Stefan Stefanov

Monte Carlo simulation of the Taylor–Couette flow of a rarefied gas

We report and discuss the results of a direct Monte Carlo simulation of the flow of a rarefied gas flowing between two cylinders when the inner one rotates. The formation of Taylor vortices is clearly exhibited.

Rayleigh–Bénard flow of a rarefied gas and its attractors. I. Convection regime

In this paper we investigate the long time behavior (final state) of the Rayleigh–Benard (RB) flow of a rarefied monatomic gas for a set of the nondimensional Knudsen and Froude numbers in the intervals Kn∈[1.0×10−3,4×10−2], Fr∈[1.0×10−1,1.5×103]. For the most part of the computations the third nondimensional parameter, the ratio of the cold and hot wall temperatures is fixed to Tc/Th=0.1, corresponding to a large temperature difference (Th serves as reference temperature), for which the RB system is believed to reach most of the possible final states (attractors). The low Knudsen numbers allow the problem to be investigated numerically by using two completely different methods: direct simulation Monte Carlo (DSMC) method (molecular approach) and finite difference (FD) method (continuum approach based on the model of compressible viscous heat conducting gas with state-dependent transport coefficients). As a result the effect of rarefaction on the onset of convection in the two-dimensional case is studied ...

On DSMC Calculations of Rarefied Gas Flows with Small Number of Particles in Cells

The direct simulation Monte Carlo (DSMC) analysis of two- and three-dimensional rarefied gas flows requires computational resources of very large proportions. One of the major causes for this is that, along with the multidimensional computational mesh, the standard DSMC approach also requires a large number of particles in each cell of the mesh in order to obtain sufficiently accurate results. This paper presents the development and validation of a modified simulation procedure which allows more accurate calculations with a smaller mean number of particles (

Monte Carlo simulation and Navier–Stokes finite difference calculation of unsteady-state rarefied gas flows

\langle N\rangle\sim1

Nonplanar oscillatory shear flow: From the continuum to the free-molecular regime

) in the grid cells. In the new algorithm, the standard DSMC collision scheme is replaced by a two-step collision procedure based on “Bernoulli trials” scheme (or its simplified version proposed by the author), which is applied twice to the cells (or subcells) of a dual grid within a time step. The modified algorithm uses a symmetric Strang splitting scheme that improves the accuracy of the splitting scheme to

Pressure based finite volume method for calculation of compressible viscous gas flows

O(\tau^2)

Rarefied gas flow in a rectangular enclosure induced by non-isothermal walls

with respect to the time step

DSMC Simulation of Low Knudsen Micro/Nanoflows Using Small Number of Particles per Cells

\tau

Rayleigh–Bénard flow of a rarefied gas and its attractors. II. Chaotic and periodic convective regimes

, making the modified DSMC method an effective numerical tool for both steady and unsteady gas flow calculations on fine multidimensional grids. The latter is particularly important for simulation of vortical and unstable rarefied gas flows. The modified simulation scheme might also be useful for DSMC calculations within the subcell areas of a multilevel computational grid.

Monte Carlo analysis of macroscopic fluctuations in a rarefied hypersonic flow around a cylinder

A comparative analysis of two approaches (molecular and continuum) for three one-dimensional unsteady-state rarefied gas flows with small Knudsen number is presented. Numerical results have been obtained by using Direct Simulation Monte Carlo (DSMC) method for the molecular and a finite difference method for the continuum approaches, respectively.