It is widely known that losses due to viscous, thermal and molecular relaxation play an important role in sound propagation. Traditionally, acoustics is concerned with the treatment of the fluid as a (linear) continuum using macroscopic quantities such as velocity and pressure as dependent variables. However, the continuum model has its limitations and the model breaks down for Knudsen numbers ...

The lattice Boltzmann (LB) method intrinsically links to the equation with Bhatnagar-Gross-Krook collision operator; however, it has been questioned be able simulate noncontinuum bounded gas flows at micro and nanoscale, where moves a low speed but large Knudsen number. In this article, point verified by simulating Couette moderate numbers (e.g., Kn=10 Kn=100) linearized LB models based on popu...

Abstract In the case of microscopic particles, momentum exchange between particle and gas flow starts to deviate from standard macroscopic case, i.e. no-slip with slip occurring in low moderate Knudsen numbers. order derive new drag force models that are valid also regime for non-spherical particles arbitrary shapes using computational fluid dynamics, conditions at surface have be modified acco...

In this work, slip flow of helium gas has been studied in a three dimensional rectangular microchannel heat sink with 11 microchannel and 10 rectangular fins. Helium gas flow is considered ideal and incompressible. The finite volume method with using coupled algorithm is employed to carry out the computation. To validate the present work, comparison with numerical and experimental studies is do...

The rarefied gas effect on concentration slip and on heterogeneous combustion in microscale chemical reactors was investigated. First, a concentration slip model to describe the rarefied gas effect on the species transport in microscale chemical reactors was derived from the approximate solution of the Boltzmann equation. Second, the model was verified using the direct Monte-Carlo method for th...

We consider the linear temporal stability of a Couette flow of a Maxwell gas within the gap between a rotating inner cylinder and a concentric stationary outer cylinder both maintained at the same temperature. The neutral curve is obtained for arbitrary Mach (Ma) and arbitrarily small Knudsen (Kn) numbers by use of a ‘slip-flow’ continuum model and is verified via comparison to direct simulatio...

A unified framework for particulate two-phase flow is presented with a wide range of solid particle concentration from dilute to dense limit. The simulated by two coupled solvers, that is, the gas-kinetic scheme (GKS) gas phase and wave–particle method (UGKWP) phase. GKS second-order Navier–Stokes solver. UGKWP multiscale all regimes. wave decomposition in depends on cell's Knudsen number (Kn)....

We propose a generalized treatment of the drag force of a spherical particle due to its motion in a laminar fluid media. The theory is equally applicable to analysis of particle diffusion and electric mobility. The focus of the current analysis is on the motion of spherical particles in low-density gases with Knudsen number Kn>>1. The treatment is based on the gas-kinetic theory analysis of dra...

It is widely known that losses due to viscous, thermal and molecular relaxation play an important role in sound propagation. Traditionally, acoustics is concerned with the treatment of the fluid as a (linear) continuum using macroscopic quantities such as velocity and pressure as dependent variables. However, the continuum model has its limitations and the model breaks down for Knudsen numbers ...

This paper presents the results of numerical studies of rotational-translational nonequilibrium, kinetic, and diffusive processes in spherical expanding gas flows. Computations are made using the direct simulation Monte-Carlo (DSMC) method [1, 2] and the solver [3] of the Navier-Stokes equations in terms of classical and quantum concepts [3-7], at the Knudsen numbers Kn* from 0.0015 to 0.03 and...