Extension of the DSMC method to high pressure flows

Титов, Е. В.; Levin, Deborah A.

doi:10.1080/10618560701736221

Cited by 44 publications

(21 citation statements)

References 18 publications

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“…There are different types of continuum breakdown parameter used in the literatures. 7,24,[45][46][47][48][49] Most of the parameters proposed and used in these works are based on the calculation of flow gradients. In a statistical method, calculation of gradients is always subject to noise, which can lead to significant computational errors.…”

Section: Continuum Breakdown Parametermentioning

confidence: 99%

A novel efficient hybrid DSMC–dynamic collision limiter algorithm for multiscale transitional flows

Malaikannan

Kumar

Chinnappan

2017

Numerical Methods in Fluids

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Summary A new 2D parallel multispecies polyatomic particle–based hybrid flow solver is developed by coupling the Direct Simulation Monte Carlo (DSMC) method with a novel Dynamic Collision Limiter (DCL) approach to solve multiscale transitional flows. The hybrid DSMC‐DCL solver can solve nonequilibrium multiscale flows with length scales ranging from continuum to rarefied. The DCL method, developed in this work, dynamically assigns different number of collisions in cells, which is based on the local value of K‐S parameter such that the number of collisions per time step is limited in near‐equilibrium flow regions. Present hybrid solver uses the Kolmogorov‐Smirnov statistical test as the continuum breakdown parameter, based on which, the solution domain is decomposed into near‐equilibrium and nonequilibrium flow regions. Direct Simulation Monte Carlo is used where nonequilibrium flow regions are encountered, while the DCL method is used where flow regions are found to be in near‐equilibrium state. In this work, we have studied hypersonic flow of nitrogen over a blunt body with an aerospike and supersonic flow of argon through a micronozzle. The results obtained by the hybrid DSMC‐DCL solver are compared and shown to agree well with the experimental data and with those obtained from DSMC, with significant savings in the computational cost.

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Section: Continuum Breakdown Parametermentioning

confidence: 99%

A novel efficient hybrid DSMC–dynamic collision limiter algorithm for multiscale transitional flows

Malaikannan

Kumar

Chinnappan

2017

Numerical Methods in Fluids

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“…To reduce them, the initial stages for some regimes (with a dense initial cloud, e.g. Θ > 10 for b = 10) were calculated using the 'equilibrium' modification of the DSMC method [46].…”

Section: Modelmentioning

confidence: 99%

Analytical formula for interpretation of time-of-flight distributions for neutral particles under pulsed laser evaporation in vacuum

Morozov¹

2015

J. Phys. D: Appl. Phys.

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A theoretical study of the time-of-flight (TOF) distributions of neutral species produced by low-fluence pulsed laser evaporation in a vacuum has been performed. A database of TOF distributions has been calculated by the direct simulation Monte Carlo method. The calculated TOF signals have been fitted by a modification of the shifted Maxwell-Boltzmann distribution function with the only parameter being the shift velocity. The dependence of the shift velocity on the number of evaporated monolayers has been described by an analytical expression, derived based on the gas-dynamic analysis of pulsed gas expansion into a vacuum. This expression allows the derivation of a new formula for TOF distributions for neutral particles with the only parameter being the surface temperature. This new formula has been used for the analysis of experimental data on pulsed laser ablation of niobium, copper, graphite and gold. The evaluated surface temperature agrees well with the results of the thermal model calculations and available experimental data with an error of 10% instead of 50-150% for commonly used formulas.

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“…Titov and Levin [6] found, in collision-limited DSMC, that two collisions per time step per particle are sufficient for the computed nonequilibrium distribution to relax to one differing negligibly from the corresponding Maxwell-Boltzmann equilibrium distribution. This distribution is valid for a gas in local thermal equilibrium, and is derived assuming an infinite time has elapsed for relaxation, and that no spatial gradients in density, bulk velocity or temperature exist to disturb the equilibrium.…”

Section: Validity Of the Assumption Of Infinite Collision Ratementioning

confidence: 99%

Validity and Inherent Viscosity of the Quiet Direct Simulation Method

Jermy¹,

Lim²,

Cave³

2011

AIP Conference Proceedings

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The Quiet Direct Simulation (QDS) scheme is a numerical method for modelling gas flows, based on kinetic theory, with some similarities to the Lattice Boltzmann Method (LBM). It differs from LBM notably in that the discrete molecular velocities are not constant but are reset each timestep according to local values of bulk velocity and temperature. For this reason it performs well in highly compressible flows. Two features of the scheme limit its accuracy in low Mach number flows. QDS assumes a Maxwell distribution of molecular velocities. The validity of this assumption may be tested by calculating the gradient Knudsen number and average number of collisions per timestep. The separation of collision and streaming leads to excessive diffusion of momentum, leading to a very high effective viscosity of the modelled gas when the grid spacing is larger than the mean free path. This numerical dissipation is different in character from the dissipation due to the finite order of the spatial reconstruction, common to all finite volume methods, which is also present. The effective viscosity is quantified for simple shear flows and tested in models of a 2D channel flow. A crude model of intermolecular collision during streaming is implemented and shown to reduce the effective viscosity.

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Extension of the DSMC method to high pressure flows

Cited by 44 publications

References 18 publications

A novel efficient hybrid DSMC–dynamic collision limiter algorithm for multiscale transitional flows

A novel efficient hybrid DSMC–dynamic collision limiter algorithm for multiscale transitional flows

Analytical formula for interpretation of time-of-flight distributions for neutral particles under pulsed laser evaporation in vacuum

Validity and Inherent Viscosity of the Quiet Direct Simulation Method

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