Search

A rarefied gas flow through channels (i.e. flow through parallel plates) of finite length has been modeled based on the direct simulation Monte Carlo method. The reduced flow rate and the flow field have been calculated as function of the gas rarefaction, the length-to-height ratio and the pressure ratio upstream and downstream of the channel. The whole range of the gas rarefaction including the free-molecular, transitional and hydrodynamic regimes and a wide range of the length-to-height ratio representing both short and long channels have been considered. Several values of the pressure ratio between 0 and 0.5 have been used in the calculations. It is shown that the rarefaction parameter has the most significant effect on the flow field characteristics and patterns, followed by the pressure ratio, while the length-to-height ratio has a rather modest impact. The Mach belt phenomenon is discussed in detail.

Flow of a rarefied gas through a channel of rectangular cross section is investigated numerically and experimentally. Emphasis is given on the study of the molecular scattering law influence at the wall boundary surfaces. The Cercignani-Lampis boundary conditions are considered in detail for the current problem, along with the linearized BGK kinetic model and the discrete velocity method. Numerical conductance values are tabulated for certain aspect ratios and accommodation coefficients in the whole range of the Knudsen number and compared with corresponding experimental results for certain gas-surface combinations. Compared to the classical Maxwell diffuse boundary conditions, the Cercignani-Lampis gas-surface interaction allows a better agreement with the measurements.