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Sample records for dimensional compressible hydrodynamic

  1. VH-1: Multidimensional ideal compressible hydrodynamics code

    NASA Astrophysics Data System (ADS)

    Hawley, John; Blondin, John; Lindahl, Greg; Lufkin, Eric

    2012-04-01

    VH-1 is a multidimensional ideal compressible hydrodynamics code written in FORTRAN for use on any computing platform, from desktop workstations to supercomputers. It uses a Lagrangian remap version of the Piecewise Parabolic Method developed by Paul Woodward and Phil Colella in their 1984 paper. VH-1 comes in a variety of versions, from a simple one-dimensional serial variant to a multi-dimensional version scalable to thousands of processors.

  2. Scaling relations in two-dimensional relativistic hydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Westernacher-Schneider, John Ryan; Lehner, Luis; Oz, Yaron

    2015-12-01

    We derive exact scaling relations for two-dimensional relativistic hydrodynamic turbulence in the inertial range of scales. We consider both the energy cascade towards large scales and the enstrophy cascade towards small scales. We illustrate these relations by numerical simulations of turbulent weakly compressible flows. Intriguingly, the fluid-gravity correspondence implies that the gravitational field in black hole/black brane spacetimes with anti-de Sitter asymptotics should exhibit similar scaling relations.

  3. Superresonant instability of a compressible hydrodynamic vortex

    NASA Astrophysics Data System (ADS)

    Oliveira, Leandro A.; Cardoso, Vitor; Crispino, Luís C. B.

    2016-06-01

    We show that a purely circulating and compressible system, in an adiabatic regime of acoustic propagation, presents superresonant instabilities. To show the existence these instabilities, we compute the quasinormal mode frequencies of this system numerically using two different frequency domain methods.

  4. Reliable estimation of shock position in shock-capturing compressible hydrodynamics codes

    SciTech Connect

    Nelson, Eric M

    2008-01-01

    The displacement method for estimating shock position in a shock-capturing compressible hydrodynamics code is introduced. Common estimates use simulation data within the captured shock, but the displacement method uses data behind the shock, making the estimate consistent with and as reliable as estimates of material parameters obtained from averages or fits behind the shock. The displacement method is described in the context of a steady shock in a one-dimensional lagrangian hydrodynamics code, and demonstrated on a piston problem and a spherical blast wave.The displacement method's estimates of shock position are much better than common estimates in such applications.

  5. Compressible Lagrangian hydrodynamics without Lagrangian cells

    NASA Astrophysics Data System (ADS)

    Clark, Robert A.

    The partial differential Eqs [2.1, 2.2, and 2.3], along with the equation of state 2.4, which describe the time evolution of compressible fluid flow can be solved without the use of a Lagrangian mesh. The method follows embedded fluid points and uses finite difference approximations to ěc nablaP and ěc nabla · ěc u to update p, ěc u and e. We have demonstrated that the method can accurately calculate highly distorted flows without difficulty. The finite difference approximations are not unique, improvements may be found in the near future. The neighbor selection is not unique, but the one being used at present appears to do an excellent job. The method could be directly extended to three dimensions. One drawback to the method is the failure toexplicitly conserve mass, momentum and energy. In fact, at any given time, the mass is not defined. We must perform an auxiliary calculation by integrating the density field over space to obtain mass, energy and momentum. However, in all cases where we have done this, we have found the drift in these quantities to be no more than a few percent.

  6. CASTRO: A NEW COMPRESSIBLE ASTROPHYSICAL SOLVER. II. GRAY RADIATION HYDRODYNAMICS

    SciTech Connect

    Zhang, W.; Almgren, A.; Bell, J.; Howell, L.; Burrows, A.

    2011-10-01

    We describe the development of a flux-limited gray radiation solver for the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically rectangular variable-sized grids with simultaneous refinement in both space and time. The gray radiation solver is based on a mixed-frame formulation of radiation hydrodynamics. In our approach, the system is split into two parts, one part that couples the radiation and fluid in a hyperbolic subsystem, and another parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem is solved explicitly with a high-order Godunov scheme, whereas the parabolic part is solved implicitly with a first-order backward Euler method.

  7. Pencil: Finite-difference Code for Compressible Hydrodynamic Flows

    NASA Astrophysics Data System (ADS)

    Brandenburg, Axel; Dobler, Wolfgang

    2010-10-01

    The Pencil code is a high-order finite-difference code for compressible hydrodynamic flows with magnetic fields. It is highly modular and can easily be adapted to different types of problems. The code runs efficiently under MPI on massively parallel shared- or distributed-memory computers, like e.g. large Beowulf clusters. The Pencil code is primarily designed to deal with weakly compressible turbulent flows. To achieve good parallelization, explicit (as opposed to compact) finite differences are used. Typical scientific targets include driven MHD turbulence in a periodic box, convection in a slab with non-periodic upper and lower boundaries, a convective star embedded in a fully nonperiodic box, accretion disc turbulence in the shearing sheet approximation, self-gravity, non-local radiation transfer, dust particle evolution with feedback on the gas, etc. A range of artificial viscosity and diffusion schemes can be invoked to deal with supersonic flows. For direct simulations regular viscosity and diffusion is being used. The code is written in well-commented Fortran90.

  8. CASTRO: A NEW COMPRESSIBLE ASTROPHYSICAL SOLVER. III. MULTIGROUP RADIATION HYDRODYNAMICS

    SciTech Connect

    Zhang, W.; Almgren, A.; Bell, J.; Howell, L.; Burrows, A.; Dolence, J.

    2013-01-15

    We present a formulation for multigroup radiation hydrodynamics that is correct to order O(v/c) using the comoving-frame approach and the flux-limited diffusion approximation. We describe a numerical algorithm for solving the system, implemented in the compressible astrophysics code, CASTRO. CASTRO uses a Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically rectangular variable-sized grids with simultaneous refinement in both space and time. In our multigroup radiation solver, the system is split into three parts: one part that couples the radiation and fluid in a hyperbolic subsystem, another part that advects the radiation in frequency space, and a parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem and the frequency space advection are solved explicitly with high-order Godunov schemes, whereas the parabolic part is solved implicitly with a first-order backward Euler method. Our multigroup radiation solver works for both neutrino and photon radiation.

  9. CASTRO: A New Compressible Astrophysical Solver. III. Multigroup Radiation Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Howell, L.; Almgren, A.; Burrows, A.; Dolence, J.; Bell, J.

    2013-01-01

    We present a formulation for multigroup radiation hydrodynamics that is correct to order O(v/c) using the comoving-frame approach and the flux-limited diffusion approximation. We describe a numerical algorithm for solving the system, implemented in the compressible astrophysics code, CASTRO. CASTRO uses a Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically rectangular variable-sized grids with simultaneous refinement in both space and time. In our multigroup radiation solver, the system is split into three parts: one part that couples the radiation and fluid in a hyperbolic subsystem, another part that advects the radiation in frequency space, and a parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem and the frequency space advection are solved explicitly with high-order Godunov schemes, whereas the parabolic part is solved implicitly with a first-order backward Euler method. Our multigroup radiation solver works for both neutrino and photon radiation.

  10. Three-dimensional hydrodynamic instabilities in stellar core collapses

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Lian, Biao

    2012-03-01

    A spherically symmetric hydrodynamic stellar core collapse process under gravity is time-dependent and may become unstable once disturbed. Subsequent non-linear evolutions of such growth of hydrodynamic instabilities may lead to various physical consequences. Specifically for a homologous collapse of a stellar core characterized by a polytropic exponent Γ= 4/3, we examine oscillations and/or instabilities of three-dimensional (3D) general polytropic perturbations. Being incompressible, the radial component of vorticity perturbation always grows unstably during the same homologous core collapse. For compressible 3D perturbations, the polytropic index γ of perturbations can differ from Γ= 4/3 of the general polytropic hydrodynamic background flow, where the background specific entropy is conserved along streamlines and can vary in radius and time. Our model formulation here is more general than previous ones. The Brunt-Väisälä buoyancy frequency ? does not vanish, allowing for the existence of internal gravity g- modes and/or g+ modes, depending on the sign of ? respectively. Eigenvalues and eigenfunctions of various oscillatory and unstable perturbation modes are computed, given asymptotic boundary conditions. As studied in several specialized cases of Goldreich & Weber and of Lou & Cao and Cao & Lou, we further confirm that acoustic p modes and surface f modes remain stable in the current more general situations. In comparison, g- modes and sufficiently high radial order g+ modes are unstable, leading to inevitable convective motions within the collapsing stellar interior; meanwhile, sufficiently low radial order g+ modes remain stably trapped in the collapsing core. Unstable growths of 3D g-mode disturbances are governed dominantly by the angular momentum conservation and modified by the gas pressure restoring force. We note in particular that unstable temporal growths of 3D vortical perturbations exist even when the specific entropy distribution becomes

  11. Hydrodynamic stability of three-dimensional homogeneous flow topologies

    NASA Astrophysics Data System (ADS)

    Mishra, Aashwin A.; Girimaji, Sharath S.

    2015-11-01

    This article examines the hydrodynamic stability of various homogeneous three-dimensional flow topologies. The influence of inertial and pressure effects on the stability of flows undergoing strain, rotation, convergence, divergence, and swirl are isolated. In marked contrast to two-dimensional topologies, for three-dimensional flows the inertial effects are always destabilizing, whereas pressure effects are always stabilizing. In streamline topologies with a negative velocity-gradient third invariant, inertial effects prevail leading to instability. Vortex-stretching is identified as the underlying instability mechanism. In flows with positive velocity-gradient third derivative, pressure overcomes inertial effects to stabilize the flow.

  12. One-dimensional XY model: Ergodic properties and hydrodynamic limit

    NASA Astrophysics Data System (ADS)

    Shuhov, A. G.; Suhov, Yu. M.

    1986-11-01

    We prove theorems on convergence to a stationary state in the course of time for the one-dimensional XY model and its generalizations. The key point is the well-known Jordan-Wigner transformation, which maps the XY dynamics onto a group of Bogoliubov transformations on the CAR C *-algebra over Z 1. The role of stationary states for Bogoliubov transformations is played by quasifree states and for the XY model by their inverse images with respect to the Jordan-Wigner transformation. The hydrodynamic limit for the one-dimensional XY model is also considered. By using the Jordan-Wigner transformation one reduces the problem to that of constructing the hydrodynamic limit for the group of Bogoliubov transformations. As a result, we obtain an independent motion of "normal modes," which is described by a hyperbolic linear differential equation of second order. For the XX model this equation reduces to a first-order transfer equation.

  13. Analytical solutions of Landau (1+1)-dimensional hydrodynamics

    DOE PAGESBeta

    Wong, Cheuk-Yin; Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Kenneth

    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.

  14. Analytical Solutions of Landau (1+1)-Dimensional Hydrodynamics

    SciTech Connect

    Sen, Abhisek; Gerhard, Jochen; Torrieri, Giorgio; Read, Jr, Kenneth F

    2014-01-01

    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.

  15. Second-order (2 +1 ) -dimensional anisotropic hydrodynamics

    NASA Astrophysics Data System (ADS)

    Bazow, Dennis; Heinz, Ulrich; Strickland, Michael

    2014-11-01

    We present a complete formulation of second-order (2 +1 ) -dimensional anisotropic hydrodynamics. The resulting framework generalizes leading-order anisotropic hydrodynamics by allowing for deviations of the one-particle distribution function from the spheroidal form assumed at leading order. We derive complete second-order equations of motion for the additional terms in the macroscopic currents generated by these deviations from their kinetic definition using a Grad-Israel-Stewart 14-moment ansatz. The result is a set of coupled partial differential equations for the momentum-space anisotropy parameter, effective temperature, the transverse components of the fluid four-velocity, and the viscous tensor components generated by deviations of the distribution from spheroidal form. We then perform a quantitative test of our approach by applying it to the case of one-dimensional boost-invariant expansion in the relaxation time approximation (RTA) in which case it is possible to numerically solve the Boltzmann equation exactly. We demonstrate that the second-order anisotropic hydrodynamics approach provides an excellent approximation to the exact (0+1)-dimensional RTA solution for both small and large values of the shear viscosity.

  16. Scaling and self-similarity in two-dimensional hydrodynamics.

    PubMed

    Ercan, Ali; Kavvas, M Levent

    2015-07-01

    The conditions under which depth-averaged two-dimensional (2D) hydrodynamic equations system as an initial-boundary value problem (IBVP) becomes self-similar are investigated by utilizing one-parameter Lie group of point scaling transformations. Self-similarity conditions due to the 2D k-ε turbulence model are also investigated. The self-similarity conditions for the depth-averaged 2D hydrodynamics are found for the flow variables including the time, the longitudinal length, the transverse length, the water depth, the flow velocities in x- and y-directions, the bed shear stresses in x- and y-directions, the bed shear velocity, the Manning's roughness coefficient, the kinematic viscosity of the fluid, the eddy viscosity, the turbulent kinetic energy, the turbulent dissipation, and the production and the source terms in the k-ε model. By the numerical simulations, it is shown that the IBVP of depth-averaged 2D hydrodynamic flow process in a prototype domain can be self-similar with that of a scaled domain. In fact, by changing the scaling parameter and the scaling exponents of the length dimensions, one can obtain several different scaled domains. The proposed scaling relations obtained by the Lie group scaling approach may provide additional spatial, temporal, and economical flexibility in setting up physical hydraulic models in which two-dimensional flow components are important. PMID:26232977

  17. Correlating hydrodynamic radii with that of two-dimensional nanoparticles

    SciTech Connect

    Yue, Yuan; Kan, Yuwei; Clearfield, Abraham; Choi, Hyunho; Liang, Hong

    2015-12-21

    Dynamic light scattering (DLS) is one of the most adapted methods to measure the size of nanoparticles, as referred to the hydrodynamic radii (R{sub h}). However, the R{sub h} represents only that of three-dimensional spherical nanoparticles. In the present research, the size of two-dimensional (2D) nanoparticles of yttrium oxide (Y{sub 2}O{sub 3}) and zirconium phosphate (ZrP) was evaluated through comparing their hydrodynamic diameters via DLS with lateral sizes obtained using scanning and transmission electron microscopy. We demonstrate that the hydrodynamic radii are correlated with the lateral sizes of both square and circle shaped 2D nanoparticles. Two proportional coefficients, i.e., correcting factors, are proposed for the Brownian motion status of 2D nanoparticles. The correction is possible by simplifying the calculation of integrals in the case of small thickness approximation. The correcting factor has great significance for investigating the translational diffusion behavior of 2D nanoparticles in a liquid and in effective and low-cost measurement in terms of size and morphology of shape-specific nanoparticles.

  18. Correlating hydrodynamic radii with that of two-dimensional nanoparticles

    NASA Astrophysics Data System (ADS)

    Yue, Yuan; Kan, Yuwei; Choi, Hyunho; Clearfield, Abraham; Liang, Hong

    2015-12-01

    Dynamic light scattering (DLS) is one of the most adapted methods to measure the size of nanoparticles, as referred to the hydrodynamic radii (Rh). However, the Rh represents only that of three-dimensional spherical nanoparticles. In the present research, the size of two-dimensional (2D) nanoparticles of yttrium oxide (Y2O3) and zirconium phosphate (ZrP) was evaluated through comparing their hydrodynamic diameters via DLS with lateral sizes obtained using scanning and transmission electron microscopy. We demonstrate that the hydrodynamic radii are correlated with the lateral sizes of both square and circle shaped 2D nanoparticles. Two proportional coefficients, i.e., correcting factors, are proposed for the Brownian motion status of 2D nanoparticles. The correction is possible by simplifying the calculation of integrals in the case of small thickness approximation. The correcting factor has great significance for investigating the translational diffusion behavior of 2D nanoparticles in a liquid and in effective and low-cost measurement in terms of size and morphology of shape-specific nanoparticles.

  19. Advanced three-dimensional Eulerian hydrodynamic algorithm development

    SciTech Connect

    Rider, W.J.; Kothe, D.B.; Mosso, S.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project is to investigate, implement, and evaluate algorithms that have high potential for improving the robustness, fidelity and accuracy of three-dimensional Eulerian hydrodynamic simulations. Eulerian computations are necessary to simulate a number of important physical phenomena ranging from the molding process for metal parts to nuclear weapons safety issues to astrophysical phenomena such as that associated with a Type 2 supernovae. A number of algorithmic issues were explored in the course of this research including interface/volume tracking, surface physics integration, high resolution integration techniques, multilevel iterative methods, multimaterial hydrodynamics and coupling radiation with hydrodynamics. This project combines core strengths of several Laboratory divisions. The project has high institutional benefit given the renewed emphasis on numerical simulations in Science-Based Stockpile Stewardship and the Accelerated Strategic Computing Initiative and LANL`s tactical goals related to high performance computing and simulation.

  20. Adaptive rezoner in a two-dimensional Lagrangian hydrodynamic code

    SciTech Connect

    Pyun, J.J.; Saltzman, J.S.; Scannapieco, A.J.; Carroll, D.

    1985-01-01

    In an effort to increase spatial resolution without adding additional meshes, an adaptive mesh was incorporated into a two-dimensional Lagrangian hydrodynamics code along with two-dimensional flux corrected (FCT) remapper. The adaptive mesh automatically generates a mesh based on smoothness and orthogonality, and at the same time also tracks physical conditions of interest by focusing mesh points in regions that exhibit those conditions; this is done by defining a weighting function associated with the physical conditions to be tracked. The FCT remapper calculates the net transportive fluxes based on a weighted average of two fluxes computed by a low-order scheme and a high-order scheme. This averaging procedure produces solutions which are conservative and nondiffusive, and maintains positivity. 10 refs., 12 figs.

  1. Two dimensional hydrodynamic modeling of a high latitude braided river

    NASA Astrophysics Data System (ADS)

    Humphries, E.; Pavelsky, T.; Bates, P. D.

    2014-12-01

    Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.

  2. Low Mach number two-dimensional hydrodynamic turbulence - Energy budgets and density fluctuations in a polytropic fluid

    NASA Technical Reports Server (NTRS)

    Ghosh, S.; Matthaeus, W. H.

    1992-01-01

    Theory suggests that three distinct types of turbulence can occur in the low Mach number limit of polytropic flow: nearly incompressible flows dominated by vorticity, nearly pure acoustic turbulence dominated by compression, and flows characterized by near statistical equipartition of vorticity and compressions. Distinctions between these kinds of turbulence are investigated here by direct numerical simulation of two-dimensional compressible hydrodynamic turbulence. Dynamical scalings of density fluctuations, examination of the ratio of transverse to longitudinal velocity fluctuations, and spectral decomposition of the fluctuations are employed to distinguish the nature of these low Mach number solutions. A strong dependence on the initial data is observed, as well as a tendency for enhanced effects of compressibility at later times and at higher wave numbers, as suggested by theories of nearly incompressible flows.

  3. Developing a Multi-Dimensional Hydrodynamics Code with Astrochemical Reactions

    NASA Astrophysics Data System (ADS)

    Kwak, Kyujin; Yang, Seungwon

    2015-08-01

    The Atacama Large Millimeter/submillimeter Array (ALMA) revealed high resolution molecular lines some of which are still unidentified yet. Because formation of these astrochemical molecules has been seldom studied in traditional chemistry, observations of new molecular lines drew a lot of attention from not only astronomers but also chemists both experimental and theoretical. Theoretical calculations for the formation of these astrochemical molecules have been carried out providing reaction rates for some important molecules, and some of theoretical predictions have been measured in laboratories. The reaction rates for the astronomically important molecules are now collected to form databases some of which are publically available. By utilizing these databases, we develop a multi-dimensional hydrodynamics code that includes the reaction rates of astrochemical molecules. Because this type of hydrodynamics code is able to trace the molecular formation in a non-equilibrium fashion, it is useful to study the formation history of these molecules that affects the spatial distribution of some specific molecules. We present the development procedure of this code and some test problems in order to verify and validate the developed code.

  4. 3+1 dimensional viscous hydrodynamics at high baryon densities

    NASA Astrophysics Data System (ADS)

    Karpenko, Iu; Bleicher, M.; Huovinen, P.; Petersen, H.

    2015-05-01

    A 3+1 dimensional event-by-event viscous hydrodynamic + cascade model is applied for the simulation of heavy ion collision reactions at \\sqrt{sNN} = 6.3... 200 GeV. UrQMD cascade is used for the pre-thermal (pre-hydro) and final (post-hydro) stages of the reaction. The baryon, as well as electric charge densities are consistently taken into account in the model. For this aim the equation of state based on a Chiral model coupled to the Polyakov loop is used in hydrodynamic phase of evolution. As a result of the model adjustment to the experimental data, the effective values of the shear viscosity over entropy density η/s are obtained for different collision energies in the BES region. A decrease of the effective values of η/s from 0.2 to 0.08 is observed as collision energy increases from \\sqrt{s} ≈ 7 to 39 GeV.

  5. A two-dimensional hydrodynamic model of a tidal estuary

    USGS Publications Warehouse

    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.

  6. Two-dimensional symmetrical inlets with external compression

    NASA Technical Reports Server (NTRS)

    Ruden, P

    1950-01-01

    The purpose of inlets like, for instance, those of air-cooled radiators and scoops is to take a certain air quantity out of the free stream and to partly convert the free-stream velocity into pressure. In the extreme case this pressure conversion may occur either entirely in the interior of the inlet (inlet with internal compression) or entirely in the free stream ahead of the inlet (inlet with external compression). In this report a theory for two-dimensional inlets with external compression is developed and illustrated by numerical examples. Intermediary forms between inlets with internal and external compression which can be derived from the latter are briefly discussed.

  7. Three-dimensional hydrodynamic simulations of L2 Puppis

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Nordhaus, Jason; Frank, Adam; Blackman, Eric G.; Balick, Bruce

    2016-08-01

    Recent observations of the L2 Puppis system suggest that this Mira-like variable may be in the early stages of forming a bipolar planetary nebula. As one of nearest and brightest asymptotic giant branch (AGB) stars, thought be a binary, L2 Puppis serves as a benchmark object for studying the late-stages of stellar evolution. We perform global, three-dimensional, adaptive-mesh-refinement hydrodynamic simulations of the L2 Puppis system with ASTROBEAR. We use the radiative transfer code RADMC-3D to construct the broad-band spectral energy distribution and synthetic observational images from our simulations. Given the reported binary parameters, we are able to reproduce the current observational data if a short pulse of dense material is released from the AGB star with a velocity sufficient to escape the primary but not the binary. Such a situation could result from a thermal pulse, be induced by a periastron passage of the secondary, or could be launched if the primary ingests a planet.

  8. Three-dimensional hydrodynamic focusing in a microfluidic Coulter counter

    NASA Astrophysics Data System (ADS)

    Scott, R.; Sethu, P.; Harnett, C. K.

    2008-04-01

    Electrical impedance-based particle detection or Coulter counting, offers a lab-on-chip compatible method for flow cytometry. Developments in this area will produce devices with greater portability, lower cost, and lower power requirements than fluorescence-based flow cytometry. Because conventional Coulter apertures are prone to clogging, hydrodynamic focusing improves the device by creating fluid-walled channels with variable width to increase sensitivity without the associated risk of blocking the channel. We describe a device that focuses the sample in three dimensions, creating a narrow sample stream on the floor of the channel for close interaction with sensing electrodes. The key to this design is a stepped outlet channel fabricated in a single layer with soft lithography. In contrast to previous impedance-based designs, the new design requires minimal alignment with the substrate. Three-dimensional focusing maximizes the sensitivity of the device to cell-size particles within much larger channels. Impedance-based particle sensing experiments within this device show an increase in percentage conductivity change by a factor of 2.5 over devices that only focus the sample in the horizontal direction.

  9. Three-dimensional hydrodynamic simulations of L2 Puppis

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Nordhaus, Jason; Frank, Adam; Blackman, Eric G.; Balick, Bruce

    2016-06-01

    Recent observations of the L2 Puppis system suggest that this Mira-like variable may be in the early stages of forming a bipolar planetary nebula (PN). As one of nearest and brightest AGB stars, thought be a binary, L2 Puppis serves as a benchmark object for studying the late-stages of stellar evolution. We perform global, three-dimensional, adaptive-mesh-refinement hydrodynamic simulations of the L2 Puppis system with ASTROBEAR. We use the radiative transfer code RADMC-3D to construct the broad-band spectral-energy-distribution (SED) and synthetic observational images from our simulations. Given the reported binary parameters, we are able to reproduce the current observational data if a short pulse of dense material is released from the AGB star with a velocity sufficient to escape the primary but not the binary. Such a situation could result from a thermal pulse, be induced by a periastron passage of the secondary, or could be launched if the primary ingests a planet.

  10. A Three-Dimensional Hydrodynamic Focusing Method for Polyplex Synthesis

    PubMed Central

    Lu, Mengqian; Ho, Yi-Ping; Grigsby, Christopher L.; Nawaz, Ahmad Ahsan; Leong, Kam W.; Huang, Tony Jun

    2014-01-01

    Successful intracellular delivery of nucleic acid therapeutics relies on multi-aspect optimization, one of which is formulation. While there has been ample innovation on chemical design of polymeric gene carriers, the same cannot be said for physical processing of polymer-DNA nanocomplexes (polyplexes). Conventional synthesis of polyplexes by bulk mixing depends on the operators’ experience. The poorly controlled bulk-mixing process may also lead to batch-to-batch variation and consequent irreproducibility. Here, we synthesize polyplexes by using a three-dimensional hydrodynamic focusing (3D-HF) technique in a single-layered, planar microfluidic device. Without any additional chemical treatment or post processing, the polyplexes prepared by the 3D-HF method show smaller size, slower aggregation rate, and higher transfection efficiency, while exhibiting reduced cytotoxicity compared to the ones synthesized by conventional bulk mixing. In addition, by introducing external acoustic perturbation, mixing can be further enhanced, leading to even smaller nanocomplexes. The 3D-HF method provides a simple and reproducible process for synthesizing high-quality polyplexes, addressing a critical barrier in the eventual translation of nucleic acid therapeutics. PMID:24341632

  11. Incompressible-compressible flows with a transient discontinuous interface using smoothed particle hydrodynamics (SPH)

    NASA Astrophysics Data System (ADS)

    Lind, S. J.; Stansby, P. K.; Rogers, B. D.

    2016-03-01

    A new two-phase incompressible-compressible Smoothed Particle Hydrodynamics (SPH) method has been developed where the interface is discontinuous in density. This is applied to water-air problems with a large density difference. The incompressible phase requires surface pressure from the compressible phase and the compressible phase requires surface velocity from the incompressible phase. Compressible SPH is used for the air phase (with the isothermal stiffened ideal gas equation of state for low Mach numbers) and divergence-free (projection based) incompressible SPH is used for the water phase, with the addition of Fickian shifting to produce sufficiently homogeneous particle distributions to enable stable, accurate, converged solutions without noise in the pressure field. Shifting is a purely numerical particle regularisation device. The interface remains a true material discontinuity at a high density ratio with continuous pressure and velocity at the interface. This approach with the physics of compressibility and incompressibility represented is novel within SPH and is validated against semi-analytical results for a two-phase elongating and oscillating water drop, analytical results for low amplitude inviscid standing waves, the Kelvin-Helmholtz instability, and a dam break problem with high interface distortion and impact on a vertical wall where experimental and other numerical results are available.

  12. Formation of globular clusters induced by external ultraviolet radiation II: Three-dimensional radiation hydrodynamics simulations

    NASA Astrophysics Data System (ADS)

    Abe, Makito; Umemura, Masayuki; Hasegawa, Kenji

    2016-08-01

    We explore the possibility of the formation of globular clusters under ultraviolet (UV) background radiation. One-dimensional spherical symmetric radiation hydrodynamics (RHD) simulations by Hasegawa et al. have demonstrated that the collapse of low-mass (106-7 M⊙) gas clouds exposed to intense UV radiation can lead to the formation of compact star clusters like globular clusters (GCs) if gas clouds contract with supersonic infall velocities. However, three-dimensional effects, such as the anisotropy of background radiation and the inhomogeneity in gas clouds, have not been studied so far. In this paper, we perform three-dimensional RHD simulations in a semi-cosmological context, and reconsider the formation of compact star clusters in strong UV radiation fields. As a result, we find that although anisotropic radiation fields bring an elongated shadow of neutral gas, almost spherical compact star clusters can be procreated from a "supersonic infall" cloud, since photo-dissociating radiation suppresses the formation of hydrogen molecules in the shadowed regions and the regions are compressed by UV heated ambient gas. The properties of resultant star clusters match those of GCs. On the other hand, in weak UV radiation fields, dark matter-dominated star clusters with low stellar density form due to the self-shielding effect as well as the positive feedback by ionizing photons. Thus, we conclude that the "supersonic infall" under a strong UV background is a potential mechanism to form GCs.

  13. Gaseous laser targets and optical diagnostics for studying compressible hydrodynamic instabilities

    SciTech Connect

    Edwards, J M; Robey, H; Mackinnon, A

    2001-06-29

    Explore the combination of optical diagnostics and gaseous targets to obtain important information about compressible turbulent flows that cannot be derived from traditional laser experiments for the purposes of V and V of hydrodynamics models and understanding scaling. First year objectives: Develop and characterize blast wave-gas jet test bed; Perform single pulse shadowgraphy of blast wave interaction with turbulent gas jet as a function of blast wave Mach number; Explore double pulse shadowgraphy and image correlation for extracting velocity spectra in the shock-turbulent flow interaction; and Explore the use/adaptation of advanced diagnostics.

  14. Hydrodynamics of rotating stars and close binary interactions: Compressible ellipsoid models

    NASA Technical Reports Server (NTRS)

    Lai, Dong; Rasio, Frederic A.; Shapiro, Stuart L.

    1994-01-01

    We develop a new formalism to study the dynamics of fluid polytropes in three dimensions. The stars are modeled as compressible ellipsoids, and the hydrodynamic equations are reduced to a set of ordinary differential equations for the evolution of the principal axes and other global quantities. Both viscous dissipation and the gravitational radiation reaction are incorporated. We establish the validity of our approximations and demonstrate the simplicity and power of the method by rederiving a number of known results concerning the stability and dynamical oscillations of rapidly rotating polytropes. In particular, we present a generalization to compressible fluids of Chandrasekhar's classical results for the secular and dynamical instabilities of incompressible Maclaurin spheroids. We also present several applications of our method to astrophysical problems of great current interest, such as the tidal disruption of a star by a massive black hole, the coalescence of compact binaries driven by the emission of gravitational waves, and the development of instabilities in close binary systems.

  15. Implementation of the Turn Function Method in a three-dimensional, parallelized hydrodynamics code

    NASA Astrophysics Data System (ADS)

    Orourke, P. J.; Fairfield, M. S.

    1992-08-01

    The implementation of the Turn Function Method in KIVA-F90, a version of the KIVA computer program written in the FORTRAN 90 programming language that is used on some massively parallel computers is described. The Turn Function Method solves both linear momentum and vorticity equations in numerical calculations of compressible fluid flow. Solving a vorticity equation allows vorticity to be both conserved and transported more accurately than in traditional methods for computing compressible flow. This first implementation of the Turn Function Method in a three-dimensional hydrodynamics code involved some modification of the original method and some numerical difference approximations. In particular, a penalty method is used to keep the divergence of the computed vorticity field close to zero. Difference operators are also defined in such a way that the finite difference analog of del(del x u) = 0 is exactly satisfied. Three example problems show the increased computational cost and the accuracy to be gained by using the Turn Function Method in calculations of flows with rotational motion. Use of the Method can increase by 60 percent the computational times of the Euler equation solver in KIVA-F90, but it is concluded that this increased cost is justified by the increased accuracy.

  16. The core helium flash revisited. II. Two and three-dimensional hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K.

    2009-07-01

    Context: We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations. Aims: In a previous study we found that the temporal evolution and the properties of the convection inferred from two-dimensional hydrodynamic studies are similar to those predicted by quasi-hydrostatic stellar evolutionary calculations. However, as vorticity is conserved in axisymmetric flows, two-dimensional simulations of convection are characterized by incorrect dominant spatial scales and exaggerated velocities. Here, we present three-dimensional simulations that eliminate the restrictions and flaws of two-dimensional models and that provide a geometrically unbiased insight into the hydrodynamics of the core helium flash. In particular, we study whether the assumptions and predictions of stellar evolutionary calculations based on the mixing-length theory can be confirmed by hydrodynamic simulations. Methods: We used a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a 1.25 M⊙ Pop I star. Results: Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are lower than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree more closely with the predictions of mixing length theory. Our hydrodynamic simulations show the turbulent entrainment that leads to a growth of the convection zone on a dynamic time scale. In contrast to mixing length theory, the outer part of the convection zone is characterized by a subadiabatic temperature gradient.

  17. Secondary three-dimensional instability in compressible boundary layers

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.

    1989-01-01

    Three dimensional linear secondary instability theory is extended for compressible boundary layers on a flat plate in the presence of finite amplitude Tollmien-Schlichting waves. The focus is on principal parametric resonance responsible for strong growth of subharmonics in low disturbance environment.

  18. A 3-dimensional mass conserving element for compressible flows

    NASA Technical Reports Server (NTRS)

    Fix, G.; Suri, M.

    1985-01-01

    A variety of finite element schemes has been used in the numerical approximation of compressible flows particularly in underwater acoustics. In many instances instabilities have been generated due to the lack of mass conservation. Two- and three-dimensional elements are developed which avoid these problems.

  19. Magneto-hydrodynamic calculation of magnetic flux compression using imploding cylindrical liners

    NASA Astrophysics Data System (ADS)

    Zhao, Jibo; Sun, Chengwei; Gu, Zhuowei

    2015-06-01

    Based on the one-dimensional elastic-plastic reactive hydrodynamic code SSS, the one-dimensional magneto-hydrodynamics code SSS/MHD is developed successfully, and calculation is carried for cylindrical magneto cumulative generators (MC-1 device). The magnetic field diffusion into liner and sample tuber is analyzed, and the result shows that the maximum value of magnetic induction intensity to cavity 0.2 mm in liner is only sixteen Tesla, while the one in sample tuber is several hundred Tesla, which is caused by balancing of electromagnetism force and imploding one for the different velocity of liner and sample tuber. The curves of magnetic induction intensity on axes of cavity and the velocity history on the wall of sample tuber are calculated, which accord with the experiment results. The works in this paper account for that code SSS/MHD can be applied in experiment configures of detonation, shock and electromagnetism load and improve of parameter successfully. The experiment data can be estimated, analyzed and checked validly, and the physics course of correlative device can be understood deeply, according to SSS/MHD. This work was supported by the special funds of the National Natural Science Foundation of China under Grant 11176002.

  20. A one-dimensional hydrodynamic model for pressures induced near the coating-water interface during laser shock peening

    NASA Astrophysics Data System (ADS)

    Wu, Benxin; Shin, Yung C.

    2007-01-01

    In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascal, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. However, self-closed models with spatial distribution considerations for the induced pressures near the coating-water interface in LSP are rarely reported in literature. In this paper, a self-closed model is developed by numerically solving the one-dimensional hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce the one-dimensional spatial distributions of the material responses near the water-coating interface in LSP. The model-predicted pressures have been compared with experimental measurements under a variety of conditions typical for LSP, and good agreements have been found for both the transient pressure history and the peak pressure magnitude.

  1. A 2-dimensional MHD code & survey of the ``buckling'' phenomenon in cylindrical magnetic flux compression experiments

    NASA Astrophysics Data System (ADS)

    Xiao, Bo; Wang, Ganghua; Gu, Zhuowei; Computational Physics Team

    2015-11-01

    We made a 2-dimensional magneto-hydrodynamics Lagrangian code. The code handles two kinds of magnetic configuration, a (x-y) plane with z-direction magnetic field Bz and a (r-z) plane with θ-direction magnetic field Bθ. The solving of the MHD equations is split into a pure dynamical step (i.e., ideal MHD) and a diffusion step. In the diffusion step, the Joule heat is calculated with a numerical scheme based on an specific form of the Joule heat production equation, ∂eJ/∂t = ∇ . (η/μ0 º × (∇ × º)) -∂/∂t (1/2μ0 B2) , where the term ∂/∂t (1/2μ0 B2) is the magnetic field energy variation caused solely by diffusion. This scheme insures the equality of the total Joule heat produced and the total electromagnetic energy lost in the system. Material elastoplasticity is considered in the code. An external circuit is coupled to the magneto-hydrodynamics and a detonation module is also added to enhance the code's ability for simulating magnetically-driven compression experiments. As a first application, the code was utilized to simulate a cylindrical magnetic flux compression experiment. The origin of the ``buckling'' phenomenon observed in the experiment is explored.

  2. CASTRO: A New AMR Radiation-Hydrodynamics Code for Compressible Astrophysics

    NASA Astrophysics Data System (ADS)

    Almgren, Ann; Bell, J.; Day, M.; Howell, L.; Joggerst, C.; Myra, E.; Nordhaus, J.; Singer, M.; Zingale, M.

    2010-01-01

    CASTRO is a new, multi-dimensional, Eulerian AMR radiation-hydrodynamics code designed for astrophysical simulations. The code includes routines for various equations of state and nuclear reaction networks, and can be used with Cartesian, cylindrical or spherical coordinates. Time integration of the hydrodynamics equations is based on a higher-order, unsplit Godunov scheme. Self-gravity can be calculated on the adaptive hierarchy using a simple monopole approximation or a full Poisson solve for the potential. CASTRO includes gray and multigroup radiation diffusion. Multi-species neutrino diffusion for supernovae is nearing completion. The adaptive framework of CASTRO is based on an time-evolving hierarchy of nested rectangular grids with refinement in both space and time; the entire implementation is designed to run on thousands of processors. We describe in more detail how CASTRO is implemented and can be used for a number of different simulations. Our initial applications of CASTRO include Type Ia and Type II supernovae. This work has been supported by the SciDAC Program of the DOE Office of Mathematics, Information, and Computational Sciences under contracts No. DE-AC02-05CH11231 (LBNL), No. DE-FC02-06ER41438 (UCSC), and No. DE-AC52-07NA27344 (LLNL); and LLNL contracts B582735 and B574691(Stony Brook). Calculations shown were carried out on Franklin at NERSC.

  3. Three-dimensional compressible and stretchable conductive composites.

    PubMed

    Yu, You; Zeng, Jifang; Chen, Chaojian; Xie, Zhuang; Guo, Ruisheng; Liu, Zhilu; Zhou, Xuechang; Yang, Yong; Zheng, Zijian

    2014-02-01

    Three-dimensional (3D) conductive composites with remarkable flexibility, compressibility, and stretchability are fabricated by solution deposition of thin metal coatings on chemically modified, macroscopically continuous, 3D polyurethane sponges, followed by infiltration of the metallic sponges with polydimethylsiloxane (PDMS). These low-cost conductive composites are used as high-performance interconnects for flexible and stretchable light-emitting diode (LED) arrays, even with severe surface abrasion or cutting. PMID:24307070

  4. Developing a weakly compressible smoothed particle hydrodynamics model for biological flows

    NASA Astrophysics Data System (ADS)

    Vasyliv, Yaroslav; Alexeev, Alexander

    2014-11-01

    Smoothed Particle Hydrodynamics (SPH) is a meshless particle method originally developed for astrophysics applications in 1977. Over the years, limitations of the original formulations have been addressed by different groups to extend the domain of SPH application. In biologically relevant internal flows, two of the several challenges still facing SPH are 1) treatment of inlet, outlet, and no slip boundary conditions and 2) treatment of second derivatives present in the viscous terms. In this work, we develop a 2D weakly compressible SPH (WCSPH) for simulating viscous internal flows which incorporates some of the recent advancements made by groups in the above two areas. The method is validated against several analytical and experimental benchmark solutions for both steady and unsteady laminar flows. In particular, the 2013 U.S. Food and Drug Administration benchmark test case for medical devices - steady forward flow through a nozzle with a sudden contraction and conical diffuser - is simulated for different Reynolds numbers in the laminar region and results are validated against the published experimental and CFD datasets. Support from the National Science Foundation Graduate Research Fellowship Program (NSF GRFP) is gratefully acknowledged.

  5. ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT

    EPA Science Inventory

    This technical report describes a new sediment transport model and the supporting post-processor, and sampling procedures for sediments in streams. Specifically, the following items are described herein:

    EFDC1D - This is a new one-dimensional hydrodynamic and sediment tr...

  6. USING TWO-DIMENSIONAL HYDRODYNAMIC MODELS AT SCALES OF ECOLOGICAL IMPORTANCE. (R825760)

    EPA Science Inventory

    Modeling of flow features that are important in assessing stream habitat conditions has been a long-standing interest of stream biologists. Recently, they have begun examining the usefulness of two-dimensional (2-D) hydrodynamic models in attaining this objective. Current modelin...

  7. One-dimensional hydrodynamic model generating a turbulent cascade

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takeshi; Sakajo, Takashi

    2016-05-01

    As a minimal mathematical model generating cascade analogous to that of the Navier-Stokes turbulence in the inertial range, we propose a one-dimensional partial-differential-equation model that conserves the integral of the squared vorticity analog (enstrophy) in the inviscid case. With a large-scale random forcing and small viscosity, we find numerically that the model exhibits the enstrophy cascade, the broad energy spectrum with a sizable correction to the dimensional-analysis prediction, peculiar intermittency, and self-similarity in the dynamical system structure.

  8. Dimensional similitude and the hydrodynamics of three- phase fluidized beds

    NASA Astrophysics Data System (ADS)

    Safoniuk, Michael

    It is proposed that scaling of three-phase fluidized bed hydrodynamics can be carried out based on geometric similarity and matching of a set of five dimensionless groups: (i)the M-group, M = g.Δρ.μ L4/(ρL2.σ 3); (ii)an Eötvös number, Eo = g.Δρ.d p2/σ (iii)the liquid Reynolds number, Re L = ρL.dp.UL/μ L; (iv)a density ratio, βd = ρp/ρ L; and (v)a superficial velocity ratio, βu = U g/UL. These were varied in an experimental study where four dimensionless hydrodynamic parameters were measured: (i)gas hold-up, ɛ g; (ii)bed expansion ratio, βbe (iii)the ratio of mean bubble diameter to particle diameter, db/dp ; and (iv)the ratio of mean bubble rise velocity to gas superficial velocity, Ub/Ug. This approach was validated experimentally by matching the dimensionless operating conditions from a kerosene-nitrogen-ceramic three-phase system with those in an aqueous magnesium sulphate solution-air-aluminum particle fluidized bed. There was good agreement between the gas hold-ups and bed expansion ratios in the two systems. A pilot-plant scale cold-flow co-current upwards-flowing three-phase fluidized bed column of inside diameter 292 mm was built and operated using three different liquids (tap water, an aqueous 44 mass % glycerol solution, and an aqueous 60 mass % glycerol solution), air, and cylindrical aluminum particles of diameter 4 mm and length 10 mm. The fluids and solids were carefully selected to result in dimensionless group values in the range of those of an industrial hydroprocessor. Specially built conductivity probes and pressure transducers were used to measure the hydrodynamic properties for different gas and liquid superficial velocities. Special attention was required to provide for drift and calibration when recording and analyzing data from the conductivity probes. Gas hold-ups were in the range of 5 to 20% by volume and were correlated as a function of liquid-phase Reynolds number and superficial velocity ratio. The gas hold-ups were a

  9. Three Dimensional Simulations of Compressible Hall MHD Plasmas

    SciTech Connect

    Shaikh, Dastgeer; Shukla, P. K.

    2008-10-15

    We have developed three dimensional, time dependent, compressible, non-adiabatic, driven and massively parallelized Hall magnetohydrodynamic (MHD) simulations to investigate turbulent spectral cascades in a regime where characteristic lengthscales associated with plasma fluctuations are smaller than ion gyro radii. Such regime is ubiquitously present in solar wind and many other collisionless space plasmas. Particularly in the solar wind, the high time resolution databases identify a spectral break at the end of MHD inertial range spectrum that corresponds to a high frequency regime. In the regime, turbulent cascades cannot be explained by the usual MHD models. With the help of our 3D Hall MHD code, we find that characteristic turbulent interactions in the high frequency regime evolve typically on kinetic Alfven time scales. The turbulent fluctuation associated with kinetic Alfven interactions are compressive and anisotropic and possess equipartition of kinetic and magnetic energies.

  10. Three-dimensional hydrodynamic modeling of a bubbling fluidized bed

    SciTech Connect

    Gamwo, I.K.; Soong, Y.; Gidaspow, D.; Lyczkowski, R.W.

    1995-12-31

    A well-posed three-dimensional model for bed dynamics was developed starting from an ill-posed model. The new model has predicted a roughly-spheroidal bubble shape and computed porosity distributions consistent with experimental observations with no disturbing ``fountain`` as predicted by the earlier model. The model can be applied to a variety of gas-solids flows of practical interest such as fluidization, pneumatic conveying, and two-phase jets, as well as liquid-solids flows.

  11. Three-Dimensional Hydrodynamic Simulations of Collapsing Prolate Clouds

    NASA Astrophysics Data System (ADS)

    Nelson, R. P.; Papaloizou, J. C. B.

    1993-12-01

    We present the results of collapse calculations for elongated clouds performed using the numerical method of smoothed particle hydrodynamics (SPH). The clouds considered are isothermal, prolate spheroids with different axial ratios (a/b). Results are obtained for different values of a/b and mbarL, the mean mass per unit length. It is found that initially uniform clouds undergo fragmentation when the collapse is preferentially down on to the major axis, due to the intrinsic instability of a linear configuration. This occurs when the value of mbarL is sufficiently large. A criterion for elongated clouds to undergo linear collapse is derived using the tensor virial theorem, and it is found that the numerically obtained value of mbarL for which fragmentation occurs corresponds closely to that expected from analytical considerations. The addition of small density perturbations simply results in clouds that fragment more easily, particularly for cases in which a/b is close to unity. Previous calculations, presented by other authors for the case of finite cylinders, show that clouds with cylindrical geometries are highly unstable to the formation of two fragments that occur at the ends of the cylinder. We find that collapsing, prolate spheroids show qualitatively different behaviour, with no preferred tendency to form fragments at the ends of the cloud. Instead fragmentation appears to occur more readily towards the centre of the cloud where the local mass per unit length is greatest. Our implementation of SPH employs spatially variable smoothing lengths, h. In order to obtain a Hamiltonian system, we incorporate terms involving the spatial variability of h in the particle equations of motion, not included in previous implementations. We find that inclusion of these ∇h terms results in much improved energy conservation, but has little effect on the qualitative outcome of the calculations presented here. (fset 'queer "∇")

  12. A Two-Dimensional Compressible Gas Flow Code

    Energy Science and Technology Software Center (ESTSC)

    1995-03-17

    F2D is a general purpose, two dimensional, fully compressible thermal-fluids code that models most of the phenomena found in situations of coupled fluid flow and heat transfer. The code solves momentum, continuity, gas-energy, and structure-energy equations using a predictor-correction solution algorithm. The corrector step includes a Poisson pressure equation. The finite difference form of the equation is presented along with a description of input and output. Several example problems are included that demonstrate the applicabilitymore » of the code in problems ranging from free fluid flow, shock tubes and flow in heated porous media.« less

  13. Plasmas in particle accelerators: a hydrodynamic model of three-dimensional electrostatic instabilities

    SciTech Connect

    Mark, J.W.K.; Krafft, G.A.; Wang, T.S.F.

    1981-12-01

    A hydrodynamic model is used to help isolate possible three dimensional space charge instabilities in beam plasmas of concern in designing heavy ion accelerators for inertial confinement fusion energy applications. The model provides an economic means for searching the large parameter space relevant to problems in which coupling of longitudinal and transverse motions is allowed. It is shown that the equilibrium axial hydrodynamic pressure of the beam plasma has a significant effect on the stability boundaries of a two-rotating-stream instability. When considering the resistive wall effect, this model shows a kink instability. The growth rate of some modes could be enhanced by increasing the equilibrium axial pressure.

  14. Multi-dimensional high-order numerical schemes for Lagrangian hydrodynamics

    SciTech Connect

    Dai, William W; Woodward, Paul R

    2009-01-01

    An approximate solver for multi-dimensional Riemann problems at grid points of unstructured meshes, and a numerical scheme for multi-dimensional hydrodynamics have been developed in this paper. The solver is simple, and is developed only for the use in numerical schemes for hydrodynamics. The scheme is truely multi-dimensional, is second order accurate in both space and time, and satisfies conservation laws exactly for mass, momentum, and total energy. The scheme has been tested through numerical examples involving strong shocks. It has been shown that the scheme offers the principle advantages of high-order Codunov schemes; robust operation in the presence of very strong shocks and thin shock fronts.

  15. On two-dimensional flows of compressible fluids

    NASA Technical Reports Server (NTRS)

    Bergman, Stefan

    1945-01-01

    This report is devoted to the study of two-dimensional steady motion of a compressible fluid. It is shown that the complete flow pattern around a closed obstacle cannot be obtained by the method of Chaplygin. In order to overcome this difficulty, a formula for the stream-function of a two-dimensional subsonic flow is derived. The formula involves an arbitrary function of a complex variable and yields all possible subsonic flow patterns of certain types. Conditions are given so that the flow pattern in the physical plane will represent a flow around a closed curve. The formula obtained can be employed for the approximate determination of a subsonic flow around an obstacle. The method can be extended to partially supersonic flows.

  16. Three-dimensional active imaging using compressed gating

    NASA Astrophysics Data System (ADS)

    Dai, Huidong; He, Weiji; Miao, Zhuang; Chen, Yunfei; Gu, Guohua

    2013-09-01

    Due to the numerous applications employed 3D data such as target detection and recognition, three-dimensional (3D) active imaging draws great interest recently. Employing a pulsed laser as the illumination source and an intensified sensor as the image sensor, the 3D active imaging method emits and then records laser pulses to infer the distance between the target and the sensor. One of the limitations of the 3D active imaging is that acquiring depth map with high depth resolution requires a full range sweep, as well as a large number of detections, which limits the detection speed. In this work, a compressed gating method combining the 3D active imaging and compressive sensing (CS) is proposed on the basis of the random gating method to achieve the depth map reconstruction from a significantly reduced number of detections. Employing random sequences to control the sensor gate, this method estimates the distance and reconstructs the depth map in the framework of CS. A simulation was carried out to estimate the performance of the proposed method. A scene generated by the 3ds Max was employed as target and a reconstruction algorithm was used to recover the depth map in the simulation. The simulation results have shown that the proposed method can reconstruct the depth map with slight reconstruction error using as low as 7% detections that the conventional method requires and achieve perfect reconstruction from about 10% detections under the same depth resolution. It has also indicated that the number of detections required is affected by depth resolution, noise generated by a variety of reasons and complexity of the target scene. According to the simulation results, the compressed gating method is able to be used in the case of long range with high depth resolution and robust to various types of noise. In addition, the method is able to be used for multiple-return signals measurement without increase in the number of detections.

  17. Parallelization of a three-dimensional compressible transition code

    NASA Technical Reports Server (NTRS)

    Erlebacher, G.; Hussaini, M. Y.; Bokhari, Shahid H.

    1990-01-01

    The compressible, three-dimensional, time-dependent Navier-Stokes equations are solved on a 20 processor Flex/32 computer. The code is a parallel implementation of an existing code operational on the Cray-2 at NASA Ames, which performs direct simulations of the initial stages of the transition process of wall-bounded flow at supersonic Mach numbers. Spectral collocation in all three spatial directions (Fourier along the plate and Chebyshev normal to it) ensures high accuracy of the flow variables. By hiding most of the parallelism in low-level routines, the casual user is shielded from most of the nonstandard coding constructs. Speedups of 13 out of a maximum of 16 are achieved on the largest computational grids.

  18. Compressibility sum rule for the two-dimensional electron gas.

    PubMed

    Das, M P; Golden, K I; Green, F

    2001-07-01

    The authors establish formulas for the isothermal compressibility and long-wavelength static density-density response function of a weakly correlated two-dimensional electron gas in the 1

  19. Three-dimensional lattice Boltzmann model for compressible flows.

    PubMed

    Sun, Chenghai; Hsu, Andrew T

    2003-07-01

    A three-dimensional compressible lattice Boltzmann model is formulated on a cubic lattice. A very large particle-velocity set is incorporated in order to enable a greater variation in the mean velocity. Meanwhile, the support set of the equilibrium distribution has only six directions. Therefore, this model can efficiently handle flows over a wide range of Mach numbers and capture shock waves. Due to the simple form of the equilibrium distribution, the fourth-order velocity tensors are not involved in the formulation. Unlike the standard lattice Boltzmann model, no special treatment is required for the homogeneity of fourth-order velocity tensors on square lattices. The Navier-Stokes equations were recovered, using the Chapman-Enskog method from the Bhatnagar-Gross-Krook (BGK) lattice Boltzmann equation. The second-order discretization error of the fluctuation velocity in the macroscopic conservation equation was eliminated by means of a modified collision invariant. The model is suitable for both viscous and inviscid compressible flows with or without shocks. Since the present scheme deals only with the equilibrium distribution that depends only on fluid density, velocity, and internal energy, boundary conditions on curved wall are easily implemented by an extrapolation of macroscopic variables. To verify the scheme for inviscid flows, we have successfully simulated a three-dimensional shock-wave propagation in a box and a normal shock of Mach number 10 over a wedge. As an application to viscous flows, we have simulated a flat plate boundary layer flow, flow over a cylinder, and a transonic flow over a NACA0012 airfoil cascade. PMID:12935242

  20. Three dimensional inviscid compressible calculations around axial flow turbine blades

    NASA Astrophysics Data System (ADS)

    Fourmaux, Antoine; Petot, Bertrand

    1991-12-01

    The application of a three dimensional (3D) method to the prediction of steady inviscid compressible flows in highly loaded stator bladings is presented. The complete set of Euler equations is solved by a finite difference method using a time marching two step Lax-Wendorff algorithm. The treatment of the boundary conditions is based on the use of the characteristic relations. This technique offers a great versatility and allows to prescribe conditions close to the physics of flows encountered in turbomachines. The code was adapted in order to build a 3D design tool able to run in different types of turbine blade geometries. Two types of multidomain structured meshes were tested (H+0+H and H+C). The H+C type of grid was finally choosen for industrial applications. Two applications to turbine nozzles are presented. The first is a low pressure turbine vane with evolutive flow path outer diameter. The results demonstrate the ability to predict flow features that cannot be computed via the classical two dimensional approach. The second is a high pressure inlet guide vane at transonic conditions. The strong radial evolution of pressure distribution and the trailing edge flow pattern are correctly predicted.

  1. Two dimensional hydrodynamic simulation of high pressures induced by high power nanosecond laser-matter interactions under water

    NASA Astrophysics Data System (ADS)

    Wu, Benxin; Shin, Yung C.

    2007-05-01

    In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the pressure generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the induced pressures near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release wave on pressure spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.

  2. Two dimensional hydrodynamic simulation of high pressures induced by high power nanosecond laser-matter interactions under water

    SciTech Connect

    Wu, Benxin; Shin, Yung C.

    2007-05-15

    In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the pressure generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the induced pressures near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release wave on pressure spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.

  3. A 3+1 dimensional viscous hydrodynamic code for relativistic heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Karpenko, Iu.; Huovinen, P.; Bleicher, M.

    2014-11-01

    We describe the details of 3+1 dimensional relativistic hydrodynamic code for the simulations of quark-gluon/hadron matter expansion in ultra-relativistic heavy ion collisions. The code solves the equations of relativistic viscous hydrodynamics in the Israel-Stewart framework. With the help of ideal-viscous splitting, we keep the ability to solve the equations of ideal hydrodynamics in the limit of zero viscosities using a Godunov-type algorithm. Milne coordinates are used to treat the predominant expansion in longitudinal (beam) direction effectively. The results are successfully tested against known analytical relativistic inviscid and viscous solutions, as well as against existing 2+1D relativistic viscous code. Catalogue identifier: AETZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETZ_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 13 825 No. of bytes in distributed program, including test data, etc.: 92 750 Distribution format: tar.gz Programming language: C++. Computer: any with a C++ compiler and the CERN ROOT libraries. Operating system: tested on GNU/Linux Ubuntu 12.04 x64 (gcc 4.6.3), GNU/Linux Ubuntu 13.10 (gcc 4.8.2), Red Hat Linux 6 (gcc 4.4.7). RAM: scales with the number of cells in hydrodynamic grid; 1900 Mbytes for 3D 160×160×100 grid. Classification: 1.5, 4.3, 12. External routines: CERN ROOT (http://root.cern.ch), Gnuplot (http://www.gnuplot.info/) for plotting the results. Nature of problem: relativistic hydrodynamical description of the 3-dimensional quark-gluon/hadron matter expansion in ultra-relativistic heavy ion collisions. Solution method: finite volume Godunov-type method. Running time: scales with the number of hydrodynamic cells; typical running times on Intel(R) Core(TM) i7-3770 CPU @ 3.40 GHz, single thread mode, 160

  4. Development of a Three-Dimensional PSE Code for Compressible Flows: Stability of Three-Dimensional Compressible Boundary Layers

    NASA Technical Reports Server (NTRS)

    Balakumar, P.; Jeyasingham, Samarasingham

    1999-01-01

    A program is developed to investigate the linear stability of three-dimensional compressible boundary layer flows over bodies of revolutions. The problem is formulated as a two dimensional (2D) eigenvalue problem incorporating the meanflow variations in the normal and azimuthal directions. Normal mode solutions are sought in the whole plane rather than in a line normal to the wall as is done in the classical one dimensional (1D) stability theory. The stability characteristics of a supersonic boundary layer over a sharp cone with 50 half-angle at 2 degrees angle of attack is investigated. The 1D eigenvalue computations showed that the most amplified disturbances occur around x(sub 2) = 90 degrees and the azimuthal mode number for the most amplified disturbances range between m = -30 to -40. The frequencies of the most amplified waves are smaller in the middle region where the crossflow dominates the instability than the most amplified frequencies near the windward and leeward planes. The 2D eigenvalue computations showed that due to the variations in the azimuthal direction, the eigenmodes are clustered into isolated confined regions. For some eigenvalues, the eigenfunctions are clustered in two regions. Due to the nonparallel effect in the azimuthal direction, the eigenmodes are clustered into isolated confined regions. For some eigenvalues, the eigenfunctions are clustered in two regions. Due to the nonparallel effect in the azimuthal direction, the most amplified disturbances are shifted to 120 degrees compared to 90 degrees for the parallel theory. It is also observed that the nonparallel amplification rates are smaller than that is obtained from the parallel theory.

  5. High-energy Particle Transport in Three-dimensional Hydrodynamic Models of Colliding-wind Binaries

    NASA Astrophysics Data System (ADS)

    Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O.; Dubus, G.

    2014-02-01

    Massive stars in binary systems (such as WR 140, WR 147, or η Carinae) have long been regarded as potential sources of high-energy γ-rays. The emission is thought to arise in the region where the stellar winds collide and produce relativistic particles that subsequently might be able to emit γ-rays. Detailed numerical hydrodynamic simulations have already offered insight into the complex dynamics of the wind collision region (WCR), while independent analytical studies, albeit with simplified descriptions of the WCR, have shed light on the spectra of charged particles. In this paper, we describe a combination of these two approaches. We present a three-dimensional hydrodynamical model for colliding stellar winds and compute spectral energy distributions of relativistic particles for the resulting structure of the WCR. The hydrodynamic part of our model incorporates the line-driven acceleration of the winds, gravity, orbital motion, and the radiative cooling of the shocked plasma. In our treatment of charged particles, we consider diffusive shock acceleration in the WCR and the subsequent cooling via inverse Compton losses (including Klein-Nishina effects), bremsstrahlung, collisions, and other energy loss mechanisms.

  6. Three-dimensional simulations of dilute and concentrated suspensions using smoothed particle hydrodynamics

    NASA Astrophysics Data System (ADS)

    Vázquez-Quesada, Adolfo; Bian, Xin; Ellero, Marco

    2016-04-01

    A three-dimensional model for a suspension of rigid spherical particles in a Newtonian fluid is presented. The solvent is modeled with smoothed particle hydrodynamics method, which takes into account exactly the long-range multi-body hydrodynamic interactions between suspended spheres. Short-range lubrication forces which are necessary to simulate concentrated suspensions, are introduced pair-wisely based on the analytical solution of Stokes equations for approaching/departing objects. Given that lubrication is singular at vanishing solid particle separations, an implicit splitting integration scheme is used to obtain accurate results and at the same time to avoid prohibitively small simulation time steps. Hydrodynamic interactions between solid particles, at both long-range and short-range limits, are verified against theory in the case of two approaching spheres in a quiescent medium and under bulk shear flow, where good agreements are obtained. Finally, numerical results for the suspension viscosity of a many-particle system are shown and compared with analytical solutions available in the dilute and semi-dilute case as well as with previous numerical results obtained in the concentrated limit.

  7. Effect of Hydrodynamic Interactions on Self-Diffusion of Quasi-Two-Dimensional Colloidal Hard Spheres

    NASA Astrophysics Data System (ADS)

    Thorneywork, Alice L.; Rozas, Roberto E.; Dullens, Roel P. A.; Horbach, Jürgen

    2015-12-01

    We compare experimental results from a quasi-two-dimensional colloidal hard sphere fluid to a Monte Carlo simulation of hard disks with small particle displacements. The experimental short-time self-diffusion coefficient DS scaled by the diffusion coefficient at infinite dilution, D0, strongly depends on the area fraction, pointing to significant hydrodynamic interactions at short times in the experiment, which are absent in the simulation. In contrast, the area fraction dependence of the experimental long-time self-diffusion coefficient DL/D0 is in quantitative agreement with DL/D0 obtained from the simulation. This indicates that the reduction in the particle mobility at short times due to hydrodynamic interactions does not lead to a proportional reduction in the long-time self-diffusion coefficient. Furthermore, the quantitative agreement between experiment and simulation at long times indicates that hydrodynamic interactions effectively do not affect the dependence of DL/D0 on the area fraction. In light of this, we discuss the link between structure and long-time self-diffusion in terms of a configurational excess entropy and do not find a simple exponential relation between these quantities for all fluid area fractions.

  8. Sub-micrometer-precision, three-dimensional (3D) hydrodynamic focusing via “microfluidic drifting”

    PubMed Central

    Nawaz, Ahmad Ahsan; Zhang, Xiangjun; Mao, Xiaole; Rufo, Joseph; Lin, Sz-Chin Steven; Guo, Feng; Zhao, Yanhui; Lapsley, Michael; Li, Peng; McCoy, J. Philip; Levine, Stewart J.; Huang, Tony Jun

    2014-01-01

    In this article, we demonstrate single-layered, “microfluidic drifting” based three-dimensional (3D) hydrodynamic focusing devices with particle/cell focal positioning approaching submicron precision along both lateral and vertical directions. By systematically optimizing channel geometries and sample/sheath flow rates, a series of “microfluidic drifting” based 3D hydrodynamic focusing devices with different curvature angles are designed and fabricated. Their performances are then evaluated by confocal microscopy, fast camera imaging, and side-view imaging techniques. Using a device with a curvature angle of 180°, we have achieved a standard deviation of ±0.45 µm in particle focal position and a coefficient of variation (CV) of 2.37% in flow cytometric measurements. To the best of our knowledge, this is the best CV that has been achieved by a microfluidic flow cytometry device. Moreover, the device showed the capability to distinguish 8 peaks when subjected to a stringent 8-peak rainbow calibration test, signifying the ability to perform sensitive, accurate tests similar to commercial flow cytometers. We have further tested and validated our device by detection of HEK-293 cells. With its advantages in simple fabrication (i.e., single-layered device), precise 3D hydrodynamic focusing (i.e., submicrometer precision along both lateral and vertical directions), and high detection resolution (i.e., low CV), our method could serve as an important basis for high-performance, mass-producible microfluidic flow cytometry. PMID:24287742

  9. Sub-micrometer-precision, three-dimensional (3D) hydrodynamic focusing via "microfluidic drifting".

    PubMed

    Nawaz, Ahmad Ahsan; Zhang, Xiangjun; Mao, Xiaole; Rufo, Joseph; Lin, Sz-Chin Steven; Guo, Feng; Zhao, Yanhui; Lapsley, Michael; Li, Peng; McCoy, J Philip; Levine, Stewart J; Huang, Tony Jun

    2014-01-21

    In this article, we demonstrate single-layered, "microfluidic drifting" based three-dimensional (3D) hydrodynamic focusing devices with particle/cell focal positioning approaching submicron precision along both lateral and vertical directions. By systematically optimizing channel geometries and sample/sheath flow rates, a series of "microfluidic drifting" based 3D hydrodynamic focusing devices with different curvature angles are designed and fabricated. Their performances are then evaluated using confocal microscopy, fast camera imaging, and side-view imaging techniques. Using a device with a curvature angle of 180°, we have achieved a standard deviation of ±0.45 μm in particle focal position and a coefficient of variation (CV) of 2.37% in flow cytometric measurements. To the best of our knowledge, this is the best CV that has been achieved using a microfluidic flow cytometry device. Moreover, the device showed the capability to distinguish 8 peaks when subjected to a stringent 8-peak rainbow calibration test, signifying the ability to perform sensitive, accurate tests similar to commercial flow cytometers. We have further tested and validated our device by detection of HEK-293 cells. With its advantages in simple fabrication (i.e., single-layered device), precise 3D hydrodynamic focusing (i.e., submicrometer precision along both lateral and vertical directions), and high detection resolution (i.e., low CV), our method could serve as an important basis for high-performance, mass-producible microfluidic flow cytometry. PMID:24287742

  10. Effect of Hydrodynamic Interactions on Self-Diffusion of Quasi-Two-Dimensional Colloidal Hard Spheres.

    PubMed

    Thorneywork, Alice L; Rozas, Roberto E; Dullens, Roel P A; Horbach, Jürgen

    2015-12-31

    We compare experimental results from a quasi-two-dimensional colloidal hard sphere fluid to a Monte Carlo simulation of hard disks with small particle displacements. The experimental short-time self-diffusion coefficient D(S) scaled by the diffusion coefficient at infinite dilution, D(0), strongly depends on the area fraction, pointing to significant hydrodynamic interactions at short times in the experiment, which are absent in the simulation. In contrast, the area fraction dependence of the experimental long-time self-diffusion coefficient D(L)/D(0) is in quantitative agreement with D(L)/D(0) obtained from the simulation. This indicates that the reduction in the particle mobility at short times due to hydrodynamic interactions does not lead to a proportional reduction in the long-time self-diffusion coefficient. Furthermore, the quantitative agreement between experiment and simulation at long times indicates that hydrodynamic interactions effectively do not affect the dependence of D(L)/D(0) on the area fraction. In light of this, we discuss the link between structure and long-time self-diffusion in terms of a configurational excess entropy and do not find a simple exponential relation between these quantities for all fluid area fractions. PMID:26765032

  11. High-energy particle transport in three-dimensional hydrodynamic models of colliding-wind binaries

    SciTech Connect

    Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O.; Dubus, G.

    2014-02-20

    Massive stars in binary systems (such as WR 140, WR 147, or η Carinae) have long been regarded as potential sources of high-energy γ-rays. The emission is thought to arise in the region where the stellar winds collide and produce relativistic particles that subsequently might be able to emit γ-rays. Detailed numerical hydrodynamic simulations have already offered insight into the complex dynamics of the wind collision region (WCR), while independent analytical studies, albeit with simplified descriptions of the WCR, have shed light on the spectra of charged particles. In this paper, we describe a combination of these two approaches. We present a three-dimensional hydrodynamical model for colliding stellar winds and compute spectral energy distributions of relativistic particles for the resulting structure of the WCR. The hydrodynamic part of our model incorporates the line-driven acceleration of the winds, gravity, orbital motion, and the radiative cooling of the shocked plasma. In our treatment of charged particles, we consider diffusive shock acceleration in the WCR and the subsequent cooling via inverse Compton losses (including Klein-Nishina effects), bremsstrahlung, collisions, and other energy loss mechanisms.

  12. Onset of hydrodynamic mix in high-velocity, highly compressed inertial confinement fusion implosions.

    PubMed

    Ma, T; Patel, P K; Izumi, N; Springer, P T; Key, M H; Atherton, L J; Benedetti, L R; Bradley, D K; Callahan, D A; Celliers, P M; Cerjan, C J; Clark, D S; Dewald, E L; Dixit, S N; Döppner, T; Edgell, D H; Epstein, R; Glenn, S; Grim, G; Haan, S W; Hammel, B A; Hicks, D; Hsing, W W; Jones, O S; Khan, S F; Kilkenny, J D; Kline, J L; Kyrala, G A; Landen, O L; Le Pape, S; MacGowan, B J; Mackinnon, A J; MacPhee, A G; Meezan, N B; Moody, J D; Pak, A; Parham, T; Park, H-S; Ralph, J E; Regan, S P; Remington, B A; Robey, H F; Ross, J S; Spears, B K; Smalyuk, V; Suter, L J; Tommasini, R; Town, R P; Weber, S V; Lindl, J D; Edwards, M J; Glenzer, S H; Moses, E I

    2013-08-23

    Deuterium-tritium inertial confinement fusion implosion experiments on the National Ignition Facility have demonstrated yields ranging from 0.8 to 7×10(14), and record fuel areal densities of 0.7 to 1.3 g/cm2. These implosions use hohlraums irradiated with shaped laser pulses of 1.5-1.9 MJ energy. The laser peak power and duration at peak power were varied, as were the capsule ablator dopant concentrations and shell thicknesses. We quantify the level of hydrodynamic instability mix of the ablator into the hot spot from the measured elevated absolute x-ray emission of the hot spot. We observe that DT neutron yield and ion temperature decrease abruptly as the hot spot mix mass increases above several hundred ng. The comparison with radiation-hydrodynamic modeling indicates that low mode asymmetries and increased ablator surface perturbations may be responsible for the current performance. PMID:24010449

  13. Three-dimensional Hybrid Continuum-Atomistic Simulations for Multiscale Hydrodynamics

    SciTech Connect

    Wijesinghe, S; Hornung, R; Garcia, A; Hadjiconstantinou, N

    2004-04-15

    We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such ''hybrid'' methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct Simulation Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.

  14. One-dimensional radiation-hydrodynamic simulations of imploding spherical plasma liners with detailed equation-of-state modeling

    SciTech Connect

    Davis, J. S.; Hsu, S. C.; Golovkin, I. E.; MacFarlane, J. J.; Cassibry, J. T.

    2012-10-15

    This work extends the one-dimensional radiation-hydrodynamic imploding spherical argon plasma liner simulations of Awe et al.[Phys. Plasmas 18, 072705 (2011)] by using a detailed tabular equation-of-state (EOS) model, whereas Awe et al. used a polytropic EOS model. Results using the tabular EOS model give lower stagnation pressures by a factor of 3.9-8.6 and lower peak ion temperatures compared to the polytropic EOS results. Both local thermodynamic equilibrium (LTE) and non-LTE EOS models were used in this work, giving similar results on stagnation pressure. The lower stagnation pressures using a tabular EOS model are attributed to a reduction in the liner's ability to compress arising from the energy sink introduced by ionization and electron excitation, which are not accounted for in a polytropic EOS model. Variation of the plasma liner species for the same initial liner geometry, mass density, and velocity was also explored using the LTE tabular EOS model, showing that the highest stagnation pressure is achieved with the highest atomic mass species for the constraints imposed.

  15. Implications for the electron distribution from the stationary hydrodynamic model of a one-dimensional plasma expansion into vacuum

    SciTech Connect

    Kiefer, Thomas; Schlegel, Theodor

    2012-10-15

    It is shown that the hydrodynamic model of a one-dimensional collisionless plasma expansion is contained in the kinetic description as a special case. This belongs to a specific choice for the electron distribution function. Moreover, the consequences of the use of the hydrodynamic approach regarding the temporal evolution of the electron phase space density are investigated. It turns out that only the case of a hydrodynamic description with the adiabatic constant {kappa}=3 is physically self-consistent. Numerical simulations confirm this argumentation. The analysis for the case {kappa}=3 is extended to the kinetics of a relativistic electron gas.

  16. Mechanisms and effects of mechanical compression and dimensional change in polymer electrolyte fuel cells - A review

    NASA Astrophysics Data System (ADS)

    Millichamp, Jason; Mason, Thomas J.; Neville, Tobias P.; Rajalakshmi, Natarajan; Jervis, Rhodri; Shearing, Paul R.; Brett, Daniel J. L.

    2015-06-01

    Conventional polymer electrolyte fuel cells (PEFCs) require a means of placing the series of laminar components that make up cells under mechanical compression so as to ensure effective electrical conduction, mass transport and gas-tight operation. This review describes the effect of mechanical compression and dimensional change on the components of PEFCs and reviews the range of methods used to achieve desired stack compression. The case is made for improved understanding of the mechanisms of fuel cell component compression and greater attention to the development of technological approaches for stack compression.

  17. Three-dimensional modeling of hydrodynamic processes in the St. Lucie Estuary

    NASA Astrophysics Data System (ADS)

    Ji, Zhen-Gang; Hu, Guangdou; Shen, Jian; Wan, Yongshan

    2007-06-01

    Comparing with the studies on large estuarine systems, such as the Chesapeake Bay and the San Francisco Bay, the processes of stratification and transport in small and shallow estuaries are relatively less studied. The St. Lucie Estuary (SLE) is a riverine estuary located on the east coast of south Florida. It is small and shallow, with mean depth of 2.4 m. To study the estuarine processes in the SLE, a hydrodynamic model was developed based on the Environmental Fluid Dynamics Code (EFDC) [Hamrick, J.M., 1992. A three-dimensional environmental fluid dynamics computer code: theoretical and computational aspects. The College of William and Mary, Virginia Institute of Marine Science, Special Report 317, 63 pp.]. The model was calibrated and verified using observational data obtained in 1999 and 2000, respectively. The model variables used for model data-comparisons are water elevation, velocity, temperature, and salinity. The model is then applied to study the hydrodynamic processes in the SLE. It is found that freshwater inflow plays a major role in the stratification and net flushing of the SLE. Stratification generally increases with freshwater inflow. But when the inflow is persistently large for a relatively long period, the estuary can suddenly change from very stratified to well mixed within a few tidal cycles and the stratification collapses. This finding suggests that large and persistent freshwater inflows do not always increase estuarine stratification. Instead, it may cause the stratification to collapse within a short period of time. In addition to gauged tributaries, ungauged lateral inflows can also be important to small and shallow estuaries like the SLE. Although small individually, the ungauged streams and surface runoffs can be a significant portion of the total inflow and affect salinity distribution significantly. Flushing time affects a wide range of hydrodynamic and water quality processes in the estuary. The model results indicate that commonly

  18. Three-dimensional hydrodynamic Bondi-Hoyle accretion. 1: Code validation and stationary accretors

    NASA Technical Reports Server (NTRS)

    Ruffert, Maximilian

    1994-01-01

    We investigate the hydrodynamics of three-dimensional classical Bondi-Hoyle accretion. Totally absorbing stationary spheres of varying sizes (from 10.0 down to 0.02 Bondi radii) accrete matter from a homogeneous and slightly perturbed medium, which is taken to be an ideal gas (gamma = 5/3 or 1.2). To accommodate the long-range gravitational forces, the extent of the computational volume is typically a factor of 100 larger than the radius of the accretor. We compare the numerical mass accretion rates with the theoretical predictions of Bondi, to assess the validity of the code. The hydrodynamics is modeled by the piecewise parabolic method. No energy sources (nuclear burning) or sinks (radiation, conduction) are included. The resolution in the vicinity of the accretor is increased by multiply nesting several (6-8) grids around the stationary sphere, each finer grid being a factor of 2 smaller spatially than the next coarser grid. This allows us to include a coarse model for the surface of the accretor (vacuum sphere) on the finest grid while at the same time evolving the gas on the coarser grids. The accretion rates derived numerically are in in very good agreement (to about 10% over several orders of magnitude) with the values given by Bondi for a stationary accretor within a hydrodynamic medium. However, the equations have to be changed in order to include the finite size of the accretor (in some cases very large compared to the sonic point or even to the Bondi radius).

  19. Time-dependent two-dimensional radiation hydrodynamics of accreting matter onto highly magnetized neutron stars

    SciTech Connect

    Klein, R.I. . Dept. of Astronomy Lawrence Livermore National Lab., CA California Univ., Los Angeles, CA . Inst. of Geophysics and Planetary Physics); Arons, J. . Dept. of Astronomy California Univ., Los Angeles, CA . Inst. of Geophysics and Planetary Physics CEA Centre d'Etudes Nucleaires de Saclay, 91 -

    1989-11-24

    We present for the first time, the self-consistent solution of the two-dimensional, time-dependent equations of radiation-hydrodynamics governing the accretion of matter onto the highly magnetized polar caps of luminous x-ray pulsars. The calculations show a structure in the accretion column very different from previous one-zone uniform models. We have included all the relevant magnetic field corrections to both the hydrodynamics and the radiative transport. We include a new theory for the diffusion and advection of both radiation energy density and photon number density. For initially uniformly accreting models with super-Eddington flows, we have uncovered evidence of strong radiation-driven outflowing optically thin radiation filled regions of the accretion column embedded in optically-thick inflowing plasma. The development of these photon bubbles'' have growth times on the order of a millisecond and show fluctuations on sub-millisecond timescales. The photon bubbles are likely to be a consequence of convective over-stability and may result in observable fluctuations in the emitted luminosity leading to luminosity dependent changes in the pulse profile. This may provide important new diagnostics for conditions in accreting x-ray pulsars. 13 refs., 18 figs.

  20. Time-dependent two-dimensional radiation hydrodynamics of accreting matter onto highly magnetized neutron stars

    SciTech Connect

    Klein, R.I. . Dept. of Astronomy Lawrence Livermore National Lab., CA ); Arons, J. . Dept. of Astronomy California Univ., Berkeley, CA . Dept. of Physics)

    1990-11-20

    We present for the first time, the self-consistent solution of the two-dimensional, time-dependent equations of radiation-hydrodynamics governing the accretion of matter onto the highly magnetized polar caps of luminous x-ray pulsars. The calculations show a structure in the accretion column very different from previous one-zone uniform models. We have included all the relevant magnetic field corrections to both the hydrodynamics and the radiative transport. We include a new theory for the diffusion and advection of both radiation energy density and photon number density. For initially uniformly accreting models with super-Eddington flows, we have uncovered evidence of strong radiation-driven outflowing optically thin radiation filled regions of the accretion column embedded in optically-thick inflowing plasma. We follow the evolution of these photon bubbles for several dynamical timescales. The development of these photon bubbles'' indicates growth times on the order of a millisecond and show fluctuations on sub-millisecond timescales in agreement with a linear stability analysis. The photon bubbles are a consequence of the effect of radiative heat flux on the internal gravity waves in the strongly magnetized atmosphere and may result in observable fluctuations in the emitted luminosity leading to luminosity dependent changes in the pulse profile. This may provide important new diagnostics for conditions in accreting x-ray pulsars. 19 refs., 13 figs.

  1. Shape-Controlled Synthesis of Hybrid Nanomaterials via Three-Dimensional Hydrodynamic Focusing

    PubMed Central

    2015-01-01

    Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional hydrodynamic focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF–Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, and the formation mechanisms of different structures are discussed. This simple one-step method to achieve continuous shape-tunable synthesis highlights the potential of 3D-HF in nanomaterials research. PMID:25268035

  2. Three-dimensional effects of the linear hydrodynamic instability on the plane wake flow

    NASA Astrophysics Data System (ADS)

    Mele, P.; Morganti, M.; Attili, F.

    The LINEAR hydrodynamic stability for plane shear flows considers planar disturbances super-imposed over the main flow. Squire transforms justify the use of disturbances of this kind in order to detect the critical Reynolds number. In this way the behavior of the onset of oscillations of the flow field is well described, especially for flows with a profile of the basic velocity with points of inflexion like wake profile flows. A tentative approach is pursued for the study of the behavior of the flow for a Reynolds number slightly greater than the critical value using the Squire transforms to obtain new solutions of the flow field, with disturbances neither amplified nor damped but of three-dimensional character. The two-dimensional mode is obtained as an eigenfunction of the Orr-Sommerfeld equation by an already tested Galerkin procedure. Hence the Poisson equation is solved in order to obtain the pressure field of the disturbance. The presence of more than one mode is analyzed with their influence on the two- and three-dimensional organized structures of large eddies. Numerical and experimental results are compared.

  3. Hydrodynamics of a cold one-dimensional fluid: the problem of strong shock waves

    NASA Astrophysics Data System (ADS)

    Hurtado, Pablo I.

    2005-03-01

    We study a shock wave induced by an infinitely massive piston propagating into a one-dimensional cold gas. The cold gas is modelled as a collection of hard rods which are initially at rest, so the temperature is zero. Most of our results are based on simulations of a gas of rods with binary mass distribution, and we partcularly focus on the case of spatially alternating masses. We find that the properties of the resulting shock wave are in striking contrast with those predicted by hydrodynamic and kinetic approaches, e.g., the flow-field profiles relax algebraically toward their equilibrium values. In addition, most relevant observables characterizing local thermodynamic equilibrium and equipartition decay as a power law of the distance to the shock layer. The exponents of these power laws depend non-monotonously on the mass ratio. Similar interesting dependences on the mass ratio also characterize the shock width, density and temperature overshoots, etc.

  4. Massively parallel fast elliptic equation solver for three dimensional hydrodynamics and relativity

    SciTech Connect

    Sholl, P.L.; Wilson, J.R.; Mathews, G.J.; Avila, J.H.

    1995-01-01

    Through the work proposed in this document we expect to advance the forefront of large scale computational efforts on massively parallel distributed-memory multiprocessors. We will develop tools for effective conversion to a parallel implementation of sequential numerical methods used to solve large systems of partial differential equations. The research supported by this work will involve conversion of a program which does state of the art modeling of multi-dimensional hydrodynamics, general relativity and particle transport in energetic astrophysical environments. The proposed parallel algorithm development, particularly the study and development of fast elliptic equation solvers, could significantly benefit this program and other applications involving solutions to systems of differential equations. We shall develop a data communication manager for distributed memory computers as an aid in program conversions to a parallel environment and implement it in the three dimensional relativistic hydrodynamics program discussed below; develop a concurrent system/concurrent subgrid multigrid method. Currently, five systems are approximated sequentially using multigrid successive overrelaxation. Results from an iteration cycle of one multigrid system are used in following multigrid systems iterations. We shall develop a multigrid algorithm for simultaneous computation of the sets of equations. In addition, we shall implement a method for concurrent processing of the subgrids in each of the multigrid computations. The conditions for convergence of the method will be examined. We`ll compare this technique to other parallel multigrid techniques, such as distributed data/sequential subgrids and the Parallel Superconvergent Multigrid of Frederickson and McBryan. We expect the results of these studies to offer insight and tools both for the selection of new algorithms as well as for conversion of existing large codes for massively parallel architectures.

  5. Three-dimensional compression scheme based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Yang, Wu; Xu, Hui; Liao, Mengyang

    1999-03-01

    In this paper, a 3D compression method based on separable wavelet transform is discussed in detail. The most commonly used digital modalities generate multiple slices in a single examination, which are normally anatomically or physiologically correlated to each other. 3D wavelet compression methods can achieve more efficient compression by exploring the correlation between slices. The first step is based on a separable 3D wavelet transform. Considering the difference between pixel distances within a slice and those between slices, one biorthogonal Antoninin filter bank is applied within 2D slices and a second biorthogonal Villa4 filter bank on the slice direction. Then, S+P transform is applied in the low-resolution wavelet components and an optimal quantizer is presented after analysis of the quantization noise. We use an optimal bit allocation algorithm, which, instead of eliminating the coefficients of high-resolution components in smooth areas, minimizes the system reconstruction distortion at a given bit-rate. Finally, to remain high coding efficiency and adapt to different properties of each component, a comprehensive entropy coding method is proposed, in which arithmetic coding method is applied in high-resolution components and adaptive Huffman coding method in low-resolution components. Our experimental results are evaluated by several image measures and our 3D wavelet compression scheme is proved to be more efficient than 2D wavelet compression.

  6. Numerical investigation of fluid mud motion using a three-dimensional hydrodynamic and two-dimensional fluid mud coupling model

    NASA Astrophysics Data System (ADS)

    Yang, Xiaochen; Zhang, Qinghe; Hao, Linnan

    2015-03-01

    A water-fluid mud coupling model is developed based on the unstructured grid finite volume coastal ocean model (FVCOM) to investigate the fluid mud motion. The hydrodynamics and sediment transport of the overlying water column are solved using the original three-dimensional ocean model. A horizontal two-dimensional fluid mud model is integrated into the FVCOM model to simulate the underlying fluid mud flow. The fluid mud interacts with the water column through the sediment flux, current, and shear stress. The friction factor between the fluid mud and the bed, which is traditionally determined empirically, is derived with the assumption that the vertical distribution of shear stress below the yield surface of fluid mud is identical to that of uniform laminar flow of Newtonian fluid in the open channel. The model is validated by experimental data and reasonable agreement is found. Compared with numerical cases with fixed friction factors, the results simulated with the derived friction factor exhibit the best agreement with the experiment, which demonstrates the necessity of the derivation of the friction factor.

  7. Compression Shocks in Two-Dimensional Gas Flows

    NASA Technical Reports Server (NTRS)

    Busemann, A.

    1949-01-01

    The following are arguments on the compression shocks in gas flow start with a simplified representation of the results of the study made by Th. Meyer as published in the Forschungsheft 62 of the VDI, supplemented by several amplifications for the application.In the treatment of compression shocks, the equation of energy, the equation of continuity, the momentum equation, the equation of state of the particular gas, as well as the condition Of the second law of thermodynamics that no decrease of entropy is possible in an isolated system, must be taken into consideration. The result is that, in those cases where the sudden change of state according to the second law of thermodynamics is possible, there always occurs a compression of the gas which is uniquely determined by the other conditions.

  8. Compression and Progressive Retrieval of Multi-Dimensional Sensor Data

    NASA Astrophysics Data System (ADS)

    Lorkowski, P.; Brinkhoff, T.

    2016-06-01

    Since the emergence of sensor data streams, increasing amounts of observations have to be transmitted, stored and retrieved. Performing these tasks at the granularity of single points would mean an inappropriate waste of resources. Thus, we propose a concept that performs a partitioning of observations by spatial, temporal or other criteria (or a combination of them) into data segments. We exploit the resulting proximity (according to the partitioning dimension(s)) within each data segment for compression and efficient data retrieval. While in principle allowing lossless compression, it can also be used for progressive transmission with increasing accuracy wherever incremental data transfer is reasonable. In a first feasibility study, we apply the proposed method to a dataset of ARGO drifting buoys covering large spatio-temporal regions of the world's oceans and compare the achieved compression ratio to other formats.

  9. A variational principle for compressible fluid mechanics: Discussion of the multi-dimensional theory

    NASA Technical Reports Server (NTRS)

    Prozan, R. J.

    1982-01-01

    The variational principle for compressible fluid mechanics previously introduced is extended to two dimensional flow. The analysis is stable, exactly conservative, adaptable to coarse or fine grids, and very fast. Solutions for two dimensional problems are included. The excellent behavior and results lend further credence to the variational concept and its applicability to the numerical analysis of complex flow fields.

  10. A two-dimensional Segmented Boundary Algorithm for complex moving solid boundaries in Smoothed Particle Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Khorasanizade, Sh.; Sousa, J. M. M.

    2016-03-01

    A Segmented Boundary Algorithm (SBA) is proposed to deal with complex boundaries and moving bodies in Smoothed Particle Hydrodynamics (SPH). Boundaries are formed in this algorithm with chains of lines obtained from the decomposition of two-dimensional objects, based on simple line geometry. Various two-dimensional, viscous fluid flow cases have been studied here using a truly incompressible SPH method with the aim of assessing the capabilities of the SBA. Firstly, the flow over a stationary circular cylinder in a plane channel was analyzed at steady and unsteady regimes, for a single value of blockage ratio. Subsequently, the flow produced by a moving circular cylinder with a prescribed acceleration inside a plane channel was investigated as well. Next, the simulation of the flow generated by the impulsive start of a flat plate, again inside a plane channel, has been carried out. This was followed by the study of confined sedimentation of an elliptic body subjected to gravity, for various density ratios. The set of test cases was completed with the simulation of periodic flow around a sunflower-shaped object. Extensive comparisons of the results obtained here with published data have demonstrated the accuracy and effectiveness of the proposed algorithms, namely in cases involving complex geometries and moving bodies.

  11. Two-dimensional hydrodynamic flood modelling for populated valley areas of Russian rivers

    NASA Astrophysics Data System (ADS)

    Belikov, V. V.; Krylenko, I. N.; Alabyan, A. M.; Sazonov, A. A.; Glotko, A. V.

    2015-06-01

    Results of flood modelling for three cities located in different parts of Russia: (1) Veliky Ustyug at the Northern Dvina river (Europe); (2) Mezhdurechensk at the Tom river (Siberia); and (3) Blagoveschensk at the Amur river (Far East) are presented. The two-dimensional hydrodynamic model of flow in channels and on floodplain STREAM_2D on the basis of the numerical solution of two-dimensional Saint-Venant equations on a hybrid curvilinear quadrangular and rectangular mesh was used for the simulations. Verification of the model through a comparison of simulated inundated areas with outlines of flooded zones from satellite images for known hydrologic situations demonstrate close correspondence (relative errors of 7-12% in terms of the area for peaks of the analysed floods). Analyses of embankment influence of large-scale levees on the water flow demonstrate that, in some cases, water levels could rise by more than 1 m and the patterns of the flooding zones could significantly differ.

  12. Impacts of Rotation on Three-dimensional Hydrodynamics of Core-collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Nakamura, Ko; Kuroda, Takami; Takiwaki, Tomoya; Kotake, Kei

    2014-09-01

    We perform a series of simplified numerical experiments to explore how rotation impacts the three-dimensional (3D) hydrodynamics of core-collapse supernovae. For our systematic study, we employ a light-bulb scheme to trigger explosions and a three-flavor neutrino leakage scheme to treat deleptonization effects and neutrino losses from the proto-neutron-star interior. Using a 15 M ⊙ progenitor, we compute 30 models in 3D with a wide variety of initial angular momentum and light-bulb neutrino luminosity. We find that the rotation can help the onset of neutrino-driven explosions for the models in which the initial angular momentum is matched to that obtained in recent stellar evolutionary calculations (~0.3-3 rad s-1 at the center). For the models with larger initial angular momentum, the shock surface deforms to be more oblate due to larger centrifugal force. This not only makes the gain region more concentrated around the equatorial plane, but also makes the mass larger in the gain region. As a result, buoyant bubbles tend to be coherently formed and rise in the equatorial region, which pushes the revived shock toward ever larger radii until a global explosion is triggered. We find that these are the main reasons that the preferred direction of the explosion in 3D rotating models is often perpendicular to the spin axis, which is in sharp contrast to the polar explosions around the axis that were obtained in previous two-dimensional simulations.

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

    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.

  14. Six-dimensional supersymmetric gauge theories, quantum cohomology of instanton moduli spaces and gl( N) Quantum Intermediate Long Wave Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Bonelli, Giulio; Sciarappa, Antonio; Tanzini, Alessandro; Vasko, Petr

    2014-07-01

    We show that the exact partition function of U( N) six-dimensional gauge theory with eight supercharges on ℂ2 × S 2 provides the quantization of the integrable system of hydrodynamic type known as gl( N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S 2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl( N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl( N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W N algebrae, thus providing a gauge theoretical proof of AGT correspondence.

  15. Gaseous Laser Targets and Optical Dignostics for Studying Compressible Turbulent Hydrodynamic Instabilities

    SciTech Connect

    Edwards, M J; Hansen, J; Miles, A R; Froula, D; Gregori, G; Glenzer, S; Edens, A; Dittmire, T

    2005-02-08

    The possibility of studying compressible turbulent flows using gas targets driven by high power lasers and diagnosed with optical techniques is investigated. The potential advantage over typical laser experiments that use solid targets and x-ray diagnostics is more detailed information over a larger range of spatial scales. An experimental system is described to study shock - jet interactions at high Mach number. This consists of a mini-chamber full of nitrogen at a pressure {approx} 1 atms. The mini-chamber is situated inside a much larger vacuum chamber. An intense laser pulse ({approx}100J in {approx} 5ns) is focused on to a thin {approx} 0.3{micro}m thick silicon nitride window at one end of the mini-chamber. The window acts both as a vacuum barrier, and laser entrance hole. The ''explosion'' caused by the deposition of the laser energy just inside the window drives a strong blast wave out into the nitrogen atmosphere. The spherical shock expands and interacts with a jet of xenon introduced though the top of the mini-chamber. The Mach number of the interaction is controlled by the separation of the jet from the explosion. The resulting flow is visualized using an optical schlieren system using a pulsed laser source at a wavelength of 0.53 {micro}m. The technical path leading up to the design of this experiment is presented, and future prospects briefly considered. Lack of laser time in the final year of the project severely limited experimental results obtained using the new apparatus.

  16. Spatial three-dimensional secondary instability compressible boundary-layer flows

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.

    1989-01-01

    Three-dimensional linear secondary instability theory is extended for compressible and high Mach number boundary layer flows. The small but finite amplitude compressible Tollmien-Schlichting wave effect on the growth of 3-D perturbations is investigated. The focus is on principal parametric resonance responsible for the strong growth of subharmonic in low disturbance environment. The effect of increasing Mach number on the onset, growth, the shape of eigenfunctions of the subharmonic is assessed, and the resulting vortical structure is examined.

  17. MULTI2D - a computer code for two-dimensional radiation hydrodynamics

    NASA Astrophysics Data System (ADS)

    Ramis, R.; Meyer-ter-Vehn, J.; Ramírez, J.

    2009-06-01

    required. Nature of problem: In inertial confinement fusion and related experiments with lasers and particle beams, energy transport by thermal radiation becomes important. Under these conditions, the radiation field strongly interacts with the hydrodynamic motion through emission and absorption processes. Solution method: The equations of radiation transfer coupled with Lagrangian hydrodynamics, heat diffusion and beam tracing (laser or ions) are solved, in two-dimensional axial-symmetric geometry ( R-Z coordinates) using a fractional step scheme. Radiation transfer is solved with angular resolution. Matter properties are either interpolated from tables (equations-of-state and opacities) or computed by user routines (conductivities and beam attenuation). Restrictions: The code has been designed for typical conditions prevailing in inertial confinement fusion (ns time scale, matter states close to local thermodynamical equilibrium, negligible radiation pressure, …). Although a wider range of situations can be treated, extrapolations to regions beyond this design range need special care. Unusual features: A special computer language, called r94, is used at top levels of the code. These parts have to be converted to standard C by a translation program (supplied as part of the package). Due to the complexity of code (hydro-code, grid generation, user interface, graphic post-processor, translator program, installation scripts) extensive manuals are supplied as part of the package. Running time: 567 seconds for the example supplied.

  18. Two-dimensional subsonic compressible flow past elliptic cylinders

    NASA Technical Reports Server (NTRS)

    Kaplan, Carl

    1938-01-01

    The method of Poggi is used to calculate, for perfect fluids, the effect of compressibility upon the flow on the surface of an elliptic cylinder at zero angle of attack and with no circulation. The result is expressed in a closed form and represents a rigorous determination of the velocity of the fluid at the surface of the obstacle insofar as the second approximation is concerned. Comparison is made with Hooker's treatment of the same problem according to the method of Janzen and Rayleight and it is found that, for thick elliptic cylinders, the two methods agree very well. The labor of computation is considerably reduced by the present solution.

  19. Volumetric imaging of shark tail hydrodynamics reveals a three-dimensional dual-ring vortex wake structure

    PubMed Central

    Flammang, Brooke E.; Lauder, George V.; Troolin, Daniel R.; Strand, Tyson

    2011-01-01

    Understanding how moving organisms generate locomotor forces is fundamental to the analysis of aerodynamic and hydrodynamic flow patterns that are generated during body and appendage oscillation. In the past, this has been accomplished using two-dimensional planar techniques that require reconstruction of three-dimensional flow patterns. We have applied a new, fully three-dimensional, volumetric imaging technique that allows instantaneous capture of wake flow patterns, to a classic problem in functional vertebrate biology: the function of the asymmetrical (heterocercal) tail of swimming sharks to capture the vorticity field within the volume swept by the tail. These data were used to test a previous three-dimensional reconstruction of the shark vortex wake estimated from two-dimensional flow analyses, and show that the volumetric approach reveals a different vortex wake not previously reconstructed from two-dimensional slices. The hydrodynamic wake consists of one set of dual-linked vortex rings produced per half tail beat. In addition, we use a simple passive shark-tail model under robotic control to show that the three-dimensional wake flows of the robotic tail differ from the active tail motion of a live shark, suggesting that active control of kinematics and tail stiffness plays a substantial role in the production of wake vortical patterns. PMID:21543357

  20. Three dimensional hydrodynamic calculations with adaptive mesh refinement of the evolution of Rayleigh Taylor and Richtmyer Meshkov instabilities in converging geometry: Multi-mode perturbations

    SciTech Connect

    Klein, R.I. |; Bell, J.; Pember, R.; Kelleher, T.

    1993-04-01

    The authors present results for high resolution hydrodynamic calculations of the growth and development of instabilities in shock driven imploding spherical geometries in both 2D and 3D. They solve the Eulerian equations of hydrodynamics with a high order Godunov approach using local adaptive mesh refinement to study the temporal and spatial development of the turbulent mixing layer resulting from both Richtmyer Meshkov and Rayleigh Taylor instabilities. The use of a high resolution Eulerian discretization with adaptive mesh refinement permits them to study the detailed three-dimensional growth of multi-mode perturbations far into the non-linear regime for converging geometries. They discuss convergence properties of the simulations by calculating global properties of the flow. They discuss the time evolution of the turbulent mixing layer and compare its development to a simple theory for a turbulent mix model in spherical geometry based on Plesset`s equation. Their 3D calculations show that the constant found in the planar incompressible experiments of Read and Young`s may not be universal for converging compressible flow. They show the 3D time trace of transitional onset to a mixing state using the temporal evolution of volume rendered imaging. Their preliminary results suggest that the turbulent mixing layer loses memory of its initial perturbations for classical Richtmyer Meshkov and Rayleigh Taylor instabilities in spherically imploding shells. They discuss the time evolution of mixed volume fraction and the role of vorticity in converging 3D flows in enhancing the growth of a turbulent mixing layer.

  1. Galactic scale gas flows in colliding galaxies: 3-dimensional, N-body/hydrodynamics experiments

    NASA Technical Reports Server (NTRS)

    Lamb, Susan A.; Gerber, Richard A.; Balsara, Dinshaw S.

    1994-01-01

    We present some results from three dimensional computer simulations of collisions between models of equal mass galaxies, one of which is a rotating, disk galaxy containing both gas and stars and the other is an elliptical containing stars only. We use fully self consistent models in which the halo mass is 2.5 times that of the disk. In the experiments we have varied the impact parameter between zero (head on) and 0.9R (where R is the radius of the disk), for impacts perpendicular to the disk plane. The calculations were performed on a Cray 2 computer using a combined N-body/smooth particle hydrodynamics (SPH) program. The results show the development of complicated flows and shock structures in the direction perpendicular to the plane of the disk and the propagation outwards of a density wave in both the stars and the gas. The collisional nature of the gas results in a sharper ring than obtained for the star particles, and the development of high volume densities and shocks.

  2. Three-dimensional hydrodynamic simulations of the combustion of a neutron star into a quark star

    SciTech Connect

    Herzog, Matthias; Roepke, Friedrich K.

    2011-10-15

    We present three-dimensional numerical simulations of turbulent combustion converting a neutron star into a quark star. Hadronic matter, described by a microphysical finite-temperature equation of state, is converted into strange quark matter. We assume this phase, represented by a bag-model equation of state, to be absolutely stable. Following the example of thermonuclear burning in white dwarfs leading to type Ia supernovae, we treat the conversion process as a potentially turbulent deflagration. Solving the nonrelativistic Euler equations using established numerical methods we conduct large eddy simulations including an elaborate subgrid scale model, while the propagation of the conversion front is modeled with a level-set method. Our results show that for large parts of the parameter space the conversion becomes turbulent and therefore significantly faster than in the laminar case. Despite assuming absolutely stable strange quark matter, in our hydrodynamic approximation an outer layer remains in the hadronic phase, because the conversion front stops when it reaches conditions under which the combustion is no longer exothermic.

  3. Verification of coronal loop diagnostics using realistic three-dimensional hydrodynamic models

    SciTech Connect

    Winebarger, Amy R.; Lionello, Roberto; Linker, Jon A.; Mikić, Zoran; Mok, Yung E-mail: lionel@predsci.com E-mail: mikicz@predsci.com

    2014-11-10

    Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure distributions. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a three-dimensional hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the background. We then determine the density, temperature, and emission measure distribution as a function of time from the observations and compare these with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to a limitation of the analysis methods, but also to inadequate background subtraction.

  4. Anisotropic characteristics of the kraichnan direct cascade in two-dimensional hydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Kuznetsov, E. A.; Sereshchenko, E. V.

    2015-12-01

    The statistical characteristics of the Kraichnan direct cascade for two-dimensional hydrodynamic turbulence are numerically studied (with spatial resolution 8192 × 8192) in the presence of pumping and viscous-like damping. It is shown that quasi-shocks of vorticity and their Fourier partnerships in the form of jets introduce an essential influence in turbulence leading to strong angular dependencies for correlation functions. The energy distribution as a function of modulus k for each angle in the inertial interval has the Kraichnan behavior, ~ k -4, and simultaneously a strong dependence on angles. However, angle average provides with a high accuracy the Kraichnan turbulence spectrum E k = C Kη2/3k-3, where η is the enstrophy flux and the Kraichnan constant C K ≃ 1.3, in correspondence with the previous simulations. Familiar situation takes place for third-order velocity structure function S 3 L which, as for the isotropic turbulence, gives the same scaling with respect to the separation length R and η, S 3 L = C 3η R 3, but the average over the angles and time differs from its isotropic value.

  5. Field evaluation of a two-dimensional hydrodynamic model near boulders for habitat calculation

    USGS Publications Warehouse

    Waddle, Terry

    2009-01-01

    Two-dimensional hydrodynamic models are now widely used in aquatic habitat studies. To test the sensitivity of calculated habitat outcomes to limitations of such a model and of typical field data, bathmetry, depth and velocity data were collected for three discharges in the vicinity of two large boulders in the South Platte River (Colorado) and used in the River2D model. Simulated depth and velocity were compared with observed values at 204 locations and the differences in habitat numbers produced by observed and simulated conditions were calculated. The bulk of the differences between simulated and observed depth and velocity values were found to lie within the likely error of measurement. However, the effect of flow simulation outliers on potential habitat outcomes must be considered when using 2D models for habitat simulation. Furthermore, the shape of the habitat suitability relation can influence the effects of simulation errors. Habitat relations with steep slopes in the velocity ranges found in similar study areas are expected to be sensitive to the magnitude of error found here. Comparison of habitat values derived from simulated and observed depth and velocity revealed a small tendency to under-predict habitat values.

  6. Two new three-dimensional contact algorithms for staggered Lagrangian Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Jia, Zupeng; Gong, Xiangfei; Zhang, Shudao; Liu, Jun

    2014-06-01

    This paper presents two new three-dimensional contact algorithms for staggered Lagrangian Hydrodynamics, named discrete accurate matching method and discrete Lagrangian multiplier method. These new contact algorithms utilize the unified contact algorithm for contact searching. Contact segments from all potential contact surfaces are treated as a single set. The basic idea of these new methods is to partition all contact segments into triangular facets firstly; then for each pair of two triangular facets which correspond to a hitting node and a target node respectively, these two triangular facets are projected to one plane and their intersection area is calculated; the nodal masses and nodal forces of the hitting node and the target node are distributed to the intersection portions of these two triangular facets respectively according to the proportion of the intersection area to corresponding nodal area. In the discrete accurate matching method, the masses and forces of the intersection portions of these two triangular facets are added to corresponding contact nodes of each other, and then the accelerations and velocities of the contact nodes are updated; while in the discrete Lagrangian multiplier method, the intersection portions of these two triangular facets are considered as a 1D contact pair in the normal direction for which the contact force is explicitly calculated by the Lagrangian multiplier method for a 1D contact pair of one hitting point and one target point, then the contact force being added to corresponding contact nodes. These new contact algorithms are assessed through several numerical tests performed on three-dimensional structured and unstructured meshes. The results of these tests show the accuracy and robustness of these new methods.

  7. Impacts of rotation on three-dimensional hydrodynamics of core-collapse supernovae

    SciTech Connect

    Nakamura, Ko; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

    2014-09-20

    We perform a series of simplified numerical experiments to explore how rotation impacts the three-dimensional (3D) hydrodynamics of core-collapse supernovae. For our systematic study, we employ a light-bulb scheme to trigger explosions and a three-flavor neutrino leakage scheme to treat deleptonization effects and neutrino losses from the proto-neutron-star interior. Using a 15 M {sub ☉} progenitor, we compute 30 models in 3D with a wide variety of initial angular momentum and light-bulb neutrino luminosity. We find that the rotation can help the onset of neutrino-driven explosions for the models in which the initial angular momentum is matched to that obtained in recent stellar evolutionary calculations (∼0.3-3 rad s{sup –1} at the center). For the models with larger initial angular momentum, the shock surface deforms to be more oblate due to larger centrifugal force. This not only makes the gain region more concentrated around the equatorial plane, but also makes the mass larger in the gain region. As a result, buoyant bubbles tend to be coherently formed and rise in the equatorial region, which pushes the revived shock toward ever larger radii until a global explosion is triggered. We find that these are the main reasons that the preferred direction of the explosion in 3D rotating models is often perpendicular to the spin axis, which is in sharp contrast to the polar explosions around the axis that were obtained in previous two-dimensional simulations.

  8. Quasi-three-dimensional analysis for composite cylinder under lateral compressive loading

    SciTech Connect

    Nishiwaki, Tsuyoshi |; Yokoyama, Atsushi; Maekawa, Zenichiro; Hamada, Hiroyuki; Mori, Sadaki

    1995-11-01

    This paper presents a lateral compressive analytical method for CFRP cylinders using a quasi-three-dimensional model. This numerical model was constructed by shell and beam elements which represent fiber and resin respectively. The lateral compressive behaviors of CFRP cylinders with [{theta}/{minus}{theta}]sym ({theta} = 15{degree}, 30{degree}, 45{degree}, 60{degree}) were experimentally evaluated. The damage propagation was simulated using the quasi-three-dimensional model. The transverse cracking and interlaminar delamination were simulated independently. Furthermore comparing the analytical and experimental results, it is confirmed that the proposed analytical method is precise.

  9. The topology and vorticity dynamics of a three-dimensional plane compressible wake

    NASA Technical Reports Server (NTRS)

    Chen, Jacqueline H.; Cantwell, Brian J.; Mansour, Nagi N.

    1989-01-01

    The three-dimensional aspects of transition in a low Mach number plane compressible wake are studied numerically. Comparisons are made between the topology of the velocity field and the vorticity dynamics of the flow based on results from direct numerical simulations of the full compressible Navier-Stokes equations. The velocity field is integrated to obtain instantaneous streamlines at different stages in the evolution. A generalized three-dimensional critical point theory is applied to classify the critical points of the velocity field.

  10. Linear stability analysis of three-dimensional compressible boundary layers

    NASA Technical Reports Server (NTRS)

    Malik, Mujeeb R.; Orszag, Steven A.

    1987-01-01

    A compressible stability analysis computer code is developed. The code uses a matrix finite-difference method for local eigenvale solution when a good guess for the eigenvalue is available and is significantly more computationally efficient than the commonly used inital-value approach. The local eigenvalue search procedure also results in eigenfunctions and, at little extra work, group velocities. A globally convergent eigenvalue procedure is also developed that may be used when no guess for the eigenvalue is available. The global problem is formulated in such a way that no unstable spurious modes appear so that the method is suitable for use in a black-box stability code. Sample stability calculations are presented for the boundary layer profiles of an LFC swept wing.

  11. Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries

    PubMed Central

    Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M.

    2015-01-01

    Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g−1 and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices. PMID:26021485

  12. Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries.

    PubMed

    Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M

    2015-01-01

    Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g(-1) and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices. PMID:26021485

  13. Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries

    NASA Astrophysics Data System (ADS)

    Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M.

    2015-05-01

    Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g-1 and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices.

  14. Analytic solutions for the three-dimensional compressible Navier-Stokes equation

    NASA Astrophysics Data System (ADS)

    Barna, I. F.; Mátyás, L.

    2014-10-01

    We investigate the three-dimensional compressible Navier-Stokes (NS) and the continuity equations in Cartesian coordinates for Newtonian fluids. The problem has an importance in different fields of science and engineering like fluid, aerospace dynamics or transfer processes. Finding an analytic solution may bring considerable progress in understanding the transport phenomena and in the design of different equipments where the NS equation is applicable. For solving the equation the polytropic equation of state is used as a closing condition. The key idea is the three-dimensional generalization of the well-known self-similar ansatz which was already used for non-compressible viscous flow in our former study. The geometrical interpretations of the trial function is also discussed. We compared our recent results to the former non-compressible ones.

  15. Secondary instability of compressible boundary layer to subharmonic three-dimensional disturbances

    NASA Technical Reports Server (NTRS)

    El Hady, Nabil M.

    1989-01-01

    Three-dimensional linear secondary instability theory is extended for compressible boundary layers on a flat plate in the presence of finite amplitude Tollmien-Schlichting (T-S) waves. The focus is on principal parametric resonance responsible for the strong growth of harmonics in a low disturbance environment.

  16. Secondary instability of compressible boundary layer to subharmonic three-dimensional disturbances

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.

    1988-01-01

    Three-dimensional linear secondary instability theory is extended for compressible boundary layers on a flat plate in the presence of finite amplitude Tollmien-Schlichting (T-S) waves. The focus is on principal parametric resonance responsible for the strong growth of harmonics in a low disturbance environment.

  17. Quasi One-Dimensional Unsteady Modeling of External Compression Supersonic Inlets

    NASA Technical Reports Server (NTRS)

    Kopasakis, George; Connolly, Joseph W.; Kratz, Jonathan

    2012-01-01

    The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of an axisymmetric external compression supersonic inlet is being developed. The model utilizes compressible flow computational fluid dynamics to model the internal inlet segment as well as the external inlet portion between the cowl lip and normal shock, and compressible flow relations with flow propagation delay to model the oblique shocks upstream of the normal shock. The external compression portion between the cowl-lip and the normal shock is also modeled with leaking fluxes crossing the sonic boundary, with a moving CFD domain at the normal shock boundary. This model has been verified in steady state against tunnel inlet test data and it s a first attempt towards developing a more comprehensive model for inlet dynamics.

  18. Verification of the two-dimensional hydrodynamic model based on remote sensing

    NASA Astrophysics Data System (ADS)

    Sazonov, Alexey; Mikhailukova, Polina; Krylenko, Inna; Frolova, Natalya; Kireeva, Mariya

    2016-04-01

    Mathematical modeling methods are used more and more actively to evaluate possible damage, identify potential flood zone and the influence of individual factors affecting the river during the passage of the flood. Calculations were performed by means of domestic software complex «STREAM-2D» which is based on the numerical solution of two-dimensional St. Venant equations. One of the major challenges in mathematical modeling is the verification of the model. This is usually made using data on water levels from hydrological stations: the smaller the difference of the actual level and the simulated one, the better the quality of the model used. Data from hydrological stations are not always available, so alternative sources of verification, such as remote sensing, are increasingly used. The aim of this work is to develop a method of verification of hydrodynamic model based on a comparison of actual flood zone area, which in turn is determined on the basis of the automated satellite image interpretation methods for different imaging systems and flooded area obtained in the course of the model. The study areas are Lena River, The North Dvina River, Amur River near Blagoveshchensk. We used satellite images made by optical and radar sensors: SPOT-5/HRG, Resurs-F, Radarsat-2. Flooded area were calculated using unsupervised classification (ISODATA and K-mean) for optical images and segmentation for Radarsat-2. Knowing the flow rate and the water level at a given date for the upper and lower limits of the model, respectively, it is possible to calculate flooded area by means of program STREAM-2D and GIS technology. All the existing vector layers with the boundaries of flooding are included in a GIS project for flood area calculation. This study was supported by the Russian Science Foundation, project no. 14-17-00155.

  19. Three-dimensional hydrodynamic and water quality model for TMDL development of Lake Fuxian, China.

    PubMed

    Zhao, Lei; Zhang, Xiaoling; Liu, Yong; He, Bin; Zhu, Xiang; Zou, Rui; Zhu, Yuanguan

    2012-01-01

    Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making. PMID:23513675

  20. SPIRALING OUT OF CONTROL: THREE-DIMENSIONAL HYDRODYNAMICAL MODELING OF THE COLLIDING WINDS IN {eta} CARINAE

    SciTech Connect

    Parkin, E. R.; Pittard, J. M.; Corcoran, M. F.; Hamaguchi, K.

    2011-01-10

    Three-dimensional adaptive mesh refinement hydrodynamical simulations of the wind-wind collision between the enigmatic supermassive star {eta} Car and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically thin radiative cooling, and orbital motion. Simulations with static stars with a periastron passage separation reveal that the preshock companion star's wind speed is sufficiently reduced so that radiative cooling in the postshock gas becomes important, permitting the runaway growth of nonlinear thin-shell instabilities (NTSIs) which massively distort the wind-wind collision region (WCR). However, large-scale simulations, which include the orbital motion of the stars, show that orbital motion reduces the impact of radiative inhibition and thus increases the acquired preshock velocities. As such, the postshock gas temperature and cooling time see a commensurate increase, and sufficient gas pressure is preserved to stabilize the WCR against catastrophic instability growth. We then compute synthetic X-ray spectra and light curves and find that, compared to previous models, the X-ray spectra agree much better with XMM-Newton observations just prior to periastron. The narrow width of the 2009 X-ray minimum can also be reproduced. However, the models fail to reproduce the extended X-ray minimum from previous cycles. We conclude that the key to explaining the extended X-ray minimum is the rate of cooling of the companion star's postshock wind. If cooling is rapid then powerful NTSIs will heavily disrupt the WCR. Radiative inhibition of the companion star's preshock wind, albeit with a stronger radiation-wind coupling than explored in this work, could be an effective trigger.

  1. One-dimensional radiation-hydrodynamic scaling studies of imploding spherical plasma liners

    SciTech Connect

    Awe, T. J.; Adams, C. S.; Davis, J. S.; Hanna, D. S.; Hsu, S. C.; Cassibry, J. T.

    2011-07-15

    One-dimensional radiation-hydrodynamic simulations are performed to develop insight into the scaling of stagnation pressure with initial conditions of an imploding spherical plasma shell or ''liner.'' Simulations reveal the evolution of high-Mach-number (M), annular, spherical plasma flows during convergence, stagnation, shock formation, and disassembly, and indicate that cm- and {mu}s-scale plasmas with peak pressures near 1 Mbar can be generated by liners with initial kinetic energy of several hundred kilo-joules. It is shown that radiation transport and thermal conduction must be included to avoid non-physical plasma temperatures at the origin which artificially limit liner convergence and, thus, the peak stagnation pressure. Scalings of the stagnated plasma lifetime ({tau}{sub stag}) and average stagnation pressure (P{sub stag}, the pressure at the origin, averaged over {tau}{sub stag}) are determined by evaluating a wide range of liner initial conditions. For high-M flows, {tau}{sub stag} {approx} {Delta}R/v{sub 0}, where {Delta}R and v{sub 0} are the initial liner thickness and velocity, respectively. Furthermore, for argon liners, P{sub stag} scales approximately as v{sub 0}{sup 15/4} over a wide range of initial densities (n{sub 0}) and as n{sub 0}{sup 1/2} over a wide range of v{sub 0}. The approximate scaling P{sub stag} {approx} M{sup 3/2} is also found for a wide range of liner-plasma initial conditions.

  2. Acoustic waves in a stratified atmosphere. IV. Three-dimensional nonlinear hydrodynamics

    NASA Astrophysics Data System (ADS)

    Kalkofen, W.; Rossi, P.; Bodo, G.; Massaglia, S.

    2010-09-01

    Context. The quiet solar chromosphere in the interior of supergranulation cells is believed to be heated by the dissipation of acoustic waves that originate with a typical period of 3 min in the photosphere. Aims: We investigate how the horizontal expansion with height of acoustic waves traveling upward into an isothermal, gravitationally stratified atmosphere depends on the size of the source region. Methods: We have solved the three-dimensional, nonlinear, time-dependent hydrodynamic equations for impulsively-generated, upward-propagating acoustic waves, assuming cylindrical symmetry. Results: When the diameter of the source of acoustic waves is small, the pattern of the upward-propagating waves is that of a point source, for which the energy travels upward in a vertical cone, qualitatively matching the observed pattern of bright-point expansion with height. For the largest plausible size of a source region, i.e., with granular size of 1 Mm, wave propagation in the low chromosphere is approximately that of plane waves, but in the middle and upper chromosphere it is also that of a point source. The assumption of plane-wave propagation is not a good approximation in the solar chromosphere. The upward-directed energy flux is larger than that of the solar chromosphere, at least in the middle and upper chromosphere, and probably throughout. Conclusions: Simulations of impulsively generated acoustic waves emitted from source regions with diameters that are small compared to the pressure scale height of the atmosphere qualitatively reproduce the upward expansion observed in chromospheric bright points. The emission features in the cores of the H and K lines are predicted to be blueshifted for a pulse and redshifted for the waves in its wake. The contribution of internal gravity waves to the upward energy flux is small and decreases with increasing size of the source region.

  3. A global three-dimensional radiation magneto-hydrodynamic simulation of super-eddington accretion disks

    SciTech Connect

    Jiang, Yan-Fei; Stone, James M.; Davis, Shane W.

    2014-12-01

    We study super-Eddington accretion flows onto black holes using a global three-dimensional radiation magneto-hydrodynamical simulation. We solve the time-dependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magneto-rotational instability provides self-consistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ∼220 L {sub Edd}/c {sup 2} and forms a radiation-driven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ∼20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ∼10 L {sub Edd}. This yields a radiative efficiency ∼4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous X-ray sources.

  4. Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

    SciTech Connect

    Smalyuk, V. A.; Weber, S. V.; Casey, D. T.; Clark, D. S.; Field, J. E.; Haan, S. W.; Hamza, A. V.; Hoover, D. E.; Landen, O. L.; Nikroo, A.; Robey, H. F.; Weber, C. R.

    2015-06-08

    The first hydrodynamic instability growth measurements with three-dimensional (3D) surface-roughness modulations were performed on CH shell spherical implosions at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng.43, 2841 (2004)]. The initial capsule outer-surface amplitudes were increased approximately four times, compared with the standard specifications, to increase the signal-to-noise ratio, helping to qualify a technique for measuring small 3D modulations. The instability growth measurements were performed using x-ray through-foil radiography based on time-resolved pinhole imaging. Averaging over 15 similar images significantly increased the signal-to-noise ratio, making possible a comparison with 3D simulations. At a convergence ratio of${\\sim}2.4$, the measured modulation levels were${\\sim}3$times larger than those simulated based on the growth of the known imposed initial surface modulations. Several hypotheses are discussed, including increased instability growth due to modulations of the oxygen content in the bulk of the capsule. Future experiments will be focused on measurements with standard 3D ‘native-roughness’ capsules as well as with deliberately imposed oxygen modulations.

  5. Three-dimensional Hydrodynamic Simulations of Accretion in High-mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Raymer, Eric John

    Wind accretion in high-mass X-ray binaries (HMXBs) often results in highly variable X-ray behavior, the nature of which is not well understood. Most models of wind accretion are based on the analytical predictions of Hoyle-Lyttleton accretion (HLA), which assumes a steady axisymmetric flow. Surprisingly little is known about the structure, stability, and time-evolution of HLA in three dimensions, particularly in the presence of non-uniform winds. This work describes hydrodynamic simulations of idealized HLA in three-dimensions, then applies these simulations to two HMXB subclasses that exhibit unexplained X-ray behavior. Our idealized HLA models show that the accretion flow remains steady and stable in two-dimensional axisymmetric and three dimensional grid geometries, assuming a uniform upstream flow. We test the stability of the model with linear upstream density gradients and find that they are able to induce rotational flow around the accretor that reduces the mass accretion rate by up to an order of magnitude. We apply our 3D model to accretion in the context of Be/X-ray binaries, in which the accreting neutron star is immersed in the dense decretion disk of the Be donor star. These systems have traditionally been described with 2D models that exhibit the flip-flop instability. This instability results in the formation and destruction of transient accretion disks with accompanying bursts of mass accretion. Our 3D models show no sign of the flip-flop instability, but instead display rotation about the neutron star directed primarily out of the plane of the decretion disk. This rotation generates large-scale asymmetries in the bow shock and suppresses mass accretion by up to two orders of magnitude. The accretion of a clumped stellar wind is one of the primary mechanisms proposed to explain the high-luminosity X-ray flares of supergiant fast X-ray transients. We model clump accretion in 3D to determine whether the impact of a clump can produce flares with a

  6. Calculation of three-dimensional compressible laminar and turbulent boundary flows. Three-dimensional compressible boundary layers of reacting gases over realistic configurations

    NASA Technical Reports Server (NTRS)

    Kendall, R. M.; Bonnett, W. S.; Nardo, C. T.; Abbett, M. J.

    1975-01-01

    A three-dimensional boundary-layer code was developed for particular application to realistic hypersonic aircraft. It is very general and can be applied to a wide variety of boundary-layer flows. Laminar, transitional, and fully turbulent flows of compressible, reacting gases are efficiently calculated by use of the code. A body-oriented orthogonal coordinate system is used for the calculation and the user has complete freedom in specifying the coordinate system within the restrictions that one coordinate must be normal to the surface and the three coordinates must be mutually orthogonal.

  7. Frequency Spectrum of Exact Solutions of the Two-Dimensional Hydrodynamic Equations

    NASA Astrophysics Data System (ADS)

    Abrashkin, A. A.; Yakubovich, E. I.

    2016-05-01

    We show that the discrete frequency spectrum of a plane hydrodynamic flow of ideal incompressible liquid with localized trajectories of the liquid particles can contain only one, two, or an infinite number of harmonics.

  8. THEHYCO-3DT: Thermal hydrodynamic code for the 3 dimensional transient calculation of advanced LMFBR core

    SciTech Connect

    Vitruk, S.G.; Korsun, A.S.; Ushakov, P.A.

    1995-09-01

    The multilevel mathematical model of neutron thermal hydrodynamic processes in a passive safety core without assemblies duct walls and appropriate computer code SKETCH, consisted of thermal hydrodynamic module THEHYCO-3DT and neutron one, are described. A new effective discretization technique for energy, momentum and mass conservation equations is applied in hexagonal - z geometry. The model adequacy and applicability are presented. The results of the calculations show that the model and the computer code could be used in conceptual design of advanced reactors.

  9. Three-Dimensional Parallel Lattice Boltzmann Hydrodynamic Simulations of Turbulent Flows in Interstellar Dark Clouds

    NASA Astrophysics Data System (ADS)

    Muders, Dirk

    1995-08-01

    Exploring the clumpy and filamentary structure of interstellar molecular clouds is one of the key problems of modern astrophysics. So far, we have little knowledge of the physical processes that cause the structure, but turbulence is suspected to be essential. In this thesis I study turbulent flows and how they contribute to the structure of interstellar dark clouds. To this end, three-dimensional numerical hydrodynamic simulations are needed since the detailed turbulent spatial and velocity structure cannot be analytically calculated. I employ the ``Lattice Boltzmann Method'', a recently developed numerical method which solves the Boltzmann equation in a discretized phase space. Mesoscopic particle packets move with fixed velocities on a Cartesian lattice and at each time step they exchange mass according to given rules. Because of its mainly local operations the method is well suited for application on parallel or clustered computers. As part of my thesis I have developed a parallelized ``Lattice Boltzmann Method'' hydrodynamics code. I have improved the numerical stability for Reynolds numbers of up to 104.5 and Mach numbers of up to 0.9 and I have extended the method to include a second miscible fluid phase. The code has been used on the three currently most powerful workstations at the ``Max-Planck-Institut für Radioastronomie'' in Bonn and on the massively parallel mainframe CM-5 at the ``Gesellschaft für Mathematik und Datenverarbeitung'' in St. Augustin. The simulations consist of collimated shear flows and the motion of molecular clumps through an ambient medium. The dependence of the emerging structure on Reynolds and Mach numbers is studied. The main results are (1) that distinct clumps and filaments appear only at the transition between laminar and fully turbulent flow at Reynolds numbers between 500 and 5000 and (2) that subsonic viscous shear flows are capable of producing the dark cloud velocity structure. The unexpectedly low Reynolds numbers can

  10. BEM-based numerical study of three-dimensional compressible bubble dynamics in stokes flow

    NASA Astrophysics Data System (ADS)

    Abramova, O. A.; Akhatov, I. Sh.; Gumerov, N. A.; Itkulova, Yu. A.

    2014-09-01

    The dynamics of compressible gas bubbles in a viscous shear flow and an acoustic field at low Reynolds numbers is studied. The numerical approach is based on the boundary element method (BEM), which is effective as applied to the three-dimensional simulation of bubble deformation. However, the application of the conventional BEM to compressible bubble dynamics faces difficulties caused by the degeneration of the resulting algebraic system. Additional relations based on the Lorentz reciprocity principle are used to cope with this problem. Test computations of the dynamics of a single bubble and bubble clusters in acoustic fields and shear flows are presented.

  11. One-Dimensional Lagrangian Code for Plasma Hydrodynamic Analysis of a Fusion Pellet Driven by Ion Beams.

    Energy Science and Technology Software Center (ESTSC)

    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 gainmore » 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.« less

  12. Three-dimensional nonlinear ideal MHD equilibria with field-aligned incompressible and compressible flows

    NASA Astrophysics Data System (ADS)

    Moawad, S. M.; Ibrahim, D. A.

    2016-08-01

    The equilibrium properties of three-dimensional ideal magnetohydrodynamics (MHD) are investigated. Incompressible and compressible flows are considered. The governing equations are taken in a steady state such that the magnetic field is parallel to the plasma flow. Equations of stationary equilibrium for both of incompressible and compressible MHD flows are derived and described in a mathematical mode. For incompressible MHD flows, Alfvénic and non-Alfvénic flows with constant and variable magnetofluid density are investigated. For Alfvénic incompressible flows, the general three-dimensional solutions are determined with the aid of two potential functions of the velocity field. For non-Alfvénic incompressible flows, the stationary equilibrium equations are reduced to two differential constraints on the potential functions, flow velocity, magnetofluid density, and the static pressure. Some examples which may be of some relevance to axisymmetric confinement systems are presented. For compressible MHD flows, equations of the stationary equilibrium are derived with the aid of a single potential function of the velocity field. The existence of three-dimensional solutions for these MHD flows is investigated. Several classes of three-dimensional exact solutions for several cases of nonlinear equilibrium equations are presented.

  13. Three-dimensional supersonic flow around double compression ramp with finite span

    NASA Astrophysics Data System (ADS)

    Lee, H. S.; Lee, J. H.; Park, G.; Park, S. H.; Byun, Y. H.

    2016-03-01

    Three-dimensional flows of Mach number 3 around a double-compression ramp with finite span have been investigated numerically. Shadowgraph visualisation images obtained in a supersonic wind tunnel are used for comparison. A three-dimensional Reynolds-averaged Navier-Stokes solver was used to obtain steady numerical solutions. Two-dimensional numerical results are also compared. Four different cases were studied: two different second ramp angles of 30° and 45° in configurations with and without sidewalls, respectively. Results showed that there is a leakage of mass and momentum fluxes heading outwards in the spanwise direction for three-dimensional cases without sidewalls. The leakage changed the flow characteristics of the shock-induced boundary layer and resulted in the discrepancy between the experimental data and two-dimensional numerical results. It is found that suppressing the flow leakage by attaching the sidewalls enhances the two-dimensionality of the experimental data for the double-compression ramp flow.

  14. Using two-dimensional hydrodynamic models at scales of ecological importance

    NASA Astrophysics Data System (ADS)

    Crowder, D. W.; Diplas, P.

    2000-05-01

    Modeling of flow features that are important in assessing stream habitat conditions has been a long-standing interest of stream biologists. Recently, they have begun examining the usefulness of two-dimensional (2-D) hydrodynamic models in attaining this objective. Current modeling practices consider relatively long channel sections with their bathymetry represented in terms of large, macro-scale, topographic features. Meso-scale topographic features, such as boulders, root-wads and other obstructions are typically not considered in the modeling process. Instead, the overall effects of these flow obstructions are captured through increased values in the channel roughness parameters. Such an approach to 2-D modeling allows one to accurately predict average depth and velocity values; however, it is not capable of providing any information about the flow patterns in the vicinity of these obstructions. Biologists though have known that such meso-scale features and the complex velocity patterns generated by their presence, play an important role in the ecology of streams, and thus cannot be ignored. It is therefore evident that there is a need to develop better tools, capable of modeling flow characteristics at scales of ecological importance. The purpose of this study is to expand the utility of 2-D hydraulic models to capture these flow features that are critical for characterizing stream habitat conditions. There exists a paucity of research addressing what types of topographic features should be included in 2-D model studies and to what extent a boulder or series of exposed boulders can influence predicted flow conditions and traditional useable habitat computations. Moreover, little research has been performed to evaluate the impact mesh refinement has on model results in natural streams. Numerical simulations, based on a natural river channel containing several large boulders, indicate that explicitly modeling local obstructions/boulders can significantly impact

  15. Two-Dimensional Microfluidics: hydrodynamics of drops and interfaces in flowing smectic liquid crystal channels

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyuan; Nguyen, Zoom; Park, Cheol; Maclennan, Joe; Maclennan, Matt; Clark, Noel

    2012-02-01

    The quantization of film thickness in freely suspended fluid smectic liquid crystal film enables the study of the hydrodynamics of drops and interfaces in 2D. We report microfluidic experiments, in which we observe the hydrodynamics of 2D drops flowing in channels. Using high-speed video microscopy, we track the shape of 2D drops and interfaces, visualizing the deterministic lateral displacement-based separation and pinched flow separation phenomena previously observed only in 3D. Finally, we demonstrate techniques for 2D drop generation and sorting, which will be used for 2D microfluidic applications.

  16. Out-of-Core Compression and Decompression of Large n-Dimensional Scalar Fields

    SciTech Connect

    Ibarria, L; Lindstrom, P; Rossignac, J; Szymczak, A

    2003-05-07

    We present a simple method for compressing very large and regularly sampled scalar fields. Our method is particularly attractive when the entire data set does not fit in memory and when the sampling rate is high relative to the feature size of the scalar field in all dimensions. Although we report results for R{sup 3} and R{sup 4} data sets, the proposed approach may be applied to higher dimensions. The method is based on the new Lorenzo predictor, introduced here, which estimates the value of the scalar field at each sample from the values at processed neighbors. The predicted values are exact when the n-dimensional scalar field is an implicit polynomial of degree n-1. Surprisingly, when the residuals (differences between the actual and predicted values) are encoded using arithmetic coding, the proposed method often outperforms wavelet compression in an L{infinity} sense. The proposed approach may be used both for lossy and lossless compression and is well suited for out-of-core compression and decompression, because a trivial implementation, which sweeps through the data set reading it once, requires maintaining only a small buffer in core memory, whose size barely exceeds a single n-1 dimensional slice of the data.

  17. Three-Dimensional Inverse Transport Solver Based on Compressive Sensing Technique

    NASA Astrophysics Data System (ADS)

    Cheng, Yuxiong; Wu, Hongchun; Cao, Liangzhi; Zheng, Youqi

    2013-09-01

    According to the direct exposure measurements from flash radiographic image, a compressive sensing-based method for three-dimensional inverse transport problem is presented. The linear absorption coefficients and interface locations of objects are reconstructed directly at the same time. It is always very expensive to obtain enough measurements. With limited measurements, compressive sensing sparse reconstruction technique orthogonal matching pursuit is applied to obtain the sparse coefficients by solving an optimization problem. A three-dimensional inverse transport solver is developed based on a compressive sensing-based technique. There are three features in this solver: (1) AutoCAD is employed as a geometry preprocessor due to its powerful capacity in graphic. (2) The forward projection matrix rather than Gauss matrix is constructed by the visualization tool generator. (3) Fourier transform and Daubechies wavelet transform are adopted to convert an underdetermined system to a well-posed system in the algorithm. Simulations are performed and numerical results in pseudo-sine absorption problem, two-cube problem and two-cylinder problem when using compressive sensing-based solver agree well with the reference value.

  18. Three-dimensional plastic flow of anisotropic layer compressed by flat dies

    NASA Astrophysics Data System (ADS)

    Maksimova, Ljudmila A.

    2016-06-01

    Three-dimensional flow of anisotropic plastic layer compressed by parallel rough flat dies is considered. Ideal plastic material model with Hill anisotropic yield criterion modification of Mises isotropic model is used with associated plastic flow rule. General solution of a thin layer plastic flow problem with Prandtl linear velocity and shear stress variation in layer thickness direction is presented. Effects of contact friction force vector module and direction on the layer pressure on the dies and the layer plastic flow are considered.

  19. Quasi-one-dimensional compressible flow across face seals and narrow slots. 2: Computer program

    NASA Technical Reports Server (NTRS)

    Zuk, J.; Smith, P. J.

    1972-01-01

    A computer program is presented for compressible fluid flow with friction across face seals and through narrow slots. The computer program carries out a quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions for parallel surfaces. The program is written in FORTRAN IV. The input and output variables are in either the International System of Units (SI) or the U.S. customary system.

  20. Simulating hydrodynamics in a spring-fed estuary using a three-dimensional unstructured Cartesian grid model

    NASA Astrophysics Data System (ADS)

    Chen, XinJian

    2012-12-01

    This paper presents an application of a three-dimensional unstructured Cartesian grid model (Chen, 2011) to a real-world case, namely the Crystal River/Kings Bay system located on the Gulf coast of the Florida peninsula of the United States. Crystal River/Kings Bay is a spring-fed estuarine system which is believed to be the largest natural refuge in the United States for manatees during the coldest days in winter because of the existence of a large amount of discharge out of numerous spring vents at the bottom of Kings Bay. The unstructured Cartesian grid model was used to simulate hydrodynamics, including salinity transport processes and thermodynamics, in the estuary during a 34-month period from April 2007 to February 2010. Although there are some unidentified uncertainties in quantifying flow rates from the spring vents and salinity variations in spring flows, simulated water elevations, salinities, temperatures, and cross-sectional flux all match well or very well with measured real-time field data. This suggests that the unstructured Cartesian grid model can adequately simulate hydrodynamics in a complex shallow water system such as Crystal River/Kings Bay and the numerical theory for the unstructured Cartesian grid model works properly. The successful simulation of hydrodynamics in the estuarine system also suggests that an empirical formula that relates the spring discharge with the water level in Kings Bay and the groundwater level measured in a nearby well is reasonable.

  1. Experimental reconstruction of three-dimensional hydrodynamic loading in water entry problems through particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Jalalisendi, Mohammad; Shams, Adel; Panciroli, Riccardo; Porfiri, Maurizio

    2015-02-01

    Predicting the hydrodynamic loading during water impact is of fundamental importance for the design of offshore and aerospace structures. Here, we experimentally characterize the 3D hydrodynamic loading on a rigid wedge vertically impacting a quiescent water surface. Planar particle image velocimetry is used to measure the velocity field on several planes, along the width and the length of the impacting wedge. Such data are ultimately utilized to estimate the 3D velocity field in the whole fluid domain, where the pressure field is reconstructed from the solution of the incompressible Navier-Stokes equations. Experimental results confirm that the velocity field is nearly 2D at the mid-span of the wedge, while the axial velocity along the length of the wedge becomes significant in the proximity of the edges. The variation of the fluid flow along the length of the wedge regulates the hydrodynamic loading experienced during the impact. Specifically, the hydrodynamic loading is maximized at the mid-span of the wedge and considerably decreases toward the edges. The method proposed in this study can find application in several areas of experimental fluid mechanics, where the analysis of unsteady 3D fluid-structure interactions is of interest.

  2. Fish Pectoral Fin Hydrodynamics; Part III: Low Dimensional Models via POD Analysis

    NASA Astrophysics Data System (ADS)

    Bozkurttas, M.; Madden, P.

    2005-11-01

    The highly complex kinematics of the pectoral fin and the resulting hydrodynamics does not lend itself easily to analysis based on simple notions of pitching/heaving/paddling kinematics or lift/drag based propulsive mechanisms. A more inventive approach is needed to dissect the fin gait and gain insight into the hydrodynamic performance of the pectoral fin. The focus of the current work is on the hydrodynamics of the pectoral fin of a bluegill sunfish in steady forward motion. The 3D, time-dependent fin kinematics is obtained via a stereo-videographic technique. We employ proper orthogonal decomposition to extract the essential features of the fin gait and then use CFD to examine the hydrodynamics of simplified gaits synthesized from the POD modes. The POD spectrum shows that the first two, three and five POD modes capture 55%, 67%, and 80% of the motion respectively. The first three modes are in particular highly distinct: Mode-1 is a ``cupping'' motion where the fin cups forward as it is abducted; Mode-2 is an ``expansion'' motion where the fin expands to present a larger area during adduction and finally Mode-3 involves a ``spanwise flick'' of the dorsal edge of the fin. Numerical simulation of flow past fin gaits synthesized from these modes lead to insights into the mechanisms of thrust production; these are discussed in detail.

  3. Design of indirectly driven, high-compression Inertial Confinement Fusion implosions with improved hydrodynamic stability using a 4-shock adiabat-shaped drive

    SciTech Connect

    Milovich, J. L. Robey, H. F.; Clark, D. S.; Baker, K. L.; Casey, D. T.; Cerjan, C.; Field, J.; MacPhee, A. G.; Pak, A.; Patel, P. K.; Peterson, J. L.; Smalyuk, V. A.; Weber, C. R.

    2015-12-15

    Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm{sup 2}, but with significantly lower total neutron yields (between 1.5 × 10{sup 14} and 5.5 × 10{sup 14}) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the “high-foot” experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3–10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm{sup 2}. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.

  4. Design of indirectly driven, high-compression Inertial Confinement Fusion implosions with improved hydrodynamic stability using a 4-shock adiabat-shaped drive

    NASA Astrophysics Data System (ADS)

    Milovich, J. L.; Robey, H. F.; Clark, D. S.; Baker, K. L.; Casey, D. T.; Cerjan, C.; Field, J.; MacPhee, A. G.; Pak, A.; Patel, P. K.; Peterson, J. L.; Smalyuk, V. A.; Weber, C. R.

    2015-12-01

    Experimental results from indirectly driven ignition implosions during the National Ignition Campaign (NIC) [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] achieved a record compression of the central deuterium-tritium fuel layer with measured areal densities up to 1.2 g/cm2, but with significantly lower total neutron yields (between 1.5 × 1014 and 5.5 × 1014) than predicted, approximately 10% of the 2D simulated yield. An order of magnitude improvement in the neutron yield was subsequently obtained in the "high-foot" experiments [O. A. Hurricane et al., Nature 506, 343 (2014)]. However, this yield was obtained at the expense of fuel compression due to deliberately higher fuel adiabat. In this paper, the design of an adiabat-shaped implosion is presented, in which the laser pulse is tailored to achieve similar resistance to ablation-front instability growth, but with a low fuel adiabat to achieve high compression. Comparison with measured performance shows a factor of 3-10× improvement in the neutron yield (>40% of predicted simulated yield) over similar NIC implosions, while maintaining a reasonable fuel compression of >1 g/cm2. Extension of these designs to higher laser power and energy is discussed to further explore the trade-off between increased implosion velocity and the deleterious effects of hydrodynamic instabilities.

  5. Utilizing dimensional analysis with observed data to determine the significance of hydrodynamic solutions in coastal hydrology

    USGS Publications Warehouse

    Swain, Eric D.; Decker, Jeremy D.; Hughes, Joseph D.

    2014-01-01

    In this paper, the authors present an analysis of the magnitude of the temporal and spatial acceleration (inertial) terms in the surface-water flow equations and determine the conditions under which these inertial terms have sufficient magnitude to be required in the computations. Data from two South Florida field sites are examined and the relative magnitudes of temporal acceleration, spatial acceleration, and the gravity and friction terms are compared. Parameters are derived by using dimensionless numbers and applied to quantify the significance of the hydrodynamic effects. The time series of the ratio of the inertial and gravity terms from field sites are presented and compared with both a simplified indicator parameter and a more complex parameter called the Hydrodynamic Significance Number (HSN). Two test-case models were developed by using the SWIFT2D hydrodynamic simulator to examine flow behavior with and without the inertial terms and compute the HSN. The first model represented one of the previously-mentioned field sites during gate operations of a structure-managed coastal canal. The second model was a synthetic test case illustrating the drainage of water down a sloped surface from an initial stage while under constant flow. The analyses indicate that the times of substantial hydrodynamic effects are sporadic but significant. The simplified indicator parameter correlates much better with the hydrodynamic effect magnitude for a constant width channel such as Miami Canal than at the non-uniform North River. Higher HSN values indicate flow situations where the inertial terms are large and need to be taken into account.

  6. Effects of thermal fluctuations and fluid compressibility on hydrodynamic synchronization of microrotors at finite oscillatory Reynolds number: a multiparticle collision dynamics simulation study.

    PubMed

    Theers, Mario; Winkler, Roland G

    2014-08-28

    We investigate the emergent dynamical behavior of hydrodynamically coupled microrotors by means of multiparticle collision dynamics (MPC) simulations. The two rotors are confined in a plane and move along circles driven by active forces. Comparing simulations to theoretical results based on linearized hydrodynamics, we demonstrate that time-dependent hydrodynamic interactions lead to synchronization of the rotational motion. Thermal noise implies large fluctuations of the phase-angle difference between the rotors, but synchronization prevails and the ensemble-averaged time dependence of the phase-angle difference agrees well with analytical predictions. Moreover, we demonstrate that compressibility effects lead to longer synchronization times. In addition, the relevance of the inertia terms of the Navier-Stokes equation are discussed, specifically the linear unsteady acceleration term characterized by the oscillatory Reynolds number ReT. We illustrate the continuous breakdown of synchronization with the Reynolds number ReT, in analogy to the continuous breakdown of the scallop theorem with decreasing Reynolds number. PMID:25011003

  7. Full-coverage film cooling: 3-dimensional measurements of turbulence structure and prediction of recovery region hydrodynamics

    NASA Technical Reports Server (NTRS)

    Yavuzkurt, S.; Moffat, R. J.; Kays, W. M.

    1979-01-01

    Hydrodynamic measurements were made with a triaxial hot-wire in the full-coverage region and the recovery region following an array of injection holes inclined downstream, at 30 degrees to the surface. The data were taken under isothermal conditions at ambient temperature and pressure for two blowing ratios: M = 0.9 and M = 0.4. Profiles of the three main velocity components and the six Reynolds stresses were obtained at several spanwise positions at each of the five locations down the test plate. A one-equation model of turbulence (using turbulent kinetic energy with an algebraic mixing length) was used in a two-dimensional computer program to predict the mean velocity and turbulent kinetic energy profiles in the recovery region. A new real-time hotwire scheme was developed to make measurements in the three-dimensional turbulent boundary layer over the full-coverage surface.

  8. Predicting typhoon-induced storm surge tide with a two-dimensional hydrodynamic model and artificial neural network model

    NASA Astrophysics Data System (ADS)

    Chen, W.-B.; Liu, W.-C.; Hsu, M.-H.

    2012-12-01

    Precise predictions of storm surges during typhoon events have the necessity for disaster prevention in coastal seas. This paper explores an artificial neural network (ANN) model, including the back propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS) algorithms used to correct poor calculations with a two-dimensional hydrodynamic model in predicting storm surge height during typhoon events. The two-dimensional model has a fine horizontal resolution and considers the interaction between storm surges and astronomical tides, which can be applied for describing the complicated physical properties of storm surges along the east coast of Taiwan. The model is driven by the tidal elevation at the open boundaries using a global ocean tidal model and is forced by the meteorological conditions using a cyclone model. The simulated results of the hydrodynamic model indicate that this model fails to predict storm surge height during the model calibration and verification phases as typhoons approached the east coast of Taiwan. The BPNN model can reproduce the astronomical tide level but fails to modify the prediction of the storm surge tide level. The ANFIS model satisfactorily predicts both the astronomical tide level and the storm surge height during the training and verification phases and exhibits the lowest values of mean absolute error and root-mean-square error compared to the simulated results at the different stations using the hydrodynamic model and the BPNN model. Comparison results showed that the ANFIS techniques could be successfully applied in predicting water levels along the east coastal of Taiwan during typhoon events.

  9. Predicted macroinvertebrate response to water diversion from a montane stream using two-dimensional hydrodynamic models and zero flow approximation

    USGS Publications Warehouse

    Holmquist, Jeffrey G.; Waddle, Terry J.

    2013-01-01

    We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.

  10. Small-Scale Structures in Three-Dimensional Hydrodynamic and Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Meneguzzi, Maurice; Pouquet, Annick; Sulem, Pierre-Louis

    Small-scale structures in turbulent flows appear as a subtle mixture of order and chaos that could play an important role in the energetics. The aim here is a better understanding of the similarities and differences between vortex and current dynamics, and of the influence of these structures on the statistical and transport properties of hydrodynamic and magnetohydrodynamic turbulence, with special concern for fusion plasmas, and solar or magnetospheric environments. Special emphasis is given to the intermittency at inertial scales and to the coherent structures at small scales. Magnetic reconnection and the dynamo effect are also discussed, together with the effect of stratification and inhomogeneity. The impact of hydrodynamic concepts on astro and geophysical observations are reviewed.

  11. Thermal compression and characterization of three-dimensional nonwoven PET matrices as tissue engineering scaffolds.

    PubMed

    Li, Y; Ma, T; Yang, S T; Kniss, D A

    2001-03-01

    Nonwoven fibrous matrices have been widely used as scaffolds in tissue engineering, and modification of microstructure of these matrices is needed to organize cells in three-dimensional space with spatially balanced proliferation and differentiation required for functional tissue development. The method of thermal compression of nonwoven polyethylene terephthalate (PET) fabrics was developed and key parameters of temperature, pressure, and compression duration were evaluated in this study. The permanent deformation was obtained at elevated temperature under pressure and the viscoelastic compressional behaviors were observed, characterized by a distinct apparent modulus change in glass transition temperature region. A liquid extrusion method was further employed to analyze both pore size and its distribution for matrices with porosity ranging from 84 to 93%. It is also found that a more uniformly distributed pore size was resulted from thermal compression and the isotropic nature of nonwoven fabrics was preserved because of the proportional reduction of the pore by compression. The thermally compressed fabric matrices with two different pore sizes (15 and 20 microm in pore radius) were used to culture human trophoblast ED27 and NIH 3T3 cells. It was found that cells cultured in the different pore-size PET matrices had different cell spatial organization and proliferation rates. The smaller pores in the matrix allowed cells to spread better and proliferate faster, while cells in the larger pores tended to form large aggregates and had lower proliferation rate. The thermal compression technique also can be applied to other synthetic fibrous matrices including biodegradable polymers used in tissue engineering to modify the microstructure according to their viscoelastic properties. PMID:11219726

  12. Three-dimensional evolution of magnetic and velocity shear driven instabilities in a compressible magnetized jet

    NASA Astrophysics Data System (ADS)

    Bettarini, Lapo; Landi, Simone; Velli, Marco; Londrillo, Pasquale

    2009-06-01

    The problem of three-dimensional combined magnetic and velocity shear driven instabilities of a compressible magnetized jet modeled as a plane neutral/current double vortex sheet in the framework of the resistive magnetohydrodynamics is addressed. The resulting dynamics given by the stream+current sheet interaction is analyzed and the effects of a variable geometry of the basic fields are considered. Depending on the basic asymptotic magnetic field configuration, a selection rule of the linear instability modes can be obtained. Hence, the system follows a two-stage path developing either through a fully three-dimensional dynamics with a rapid evolution of kink modes leading to a final turbulent state, or rather through a driving two-dimensional instability pattern that develops on parallel planes on which a reconnection+coalescence process takes place.

  13. Three-dimensional evolution of magnetic and velocity shear driven instabilities in a compressible magnetized jet

    SciTech Connect

    Bettarini, Lapo; Landi, Simone; Velli, Marco; Londrillo, Pasquale

    2009-06-15

    The problem of three-dimensional combined magnetic and velocity shear driven instabilities of a compressible magnetized jet modeled as a plane neutral/current double vortex sheet in the framework of the resistive magnetohydrodynamics is addressed. The resulting dynamics given by the stream+current sheet interaction is analyzed and the effects of a variable geometry of the basic fields are considered. Depending on the basic asymptotic magnetic field configuration, a selection rule of the linear instability modes can be obtained. Hence, the system follows a two-stage path developing either through a fully three-dimensional dynamics with a rapid evolution of kink modes leading to a final turbulent state, or rather through a driving two-dimensional instability pattern that develops on parallel planes on which a reconnection+coalescence process takes place.

  14. On deformations of one-dimensional Poisson structures of hydrodynamic type with degenerate metric

    NASA Astrophysics Data System (ADS)

    Savoldi, Andrea

    2016-06-01

    We provide a complete list of two- and three-component Poisson structures of hydrodynamic type with degenerate metric, and study their homogeneous deformations. In the non-degenerate case any such deformation is trivial, that is, can be obtained via Miura transformations. We demonstrate that in the degenerate case this class of deformations is non-trivial, and depends on a certain number of arbitrary functions. This shows that the second Poisson-Lichnerowicz cohomology group does not vanish.

  15. Reconstructing high-dimensional two-photon entangled states via compressive sensing

    PubMed Central

    Tonolini, Francesco; Chan, Susan; Agnew, Megan; Lindsay, Alan; Leach, Jonathan

    2014-01-01

    Accurately establishing the state of large-scale quantum systems is an important tool in quantum information science; however, the large number of unknown parameters hinders the rapid characterisation of such states, and reconstruction procedures can become prohibitively time-consuming. Compressive sensing, a procedure for solving inverse problems by incorporating prior knowledge about the form of the solution, provides an attractive alternative to the problem of high-dimensional quantum state characterisation. Using a modified version of compressive sensing that incorporates the principles of singular value thresholding, we reconstruct the density matrix of a high-dimensional two-photon entangled system. The dimension of each photon is equal to d = 17, corresponding to a system of 83521 unknown real parameters. Accurate reconstruction is achieved with approximately 2500 measurements, only 3% of the total number of unknown parameters in the state. The algorithm we develop is fast, computationally inexpensive, and applicable to a wide range of quantum states, thus demonstrating compressive sensing as an effective technique for measuring the state of large-scale quantum systems. PMID:25306850

  16. Revisiting pyramid compression to quantify flexoelectricity: A three-dimensional simulation study

    NASA Astrophysics Data System (ADS)

    Abdollahi, Amir; Millán, Daniel; Peco, Christian; Arroyo, Marino; Arias, Irene

    2015-03-01

    Flexoelectricity is a universal property of all dielectrics by which they generate a voltage in response to an inhomogeneous deformation. One of the controversial issues in this field concerns the magnitude of flexoelectric coefficients measured experimentally, which greatly exceed theoretical estimates. Furthermore, there is a broad scatter amongst experimental measurements. The truncated pyramid compression method is one of the common setups to quantify flexoelectricity, the interpretation of which relies on simplified analytical equations to estimate strain gradients. However, the deformation fields in three-dimensional pyramid configurations are highly complex, particularly around its edges. In the present work, using three-dimensional self-consistent simulations of flexoelectricity, we show that the simplified analytical estimations of strain gradients in compressed pyramids significantly overestimate flexoelectric coefficients, thus providing a possible explanation to reconcile different estimates. In fact, the interpretation of pyramid compression experiments is highly nontrivial. We systematically characterize the magnitude of this overestimation, of over one order of magnitude, as a function of the truncated pyramid configuration. These results are important to properly characterize flexoelectricity, and provide design guidelines for effective electromechanical transducers exploiting flexoelectricity.

  17. Large-eddy simulation of a three-dimensional compressible tornado vortex

    NASA Astrophysics Data System (ADS)

    Xia, Jianjun

    Large-Eddy simulation (LES) has become a very useful tool for investigating tornadoes, one of the more spectacular and destructive phenomena of nature. A new three-dimensional, unsteady, compressible model is generated to determine how significant the differences between compressible and incompressible LES simulations may be in some extremely violent tornadoes. In particular, this study seeks to determine how high the Mach number within the tornado may become before significant changes occur due to compressibility, and what the major effects of these changes may be expected to be. After developing and verifying the compressible LES model, three different patterns of tornadic corner flows cataloged by local swirl ratio are simulated under quasisteady conditions for different Mach numbers. Simulation comparisons have demonstrated that the compressibility effects are different for different corner flow structures. At peak average Mach numbers less than approximately 0.5, the compressibility effects are not very significant and may be accounted for to leading order by an appropriate isentropic transformation applied to the incompressible results. As the maximum Mach number is increased to more than 1.0, the compressibility effects for low-swirl-ratio corner flows are dramatic, with significant increase in peak vertical velocity and the height of the vortex breakdown above the surface. The effects are much weaker for medium swirl conditions, and expected to be still weaker for high swirl corner flow where the effects are essentially limited to influencing the secondary vortices. In general, compressibility effects would not change the basic dynamics of tornadic corner flows even if Mach numbers greater than one are achieved. This study also shows that during the sharp temporal overshoot in near-surface intensity that can sometimes occur during a tornado's evolution, the maximum pressure drop will tend to be restricted by supersonic velocities, and thus limit the

  18. Quantum hydrodynamics approach to the formation of waves in polarized two-dimensional systems of charged and neutral particles

    SciTech Connect

    Andreev, P. A.; Kuzmenkov, L. S.; Trukhanova, M. I.

    2011-12-15

    In this paper, we explicate a method of quantum hydrodynamics (QHD) for the study of the quantum evolution of a system of polarized particles. Although we focused primarily on the two-dimensional (2D) physical systems, the method is valid for three-dimensional (3D) and one-dimensional (1D) systems too. The presented method is based upon the Schroedinger equation. Fundamental QHD equations for charged and neutral particles were derived from the many-particle microscopic Schroedinger equation. The fact that particles possess the electric dipole moment (EDM) was taken into account. The explicated QHD approach was used to study dispersion characteristics of various physical systems. We analyzed dispersion of waves in a two-dimensional ion and hole gas placed into an external electric field, which is orthogonal to the gas plane. Elementary excitations in a system of neutral polarized particles were studied for 1D, 2D, and 3D cases. The polarization dynamics in systems of both neutral and charged particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. We also analyzed wave dispersion in 2D exciton systems, in 2D electron-ion plasma, and in 2D electron-hole plasma. Generation of waves in 3D-system neutral particles with EDM by means of the beam of electrons and neutral polarized particles is investigated.

  19. Efficient computation of the stability of three-dimensional compressible boundary layers

    NASA Technical Reports Server (NTRS)

    Malik, M. R.; Orszag, S. A.

    1981-01-01

    Methods for the computer analysis of the stability of three-dimensional compressible boundary layers are discussed and the user-oriented Compressible Stability Analysis (COSAL) computer code is described. The COSAL code uses a matrix finite-difference method for local eigenvalue solution when a good guess for the eigenvalue is available and is significantly more computationally efficient than the commonly used initial-value approach. The local eigenvalue search procedure also results in eigenfunctions and, at little extra work, group velocities. A globally convergent eigenvalue procedure is also developed which may be used when no guess for the eigenvalue is available. The global problem is formulated in such a way that no unstable spurious modes appear so that the method is suitable for use in a black-box stability code. Sample stability calculations are presented for the boundary layer profiles of an LFC swept wing.

  20. Encrypted Three-dimensional Dynamic Imaging using Snapshot Time-of-flight Compressed Ultrafast Photography.

    PubMed

    Liang, Jinyang; Gao, Liang; Hai, Pengfei; Li, Chiye; Wang, Lihong V

    2015-01-01

    Compressed ultrafast photography (CUP), a computational imaging technique, is synchronized with short-pulsed laser illumination to enable dynamic three-dimensional (3D) imaging. By leveraging the time-of-flight (ToF) information of pulsed light backscattered by the object, ToF-CUP can reconstruct a volumetric image from a single camera snapshot. In addition, the approach unites the encryption of depth data with the compressed acquisition of 3D data in a single snapshot measurement, thereby allowing efficient and secure data storage and transmission. We demonstrated high-speed 3D videography of moving objects at up to 75 volumes per second. The ToF-CUP camera was applied to track the 3D position of a live comet goldfish. We have also imaged a moving object obscured by a scattering medium. PMID:26503834

  1. Compression of digital holograms for three-dimensional object reconstruction and recognition.

    PubMed

    Naughton, Thomas J; Frauel, Yann; Javidi, Bahram; Tajahuerce, Enrique

    2002-07-10

    We present the results of applying lossless and lossy data compression to a three-dimensional object reconstruction and recognition technique based on phase-shift digital holography. We find that the best lossless (Lempel-Ziv, Lempel-Ziv-Welch, Huffman, Burrows-Wheeler) compression rates can be expected when the digital hologram is stored in an intermediate coding of separate data streams for real and imaginary components. The lossy techniques are based on subsampling, quantization, and discrete Fourier transformation. For various degrees of speckle reduction, we quantify the number of Fourier coefficients that can be removed from the hologram domain, and the lowest level of quantization achievable, without incurring significant loss in correlation performance or significant error in the reconstructed object domain. PMID:12141512

  2. Compression of digital holograms for three-dimensional object reconstruction and recognition

    NASA Astrophysics Data System (ADS)

    Naughton, Thomas J.; Frauel, Yann; Javidi, Bahram; Tajahuerce, Enrique

    2002-07-01

    We present the results of applying lossless and lossy data compression to a three-dimensional object reconstruction and recognition technique based on phase-shift digital holography. We find that the best lossless (Lempel-Ziv, Lempel-Ziv-Welch, Huffman, Burrows-Wheeler) compression rates can be expected when the digital hologram is stored in an intermediate coding of separate data streams for real and imaginary components. The lossy techniques are based on subsampling, quantization, and discrete Fourier transformation. For various degrees of speckle reduction, we quantify the number of Fourier coefficients that can be removed from the hologram domain, and the lowest level of quantization achievable, without incurring significant loss in correlation performance or significant error in the reconstructed object domain.

  3. Study of Two-Dimensional Compressible Non-Acoustic Modeling of Stirling Machine Type Components

    NASA Technical Reports Server (NTRS)

    Tew, Roy C., Jr.; Ibrahim, Mounir B.

    2001-01-01

    A two-dimensional (2-D) computer code was developed for modeling enclosed volumes of gas with oscillating boundaries, such as Stirling machine components. An existing 2-D incompressible flow computer code, CAST, was used as the starting point for the project. CAST was modified to use the compressible non-acoustic Navier-Stokes equations to model an enclosed volume including an oscillating piston. The devices modeled have low Mach numbers and are sufficiently small that the time required for acoustics to propagate across them is negligible. Therefore, acoustics were excluded to enable more time efficient computation. Background information about the project is presented. The compressible non-acoustic flow assumptions are discussed. The governing equations used in the model are presented in transport equation format. A brief description is given of the numerical methods used. Comparisons of code predictions with experimental data are then discussed.

  4. A variational principle for compressible fluid mechanics. Discussion of the one-dimensional theory

    NASA Technical Reports Server (NTRS)

    Prozan, R. J.

    1982-01-01

    The second law of thermodynamics is used as a variational statement to derive a numerical procedure to satisfy the governing equations of motion. The procedure, based on numerical experimentation, appears to be stable provided the CFL condition is satisfied. This stability is manifested no matter how severe the gradients (compression or expansion) are in the flow field. For reasons of simplicity only one dimensional inviscid compressible unsteady flow is discussed here; however, the concepts and techniques are not restricted to one dimension nor are they restricted to inviscid non-reacting flow. The solution here is explicit in time. Further study is required to determine the impact of the variational principle on implicit algorithms.

  5. Encrypted Three-dimensional Dynamic Imaging using Snapshot Time-of-flight Compressed Ultrafast Photography

    PubMed Central

    Liang, Jinyang; Gao, Liang; Hai, Pengfei; Li, Chiye; Wang, Lihong V.

    2015-01-01

    Compressed ultrafast photography (CUP), a computational imaging technique, is synchronized with short-pulsed laser illumination to enable dynamic three-dimensional (3D) imaging. By leveraging the time-of-flight (ToF) information of pulsed light backscattered by the object, ToF-CUP can reconstruct a volumetric image from a single camera snapshot. In addition, the approach unites the encryption of depth data with the compressed acquisition of 3D data in a single snapshot measurement, thereby allowing efficient and secure data storage and transmission. We demonstrated high-speed 3D videography of moving objects at up to 75 volumes per second. The ToF-CUP camera was applied to track the 3D position of a live comet goldfish. We have also imaged a moving object obscured by a scattering medium. PMID:26503834

  6. Encrypted Three-dimensional Dynamic Imaging using Snapshot Time-of-flight Compressed Ultrafast Photography

    NASA Astrophysics Data System (ADS)

    Liang, Jinyang; Gao, Liang; Hai, Pengfei; Li, Chiye; Wang, Lihong V.

    2015-10-01

    Compressed ultrafast photography (CUP), a computational imaging technique, is synchronized with short-pulsed laser illumination to enable dynamic three-dimensional (3D) imaging. By leveraging the time-of-flight (ToF) information of pulsed light backscattered by the object, ToF-CUP can reconstruct a volumetric image from a single camera snapshot. In addition, the approach unites the encryption of depth data with the compressed acquisition of 3D data in a single snapshot measurement, thereby allowing efficient and secure data storage and transmission. We demonstrated high-speed 3D videography of moving objects at up to 75 volumes per second. The ToF-CUP camera was applied to track the 3D position of a live comet goldfish. We have also imaged a moving object obscured by a scattering medium.

  7. Multiscale molecular dynamics/hydrodynamics implementation of two dimensional "Mercedes Benz" water model

    NASA Astrophysics Data System (ADS)

    Scukins, A.; Nerukh, D.; Pavlov, E.; Karabasov, S.; Markesteijn, A.

    2015-09-01

    A multiscale Molecular Dynamics/Hydrodynamics implementation of the 2D Mercedes Benz (MB or BN2D) [1] water model is developed and investigated. The concept and the governing equations of multiscale coupling together with the results of the two-way coupling implementation are reported. The sensitivity of the multiscale model for obtaining macroscopic and microscopic parameters of the system, such as macroscopic density and velocity fluctuations, radial distribution and velocity autocorrelation functions of MB particles, is evaluated. Critical issues for extending the current model to large systems are discussed.

  8. Processing and properties of ceramic composites with three-dimensional architectures of thin compressive layers

    NASA Astrophysics Data System (ADS)

    Fair, Geoff Eric

    Threshold strength behavior and flaw insensitivity have recently been observed in laminar ceramic composites containing thick stress-free layers and thin layers in residual compression (due to thermal expansion mismatch). The threshold strength behavior is due to a crack tip shielding effect in which the stress intensity factor cracks initiating in the thick layers and propagating through the thin layers is reduced by the compressive stresses. Consequently, a well-defined level of stress (the threshold strength) is required to cause the cracks to propagate entirely through the compressive layers to cause failure of the specimens regardless of the initial flaw size. The threshold strength behavior is only observed in one loading orientation relative to the layers. The current work describes the processing procedures and fracture behavior of ceramic composites with three-dimensional architectures of thin compressive layers which are expected to exhibit threshold strength behavior in any tensile loading orientation and possess higher threshold strengths than laminates of similar architectural dimensions. Processing of the composites consists of producing spherical agglomerates, coating these agglomerates with a thin layer of material which upon heat treatment develops a residual compressive stress, and consolidating the coated agglomerates into bars suitable for mechanical testing. Finite element modeling of the residual stresses in the composite architecture is used to explain fracture behavior of the composites which is shown to depend on the architectural variables. Fractography of failed specimens is instrumental in elucidating the processing flaws within the architectures, one of the most pervasive of which is inter-agglomerate voids due to incomplete consolidation; additional processing steps are developed to remove these flaws and produce flaw-free composites suitable for a study of a flaw-insensitivity through the introduction of controlled flaws. Mechanical

  9. VALIDITY OF A TWO-DIMENSIONAL MODEL FOR VARIABLE-DENSITY HYDRODYNAMIC CIRCULATION

    EPA Science Inventory

    A three-dimensional model of temperatures and currents has been formulated to assist in the analysis and interpretation of the dynamics of stratified lakes. In this model, nonlinear eddy coefficients for viscosity and conductivities are included. A two-dimensional model (one vert...

  10. Three-dimensional compressible turbulent computations for a nondiffusing S-duct

    NASA Technical Reports Server (NTRS)

    Harloff, G. J.; Debonis, J. R.; Smith, C. F.; Bruns, J. E.

    1992-01-01

    The PARC3D code was used to compute the compressible turbulent flow within a three dimensional, nondiffusing S-duct. A frame of reference is provided for future computational fluid dynamics studies of internal flows with strong secondary flows and provides an understanding of the performance characteristics of a typical S-duct with attached flow. The predicted results, obtained with both H- and O-grids, are compared with the experimental wall pressure, static and total pressure fields, and velocity vectors. Additionally, computed boundary layer thickness, velocity profiles in wall coordinates, and skin friction values are presented.

  11. Quasiconservation laws for compressible three-dimensional Navier-Stokes flow.

    PubMed

    Gibbon, J D; Holm, D D

    2012-10-01

    We formulate the quasi-Lagrangian fluid transport dynamics of mass density ρ and the projection q=ω·∇ρ of the vorticity ω onto the density gradient, as determined by the three-dimensional compressible Navier-Stokes equations for an ideal gas, although the results apply for an arbitrary equation of state. It turns out that the quasi-Lagrangian transport of q cannot cross a level set of ρ. That is, in this formulation, level sets of ρ (isopycnals) are impermeable to the transport of the projection q. PMID:23214709

  12. Multi-dimensional modeling of the application of catalytic combustion to homogeneous charge compression ignition engine

    NASA Astrophysics Data System (ADS)

    Zeng, Wen; Xie, Maozhao

    2006-12-01

    The detailed surface reaction mechanism of methane on rhodium catalyst was analyzed. Comparisons between numerical simulation and experiments showed a basic agreement. The combustion process of homogeneous charge compression ignition (HCCI) engine whose piston surface has been coated with catalyst (rhodium and platinum) was numerically investigated. A multi-dimensional model with detailed chemical kinetics was built. The effects of catalytic combustion on the ignition timing, the temperature and CO concentration fields, and HC, CO and NOx emissions of the HCCI engine were discussed. The results showed the ignition timing of the HCCI engine was advanced and the emissions of HC and CO were decreased by the catalysis.

  13. An implicit three-dimensional Navier-Stokes solver for compressible flow

    NASA Technical Reports Server (NTRS)

    Yoon, Seokkwan; Kwak, Dochan

    1991-01-01

    A three-dimensional numerical method based on the lower-upper symmetric-Gauss-Seidel implicit scheme in conjunction with the flux-limited dissipation model is developed for solving the compressible Navier-Stokes equations. A new computer code which is based on this method requires only 9 microsec per grid-point per iteration on a single processor of a Cray YMP computer and executes at the sustained rate of 170 MFLOPS. A reduction of 4 orders of magnitude in the residual for a high Reynolds number flow using 230 K grid points is obtained in 24 minutes. The computational results compare well with available experimental data.

  14. Spatial heterogeneity in geothermally-influenced lakes derived from atmospherically corrected Landsat thermal imagery and three-dimensional hydrodynamic modelling

    NASA Astrophysics Data System (ADS)

    Allan, Mathew G.; Hamilton, David P.; Trolle, Dennis; Muraoka, Kohji; McBride, Christopher

    2016-08-01

    Atmospheric correction of Landsat 7 thermal data was carried out for the purpose of retrieval of lake skin water temperature in Rotorua lakes, and Lake Taupo, North Island, New Zealand. The effect of the atmosphere was modelled using four sources of atmospheric profile data as input to the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model. The retrieved skin water temperatures were validated using a high-frequency temperature sensor deployed from a monitoring buoy at the water surface of Lake Rotorua. The most accurate atmospheric correction method was with Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric profile data (root-mean-square-error, RMSE, 0.48 K), followed by radiosonde (0.52 K), Atmospheric Infrared Sounder (AIRS) Level 3 (0.54 K), and the NASA atmospheric correction parameter calculator (0.94 K). Retrieved water temperature was used for assessing spatial heterogeneity and accuracy of surface water temperature simulated with a three-dimensional (3-D) hydrodynamic model of Lake Rotoehu, located approximately 20 km east of Lake Rotorua. This comparison indicated that the model was suitable for reproducing the dominant horizontal variations in surface water temperature in the lake. This study demonstrated the potential of accurate satellite-based thermal monitoring to validate temperature outputs from 3-D hydrodynamic model simulations. It also provided atmospheric correction options for local and global applications of Landsat thermal data.

  15. Three-dimensional numerical simulation of hydrodynamic interactions between pectoral-fin vortices and body undulation in a swimming fish

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Lun; Ting, Shang-Chieh; Yeh, Meng-Kao; Yang, Jing-Tang

    2011-09-01

    We investigated numerically the hydrodynamic interactions between pectoral-fin vortices and body undulation in a fish swimming with carangiform locomotion at a Reynolds number of 3.3 × 104; the three-dimensional, viscous, incompressible, Navier-Stokes equations were solved with a finite-volume method. For a fish swimming with the pectoral fins abducted, we characterized the wake flow structures, forces, and power consumption with respect to various Strouhal numbers. The numerical results reveal that a pair of vortices is formed immediately behind the abducted pectoral fins of a swimming fish. There exist hydrodynamic interactions between the pectoral-fin vortices and the undulating fish body. For Strouhal numbers in a range 0.2-0.8, the body undulation impedes the shedding of pectoral-fin vortices, resulting in vortices closely attached to the pectoral fins. In contrast, for Strouhal number = 0.1, the pectoral-fin vortices are shed from the pectoral fins and drift downstream. The low-pressure suction forces arising from the shed pectoral-fin vortices facilitate lateral movements of the fish body, decreasing the power consumption. This phenomenon indicates the possibility for an actual fish to harvest energy from the shed pectoral-fin vortices.

  16. Calibration and validation of a two-dimensional hydrodynamic model of the Ohio River, Jefferson County, Kentucky

    USGS Publications Warehouse

    Wagner, C.R.; Mueller, D.S.

    2001-01-01

    The quantification of current patterns is an essential component of a Water Quality Analysis Simulation Program (WASP) application in a riverine environment. The U.S. Geological Survey (USGS) provided a field validated two-dimensional Resource Management Associates-2 (RMA-2) hydrodynamic model capable of quantifying the steady-flowpatterns in the Ohio River extending from river mile 590 to 630 for the Ohio River Valley Water Sanitation Commission (ORSANCO) water-quality modeling efforts on that reach. Because of the hydrodynamic complexities induced by McAlpine Locks and Dam (Ohio River mile 607), the model was split into two segments: an upstream reach, which extended from the dam upstream to the upper terminus of the study reach at Ohio River mile 590; and a downstream reach, which extended from the dam downstream to a lower terminus at Ohio River mile 636. The model was calibrated to a low-flow hydraulic survey (approximately 35,000 cubic feet per second (ft3/s)) and verified with data collected during a high-flow survey (approximately 390,000 ft3/s). The model calibration and validation process included matching water-surface elevations at 10 locations and velocity profiles at 30 cross sections throughout the study reach. Based on the calibration and validation results, the model is a representative simulation of the Ohio River steady-flow patterns below discharges of approximately 400,000 ft3/s.

  17. Entropy stable wall boundary conditions for the three-dimensional compressible Navier-Stokes equations

    NASA Astrophysics Data System (ADS)

    Parsani, Matteo; Carpenter, Mark H.; Nielsen, Eric J.

    2015-07-01

    Non-linear entropy stability and a summation-by-parts framework are used to derive entropy stable wall boundary conditions for the three-dimensional compressible Navier-Stokes equations. A semi-discrete entropy estimate for the entire domain is achieved when the new boundary conditions are coupled with an entropy stable discrete interior operator. The data at the boundary are weakly imposed using a penalty flux approach and a simultaneous-approximation-term penalty technique. Although discontinuous spectral collocation operators on unstructured grids are used herein for the purpose of demonstrating their robustness and efficacy, the new boundary conditions are compatible with any diagonal norm summation-by-parts spatial operator, including finite element, finite difference, finite volume, discontinuous Galerkin, and flux reconstruction/correction procedure via reconstruction schemes. The proposed boundary treatment is tested for three-dimensional subsonic and supersonic flows. The numerical computations corroborate the non-linear stability (entropy stability) and accuracy of the boundary conditions.

  18. WIND: Computer program for calculation of three dimensional potential compressible flow about wind turbine rotor blades

    NASA Technical Reports Server (NTRS)

    Dulikravich, D. S.

    1980-01-01

    A computer program is presented which numerically solves an exact, full potential equation (FPE) for three dimensional, steady, inviscid flow through an isolated wind turbine rotor. The program automatically generates a three dimensional, boundary conforming grid and iteratively solves the FPE while fully accounting for both the rotating cascade and Coriolis effects. The numerical techniques incorporated involve rotated, type dependent finite differencing, a finite volume method, artificial viscosity in conservative form, and a successive line overrelaxation combined with the sequential grid refinement procedure to accelerate the iterative convergence rate. Consequently, the WIND program is capable of accurately analyzing incompressible and compressible flows, including those that are locally transonic and terminated by weak shocks. The program can also be used to analyze the flow around isolated aircraft propellers and helicopter rotors in hover as long as the total relative Mach number of the oncoming flow is subsonic.

  19. Entropy Stable Wall Boundary Conditions for the Three-Dimensional Compressible Navier-Stokes Equations

    NASA Technical Reports Server (NTRS)

    Parsani, Matteo; Carpenter, Mark H.; Nielsen, Eric J.

    2015-01-01

    Non-linear entropy stability and a summation-by-parts framework are used to derive entropy stable wall boundary conditions for the three-dimensional compressible Navier-Stokes equations. A semi-discrete entropy estimate for the entire domain is achieved when the new boundary conditions are coupled with an entropy stable discrete interior operator. The data at the boundary are weakly imposed using a penalty flux approach and a simultaneous-approximation-term penalty technique. Although discontinuous spectral collocation operators on unstructured grids are used herein for the purpose of demonstrating their robustness and efficacy, the new boundary conditions are compatible with any diagonal norm summation-by-parts spatial operator, including finite element, finite difference, finite volume, discontinuous Galerkin, and flux reconstruction/correction procedure via reconstruction schemes. The proposed boundary treatment is tested for three-dimensional subsonic and supersonic flows. The numerical computations corroborate the non-linear stability (entropy stability) and accuracy of the boundary conditions.

  20. Numerical simulation of compressible Couette flow stability: Non-linear and three-dimensional effects

    NASA Astrophysics Data System (ADS)

    Saati, Abdulmannan Abdulhamid

    1991-02-01

    The direct numerical simulation of the stability and transition of compressible Couette flow is studied. The effects of a constant body force along the vertical direction are also studied. Cartesian geometry is adopted to approximate Couette flow produced in the gap between two coaxial cylinders rotating at high-speed, with the body force representing the effects of the centrifugal force. A new, compressible flow solver for two- and three-dimensional, time dependent Navier-Stokes equations, using both the MacCormack and the high-order Two-Four methods was developed. In order to facilitate the simulations with greater detail and accuracy, a high-speed supercomputer with large core memory is required. Thus, the computer code was written in FORTRAN for its execution on the CRAY2, at NASA Langley. In a concurrent effort, in order to study the feasibility and efficiency of massively parallel super-computers and to speed up the computations, the work was further extended by rewriting the computer code in both C* and PARIS languages, for execution on the massively parallel Connection Machine CM 2 at the University of Colorado. Extensive testing of this new computer code was performed using wave propagation problems involving small- and large-amplitude two- and three-dimensional disturbances. Numerical simulations on the stability of compressible Couette flow between two infinite, parallel plates, with the inclusion of (1) a sudden body force, and (2) a body force in equilibrium, were performed. First, two-dimensional disturbances were considered and then the work was extended by considering three-dimensional disturbances on the rectangular Couette flow problem. Effects of body force magnitude, Mach number, and Reynolds number were also investigated. The simulations provide excellent agreement with the linear theory, thus documenting the phase and amplitude accuracy of the computed results; the overall amplitude error remains less than one percent. The results show that

  1. Two-dimensional electromagnetic quantum-hydrodynamic simulations of isochoric heating of a solid target by proton beams

    SciTech Connect

    Zhang, Ya; Jiang, Wei; Song, Yuan-Hong; Wang, You-Nian

    2015-02-15

    Isochoric heating of an aluminum target by proton beams has been studied with a two-dimensional self-consistent electromagnetic quantum-hydrodynamic model, including the nonlinear quantum effects. It is shown that most protons deposit their energy within several micrometers near the surface, and the aluminum metal target is heated up to several electron volts in tens of Mbar pressure regime within one picosecond. Comparison between electrostatic and electromagnetic cases shows that the strength of electromagnetic field is much smaller than that of the electrostatic field at initial stage but increases more rapidly and becomes larger at later time. The results show that the time evolution of electric field has a significant influence on the interaction of intense beams with a solid target, while the effect of the self-magnetic field is small for non-relativistic beams considered here.

  2. A three-dimensional model of co-rotating streams in the solar wind. 2: Hydrodynamic streams

    NASA Technical Reports Server (NTRS)

    Pizzo, V. J.

    1979-01-01

    Theoretical aspects of corotating solar wind dynamics on a global scale are explored by means of numerical simulations executed with a nonlinear, inviscid, adiabatic, single-fluid, three-dimensional (3-D) hydrodynamic formulation. A simple, hypothetical 3-D stream structure is defined on a source surface located at 35 solar radius and carefully documents its evolution to 1 AU under the influence of solar rotation. By manipulating the structure of this prototype configuration at the source surface, it is possible to elucidate the factors most strongly affecting stream evolution: (1) the intrinsic correlations among density, temperature, and velocity existing near the source; (2) the amplitude of the stream; (3) the longitudinal breadth of the stream; (4) the latitudinal breadth of the stream; and (5) the heliographic latitude of the centroid of the stream.

  3. User's manual for DYNA2D: an explicit two-dimensional hydrodynamic finite-element code with interactive rezoning

    SciTech Connect

    Hallquist, J.O.

    1982-02-01

    This revised report provides an updated user's manual for DYNA2D, an explicit two-dimensional axisymmetric and plane strain finite element code for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. A contact-impact algorithm permits gaps and sliding along material interfaces. By a specialization of this algorithm, such interfaces can be rigidly tied to admit variable zoning without the need of transition regions. Spatial discretization is achieved by the use of 4-node solid elements, and the equations-of motion are integrated by the central difference method. An interactive rezoner eliminates the need to terminate the calculation when the mesh becomes too distorted. Rather, the mesh can be rezoned and the calculation continued. The command structure for the rezoner is described and illustrated by an example.

  4. Compressed simulation of thermal and excited states of the one-dimensional X Y model

    NASA Astrophysics Data System (ADS)

    Boyajian, W. L.; Kraus, B.

    2015-09-01

    Since several years, the preparation and manipulation of a small number of quantum systems in a controlled and coherent way is feasible in many experiments. In fact, these experiments are nowadays commonly used for quantum simulation and quantum computation. As recently shown, such a system can, however, also be utilized to simulate specific behaviors of exponentially larger systems. That is, certain quantum computations can be performed by an exponentially smaller quantum computer. This compressed quantum computation can be employed to observe, for instance, the quantum phase transition of the one-dimensional (1D) X Y model using very few qubits. We extend here this notion to simulate the behavior of thermal as well as excited states of the 1D X Y model. In particular, we consider the 1D X Y model of a spin chain of n qubits and derive a quantum circuit processing only log(n ) qubits which simulates the original system. We demonstrate how the behavior of thermal as well as any eigenstate of the system can be efficiently simulated in this compressed fashion and present a quantum circuit on log(n ) qubits to measure the magnetization, the number of kinks, and correlations occurring in the thermal as well as any excited state of the original systems. Moreover, we derive compressed circuits to study time evolutions.

  5. Turbulence models and Reynolds analogy for two-dimensional supersonic compression ramp flow

    NASA Technical Reports Server (NTRS)

    Wang, Chi R.; Bidek, Maleina C.

    1994-01-01

    Results of the application of turbulence models and the Reynolds analogy to the Navier-Stokes computations of Mach 2.9 two-dimensional compression ramp flows are presented. The Baldwin-Lomax eddy viscosity model and the kappa-epsilon turbulence transport equations for the turbulent momentum flux modeling in the Navier-Stokes equations are studied. The Reynolds analogy for the turbulent heat flux modeling in the energy equation was also studied. The Navier-Stokes equations and the energy equation were numerically solved for the flow properties. The Reynolds shear stress, the skin friction factor, and the surface heat transfer rate were calculated and compared with their measurements. It was concluded that with a hybrid kappa-epsilon turbulence model for turbulence modeling, the present computations predicted the skin friction factors of the 8 deg and 16 deg compression ramp flows and with the turbulent Prandtl number Pr(sub t) = 0.93 and the ratio of the turbulent thermal and momentum transport coefficients mu(sub q)/mu(sub t) = 2/Prt, the present computations also predicted the surface heat transfer rates beneath the boundary layer flow of the 16 compression ramp.

  6. Multi-dimensional hydrodynamic simulations aimed at characterizing heavily aluminized RDX

    NASA Astrophysics Data System (ADS)

    Yoh, Jack J.; Kim, Bohoon; Kim, Minsung

    2015-06-01

    An accurate and reliable prediction of reactive flow is a challenging task for an energetic material subjected to an external shock impact. The present study aims at simulating the shock induced detonation of heavily aluminized RDX which contains 35% of aluminum. A series of gap tests with the longitudinal simulations involving gap substances are conducted to understand the inherent initiation process that depends on the shock propagation through multi-material domain and the high strain dynamics of nearby confinement materials. A pressure chamber test is used to validate the blast wave calculation of the sample charge, and a full 3-D hydrodynamic simulation is performed to predict fragmentation of an explosively loaded steel casing. The paper provides an elaborate description of how a heavily aluminized RDX is characterized in terms of its thermo-chemical response and multi-material interaction with inert confinement materials.

  7. Three-dimensional model of a plasma railgun using smoothed particle hydrodynamics

    NASA Astrophysics Data System (ADS)

    Jackson, Lloyd M.

    Pulsed plasma accelerators are utilized for in-space propulsion and drivers for inertial fusion concepts. Theoretical models are necessary to assist in diagnostic analysis and for developing scaling laws. SPFMax is a new 3D code which uses smoothed particle hydrodynamics (SPH) to simulate fluid flow, and has been designed specifically for modeling plasmas produced by these pulsed devices. A set of gasdynamic test cases were established and utilized to verify the accuracy of SPFMax for modeling the gas dynamics in a railgun. The free expansion confirmed that the gas expands supersonically without exceeding the predicted maximum value. With the square wave test, SPFMax advected the waves with floating point accuracy. Shocks, expansion waves, and contact surfaces were resolved in both 1D and 3D tests with a relatively low number of particles.

  8. Radiological image compression using error-free irreversible two-dimensional direct-cosine-transform coding techniques.

    PubMed

    Huang, H K; Lo, S C; Ho, B K; Lou, S L

    1987-05-01

    Some error-free and irreversible two-dimensional direct-cosine-transform (2D-DCT) coding, image-compression techniques applied to radiological images are discussed in this paper. Run-length coding and Huffman coding are described, and examples are given for error-free image compression. In the case of irreversible 2D-DCT coding, the block-quantization technique and the full-frame bit-allocation (FFBA) technique are described. Error-free image compression can achieve a compression ratio from 2:1 to 3:1, whereas the irreversible 2D-DCT coding compression technique can, in general, achieve a much higher acceptable compression ratio. The currently available block-quantization hardware may lead to visible block artifacts at certain compression ratios, but FFBA may be employed with the same or higher compression ratios without generating such artifacts. An even higher compression ratio can be achieved if the image is compressed by using first FFBA and then Huffman coding. The disadvantages of FFBA are that it is sensitive to sharp edges and no hardware is available. This paper also describes the design of the FFBA technique. PMID:3598750

  9. Three-dimensional hydrodynamic Bondi-Hoyle accretion. 2: Homogeneous medium at Mach 3 with gamma = 5/3

    NASA Technical Reports Server (NTRS)

    Ruffert, Maximilian; Arnett, David

    1994-01-01

    We investigate the hydrodynamics of three-dimensional classical Bondi-Hoyle accretion. Totally absorbing spheres of varying sizes (from 10 down to 0.01 accretion radii) move at Mach 3 relative to a homogeneous and slightly perturbed medium, which is taken to be an ideal gas (gamma = 5/3). To accommodate the long-range gravitational forces, the extent of the computational volume is 32(exp 3) accretion radii. We examine the influence of numerical procedure on physical behavior. The hydrodynamics is modeled by the 'piecewise parabolic method.' No energy sources (nuclear burning) or sinks (radiation, conduction) are included. The resolution in the vicinity of the accretor is increased by multiply nesting several (5-10) grids around the sphere, each finer grid being a factor of 2 smaller in zone dimension that the next coarser grid. The largest dynamic range (ratio of size of the largest grid to size of the finest zone) is 16,384. This allows us to include a coarse model for the surface of the accretor (vacuum sphere) on the finest grid, while at the same time evolving the gas on the coarser grids. Initially (at time t = 0-10), a shock front is set up, a Mach cone develops, and the accretion column is observable. Eventually the flow becomes unstable, destroying axisymmetry. This happens approximately when the mass accretion rate reaches the values (+/- 10%) predicted by the Bondi-Hoyle accretion formula (factor of 2 included). However, our three-dimensional models do not show the highly dynamic flip-flop flow so prominent in two-dimensional calculations performed by other authors. The flow, and thus the accretion rate of all quantities, shows quasi-periodic (P approximately equals 5) cycles between quiescent and active states. The interpolation formula proposed in an accompanying paper is found to follow the collected numerical data to within approximately 30%. The specific angular momentum accreted is of the same order of magnitude as the values previously found for

  10. Geothermal well behaviour prediction after air compress stimulation using one-dimensional transient numerical modelling

    NASA Astrophysics Data System (ADS)

    Yusman, W.; Viridi, S.; Rachmat, S.

    2016-01-01

    The non-discharges geothermal wells have been a main problem in geothermal development stages and well discharge stimulation is required to initiate a flow. Air compress stimulation is one of the methods to trigger a fluid flow from the geothermal reservoir. The result of this process can be predicted by using by the Af / Ac method, but sometimes this method shows uncertainty result in several geothermal wells and also this prediction method does not take into account the flowing time of geothermal fluid to discharge after opening the well head. This paper presents a simulation of non-discharges well under air compress stimulation to predict well behavior and time process required. The component of this model consists of geothermal well data during heating-up process such as pressure, temperature and mass flow in the water column and main feed zone level. The one-dimensional transient numerical model is run based on the Single Fluid Volume Element (SFVE) method. According to the simulation result, the geothermal well behavior prediction after air compress stimulation will be valid under two specific circumstances, such as single phase fluid density between 1 - 28 kg/m3 and above 28.5 kg/m3. The first condition shows that successful well discharge and the last condition represent failed well discharge after air compress stimulation (only for two wells data). The comparison of pf values between simulation and field observation shows the different result according to the success discharge well. Time required for flow to occur as observed in well head by using the SFVE method is different with the actual field condition. This model needs to improve by updating more geothermal well data and modified fluid phase condition inside the wellbore.

  11. EFDC1D - A ONE DIMENSIONAL HYDRODYNAMIC AND SEDIMENT TRANSPORT MODEL FOR RIVER AND STREAM NETWORKS: MODEL THEORY AND USERS GUIDE

    EPA Science Inventory

    This technical report describes the new one-dimensional (1D) hydrodynamic and sediment transport model EFDC1D. This model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. EFDC1D can simulate bi-directional unstea...

  12. Horizontally propagating three-dimensional chemo-hydrodynamic patterns in the chlorite-tetrathionate reaction

    NASA Astrophysics Data System (ADS)

    Pópity-Tóth, Éva; Horváth, Dezső; Tóth, Ágota

    2012-09-01

    Planar reaction fronts resulting from the coupling of exothermic autocatalytic reactions and transport processes can be deformed by convection in the presence of gravity field. We have experimentally investigated how buoyancy affects the spatiotemporal pattern formation at various solution thicknesses in three-dimensional medium. In the chlorite-tetrathionate reaction, a stable structure propagating horizontally with constant velocity and geometry develops when appropriately thick solutions are studied. Both the horizontal and the vertical projections of the resulting three-dimensional structures are quantitatively characterized: the smooth leading edge of the front is independent of the solution thickness and the structured trailing edge ends in a center cusp with a constant angle.

  13. Improved non-local electron thermal transport model for two-dimensional radiation hydrodynamics simulations

    SciTech Connect

    Cao, Duc; Moses, Gregory; Delettrez, Jacques

    2015-08-15

    An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the model's effect on DRACO's predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester.

  14. A numerical study of the Navier-Stokes transport coefficients for two-dimensional granular hydrodynamics

    NASA Astrophysics Data System (ADS)

    Almazán, Lidia; Carrillo, José A.; Salueña, Clara; Garzó, Vicente; Pöschel, Thorsten

    2013-04-01

    A numerical study that aims to analyze the thermal mechanisms of unsteady, supersonic granular flow by means of hydrodynamic simulations of the Navier-Stokes granular equation is reported in this paper. For this purpose, a paradigmatic problem in granular dynamics such as the Faraday instability is selected. Two different approaches for the Navier-Stokes transport coefficients for granular materials are considered, namely the traditional Jenkins-Richman theory for moderately dense quasi-elastic grains and the improved Garzó-Dufty-Lutsko theory for arbitrary inelasticity, which we also present here. Both the solutions are compared with event-driven simulations of the same system under the same conditions, by analyzing the density, temperature and velocity field. Important differences are found between the two approaches, leading to interesting implications. In particular, the heat transfer mechanism coupled to the density gradient, which is a distinctive feature of inelastic granular gases, is responsible for a major discrepancy in the temperature field and hence in the diffusion mechanisms.

  15. Improved non-local electron thermal transport model for two-dimensional radiation hydrodynamics simulations

    NASA Astrophysics Data System (ADS)

    Cao, Duc; Moses, Gregory; Delettrez, Jacques

    2015-08-01

    An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the model's effect on DRACO's predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester.

  16. A two-dimensional hydrodynamic model of the St. Clair-Detroit River waterway in the Great Lakes basin

    USGS Publications Warehouse

    Holtschlag, David J.; Koschik, John A.

    2002-01-01

    The St. Clair-Detroit River waterway connects Lake Huron with Lake Erie in the Great Lakes basin to form part of the international boundary between the United States and Canada. A two-dimensional hydrodynamic model is developed to compute flow velocities and water levels as part of a source water assessment of public water intakes. The model, which uses the generalized finite-element code RMA2, discretizes the waterway into a mesh formed by 13,783 quadratic elements defined by 42,936 nodes. Seven steady-state scenarios are used to calibrate the model by adjusting parameters associated with channel roughness in 25 material zones. An inverse modeling code is used to systematically adjust model parameters and to determine their associated uncertainty by use of nonlinear regression. Calibration results show close agreement between simulated and expected flows in major channels and water levels at gaging stations. Sensitivity analyses describe the amount of information available to estimate individual model parameters, and quantify the utility of flow measurements at selected cross sections and water-level measurements at gaging stations. Further data collection, model calibration analysis, and grid refinements are planned to assess and enhance two-dimensional flow simulation capabilities describing the horizontal flow distributions in St. Clair and Detroit Rivers and circulation patterns in Lake St. Clair.

  17. An implicit method for two-dimensional hydrodynamics. [in stellar evolution

    NASA Technical Reports Server (NTRS)

    Livne, Eli

    1993-01-01

    An implicit method for compressible multidimensional flows is presented. The method, which is strongly oriented toward astrophysical applications, enables one to simulate very subsonic flows by removing the Courant condition upon time steps. It consists of an implicit purely Lagrangian step, followed by an explicit and second-order accurate (at least in one dimension) remapping step, which is optional. When the remapping step is performed the time step is limited by the 'particle crossing time' and otherwise it is limited only by accuracy considerations. The suggested method, which results from a compromise between accuracy and efficiency, is very efficient relative to other methods. It enables the computation of many multidimensional problems in stellar evolution, such as those governed by very subsonic flows, which were not calculable with existing explicit methods.

  18. Three-Dimensional Numerical Simulation of Mold Filling Process in Compression Resin Transfer Molding

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Jin, Tianguo; Li, Jianguang; Bi, Fengyang

    2015-04-01

    Compression resin transfer molding (CRTM) is an effective process for the manufacturing of composite parts with large size and high fiber content, while the existence of open gap, the dynamically changing dimensions of cavity geometry and the deformation of preform during filling process bring great difficulties to the three-dimensional simulation of resin flow in CRTM. In order to develop a convenient and efficient three-dimensional simulation approach for CRTM filling process, a unified mathematical model for resin flow in both open gap and preform is established instead of considering the gap as high permeability preform, then the analysis of the clamping force and stress distribution are presented. In order to avoid direct solving the coupled equations of resin flow and cavity deformation, volume of fluid (VOF) multiphase flow technology and dynamic mesh model are applied to track the resin flow front and update the cavity geometry during filling simulation, respectively. The master-slave element method is used to modify the amount of resin release and ensure the resin mass conservation. The validity of the numerical approach is verified by comparison with analytical and experimental results, three-dimensional simulation examples are also presented.

  19. SOLA-STAR: a one-dimensional ICED-ALE hydrodynamics program for spherically symmetric flows

    SciTech Connect

    Cloutman, L.D.

    1980-07-01

    This report describes a simple, general-purpose, and efficient algorithm for solving one-dimensional spherically symmetric, transient fluid-dynamics problems using a variation of the ICED-ALE technique. Included are the finite difference equations, three test problems that illustrate various capabilities of the program, and a complete code description, including a listing, sample data decks and output, a summary of important variable names, and hints for conversion to other operating systems.

  20. Two-dimensional simulations of thermonuclear burn in ignition-scale inertial confinement fusion targets under compressed axial magnetic fields

    SciTech Connect

    Perkins, L. J.; Logan, B. G.; Zimmerman, G. B.; Werner, C. J.

    2013-07-15

    We report for the first time on full 2-D radiation-hydrodynamic implosion simulations that explore the impact of highly compressed imposed magnetic fields on the ignition and burn of perturbed spherical implosions of ignition-scale cryogenic capsules. Using perturbations that highly convolute the cold fuel boundary of the hotspot and prevent ignition without applied fields, we impose initial axial seed fields of 20–100 T (potentially attainable using present experimental methods) that compress to greater than 4 × 10{sup 4} T (400 MG) under implosion, thereby relaxing hotspot areal densities and pressures required for ignition and propagating burn by ∼50%. The compressed field is high enough to suppress transverse electron heat conduction, and to allow alphas to couple energy into the hotspot even when highly deformed by large low-mode amplitudes. This might permit the recovery of ignition, or at least significant alpha particle heating, in submarginal capsules that would otherwise fail because of adverse hydrodynamic instabilities.

  1. Chemistry in the First Hydrostatic Core Stage by Adopting Three-dimensional Radiation Hydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Furuya, Kenji; Aikawa, Yuri; Tomida, Kengo; Matsumoto, Tomoaki; Saigo, Kazuya; Tomisaka, Kohji; Hersant, Franck; Wakelam, Valentine

    2012-10-01

    We investigate molecular evolution from a molecular cloud core to a first hydrostatic core in three spatial dimensions. We perform a radiation hydrodynamic simulation in order to trace fluid parcels, in which molecular evolution is investigated, using a gas-phase and grain-surface chemical reaction network. We derive spatial distributions of molecular abundances and column densities in the molecular cloud core harboring the first core. We find that the total gas and ice abundances of many species in a cold era (10 K) remain unaltered until the temperature reaches ~500 K. The gas abundances in the warm envelope and the outer layer of the first core (T <~ 500 K) are mainly determined via the sublimation of ice-mantle species. Above 500 K, the abundant molecules, such as H2CO, start to be destroyed, and simple molecules, such as CO, H2O, and N2, are reformed. On the other hand, some molecules are effectively formed at high temperature; carbon chains, such as C2H2 and cyanopolyynes, are formed at temperatures >700 K. We also find that large organic molecules, such as CH3OH and HCOOCH3, are associated with the first core (r <~ 10 AU). Although the abundances of these molecules in the first core stage are comparable to or less than in the protostellar stage (hot corino), reflecting the lower luminosity of the central object, their column densities in our model are comparable to the observed values toward the prototypical hot corino, IRAS 16293-2422. We propose that these large organic molecules can be good tracers of the first cores.

  2. Hydrodynamics of paper making: Streamwise vortices generated upstream of a two-dimensional jet nozzle

    NASA Astrophysics Data System (ADS)

    Hsu, Tsun-Ya

    The hydrodynamic stability of initially laminar flow in a 2D jet was investigated. The motivation for this study was understanding the effects of jet geometry and turbulence in the papermaking process. Utilizing the digital particle image velocimetry (DPIV) technique, eight experimental cases were conducted in a 2D jet. The jet exit had a vertical blockage as much as 50% of the jet height. Two grid size screens, 0.73 x 0.73cm2 and 1.11 x 1.11 cm2, were used as turbulence generators. The Reynolds number range, based on the momentum thickness and the free stream velocity 1-2ms , varied from 960 to 5500. Streamwise vortices occurred due to shear induced by the presence of the blockage. The size of the vortices was 0.5--1 cm, which is nearly proportional to the streak spacing found in a sheet of paper. With the presence of a turbulence generator, streamwise vortices still exist. The 0.73 x 0.73cm2 size turbulence generator had a greater effect on reducing the strength of the streamwise vortices than the 1.11 x 1.11cm2 size turbulence generator. The size of a mean spanwise vortex, located at the corner formed by the upper wall and the blockage, was found to be one half the length of the blockage. The study suggests that the streamwise vortices do not result from the streaks in the turbulent boundary layer, nor from the Gortler vortices. The spanwise and streamwise vortices are likely the product of inflexional instability.

  3. Two-dimensional radiation hydrodynamics simulations of superluminous interacting supernovae of Type IIn

    NASA Astrophysics Data System (ADS)

    Vlasis, Alkiviadis; Dessart, Luc; Audit, Edouard

    2016-05-01

    Some interacting supernovae (SNe) of Type IIn show a sizeable continuum polarization suggestive of a large-scale asymmetry in the circumstellar medium (CSM) and/or the SN ejecta. Here, we extend the recent work of Dessart et al. on superluminous SNe IIn and perform axially-symmetric (i.e. 2D) multigroup radiation hydrodynamics simulations to explore the impact of an imposed large-scale density asymmetry. When the CSM is asymmetric, the latitudinal variation of the radial optical depth τ introduces a strong flux redistribution from the higher density CSM regions, where the shock luminosity is larger, towards the lower density CSM regions where photons escape more freely - this redistribution ceases when τ ≲ 1. Along directions where the CSM density is larger, the shock deceleration is stronger and its progression slower, producing a non-spherical cold-dense shell (CDS). For an oblate CSM density distribution, the photosphere (CDS) has an oblate (prolate) morphology when τ ≳ 1. When the CSM is symmetric and the ejecta asymmetric, the flux redistribution within the CSM now tends to damp the latitudinal variation of the luminosity at the shock. It then requires a larger ejecta asymmetry to produce a sizeable latitudinal variation in the emergent flux. When the interaction is between a SN ejecta and a relic disc, the luminosity boost at early times scales with the disc opening angle - forming a superluminous SN IIn this way requires an unrealistically thick disc. In contrast, interaction with a disc of modest thickness/mass can yield a power that rivals radioactive decay of a standard SN II at nebular times.

  4. Three-dimensional simulations of ablative hydrodynamic instabilities in indirectly driven targets

    SciTech Connect

    Marinak, M.M.; Tipton, R.E.; Remington, B.A.

    1996-06-01

    To model ignition in a National Ignition Facility (NIF) capsule implosion, the authors must understand the behavior of instabilities that can cause breakup of the pellet shell. During a capsule implosion, shocks that transit the shell cause growth of perturbations at the surface or at an interface because of a Richtmyer-Meshkov type of instability. Following shock breakout, or earlier for a shaped pulse, the low-density ablated plasma accelerates the pusher, and the ablation front is Rayleigh-Taylor (RT) unstable. Ablation and finite density gradients have the effect of stabilizing the short wavelength modes. Unstable modes present on the outer surface grow and feed through to the inner surface. Once the shell encounters the rebounding shock from the capsule center, it decelerates and the inner surface becomes RT unstable. If perturbations grow large enough, pusher material mixes into the core, degrading implosion performance. Capsule designs for the NIF depend on ablative stabilization and saturation to prevent perturbations initially present on the capsule surface from growing large enough to quench ignition. Here, the authors examine the first simulations and experiments to study the effect of 3-D perturbation shape on instability growth and saturation in indirectly driven targets. The first section discusses HYDRA, the radiation hydrodynamics code developed for these simulations. The subsequent section examines 3-D shape effects in single-mode perturbations in planar foil simulations and experiments. A discussion of the evolution of multimode perturbations on planar foils is followed by a discussion of 3-D simulations of instability growth in Nova capsule implosions.

  5. CHEMISTRY IN THE FIRST HYDROSTATIC CORE STAGE BY ADOPTING THREE-DIMENSIONAL RADIATION HYDRODYNAMIC SIMULATIONS

    SciTech Connect

    Furuya, Kenji; Aikawa, Yuri; Tomida, Kengo; Tomisaka, Kohji; Matsumoto, Tomoaki; Saigo, Kazuya; Hersant, Franck; Wakelam, Valentine

    2012-10-20

    We investigate molecular evolution from a molecular cloud core to a first hydrostatic core in three spatial dimensions. We perform a radiation hydrodynamic simulation in order to trace fluid parcels, in which molecular evolution is investigated, using a gas-phase and grain-surface chemical reaction network. We derive spatial distributions of molecular abundances and column densities in the molecular cloud core harboring the first core. We find that the total gas and ice abundances of many species in a cold era (10 K) remain unaltered until the temperature reaches {approx}500 K. The gas abundances in the warm envelope and the outer layer of the first core (T {approx}< 500 K) are mainly determined via the sublimation of ice-mantle species. Above 500 K, the abundant molecules, such as H{sub 2}CO, start to be destroyed, and simple molecules, such as CO, H{sub 2}O, and N{sub 2}, are reformed. On the other hand, some molecules are effectively formed at high temperature; carbon chains, such as C{sub 2}H{sub 2} and cyanopolyynes, are formed at temperatures >700 K. We also find that large organic molecules, such as CH{sub 3}OH and HCOOCH{sub 3}, are associated with the first core (r {approx}< 10 AU). Although the abundances of these molecules in the first core stage are comparable to or less than in the protostellar stage (hot corino), reflecting the lower luminosity of the central object, their column densities in our model are comparable to the observed values toward the prototypical hot corino, IRAS 16293-2422. We propose that these large organic molecules can be good tracers of the first cores.

  6. Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling

    NASA Astrophysics Data System (ADS)

    Xu, Sheng; Yan, Zheng; Jang, Kyung-In; Huang, Wen; Fu, Haoran; Kim, Jeonghyun; Wei, Zijun; Flavin, Matthew; McCracken, Joselle; Wang, Renhan; Badea, Adina; Liu, Yuhao; Xiao, Dongqing; Zhou, Guoyan; Lee, Jungwoo; Chung, Ha Uk; Cheng, Huanyu; Ren, Wen; Banks, Anthony; Li, Xiuling; Paik, Ungyu; Nuzzo, Ralph G.; Huang, Yonggang; Zhang, Yihui; Rogers, John A.

    2015-01-01

    Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations.

  7. Pressure, compressibility, and contact of the two-dimensional attractive fermi gas.

    PubMed

    Anderson, E R; Drut, J E

    2015-09-11

    Using ab initio lattice methods, we calculate the finite temperature thermodynamics of homogeneous two-dimensional spin-1/2 fermions with attractive short-range interactions. We present results for the density, pressure, compressibility, and quantum anomaly (i.e., Tan's contact) for a wide range of temperatures (mostly above the superfluid phase, including the pseudogap regime) and coupling strengths, focusing on the unpolarized case. Within our statistical and systematic uncertainties, our prediction for the density equation of state differs quantitatively from the prediction by Luttinger-Ward theory in the strongly coupled region of parameter space, but otherwise agrees well with it. We also compare our calculations with the second- and third-order virial expansion, with which they are in excellent agreement in the low-fugacity regime. PMID:26406837

  8. Materials science. Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling.

    PubMed

    Xu, Sheng; Yan, Zheng; Jang, Kyung-In; Huang, Wen; Fu, Haoran; Kim, Jeonghyun; Wei, Zijun; Flavin, Matthew; McCracken, Joselle; Wang, Renhan; Badea, Adina; Liu, Yuhao; Xiao, Dongqing; Zhou, Guoyan; Lee, Jungwoo; Chung, Ha Uk; Cheng, Huanyu; Ren, Wen; Banks, Anthony; Li, Xiuling; Paik, Ungyu; Nuzzo, Ralph G; Huang, Yonggang; Zhang, Yihui; Rogers, John A

    2015-01-01

    Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations. PMID:25574018

  9. Flame four-dimensional deflection tomography with compressed-sensing-revision reconstruction

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Zhao, Minmin; Liu, Zhigang; Wu, Zhaohang

    2016-08-01

    Deflection tomography with limited angle projections was investigated to visualize a premixed flame. A projection sampling system for deflection tomography was used to obtain chronological deflectogram arrays at six view angles with only a pair of gratings. A new iterative reconstruction algorithm with deflection angle compressed-sensing revision was developed to improve reconstruction-distribution quality from incomplete projection data. Numerical simulation and error analysis provided a good indication of algorithm precision and convergence. In the experiment, 150 fringes were processed, and temperature distributions in 20 cross-sections were reconstructed from projection data in four instants. Four-dimensional flame structures and temperature distributions in the flame interior were visualized using the visualization toolkit. The experimental reconstruction was then compared with the result obtained from computational fluid dynamic analysis.

  10. Computation of Three-Dimensional Compressible Flow From a Rectangular Nozzle with Delta Tabs

    NASA Technical Reports Server (NTRS)

    Reddy, D. R.; Steffen, C. J., Jr.; Zaman, K. B. M. Q.

    1999-01-01

    A three-dimensional viscous flow analysis is performed using a time-marching Reynolds-averaged Navier-Stokes code for a 3:1 rectangular nozzle with two delta tabs located at the nozz1e exit plane to enhance mixing. Two flow configurations, a subsonic jet case and a supersonic jet case using the same rate configuration, which were previously studied experimentally, are computed and compared with the experimental data. The experimental data include streamwise velocity and vorticity distributions for the subsonic case, and Mach number distributions for the supersonic case, at various axial locations downstream of the nozzle exit. The computational results show very good agreement with the experimental data. In addition, the effect of compressibility on vorticity dynamics is examined by comparing the vorticity contours of the subsonic jet case with those of the supersonic jet case which were not measured in the experiment.

  11. An experimental investigation of compressible three-dimensional boundary layer flow in annular diffusers

    NASA Technical Reports Server (NTRS)

    Om, Deepak; Childs, Morris E.

    1987-01-01

    An experimental study is described in which detailed wall pressure measurements have been obtained for compressible three-dimensional unseparated boundary layer flow in annular diffusers with and without normal shock waves. Detailed mean flow-field data were also obtained for the diffuser flow without a shock wave. Two diffuser flows with shock waves were investigated. In one case, the normal shock existed over the complete annulus whereas in the second case, the shock existed over a part of the annulus. The data obtained can be used to validate computational codes for predicting such flow fields. The details of the flow field without the shock wave show flow reversal in the circumferential direction on both inner and outer surfaces. However, there is a lag in the flow reversal between the inner nad the outer surfaces. This is an interesting feature of this flow and should be a good test for the computational codes.

  12. Pressure, Compressibility, and Contact of the Two-Dimensional Attractive Fermi Gas

    NASA Astrophysics Data System (ADS)

    Anderson, E. R.; Drut, J. E.

    2015-09-01

    Using ab initio lattice methods, we calculate the finite temperature thermodynamics of homogeneous two-dimensional spin-1 /2 fermions with attractive short-range interactions. We present results for the density, pressure, compressibility, and quantum anomaly (i.e., Tan's contact) for a wide range of temperatures (mostly above the superfluid phase, including the pseudogap regime) and coupling strengths, focusing on the unpolarized case. Within our statistical and systematic uncertainties, our prediction for the density equation of state differs quantitatively from the prediction by Luttinger-Ward theory in the strongly coupled region of parameter space, but otherwise agrees well with it. We also compare our calculations with the second- and third-order virial expansion, with which they are in excellent agreement in the low-fugacity regime.

  13. Experimental and computational studies of two-dimensional compressible vortex-shock interaction

    NASA Astrophysics Data System (ADS)

    Kao, Chun-Teh

    The problem of two-dimensional compressible vortex-shock interaction is studied both experimentally and numerically. On the experimental side, a strong compressible vortex and a shock wave are produced in the open test section of a shock tube. The shock wave of strength M ≈ 1.2 then collides with the vortex that possesses a density drop at the vortex center exceeding 60% of the free stream value. Shadowgraphs and schlieren pictures of the event are taken in a sequence of experiments with progressive time delays. The pictures show that the shock profile is significantly modified by the interaction, with substantial distortion, disconnection, and a local nonlinear focusing structure. In the computational work, both the Euler equations and the Navier-Stokes equations are solved to simulate the problem. Two flux-splitting techniques are employed: (1) first-order-accurate Modified Steger-Warming method and (2) second-order-accurate variable-extrapolation method satisfying the total-variation-diminishing (TVD) condition. Based on the numerical data, the respective behaviors of the vortex, the shock wave, and the secondary wave generated during the interaction are analyzed. The simulation also reveals that the focal region of the distorted shock structure is bounded by a Mach stem and two slipstreams, in which local intensified pressure, density, and temperature peaks occur. It is found that the local intensification of fluid properties and the secondary wave possess essentially nonlinear characteristics at their early stages. The computational results agree well, qualitatively, with the experimental observations.

  14. SASI ACTIVITY IN THREE-DIMENSIONAL NEUTRINO-HYDRODYNAMICS SIMULATIONS OF SUPERNOVA CORES

    SciTech Connect

    Hanke, Florian; Mueller, Bernhard; Wongwathanarat, Annop; Marek, Andreas; Janka, Hans-Thomas E-mail: bjmuellr@mpa-garching.mpg.de E-mail: amarek@mpa-garching.mpg.de

    2013-06-10

    The relevance of the standing accretion shock instability (SASI) compared to neutrino-driven convection in three-dimensional (3D) supernova-core environments is still highly controversial. Studying a 27 M{sub Sun} progenitor, we demonstrate, for the first time, that violent SASI activity can develop in 3D simulations with detailed neutrino transport despite the presence of convection. This result was obtained with the PROMETHEUS-VERTEX code with the same sophisticated neutrino treatment so far used only in one-dimensional and two-dimensional (2D) models. While buoyant plumes initially determine the nonradial mass motions in the postshock layer, bipolar shock sloshing with growing amplitude sets in during a phase of shock retraction and turns into a violent spiral mode whose growth is only quenched when the infall of the Si/SiO interface leads to strong shock expansion in response to a dramatic decrease of the mass accretion rate. In the phase of large-amplitude SASI sloshing and spiral motions, the postshock layer exhibits nonradial deformation dominated by the lowest-order spherical harmonics (l = 1, m = 0, {+-}1) in distinct contrast to the higher multipole structures associated with neutrino-driven convection. We find that the SASI amplitudes, shock asymmetry, and nonradial kinetic energy in three dimensions can exceed those of the corresponding 2D case during extended periods of the evolution. We also perform parameterized 3D simulations of a 25 M{sub Sun} progenitor, using a simplified, gray neutrino transport scheme, an axis-free Yin-Yang grid, and different amplitudes of random seed perturbations. They confirm the importance of the SASI for another progenitor, its independence of the choice of spherical grid, and its preferred growth for fast accretion flows connected to small shock radii and compact proto-neutron stars as previously found in 2D setups.

  15. Magnetic dynamo action in two-dimensional turbulent magneto-hydrodynamics

    NASA Technical Reports Server (NTRS)

    Fyfe, D.; Joyce, G.; Montgomery, D.

    1977-01-01

    Two-dimensional magnetohydrodynamic turbulence is explored by means of numerical simulation. Previous analytical theory, based on non-dissipative constants of the motion in a truncated Fourier representation, is verified by following the evolution of highly non-equilibrium initial conditions numerically. Dynamo action (conversion of a significant fraction of turbulent kinetic energy into long-wavelength magnetic field energy) is observed. It is conjectured that in the presence of dissipation and external forcing, a dual cascade will be observed for zero-helicity situations. Energy will cascade to higher wavenumbers simultaneously with a cascade of mean square vector potential to lower wavenumbers, leading to an omni-directional magnetic energy spectrum.

  16. Three-dimensional hydrodynamics of the deceleration stage in inertial confinement fusion

    SciTech Connect

    Weber, C. R. Clark, D. S.; Cook, A. W.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Marinak, M. M.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.; Thomas, C. A.

    2015-03-15

    The deceleration stage of inertial confinement fusion implosions is modeled in detail using three-dimensional simulations designed to match experiments at the National Ignition Facility. In this final stage of the implosion, shocks rebound from the center of the capsule, forming the high-temperature, low-density hot spot and slowing the incoming fuel. The flow field that results from this process is highly three-dimensional and influences many aspects of the implosion. The interior of the capsule has high-velocity motion, but viscous effects limit the range of scales that develop. The bulk motion of the hot spot shows qualitative agreement with experimental velocity measurements, while the variance of the hot spot velocity would broaden the DT neutron spectrum, increasing the inferred temperature by 400–800 eV. Jets of ablator material are broken apart and redirected as they enter this dynamic hot spot. Deceleration stage simulations using two fundamentally different rad-hydro codes are compared and the flow field is found to be in good agreement.

  17. Magnetic dynamo action in two-dimensional turbulent magneto-hydrodynamics

    NASA Technical Reports Server (NTRS)

    Fyfe, D.; Joyce, G.; Montgomery, D.

    1976-01-01

    Two-dimensional magnetohydrodynamic turbulence is explored by means of numerical simulation. Previous analytical theory, based on non-dissipative constants of the motion in a truncated Fourier representation, is verified by following the evolution of highly non-equilibrium initial conditions numerically. Dynamo action (conversion of a significant fraction of turbulent kinetic energy into long-wavelength magnetic field energy) is observed. It is conjectured that in the presence of dissipation and external forcing, a dual cascade will be observed for zero-helicity situations. Energy will cascade to higher wave numbers simultaneously with a cascade of mean square vector potential to lower wave numbers, leading to an omni-directional magnetic energy spectrum which varies as 1/k 3 at lower wave numbers, simultaneously with a buildup of magnetic excitation at the lowest wave number of the system. Equipartition of kinetic and magnetic energies is expected at the highest wave numbers in the system.

  18. Radiation hydrodynamics modeling of the highest compression inertial confinement fusion ignition experiment from the National Ignition Campaign

    NASA Astrophysics Data System (ADS)

    Clark, D. S.; Marinak, M. M.; Weber, C. R.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.; Thomas, C. A.

    2015-02-01

    The recently completed National Ignition Campaign (NIC) on the National Ignition Facility (NIF) showed significant discrepancies between post-shot simulations of implosion performance and experimentally measured performance, particularly in thermonuclear yield. This discrepancy between simulation and observation persisted despite concerted efforts to include all of the known sources of performance degradation within a reasonable two-dimensional (2-D), and even three-dimensional (3-D), simulation model, e.g., using measured surface imperfections and radiation drives adjusted to reproduce observed implosion trajectories [Clark et al., Phys. Plasmas 20, 056318 (2013)]. Since the completion of the NIC, several effects have been identified that could explain these discrepancies and that were omitted in previous simulations. In particular, there is now clear evidence for larger than anticipated long-wavelength radiation drive asymmetries and a larger than expected perturbation seeded by the capsule support tent. This paper describes an updated suite of one-dimensional (1-D), 2-D, and 3-D simulations that include the current best understanding of these effects identified since the NIC, as applied to a specific NIC shot. The relative importance of each effect on the experimental observables is compared. In combination, these effects reduce the simulated-to-measured yield ratio from 125:1 in 1-D to 1.5:1 in 3-D, as compared to 15:1 in the best 2-D simulations published previously. While the agreement with the experimental data remains imperfect, the comparison to the data is significantly improved and suggests that the largest sources for the previous discrepancies between simulation and experiment are now being included.

  19. Radiation hydrodynamics modeling of the highest compression inertial confinement fusion ignition experiment from the National Ignition Campaign

    SciTech Connect

    Clark, D. S.; Marinak, M. M.; Weber, C. R.; Eder, D. C.; Haan, S. W.; Hammel, B. A.; Hinkel, D. E.; Jones, O. S.; Milovich, J. L.; Patel, P. K.; Robey, H. F.; Salmonson, J. D.; Sepke, S. M.; Thomas, C. A.

    2015-02-15

    The recently completed National Ignition Campaign (NIC) on the National Ignition Facility (NIF) showed significant discrepancies between post-shot simulations of implosion performance and experimentally measured performance, particularly in thermonuclear yield. This discrepancy between simulation and observation persisted despite concerted efforts to include all of the known sources of performance degradation within a reasonable two-dimensional (2-D), and even three-dimensional (3-D), simulation model, e.g., using measured surface imperfections and radiation drives adjusted to reproduce observed implosion trajectories [Clark et al., Phys. Plasmas 20, 056318 (2013)]. Since the completion of the NIC, several effects have been identified that could explain these discrepancies and that were omitted in previous simulations. In particular, there is now clear evidence for larger than anticipated long-wavelength radiation drive asymmetries and a larger than expected perturbation seeded by the capsule support tent. This paper describes an updated suite of one-dimensional (1-D), 2-D, and 3-D simulations that include the current best understanding of these effects identified since the NIC, as applied to a specific NIC shot. The relative importance of each effect on the experimental observables is compared. In combination, these effects reduce the simulated-to-measured yield ratio from 125:1 in 1-D to 1.5:1 in 3-D, as compared to 15:1 in the best 2-D simulations published previously. While the agreement with the experimental data remains imperfect, the comparison to the data is significantly improved and suggests that the largest sources for the previous discrepancies between simulation and experiment are now being included.

  20. OFF-AXIS GAMMA-RAY BURST AFTERGLOW MODELING BASED ON A TWO-DIMENSIONAL AXISYMMETRIC HYDRODYNAMICS SIMULATION

    SciTech Connect

    Van Eerten, Hendrik; Zhang Weiqun; MacFadyen, Andrew

    2010-10-10

    Starting as highly relativistic collimated jets, gamma-ray burst outflows gradually slow down and become nonrelativistic spherical blast waves. Although detailed analytical solutions describing the afterglow emission received by an on-axis observer during both the early and late phases of the outflow evolution exist, a calculation of the received flux during the intermediate phase and for an off-axis observer requires either a more simplified analytical model or direct numerical simulations of the outflow dynamics. In this paper, we present light curves for off-axis observers covering the long-term evolution of the blast wave, calculated from a high-resolution two-dimensional relativistic hydrodynamics simulation using a synchrotron radiation model. We compare our results to earlier analytical work and calculate the consequence of the observer angle with respect to the jet axis both for the detection of orphan afterglows and for jet break fits to the observational data. We confirm earlier results in the literature finding that only a very small number of local type Ibc supernovae can harbor an orphan afterglow. For off-axis observers, the observable jet break can be delayed up to several weeks, potentially leading to overestimation of the beaming-corrected total energy. In addition we find that, when using our off-axis light curves to create synthetic Swift X-ray data, jet breaks are likely to remain hidden in the data.

  1. Three-dimensional Hydrodynamical Simulations of the Supernovae-driven Gas Loss in the Dwarf Spheroidal Galaxy Ursa Minor

    NASA Astrophysics Data System (ADS)

    Caproni, A.; Lanfranchi, G. A.; da Silva, A. Luiz; Falceta-Gonçalves, D.

    2015-06-01

    As is usual in dwarf spheroidal galaxies, today the Local Group galaxy Ursa Minor is depleted of its gas content. How this galaxy lost its gas is still a matter of debate. To study the history of gas loss in Ursa Minor, we conducted the first three-dimensional hydrodynamical simulations of this object, assuming that the gas loss was driven by galactic winds powered only by type II supernovae (SNe II). The initial gas setup and supernova (SN) rates used in our simulations are mainly constrained by the inferred star formation history and the observed velocity dispersion of Ursa Minor. After 3 Gyr of evolution, we found that the gas removal efficiency is higher when the SN rate is increased, and also when the initial mean gas density is lowered. The derived mass-loss rates are systematically higher in the central regions (\\lt 300 pc), even though such a relationship has not been strictly linear in time and in terms of the galactic radius. The filamentary structures induced by Rayleigh-Taylor instabilities and the concentric shells related to the acoustic waves driven by SNe can account for the inferred mass losses from the simulations. Our results suggest that SNe II are able to transfer most of the gas from the central region outward to the galactic halo. However, other physical mechanisms must be considered in order to completely remove the gas at larger radii.

  2. Assessing factors affecting the thermal properties of a passive thermal refuge using three-dimensional hydrodynamic flow and transport modeling

    USGS Publications Warehouse

    Decker, Jeremy D.; Swain, Eric D.; Stith, Bradley M.; Langtimm, Catherine A.

    2013-01-01

    Everglades restoration activities may cause changes to temperature and salinity stratification at the Port of the Islands (POI) marina, which could affect its suitability as a cold weather refuge for manatees. To better understand how the Picayune Strand Restoration Project (PSRP) may alter this important resource in Collier County in southwestern Florida, the USGS has developed a three-dimensional hydrodynamic model for the marina and canal system at POI. Empirical data suggest that manatees aggregate at the site during winter because of thermal inversions that provide warmer water near the bottom that appears to only occur in the presence of salinity stratification. To study these phenomena, the environmental fluid dynamics code simulator was used to represent temperature and salinity transport within POI. Boundary inputs were generated using a larger two-dimensional model constructed with the flow and transport in a linked overland-aquifer density-dependent system simulator. Model results for a representative winter period match observed trends in salinity and temperature fluctuations and produce temperature inversions similar to observed values. Modified boundary conditions, representing proposed PSRP alterations, were also tested to examine the possible effect on the salinity stratification and temperature inversion within POI. Results show that during some periods, salinity stratification is reduced resulting in a subsequent reduction in temperature inversion compared with the existing conditions simulation. This may have an effect on POI’s suitability as a passive thermal refuge for manatees and other temperature-sensitive species. Additional testing was completed to determine the important physical relationships affecting POI’s suitability as a refuge.

  3. Three-dimensional radiation-hydrodynamics calculations of the envelopes of young planets embedded in protoplanetary disks

    SciTech Connect

    D'Angelo, Gennaro; Bodenheimer, Peter E-mail: peter@ucolick.org

    2013-11-20

    We perform global three-dimensional (3D) radiation-hydrodynamics calculations of the envelopes surrounding young planetary cores of 5, 10, and 15 Earth masses, located in a protoplanetary disk at 5 and 10 AU from a solar-mass star. We apply a nested-grid technique to resolve the thermodynamics of the disk at the orbital-radius length scale and that of the envelope at the core-radius length scale. The gas is modeled as a solar mixture of molecular and atomic hydrogen, helium, and their ions. The equation of state accounts for both gas and radiation, and gas energy includes contributions from rotational and vibrational states of molecular hydrogen and from ionization of atomic species. Dust opacities are computed from first principles, applying the full Mie theory. One-dimensional (1D) calculations of planet formation are used to supplement the 3D calculations by providing energy deposition rates in the envelope due to solids accretion. We compare 1D and 3D envelopes and find that masses and gas accretion rates agree within factors of 2, and so do envelope temperatures. The trajectories of passive tracers are used to define the size of 3D envelopes, resulting in radii much smaller than the Hill radius and smaller than the Bondi radius. The moments of inertia and angular momentum of the envelopes are determined and the rotation rates are derived from the rigid-body approximation, resulting in slow bulk rotation. We find that the polar flattening is ≲ 0.05. The dynamics of the accretion flow are examined by tracking the motion of tracers that move into the envelope. The anisotropy of this flow is characterized in terms of both its origin and impact site at the envelope surface. Gas merges with the envelope preferentially at mid- to high latitudes.

  4. Uniform Regularity and Vanishing Dissipation Limit for the Full Compressible Navier-Stokes System in Three Dimensional Bounded Domain

    NASA Astrophysics Data System (ADS)

    Wang, Yong

    2016-09-01

    In the present paper, we study the uniform regularity and vanishing dissipation limit for the full compressible Navier-Stokes system whose viscosity and heat conductivity are allowed to vanish at different orders. The problem is studied in a three dimensional bounded domain with Navier-slip type boundary conditions. It is shown that there exists a unique strong solution to the full compressible Navier-Stokes system with the boundary conditions in a finite time interval which is independent of the viscosity and heat conductivity. The solution is uniformly bounded in {W^{1,infty}} and is a conormal Sobolev space. Based on such uniform estimates, we prove the convergence of the solutions of the full compressible Navier-Stokes to the corresponding solutions of the full compressible Euler system in {L^infty(0,T; L^2)}, {L^infty(0,T; H1)} and {L^infty([0,T]×Ω)} with a rate of convergence.

  5. Calibration of a two-dimensional hydrodynamic model for parts of the Allegheny, Monongahela, and Ohio Rivers, Allegheny County, Pennsylvania

    USGS Publications Warehouse

    Fulton, John W.; Wagner, Chad R.

    2014-01-01

    The U.S. Geological Survey (USGS), in cooperation with the Allegheny County Sanitary Authority, developed a validated two-dimensional Resource Management Associates2 (RMA2) hydrodynamic model of parts of the Allegheny, Monongahela, and Ohio Rivers (Three Rivers) to help assess the effects of combined sewer overflows (CSOs) and sanitary sewer overflows (SSOs) on the rivers. The hydrodynamic model was used to drive a water-quality model of the study area that was capable of simulating the transport and fate of fecal-indicator bacteria and chemical constituents under open-water conditions. The study area includes 14 tributary streams and parts of the Three Rivers where they enter and exit Allegheny County, an area of approximately 730 square miles (mi2). The city of Pittsburgh is near the center of the county, where the Allegheny and Monongahela Rivers join to form the headwaters of the Ohio River. The Three Rivers are regulated by a series of fixed-crest dams, gated dams, and radial (tainter) gates and serve as the receiving waters for tributary streams, CSOs, and SSOs. The RMA2 model was separated into four individual segments on the basis of the U.S. Army Corps of Engineers navigational pools in the study area (Dashields; Emsworth; Allegheny River, Pool 2; and Braddock), which were calibrated individually using measured water-surface slope, velocity, and discharge during high- and low-flow conditions. The model calibration process included the comparison of water-surface elevations at five locations and velocity profiles at more than 80 cross sections in the study area. On the basis of the calibration and validation results that included water-surface elevations and velocities, the model is a representative simulation of the Three Rivers flow patterns for discharges ranging from 4,050 to 47,400 cubic feet per second (ft3/s) on the Allegheny River, 2,550 to 40,000 ft3/s on the Monongahela River, and 10,900 to 99,000 ft3/s on the Ohio River. The Monongahela River was

  6. Classification of neurovascular compression in glossopharyngeal neuralgia: Three-dimensional visualization of the glossopharyngeal nerve

    PubMed Central

    Tanrikulu, Levent; Hastreiter, Peter; Dörfler, Arnd; Buchfelder, Michael; Naraghi, Ramin

    2015-01-01

    Background: We introduce a method of noninvasive topographical analysis of the neurovascular relationships of the glossopharyngeal nerve (CN IX) by three-dimensional (3D) visualization. Patients with glossopharyngeal neuralgia (GN) resulting from neurovascular compression (NVC) were studied. Methods: 15 patients with GN were prospectively examined with 3D visualization using high-resolution magnetic resonance imaging with constructive interference in steady state (MR-CISS). The datasets were segmented and visualized with the real, individual neurovascular relationships by direct volume rendering. Segmentation and 3D visualization of the CN IX and corresponding blood vessels were performed. The 3D visualizations were interactively compared with the intraoperative setup during microvascular decompression (MVD) in order to verify the results by the observed surgical-anatomical findings. Results: 15 patients (female/male: 5/10) were examined. All of them underwent MVD (100%). Microvascular details were documented. The posterior inferior cerebellar artery (PICA) was the most common causative vessel in 12 of 15 patients (80%), the vertebral artery (VA) alone in one case (6.7%), and the combination of compression by the VA and PICA in 3 patients (13.3%). We identified three distinct types of NVC within the root entry zone of CN IX. Conclusion: 3D visualization by direct volume rendering of MR-CISS data offers the opportunity of noninvasive exploration and anatomical categorization of the CN IX. It proves to be advantageous in supporting to establish the diagnosis and microneurosurgical interventions by representing original, individual patient data in a 3D fashion. It provides an excellent global individual view over the entire neurovascular relationships of the brainstem and corresponding nerves in each case. PMID:26759734

  7. WIND- THREE DIMENSIONAL POTENTIAL COMPRESSIBLE FLOW ABOUT WIND TURBINE ROTOR BLADES

    NASA Technical Reports Server (NTRS)

    Dulikravich, D. S.

    1994-01-01

    This computer program, WIND, was developed to numerically solve the exact, full-potential equation for three-dimensional, steady, inviscid flow through an isolated wind turbine rotor. The program automatically generates a three-dimensional, boundary-conforming grid and iteratively solves the full-potential equation while fully accounting for both the rotating and Coriolis effects. WIND is capable of numerically analyzing the flow field about a given blade shape of the horizontal-axis type wind turbine. The rotor hub is assumed representable by a doubly infinite circular cylinder. An arbitrary number of blades may be attached to the hub and these blades may have arbitrary spanwise distributions of taper and of the twist, sweep, and dihedral angles. An arbitrary number of different airfoil section shapes may be used along the span as long as the spanwise variation of all the geometeric parameters is reasonably smooth. The numerical techniques employed in WIND involve rotated, type-dependent finite differencing, a finite volume method, artificial viscosity in conservative form, and a successive overrelaxation combined with the sequential grid refinement procedure to accelerate the iterative convergence rate. Consequently, WIND is cabable of accurately analyzing incompressible and compressible flows, including those that are locally transonic and terminated by weak shocks. Along with the three-dimensional results, WIND provides the results of the two-dimensional calculations to aid the user in locating areas of possible improvement in the aerodynamic design of the blade. Output from WIND includes the chordwise distribution of the coefficient of pressure, the Mach number, the density, and the relative velocity components at spanwise stations along the blade. In addition, the results specify local values of the lift coefficient and the tangent and axial aerodynamic force components. These are also given in integrated form expressing the total torque and the total axial

  8. Global well-posedness of strong solutions to the two-dimensional barotropic compressible Navier-Stokes equations with vacuum

    NASA Astrophysics Data System (ADS)

    Fang, Li; Guo, Zhenhua

    2016-04-01

    The aim of this paper is to establish the global well-posedness and large-time asymptotic behavior of the strong solution to the Cauchy problem of the two-dimensional compressible Navier-Stokes equations with vacuum. It is proved that if the shear viscosity {μ} is a positive constant and the bulk viscosity {λ} is the power function of the density, that is, {λ=ρ^{β}} with {β in [0,1],} then the Cauchy problem of the two-dimensional compressible Navier-Stokes equations admits a unique global strong solution provided that the initial data are of small total energy. This result can be regarded as the extension of the well-posedness theory of classical compressible Navier-Stokes equations [such as Huang et al. (Commun Pure Appl Math 65:549-585, 2012) and Li and Xin (http://arxiv.org/abs/1310.1673) respectively]. Furthermore, the large-time behavior of the strong solution to the Cauchy problem of the two-dimensional barotropic compressible Navier-Stokes equations had been also obtained.

  9. Application of the Analogy Between Water Flow with a Free Surface and Two-dimensional Compressible Gas Flow

    NASA Technical Reports Server (NTRS)

    Orlin, W James; Lindner, Norman J; Bitterly, Jack G

    1947-01-01

    The theory of hydraulic analogy, that is, the analogy between water flow with a free surface and two-dimensional compressible gas flow and the limitations and conditions of the analogy are discussed. A test run was made using the hydraulic analogy as applied to the flow about circular cylinders at various diameters at subsonic velocities extending to the super critical range. The apparatus and techniques used in this application are described and criticized. Reasonably satisfactory agreement of pressure distributions and flow fields existed between water and airflow about corresponding bodies. This agreement indicated the possibility of extending experimental compressibility research by new methods.

  10. Application of the Analogy Between Water Flow with a Free Surface and Two-Dimensional Compressible Gas Flow

    NASA Technical Reports Server (NTRS)

    Orlin, W James; Lindner, Norman J; Butterly, Jack G

    1947-01-01

    The theory of the hydraulic analogy -- that is, the analogy between water flow with a free surface and two-dimensional compressible gas flow -- and the limitations and conditions of the analogy are discussed. A test was run using the hydraulic analogy as applied to the flow about circular cylinders of various diameters at subsonic velocities extending into the supercritical range. The apparatus and techniques used in this application are described and criticized. Reasonably satisfactory agreement of pressure distributions and flow fields existed between water and air flow about corresponding bodies. This agreement indicated the possibility of extending experimental compressibility research by new methods.

  11. COSAL: A black-box compressible stability analysis code for transition prediction in three-dimensional boundary layers

    NASA Technical Reports Server (NTRS)

    Malik, M. R.

    1982-01-01

    A fast computer code COSAL for transition prediction in three dimensional boundary layers using compressible stability analysis is described. The compressible stability eigenvalue problem is solved using a finite difference method, and the code is a black box in the sense that no guess of the eigenvalue is required from the user. Several optimization procedures were incorporated into COSAL to calculate integrated growth rates (N factor) for transition correlation for swept and tapered laminar flow control wings using the well known e to the Nth power method. A user's guide to the program is provided.

  12. Nonstandard Analysis and Shock Wave Jump Conditions in a One-Dimensional Compressible Gas

    NASA Technical Reports Server (NTRS)

    Baty, Roy S.; Farassat, Fereidoun; Hargreaves, John

    2007-01-01

    Nonstandard analysis is a relatively new area of mathematics in which infinitesimal numbers can be defined and manipulated rigorously like real numbers. This report presents a fairly comprehensive tutorial on nonstandard analysis for physicists and engineers with many examples applicable to generalized functions. To demonstrate the power of the subject, the problem of shock wave jump conditions is studied for a one-dimensional compressible gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. To use conservations laws, smooth pre-distributions of the Dirac delta measure are applied whose supports are contained within the shock thickness. Furthermore, smooth pre-distributions of the Heaviside function are applied which vary from zero to one across the shock wave. It is shown that if the equations of motion are expressed in nonconservative form then the relationships between the jump functions for the flow parameters may be found unambiguously. The analysis yields the classical Rankine-Hugoniot jump conditions for an inviscid shock wave. Moreover, non-monotonic entropy jump conditions are obtained for both inviscid and viscous flows. The report shows that products of generalized functions may be defined consistently using nonstandard analysis; however, physically meaningful products of generalized functions must be determined from the physics of the problem and not the mathematical form of the governing equations.

  13. Two-dimensional compressible flow in centrifugal compressors with straight blades

    NASA Technical Reports Server (NTRS)

    Stanitz, John D; Ellis, Gaylord O

    1950-01-01

    Six numerical examples are presented for steady, two-dimensional, compressible, nonviscous flow in centrifugal compressors with thin straight blades, the center lines of which generate the surface of a right circular cone when rotated about the axis of the compressor. A seventh example is presented for incompressible flow. The solutions were obtained in a region of the compressors, including the impeller tip, that was considered to be unaffected by the diffuser vanes or by the impeller-inlet configuration. Each solution applies to radial and mixed flow compressors with various cone angles but with the same angle between blades on the conic flow surface. The solution also apply to radial and mixed flow turbines with the rotation and the flow direction reversed. The effects of variations in the following parameters were investigated: (1) flow rate, (2) impeller-tip speed, (3) variation of passage height with radius, and (4) angle between blades on conic flow surface. The numerical results are presented in plots of the streamlines and constant Mach number lines. Correlation equations are developed whereby the flow conditions in any impeller with straight blades can be determined (in the region investigated by this analysis) for all operating conditions.

  14. A three dimensional lattice model for thermal compressible flow on standard lattices

    NASA Astrophysics Data System (ADS)

    Feng, Yongliang; Sagaut, Pierre; Tao, Wenquan

    2015-12-01

    A three-dimensional double distribution function thermal lattice Boltzmann model has been developed for simulation of thermal compressible flows in the low Mach number limit. Both the flow field and energy conservation equation are solved by LB approach. A higher order density distribution function on standard lattices is used to solve the flow field, while an energy distribution function is employed to compute the temperature field. The equation of state of thermal perfect gas is recovered by higher order Hermite polynomial expansions in Navier-Stokes-Fourier equations. The equilibrium distribution functions of D3Q15, D3Q19 and D3Q27 lattices are obtained from the Hermite expansion. They exhibit slight differences originating in differences in the discrete lattice symmetries. The correction terms in LB models for third order derivation are added using an external force in orthogonal polynomials form. Present models are successfully assessed considering several test cases, namely the thermal Couette flow, Rayleigh-Bénard convection, natural convection in square cavity and a spherical explosion in a 3D enclosed box. The numerical results are in good agreement with both analytical solution and results given by previous authors.

  15. Nonstandard Analysis and Shock Wave Jump Conditions in a One-Dimensional Compressible Gas

    SciTech Connect

    Roy S. Baty, F. Farassat, John A. Hargreaves

    2007-05-25

    Nonstandard analysis is a relatively new area of mathematics in which infinitesimal numbers can be defined and manipulated rigorously like real numbers. This report presents a fairly comprehensive tutorial on nonstandard analysis for physicists and engineers with many examples applicable to generalized functions. To demonstrate the power of the subject, the problem of shock wave jump conditions is studied for a one-dimensional compressible gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. To use conservations laws, smooth pre-distributions of the Dirac delta measure are applied whose supports are contained within the shock thickness. Furthermore, smooth pre-distributions of the Heaviside function are applied which vary from zero to one across the shock wave. It is shown that if the equations of motion are expressed in nonconservative form then the relationships between the jump functions for the flow parameters may be found unambiguously. The analysis yields the classical Rankine-Hugoniot jump conditions for an inviscid shock wave. Moreover, non-monotonic entropy jump conditions are obtained for both inviscid and viscous flows. The report shows that products of generalized functions may be defined consistently using nonstandard analysis; however, physically meaningful products of generalized functions must be determined from the physics of the problem and not the mathematical form of the governing equations.

  16. The Formation of Rotational Discontinuities in Compressive Three-dimensional MHD Turbulence

    NASA Astrophysics Data System (ADS)

    Yang, Liping; Zhang, Lei; He, Jiansen; Tu, Chuanyi; Wang, Linghua; Marsch, Eckart; Wang, Xin; Zhang, Shaohua; Feng, Xueshang

    2015-08-01

    Measurements of solar wind turbulence reveal the ubiquity of discontinuities. In this study we investigate how the discontinuities, especially rotational discontinuities (RDs), are formed in MHD turbulence. In a simulation of the decaying compressive three-dimensional (3D) MHD turbulence with an imposed uniform background magnetic field, we detect RDs with sharp field rotations and little variations of magnetic field intensity, as well as mass density. At the same time, in the de Hoffman–Teller frame, the plasma velocity is nearly in agreement with the Alfvén speed, and is field-aligned on both sides of the discontinuity. We take one of the identified RDs to analyze its 3D structure and temporal evolution in detail. By checking the magnetic field and plasma parameters, we find that the identified RD evolves from the steepening of the Alfvén wave with moderate amplitude, and that steepening is caused by the nonuniformity of the Alfvén speed in the ambient turbulence.

  17. Three-dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback. I. Regulation of Star Formation Rates

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Goo; Ostriker, Eve C.; Kim, Woong-Tae

    2013-10-01

    The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation ΣSFR varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of ΣSFR on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and ΣSFR apply. For outer disk regions, this results in ΣSFR ∝ Σ&sqrt;{ρsd}, where Σ is the total gas surface density and ρsd is the midplane density of the stellar disk (plus dark matter). This scaling law arises because ρsd sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with solar-neighborhood and other outer disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.

  18. THREE-DIMENSIONAL HYDRODYNAMIC SIMULATIONS OF MULTIPHASE GALACTIC DISKS WITH STAR FORMATION FEEDBACK. I. REGULATION OF STAR FORMATION RATES

    SciTech Connect

    Kim, Chang-Goo; Ostriker, Eve C.; Kim, Woong-Tae E-mail: eco@astro.princeton.edu

    2013-10-10

    The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation Σ{sub SFR} varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of Σ{sub SFR} on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and Σ{sub SFR} apply. For outer disk regions, this results in Σ{sub SFR}∝Σ√(ρ{sub sd}), where Σ is the total gas surface density and ρ{sub sd} is the midplane density of the stellar disk (plus dark matter). This scaling law arises because ρ{sub sd} sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with solar-neighborhood and other outer disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.

  19. Efficient compression of motion-compensated sub-images with Karhunen-Loeve transform in three-dimensional integral imaging

    NASA Astrophysics Data System (ADS)

    Kang, Ho-Hyun; Shin, Dong-Hak; Kim, Eun-Soo

    2010-03-01

    An approach to highly enhance the compression efficiency of the integral images by applying the Karhunen-Loeve transform (KLT) algorithm to the motion-compensated sub-images is proposed. The sub-images transformed from the elemental images picked-up from the three-dimensional (3D) object might represent the different perspectives of the object. Thus, the similarity among the sub-images gets better than that among the elemental images, so that an improvement of compression efficiency of the sub-images could be obtained. However, motion vectors occurred among the sub-images might result in an additional increase of image data to be compressed. Accordingly, in this paper, motion vectors have been estimated and compensated in all sub-image in advance. Then the KLT algorithm was applied to these motion-compensated sub-images for compression. It is shown from some experimental results that compression efficiency of the proposed method has been improved up to 24.44%, 40.62%, respectively, on the average compared to that of the conventional KLT compression method and that of the JPEG.

  20. X-ray radiographic imaging of hydrodynamic phenomena in radiation driven materials -- shock propagation, material compression and shear flow. Revision 1

    SciTech Connect

    Hammel, B.A.; Kilkenny, J.D.; Munro, D.; Remington, B.A.; Kornblum, H.N.; Perry, T.S.; Phillion, D.W.; Wallace, R.J.

    1994-02-01

    One- and two-dimensional, time resolved x-ray radiographic imaging at high photon energy (5-7 keV) is used to study shock propagation, material motion and compression, and the effects of shear flow in solid density samples which are driven by x-ray ablation with the Nova laser. By backlighting the samples with x-rays and observing the increase in sample areal density due to shock compression, the authors directly measure the trajectory of strong shocks ({approx}40 Mbar) in flight, in solid density plastic samples. Doping a section of the samples with high-Z material (Br) provides radiographic contrast, allowing the measurement of the shock induced particle motion. Instability growth due to shear flow at an interface is investigated by imbedding a metal wire in a cylindrical plastic sample and launching a shock in the axial direction. Time resolved radiographic measurements are made with either a slit-imager coupled to an x-ray streak camera or a pinhole camera coupled to a gated microchannel plate detector, providing {approx} 10-{mu}m spatial and {approx} 100-ps temporal resolution.

  1. X-ray radiographic imaging of hydrodynamic phenomena in radiation-driven materials---Shock propagation, material compression, and shear flow

    SciTech Connect

    Hammel, B.A.; Kilkenny, J.D.; Munro, D.; Remington, B.A.; Kornblum, H.N.; Perry, T.S.; Phillion, D.W.; Wallace, R.J. )

    1994-05-01

    One- and two-dimensional, time-resolved x-ray radiographic imaging at high photon energy (5--7 keV) is used to study shock propagation, material motion and compression, and the effects of shear flow in solid density samples which are driven by x-ray ablation with the Nova laser. By backlighting the samples with x rays and observing the increase in sample areal density due to shock compression, the trajectories of strong shocks ([similar to]40 Mbars) in flight are directly measured in solid density plastic samples. Doping a section of the samples with high-[ital Z] material (Br) provides radiographic contrast, allowing a measurement of the shock-induced particle motion. Instability growth due to shear flow at an interface is investigated by imbedding a metal wire in a cylindrical plastic sample and launching a shock in the axial direction. Time-resolved radiographic measurements are made with either a slit-imager coupled to an x-ray streak camera or a pinhole camera coupled to a gated microchannel plate detector, providing [similar to]10 [mu]m spatial and [similar to]100 ps temporal resolution.

  2. The role of molecular motors in the mechanics of active gels and the effects of inertia, hydrodynamic interaction and compressibility in passive microrheology

    NASA Astrophysics Data System (ADS)

    Uribe, Andres Cordoba

    The mechanical properties of soft biological materials are essential to their physiological function and cannot easily be duplicated by synthetic materials. The study of the mechanical properties of biological materials has lead to the development of new rheological characterization techniques. In the technique called passive microbead rheology, the positional autocorrelation function of a micron-sized bead embedded in a viscoelastic fluid is used to infer the dynamic modulus of the fluid. Single particle microrheology is limited to fluids were the microstructure is much smaller than the size of the probe bead. To overcome this limitation in two-bead microrheology the cross-correlated thermal motion of pairs of tracer particles is used to determine the dynamic modulus. Here we present a time-domain data analysis methodology and generalized Brownian dynamics simulations to examine the effects of inertia, hydrodynamic interaction, compressibility and non-conservative forces in passive microrheology. A type of biological material that has proven specially challenging to characterize are active gels. They are formed by semiflexible polymer filaments driven by motor proteins that convert chemical energy from the hydrolysis of adenosine triphosphate (ATP) to mechanical work and motion. Active gels perform essential functions in living tissue. Here we introduce a single-chain mean-field model to describe the mechanical properties of active gels. We model the semiflexible filaments as bead-spring chains and the molecular motors are accounted for by using a mean-field approach. The level of description of the model includes the end-to-end length and attachment state of the filaments, and the motor-generated forces, as stochastic state variables which evolve according to a proposed differential Chapman-Kolmogorov equation. The model allows accounting for physics that are not available in models that have been postulated on coarser levels of description. Moreover it allows

  3. Radiation hydrodynamics

    SciTech Connect

    Pomraning, G.C.

    1982-12-31

    This course was intended to provide the participant with an introduction to the theory of radiative transfer, and an understanding of the coupling of radiative processes to the equations describing compressible flow. At moderate temperatures (thousands of degrees), the role of the radiation is primarily one of transporting energy by radiative processes. At higher temperatures (millions of degrees), the energy and momentum densities of the radiation field may become comparable to or even dominate the corresponding fluid quantities. In this case, the radiation field significantly affects the dynamics of the fluid, and it is the description of this regime which is generally the charter of radiation hydrodynamics. The course provided a discussion of the relevant physics and a derivation of the corresponding equations, as well as an examination of several simplified models. Practical applications include astrophysics and nuclear weapons effects phenomena.

  4. Compression of ultra-short light pulses using the graded refractive index one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Shiri, R.; Bananej, A.; Safari, E.

    2016-09-01

    The one-dimensional photonic crystals (1D PCs) containing a graded refractive index layer have been theoretically utilized to compress the positively chirped ultra-short pulses of light. Two types of simple and graded index multi-layer structures consisting alternating layers of TiO2 and SiO2 with the same total thicknesses and periodicity have been investigated and compared. For the graded structure, three different refractive index distributions including linear, exponential and parabolic profiles have been considered. The results revealed that replacing one of the homogeneous layers of the unit cells in simple photonic crystal with a graded material having parabolic refractive index profile efficiently improves compression behavior of the structure. The compress factors of as much as 47% and 78% depending on the pulse's initial chirp rate obtained with parabolic profile of such the structures.

  5. One-dimensional magnetohydrodynamics of a cylindrical liner imploded by an azimuthal magnetic field and compressing an axial field

    SciTech Connect

    Hamann, F. Combis, P.; Videau, L.

    2015-08-15

    The one-dimensional magnetohydrodynamics of a plasma cylindrical liner is addressed in the case of a two components magnetic field. The azimuthal component is responsible for the implosion of the liner and the axial field is compressed inside the liner. A complete set of analytical profiles for the magnetic field components, the density, and the local velocity are proposed at the scale of the liner thickness. Numerical simulations are also presented to test the validity of the analytical formulas.

  6. A three-dimensional, compressible, laminar boundary-layer method for general fuselages. Volume 2: User's manual

    NASA Technical Reports Server (NTRS)

    Wie, Yong-Sun

    1990-01-01

    This user's manual contains a complete description of the computer programs developed to calculate three-dimensional, compressible, laminar boundary layers for perfect gas flow on general fuselage shapes. These programs include the 3-D boundary layer program (3DBLC), the body-oriented coordinate program (BCC), and the streamline coordinate program (SCC). Subroutine description, input, output and sample case are discussed. The complete FORTRAN listings of the computer programs are given.

  7. Statistics of active and passive scalars in one-dimensional compressible turbulence.

    PubMed

    Ni, Qionglin; Chen, Shiyi

    2012-12-01

    Statistics of the active temperature and passive concentration advected by the one-dimensional stationary compressible turbulence at Re_{λ}=2.56×10^{6} and M_{t}=1.0 is investigated by using direct numerical simulation with all-scale forcing. It is observed that the signal of velocity, as well as the two scalars, is full of small-scale sawtooth structures. The temperature spectrum corresponds to G(k)∝k^{-5/3}, whereas the concentration spectrum acts as a double power law of H(k)∝k^{-5/3} and H(k)∝k^{-7/3}. The probability distribution functions (PDFs) for the two scalar increments show that both δT and δC are strongly intermittent at small separation distance r and gradually approach the Gaussian distribution as r increases. Simultaneously, the exponent values of the PDF tails for the large negative scalar gradients are q_{θ}=-4.0 and q_{ζ}=-3.0, respectively. A single power-law region of finite width is identified in the structure function (SF) of δT; however, in the SF of δC, there are two regions with the exponents taken as a local minimum and a local maximum. As for the scalings of the two SFs, they are close to the Burgers and Obukhov-Corrsin scalings, respectively. Moreover, the negative filtered flux at large scales and the time-increasing total variance give evidences to the existence of an inverse cascade of the passive concentration, which is induced by the implosive collapse in the Lagrangian trajectories. PMID:23368038

  8. Lattice Boltzmann study of hydrodynamic effects in lamellar ordering process of two-dimensional quenched block copolymers

    NASA Astrophysics Data System (ADS)

    Song, Kai-Xu; Jia, Yu-Xi; Sun, Zhao-Yan; An, Li-Jia

    2008-10-01

    By incorporating self-consistent field theory with lattice Boltzmann method, a model for polymer melts is proposed. Compared with models based on Ginzburg-Landau free energy, our model does not employ phenomenological free energies to describe systems and can consider the chain topological details of polymers. We use this model to study the effects of hydrodynamic interactions on the dynamics of microphase separation for block copolymers. In the early stage of phase separation, an exponential growth predicted by Cahn-Hilliard treatment is found. Simulation results also show that the effect of hydrodynamic interactions can be neglected in the early stage. For the late stage of phase separation, it is easy to see the effects of hydrodynamic interactions on the ordering process of lamellae phase. From the analysis of structure factor curves, we find that the growth of domains is faster if hydrodynamic interactions are introduced. Furthermore, the scaling of the pattern dynamics is investigated for the late stage at zero thermal noise. By studying the behavior of scaling exponents of the structure factor and the nematic order-parameter correlation function Cnn, we can see that the effects of hydrodynamic interactions lead to bigger growth exponent for both functions.

  9. Three dimensional numerical modeling of Hydrodynamics and sediment transport in the Mississippi River Diversion at West Bay

    NASA Astrophysics Data System (ADS)

    Sadid, K. M.; Meselhe, E. A.; Roth, B.; Allison, M. A.

    2013-12-01

    The coastal wetlands of Louisiana have been experiencing high rates of land subsidence and erosion for decades. Anthropogenic alterations to the hydrology and geology, powerful hurricanes, and relative sea level rise have caused major coastal land loss in Louisiana. After years of research and discussions, the use of sediment diversions from the Mississippi River to adjacent embayment areas were proposed and further authorized as a solution for land building. To this end, the West Bay diversion (WBD) was constructed in 2003 to restore approximately 9,831 acres of wetlands in the West Bay area under the Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA). The WBD is located along the right-descending bank of the Mississippi River south of Venice, LA near River Mile (RM) 4.7. The initial size of the channel post-construction was designed to convey 20,000 cubic feet per second (cfs), and over time it was anticipated to support a maximum of 50,000 cfs. This sediment diversion provides an opportunity to examine and analyze the impact of such diversion on the morphology of the river channel, and the retention characteristics and rate of delta growth in the receiving basin. Additionally, the WBD serve as analogue to fully validate morphologic models that could consequently be used to model proposed land building sediment diversions in the Lower Mississippi River. In this study a three-dimensional numerical model is developed for the WBD which includes the main channel of the Mississippi River as well as the receiving basin. The model is being calibrated and validated for hydrodynamics and morphology using detailed field observations. Since 2003 regular monitoring has taken place as per the CWPPRA project guidelines. This includes bathymetric surveys of the receiving basin from 2002 (pre-construction), 2003, 2006, and 2009. A recent monitoring survey has been completed and will be available in the near future. In addition to this monitoring data, the U

  10. Weakly compressible turbulence in local interstellar medium. Three-dimensional modeling using Large Eddy Simulation method

    SciTech Connect

    Chernyshov, Alexander A.; Karelsky, Kirill V.; Petrosyan, Arakel S.

    2010-06-16

    Using advantages of large eddy simulation method, nontrivial regime of compressible magnetohydrodynamic turbulence of space plasma when initially supersonic fluctuations become weakly compressible is studied. Establishment of weakly compressible limit with Kolmogorov-like density fluctuations spectrum is shown in present work. We use our computations results to study dynamics of the turbulent plasma beta and anisotropic properties of the magnetoplasma fluctuations in the local interstellar medium. An outstanding, as yet unexplained, observation is that density fluctuations in the local interstellar medium exhibit a Kolmogorov-like spectrum over an extraordinary range of scales with a spectral index close to -5/3. In spite of the compressibility and the presence of magnetic field in the local interstellar medium, density fluctuations nevertheless admit a Kolmogorov-like power law. Supersonic flows with high value of large-scale Mach numbers are characterized in interstellar medium, nevertheless, there are subsonic fluctuations of weakly compressible components of interstellar medium. These weakly compressible subsonic fluctuations are responsible for emergence of a Kolmogorov-type spectrum in interstellar turbulence which is observed from experimental data. It is shown that density fluctuations are a passive scalar in a velocity field in weakly compressible magnetohydrodynamic turbulence and demonstrate Kolmogorov-like spectrum.