A5046136867- Gas Dynamics and Kinetic Theory
- Fluid Dynamics and Turbulent Flows
- Fluid Dynamics and Mixing
- Particle Dynamics in Fluid Flows
- Cyclone Separators and Fluid Dynamics
- Granular flow and fluidized beds
- Electrical and Bioimpedance Tomography
- Heat Transfer and Optimization
- Fluid Dynamics and Vibration Analysis
- Fluid Dynamics and Heat Transfer
- Laser Design and Applications
- Computational Fluid Dynamics and Aerodynamics
- Heat Transfer and Boiling Studies
- Phase Equilibria and Thermodynamics
- Advanced MEMS and NEMS Technologies
- Combustion and flame dynamics
- Quantum, superfluid, helium dynamics
- Flow Measurement and Analysis
- Lattice Boltzmann Simulation Studies
- Spacecraft and Cryogenic Technologies
- Catalytic Processes in Materials Science
- Aerosol Filtration and Electrostatic Precipitation
- Metallurgical Processes and Thermodynamics
- High-pressure geophysics and materials
- Vibration and Dynamic Analysis
Sandia National Laboratories
2015-2024
Sandia National Laboratories California
2004-2021
IP Australia
2008
National Technical Information Service
2005
Office of Scientific and Technical Information
2000-2005
Radiology Associates of Albuquerque
2000-2003
University of Michigan
1997-2000
United States Department of Commerce
2000
Oak Ridge National Laboratory
1996-1997
California Institute of Technology
1984-1985
The lattice-Boltzmann (LB) method is applied to complex, moving geometries in which computational cells are partially filled with fluid. LB algorithm modified include a term that depends on the percentage of cell saturated useful for modeling suspended obstacles do not conform grid. Another application simulations flow through reconstructed media easily segmented into solid and liquid regions. A detailed comparison made FIDAP simulation results about periodic line cylinders channel at...
The gold-standard definition of the Direct Simulation Monte Carlo (DSMC) method is given in 1994 book by Bird [Molecular Gas Dynamics and Flows (Clarendon Press, Oxford, UK, 1994)], which refined his pioneering earlier papers he first formulated method. In intervening 25 years, DSMC has become choice for modeling rarefied gas dynamics a variety scenarios. chief barrier to applying more dense or even continuum flows its computational expense compared fluid methods. dramatic (nearly...
A ‘‘reference cell’’ for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform comparing plasma measurements carried out common reactor geometry by different groups, thereby enhancing the transfer knowledge and insight gained rf discharge studies. results performing ostensibly identical on six these cells five laboratories are analyzed discussed. Measurements were made voltage current...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Michael A. Gallis, John R. Torczynski, Steven J. Plimpton, Daniel Rader, Timothy Koehler; Direct simulation Monte Carlo: The quest for speed. AIP Conf. Proc. 9 December 2014; 1628 (1): 27–36. https://doi.org/10.1063/1.4902571 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley...
We provide the first demonstration that molecular-level methods based on gas kinetic theory and molecular chaos can simulate turbulence its decay. The direct simulation Monte Carlo (DSMC) method, a technique for simulating flows resolves phenomena from to hydrodynamic (continuum) length scales, is applied Taylor-Green vortex flow. DSMC simulations reproduce Kolmogorov -5/3 law agree well with turbulent energy dissipation rate obtained numerical of Navier-Stokes equations using spectral...
Abstract A detailed case study is made of one particular solution the 2D incompressible Navier–Stokes equations. Careful mesh refinement studies were using four different methods (and computer codes): (1) a high‐order finite‐element method solving unsteady equations by time‐marching; (2) both steady and associated linear‐stability problem; (3) second‐order finite difference in streamfunction form (4) spectral‐element time‐marching. The unanimous conclusion that correct for flow over...
An experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations. Results are obtained primarily through measurement the pressure dependence conductive heat flux between parallel plates separated by gas-filled gap. Measured heat-flux data used in formula based on Direct Simulation Monte Carlo (DSMC) simulations coefficients. The assembly also features complementary capability measuring variation gas density using...
The accuracy of a recently proposed direct simulation Monte Carlo (DSMC) algorithm, termed “sophisticated DSMC,” is investigated by comparing results to analytical solutions the Boltzmann equation for one-dimensional Fourier–Couette flow. An argon-like hard-sphere gas at 273.15 K and 266.644 Pa confined between two parallel, fully accommodating walls 1 mm apart that have unequal temperatures tangential velocities. simulations are performed using implementation. In harmony with previous work,...
The Rayleigh-Taylor instability (RTI) is investigated using the direct simulation Monte Carlo method of molecular gas dynamics. Fully resolved two-dimensional simulations are performed to quantify growth flat and single-mode perturbed interfaces between two atmospheric-pressure monatomic gases as a function Atwood number gravitational acceleration. Future on more extreme computational platforms will enable investigation RTI in greater detail.
In turbulent flows, kinetic energy is transferred from the largest scales to progressively smaller scales, until it ultimately converted into heat. The Navier-Stokes equations are almost universally used study this process. Here, by comparing with molecular-gas-dynamics simulations, we show that do not describe gas flows in dissipation range because they neglect thermal fluctuations. We investigate decaying turbulence produced Taylor-Green vortex and find spectra grow quadratically wave...
The ellipsoidal-statistical Bhatnagar–Gross–Krook (ES-BGK) kinetic model is investigated for steady gas-phase transport of heat, tangential momentum, and mass between parallel walls (i.e., Fourier, Couette, Fickian flows). This investigation extends the original study Cercignani Tironi, who first applied ES-BGK to heat Fourier flow) shortly after this was proposed by Holway. implemented in a molecular-gas-dynamics code so that results from can be compared directly full Boltzmann collision...
The Richtmyer-Meshkov instability (RMI) is investigated using the Direct Simulation Monte Carlo (DSMC) method of molecular gas dynamics. Due to inherent statistical noise and significant computational requirements, DSMC hardly ever applied hydrodynamic flows. Here, RMI simulations are performed quantify shock-driven growth a single-mode perturbation on interface between two atmospheric-pressure monatomic gases prior re-shocking as function Atwood Mach numbers. results qualitatively reproduce...
An approach is presented for computing the force on and heat transfer to a spherical particle from rarefied flow of monatomic gas that computed using direct simulation Monte Carlo (DSMC) method. The concentration taken be dilute, around (but not necessarily throughout domain) free-molecular. Green’s functions are determined analytically, verified by demonstrating they yield certain well-known results, implemented numerically within DSMC code. Simulations performed case confined between two...
The convergence behavior of the direct simulation Monte Carlo (DSMC) method is systematically investigated for near-continuum, one-dimensional Fourier flow. An argon-like, hard-sphere gas confined between two parallel, fully accommodating, motionless walls unequal temperature. simulations are performed using four variations based on Bird’s DSMC algorithm that differ in ordering move, collide, and sample operations. primary metric studied ratio DSMC-calculated bulk thermal conductivity to...
Recently proposed molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory fundamental molecular properties (i.e., no macroscopic reaction-rate information) are investigated for chemical reactions occurring in upper-atmosphere hypersonic flows. The new good agreement with the measured Arrhenius near-equilibrium conditions both other theoretical far-from-equilibrium conditions. Additionally, applied to representative combustion...
An improved gas-damping model for the out-of-plane motion of a near-substrate microbeam is developed based on Reynolds equation (RE). A boundary condition RE that relates pressure at beam edge to motion. The coefficients in this are determined from Navier-Stokes slip-jump (NSSJ) simulations small slip lengths (relative gap height) and direct simulation Monte Carlo (DSMC) molecular gas dynamics larger lengths. This significantly improves accuracy when width only slightly greater than height...
The state of a single-species monatomic gas from near-equilibrium to highly nonequilibrium conditions is investigated using analytical and numerical methods. Normal solutions the Boltzmann equation for Fourier flow (uniform heat flux) Couette shear stress) are found in terms heat-flux shear-stress Knudsen numbers. Analytical inverse-power-law molecules hard-sphere through Maxwell at small numbers Chapman-Enskog (CE) theory finite moment-hierarchy (MH) method. Corresponding obtained Direct...
Bird's direct simulation Monte Carlo method is used to compute the molecular velocity distribution of a gas with heat flow. At continuum nonequilibrium conditions (small flux), Chapman-Enskog behavior obtained for inverse-power-law molecules (hard-sphere through Maxwell): Sonine-polynomial coefficients away from walls (i.e., normal solution) agree theory. noncontinuum (large these differ systematically their values as local Knudsen number (nondimensional flux) increased.
Abstract The effect of the collision‐partner selection scheme on accuracy and efficiency Direct Simulation Monte Carlo method is investigated. Several schemes that reduce mean collision separation, including fixed sub‐cell scheme, transient adaptive virtual are evaluated. Additionally, a new proposed limits population from which partners selected based distance traveled by simulator performs near‐neighbor collisions using this population. These assessed for Fourier flow (heat conduction...
For high-Mach-number turbulent flows, the Kolmogorov length scale can be comparable to gas-molecule mean-free path, which could introduce noncontinuum molecular-level effects into energy cascade. To investigate this issue, compressible Taylor-Green vortex flow is simulated using both molecular gas dynamics and continuum computational fluid dynamics. Although energy-decay rates are same, fluctuations break symmetries thereby produce different but statistically similar routes from initial...
Measurement and modeling of gas flows in microelectromechanical systems (MEMS) scale channels are relevant to the fundamentals rarefied dynamics (RGD) practical design MEMS-based flow micropumps. We describe techniques for building robust, leak-free, rectangular microchannels which micro- nanofluidic devices, while themselves useful fundamental RGD studies. For first time, we report isothermal steady helium (He) through these from continuum free-molecular regime unprecedented Knudsen range...
Kolmogorov's theory of turbulence assumes that the small-scale turbulent structures in energy cascade are universal and determined by dissipation rate kinematic viscosity alone. However, thermal fluctuations, absent from continuum description, terminate near Kolmogorov length scale. Here, we propose a simple superposition model to account for effects fluctuations on statistics. For compressible Taylor–Green vortex flow, demonstrate conjunction with data direct numerical simulation...