute the dependence of CMW's velocity on the coefficient of gravitational anomaly as well. We also show that the dissipation splits the degeneracy of CAW. At finite chiral charge density we show that in general there may exist five chiral hydrodynamic waves. Of these five waves, one is the CMW while the other four are mixed Modified Sound-Alfvén waves. It turns out that in propagation transverse to the magnetic field no anomaly effect appears while in parallel to the magnetic field we find sound waves become dispersive due to anomaly.
Numerical Convergence In Smoothed Particle Hydrodynamics
NASA Astrophysics Data System (ADS)
Zhu, Qirong; Hernquist, Lars; Li, Yuexing
2015-02-01
We study the convergence properties of smoothed particle hydrodynamics (SPH) using numerical tests and simple analytic considerations. Our analysis shows that formal numerical convergence is possible in SPH only in the joint limit N → ∞, h → 0, and Nnb → ∞, where N is the total number of particles, h is the smoothing length, and Nnb is the number of neighbor particles within the smoothing volume used to compute smoothed estimates. Previous work has generally assumed that the conditions N → ∞ and h → 0 are sufficient to achieve convergence, while holding Nnb fixed. We demonstrate that if Nnb is held fixed as the resolution is increased, there will be a residual source of error that does not vanish as N → ∞ and h → 0. Formal numerical convergence in SPH is possible only if Nnb is increased systematically as the resolution is improved. Using analytic arguments, we derive an optimal compromise scaling for Nnb by requiring that this source of error balance that present in the smoothing procedure. For typical choices of the smoothing kernel, we find Nnb vpropN 0.5. This means that if SPH is to be used as a numerically convergent method, the required computational cost does not scale with particle number as O(N), but rather as O(N 1 + δ), where δ ≈ 0.5, with a weak dependence on the form of the smoothing kernel.
Hydrodynamic Simulations of Gaseous Argon Shock Experiments
NASA Astrophysics Data System (ADS)
Garcia, Daniel; Dattelbaum, Dana; Goodwin, Peter; Morris, John; Sheffield, Stephen; Burkett, Michael
2015-06-01
The lack of published Argon gas shock data motivated an evaluation of the Argon Equation of State (EOS) in gas phase initial density regimes never before reached. In particular, these regimes include initial pressures in the range of 200-500 psi (0.025 - 0.056 g/cc) and initial shock velocities around 0.2 cm/ μs. The objective of the numerical evaluation was to develop a physical understanding of the EOS behavior of shocked and subsequently multiply re-shocked Argon gas initially pressurized to 200-500 psi through Pagosa numerical hydrodynamic simulations utilizing the SESAME equation of state. Pagosa is a Los Alamos National Laboratory 2-D and 3-D Eulerian hydrocode capable of modeling high velocity compressible flow with multiple materials. The approach involved the use of gas gun experiments to evaluate the shock and multiple re-shock behavior of pressurized Argon gas to validate Pagosa simulations and the SESAME EOS. Additionally, the diagnostic capability within the experiments allowed for the EOS to be fully constrained with measured shock velocity, particle velocity and temperature. The simulations demonstrate excellent agreement with the experiments in the shock velocity/particle velocity space, but note unanticipated differences in the ionization front temperatures.
The hydrodynamics of an oscillating porous sphere
NASA Astrophysics Data System (ADS)
Looker, Jason R.; Carnie, Steven L.
2004-01-01
We determine the hydrodynamics of a rigid, weakly permeable sphere undergoing translational oscillations in an incompressible Newtonian fluid. We check using homogenization and scaling arguments that the flow inside the sphere may be modeled by Darcy's law and that the Beavers-Joseph-Saffman (BJS) boundary condition still applies for oscillatory flows, provided the frequency of oscillation is not too high. The BJS boundary condition introduces a slip velocity and to leading order in ɛ=√k /a, where k is the particle permeability and a is the radius, the particle may be regarded as impermeable with a slip length independent of frequency. Under these circumstances we solve for the flow field, pressure distribution and drag explicitly and show their behavior for 0⩽ɛ⩽0.05 and frequencies relevant to electroacoustics (1-10 MHz). From the drag we find the leading order corrections due to particle permeability of the pseudo-steady drag, Basset force and added mass.
Modeling the hydrodynamics of Phloem sieve plates.
Jensen, Kaare Hartvig; Mullendore, Daniel Leroy; Holbrook, Noel Michele; Bohr, Tomas; Knoblauch, Michael; Bruus, Henrik
2012-01-01
Sieve plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin plates, which separate neighboring phloem cells, are perforated by a large number of tiny sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the sieve plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of sieve plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the sieve plate resistance is correlated to the cell lumen resistance, and that the sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.
Temporal dynamics of tunneling: Hydrodynamic approach
NASA Astrophysics Data System (ADS)
Dekel, G.; Fleurov, V.; Soffer, A.; Stucchio, C.
2007-04-01
We use the hydrodynamic representation of the Gross-Pitaevskii and nonlinear Schrödinger equations in order to analyze the dynamics of macroscopic tunneling processes. We observe a tendency to wave breaking and shock formation during the early stages of the tunneling process. A blip in the density distribution appears on the outskirts of the barrier and under proper conditions it may transform into a bright soliton. Our approach, based on the theory of shock formation in solutions of the Burgers equation, allows us to find the parameters of the ejected blip (or soliton if formed), including the velocity of its propagation. The blip in the density is formed regardless of the value and sign of the nonlinearity parameter. However, a soliton may be formed only if this parameter is negative (attraction) and large enough. A criterion is proposed. An ejection of a soliton is also observed numerically. We demonstrate, theoretically and numerically, controlled formation of a soliton through tunneling. The mass of the ejected soliton is controlled by the initial state.
Hydrodynamic optical alignment for microflow cytometry†
Kennedy, Matthew J.; Stelick, Scott J.; Sayam, Lavanya G.; Yen, Andrew; Erickson, David
2013-01-01
A microfabricated flow cytometer has been developed that is capable of detecting nearly all of the microparticles in an aqueous suspension. Current design allows for integrated coupling between an optical fiber-based detection system and the particle stream via hydrodynamic focusing. By adjusting the relative flow-rates at the auxiliary inputs of the focusing manifold, the particle stream can be steered out-of-plane relative to the illuminating laser, and similarly the particle stream can be squeezed or expanded. The microfabricated device was constructed in polydimethylsiloxane with cross-sectional microfluidic dimensions of 125 μm × 125 μm. Using the present device and method, fluorescent microparticles in aqueous solution were counted at an absolute counting efficiency of 91 ± 4%. The coefficient of variation of the fluorescence pulse-heights for far-red fluorescent microparticles was 15%. The device exhibited a linear response to fluorescence intensity calibration microparticles as shown by comparison with a commercial cytometer instrument. PMID:21279198
Hydrodynamics of diatom chains and semiflexible fibres.
Nguyen, Hoa; Fauci, Lisa
2014-07-06
Diatoms are non-motile, unicellular phytoplankton that have the ability to form colonies in the form of chains. Depending upon the species of diatoms and the linking structures that hold the cells together, these chains can be quite stiff or very flexible. Recently, the bending rigidities of some species of diatom chains have been quantified. In an effort to understand the role of flexibility in nutrient uptake and aggregate formation, we begin by developing a three-dimensional model of the coupled elastic-hydrodynamic system of a diatom chain moving in an incompressible fluid. We find that simple beam theory does a good job of describing diatom chain deformation in a parabolic flow when its ends are tethered, but does not tell the whole story of chain deformations when they are subjected to compressive stresses in shear. While motivated by the fluid dynamics of diatom chains, our computational model of semiflexible fibres illustrates features that apply widely to other systems. The use of an adaptive immersed boundary framework allows us to capture complicated buckling and recovery dynamics of long, semiflexible fibres in shear.
Chemical and Hydrodynamical Models of Cometary Comae
NASA Technical Reports Server (NTRS)
Charnley, Steven
2012-01-01
Multi-fluid modelling of the outflowing gases which sublimate from cometary nuclei as they approach the Sun is necessary for understanding the important physical and chemical processes occurring in this complex plasma. Coma chemistry models can be employed to interpret observational data and to ultimately determine chemical composition and structure of the nuclear ices and dust. We describe a combined chemical and hydrodynamical model [1] in which differential equations for the chemical abundances and the energy balance are solved as a function of distance from the cometary nucleus. The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [2]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of new models for the chemistry of cometary comae that include atomic and molecular anions and calculate the impact of these anions on the coma physics and chemistry af the coma.
Combining Hydrodynamic and Evolution Calculations of Rotating Stars
NASA Astrophysics Data System (ADS)
Deupree, R. G.
1996-12-01
Rotation has two primary effects on stellar evolutionary models: the direct influence on the model structure produced by the rotational terms, and the indirect influence produced by rotational instabilities which redistribute angular momentum and composition inside the model. Using a two dimensional, fully implicit finite difference code, I can follow events on both evolutionary and hydrodynamic timescales, thus allowing the simulation of both effects. However, there are several issues concerning how to integrate the results from hydrodynamic runs into evolutionary runs that must be examined. The schemes I have devised for the integration of the hydrodynamic simulations into evolutionary calculations are outlined, and the positive and negative features summarized. The practical differences among the various schemes are small, and a successful marriage between hydrodynamic and evolution calculations is possible.
Concurrent multiscale modelling of atomistic and hydrodynamic processes in liquids.
Markesteijn, Anton; Karabasov, Sergey; Scukins, Arturs; Nerukh, Dmitry; Glotov, Vyacheslav; Goloviznin, Vasily
2014-08-06
Fluctuations of liquids at the scales where the hydrodynamic and atomistic descriptions overlap are considered. The importance of these fluctuations for atomistic motions is discussed and examples of their accurate modelling with a multi-space-time-scale fluctuating hydrodynamics scheme are provided. To resolve microscopic details of liquid systems, including biomolecular solutions, together with macroscopic fluctuations in space-time, a novel hybrid atomistic-fluctuating hydrodynamics approach is introduced. For a smooth transition between the atomistic and continuum representations, an analogy with two-phase hydrodynamics is used that leads to a strict preservation of macroscopic mass and momentum conservation laws. Examples of numerical implementation of the new hybrid approach for the multiscale simulation of liquid argon in equilibrium conditions are provided.
View of hydrodynamic support cylinders, removed from structure and relocated ...
View of hydrodynamic support cylinders, removed from structure and relocated for reconditioning to return them to service. - Marshall Space Flight Center, Saturn V Dynamic Test Facility, East Test Area, Huntsville, Madison County, AL
[Intraocular hydrodynamics failure as a part of age cataract etiopathogenesis].
Ignat'ev, S G; Shilkin, G A; Iartseva, N S; Ignat'eva, S G; Al'-Dandan, I Kh
2011-01-01
59 (105 eyes) patients with initial, premature and mature cataract are studied. Besides 14 patients (19 eyes) 1-2 years after cataract phacoemulsification with IOL implantation were examined. All patients underwent routine ophthalmological examination and tonography. Average indexes of intraocular hydrodynamics coefficients differed from normal rates: in initial and premature cataract F- coefficient was lower by 34% compared to normal, in mature cataract it was higher by 8,9% than upper limit of normal, in pseudophakia by 86,8% lower. In all groups with cataract patients disbalance of intraocular hydrodynamics was revealed in more than 70% cases, and in pseudophakia group it was found in 100%. Disbalance of intraocular hydrodynamics in cataract confirms hypothesis that intraocular hydrodynamics failure is an important part of cataract etiopathogenesis.
Concurrent multiscale modelling of atomistic and hydrodynamic processes in liquids
Markesteijn, Anton; Karabasov, Sergey; Scukins, Arturs; Nerukh, Dmitry; Glotov, Vyacheslav; Goloviznin, Vasily
2014-01-01
Fluctuations of liquids at the scales where the hydrodynamic and atomistic descriptions overlap are considered. The importance of these fluctuations for atomistic motions is discussed and examples of their accurate modelling with a multi-space–time-scale fluctuating hydrodynamics scheme are provided. To resolve microscopic details of liquid systems, including biomolecular solutions, together with macroscopic fluctuations in space–time, a novel hybrid atomistic–fluctuating hydrodynamics approach is introduced. For a smooth transition between the atomistic and continuum representations, an analogy with two-phase hydrodynamics is used that leads to a strict preservation of macroscopic mass and momentum conservation laws. Examples of numerical implementation of the new hybrid approach for the multiscale simulation of liquid argon in equilibrium conditions are provided. PMID:24982246
Small systems and regulator dependence in relativistic hydrodynamics
NASA Astrophysics Data System (ADS)
Spaliński, Michał
2016-10-01
Consistent theories of hydrodynamics necessarily include nonhydrodynamic modes, which can be viewed as a regulator necessary to ensure causality. Under many circumstances the choice of regulator is not relevant, but this is not always the case. In particular, for sufficiently small systems (such as those arising in pA or pp collisions) such dependence may be inevitable. We address this issue in the context of the modern version of Müller-Israel-Stewart theory of relativistic hydrodynamics. In this case, by demanding that the nonhydrodynamic modes do not dominate, we find that regulator dependence becomes inevitable only for multiplicities d N /d Y of the order of a few. This conclusion supports earlier studies based on hydrodynamic simulations of small systems, at the same time providing a simple physical picture of how hydrodynamics can be reliable even in such seemingly extreme conditions.
Hydrodynamic and Salinity Intrusion Model in Selangor River Estuary
NASA Astrophysics Data System (ADS)
Haron, N. F.; Tahir, W.
2016-07-01
A multi-dimensional hydrodynamic and transport model has been used to develop the hydrodynamic and salinity intrusion model for Selangor River Estuary. Delft3D-FLOW was applied to the study area using a curvilinear, boundary fitted grid. External boundary forces included ocean water level, salinity, and stream flow. The hydrodynamic and salinity transport used for the simulation was calibrated and confirmed using data on November 2005 and from May to June 2014. A 13-day period for November 2005 data and a 6-day period of May to June 2014 data were chosen as the calibration and confirmation period because of the availability of data from the field-monitoring program conducted. From the calibration results, it shows that the model was well suited to predict the hydrodynamic and salinity intrusion characteristics of the study area.
Lattice-Boltzmann hydrodynamics of anisotropic active matter
NASA Astrophysics Data System (ADS)
de Graaf, Joost; Menke, Henri; Mathijssen, Arnold J. T. M.; Fabritius, Marc; Holm, Christian; Shendruk, Tyler N.
2016-04-01
A plethora of active matter models exist that describe the behavior of self-propelled particles (or swimmers), both with and without hydrodynamics. However, there are few studies that consider shape-anisotropic swimmers and include hydrodynamic interactions. Here, we introduce a simple method to simulate self-propelled colloids interacting hydrodynamically in a viscous medium using the lattice-Boltzmann technique. Our model is based on raspberry-type viscous coupling and a force/counter-force formalism, which ensures that the system is force free. We consider several anisotropic shapes and characterize their hydrodynamic multipolar flow field. We demonstrate that shape-anisotropy can lead to the presence of a strong quadrupole and octupole moments, in addition to the principle dipole moment. The ability to simulate and characterize these higher-order moments will prove crucial for understanding the behavior of model swimmers in confining geometries.
Viscosity and Vorticity in Reduced Magneto-Hydrodynamics
Joseph, Ilon
2015-08-12
Magneto-hydrodynamics (MHD) critically relies on viscous forces in order for an accurate determination of the electric eld. For each charged particle species, the Braginskii viscous tensor for a magnetized plasma has the decomposition into matrices with special symmetries.
Theoretical study of the crossover into hydrodynamic regime in graphene
NASA Astrophysics Data System (ADS)
Ho, Derek; Yudhistira, Indra; Hu, Ben Yu-Kuang; Adam, Shaffique
Experiments on graphene have recently succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of strong violation of Wiedemann-Franz law, the Gurzhi effect and electronic Poiseuille flow. It is known that electronic systems enter the hydrodynamic regime when electron-electron scattering dominates over electron-impurity and electron-phonon scattering. However, a quantitative study of this transition from the Fermi liquid to hydrodynamic regime is still lacking. In view of this, we quantitatively analyze the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. This yields a quantitative understanding of the onset of hydrodynamic electronic behavior in graphene samples. This work is supported by the National Research Foundation of Singapore under its Fellowship program (NRF-NRFF2012-01) and by the Singapore Ministry of Education and Yale-NUS College through Grant No. R-607-265-01312.
Noether's Theorem of Relativistic-Electromagnetic Ideal Hydrodynamics
NASA Astrophysics Data System (ADS)
Gaspar Elsas, J. H.; Koide, T.; Kodama, T.
2015-06-01
We present a variational approach for relativistic ideal hydrodynamics interacting with electromagnetic fields. The momentum of fluid is introduced as the canonical conjugate variable of the position of a fluid element, which coincides with the conserved quantity derived from Noether's theorem. We further show that our formulation can reproduce the usual electromagnetic hydrodynamics which is obtained so as to satisfy the conservation of the inertia of fluid motion.
Hydrodynamic Instability of Ionization Fronts in HII Regions
Mizuta, A; Kane, J; Ryutov, D; Remington, B; Takabe, H; Pound, M
2003-08-21
The authors investigate hydrodynamic instability of accelerating ionization fronts with two dimensional hydrodynamic simulations. When recombination in the ionized region is turned off, Rayleigh-Taylor instability is effective. Perturbation grows up with classical Rayleigh-Taylor growth rate. In the case with recombination, the local difference of absorption profile works to smooth the surface. The perturbation does not grow and the amplitude follows a damped oscillations with time.
Use of hydrodynamic cavitation in (waste)water treatment.
Dular, Matevž; Griessler-Bulc, Tjaša; Gutierrez-Aguirre, Ion; Heath, Ester; Kosjek, Tina; Krivograd Klemenčič, Aleksandra; Oder, Martina; Petkovšek, Martin; Rački, Nejc; Ravnikar, Maja; Šarc, Andrej; Širok, Brane; Zupanc, Mojca; Žitnik, Miha; Kompare, Boris
2016-03-01
The use of acoustic cavitation for water and wastewater treatment (cleaning) is a well known procedure. Yet, the use of hydrodynamic cavitation as a sole technique or in combination with other techniques such as ultrasound has only recently been suggested and employed. In the first part of this paper a general overview of techniques that employ hydrodynamic cavitation for cleaning of water and wastewater is presented. In the second part of the paper the focus is on our own most recent work using hydrodynamic cavitation for removal of pharmaceuticals (clofibric acid, ibuprofen, ketoprofen, naproxen, diclofenac, carbamazepine), toxic cyanobacteria (Microcystis aeruginosa), green microalgae (Chlorella vulgaris), bacteria (Legionella pneumophila) and viruses (Rotavirus) from water and wastewater. As will be shown, hydrodynamic cavitation, like acoustic, can manifest itself in many different forms each having its own distinctive properties and mechanisms. This was until now neglected, which eventually led to poor performance of the technique. We will show that a different type of hydrodynamic cavitation (different removal mechanism) is required for successful removal of different pollutants. The path to use hydrodynamic cavitation as a routine water cleaning method is still long, but recent results have already shown great potential for optimisation, which could lead to a low energy tool for water and wastewater cleaning.
Hydrodynamic resistance and mobility of deformable objects in microfluidic channels
Sajeesh, P.; Doble, M.; Sen, A. K.
2014-01-01
This work reports experimental and theoretical studies of hydrodynamic behaviour of deformable objects such as droplets and cells in a microchannel. Effects of mechanical properties including size and viscosity of these objects on their deformability, mobility, and induced hydrodynamic resistance are investigated. The experimental results revealed that the deformability of droplets, which is quantified in terms of deformability index (D.I.), depends on the droplet-to-channel size ratio ρ and droplet-to-medium viscosity ratio λ. Using a large set of experimental data, for the first time, we provide a mathematical formula that correlates induced hydrodynamic resistance of a single droplet ΔRd with the droplet size ρ and viscosity λ. A simple theoretical model is developed to obtain closed form expressions for droplet mobility ϕ and ΔRd. The predictions of the theoretical model successfully confront the experimental results in terms of the droplet mobility ϕ and induced hydrodynamic resistance ΔRd. Numerical simulations are carried out using volume-of-fluid model to predict droplet generation and deformation of droplets of different size ratio ρ and viscosity ratio λ, which compare well with that obtained from the experiments. In a novel effort, we performed experiments to measure the bulk induced hydrodynamic resistance ΔR of different biological cells (yeast, L6, and HEK 293). The results reveal that the bulk induced hydrodynamic resistance ΔR is related to the cell concentration and apparent viscosity of the cells. PMID:25538806
Supernova-relevant hydrodynamic instability experiment on the Nova laser
Kane, J.; Arnett, D.; Remington, B.A.; Glendinning, S.G.; Castor, J.; Rubenchik, A.; Berning, M.
1996-02-12
Supernova 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. On quite a separate front, the detrimental effect of hydrodynamic instabilities in inertial confinement fusion (ICF) has long been known. Tools from both areas are being tested on a common project. At Lawrence Livermore National Laboratory (LLNL), the Nova Laser is being used in scaled laboratory experiments of hydrodynamic mixing under supernova-relevant conditions. Numerical simulations of the experiments are being done, using hydrodynamics codes at the Laboratory, and astrophysical codes successfully used to model the hydrodynamics of supernovae. A two-layer package composed of Cu and CH{sub 2} with a single mode sinusoidal 1D perturbation at the interface, shocked by indirect laser drive from the Cu side of the package, produced significant Rayleigh-Taylor (RT) growth in the nonlinear regime. The scale and gross structure of the growth was successfully modeled, by mapping an early-time simulation done with 1D HYADES, a radiation transport code, into 2D CALE, a LLNL hydrodynamics code. The HYADES result was also mapped in 2D into the supernova code PROMETHEUS, which was also able to reproduce the scale and gross structure of the growth.
Supernova-relevant hydrodynamic instability experiment on the Nova laser
NASA Astrophysics Data System (ADS)
Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Castor, J.; Rubenchik, A.
1996-02-01
Supernova 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. On quite a separate front, the detrimental effect of hydrodynamic instabilities in Inertial Confinement Fusion (ICF) has long been known. Tools from both areas are being tested on a common project. At Lawrence Livermore National Laboratory (LLNL), the Nova Laser is being used in scaled laboratory experiments of hydrodynamic mixing under supernova-relevant conditions. Numerical simulations of the experiments are being done, using hydrodynamics codes at the Laboratory, and astrophysical codes successfully used to model the hydrodynamics of supernovae. A two-layer package composed of Cu and CH2 with a single mode sinusoidal 1D perturbation at the interface, shocked by indirect laser drive from the Cu side of the package, produced significant Rayleigh-Taylor (RT) growth in the nonlinear regime. The scale and gross structure of the growth was successfully modeled, by mapping an early-time simulation done with 1D HYADES, a radiation transport code, into 2D CALE, a LLNL hydrodynamics code. The HYADES result was also mapped in 2D into the supernova code PROMETHEUS, which was also able to reproduce the scale and gross structure of the growth.
Leading-order anisotropic hydrodynamics for central collisions
NASA Astrophysics Data System (ADS)
Nopoush, Mohammad; Strickland, Michael; Ryblewski, Radoslaw; Bazow, Dennis; Heinz, Ulrich; Martinez, Mauricio
2015-10-01
We use leading-order anisotropic hydrodynamics to study an azimuthally symmetric boost-invariant quark-gluon plasma. We impose a realistic lattice-based equation of state and perform self-consistent anisotropic freeze-out to hadronic degrees of freedom. We then compare our results for the full spatiotemporal evolution of the quark-gluon plasma and its subsequent freeze-out to results obtained using 1+1D Israel-Stewart second-order viscous hydrodynamics. We find that for small shear viscosities, 4 π η /s ˜1 , the two methods agree well for nucleus-nucleus collisions; however, for large-shear-viscosity-to-entropy-density ratios or proton-nucleus collisions we find important corrections to the Israel-Stewart results for the final particle spectra and the total number of charged particles. Finally, we demonstrate that the total number of charged particles produced is a monotonically increasing function of 4 π η /s in Israel-Stewart viscous hydrodynamics, whereas in anisotropic hydrodynamics it has a maximum at 4 π η /s ˜10 . For all 4 π η /s >0 , we find that for Pb-Pb collisions Israel-Stewart viscous hydrodynamics predicts more dissipative particle production than anisotropic hydrodynamics.
Are hydrodynamic interactions screened in spherically confined micro-compartments?
NASA Astrophysics Data System (ADS)
Aponte-Rivera, Christian; Zia, Roseanna
2016-11-01
We study diffusion of hydrodynamically interacting particles confined by a spherical cavity via dynamic simulation, as a model for intracellular transport. Previous models of 3D confined transport typically assume that hydrodynamic interactions are screened and thus can be neglected, but such assumptions lead to qualitative errors in predictive models. Recent studies show that crowding does not screen hydrodynamic entrainment of freely diffusing particles in unbound suspensions, and that diffusing near a planar wall can weaken (but does not screen) hydrodynamic entrainment. Biophysical and other confined suspensions are crowded, watery compartments, suggesting a role of both crowding and confinement in hydrodynamic entrainment. In the present work, we utilize our new computational framework to study the effect of 3D micro-confinement on particle entrainment, and whether such entrainment is algebraically screened. We measure the hydrodynamic entrainment of one particle in the flow induced by another, in suspensions of arbitrary concentration. We find that the strength of entrainment varies spatially in the cavity, changes qualitatively with the size of the confined particles relative to the enclosure, but varies only quantitatively with the concentration of particles.
Annual Report 2006 for Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications
R. Paul Drake
2007-04-05
We report the ongoing work of our group in hydrodynamics and radiation hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining data using a backlit pinhole with a 100 ps backlighter and beginning to develop the ability to look into the shock tube with optical or x-ray diagnostics. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, using dual-axis radiographic data with backlit pinholes and ungated detectors to complete the data set for a Ph.D. student. We lead a team that is developing a proposal for experiments at the National Ignition Facility and are involved in experiments at NIKE and LIL. All these experiments have applications to astrophysics, discussed in the corresponding papers. We assemble the targets for the experiments at Michigan, where we also prepare many of the simple components. We also have several projects underway in our laboratory involving our x-ray source. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.
Bacterial Swarming: social behaviour or hydrodynamics?
NASA Astrophysics Data System (ADS)
Vermant, Jan
2010-03-01
Bacterial swarming of colonies is typically described as a social phenomenon between bacteria, whereby groups of bacteria collectively move atop solid surfaces. This multicellular behavior, during which the organized bacterial populations are embedded in an extracellular slime layer, is connected to important features such as biofilm formation and virulence. Despite the possible intricate quorum sensing mechanisms that regulate swarming, several physico-chemical phenomena may play a role in the dynamics of swarming and biofilm formation. Especially the striking fingering patterns formed by some swarmer colonies on relatively soft sub phases have attracted the attention as they could be the signatures of an instability. Recently, a parallel has been drawn between the swarming patterns and the spreading of viscous drops under the influence of a surfactant, which lead to similar patterns [1]. Starting from the observation that several of the molecules, essential in swarming systems, are strong biosurfactants, the possibility of flows driven by gradients in surface tension, has been proposed. This Marangoni flows are known to lead to these characteristic patterns. For Rhizobium etli not only the pattern formation, but also the experimentally observed spreading speed has been shown to be consistent with the one expected for Marangoni flows for the surface pressures, thickness, and viscosities that have been observed [2]. We will present an experimental study of swarming colonies of the bacteria Pseudomonas aeruginosa, the pattern formation, the surfactant gradients and height profiles in comparison with predictions of a thin film hydrodynamic model.[4pt] [1] Matar O.K. and Troian S., Phys. Fluids 11 : 3232 (1999)[0pt] [2] Daniels, R et al., PNAS, 103 (40): 14965-14970 (2006)
Hydrodynamic stability of rockets with headwall injection
NASA Astrophysics Data System (ADS)
Abu-Irshaid, Esam M.; Majdalani, Joseph; Casalis, Grégoire
2007-02-01
We investigate the hydrodynamic instability of the full-length, cylindrical models of solid and hybrid rockets with headwall injection. Our baseline is the rotational incompressible flowfield proposed in a recent study (Majdalani and Vyas, "Inviscid models of the classic hybrid rocket," AIAA Paper 2004-3474). The local nonparallel approach is implemented in which the amplitude functions are assumed to be radially dependent at fixed streamwise locations. The usual singularity along the chamber axis is eliminated using Taylor series expansions. As a result, three compatibility relations are derived and substituted for the local boundary conditions along the axis. These depend on whether the tangential wave number q is 0, 1, or larger. Our rotational model is shown to exhibit a range of instability that broadens with successive increases in headwall injection. The lowest frequency below which the flow remains unconditionally stable is observed at ω =28.5 regardless of the headwall injection rate. As usual, the zeroth order tangential mode is found to be the most amplified. Using a representative headwall injection velocity for hybrid rockets, we identify a range of frequencies along which large excursions in pressure and velocity amplitudes are possible. These surges signal the presence of a resonant-like mechanism that is akin to an acoustic instability response. The most excited frequencies vary between 387 and 415 in the vicinity of the headwall. These frequencies are spatially delayed and lowered to 93.8-163.5 when the headwall injection rate is reduced to the level associated with solid rockets. For the most critical streamwise stations, these resurging wave amplitudes are quantified and shown to exhibit spectra that mimic the waterfall data acquired in acoustic instability tests.
NUMERICAL CONVERGENCE IN SMOOTHED PARTICLE HYDRODYNAMICS
Zhu, Qirong; Li, Yuexing; Hernquist, Lars
2015-02-10
We study the convergence properties of smoothed particle hydrodynamics (SPH) using numerical tests and simple analytic considerations. Our analysis shows that formal numerical convergence is possible in SPH only in the joint limit N → ∞, h → 0, and N{sub nb} → ∞, where N is the total number of particles, h is the smoothing length, and N{sub nb} is the number of neighbor particles within the smoothing volume used to compute smoothed estimates. Previous work has generally assumed that the conditions N → ∞ and h → 0 are sufficient to achieve convergence, while holding N{sub nb} fixed. We demonstrate that if N{sub nb} is held fixed as the resolution is increased, there will be a residual source of error that does not vanish as N → ∞ and h → 0. Formal numerical convergence in SPH is possible only if N{sub nb} is increased systematically as the resolution is improved. Using analytic arguments, we derive an optimal compromise scaling for N{sub nb} by requiring that this source of error balance that present in the smoothing procedure. For typical choices of the smoothing kernel, we find N{sub nb} ∝N {sup 0.5}. This means that if SPH is to be used as a numerically convergent method, the required computational cost does not scale with particle number as O(N), but rather as O(N {sup 1} {sup +} {sup δ}), where δ ≈ 0.5, with a weak dependence on the form of the smoothing kernel.
Early hydrodynamic evolution of a stellar collision
Kushnir, Doron; Katz, Boaz
2014-04-20
The early phase of the hydrodynamic evolution following the collision of two stars is analyzed. Two strong shocks propagate from the contact surface and move toward the center of each star at a velocity that is a small fraction of the velocity of the approaching stars. The shocked region near the contact surface has a planar symmetry and a uniform pressure. The density vanishes at the (Lagrangian) surface of contact, and the speed of sound diverges there. The temperature, however, reaches a finite value, since as the density vanishes, the finite pressure is radiation dominated. For carbon-oxygen white dwarf (CO WD) collisions, this temperature is too low for any appreciable nuclear burning shortly after the collision, which allows for a significant fraction of the mass to be highly compressed to the density required for efficient {sup 56}Ni production in the detonation wave that follows. This property is crucial for the viability of collisions of typical CO WD as progenitors of type Ia supernovae, since otherwise only massive (>0.9 M {sub ☉}) CO WDs would have led to such explosions (as required by all other progenitor models). The divergence of the speed of sound limits numerical studies of stellar collisions, as it makes convergence tests exceedingly expensive unless dedicated schemes are used. We provide a new one-dimensional Lagrangian numerical scheme to achieve this. A self-similar planar solution is derived for zero-impact parameter collisions between two identical stars, under some simplifying assumptions (including a power-law density profile), which is the planar version of previous piston problems that were studied in cylindrical and spherical symmetries.
Investigation of hydrodynamic focusing in a microfluidic coulter counter device.
Zhang, Muheng; Lian, Yongsheng; Harnett, Cindy; Brehob, Ellen
2012-08-01
The Coulter technique enables rapid analysis of particles or cells suspended in a fluid stream. In this technique, the cells are suspended in an electrically conductive solution, which is hydrodynamically focused by nonconducting sheath flows. The cells produce a characteristic voltage signal when they interrupt an electrical path. The population and size of the cells can be obtained through analyzing the voltage signal. In a microfluidic Coulter counter device, the hydrodynamic focusing technique is used to position the conducting sample stream and the cells and also to separate close cells to generate distinct signals for each cell and avoid signal jam. The performance of hydrodynamic focusing depends on the relative flow ratio between the sample stream and sheath stream. We use a numerical approach to study the hydrodynamic focusing in a microfluidic Coulter counter device. In this approach, the flow field is described by solving the incompressible Navier-Stokes equations. The sample stream concentration is modeled by an advection-diffusion equation. The motion of the cells is governed by the Newton-Euler equations of motion. Particle motion through the flow field is handled using an overlapping grid technique. A numerical model for studying a microfluidic Coulter counter has been validated. Using the model, the impact of relative flow rate on the performance of hydrodynamic focusing was studied. Our numerical results show that the position of the sample stream can be controlled by adjusting the relative flow rate. Our simulations also show that particles can be focused into the stream and initially close particles can be separated by the hydrodynamic focusing. From our study, we conclude that hydrodynamic focusing provides an effective way to control the position of the sample stream and cells and it also can be used to separate cells to avoid signal jam.
Phonon hydrodynamics and its applications in nanoscale heat transport
NASA Astrophysics Data System (ADS)
Guo, Yangyu; Wang, Moran
2015-09-01
Phonon hydrodynamics is an effective macroscopic method to study heat transport in dielectric solid and semiconductor. It has a clear and intuitive physical picture, transforming the abstract and ambiguous heat transport process into a concrete and evident process of phonon gas flow. Furthermore, with the aid of the abundant models and methods developed in classical hydrodynamics, phonon hydrodynamics becomes much easier to implement in comparison to the current popular approaches based on the first-principle method and kinetic theories involving complicated computations. Therefore, it is a promising tool for studying micro- and nanoscale heat transport in rapidly developing micro and nano science and technology. However, there still lacks a comprehensive account of the theoretical foundations, development and implementation of this approach. This work represents such an attempt in providing a full landscape, from physical fundamental and kinetic theory of phonons to phonon hydrodynamics in view of descriptions of phonon systems at microscopic, mesoscopic and macroscopic levels. Thus a systematical kinetic framework, summing up so far scattered theoretical models and methods in phonon hydrodynamics as individual cases, is established through a frame of a Chapman-Enskog solution to phonon Boltzmann equation. Then the basic tenets and procedures in implementing phonon hydrodynamics in nanoscale heat transport are presented through a review of its recent wide applications in modeling thermal transport properties of nanostructures. Finally, we discuss some pending questions and perspectives highlighted by a novel concept of generalized phonon hydrodynamics and possible applications in micro/nano phononics, which will shed more light on more profound understanding and credible applications of this new approach in micro- and nanoscale heat transport science.
Vortex-Based Aero- and Hydrodynamic Estimation
NASA Astrophysics Data System (ADS)
Hemati, Maziar Sam
Flow control strategies often require knowledge of unmeasurable quantities, thus presenting a need to reconstruct flow states from measurable ones. In this thesis, the modeling, simulation, and estimator design aspects of flow reconstruction are considered. First, a vortex-based aero- and hydrodynamic estimation paradigm is developed to design a wake sensing algorithm for aircraft formation flight missions. The method assimilates wing distributed pressure measurements with a vortex-based wake model to better predict the state of the flow. The study compares Kalman-type algorithms with particle filtering algorithms, demonstrating that the vortex nonlinearities require particle filters to yield adequate performance. Furthermore, the observability structure of the wake is shown to have a negative impact on filter performance regardless of the algorithm applied. It is demonstrated that relative motions can alleviate the filter divergence issues associated with this observability structure. In addition to estimator development, the dissertation addresses the need for an efficient unsteady multi-body aerodynamics testbed for estimator and controller validation studies. A pure vortex particle implementation of a vortex panel-particle method is developed to satisfy this need. The numerical method is demonstrated on the impulsive startup of a flat plate as well as the impulsive startup of a multi-wing formation. It is clear, from these validation studies, that the method is able to accommodate the unsteady wake effects that arise in formation flight missions. Lastly, successful vortex-based estimation is highly dependent on the reliability of the low-order vortex model used in representing the flow of interest. The present treatise establishes a systematic framework for vortex model improvement, grounded in optimal control theory and the calculus of variations. By minimizing model predicted errors with respect to empirical data, the shortcomings of the baseline vortex model
Hydrodynamic complexity in the Earth system
NASA Astrophysics Data System (ADS)
Peltier, W. Richard
Geophysical fluid Dynamics (GFD), as a recognizably distinct subdiscipline in the geophysical sciences, was probably born in the continuing series of Summer Schools in GFD that began at the Woods Hole Oceanographic Institution over 20 years ago. The goal of these schools was to bring together relatively small groups of gifted graduate students with professional academics working in the areas of astrophysics, atmospheric science, geophysics, oceanography and other areas in which models based upon the concepts of classical hydrodynamics were coming to be seen as central to the understanding of a wide range of dynamical processes. The point of this effort was, and remains, to emphasize the commonality of physical process that underlies the behaviour of such apparently unrelated systems and thereby to stimulate the growth of a new group of theoretical geophysicists whose members are as comfortable in analyzing the behaviour of the infinite Reynold number flows that dominate the general circulation of the planetary atmosphere as they are in developing models of the zero Reynolds number flow associated with convection in the earth's mantle. The goal was, and remains, for example, to educate astrophysicists to understand that the double diffusive processes at work in magnetoconvection in the earth's core (say) have many similarities with the processes that operate in the oceanographically important heat-salt system; and similarly to educate oceanographers to understand that the process of Gulf Stream ring formation has everything to do with the process of occlusion of a frontal baroclinic wave in the atmosphere, etc. The summary of the present state and future promise of this young science, by Raymond Hyde, in the preceding paper of this volume, has provided an interesting view of some of the areas of present research that are liable to be most productive of new insights in the immediate future. By way of this invited response to what Dr. Hyde has written I thought I
Progress in MELCOR development and assessment
Summers, R.M.; Kmetyk, L.N.; Cole, R.K. Jr.; Smith, R.C.; Elsbernd, A.E.; Stuart, D.S.; Thompson, S.L.
1995-04-01
MELCOR models the progression of severe accidents in light water reactor nuclear power plants. Recent efforts in MELCOR development to incorporate CORCON-Mod3 models for core-concrete interactions, new models for advanced reactors, and improvements to several other existing models have resulted in release of MELCOR 1.8.3. In addition, continuing efforts to expand the code assessment database have filled in many of the gaps in phenomenological coverage. Efforts are now under way to develop models for chemical interactions of fission products with structural surfaces and for reactions of iodine in the presence of water, and work is also in progress to improve models for the scrubbing of fission products by water pools, the chemical reactions of boron carbide with steam, and the coupling of flow blockages with the hydrodynamics. Several code assessment analyses are in progress, and more are planned.
The issue of cavitation number value in studies of water treatment by hydrodynamic cavitation.
Šarc, Andrej; Stepišnik-Perdih, Tadej; Petkovšek, Martin; Dular, Matevž
2017-01-01
Within the last years there has been a substantial increase in reports of utilization of hydrodynamic cavitation in various applications. It has came to our attention that many times the results are poorly repeatable with the main reason being that the researchers put significant emphasis on the value of the cavitation number when describing the conditions at which their device operates. In the present paper we firstly point to the fact that the cavitation number cannot be used as a single parameter that gives the cavitation condition and that large inconsistencies in the reports exist. Then we show experiments where the influences of the geometry, the flow velocity, the medium temperature and quality on the size, dynamics and aggressiveness of cavitation were assessed. Finally we show that there are significant inconsistencies in the definition of the cavitation number itself. In conclusions we propose a number of parameters, which should accompany any report on the utilization of hydrodynamic cavitation, to make it repeatable and to enable faster progress of science and technology development.
Time-implicit hydrodynamical simulations of stellar interiors: Application to turbulent convection
NASA Astrophysics Data System (ADS)
Viallet, M.
2012-12-01
The talk described the first results on turbulent convection in the envelope of a red giant star obtained with the MUSIC code, a new multi-dimensional time-implicit code devoted to stellar interiors (Viallet, Baraffe & Walder, A&A, 2011). Currently, most of our physical understanding of stellar interiors and evolution largely relies on one-dimensional calculations. The description of complex physical processes like time-dependent turbulent convection, rotation or MHD processes mostly relies on simplified, phenomenological approaches, with a predictive power hampered by the use of several free parameters. These approaches have now reached their limits in the understanding of stellar structure and evolution. The development of multi-dimensional hydrodynamical simulations becomes crucial to progress in the field of stellar physics and to meet the enormous observational efforts aimed at producing data of unprecedented quality (COROT, Kepler GAIA). The MUSIC code solves the hydrodynamical equations in spherical geometry and is based on the finite volume method. The talk presented implicit large eddy simulations of the turbulent convection in a cold giant envelope both in 2D and 3D and covering 80% in radius of the stellar structure. The computational domain includes both the convective envelope and a significant fraction of the radiative zone, allowing for convective penetration. These simulations provide valuable insight to improve the description of turbulent convection in 1D models
Cheng, J Y; Chahine, G L
2001-12-01
The slender body theory, lifting surface theories, and more recently panel methods and Navier-Stokes solvers have been used to study the hydrodynamics of fish swimming. This paper presents progress on swimming hydrodynamics using a boundary integral equation method (or boundary element method) based on potential flow model. The unsteady three-dimensional BEM code 3DynaFS that we developed and used is able to model realistic body geometries, arbitrary movements, and resulting wake evolution. Pressure distribution over the body surface, vorticity in the wake, and the velocity field around the body can be computed. The structure and dynamic behavior of the vortex wakes generated by the swimming body are responsible for the underlying fluid dynamic mechanisms to realize the high-efficiency propulsion and high-agility maneuvering. Three-dimensional vortex wake structures are not well known, although two-dimensional structures termed 'reverse Karman Vortex Street' have been observed and studied. In this paper, simulations about a swimming saithe (Pollachius virens) using our BEM code have demonstrated that undulatory swimming reduces three-dimensional effects due to substantially weakened tail tip vortex, resulting in a reverse Karman Vortex Street as the major flow pattern in the three-dimensional wake of an undulating swimming fish.
Viscosity and dissipative hydrodynamics from effective field theory
NASA Astrophysics Data System (ADS)
Grozdanov, Sašo; Polonyi, Janos
2015-05-01
With the goal of deriving dissipative hydrodynamics from an action, we study classical actions for open systems, which follow from the generic structure of effective actions in the Schwinger-Keldysh closed-time-path (CTP) formalism with two time axes and a doubling of degrees of freedom. The central structural feature of such effective actions is the coupling between degrees of freedom on the two time axes. This reflects the fact that from an effective field theory point of view, dissipation is the loss of energy of the low-energy hydrodynamical degrees of freedom to the integrated-out, UV degrees of freedom of the environment. The dynamics of only the hydrodynamical modes may therefore not possess a conserved stress-energy tensor. After a general discussion of the CTP effective actions, we use the variational principle to derive the energy-momentum balance equation for a dissipative fluid from an effective Goldstone action of the long-range hydrodynamical modes. Despite the absence of conserved energy and momentum, we show that we can construct the first-order dissipative stress-energy tensor and derive the Navier-Stokes equations near hydrodynamical equilibrium. The shear viscosity is shown to vanish in the classical theory under consideration, while the bulk viscosity is determined by the form of the effective action. We also discuss the thermodynamics of the system and analyze the entropy production.
Hydrodynamic Efficiency of Ablation Propulsion with Pulsed Ion Beam
Buttapeng, Chainarong; Yazawa, Masaru; Harada, Nobuhiro; Suematsu, Hisayuki; Jiang Weihua; Yatsui, Kiyoshi
2006-05-02
This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam on the basis of the ion beam-target interaction. We used a one-dimensional hydrodynamic fluid compressible to study the physics involved namely an ablation acceleration behavior and analyzed it as a rocketlike model in order to investigate its hydrodynamic variables for propulsion applications. These variables were estimated by the concept of ablation driven implosion in terms of ablated mass fraction, implosion efficiency, and hydrodynamic energy conversion. Herein, the energy conversion efficiency of 17.5% was achieved. In addition, the results show maximum energy efficiency of the ablation process (ablation efficiency) of 67% meaning the efficiency with which pulsed ion beam energy-ablation plasma conversion. The effects of ion beam energy deposition depth to hydrodynamic efficiency were briefly discussed. Further, an evaluation of propulsive force with high specific impulse of 4000s, total impulse of 34mN and momentum to energy ratio in the range of {mu}N/W was also analyzed.
Hydrodynamic model for picosecond propagation of laser-created nanoplasmas
NASA Astrophysics Data System (ADS)
Saxena, Vikrant; Jurek, Zoltan; Ziaja, Beata; Santra, Robin
2015-06-01
The interaction of a free-electron-laser pulse with a moderate or large size cluster is known to create a quasi-neutral nanoplasma, which then expands on hydrodynamic timescale, i.e., > 1 ps. To have a better understanding of ion and electron data from experiments derived from laser-irradiated clusters, one needs to simulate cluster dynamics on such long timescales for which the molecular dynamics approach becomes inefficient. We therefore propose a two-step Molecular Dynamics-Hydrodynamic scheme. In the first step we use molecular dynamics code to follow the dynamics of an irradiated cluster until all the photo-excitation and corresponding relaxation processes are finished and a nanoplasma, consisting of ground-state ions and thermalized electrons, is formed. In the second step we perform long-timescale propagation of this nanoplasma with a computationally efficient hydrodynamic approach. In the present paper we examine the feasibility of a hydrodynamic two-fluid approach to follow the expansion of spherically symmetric nanoplasma, without accounting for the impact ionization and three-body recombination processes at this stage. We compare our results with the corresponding molecular dynamics simulations. We show that all relevant information about the nanoplasma propagation can be extracted from hydrodynamic simulations at a significantly lower computational cost when compared to a molecular dynamics approach. Finally, we comment on the accuracy and limitations of our present model and discuss possible future developments of the two-step strategy.
Cohesiveness and hydrodynamic properties of young drinking water biofilms.
Abe, Yumiko; Skali-Lami, Salaheddine; Block, Jean-Claude; Francius, Grégory
2012-03-15
Drinking water biofilms are complex microbial systems mainly composed of clusters of different size and age. Atomic force microscopy (AFM) measurements were performed on 4, 8 and 12 weeks old biofilms in order to quantify the mechanical detachment shear stress of the clusters, to estimate the biofilm entanglement rate ξ. This AFM approach showed that the removal of the clusters occurred generally for mechanical shear stress of about 100 kPa only for clusters volumes greater than 200 μm3. This value appears 1000 times higher than hydrodynamic shear stress technically available meaning that the cleaning of pipe surfaces by water flushing remains always incomplete. To predict hydrodynamic detachment of biofilm clusters, a theoretical model has been developed regarding the averaging of elastic and viscous stresses in the cluster and by including the entanglement rate ξ. The results highlighted a slight increase of the detachment shear stress with age and also the dependence between the posting of clusters and their volume. Indeed, the experimental values of ξ allow predicting biofilm hydrodynamic detachment with same order of magnitude than was what reported in the literature. The apparent discrepancy between the mechanical and the hydrodynamic detachment is mainly due to the fact that AFM mechanical experiments are related to the clusters local properties whereas hydrodynamic measurements reflected the global properties of the whole biofilm.
Influence of mass transfer on bubble plume hydrodynamics.
Lima Neto, Iran E; Parente, Priscila A B
2016-03-01
This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities), both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.
Stellar hydrodynamical modeling of dwarf galaxies: simulation methodology, tests, and first results
NASA Astrophysics Data System (ADS)
Vorobyov, Eduard I.; Recchi, Simone; Hensler, Gerhard
2015-07-01
Context. In spite of enormous progress and brilliant achievements in cosmological simulations, they still lack numerical resolution or physical processes to simulate dwarf galaxies in sufficient detail. Accurate numerical simulations of individual dwarf galaxies are thus still in demand. Aims: We aim to improve available numerical techniques to simulate individual dwarf galaxies. In particular, we aim to (i) study in detail the coupling between stars and gas in a galaxy, exploiting the so-called stellar hydrodynamical approach; and (ii) study for the first time the chemodynamical evolution of individual galaxies starting from self-consistently calculated initial gas distributions. Methods: We present a novel chemodynamical code for studying the evolution of individual dwarf galaxies. In this code, the dynamics of gas is computed using the usual hydrodynamics equations, while the dynamics of stars is described by the stellar hydrodynamics approach, which solves for the first three moments of the collisionless Boltzmann equation. The feedback from stellar winds and dying stars is followed in detail. In particular, a novel and detailed approach has been developed to trace the aging of various stellar populations, which facilitates an accurate calculation of the stellar feedback depending on the stellar age. The code has been accurately benchmarked, allowing us to provide a recipe for improving the code performance on the Sedov test problem. Results: We build initial equilibrium models of dwarf galaxies that take gas self-gravity into account and present different levels of rotational support. Models with high rotational support (and hence high degrees of flattening) develop prominent bipolar outflows; a newly-born stellar population in these models is preferentially concentrated to the galactic midplane. Models with little rotational support blow away a large fraction of the gas and the resulting stellar distribution is extended and diffuse. Models that start from non
Modeling High Resolution Flare Spectra Using Hydrodynamic Simulations
NASA Astrophysics Data System (ADS)
Warren, Harry; Doschek, G.
2006-06-01
Understanding the hydrodynamic response of the solar atmosphere to the release of energy during a flare has been a long standing problem in solar physics. Early time-dependent hydrodynamic simulations were able to reproduce the high temperatures and densities observed in solar flares, but were not able to model the observations in any detail. For example, these simulations could not account for the relatively slow decay of the observed emission or the absence of blueshifts in high spectral resolution line profiles at flare onset. We have found that by representing the flare as a succession of independently heated filaments it is possible to reproduce both the evolution of line intensity and the shape of the line profile using hydrodynamic simulations. Here we present detailed comparisons between our simulation results and several flares observed with the Yohkoh Bragg Crystal Spectrometer (BCS). Comparisons with 3D MHD simulations will also be discussed.
Universal Hydrodynamic Mechanisms for Crystallization in Active Colloidal Suspensions
NASA Astrophysics Data System (ADS)
Singh, Rajesh; Adhikari, R.
2016-11-01
The lack of detailed balance in active colloidal suspensions allows dissipation to determine stationary states. Here we show that slow viscous flow produced by polar or apolar active colloids near plane walls mediates attractive hydrodynamic forces that drive crystallization. Hydrodynamically mediated torques tend to destabilize the crystal but stability can be regained through critical amounts of bottom heaviness or chiral activity. Numerical simulations show that crystallization is not nucleational, as in equilibrium, but is preceded by a spinodal-like instability. Harmonic excitations of the active crystal relax diffusively but the normal modes are distinct from an equilibrium colloidal crystal. The hydrodynamic mechanisms presented here are universal and rationalize recent experiments on the crystallization of active colloids.
Distant touch hydrodynamic imaging with an artificial lateral line
Yang, Yingchen; Chen, Jack; Engel, Jonathan; Pandya, Saunvit; Chen, Nannan; Tucker, Craig; Coombs, Sheryl; Jones, Douglas L.; Liu, Chang
2006-01-01
Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment. PMID:17132735
Hydrodynamic body shape analysis and their impact on swimming performance.
Li, Tian-Zeng; Zhan, Jie-Min
2015-01-01
This study presents the hydrodynamic characteristics of different adult male swimmer's body shape using computational fluid dynamics method. This simulation strategy is carried out by CFD fluent code with solving the 3D incompressible Navier-Stokes equations using the RNG k-ε turbulence closure. The water free surface is captured by the volume of fluid (VOF) method. A set of full body models, which is based on the anthropometrical characteristics of the most common male swimmers, is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. The analysis of CFD results revealed that swimmer's body shape has a noticeable effect on the hydrodynamics performances. This explains why male swimmer with an inverted triangle body shape has good hydrodynamic characteristics for competitive swimming.
Origins of hydrodynamic forces on centrifugal pump impellers
NASA Technical Reports Server (NTRS)
Adkins, Douglas R.; Brennen, Christopher E.
1987-01-01
Hydrodynamic interactions that occur between a centrifugal pump impeller and volute are experimentally and theoretically investigated. The theoretical analysis considers the inability of the blades to perfectly guide the flow through the impeller, and also includes a quasi-one dimensional treatment of the flow in the volute. The disturbance at the impeller discharge and the resulting forces are determined by the theoretical model. The model is then extended to obtain the hydrodynamic force perturbations that are caused by the impeller whirling eccentrically in the volute. Under many operating conditions, these force perturbations were found to be destablizing. Comparisons are made between the theoretical model and the experimental measurements of pressure distributions and radial forces on the impeller. The theoretical model yields fairly accurate predictions of the radial forces caused by the flow through the impeller. However, it was found that the pressure acting on the front shroud of the impeller has a substantial effect on the destablizing hydrodynamic forces.
Effects of bioreactor hydrodynamics on the physiology of Streptomyces.
Olmos, E; Mehmood, N; Haj Husein, L; Goergen, J-L; Fick, M; Delaunay, S
2013-03-01
Streptomyces are filamentous bacteria which are widely used industrially for the production of therapeutic biomolecules, especially antibiotics. Bioreactor operating conditions may impact the physiological response of Streptomyces especially agitation and aeration as they influence hydromechanical stress, oxygen and nutrient transfer. The understanding of the coupling between physiological response and bioreactor hydrodynamics lies on a simultaneous description of the flow and transfers encountered by the bacteria and of the microbial response in terms of growth, consumption, morphology, production or intracellular signals. This article reviews the experimental and numerical works dedicated to the study of the coupling between bioreactor hydrodynamics and antibiotics producing Streptomyces. In a first part, the description of hydrodynamics used in these works is presented and then the main relations used. In a second part, the assumptions made in these works are discussed and put into emphasize. Lastly, the various Streptomyces physiological responses observed are detailed and compared.
High-order hydrodynamic algorithms for exascale computing
Morgan, Nathaniel Ray
2016-02-05
Hydrodynamic algorithms are at the core of many laboratory missions ranging from simulating ICF implosions to climate modeling. The hydrodynamic algorithms commonly employed at the laboratory and in industry (1) typically lack requisite accuracy for complex multi- material vortical flows and (2) are not well suited for exascale computing due to poor data locality and poor FLOP/memory ratios. Exascale computing requires advances in both computer science and numerical algorithms. We propose to research the second requirement and create a new high-order hydrodynamic algorithm that has superior accuracy, excellent data locality, and excellent FLOP/memory ratios. This proposal will impact a broad range of research areas including numerical theory, discrete mathematics, vorticity evolution, gas dynamics, interface instability evolution, turbulent flows, fluid dynamics and shock driven flows. If successful, the proposed research has the potential to radically transform simulation capabilities and help position the laboratory for computing at the exascale.
Fluctuating hydrodynamics in a vertically vibrated granular fluid with gravity.
Costantini, Giulio; Puglisi, Andrea
2011-09-01
We investigate hydrodynamic fluctuations in a two-dimensional granular fluid excited by a vibrating base and in the presence of gravity, focusing on the transverse velocity modes. Since the system is inhomogeneous, we measure fluctuations in horizontal layers whose width is smaller than the characteristic hydrodynamic lengths: they can be considered as almost-homogeneous subsystems. The large time decay of the autocorrelations of modes is exponential and compatible with vorticity diffusion due to shear viscosity, as in equilibrium fluids. The velocity structure factor, which strongly deviates from the equilibrium constant behavior, is well reproduced by an effective fluctuating hydrodynamics described by two noise terms: the first associated with vorticity diffusion and the second with the local energy exchange, which have internal and external character, respectively.
Hydrodynamics of spin-polarized transport and spin pendulum
Gurzhi, R. N. Kalinenko, A. N.; Kopeliovich, A. I.; Pyshkin, P. V.; Yanovsky, A. V.
2007-07-15
The dynamics of a nonequilibrium spin system dominated by collisions preserving the total quasimomentum of the interacting electrons and quasiparticles is considered. An analysis of the derived hydrodynamic equations shows that weakly attenuated spin-polarization waves associated with an oscillating drift current can exist in a magnetically inhomogeneous conducting ring. Spin-polarized transport in a ballistic regime of wave propagation through a conductor is also considered, and a simple method is proposed for distinguishing these waves from spin and current oscillations that develop in the hydrodynamic regime. It is shown that a potential difference arises between the leads of an open nonuniformly spin-polarized conductor as a manifestation of spin polarization of electron density. This spin-mediated electrical phenomenon occurs in both hydrodynamic and diffusive limits.
Hydrodynamic interaction of swimming organisms in an inertial regime
NASA Astrophysics Data System (ADS)
Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M.
2016-11-01
We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re˜O (0.1 -100 ) , where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.
Determination of thin hydrodynamic lubricating film thickness using dichromatic interferometry.
Guo, L; Wong, P L; Guo, F; Liu, H C
2014-09-10
This paper introduces the application of dichromatic interferometry for the study of hydrodynamic lubrication. In conventional methods, two beams with different colors are projected consecutively on a static object. By contrast, the current method deals with hydrodynamic lubricated contacts under running conditions and two lasers with different colors are projected simultaneously to form interference images. Dichromatic interferometry incorporates the advantages of monochromatic and chromatic interferometry, which are widely used in lubrication research. This new approach was evaluated statically and dynamically by measuring the inclination of static wedge films and the thickness of the hydrodynamic lubricating film under running conditions, respectively. Results show that dichromatic interferometry can facilitate real-time determination of lubricating film thickness and is well suited for the study of transient or dynamic lubricating problems.
A microfluidic-based hydrodynamic trap: design and implementation.
Tanyeri, Melikhan; Ranka, Mikhil; Sittipolkul, Natawan; Schroeder, Charles M
2011-05-21
We report an integrated microfluidic device for fine-scale manipulation and confinement of micro- and nanoscale particles in free-solution. Using this device, single particles are trapped in a stagnation point flow at the junction of two intersecting microchannels. The hydrodynamic trap is based on active flow control at a fluid stagnation point using an integrated on-chip valve in a monolithic PDMS-based microfluidic device. In this work, we characterize device design parameters enabling precise control of stagnation point position for efficient trap performance. The microfluidic-based hydrodynamic trap facilitates particle trapping using the sole action of fluid flow and provides a viable alternative to existing confinement and manipulation techniques based on electric, optical, magnetic or acoustic force fields. Overall, the hydrodynamic trap enables non-contact confinement of fluorescent and non-fluorescent particles for extended times and provides a new platform for fundamental studies in biology, biotechnology and materials science.
Hydrodynamic interaction of swimming organisms in an inertial regime.
Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M
2016-11-01
We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re∼O(0.1-100), where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.
Ayyaswamy, Portonovo S; Muzykantov, Vladimir; Eckmann, David M; Radhakrishnan, Ravi
2013-02-01
This review discusses current progress and future challenges in the numerical modeling of targeted drug delivery using functionalized nanocarriers (NC). Antibody coated nanocarriers of various size and shapes, also called functionalized nanocarriers, are designed to be injected in the vasculature, whereby they undergo translational and rotational motion governed by hydrodynamic interaction with blood particulates as well as adhesive interactions mediated by the surface antibody binding to target antigens/receptors on cell surfaces. We review current multiscale modeling approaches rooted in computational fluid dynamics and nonequilibrium statistical mechanics to accurately resolve fluid, thermal, as well as adhesive interactions governing nanocarrier motion and their binding to endothelial cells lining the vasculature. We also outline current challenges and unresolved issues surrounding the modeling methods. Experimental approaches in pharmacology and bioengineering are discussed briefly from the perspective of model validation.
Hydrodynamic perception in true seals (Phocidae) and eared seals (Otariidae).
Hanke, Wolf; Wieskotten, Sven; Marshall, Christopher; Dehnhardt, Guido
2013-06-01
Pinnipeds, that is true seals (Phocidae), eared seals (Otariidae), and walruses (Odobenidae), possess highly developed vibrissal systems for mechanoreception. They can use their vibrissae to detect and discriminate objects by direct touch. At least in Phocidae and Otariidae, the vibrissae can also be used to detect and analyse water movements. Here, we review what is known about this ability, known as hydrodynamic perception, in pinnipeds. Hydrodynamic perception in pinnipeds developed convergently to the hydrodynamic perception with the lateral line system in fish and the sensory hairs in crustaceans. So far two species of pinnipeds, the harbour seal (Phoca vitulina) representing the Phocidae and the California sea lion (Zalophus californianus) representing the Otariidae, have been studied for their ability to detect local water movements (dipole stimuli) and to follow hydrodynamic trails, that is the water movements left behind by objects that have passed by at an earlier point in time. Both species are highly sensitive to dipole stimuli and can follow hydrodynamic trails accurately. In the individuals tested, California sea lions were clearly more sensitive to dipole stimuli than harbour seals, and harbour seals showed a superior trail following ability as compared to California sea lions. Harbour seals have also been shown to derive additional information from hydrodynamic trails, such as motion direction, size and shape of the object that caused the trail (California sea lions have not yet been tested). The peculiar undulated shape of the harbour seals' vibrissae appears to play a crucial role in trail following, as it suppresses self-generated noise while the animal is swimming.
Constructing stable 3D hydrodynamical models of giant stars
NASA Astrophysics Data System (ADS)
Ohlmann, Sebastian T.; Röpke, Friedrich K.; Pakmor, Rüdiger; Springel, Volker
2017-02-01
Hydrodynamical simulations of stellar interactions require stable models of stars as initial conditions. Such initial models, however, are difficult to construct for giant stars because of the wide range in spatial scales of the hydrostatic equilibrium and in dynamical timescales between the core and the envelope of the giant. They are needed for, e.g., modeling the common envelope phase where a giant envelope encompasses both the giant core and a companion star. Here, we present a new method of approximating and reconstructing giant profiles from a stellar evolution code to produce stable models for multi-dimensional hydrodynamical simulations. We determine typical stellar stratification profiles with the one-dimensional stellar evolution code mesa. After an appropriate mapping, hydrodynamical simulations are conducted using the moving-mesh code arepo. The giant profiles are approximated by replacing the core of the giant with a point mass and by constructing a suitable continuation of the profile to the center. Different reconstruction methods are tested that can specifically control the convective behaviour of the model. After mapping to a grid, a relaxation procedure that includes damping of spurious velocities yields stable models in three-dimensional hydrodynamical simulations. Initially convectively stable configurations lead to stable hydrodynamical models while for stratifications that are convectively unstable in the stellar evolution code, simulations recover the convective behaviour of the initial model and show large convective plumes with Mach numbers up to 0.8. Examples are shown for a 2 M⊙ red giant and a 0.67 M⊙ asymptotic giant branch star. A detailed analysis shows that the improved method reliably provides stable models of giant envelopes that can be used as initial conditions for subsequent hydrodynamical simulations of stellar interactions involving giant stars.
Colliding Shock Waves and Hydrodynamics in Small Systems.
Chesler, Paul M
2015-12-11
Using numerical holography, we study the collision of a planar sheet of energy with a bounded localized distribution of energy. The collision, which mimics proton-nucleus collisions, produces a localized lump of debris with transverse size R∼1/T_{eff} with T_{eff} the effective temperature, and has large gradients and large transverse flow. Nevertheless, the postcollision evolution is well described by viscous hydrodynamics. Our results bolster the notion that debris produced in proton-nucleus collisions may be modeled using hydrodynamics.
Collective Dynamics in a Binary Mixture of Hydrodynamically Coupled Microrotors
NASA Astrophysics Data System (ADS)
Yeo, Kyongmin; Lushi, Enkeleida; Vlahovska, Petia M.
2015-05-01
We study, numerically, the collective dynamics of self-rotating nonaligning particles by considering a monolayer of spheres driven by constant clockwise or counterclockwise torques. We show that hydrodynamic interactions alter the emergence of large-scale dynamical patterns compared to those observed in dry systems. In dilute suspensions, the flow stirred by the rotors induces clustering of opposite-spin rotors, while at higher densities same-spin rotors phase separate. Above a critical rotor density, dynamic hexagonal crystals form. Our findings underscore the importance of inclusion of the many-body, long-range hydrodynamic interactions in predicting the phase behavior of active particles.
3-D HYDRODYNAMIC MODELING IN A GEOSPATIAL FRAMEWORK
Bollinger, J; Alfred Garrett, A; Larry Koffman, L; David Hayes, D
2006-08-24
3-D hydrodynamic models are used by the Savannah River National Laboratory (SRNL) to simulate the transport of thermal and radionuclide discharges in coastal estuary systems. Development of such models requires accurate bathymetry, coastline, and boundary condition data in conjunction with the ability to rapidly discretize model domains and interpolate the required geospatial data onto the domain. To facilitate rapid and accurate hydrodynamic model development, SRNL has developed a pre- and post-processor application in a geospatial framework to automate the creation of models using existing data. This automated capability allows development of very detailed models to maximize exploitation of available surface water radionuclide sample data and thermal imagery.
Determination of the hydrodynamic friction matrix for various anisotropic particles
NASA Astrophysics Data System (ADS)
Kraft, Daniela; Wittkowksi, Raphael; Löwen, Hartmut; Pine, David
2013-03-01
The relationship between the shape of a colloidal particle and its Brownian motion can be captured by the hydrodynamic friction matrix. It fully describes the translational and rotational diffusion along the particle's main axes as well as the coupling between rotational and translational diffusion. We observed a wide variety of anisotropic colloidal particles with confocal microscopy and calculated the hydrodynamic friction matrix from the particle trajectories. We find that symmetries in the particle shape are reflected in the entries of the friction matrix. We compare our experimentally obtained results with numerical simulations and theoretical predictions. Financial support through a Rubicon grant by the Netherlands Organisation for Scientific Research.
Hydrodynamic pressure of breaking waves on buildings and their interaction
NASA Astrophysics Data System (ADS)
Kashevarova, G. G.; Martirosyan, A. S.
2016-10-01
In the course of numerical experiments the problem hydrodynamic pressure of breaking waves on buildings and their interaction was solved in a related setting, e.g. fluid flow and deformation of the building were calculated simultaneously. The method of calculation allows evaluating the dependence of the hydrodynamic pressure of water flow from the shape of the building in plan, size and orientation relative to the direction of flow stream. This study allowed to perform strength analysis of buildings under the action of breakthrough wave for evaluate the necessity of guard measures.
Hydrodynamic flow of the eutectic under the conditions of superplasticity
NASA Astrophysics Data System (ADS)
Korshak, V. F.; Kryshtal', A. P.; Shapovalov, Yu. A.; Samsonik, A. L.
2010-10-01
In this paper we present original experimental data indicating the manifestation of a hydrodynamic mode of deformation under the conditions of superplasticity. The investigations have been performed on a cast alloy Sn-38 wt % Pb at room temperature. The manifestation of the hydrodynamic mode is related to the high level of internal stresses arising in the process of tension in connection with the occurrence of structural and phase transformations stimulated by plastic deformation in the initially metastable alloy and caused by a preliminary swaging of the samples.
Analyses of hydrodynamic radial forces on centrifugal pump impellers
NASA Technical Reports Server (NTRS)
Adkins, D. R.; Brennen, C. E.
1988-01-01
An experimental and theoretical study of the hydrodynamic interactions occurring between a centrifugal pump impeller and a volute is presented. The theoretical analysis provides a quasi-one-dimensional treatment of the flow in the volute, and it is extended to include the hydrodynamic force perturbations caused by the impeller whirling eccentrically in the volute. It is noted that these perturbations are often destabilizing. The theoretical models were found to accurately predict the radial forces caused by the flow through the impeller. The pressure acting on the front shroud of the impeller is shown to have a significant effect on the destabilizing hydrodyamic forces.
Hydrodynamic spectrum of a superfluid in an elongated trap
NASA Astrophysics Data System (ADS)
Crépin, Pierre-Philippe; Leyronas, Xavier; Chevy, Frédéric
2016-06-01
In this article we study the hydrodynamic spectrum of a superfluid confined in cylindrical trap. We show that the dispersion relation ω(q) of the phonon branch scales like \\sqrt{q} at large q, leading to a vanishingly small superfluid critical velocity. In practice the critical velocity is set by the breakdown of the hydrodynamic approximation. For a broad class of superfluids, this entails a reduction of the critical velocity by a factor (\\hbarω_\\perp/μ_c)1/3 with respect to the free-space prediction (here ω_\\perp is the trapping frequency and μ_\\text{c} the chemical potential of the cloud).
Hydrodynamics of Hemostasis in Sickle-Cell Disease
NASA Astrophysics Data System (ADS)
Cohen, S. I. A.; Mahadevan, L.
2013-03-01
Vaso-occlusion, the stoppage of blood flow in sickle-cell disease, is a complex dynamical process spanning multiple time and length scales. Motivated by recent ex vivo microfluidic measurements of hemostasis using blood from sickle-cell patients, we develop a multiphase model that couples the kinetics and hydrodynamics of a flowing suspension of normal and sickled cells in a fluid. We use the model to derive expressions for the cell velocities and concentrations that quantify the hydrodynamics of hemostasis, and provide simple criteria as well as a phase diagram for occlusion, consistent with our simulations and earlier observations.
Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation
NASA Astrophysics Data System (ADS)
Heller, Michal P.; Spaliński, Michał
2015-08-01
Consistent formulations of relativistic viscous hydrodynamics involve short-lived modes, leading to asymptotic rather than convergent gradient expansions. In this Letter we consider the Müller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. We give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.
Hydrodynamic evolution and jet energy loss in Cu + Cu collisions
Schenke, Bjoern; Jeon, Sangyong; Gale, Charles
2011-04-15
We present results from a hybrid description of Cu + Cu collisions using (3 + 1)-dimensional hydrodynamics (music) for the bulk evolution and a Monte Carlo simulation (martini) for the evolution of high-momentum partons in the hydrodynamical background. We explore the limits of this description by going to small system sizes and determine the dependence on different fractions of wounded nucleon and binary collisions scaling of the initial energy density. We find that Cu + Cu collisions are well described by the hybrid description at least up to 20% central collisions.
pyro: A teaching code for computational astrophysical hydrodynamics
NASA Astrophysics Data System (ADS)
Zingale, M.
2014-10-01
We describe pyro: a simple, freely-available code to aid students in learning the computational hydrodynamics methods widely used in astrophysics. pyro is written with simplicity and learning in mind and intended to allow students to experiment with various methods popular in the field, including those for advection, compressible and incompressible hydrodynamics, multigrid, and diffusion in a finite-volume framework. We show some of the test problems from pyro, describe its design philosophy, and suggest extensions for students to build their understanding of these methods.
Efficient calculation of hydrodynamic properties of OWC-type devices
Evans, D.V.; Porter, R.
1996-12-31
A simple model of an OWC-type wave-energy device is used to illustrate a powerful accurate method for computing the hydrodynamic coefficients when sharp edges are present. The device consists simply of a vertical partially-immersed circular cylinder open at either end, with power being extracted by constricting the flow of the air trapped in the cylinder above the internal free surface. The method involves the use of the theory of pressure distributions for OWC devices and the hydrodynamical coefficients are computed using an accurate Galerkin method which preserves the reciprocity relations.
Quantum cohomology and quantum hydrodynamics from supersymmetric quiver gauge theories
NASA Astrophysics Data System (ADS)
Bonelli, Giulio; Sciarappa, Antonio; Tanzini, Alessandro; Vasko, Petr
2016-11-01
We study the connection between N = 2 supersymmetric gauge theories, quantum cohomology and quantum integrable systems of hydrodynamic type. We consider gauge theories on ALE spaces of A and D-type and discuss how they describe the quantum cohomology of the corresponding Nakajima's quiver varieties. We also discuss how the exact evaluation of local BPS observables in the gauge theory can be used to calculate the spectrum of quantum Hamiltonians of spin Calogero integrable systems and spin Intermediate Long Wave hydrodynamics. This is explicitly obtained by a Bethe Ansatz Equation provided by the quiver gauge theory in terms of its adjacency matrix.
Hydrodynamic effects in a misaligned radial face seal
NASA Technical Reports Server (NTRS)
Etsion, I.
1977-01-01
Hydrodynamic effects in a flat seal having an angular misalignment are analyzed, taking into account the radial variation in seal clearance. An analytical solution for axial force, restoring moment, and transverse moment is presented that covers the whole range from zero to full angular misalignment. Both low pressure seals with cavitating flow and high pressure seals with full fluid film are considered. Strong coupling is demonstrated between angular misalignment and transverse moment which leads the misalignment vector by 90 degrees. This transverse moment, which is entirely due to hydrodynamic effects, is a significant factor in the seal operating mechanism.
Derivation of anomalous hydrodynamics from quantum field theory
NASA Astrophysics Data System (ADS)
Hongo, Masaru; Hayata, Tomoya; Hidaka, Yoshimasa; Minami, Yuki; Noumi, Toshifumi
2014-09-01
Hydrodynamics is a low-energy effective theory which describes a long-distance and long-time behavior of many-body systems. It has been recently pointed out that triangle anomalies affect macroscopic transport properties and generate anomaly-induced transports. These transport phenomena have a common feature that they are dissipationless, or in other words, they don't cause the entropy production. One example is the chiral magnetic effect, which represents the existence of a dissipationless vector current along the magnetic field and is expected to occur in ultra-relativistic heavy ion collisions. In this study, we derive anomalous hydrodynamic equations from the point of view of quantum field theory. Assuming the local Gibbs distribution at initial time, we derive a thermodynamic potential for relativistic hydrodynamics. This action has a form in the curved space-time whose metric is determined by the thermodynamic variables such as the temperature. We show that anomaly-induced transports manifest from this thermodynamic potential if systems do not have the parity symmetry, and, therefore, are dissipationless. We also discuss a relation between our work and other recent approaches that aim at deriving hydrodynamic equations for the parity-violating systems. Hydrodynamics is a low-energy effective theory which describes a long-distance and long-time behavior of many-body systems. It has been recently pointed out that triangle anomalies affect macroscopic transport properties and generate anomaly-induced transports. These transport phenomena have a common feature that they are dissipationless, or in other words, they don't cause the entropy production. One example is the chiral magnetic effect, which represents the existence of a dissipationless vector current along the magnetic field and is expected to occur in ultra-relativistic heavy ion collisions. In this study, we derive anomalous hydrodynamic equations from the point of view of quantum field theory. Assuming
Hydrodynamic simulations of metal ablation by femtosecond laser irradiation
Colombier, J.P.; Combis, P.; Bonneau, F.
2005-04-15
Ablation of Cu and Al targets has been performed with 170 fs laser pulses in the intensity range of 10{sup 12}-10{sup 14} W cm{sup -2}. We compare the measured removal depth with 1D hydrodynamic simulations. The electron-ion temperature decoupling is taken into account using the standard two-temperature model. The influence of the early heat transfer by electronic thermal conduction on hydrodynamic material expansion and mechanical behavior is investigated. A good agreement between experimental and numerical matter ablation rates shows the importance of including solid-to-vapor evolution of the metal in the current modeling of the laser matter interaction.
Topics in physico-chemical hydrodynamics. Progress report No. 2, November 1, 1989--October 31, 1990
Sivashinsky, G.
1990-12-31
This report discusses: Theory of turbulent flame speed; flame extinction by periodic flow field; influence of swirl on the structure and extinction of premixed flames; propagation and extinction of nonsteady spherical flame fronts; geometrically invariant formulation of the intrinsic dynamics of premixed flames; nonlinear dynamics of oscillatory regime of premixed combustion; and pattern formation in premixed flames. (LSP)
Frenkel, A.
1991-08-01
The authors have derived a 3-dimensional dissipative-dispersive evolution equation for the film thickness for films flowing down inclined planes. They have also derived dissipative-dispersive evolution equations for 3-dimensional waves on films flowing down vertical cylinders. They have obtained and simulated numerically highly nonlinear evolution equations describing large-amplitude waves in core-annular flows. They have completed the numerical proof of negativity of the isotropic eddy viscosity for a sinusoidally oscillating triangular-eddy flow. Finally, they have developed an unusual generalization of Landau`s equation to describe the nonlinear evolution of certain (steady) periodic flows slightly above the onset of the (intermediate-wavelength) instability.
Silliman, S.E.
1992-09-30
The initial stages of this project have been focused on equipment development and preliminary experimental efforts. Among the accomplishments to date are the development of a successful flow cell design, proof of the utility of the UV resin, adjustment of the Laser Particle Counter to produce reliable readings, installation of a low particle content water supply, installation of a microscope for viewing discharge samples, development of a fiber/rod optic system for freezing the UV resin in situ and performance of initial experiments on layered and complex heterogeneities. The work is currently following very closely the original schedule for research efforts. Continuing efforts in year one will include continued efforts in simple and complex heterogeneity in two-dimensions, extension into three-dimensions, consideration of the most appropriate methods for creating geologically realistic structures in the laboratory, interaction with other SSP research programs and organization of the spring meeting on intermediate-scale experimentation to be held at Notre Dame. Efforts in year two will be focused on three-dimensional experiments in saturated media, extension of results into unsaturated media, development of techniques for unsaturated media characterization, and development of research ties with outside research interests.
Linearly resummed hydrodynamics in a weakly curved spacetime
NASA Astrophysics Data System (ADS)
Bu, Yanyan; Lublinsky, Michael
2015-04-01
We extend our study of all-order linearly resummed hydrodynamics in a flat space [1, 2] to fluids in weakly curved spaces. The underlying microscopic theory is a finite temperature super-Yang-Mills theory at strong coupling. The AdS/CFT correspondence relates black brane solutions of the Einstein gravity in asymptotically locally AdS5 geometry to relativistic conformal fluids in a weakly curved 4D background. To linear order in the amplitude of hydrodynamic variables and metric perturbations, the fluid's energy-momentum tensor is computed with derivatives of both the fluid velocity and background metric resummed to all orders. We extensively discuss the meaning of all order hydrodynamics by expressing it in terms of the memory function formalism, which is also suitable for practical simulations. In addition to two viscosity functions discussed at length in refs. [1, 2], we find four curvature induced structures coupled to the fluid via new transport coefficient functions. In ref. [3], the latter were referred to as gravitational susceptibilities of the fluid. We analytically compute these coefficients in the hydrodynamic limit, and then numerically up to large values of momenta.
Launch Environment Water Flow Simulations Using Smoothed Particle Hydrodynamics
NASA Technical Reports Server (NTRS)
Vu, Bruce T.; Berg, Jared J.; Harris, Michael F.; Crespo, Alejandro C.
2015-01-01
This paper describes the use of Smoothed Particle Hydrodynamics (SPH) to simulate the water flow from the rainbird nozzle system used in the sound suppression system during pad abort and nominal launch. The simulations help determine if water from rainbird nozzles will impinge on the rocket nozzles and other sensitive ground support elements.
The Quantum Hydrodynamic Model for Semiconductor Devices: Theory and Computations
2007-11-02
Quantum transport effects including electron or hole tunneling through potential barriers and buildup in quantum wells are important in predicting...semiconductor device. A new extension of the classical hydrodynamic model to include quantum transport effects was derived. This "smooth" quantum
Non-dissipative hydrodynamics: effective actions versus entropy current
NASA Astrophysics Data System (ADS)
Bhattacharya, Jyotirmoy; Bhattacharyya, Sayantani; Rangamani, Mukund
2013-02-01
While conventional hydrodynamics incorporating dissipative effects is hard to derive from an action principle, it is nevertheless possible to construct classical actions when the dissipative terms are switched off. In this note we undertake a systematic exploration of such constructions from an effective field theory approach and argue for the existence of non-trivial second order non-dissipative hydrodynamics involving pure energy-momentum transport. We find these fluids to be characterized by five second-order transport coefficients based on the effective action (a three parameter family is Weyl invariant). On the other hand since all flows of such fluids are non-dissipative, they entail zero entropy production; one can therefore understand them using the entropy current formalism which has provided much insight into hydrodynamic transport. An analysis of the most general stress tensor with zero entropy production however turns out to give a seven parameter family of non-dissipative hydrodynamics (a four parameter sub-family being Weyl invariant). The non-dissipative fluids derived from the effective action approach are a special case of the fluid dynamics constrained by conservation of the entropy current. We speculate on the reasons for the mismatch and potential limitations of the effective action approach.
The hydrodynamic vortex: an exactly solvable black hole analogue
NASA Astrophysics Data System (ADS)
Ussembayev, Nail
2016-11-01
We consider the Cauchy problem for the Klein-Gordon equation on an effective Lorentzian manifold describing the sound propagation on a background flow undergoing a subsonic-supersonic transition. For the hydrodynamic vortex model, a particular case of a draining bathtub geometry with non-zero circulation and no draining, we derive an exact solution and discuss its properties.
Viscous QCD matter in a hybrid hydrodynamic+Boltzmann approach
Song Huichao; Bass, Steffen A.; Heinz, Ulrich
2011-02-15
A hybrid transport approach for the bulk evolution of viscous QCD matter produced in ultra-relativistic heavy-ion collisions is presented. The expansion of the dense deconfined phase of the reaction is modeled with viscous hydrodynamics, while the dilute late hadron gas stage is described microscopically by the Boltzmann equation. The advantages of such a hybrid approach lie in the improved capability of handling large dissipative corrections in the late dilute phase of the reaction, including a realistic treatment of the nonequilibrium hadronic chemistry and kinetic freeze-out. By varying the switching temperature at which the hydrodynamic output is converted to particles for further propagation with the Boltzmann cascade we test the ability of the macroscopic hydrodynamic approach to emulate the microscopic evolution during the hadronic stage and extract the temperature dependence of the effective shear viscosity of the hadron resonance gas produced in the collision. We find that the extracted values depend on the prior hydrodynamic history and hence do not represent fundamental transport properties of the hadron resonance gas. We conclude that viscous fluid dynamics does not provide a faithful description of hadron resonance gas dynamics with predictive power, and that both components of the hybrid approach are needed for a quantitative description of the fireball expansion and its freeze-out.
Machine learning and cosmological simulations - II. Hydrodynamical simulations
NASA Astrophysics Data System (ADS)
Kamdar, Harshil M.; Turk, Matthew J.; Brunner, Robert J.
2016-04-01
We extend a machine learning (ML) framework presented previously to model galaxy formation and evolution in a hierarchical universe using N-body + hydrodynamical simulations. In this work, we show that ML is a promising technique to study galaxy formation in the backdrop of a hydrodynamical simulation. We use the Illustris simulation to train and test various sophisticated ML algorithms. By using only essential dark matter halo physical properties and no merger history, our model predicts the gas mass, stellar mass, black hole mass, star formation rate, g - r colour, and stellar metallicity fairly robustly. Our results provide a unique and powerful phenomenological framework to explore the galaxy-halo connection that is built upon a solid hydrodynamical simulation. The promising reproduction of the listed galaxy properties demonstrably place ML as a promising and a significantly more computationally efficient tool to study small-scale structure formation. We find that ML mimics a full-blown hydrodynamical simulation surprisingly well in a computation time of mere minutes. The population of galaxies simulated by ML, while not numerically identical to Illustris, is statistically robust and physically consistent with Illustris galaxies and follows the same fundamental observational constraints. ML offers an intriguing and promising technique to create quick mock galaxy catalogues in the future.
KEPLER: General purpose 1D multizone hydrodynamics code
NASA Astrophysics Data System (ADS)
Weaver, T. A.; Zimmerman, G. B.; Woosley, S. E.
2017-02-01
KEPLER is a general purpose stellar evolution/explosion code that incorporates implicit hydrodynamics and a detailed treatment of nuclear burning processes. It has been used to study the complete evolution of massive and supermassive stars, all major classes of supernovae, hydrostatic and explosive nucleosynthesis, and x- and gamma-ray bursts on neutron stars and white dwarfs.
Water Flow Simulation using Smoothed Particle Hydrodynamics (SPH)
NASA Technical Reports Server (NTRS)
Vu, Bruce; Berg, Jared; Harris, Michael F.
2014-01-01
Simulation of water flow from the rainbird nozzles has been accomplished using the Smoothed Particle Hydrodynamics (SPH). The advantage of using SPH is that no meshing is required, thus the grid quality is no longer an issue and accuracy can be improved.
HYDRODYNAMIC AND TRANSPORT MODELING STUDY IN A HIGHLY STRATIFIED ESTUARY
This paper presents the preliminary results of hydrodynamic and salinity predictions and the implications to an ongoing contaminated sediment transport and fate modeling effort in the Lower Duwamish Waterway (LDW), Seattle, Washington. The LDW is highly strati-fied when freshwate...
Extreme hydrodynamic atmospheric loss near the critical thermal escape regime
NASA Astrophysics Data System (ADS)
Erkaev, N. V.; Lammer, H.; Odert, P.; Kulikov, Yu. N.; Kislyakova, K. G.
2015-04-01
By considering martian-like planetary embryos inside the habitable zone of solar-like stars we study the behaviour of the hydrodynamic atmospheric escape of hydrogen for small values of the Jeans escape parameter β < 3, near the base of the thermosphere, that is defined as a ratio of the gravitational and thermal energy. Our study is based on a 1D hydrodynamic upper atmosphere model that calculates the volume heating rate in a hydrogen-dominated thermosphere due to the absorption of the stellar soft X-ray and extreme ultraviolet (XUV) flux. In case of a monatomic gas, we find that when the β value near the mesopause/homopause level exceeds a critical value of ˜2.5, there exists a steady hydrodynamic solution with a smooth transition from subsonic to supersonic flow. For a fixed XUV flux, the escape rate of the upper atmosphere is an increasing function of the temperature at the lower boundary. Our model results indicate a crucial enhancement of the atmospheric escape rate, when the Jeans escape parameter β decreases to this critical value. When β becomes ≤2.5, there is no stationary hydrodynamic transition from subsonic to supersonic flow. This is the case of a fast non-stationary atmospheric expansion that results in extreme thermal atmospheric escape rates.
Young swimmers' classification based on kinematics, hydrodynamics, and anthropometrics.
Barbosa, Tiago M; Morais, Jorge E; Costa, Mário J; Goncalves, José; Marinho, Daniel A; Silva, António J
2014-04-01
The aim of this article has been to classify swimmers based on kinematics, hydrodynamics, and anthropometrics. Sixty-seven young swimmers made a maximal 25 m front-crawl to measure with a speedometer the swimming velocity (v), speed-fluctuation (dv) and dv normalized to v (dv/v). Another two 25 m bouts with and without carrying a perturbation device were made to estimate active drag coefficient (CDa). Trunk transverse surface area (S) was measured with photogrammetric technique on land and in the hydrodynamic position. Cluster 1 was related to swimmers with a high speed fluctuation (ie, dv and dv/v), cluster 2 with anthropometrics (ie, S) and cluster 3 with a high hydrodynamic profile (ie, CDa). The variable that seems to discriminate better the clusters was the dv/v (F=53.680; P<.001), followed by the dv (F=28.506; P<.001), CDa (F=21.025; P<.001), S (F=6.297; P<.01) and v (F=5.375; P=.01). Stepwise discriminant analysis extracted 2 functions: Function 1 was mainly defined by dv/v and S (74.3% of variance), whereas function 2 was mainly defined by CDa (25.7% of variance). It can be concluded that kinematics, hydrodynamics and anthropometrics are determinant domains in which to classify and characterize young swimmers' profiles.
Thigmomorphogenetic responses of an aquatic macrophyte to hydrodynamic stress.
Schoelynck, Jonas; Puijalon, Sara; Meire, Patrick; Struyf, Eric
2015-01-01
The response of aquatic plants to abiotic factors is a crucial study topic, because the diversity of aquatic vegetation is strongly related to specific adaptations to a variety of environments. This biodiversity ensures resilience of aquatic communities to new and changing ecological conditions. In running water, hydrodynamic disturbance is one of the key factors in this context. While plant adaptations to resource stress (nutrients, light…) are well documented, adaptations to mechanical stress, particularly flow, are largely unknown. The submerged species Egeria densa was used in an experiment to detect whether the presence or absence of hydrodynamic stress causes plant thigmomorphogenetic responses (i) in terms of plant biogenic silica (BSi), cellulose and lignin concentrations, and (ii) in terms of plant strength. Plant silica concentrations, as well as lignin concentrations were significantly higher in presence of hydrodynamic stress. These physiological changes are accompanied by some significant changes in stem biomechanical traits: stem resistance to tensile forces (breaking force and breaking strength) and stiffness were higher for plants exposed to hydrodynamic stress. We conclude that the response of this aquatic plant species to mechanical stress is likely the explaining factor for a higher capacity to tolerate stress through the production of mechanically hardened shoots.
Supernova-relevant hydrodynamic instability experiments on the Nova Laser
Kane, J.; arnett, D.; Remington, B.A.; Glendinning, S.G.; wallace, R.; Mangan, R.; Rubenchik, A.; Fryxell, B.A.
1997-04-18
Supernova 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. The target consists of two-layer planar package composed on 85 micron Cu backed by 500 micron CH2, having a single mode sinusoidal perturbation at the interface, with gamma = 200 microns, nuo + 20 microns. The Nova laser is used to generate a 10-15 Mbar (10- 15x10{sup 12} dynes/cm2) shock at the interface, which triggers perturbation growth, due to the Richtmyer-Meshov instability followed by the Raleigh-Taylor instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at the intermediate times, up to a few x10{sup 3} s. The experiment is modeled using the hydrodynamic codes HYADES and CALE, and the supernova code PROMETHEUS. We are designing experiments to test the differences in the growth of 2D vs 3D single mode perturbations; such differences may help explain the high observed velocities of radioactive core material in SN1987A. Results of the experiments and simulations are presented.
Hydrodynamic Liner Experiments Using the Ranchero Flux Compression Generator System
Goforth, J.H.; Atchison, W.L.; Fowler, C.M.; Lopez, E.A.; Oona, H.; Tasker, D.G.; King, J.C.; Herrera, D.H.; Torres, D.T.; Sena, F.C.; McGuire, J.A.; Reinovsky, R.E.; Stokes, J.L.; Tabaka, L.J.; Garcia, O.F.; Faehl, R.J.; Lindemuth, I.R.; Keinigs, R.K.; Broste, B.
1998-10-18
The authors have developed a system for driving hydrodynamic liners at currents approaching 30 MA. Their 43 cm module will deliver currents of interest, and when fully developed, the 1.4 m module will allow similar currents with more total system inductance. With these systems they can perform interesting physics experiments and support the Atlas development effort.
Thigmomorphogenetic responses of an aquatic macrophyte to hydrodynamic stress
Schoelynck, Jonas; Puijalon, Sara; Meire, Patrick; Struyf, Eric
2015-01-01
The response of aquatic plants to abiotic factors is a crucial study topic, because the diversity of aquatic vegetation is strongly related to specific adaptations to a variety of environments. This biodiversity ensures resilience of aquatic communities to new and changing ecological conditions. In running water, hydrodynamic disturbance is one of the key factors in this context. While plant adaptations to resource stress (nutrients, light…) are well documented, adaptations to mechanical stress, particularly flow, are largely unknown. The submerged species Egeria densa was used in an experiment to detect whether the presence or absence of hydrodynamic stress causes plant thigmomorphogenetic responses (i) in terms of plant biogenic silica (BSi), cellulose and lignin concentrations, and (ii) in terms of plant strength. Plant silica concentrations, as well as lignin concentrations were significantly higher in presence of hydrodynamic stress. These physiological changes are accompanied by some significant changes in stem biomechanical traits: stem resistance to tensile forces (breaking force and breaking strength) and stiffness were higher for plants exposed to hydrodynamic stress. We conclude that the response of this aquatic plant species to mechanical stress is likely the explaining factor for a higher capacity to tolerate stress through the production of mechanically hardened shoots. PMID:25699070
Effect of hydrodynamic pressure processing on chevon quality characteristics
Technology Transfer Automated Retrieval System (TEKTRAN)
Hydrodynamic pressure processing (HDP) technology, which involves exposure of packaged meat to a supersonic shock wave under water created by a small amount of explosive, has been shown to improve meat tenderness, but its effect on chevon tenderness has not been studied so far. The objective of this...
High Efficiency Hydrodynamic DNA Fragmentation in a Bubbling System
Li, Lanhui; Jin, Mingliang; Sun, Chenglong; Wang, Xiaoxue; Xie, Shuting; Zhou, Guofu; van den Berg, Albert; Eijkel, Jan C. T.; Shui, Lingling
2017-01-01
DNA fragmentation down to a precise fragment size is important for biomedical applications, disease determination, gene therapy and shotgun sequencing. In this work, a cheap, easy to operate and high efficiency DNA fragmentation method is demonstrated based on hydrodynamic shearing in a bubbling system. We expect that hydrodynamic forces generated during the bubbling process shear the DNA molecules, extending and breaking them at the points where shearing forces are larger than the strength of the phosphate backbone. Factors of applied pressure, bubbling time and temperature have been investigated. Genomic DNA could be fragmented down to controllable 1–10 Kbp fragment lengths with a yield of 75.30–91.60%. We demonstrate that the ends of the genomic DNAs generated from hydrodynamic shearing can be ligated by T4 ligase and the fragmented DNAs can be used as templates for polymerase chain reaction. Therefore, in the bubbling system, DNAs could be hydrodynamically sheared to achieve smaller pieces in dsDNAs available for further processes. It could potentially serve as a DNA sample pretreatment technique in the future. PMID:28098208
Hydrodynamic studies of oxygen, neon, and magnesium novae
NASA Technical Reports Server (NTRS)
Starrfield, Sumner; Sparks, W. M.; Truran, J. W.
1987-01-01
Results are presented from recent theoretical studies that have examined the properties of nova outbursts on ONeMg white dwarfs. These outbursts are much more violent and occur much more frequently than outbursts on CO white dwarfs. Hydrodynamic simulations of both kinds of outbursts are in excellent agreement with the observations.
Comparison of hydrostatic and hydrodynamic pressure to inactivate foodborne viruses
Technology Transfer Automated Retrieval System (TEKTRAN)
The effect of high hydrostatic pressure (HPP) and hydrodynamic pressure (HDP), in combination with chemical treatments, was evaluated for inactivation of foodborne viruses and non-pathogenic surrogates in a pork sausage product. Sausages were immersed in water, 100 ppm EDTA, or 2 percent lactoferrin...
MONTE CARLO RADIATION-HYDRODYNAMICS WITH IMPLICIT METHODS
Roth, Nathaniel; Kasen, Daniel
2015-03-15
We explore the application of Monte Carlo transport methods to solving coupled radiation-hydrodynamics (RHD) problems. We use a time-dependent, frequency-dependent, three-dimensional radiation transport code that is special relativistic and includes some detailed microphysical interactions such as resonant line scattering. We couple the transport code to two different one-dimensional (non-relativistic) hydrodynamics solvers: a spherical Lagrangian scheme and a Eulerian Godunov solver. The gas–radiation energy coupling is treated implicitly, allowing us to take hydrodynamical time-steps that are much longer than the radiative cooling time. We validate the code and assess its performance using a suite of radiation hydrodynamical test problems, including ones in the radiation energy dominated regime. We also develop techniques that reduce the noise of the Monte Carlo estimated radiation force by using the spatial divergence of the radiation pressure tensor. The results suggest that Monte Carlo techniques hold promise for simulating the multi-dimensional RHD of astrophysical systems.
Hydrodynamic Properties of Planing Surfaces and Flying Boats
NASA Technical Reports Server (NTRS)
Sokolov, N. A.
1950-01-01
The study of the hydrodynamic properties of planing bottom of flying boats and seaplane floats is at the present time based exclusively on the curves of towing tests conducted in tanks. In order to provide a rational basis for the test procedure in tanks and practical design data, a theoretical study must be made of the flow at the step and relations derived that show not only qualitatively but quantitatively the inter-relations of the various factors involved. The general solution of the problem of the development of hydrodynamic forces during the motion of the seaplane float or flying boat is very difficult for it is necessary to give a three-dimensional solution, which does not always permit reducing the analysis to the form of workable computation formulas. On the other had, the problem is complicated by the fact that the object of the analysis is concerned with two fluid mediums, namely, air and water, which have a surface of density discontinuity between them. The theoretical and experimental investigations on the hydrodynamics of a ship cannot be completely carried over to the design of floats and flying-boat hulls, because of the difference in the shape of the contour lines of the bodies, and, because of the entirely different flow conditions from the hydrodynamic viewpoint.
High Efficiency Hydrodynamic DNA Fragmentation in a Bubbling System
NASA Astrophysics Data System (ADS)
Li, Lanhui; Jin, Mingliang; Sun, Chenglong; Wang, Xiaoxue; Xie, Shuting; Zhou, Guofu; van den Berg, Albert; Eijkel, Jan C. T.; Shui, Lingling
2017-01-01
DNA fragmentation down to a precise fragment size is important for biomedical applications, disease determination, gene therapy and shotgun sequencing. In this work, a cheap, easy to operate and high efficiency DNA fragmentation method is demonstrated based on hydrodynamic shearing in a bubbling system. We expect that hydrodynamic forces generated during the bubbling process shear the DNA molecules, extending and breaking them at the points where shearing forces are larger than the strength of the phosphate backbone. Factors of applied pressure, bubbling time and temperature have been investigated. Genomic DNA could be fragmented down to controllable 1–10 Kbp fragment lengths with a yield of 75.30–91.60%. We demonstrate that the ends of the genomic DNAs generated from hydrodynamic shearing can be ligated by T4 ligase and the fragmented DNAs can be used as templates for polymerase chain reaction. Therefore, in the bubbling system, DNAs could be hydrodynamically sheared to achieve smaller pieces in dsDNAs available for further processes. It could potentially serve as a DNA sample pretreatment technique in the future.
Cavitation Generation and Usage Without Ultrasound: Hydrodynamic Cavitation
NASA Astrophysics Data System (ADS)
Gogate, Parag R.; Pandit, Aniruddha B.
Hydrodynamic Cavitation, which was and is still looked upon as an unavoidable nuisance in the flow systems, can be a serious contender as an alternative to acoustic cavitation for harnessing the spectacular effects of cavitation in physical and chemical processing. The present chapter covers the basics of hydrodynamic cavitation including the considerations for the bubble dynamics analysis, reactor designs and recommendations for optimum operating parameters. An overview of applications in different areas of physical, chemical and biological processing on scales ranging from few grams to several hundred kilograms has also been presented. Since hydrodynamic cavitation was initially proposed as an alternative to acoustic cavitation, it is necessary to compare the efficacy of both these modes of cavitations for a variety of applications and hence comparisons have been discussed either on the basis of energy efficiency or based on the scale of operation. Overall it appears that hydrodynamic cavitation results in conditions similar to those generated using acoustic cavitation but at comparatively much larger scale of operation and with better energy efficiencies.
Prototype Mixed Finite Element Hydrodynamics Capability in ARES
Rieben, R N
2008-07-10
This document describes work on a prototype Mixed Finite Element Method (MFEM) hydrodynamics algorithm in the ARES code, and its application to a set of standard test problems. This work is motivated by the need for improvements to the algorithms used in the Lagrange hydrodynamics step to make them more robust. We begin by identifying the outstanding issues with traditional numerical hydrodynamics algorithms followed by a description of the proposed method and how it may address several of these longstanding issues. We give a theoretical overview of the proposed MFEM algorithm as well as a summary of the coding additions and modifications that were made to add this capability to the ARES code. We present results obtained with the new method on a set of canonical hydrodynamics test problems and demonstrate significant improvement in comparison to results obtained with traditional methods. We conclude with a summary of the issues still at hand and motivate the need for continued research to develop the proposed method into maturity.
High Efficiency Hydrodynamic DNA Fragmentation in a Bubbling System.
Li, Lanhui; Jin, Mingliang; Sun, Chenglong; Wang, Xiaoxue; Xie, Shuting; Zhou, Guofu; van den Berg, Albert; Eijkel, Jan C T; Shui, Lingling
2017-01-18
DNA fragmentation down to a precise fragment size is important for biomedical applications, disease determination, gene therapy and shotgun sequencing. In this work, a cheap, easy to operate and high efficiency DNA fragmentation method is demonstrated based on hydrodynamic shearing in a bubbling system. We expect that hydrodynamic forces generated during the bubbling process shear the DNA molecules, extending and breaking them at the points where shearing forces are larger than the strength of the phosphate backbone. Factors of applied pressure, bubbling time and temperature have been investigated. Genomic DNA could be fragmented down to controllable 1-10 Kbp fragment lengths with a yield of 75.30-91.60%. We demonstrate that the ends of the genomic DNAs generated from hydrodynamic shearing can be ligated by T4 ligase and the fragmented DNAs can be used as templates for polymerase chain reaction. Therefore, in the bubbling system, DNAs could be hydrodynamically sheared to achieve smaller pieces in dsDNAs available for further processes. It could potentially serve as a DNA sample pretreatment technique in the future.
Compatible, energy and symmetry preserving 2D Lagrangian hydrodynamics in rz-cylindrical coordinates
Shashkov, Mikhail; Wendroff, Burton; Burton, Donald; Barlow, A; Hongbin, Guo
2009-01-01
We present a new discretization for 2D Lagrangian hydrodynamics in rz geometry (cylindrical coordinates) that is compatible, energy conserving and symmetry preserving. We describe discretization of the basic Lagrangian hydrodynamics equations.
A microfluidic-based hydrodynamic trap for single particles.
Johnson-Chavarria, Eric M; Tanyeri, Melikhan; Schroeder, Charles M
2011-01-21
The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science. Methods for particle trapping based on optical, magnetic, electrokinetic, and acoustic techniques have led to major advancements in physics and biology ranging from the molecular to cellular level. In this article, we introduce a new microfluidic-based technique for particle trapping and manipulation based solely on hydrodynamic fluid flow. Using this method, we demonstrate trapping of micro- and nano-scale particles in aqueous solutions for long time scales. The hydrodynamic trap consists of an integrated microfluidic device with a cross-slot channel geometry where two opposing laminar streams converge, thereby generating a planar extensional flow with a fluid stagnation point (zero-velocity point). In this device, particles are confined at the trap center by active control of the flow field to maintain particle position at the fluid stagnation point. In this manner, particles are effectively trapped in free solution using a feedback control algorithm implemented with a custom-built LabVIEW code. The control algorithm consists of image acquisition for a particle in the microfluidic device, followed by particle tracking, determination of particle centroid position, and active adjustment of fluid flow by regulating the pressure applied to an on-chip pneumatic valve using a pressure regulator. In this way, the on-chip dynamic metering valve functions to regulate the relative flow rates in the outlet channels, thereby enabling fine-scale control of stagnation point position and particle trapping. The microfluidic-based hydrodynamic trap exhibits several advantages as a method for particle trapping. Hydrodynamic trapping is possible for any arbitrary particle without specific requirements on the physical or chemical properties of the trapped object. In addition, hydrodynamic trapping enables confinement of a "single" target object in
Event-by-event hydrodynamics: A better tool to study the Quark-Gluon plasma
Grassi, Frederique
2013-03-25
Hydrodynamics has been established as a good tool to describe many data from relativistic heavyion collisions performed at RHIC and LHC. More recently, it has become clear that it is necessary to use event-by-event hydrodynamics (i.e. describe each collision individually using hydrodynamics), an approach first developed in Brazil. In this paper, I review which data require the use of event-by-event hydrodynamics and what more we may learn on the Quark-Gluon Plasma with this.
The unreasonable effectiveness of hydrodynamics in heavy ion collisions
NASA Astrophysics Data System (ADS)
Noronha-Hostler, Jacquelyn; Noronha, Jorge; Gyulassy, Miklos
2016-12-01
Event-by-event hydrodynamic simulations of AA and pA collisions involve initial energy densities with large spatial gradients. This is associated with the presence of large Knudsen numbers (Kn ≈ 1) at early times, which may lead one to question the validity of the hydrodynamic approach in these rapidly evolving, largely inhomogeneous systems. A new procedure to smooth out the initial energy densities is employed to show that the initial spatial eccentricities, εn, are remarkably robust with respect to variations in the underlying scale of initial energy density spatial gradients, λ. For √{sNN} = 2.76 TeV LHC initial conditions generated by the MCKLN code, εn (across centralities) remains nearly constant if the fluctuation scale varies by an order of magnitude, i.e., when λ varies from 0.1 to 1 fm. Given that the local Knudsen number Kn ≈ 1 / λ, the robustness of the initial eccentricities with respect to changes in the fluctuation scale suggests that the vn's cannot be used to distinguish between events with large Kn from events where Kn is in the hydrodynamic regime. We use the 2+1 Lagrangian hydrodynamic code v-USPhydro to show that this is indeed the case: anisotropic flow coefficients computed within event-by-event viscous hydrodynamics are only sensitive to long wavelength scales of order 1 /ΛQCD ≈ 1 fm and are incredibly robust with respect to variations in the initial local Knudsen number. This robustness can be used to justify the somewhat unreasonable effectiveness of the nearly perfect fluid paradigm in heavy ion collisions.
Hydrodynamic Regimes Affect Coral Reef Resilience to Ocean Acidification
NASA Astrophysics Data System (ADS)
Teneva, L. T.; Dunbar, R. B.; Koseff, J. R.; Fleischfresser, J. D.; Koweek, D.
2013-05-01
Caribbean reefs hold tremendous value as sources of food, income, coastal protection, in addition to their cultural significance. Recently, studies showed that Caribbean reef growth has been surpassed in places by excessive rates of erosion due to climate change. The rates of coral reef response to ocean pH changes and warming and the implications for ecosystem resilience remain largely unknown. One way to investigate the potential structural resilience of reefs to climate change is to measure the physical oceanographic conditions in the area. Determining the hydrodynamic regimes and residence time of water in a particular reef environment is crucial to understanding the rates of future warming and acidification a reef site would experience. Our work on Pacific Islands' hydrodynamics - Central Equatorial Pacific, Great Barrier Reef, and Western Pacific -- would be of interest to Caribbean physical oceanographers and coral reef scientists. We use a combination of Acoustic Doppler Current Profilers, Acoustic Doppler Velocimeters, temperature and salinity sensors, and pressure sensors to characterize reef hydrodynamic regimes. Our work indicates that shallower, more protected reef habitats are characterized by longer residence times, their biological signals are strongly tidally modulated, essentially subjecting such habitats to higher rates of warming and acidification in the future. Reef crest environments and fore reef habitats, on the other hand, are well-mixed with open-ocean water. The hydrodynamic regimes there condition such reef sites to more attenuated temperature and pH ranges, conditions more typical of the open ocean. Our work suggests that investigating the geomorphology and resulting localized hydrodynamics in a reef area can provide insights into the relative rates at which a reef could resist or succumb to impacts of ocean acidification. Such information for different reef islands, in the Pacific or Caribbean basins, could provide helpful insights
Warm dense mater: another application for pulsed power hydrodynamics
Reinovsky, Robert Emil
2009-01-01
Pulsed Power Hydrodynamics (PPH) is an application of low-impedance pulsed power, and high magnetic field technology to the study of advanced hydrodynamic problems, instabilities, turbulence, and material properties. PPH can potentially be applied to the study of the properties of warm dense matter (WDM) as well. Exploration of the properties of warm dense matter such as equation of state, viscosity, conductivity is an emerging area of study focused on the behavior of matter at density near solid density (from 10% of solid density to slightly above solid density) and modest temperatures ({approx}1-10 eV). Conditions characteristic of WDM are difficult to obtain, and even more difficult to diagnose. One approach to producing WDM uses laser or particle beam heating of very small quantities of matter on timescales short compared to the subsequent hydrodynamic expansion timescales (isochoric heating) and a vigorous community of researchers are applying these techniques. Pulsed power hydrodynamic techniques, such as large convergence liner compression of a large volume, modest density, low temperature plasma to densities approaching solid density or through multiple shock compression and heating of normal density material between a massive, high density, energetic liner and a high density central 'anvil' are possible ways to reach relevant conditions. Another avenue to WDM conditions is through the explosion and subsequent expansion of a conductor (wire) against a high pressure (density) gas background (isobaric expansion) techniques. However, both techniques demand substantial energy, proper power conditioning and delivery, and an understanding of the hydrodynamic and instability processes that limit each technique. In this paper we will examine the challenges to pulsed power technology and to pulsed power systems presented by the opportunity to explore this interesting region of parameter space.
Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-28
... Energy Regulatory Commission Hydrodynamics, Inc.; Notice of Preliminary Permit Application Accepted for..., 2010, Hydrodynamics, Inc. filed an application for a preliminary permit, pursuant to section 4(f) of... project is 1.7 gigawatt hours. Applicant Contact: Jason M. Cohn, Project Engineer, Hydrodynamics,...
Progressive Multifocal Leukoencephalopathy
... clumsiness; progressive weakness; and visual, speech, and sometimes personality changes. The progression of deficits leads to life- ... clumsiness; progressive weakness; and visual, speech, and sometimes personality changes. The progression of deficits leads to life- ...
Hydrodynamic Stability of Liquid-Propellant Combustion: Landau's Problem Revisited
NASA Technical Reports Server (NTRS)
Margolis, S. B.
2001-01-01
Hydrodynamic, or Landau, instability in combustion is typically associated with the onset of wrinkling of a flame surface, corresponding to the formation of steady cellular structures as the stability threshold is crossed. As its name suggests, it stems from hydrodynamic effects connected with thermal expansion across the reaction region. In the context of liquid-propellant combustion, the classical models that originally predicted this phenomenon have been extended to include the important effects that arise from a dynamic dependence of the burning rate on the local pressure and temperature fields. Thus, the onset of Landau instability has now been shown to occur for sufficiently small negative values of the pressure sensitivity of the burning rate, significantly generalizing previous classical results for this problem that assumed a constant normal burning rate. It has also been shown that the onset of instability occurs for decreasing values of the disturbance wave number as the gravitational-acceleration parameter decreases. Consequently, in an appropriate weak-gravity limit, Landau instability becomes a long-wave phenomena associated with the formation of large cells on the liquid-propellant surface. Additionally, a pulsating form of hydrodynamic instability has been shown to occur as well, corresponding to the onset of temporal oscillations in the location of the liquid/gas interface. This instability occurs for sufficiently large negative values of the pressure sensitivity, and is enhanced by increasing values of the burning-rate temperature sensitivity. It is further shown that for sufficiently small values of this parameter, there exists a stable range of pressure sensitivities for steady, planar burning such that the classical cellular form of hydrodynamic instability and the more recent pulsating form of hydrodynamic instability can each occur as the corresponding stability threshold is crossed. For larger thermal sensitivities, however, the pulsating
Multi-dimensional hydrodynamics of core-collapse supernovae
NASA Astrophysics Data System (ADS)
Murphy, Jeremiah W.
Core-collapse supernovae are some of the most energetic events in the Universe, they herald the birth of neutron stars and black holes, are a major site for nucleosynthesis, influence galactic hydrodynamics, and trigger further star formation. As such, it is important to understand the mechanism of explosion. Moreover, observations imply that asymmetries are, in the least, a feature of the mechanism, and theory suggests that multi-dimensional hydrodynamics may be crucial for successful explosions. In this dissertation, we present theoretical investigations into the multi-dimensional nature of the supernova mechanism. It had been suggested that nuclear reactions might excite non-radial g-modes (the [straight epsilon]-mechanism) in the cores of progenitors, leading to asymmetric explosions. We calculate the eigenmodes for a large suite of progenitors including excitation by nuclear reactions and damping by neutrino and acoustic losses. Without exception, we find unstable g-modes for each progenitor. However, the timescales for growth are at least an order of magnitude longer than the time until collapse. Thus, the [straight epsilon]- mechanism does not provide appreciable amplification of non-radial modes before the core undergoes collapse. Regardless, neutrino-driven convection, the standing accretion shock instability, and other instabilities during the explosion provide ample asymmetry. To adequately simulate these, we have developed a new hydrodynamics code, BETHE-hydro that uses the Arbitrary Lagrangian-Eulerian (ALE) approach, includes rotational terms, solves Poisson's equation for gravity on arbitrary grids, and conserves energy and momentum in its basic implementation. By using time-dependent arbitrary grids that can adapt to the numerical challenges of the problem, this code offers unique flexibility in simulating astrophysical phenomena. Finally, we use BETHE-hydro to investigate the conditions and criteria for supernova explosions by the neutrino
LANL Q2 2016 Quarterly Progress Report. Science Campaign and ICF
Douglas, Melissa Rae
2016-04-07
This progress report includes highlights for the Science Campaign and ICF about Advanced Certification and Assessment Methodologies, Implosion Hydrodynamics (C-1, SCE), Materials and Nuclear Science (C-1, C-2), Capabilities for Nuclear Intelligence, and High Energy Density Science (C-1, C-4, C-10). Upcoming meetings, briefings, and experiments are then listed for April and May.
NASA Astrophysics Data System (ADS)
Liénard, Jean; Lynn, Kendra; Strigul, Nikolay; Norris, Benjamin K.; Gatziolis, Demetrios; Mullarney, Julia C.; Bryan, Karin, R.; Henderson, Stephen M.
2016-09-01
Aquatic vegetation can shelter coastlines from energetic waves and tidal currents, sometimes enabling accretion of fine sediments. Simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry. However, field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements. Building on recent progress in photogrammetry and computer vision, we present a method for reconstructing three-dimensional canopy geometry. The method was used to survey a dense canopy of aerial mangrove roots, called pneumatophores, in Vietnam's Mekong River Delta. Photogrammetric estimation of geometry required 1) taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats, 2) computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3D point cloud, and 3) extracting pneumatophore locations and diameters from the point cloud data. Step 3) was accomplished by a new 'sector-slice' algorithm, yielding geometric parameters every 5 mm along a vertical profile. Photogrammetric analysis was compared with manual caliper measurements. In all 5 quadrats considered, agreement was found between manual and photogrammetric estimates of stem number, and of number × mean diameter, which is a key parameter appearing in hydrodynamic models. In two quadrats, pneumatophores were encrusted with numerous barnacles, generating a complex geometry not resolved by hand measurements. In remaining cases, moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found. By substantially reducing measurement time in the field while capturing in greater detail the 3D structure, photogrammetry has potential to improve input to hydrodynamic models, particularly for simulations of flow through large-scale, heterogenous canopies.
Metal of cavitation erosion of a hydrodynamic reactor
NASA Astrophysics Data System (ADS)
Zakirzakov, A. G.; Brand, A. E.; Petryakov, V. A.; Gordievskaya, E. F.
2017-02-01
Cavitation erosion is a major cause of the petroleum equipment hydraulic erosion, which leads to the metal weight loss of the equipment and its breakdown, which can be followed by the full stop of the plant or company work. The probability of the metal weight loss and equipment failure can be reduced by the use of special protective coatings or rivets, made of the sacrificial metals, the use of which significantly increases the service life and the production equipment reliability. The article investigates the cavitation erosion effect, occurred under the condition of the advanced hydrodynamic cavitation on the hydrodynamic cavitation reactor. This article presents the results of the experiments and recommendations for increasing the operational resource.
3D Kinematics and Hydrodynamic Analysis of Freely Swimming Cetacean
NASA Astrophysics Data System (ADS)
Ren, Yan; Sheinberg, Dustin; Liu, Geng; Dong, Haibo; Fish, Frank; Javed, Joveria
2015-11-01
It's widely thought that flexibility and the ability to control flexibility are crucial elements in determining the performance of animal swimming. However, there is a lack of quantification of both span-wise and chord-wise deformation of Cetacean's flukes and associated hydrodynamic performance during actively swimming. To fill this gap, we examined the motion and flexure of both dolphin fluke and orca fluke in steady swimming using a combined experimental and computational approach. It is found that the fluke surface morphing can effectively modulate the flow structures and influence the propulsive performance. Findings from this work are fundamental for understanding key kinematic features of effective Cetacean propulsors, and for quantifying the hydrodynamic force production that naturally occurs during different types of swimming. This work is supported by ONR MURI N00014-14-1-0533 and NSF CBET-1313217.
Decay of hydrodynamic modes in dilute Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Gust, Erich; Reichl, Linda
2015-03-01
We present the results of Bogoliubov mean field theory applied to the hydrodynamic modes in a dilute Bose-Einstein condensate. The condensate has six hydrodynamic modes, two of which are decaying shear modes related to the viscosity, and two pairs pairs of sound modes which undergo an avoided crossing as the equilibrium temperature is varied. The two pairs of sound modes decay at very different rates, except in the neighborhood of the avoided crossing, where the identity of the longest-lived mode switches. The predicted speed and lifetime of the longest-lived sound mode are consistent with recent experimental observations on sound in an 87Rb Bose-Einstein condensate. The strong depedence of the decay rates on temperature implies a possible new method for determining the temperature of Bose-Einstein condensates. The authors wish to thank the Robert A. Welch Foundation Grant No. F-1051 for support of this work.
Simulation of Tailrace Hydrodynamics Using Computational Fluid Dynamics Models
Cook, Christopher B.; Richmond, Marshall C.
2001-05-01
This report investigates the feasibility of using computational fluid dynamics (CFD) tools to investigate hydrodynamic flow fields surrounding the tailrace zone below large hydraulic structures. Previous and ongoing studies using CFD tools to simulate gradually varied flow with multiple constituents and forebay/intake hydrodynamics have shown that CFD tools can provide valuable information for hydraulic and biological evaluation of fish passage near hydraulic structures. These studies however are incapable of simulating the rapidly varying flow fields that involving breakup of the free-surface, such as those through and below high flow outfalls and spillways. Although the use of CFD tools for these types of flow are still an active area of research, initial applications discussed in this report show that these tools are capable of simulating the primary features of these highly transient flow fields.
Hydrodynamics in adaptive resolution particle simulations: Multiparticle collision dynamics
Alekseeva, Uliana; Winkler, Roland G.; Sutmann, Godehard
2016-06-01
A new adaptive resolution technique for particle-based multi-level simulations of fluids is presented. In the approach, the representation of fluid and solvent particles is changed on the fly between an atomistic and a coarse-grained description. The present approach is based on a hybrid coupling of the multiparticle collision dynamics (MPC) method and molecular dynamics (MD), thereby coupling stochastic and deterministic particle-based methods. Hydrodynamics is examined by calculating velocity and current correlation functions for various mixed and coupled systems. We demonstrate that hydrodynamic properties of the mixed fluid are conserved by a suitable coupling of the two particle methods, and that the simulation results agree well with theoretical expectations.
Low torque hydrodynamic lip geometry for rotary seals
Dietle, Lannie L.; Schroeder, John E.
2015-07-21
A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.
Hydrodynamic interactions of cilia on a spherical body
NASA Astrophysics Data System (ADS)
Nasouri, Babak; Elfring, Gwynn J.
2015-11-01
The emergence of metachronal waves in ciliated microorganisms can arise solely from the hydrodynamic interactions between the cilia. For a chain of cilia attached to a flat ciliate, it was observed that fluid forces can lead the system to form a metachronal wave. However, several microorganisms such as paramecium and volvox possess a curved shaped ciliate body. To understand the effect of this geometry on the formation of metachronal waves, we evaluate the hydrodynamic interactions of cilia near a large spherical body. Using a minimal model, we show that for a chain of cilia around the sphere, the embedded periodicity in the geometry leads the system to synchronize. We also report an emergent wave-like behavior when an asymmetry is introduced to the system.
Neutrino signature of supernova hydrodynamical instabilities in three dimensions.
Tamborra, Irene; Hanke, Florian; Müller, Bernhard; Janka, Hans-Thomas; Raffelt, Georg
2013-09-20
The first full-scale three-dimensional core-collapse supernova (SN) simulations with sophisticated neutrino transport show pronounced effects of the standing accretion shock instability (SASI) for two high-mass progenitors (20 and 27 M([Symbol: see text])). In a low-mass progenitor (11.2 M([Symbol: see text])), large-scale convection is the dominant nonradial hydrodynamic instability in the postshock accretion layer. The SASI-associated modulation of the neutrino signal (80 Hz in our two examples) will be clearly detectable in IceCube or the future Hyper-Kamiokande detector, depending on progenitor properties, distance, and observer location relative to the main SASI sloshing direction. The neutrino signal from the next galactic SN can, therefore, diagnose the nature of the hydrodynamic instability.
Interplay of Laser-Plasma Interactions and Inertial Fusion Hydrodynamics
NASA Astrophysics Data System (ADS)
Strozzi, D. J.; Bailey, D. S.; Michel, P.; Divol, L.; Sepke, S. M.; Kerbel, G. D.; Thomas, C. A.; Ralph, J. E.; Moody, J. D.; Schneider, M. B.
2017-01-01
The effects of laser-plasma interactions (LPI) on the dynamics of inertial confinement fusion hohlraums are investigated via a new approach that self-consistently couples reduced LPI models into radiation-hydrodynamics numerical codes. The interplay between hydrodynamics and LPI—specifically stimulated Raman scatter and crossed-beam energy transfer (CBET)—mostly occurs via momentum and energy deposition into Langmuir and ion acoustic waves. This spatially redistributes energy coupling to the target, which affects the background plasma conditions and thus, modifies laser propagation. This model shows reduced CBET and significant laser energy depletion by Langmuir waves, which reduce the discrepancy between modeling and data from hohlraum experiments on wall x-ray emission and capsule implosion shape.
A modified Henyey method for computing radiative transfer hydrodynamics
NASA Technical Reports Server (NTRS)
Karp, A. H.
1975-01-01
The implicit hydrodynamic code of Kutter and Sparks (1972), which is limited to optically thick regions and employs the diffusion approximation for radiative transfer, is modified to include radiative transfer effects in the optically thin regions of a model star. A modified Henyey method is used to include the solution of the radiative transfer equation in this implicit code, and the convergence properties of this method are proven. A comparison is made between two hydrodynamic models of a classical Cepheid with a 12-day period, one of which was computed with the diffusion approximation and the other with the modified Henyey method. It is found that the two models produce nearly identical light and velocity curves, but differ in the fact that the former never has temperature inversions in the atmosphere while the latter does when sufficiently strong shocks are present.
Angular-compliant hydrodynamic bearing performance under dynamic loads
NASA Astrophysics Data System (ADS)
Harnoy, A.; Rachoor, H.
1993-07-01
The study is focused on a dynamically loaded composite bearing, consisting of a hydrodynamic journal bearing inside the internal race of a rolling-element bearing. In this combination, the hydrodynamic bearing has an angular-compliant sleeve with a restricted freedom of rotation around its axis. Under static loads, the improvement is primarily in a significant reduction of friction and wear during the starting and stopping. Under periodical loads, our analysis shows that the performance depends on two dimensionless design parameters. Below particular critical values of these parameters, the results show a considerable improvement, demonstrated by a reduction of the maximum eccentricity. However, above the critical values, the bearing becomes unstable. These results indicate the significance of incorporating this computer assisted computation for each design.
Validating hydrodynamic growth in National Ignition Facility implosions
Peterson, J. L. Casey, D. T.; Hurricane, O. A.; Raman, K. S.; Robey, H. F.; Smalyuk, V. A.
2015-05-15
We present new hydrodynamic growth experiments at the National Ignition Facility, which extend previous measurements up to Legendre mode 160 and convergence ratio 4, continuing the growth factor dispersion curve comparison of the low foot and high foot pulses reported by Casey et al. [Phys. Rev. E 90, 011102(R) (2014)]. We show that the high foot pulse has lower growth factor and lower growth rate than the low foot pulse. Using novel on-capsule fiducial markers, we observe that mode 160 inverts sign (changes phase) for the high foot pulse, evidence of amplitude oscillations during the Richtmyer-Meshkov phase of a spherically convergent system. Post-shot simulations are consistent with the experimental measurements for all but the shortest wavelength perturbations, reinforcing the validity of radiation hydrodynamic simulations of ablation front growth in inertial confinement fusion capsules.
3D hydrodynamic focusing microfluidics for emerging sensing technologies.
Daniele, Michael A; Boyd, Darryl A; Mott, David R; Ligler, Frances S
2015-05-15
While the physics behind laminar flows has been studied for 200 years, understanding of how to use parallel flows to augment the capabilities of microfluidic systems has been a subject of study primarily over the last decade. The use of one flow to focus another within a microfluidic channel has graduated from a two-dimensional to a three-dimensional process and the design principles are only now becoming established. This review explores the underlying principles for hydrodynamic focusing in three dimensions (3D) using miscible fluids and the application of these principles for creation of biosensors, separation of cells and particles for sample manipulation, and fabrication of materials that could be used for biosensors. Where sufficient information is available, the practicality of devices implementing fluid flows directed in 3D is evaluated and the advantages and limitations of 3D hydrodynamic focusing for the particular application are highlighted.
Dynamic forces between bubbles and surfaces and hydrodynamic boundary conditions.
Manor, Ofer; Vakarelski, Ivan U; Stevens, Geoffrey W; Grieser, Franz; Dagastine, Raymond R; Chan, Derek Y C
2008-10-21
A bubble attached to the end of an atomic force microscope cantilever and driven toward or away from a flat mica surface across an aqueous film is used to characterize the dynamic force that arises from hydrodynamic drainage and electrical double layer interactions across the nanometer thick intervening aqueous film. The hydrodynamic response of the air/water interface can range from a classical fully immobile, no-slip surface in the presence of added surfactants to a partially mobile interface in an electrolyte solution without added surfactants. A model that includes the convection and diffusion of trace surface contaminants can account for the observed behavior presented. This model predicts quantitatively different interfacial dynamics to the Navier slip model that can also be used to fit dynamic force data with a post hoc choice of a slip length.
Hydrodynamic study of an internal airlift reactor for microalgae culture.
Rengel, Ana; Zoughaib, Assaad; Dron, Dominique; Clodic, Denis
2012-01-01
Internal airlift reactors are closed systems considered today for microalgae cultivation. Several works have studied their hydrodynamics but based on important solid concentrations, not with biomass concentrations usually found in microalgae cultures. In this study, an internal airlift reactor has been built and tested in order to clarify the hydrodynamics of this system, based on microalgae typical concentrations. A model is proposed taking into account the variation of air bubble velocity according to volumetric air flow rate injected into the system. A relationship between riser and downcomer gas holdups is established, which varied slightly with solids concentrations. The repartition of solids along the reactor resulted to be homogenous for the range of concentrations and volumetric air flow rate studied here. Liquid velocities increase with volumetric air flow rate, and they vary slightly when solids are added to the system. Finally, liquid circulation time found in each section of the reactor is in concordance with those employed in microalgae culture.
Key role of hydrodynamic interactions in colloidal gelation.
Furukawa, Akira; Tanaka, Hajime
2010-06-18
Colloidal gelation is caused by the formation of a percolated network of colloidal particles suspended in a liquid. Thus far the major transport process leading to gelation has been believed to be the brownian diffusion of particles. Contrary to this common belief, we reveal by numerical simulations that many-body hydrodynamic interactions between colloidal particles also play an essential role in gelation: They significantly promote gelation, or lower the colloid volume fraction threshold for percolation, as compared to their absence. We find that the incompressible nature of a liquid component and the resulting self-organization of hydrodynamic flow with a transverse (rotational) character are responsible for this enhancement of network-forming ability.
Hydrodynamic simulations of microjetting from shock-loaded grooves
NASA Astrophysics Data System (ADS)
Roland, C.; de Rességuier, T.; Sollier, A.; Lescoute, E.; Soulard, L.; Loison, D.
2017-01-01
The interaction of a shock wave with a free surface which has geometrical defects, such as cavities or grooves, may lead to the ejection of micrometric debris at velocities of km/s. This process can be involved in many applications, like pyrotechnics or industrial safety. Recent laser shock experiments reported elsewhere in this conference have provided some insight into jet formation as well as jet tip velocities for various groove angles and shock pressures. Here, we present hydrodynamic simulations of these experiments, in both 2D and 3D geometries, using both finite element method and smoothed particle hydrodynamics. Numerical results are compared to several theoretical predictions including the Richtmyer-Meshkov instabilities. The role of the elastic-plastic behavior on jet formation is illustrated. Finally, the possibility to simulate the late stage of jet expansion and fragmentation is explored, to evaluate the mass distribution of the ejecta and their ballistic properties, still essentially unknown in the experiments.
Hydrodynamic interaction induced mechanical properties of SGF reinforced polyethersulfone
NASA Astrophysics Data System (ADS)
Munirathnamma, L. M.; Ningaraju, S.; Kumar, K. V. Aneesh; Ravikumar, H. B.
2016-05-01
In order to explore the effect of short glass fiber (SGF) reinforcement on the mechanical properties of Polyethersulfone (PES), short glass fibers of different proportion (10 - 40 wt %) are reinforced into PES matrix. The free volume distribution of SGFR-PES composites derived from CONTIN-PALS2 program exhibits the narrow full width at half maximum (FWHM). This is attributed to the improved adhesion resulted by the hydrodynamic interaction between the polymeric chains of PES matrix and SGF. The hydrodynamic interaction parameter (h) decreases as a function of SGF wt% and becomes more negative for 40 wt% SGFR-PES composites suggest the generation of excess friction at the interface. This improves the adhesion between the polymeric chains of PES matrix and SGF and hence the mechanical strength of the SGFR-PES composites.
A hydrodynamic interpretation of crisis in sickle cell anemia.
Cima, L G; Discher, D E; Tong, J; Williams, M C
1994-01-01
The occurrence of crisis events in patients with sickle cell disease is associated with an increase in blood plasma viscosity, the hydrodynamic consequences of which are examined here. A mathematical model of the flow of sickle cells in capillaries predicts that for moderate increases in plasma viscosity, a regime of multivalued solutions for blood velocities is encountered, and the likely physical response is a precipitous drop to the lowest velocity solution. This behavior results from the coupling of the hydrodynamics with sickle erythrocyte rheology and oxygen transport to the surrounding tissue; no such catastrophe is predicted for normal erythrocytes. The type of velocity changes predicted by the model strongly suggest that plasma viscosity changes may play an important role in initiating or exacerbating crisis.
Quasiparticle second-order viscous hydrodynamics from kinetic theory
NASA Astrophysics Data System (ADS)
Tinti, Leonardo; Jaiswal, Amaresh; Ryblewski, Radoslaw
2017-03-01
We present the derivation of second-order relativistic viscous hydrodynamics from an effective Boltzmann equation for a system consisting of quasiparticles of a single species. We consider temperature-dependent masses of the quasiparticles and devise a thermodynamically consistent framework to formulate second-order evolution equations for shear and bulk viscous pressure corrections. The main advantage of this formulation is that one can consistently implement a realistic equation of state of the medium within the framework of kinetic theory. Specializing to the case of a one-dimensional purely longitudinal boost-invariant expansion, we study the effect of this new formulation on the viscous hydrodynamic evolution of strongly interacting matter formed in relativistic heavy-ion collisions.
On the Hydrodynamic Function of Sharkskin: A Computational Investigation
NASA Astrophysics Data System (ADS)
Boomsma, Aaron; Sotiropoulos, Fotis
2014-11-01
Denticles (placoid scales) are small structures that cover the epidermis of some sharks. The hydrodynamic function of denticles is unclear. Because they resemble riblets, they have been thought to passively reduce skin-friction-for which there is some experimental evidence. Others have experimentally shown that denticles increase skin-friction and have hypothesized that denticles act as vortex generators to delay separation. To help clarify their function, we use high-resolution large eddy and direct numerical simulations, with an immersed boundary method, to simulate flow patterns past and calculate the drag force on Mako Short Fin denticles. Simulations are carried out for the denticles placed in a canonical turbulent boundary layer as well as in the vicinity of a separation bubble. The computed results elucidate the three-dimensional structure of the flow around denticles and provide insights into the hydrodynamic function of sharkskin.
Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling
Hou, Yan-Hua; Yu, Zhenhua
2015-01-01
Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations. PMID:26483090
Experimental Testbed for the Study of Hydrodynamic Issues in Supernovae
Robey, H F; Kane, J O; Remington, B A; Drake, R P; Hurricane, O A; Louis, H; Wallace, R J; Knauer, J; Keiter, P; Arnett, D
2000-10-09
More than a decade after the explosion of SN 1987A, unresolved discrepancies still remain in attempts to numerically simulate the mixing processes initiated by the passage of a very strong shock through the layered structure of the progenitor star. Numerically computed velocities of the radioactive {sup 56}Ni and {sup 56}CO, produced by shock-induced explosive burning within the silicon layer for example, are still more than 50% too low as compared with the measured velocities. In order to resolve such discrepancies between observation and simulation, an experimental testbed has been designed on the Omega Laser for the study of hydrodynamic issues of importance to supernovae (SNe). In this paper, we present results from a series of scaled laboratory experiments designed to isolate and explore several issues in the hydrodynamics of SN explosions. The results of the experiments are compared with numerical simulations and are generally found to be in reasonable agreement.
REVIEWS OF TOPICAL PROBLEMS: Negative energy waves in hydrodynamics
NASA Astrophysics Data System (ADS)
Ostrovskiĭ, L. A.; Rybak, Samuil A.; Tsimring, L. Sh
1986-11-01
The utility of the concept of negative energy waves (NEW) in hydrodynamics is discussed. Examples are given of the excitation of waves by flow past elastic membranes, and of the amplification and generation of capillary-gravity and internal waves in liquids in the presence of vertically inhomogeneous flows. The concepts of "linear" and "nonlinear" energy are introduced, and it is shown that energy defined as the first integral of the equations of motion linearized against the flow background can be negative, whereas the inclusion of all the quadratic terms in the expression for the energy can give a positive value. Nonlinear processes associated with NEW are also discussed, as is the radiation instability of oscillators in hydrodynamics. The review is largely based on the authors' own work.
Hydrodynamic effects in the atmosphere of variable stars
NASA Technical Reports Server (NTRS)
Davis, C. G., Jr.; Bunker, S. S.
1975-01-01
Numerical models of variable stars are established, using a nonlinear radiative transfer coupled hydrodynamics code. The variable Eddington method of radiative transfer is used. Comparisons are for models of W Virginis, beta Doradus, and eta Aquilae. From these models it appears that shocks are formed in the atmospheres of classical Cepheids as well as W Virginis stars. In classical Cepheids, with periods from 7 to 10 days, the bumps occurring in the light and velocity curves appear as the result of a compression wave that reflects from the star's center. At the head of the outward going compression wave, shocks form in the atmosphere. Comparisons between the hydrodynamic motions in W Virginis and classical Cepheids are made. The strong shocks in W Virginis do not penetrate into the interior as do the compression waves formed in classical Cepheids. The shocks formed in W Virginis stars cause emission lines, while in classical Cepheids the shocks are weaker.
General relativistic magneto-hydrodynamics with the Einstein Toolkit
NASA Astrophysics Data System (ADS)
Moesta, Philipp; Mundim, Bruno; Faber, Joshua; Noble, Scott; Bode, Tanja; Haas, Roland; Loeffler, Frank; Ott, Christian; Reisswig, Christian; Schnetter, Erik
2013-04-01
The Einstein Toolkit Consortium is developing and supporting open software for relativistic astrophysics. Its aim is to provide the core computational tools that can enable new science, broaden our community, facilitate interdisciplinary research and take advantage of petascale computers and advanced cyberinfrastructure. The Einstein Toolkit currently consists of an open set of over 100 modules for the Cactus framework, primarily for computational relativity along with associated tools for simulation management and visualization. The toolkit includes solvers for vacuum spacetimes as well as relativistic magneto-hydrodynamics. This talk will present the current capabilities of the Einstein Toolkit with a particular focus on recent improvements made to the general relativistic magneto-hydrodynamics modeling and will point to information how to leverage it for future research.
Hydrodynamic properties of fin whale flippers predict maximum rolling performance.
Segre, Paolo S; Cade, David E; Fish, Frank E; Potvin, Jean; Allen, Ann N; Calambokidis, John; Friedlaender, Ari S; Goldbogen, Jeremy A
2016-11-01
Maneuverability is one of the most important and least understood aspects of animal locomotion. The hydrofoil-like flippers of cetaceans are thought to function as control surfaces that effect maneuvers, but quantitative tests of this hypothesis have been lacking. Here, we constructed a simple hydrodynamic model to predict the longitudinal-axis roll performance of fin whales, and we tested its predictions against kinematic data recorded by on-board movement sensors from 27 free-swimming fin whales. We found that for a given swimming speed and roll excursion, the roll velocity of fin whales calculated from our field data agrees well with that predicted by our hydrodynamic model. Although fluke and body torsion may further influence performance, our results indicate that lift generated by the flippers is sufficient to drive most of the longitudinal-axis rolls used by fin whales for feeding and maneuvering.
Hydrodynamic instabilities in beryllium targets for the National Ignition Facility
Yi, S. A. Simakov, A. N.; Wilson, D. C.; Olson, R. E.; Kline, J. L.; Batha, S. H.; Clark, D. S.; Hammel, B. A.; Milovich, J. L.; Salmonson, J. D.; Kozioziemski, B. J.
2014-09-15
Beryllium ablators offer higher ablation velocity, rate, and pressure than their carbon-based counterparts, with the potential to increase the probability of achieving ignition at the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. We present here a detailed hydrodynamic stability analysis of low (NIF Revision 6.1) and high adiabat NIF beryllium target designs. Our targets are optimized to fully utilize the advantages of beryllium in order to suppress the growth of hydrodynamic instabilities. This results in an implosion that resists breakup of the capsule, and simultaneously minimizes the amount of ablator material mixed into the fuel. We quantify the improvement in stability of beryllium targets relative to plastic ones, and show that a low adiabat beryllium capsule can be at least as stable at the ablation front as a high adiabat plastic target.
Development and Implementation of Radiation-Hydrodynamics Verification Test Problems
Marcath, Matthew J.; Wang, Matthew Y.; Ramsey, Scott D.
2012-08-22
Analytic solutions to the radiation-hydrodynamic equations are useful for verifying any large-scale numerical simulation software that solves the same set of equations. The one-dimensional, spherically symmetric Coggeshall No.9 and No.11 analytic solutions, cell-averaged over a uniform-grid have been developed to analyze the corresponding solutions from the Los Alamos National Laboratory Eulerian Applications Project radiation-hydrodynamics code xRAGE. These Coggeshall solutions have been shown to be independent of heat conduction, providing a unique opportunity for comparison with xRAGE solutions with and without the heat conduction module. Solution convergence was analyzed based on radial step size. Since no shocks are involved in either problem and the solutions are smooth, second-order convergence was expected for both cases. The global L1 errors were used to estimate the convergence rates with and without the heat conduction module implemented.
Electrophoresis of semiflexible heteropolymers and the ``hydrodynamic Kuhn length''
NASA Astrophysics Data System (ADS)
Chubynsky, Mykyta V.; Slater, Gary W.
Semiflexible polymers, such as DNA, are rodlike for short lengths and coil-like for long lengths. For purely geometric properties, such as the end-to-end distance, the crossover between these two behaviors occurs when the polymer length is on the order of the Kuhn length. On the other hand, for the hydrodynamic friction coefficient it is easy to see by comparing the expressions for a rod and a coil that the crossover should occur at the polymer length, termed by us the hydrodynamic Kuhn length, which is larger than the ordinary Kuhn length by a logarithmic factor that can be quite significant. We show that for the problem of electrophoresis of a heteropolymer consisting of several blocks of (in general) different stiffnesses, both of these length scales can be important depending on the details of the problem.
Viscoelastic hydrodynamic interactions and anomalous CM diffusion in polymer melts
NASA Astrophysics Data System (ADS)
Meyer, Hendrik
We have recently discovered that anomalous center-of-mass (CM) diffusion occurring on intermediate time scales in polymer melts can be explained by the interplay of viscoelastic and hydrodynamic interactions (VHI). The theory has been solved for unentangled melts in 3D and 2D and excellent agreement between theory and simulation is found, also for alkanes with a force field optimized from neutron scattering. The physical mechanism considers that hydrodynamic interactions are not screened: they are time dependent because of increasing viscosity before the terminal relaxation time. The VHI are generally active in melts of any topology. They are most important at early times well before the terminal relaxation time and thus affect the nanosecond time range typically observable in dynamic neutron scattering experiments. We illustrate the effects with recent molecular dynamics simulations of linear, ring and star polymers. Work performed with A.N. Semenov and J. Farago.
Viscoelastic hydrodynamic interactions and anomalous CM diffusion in polymer melts
NASA Astrophysics Data System (ADS)
Meyer, Hendrik; Farago, Jean; Semenov, A. N.
2014-03-01
We have recently discovered that anomalous center-of-mass (CM) diffusion occurring on intermediate time scales in polymer melts can be explained by the interplay of viscoelastic and hydrodynamic interactions (VHI). The theory has been solved for unentangled melts in 3D and 2D and excellent agreement between theory and simulation is found. The physical mechanism considers that hydrodynamic interactions are time dependent because of increasing viscosity before the terminal relaxation time; it is generally active in melts of any topology. Surprisingly, the effects are relevant for both, momentum-conserving and Langevin dynamics and this presentation will focus on the differences: The commonly employed Langevin thermostat significantly changes the CM motion on short and intermediate time scales, but approaching the Rouse time, the melt behavior is close to momentum-conserving simulations. On the other hand, if momentum-conserving simulations are run in too small a simulation box, the result looks as if a Langevin thermostat was used.
Hydrodynamic interaction between rigid surfaces planing on water
NASA Astrophysics Data System (ADS)
Bari, Ghazi; Matveev, Konstantin
2016-11-01
This study addresses hydrodynamic interaction of multi-surface planing hulls in the linearized, inviscid, steady flow approximation. A potential-flow-based hydrodynamic sources are distributed on the water surface to model water flow around three-dimensional hulls at finite Froude numbers. The pressure distribution on the hull surfaces are calculated as a part of the solution, and then the lift force and center of pressure are determined. For validation, numerical results are compared with an available analytical solution, experimental results, and empirical correlation equations. Parametric calculations are carried out for different hull designs in variable speed regimes, hull aspect ratios, deadrise angles and hull spacings. Results are presented for the lift coefficient, drag components, lift-drag ratio, center of pressure, and some illustrations are given for the water surface elevations. Obtained results can assist naval architects in improving design of high speed marine vehicles.
Longitudinal hydrodynamics from event-by-event Landau initial conditions
Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Kenneth; Wong, Cheuk-Yin
2015-02-02
Here we investigate three-dimensional ideal hydrodynamic evolution, with Landau initial conditions, incorporating event-by-event variation with many events and transverse density inhomogeneities. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of θ (20%-30%) expected at freeze-out for most scenarios. Moreover, the deviation from boost invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, hydrodynamics where boost invariance holds at midrapidity is inadequate to extract transport coefficients of the quark-gluon plasma. We conclude by arguing that developing experimental probes of boost invariance is necessary, and suggest some promising directions in this regard.
Longitudinal hydrodynamics from event-by-event Landau initial conditions
Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; ...
2015-02-02
Here we investigate three-dimensional ideal hydrodynamic evolution, with Landau initial conditions, incorporating event-by-event variation with many events and transverse density inhomogeneities. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of θ (20%-30%) expected at freeze-out for most scenarios. Moreover, the deviation from boost invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, hydrodynamics where boost invariance holds at midrapidity ismore » inadequate to extract transport coefficients of the quark-gluon plasma. We conclude by arguing that developing experimental probes of boost invariance is necessary, and suggest some promising directions in this regard.« less
Load-Induced Hydrodynamic Lubrication of Porous Films.
Khosla, Tushar; Cremaldi, Joseph; Erickson, Jeffrey S; Pesika, Noshir S
2015-08-19
We present an exploratory study of the tribological properties and mechanisms of porous polymer surfaces under applied loads in aqueous media. We show how it is possible to change the lubrication regime from boundary lubrication to hydrodynamic lubrication even at relatively low shearing velocities by the addition of vertical pores to a compliant polymer. It is hypothesized that the compressed, pressurized liquid in the pores produces a repulsive hydrodynamic force as it extrudes from the pores. The presence of the fluid between two shearing surfaces results in low coefficients of friction (μ ≈ 0.31). The coefficient of friction is reduced further by using a boundary lubricant. The tribological properties are studied for a range of applied loads and shear velocities to demonstrate the potential applications of such materials in total joint replacement devices.
Hydrodynamic focusing of conducting fluids for conductivity-based biosensors.
Nasir, Mansoor; Ateya, Daniel A; Burk, Diana; Golden, Joel P; Ligler, Frances S
2010-02-15
Hydrodynamic focusing of a conducting fluid by a non-conducting fluid to form a constricted current path between two sensing electrodes is implemented in order to enhance the sensitivity of a 4-electrode conductance-based biosensor. The sensor has a simple two-inlet T-junction design and performs four-point conductivity measurements to detect particles immobilized between the sensing electrode pair. Computational simulations conducted in conjunction with experimental flow studies using confocal microscopy show that a flat profile for the focused layer is dependent on the Reynolds number for the chosen flow parameters. The results also indicate that a flat focused layer is desirable for both increased sensitivity as well as surface-binding efficiency. Proof of concept for conductance measurements in a hydrodynamically focused conducting fluid was demonstrated with entrapped magnetic beads.
Matching pre-equilibrium dynamics and viscous hydrodynamics
Martinez, Mauricio; Strickland, Michael
2010-02-15
We demonstrate how to match pre-equilibrium dynamics of a 0+1-dimensional quark-gluon plasma to second-order viscous hydrodynamical evolution. The matching allows us to specify the initial values of the energy density and shear tensor at the initial time of hydrodynamical evolution as a function of the lifetime of the pre-equilibrium period. We compare two models for pre-equilibrium quark-gluon plasma, longitudinal free streaming and collisionally broadened longitudinal expansion, and present analytic formulas that can be used to fix the necessary components of the energy-momentum tensor. The resulting dynamical models can be used to assess the effect of pre-equilibrium dynamics on quark-gluon plasma observables. Additionally, we investigate the dependence of entropy production on pre-equilibrium dynamics and discuss the limitations of the standard definitions of nonequilibrium entropy.
Hydrodynamical analysis of the effect of fish fins morphology
NASA Astrophysics Data System (ADS)
Azwadi Che Sidik, Nor; Yen, Tey Wah
2013-12-01
The previous works on the biomechanics of fishes focuses on the locomotion effect of the fish bodies. However, there is quite a insufficiency in unveiling the respective function of fins when the fishes pose statics and exposed to fluid flow. Accordingly, this paper's focus is to investigate the hydrodynamic effect of the fins configuration to the fluid flow of shark-shaped-inspired structure. The drag and lift coefficient is computed for different cases of fish fins addition and configuration. The k-epsilon turbulence model is deployed using finite volume method with the aid of commercial software ANSYS CFX. The finding will demystify some of the functions of the fish's fins in term of their contribution to the hydrodynamic flow around the fishes.
Hydrodynamic Self-Assembly of Topographical Patterns on Soft Materials
Kumar, Satish
2016-01-06
The objective of this project is to use theoretical tools to explore fundamentally new ways of creating and controlling surface topography on soft materials (e.g., polymeric liquids, gels, colloidal suspensions) that make use of principles from hydrodynamics and self-assembly. Surface topography is known to have a significant impact on the optical, adhesive, and wetting properties of materials, so improved fundamental understanding of how to create and control it will help enable the tailoring of these properties to desired specifications. Self-assembly is the spontaneous organization of an ordered structure, and hydrodynamics often plays an important role in the self-assembly of soft materials. This research supported through this project has led to the discovery of a number of novel phenomena that are described in published journal articles. In this way, the research significantly adds to the fundamental understanding of the topics investigated.
Microalgae Scatter off Solid Surfaces by Hydrodynamic and Contact Forces
NASA Astrophysics Data System (ADS)
Contino, Matteo; Lushi, Enkeleida; Tuval, Idan; Kantsler, Vasily; Polin, Marco
2015-12-01
Interactions between microorganisms and solid boundaries play an important role in biological processes, such as egg fertilization, biofilm formation, and soil colonization, where microswimmers move within a structured environment. Despite recent efforts to understand their origin, it is not clear whether these interactions can be understood as being fundamentally of hydrodynamic origin or hinging on the swimmer's direct contact with the obstacle. Using a combination of experiments and simulations, here we study in detail the interaction of the biflagellate green alga Chlamydomonas reinhardtii, widely used as a model puller microorganism, with convex obstacles, a geometry ideally suited to highlight the different roles of steric and hydrodynamic effects. Our results reveal that both kinds of forces are crucial for the correct description of the interaction of this class of flagellated microorganisms with boundaries.
A new approach to non-Abelian hydrodynamics
NASA Astrophysics Data System (ADS)
Fernández-Melgarejo, Jose J.; Rey, Soo-Jong; Surówka, Piotr
2017-02-01
We present a new approach to describe hydrodynamics carrying non-Abelian macroscopic degrees of freedom. Based on the Kaluza-Klein compactification of a higher-dimensional neutral dissipative fluid on a manifold of non-Abelian isometry, we obtain a four-dimensional colored dissipative fluid coupled to Yang-Mills gauge field. We derive transport coefficients of resulting colored fluid, which feature non-Abelian character of color charges. In particular, we obtain color-specific terms in the gradient expansions and response quantities such as the conductivity matrix and the chemical potentials. We argue that our Kaluza-Klein approach provides a robust description of non-Abelian hydrodynamics, and discuss some links between this system and quark-gluon plasma and fluid/gravity duality.
Differences between hydrodynamic and macromolecule induced clusters in microcapillary flow
NASA Astrophysics Data System (ADS)
Wagner, Christian; Claveria, Viviana; Aouane, Othmane; Coupier, Gwennou; Misbah, Chaouqi; Abkarian, Manouk
2015-03-01
Recent studies have been shown that despite the large shear rates, the presence of either fibrinogen or the synthetic polymer dextran leads to an enhanced formation of robust clusters of RBC in microcapillaries under flow conditions. The contribution of hydrodynamical interactions and interactions induced by the presence of macromolecules in the cluster formation has not been established. In order to elucidate this mechanism, we compare experimentally in microchannels under flow condition, the pure hydrodynamical cluster formation of RBCs and the cluster formation of RBCs in the presence of macromolecules inducing aggregation. The results reveal strong differences in the cluster morphology. Emphasizing on the case of clusters formed by two cells, the surface to surface interdistances between the cells in the different solutions shows a bimodal distribution. Numerical simulations based on the boundary integral method showed a good agreement with the experimental findings.
Non-linear hydrodynamical simulations of delta Scuti star pulsations
NASA Astrophysics Data System (ADS)
Templeton, M. R.; Guzik, J. A.; McNamara, B. J.
1998-12-01
We present the initial results of non-linear hydrodynamic simulations of the pulsation modes of delta Scuti stars. These models use the Ostlie and Cox (1993) Lagrangian hydrodynamic code, adapted to use the most recent OPAL (1996) opacities, the Stellingwerf (1974) periodic relaxation method of obtaining stable limit cycle pulsations, and time-dependent convection. Initial tests of first- and second-overtone pulsation models are consistent with the models of Bono, et al (1997) showing asymmetric lightcurves for first overtone rather than fundamental pulsations. Future modeling work will test several stellar models with varying masses, ages, metal and helium abundances and envelope abundance gradients. Ultimately, we hope to determine the role that abundances and, more specifically, helium abundance gradients in delta Scuti envelopes play in light curve shape. This work will be applied to a test sample of known radially-pulsating delta Scuti field stars and the newly-discovered delta Scuti/SX Phoenicis variables in the Galactic Bulge.
The hydrodynamics of galaxy formation on Kiloparsec scales
NASA Technical Reports Server (NTRS)
Norman, Michael L.; Anninos, Wenbo Yuan; Centrella, Joan
1993-01-01
Two dimensional numerical simulations of Zeldovich pancake fragmentation in a dark matter dominated universe were carried out to study the hydrodynamical and gravitational effects on the formation of structures such as protogalaxies. Preliminary results were given in Yuan, Centrella and, Norman (1991). Here we report a more exhaustive study to determine the sensitivity of protogalaxies to input parameters. The numerical code we used for the simulations combines the hydrodynamical code ZEUS-2D (Stone and Norman, 1992) which was modified to include the expansion of the universe and radiative cooling of the gas with a particle-mesh code which follows the motion of dark matter particles. The resulting hybrid code is able to handle highly nonuniform grids which we utilized to obtain a high resolution (much greater than 1 kpc) in the dense region of the pancake.
IUTAM Symposium on Hydrodynamic Diffusion of Suspended Particles
NASA Technical Reports Server (NTRS)
Davis, R. H.
1995-01-01
The focus of the symposium was on multiparticle hydrodynamic interactions which lead to fluctuating motion of the particles and resulting particle migration and dispersion or diffusion. Implications of these phenomena were described for sedimentation, fluidization, suspension flows, granular flows, and fiber suspensions. Computer simulation techniques as well as experimental techniques were described. Each session had an invited leadoff talk which overviewed the session topic as well as described the speaker's own related research. Ample time for discussion was included after each talk as well as at the end of each session. The symposium started with a keynote talk on the first evening on What is so puzzling about hydrodynamic diffusion?, which set the tone for the rest of the meeting by emphasizing both recent advances and unanswered issues.
Interplay of Laser-Plasma Interactions and Inertial Fusion Hydrodynamics
Strozzi, D. J.; Bailey, D. S.; Michel, P.; ...
2017-01-12
The effects of laser-plasma interactions (LPI) on the dynamics of inertial confinement fusion hohlraums are investigated in this work via a new approach that self-consistently couples reduced LPI models into radiation-hydrodynamics numerical codes. The interplay between hydrodynamics and LPI—specifically stimulated Raman scatter and crossed-beam energy transfer (CBET)—mostly occurs via momentum and energy deposition into Langmuir and ion acoustic waves. This spatially redistributes energy coupling to the target, which affects the background plasma conditions and thus, modifies laser propagation. In conclusion, this model shows reduced CBET and significant laser energy depletion by Langmuir waves, which reduce the discrepancy between modeling andmore » data from hohlraum experiments on wall x-ray emission and capsule implosion shape.« less
Hydrodynamic granular segregation induced by boundary heating and shear.
Reyes, Francisco Vega; Garzó, Vicente; Khalil, Nagi
2014-05-01
Segregation induced by a thermal gradient of an impurity in a driven low-density granular gas is studied. The system is enclosed between two parallel walls from which we input thermal energy to the gas. We study here steady states occurring when the inelastic cooling is exactly balanced by some external energy input (stochastic force or viscous heating), resulting in a uniform heat flux. A segregation criterion based on Navier-Stokes granular hydrodynamics is written in terms of the tracer diffusion transport coefficients, whose dependence on the parameters of the system (masses, sizes, and coefficients of restitution) is explicitly determined from a solution of the inelastic Boltzmann equation. The theoretical predictions are validated by means of Monte Carlo and molecular dynamics simulations, showing that Navier-Stokes hydrodynamics produces accurate segregation criteria even under strong shearing and/or inelasticity.
Time Evolution of the Anisotropies of the Hydrodynamically Expanding Sqgp
NASA Astrophysics Data System (ADS)
Bagoly, A.; Csanád, M.
In high energy heavy ion collisions of RHIC and LHC, a strongly interacting quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic evolution, before it freezes out to form a hadronic matter. The initial state of the sQGP is determined by the initial distribution of the participating nucleons and their interactions. Due to the finite number of nucleons, the initial distribution fluctuates on an event-by-event basis. The transverse plane anisotropy of the initial state can be translated into a series of anisotropy coefficients or eccentricities: second, third, fourth-order anisotropy etc. These anisotropies then evolve in time, and result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we investigate the time evolution of the anisotropies. With a numerical hydrodynamic code, we analyze how the speed of sound and viscosity influence this evolution.
Hydrodynamic Lagrangian of relativistic superfluids with crystalline structure
NASA Astrophysics Data System (ADS)
Peletminskii, A. S.
2009-09-01
We propose a relativistic Lagrangian formulation of macroscopic dynamics of superfluid systems. The constructed Lagrangian provides the description of ordinary superfluids and superfluids with a crystalline ordering, where both phase and translational symmetries are simultaneously broken (e.g., supersolids or crystalline superfluids in neutron stars). The covariant conservation laws and equations of motion for the field variables associated with the broken symmetries are obtained. The connection to Khalatnikov-Lebedev relativistic hydrodynamic theory is discussed.
Nonlinear Generalized Hydrodynamic Wave Equations in Strongly Coupled Dusty Plasmas
Veeresha, B. M.; Sen, A.; Kaw, P. K.
2008-09-07
A set of nonlinear equations for the study of low frequency waves in a strongly coupled dusty plasma medium is derived using the phenomenological generalized hydrodynamic (GH) model and is used to study the modulational stability of dust acoustic waves to parallel perturbations. Dust compressibility contributions arising from strong Coulomb coupling effects are found to introduce significant modifications in the threshold and range of the instability domain.
Hydrodynamic boundary condition of water on hydrophobic surfaces.
Schaeffel, David; Yordanov, Stoyan; Schmelzeisen, Marcus; Yamamoto, Tetsuya; Kappl, Michael; Schmitz, Roman; Dünweg, Burkhard; Butt, Hans-Jürgen; Koynov, Kaloian
2013-05-01
By combining total internal reflection fluorescence cross-correlation spectroscopy with Brownian dynamics simulations, we were able to measure the hydrodynamic boundary condition of water flowing over a smooth solid surface with exceptional accuracy. We analyzed the flow of aqueous electrolytes over glass coated with a layer of poly(dimethylsiloxane) (advancing contact angle Θ = 108°) or perfluorosilane (Θ = 113°). Within an error of better than 10 nm the slip length was indistinguishable from zero on all surfaces.
Hydrodynamic characterization of Corpus Christi Bay through modeling and observation.
Islam, Mohammad S; Bonner, James S; Edge, Billy L; Page, Cheryl A
2014-11-01
Christi Bay is a relatively flat, shallow, wind-driven system with an average depth of 3-4 m and a mean tidal range of 0.3 m. It is completely mixed most of the time, and as a result, depth-averaged models have, historically, been applied for hydrodynamic characterization supporting regulatory decisions on Texas coastal management. The bay is highly stratified during transitory periods of the summer with low wind conditions. This has important implications on sediment transport, nutrient cycling, and water quality-related issues, including hypoxia which is a key water quality concern for the bay. Detailed hydrodynamic characterization of the bay during the summer months included analysis of simulation results of 2-D hydrodynamic model and high-frequency (HF) in situ observations. The HF radar system resolved surface currents, whereas an acoustic Doppler current profiler (ADCP) measured current at different depths of the water column. The developed model successfully captured water surface elevation variation at the mouth of the bay (i.e., onshore boundary of the Gulf of Mexico) and at times within the bay. However, large discrepancies exist between model-computed depth-averaged water currents and observed surface currents. These discrepancies suggested the presence of a vertical gradient in the current structure which was further substantiated by the observed bi-directional current movement within the water column. In addition, observed vertical density gradients proved that the water column was stratified. Under this condition, the bottom layer became hypoxic due to inadequate mixing with the aerated surface water. Understanding the disparities between observations and model predictions provides critical insights about hydrodynamics and physical processes controlling water quality.
Biomimetic shark skin: design, fabrication and hydrodynamic function.
Wen, Li; Weaver, James C; Lauder, George V
2014-05-15
Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species.
Two-Dimensional Simulation of Truckee River Hydrodynamics
2006-09-01
ANALYSIS: The Truckee River originates from Lake Tahoe , flowing 140 miles (225 km) through Reno, NV, to Pyramid Lake . The downstream boundary of the...riverine restoration design. A two-dimensional (2-D) hydrodynamic model was applied to the McCarran Ranch reach of the Truckee River to evaluate...existing condition and future restoration plan condition hydraulics. The impact of the restoration design is presented in terms of the difference in the
Supernova-relevant hydrodynamic instability experiments on the Nova laser
Kane, J.; Arnett, D.; Remington, B.A.; Glendinning, S.G.; Wallace, R.; Managan, R.; Rubenchik, A. Rubenchik, A. Fryxell, B.A.
1997-04-01
Observations of Supernova 1987A suggest that hydrodynamic instabilities play a critical role in the evolution of supernovae. To test the modeling of these instabilities, and to study instability issues which are difficult to model, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. We use the Nova laser to generate a 10{endash}15 Mbar shock at the interface between an 85 {mu}m thick layer of Cu and a 500 {mu}m layer of CH{sub 2}; our first target is planar. We impose a single mode sinusoidal material perturbation at the interface with {lambda}=200{mu}m, {eta}{sub 0}=20{mu}m, causing perturbation growth by the RM instability as the shock accelerates the interface, and by RT instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few {times}10{sup 3}s. We use the supernova code PROMETHEUS and the hydrodynamics codes HYADES and CALE to model the experiment. We are designing further experiments to compare results for 2D vs. 3D single mode perturbations; high resolution 3D modeling requires prohibitive time and computing resources, but we can perform and study 3D experiments as easily as 2D experiments. Low resolution simulations suggest that the perturbations grow 50{percent} faster in 3D than in 2D; such a difference may help explain the high observed velocities of radioactive core material in SN1987A. We present the results of the experiments and simulations. {copyright} {ital 1997 American Institute of Physics.}
Supernova-relevant hydrodynamic instability experiments on the Nova laser
Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Wallace, R.; Managan, R.; Rubenchik, A.; Fryxell, B. A.
1997-04-15
Observations of Supernova 1987A suggest that hydrodynamic instabilities play a critical role in the evolution of supernovae. To test the modeling of these instabilities, and to study instability issues which are difficult to model, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. We use the Nova laser to generate a 10-15 Mbar shock at the interface between an 85 {mu}m thick layer of Cu and a 500 {mu}m layer of CH{sub 2}; our first target is planar. We impose a single mode sinusoidal material perturbation at the interface with {lambda}=200 {mu}m, {eta}{sub 0}=20 {mu}m, causing perturbation growth by the RM instability as the shock accelerates the interface, and by RT instability as the interface decelerates. This resembles the hydrodynamics of the He-H interface of a Type II supernova at intermediate times, up to a few x10{sup 3} s. We use the supernova code PROMETHEUS and the hydrodynamics codes HYADES and CALE to model the experiment. We are designing further experiments to compare results for 2D vs. 3D single mode perturbations; high resolution 3D modeling requires prohibitive time and computing resources, but we can perform and study 3D experiments as easily as 2D experiments. Low resolution simulations suggest that the perturbations grow 50% faster in 3D than in 2D; such a difference may help explain the high observed velocities of radioactive core material in SN1987A. We present the results of the experiments and simulations.
Constructing higher-order hydrodynamics: The third order
NASA Astrophysics Data System (ADS)
Grozdanov, Sašo; Kaplis, Nikolaos
2016-03-01
Hydrodynamics can be formulated as the gradient expansion of conserved currents in terms of the fundamental fields describing the near-equilibrium fluid flow. In the relativistic case, the Navier-Stokes equations follow from the conservation of the stress-energy tensor to first order in derivatives. In this paper, we go beyond the presently understood second-order hydrodynamics and discuss the systematization of obtaining the hydrodynamic expansion to an arbitrarily high order. As an example of the algorithm that we present, we fully classify the gradient expansion at third order for neutral fluids in four dimensions, thus finding the most general next-to-leading-order corrections to the relativistic Navier-Stokes equations in curved space-time. In doing so, we list 20 new transport coefficient candidates in the conformal case and 68 in the nonconformal case. As we do not consider any constraints that could potentially arise from the local entropy current analysis, this is the maximal possible set of neutral third-order transport coefficients. To investigate the physical implications of these new transport coefficients, we obtain the third-order corrections to the linear dispersion relations that describe the propagation of diffusion and sound waves in relativistic fluids. We also compute the corrections to the scalar (spin-2) two-point correlation function of the third-order stress-energy tensor. Furthermore, as an example of a nonlinear hydrodynamic flow, we calculate the third-order corrections to the energy density of a boost-invariant Bjorken flow. Finally, we apply our field theoretic results to the N =4 supersymmetric Yang-Mills fluid at infinite 't Hooft coupling and an infinite number of colors to find the values of five new linear combinations of the conformal transport coefficients.
Smoothed-particle hydrodynamics and nonequilibrium molecular dynamics
Hoover, W. G.; Hoover, C. G.
1993-08-01
Gingold, Lucy, and Monaghan invented a grid-free version of continuum mechanics ``smoothed-particle hydrodynamics,`` in 1977. It is a likely contributor to ``hybrid`` simulations combining atomistic and continuum simulations. We describe applications of this particle-based continuum technique from the closely-related standpoint of nonequilibrium molecular dynamics. We compare chaotic Lyapunov spectra for atomistic solids and fluids with those which characterize a two-dimensional smoothed-particle fluid system.
Three-Dimensional Hydrodynamic Simulations of OMEGA Implosions
NASA Astrophysics Data System (ADS)
Igumenshchev, I. V.
2016-10-01
The effects of large-scale (with Legendre modes less than 30) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming) and target offset, mount, and layers nonuniformities were investigated using three-dimensional (3-D) hydrodynamic simulations. Simulations indicate that the performance degradation in cryogenic implosions is caused mainly by the target offsets ( 10 to 20 μm), beampower imbalance (σrms 10 %), and initial target asymmetry ( 5% ρRvariation), which distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of the stagnated target. The ion temperature inferred from the width of simulated neutron spectra are influenced by bulk fuel motion in the distorted hot spot and can result in up to 2-keV apparent temperature increase. Similar temperature variations along different lines of sight are observed. Simulated x-ray images of implosion cores in the 4- to 8-keV energy range show good agreement with experiments. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires reducing large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing high-efficient mid-adiabat (α = 4) implosion designs that mitigate cross-beam energy transfer (CBET) and suppress short-wavelength Rayleigh-Taylor growth. These simulations use a new low-noise 3-D Eulerian hydrodynamic code ASTER. Existing 3-D hydrodynamic codes for direct-drive implosions currently miss CBET and noise-free ray-trace laser deposition algorithms. ASTER overcomes these limitations using a simplified 3-D laser-deposition model, which includes CBET and is capable of simulating the effects of beam-power imbalance, beam mispointing, mistiming, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.
Analytical solutions of Landau (1+1)-dimensional hydrodynamics
Wong, Cheuk-Yin; Sen, Abhisek; Gerhard, Jochen; ...
2014-12-17
To help guide our intuition, summarize important features, and point out essential elements, we review the analytical solutions of Landau (1+1)-dimensional hydrodynamics and exhibit the full evolution of the dynamics from the very beginning to subsequent times. Special emphasis is placed on the matching and the interplay between the Khalatnikov solution and the Riemann simple wave solution at the earliest times and in the edge regions at later times.
Fluctuating hydrodynamics of multicomponent membranes with embedded proteins
Camley, Brian A.; Brown, Frank L. H.
2014-08-21
A simulation method for the dynamics of inhomogeneous lipid bilayer membranes is presented. The membrane is treated using stochastic Saffman-Delbrück hydrodynamics, coupled to a phase-field description of lipid composition and discrete membrane proteins. Multiple applications are considered to validate and parameterize the model. The dynamics of membrane composition fluctuations above the critical point and phase separation dynamics below the critical point are studied in some detail, including the effects of adding proteins to the mixture.
Fluctuating hydrodynamics of multicomponent membranes with embedded proteins.
Camley, Brian A; Brown, Frank L H
2014-08-21
A simulation method for the dynamics of inhomogeneous lipid bilayer membranes is presented. The membrane is treated using stochastic Saffman-Delbrück hydrodynamics, coupled to a phase-field description of lipid composition and discrete membrane proteins. Multiple applications are considered to validate and parameterize the model. The dynamics of membrane composition fluctuations above the critical point and phase separation dynamics below the critical point are studied in some detail, including the effects of adding proteins to the mixture.
Emergence of Upstream Swimming via a Hydrodynamic Transition
NASA Astrophysics Data System (ADS)
Tung, Chih-kuan; Ardon, Florencia; Roy, Anubhab; Koch, Donald L.; Suarez, Susan S.; Wu, Mingming
2015-03-01
We demonstrate that upstream swimming of sperm emerges via an orientation disorder-order transition. The order parameter, the average orientation of the sperm head against the flow, follows a 0.5 power law with the deviation from the critical flow shear rate (γ -γc ). This transition is successfully explained by a hydrodynamic bifurcation theory, which extends the sperm upstream swimming to a broad class of near surface microswimmers that possess front-back asymmetry and circular motion.
THE KOZAI-LIDOV MECHANISM IN HYDRODYNAMICAL DISKS
Martin, Rebecca G.; Nixon, Chris; Armitage, Philip J.; Lubow, Stephen H.; Price, Daniel J.; Doğan, Suzan; King, Andrew
2014-09-10
We use three-dimensional hydrodynamical simulations to show that a highly misaligned accretion disk around one component of a binary system can exhibit global Kozai-Lidov cycles, where the inclination and eccentricity of the disk are interchanged periodically. This has important implications for accreting systems on all scales, for example, the formation of planets and satellites in circumstellar and circumplanetary disks, outbursts in X-ray binary systems, and accretion onto supermassive black holes.
Lagrangian formulation of relativistic Israel-Stewart hydrodynamics
NASA Astrophysics Data System (ADS)
Montenegro, David; Torrieri, Giorgio
2016-09-01
We rederive relativistic hydrodynamics as a Lagrangian effective theory using the doubled coordinates technique, allowing us to include dissipative terms. We include Navier-Stokes shear and bulk terms, as well as Israel-Stewart relaxation time terms, within this formalism. We show how the inclusion of shear dissipation forces the inclusion of the Israel-Stewart term into the theory, thereby providing an additional justification for the form of this term.
Smoothed-particle hydrodynamics and nonequilibrium molecular dynamics
NASA Astrophysics Data System (ADS)
Hoover, W. G.; Hoover, C. G.
1993-08-01
Gingold, Lucy, and Monaghan invented a grid-free version of continuum mechanics 'smoothed-particle hydrodynamics,' in 1977. It is a likely contributor to 'hybrid' simulations combining atomistic and continuum simulations. We describe applications of this particle-based continuum technique from the closely-related standpoint of nonequilibrium molecular dynamics. We compare chaotic Lyapunov spectra for atomistic solids and fluids with those which characterize a two-dimensional smoothed-particle fluid system.
Including Nearshore Processes in Phase-Averaged Hydrodynamics Models
2006-08-01
physical modeling of hydrodynamics to the use of numerical models. A suitable set of equations conserving mass, momen- tum, and energy do not suffer...the high cost and scale effects of physical models. Numerical models, however, rely on a set of discritized and sim- plified equations , and nonphysical...used in the interest of brevity. The solution of Equation 24 along with Equation 26 constitutes a solution for the depth-dependent cross-shore
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, L.; Kalsi, M.S.
1999-02-23
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. 14 figs.
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, Lannie; Kalsi, Manmohan Singh
1999-01-01
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland.
Hydrodynamic quantum analogues: droplets walking on the impossible pilot wave
NASA Astrophysics Data System (ADS)
Bush, John
2012-11-01
Yves Couder and coworkers have demonstrated that droplets walking on a vibrating fluid bath exhibit several features previously thought to be peculiar to the microscopic quantum realm. We explore the connection between this hydrodynamic system and the pilot-wave theory of quantum mechanics proposed by de Broglie and extended by workers in the field of stochastic electrodynamics. Critical common features of these ostensibly disparate systems are identified, and quantitative differences noted. The author thanks the NSF.
Electrohydrodynamics and other hydrodynamic phenomena in continuous flow electrophoresis
NASA Technical Reports Server (NTRS)
Saville, D. A.
1982-01-01
The process known as continuous flow electrophoresis employs an electric field to separate the constituents of particulate samples suspended in a liquid. Complications arise because the electric field generates temperature gradients due to Joule heating and derives an electrohydrodynamic crossflow. Several aspects of the flow are discussed including entrance effects, hydrodynamic stability and a flow restructuring due to the combined effects of buoyancy and the crossflow.
Kinetic theory of flocking: Derivation of hydrodynamic equations
NASA Astrophysics Data System (ADS)
Ihle, Thomas
2011-03-01
It is shown how to explicitly coarse-grain the microscopic dynamics of the rule-based Vicsek model for self-propelled agents. The hydrodynamic equations are derived by means of an Enskog-type kinetic theory. Expressions for all transport coefficients are given. The transition from a disordered to a flocking state, which at large particle speeds appears to be a fluctuation-induced first-order phase transition, is studied numerically and analytically.
Parameterization of wind turbine impacts on hydrodynamics and sediment transport
NASA Astrophysics Data System (ADS)
Rivier, Aurélie; Bennis, Anne-Claire; Pinon, Grégory; Magar, Vanesa; Gross, Markus
2016-10-01
Monopile foundations of offshore wind turbines modify the hydrodynamics and sediment transport at local and regional scales. The aim of this work is to assess these modifications and to parameterize them in a regional model. In the present study, this is achieved through a regional circulation model, coupled with a sediment transport module, using two approaches. One approach is to explicitly model the monopiles in the mesh as dry cells, and the other is to parameterize them by adding a drag force term to the momentum and turbulence equations. Idealised cases are run using hydrodynamical conditions and sediment grain sizes typical from the area located off Courseulles-sur-Mer (Normandy, France), where an offshore windfarm is under planning, to assess the capacity of the model to reproduce the effect of the monopile on the environment. Then, the model is applied to a real configuration on an area including the future offshore windfarm of Courseulles-sur-Mer. Four monopiles are represented in the model using both approaches, and modifications of the hydrodynamics and sediment transport are assessed over a tidal cycle. In relation to local hydrodynamic effects, it is observed that currents increase at the side of the monopile and decrease in front of and downstream of the monopile. In relation to sediment transport effect, the results show that resuspension and erosion occur around the monopile in locations where the current speed increases due to the monopile presence, and sediments deposit downstream where the bed shear stress is lower. During the tidal cycle, wakes downstream of the monopile reach the following monopile and modify the velocity magnitude and suspended sediment concentration patterns around the second monopile.
Hydrodynamic starvation in first-feeding larval fishes
China, Victor; Holzman, Roi
2014-01-01
Larval fishes suffer prodigious mortality rates, eliminating 99% of the brood within a few days after first feeding. Hjort (1914) famously attributed this “critical period” of low survival to the larvae’s inability to obtain sufficient food [Hjort (1914) Rapp P-v Réun Cons Int Explor Mer 20:1–228]. However, the cause of this poor feeding success remains to be identified. Here, we show that hydrodynamic constraints on the ubiquitous suction mechanism in first-feeding larvae limit their ability to capture prey, thereby reducing their feeding rates. Dynamic-scaling experiments revealed that larval size is the primary determinant of feeding rate, independent of other ontogenetic effects. We conclude that first-feeding larvae experience “hydrodynamic starvation,” in which low Reynolds numbers mechanistically limit their feeding performance even under high prey densities. Our results provide a hydrodynamic perspective on feeding of larval fishes that focuses on the physical properties of the larvae and prey, rather than on prey concentration and the rate of encounters. PMID:24843180
Comparison of Non-Parabolic Hydrodynamic Simulations for Semiconductor Devices
NASA Technical Reports Server (NTRS)
Smith, A. W.; Brennan, K. F.
1996-01-01
Parabolic drift-diffusion simulators are common engineering level design tools for semiconductor devices. Hydrodynamic simulators, based on the parabolic band approximation, are becoming more prevalent as device dimensions shrink and energy transport effects begin to dominate device characteristic. However, band structure effects present in state-of-the-art devices necessitate relaxing the parabolic band approximation. This paper presents simulations of ballistic diodes, a benchmark device, of Si and GaAs using two different non-parabolic hydrodynamic formulations. The first formulation uses the Kane dispersion relationship in the derivation of the conservation equations. The second model uses a power law dispersion relation {(hk)(exp 2)/2m = xW(exp Y)}. Current-voltage relations show that for the ballistic diodes considered. the non-parabolic formulations predict less current than the parabolic case. Explanations of this will be provided by examination of velocity and energy profiles. At low bias, the simulations based on the Kane formulation predict greater current flow than the power law formulation. As the bias is increased this trend changes and the power law predicts greater current than the Kane formulation. It will be shown that the non-parabolicity and energy range of the hydrodynamic model based on the Kane dispersion relation are limited due to the binomial approximation which was utilized in the derivation.