Viscous flow, effusion, and thermal transpiration are the main gas transport modalities for a rarefied gas in a macro-porous medium. They have been well quantified only in the case of simple geometries. This paper develops a model based on the homogenization of kinetic equations producing effective transport properties (permeability, Knudsen diffusivity, thermal transpiration ratio) in any poro...

Abstract. Solar cells have been made from hydrogenated amorphous silicon (a-Si:H) films. The films including Si nanoparticles by 3% in the volume fraction have been found to possess good properties. In order to find the method to control this volume fraction, the motion of Si nanoparticles in the rarefied flow of H2 and SiH4 is examined for a CVD (chemical vapor deposition) reactor by use of th...

For increasingly rarefied flowfields, the predictions from continuum formulation, such as the Navier–Stokes equations lose accuracy. These inaccuracies are attributed primarily to the linear approximations of the stress and heat flux terms in the Navier– Stokes equations. The inclusion of higher order terms, such as Burnett, or high-order moment equations, could improve the predictive capabilit...

1 The BGK model 3 1.1 Basic Model Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Hydrodynamic limit of the BGKW Model . . . . . . . . . . . . . . . . . . 5 1.3 BGKW Model Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3.1 Normal shock profiles in a hard sphere gas . . . . . . . . . . . . . . 7 1.3.2 1-D heat flow in a rarefied hard sphere gas . ...

This paper summarizes the current efforts at VKI and collaborating institutions in understanding nonequilibrium phenomena in hypersonic flows. Research activities related to “Detailed gas chemistry models,” “Kinetic theory,” and “Rarefied gas effects” are described. Keywords— Atmospheric entry flows, Thermo-chemical nonequilibrium flows, Computational Fluid Dynamics.

Gas mixing in a T-shape micro mixer has been simulated using the Direct Simulation Monte Carlo (DSMC) method. It is considered that the adequate mixing occurs when the mass composition of the species, CO or N2, deviates below 1 % from their equilibrium composition. The mixing coefficient is defined as the ratio of the mixing length to the main channel’s height. As the inlet Kn increases, while ...