Numerical modelling of microchannel gas flows in the transition flow regime using the cascaded lattice Boltzmann method

TL;DR

This paper presents a numerical study of microchannel gas flows in the transition regime using a cascaded lattice Boltzmann method with a Bosanquet-type effective viscosity and specialized boundary conditions, analyzing flow characteristics across various Knudsen numbers.

Contribution

The paper introduces a modified CLB method with a combined boundary scheme and effective viscosity to accurately simulate rarefied gas flows in microchannels.

Findings

Velocity profiles are affected by rarefaction effects.

Mass flow rate varies with Knudsen number.

Non-linear pressure deviations are observed in long microchannels.

Abstract

In the CLB method, a Bosanquet-type effective viscosity is employed to account for the rarefaction effect on the gas viscosity. To gain accurate simulations and to match the Bosanquet-type effective viscosity, the combined bounce-back/specular-reflection boundary scheme with a modified second-order slip boundary condition is adopted in the CLB method. The present method is applied to study gas flow in a microchannel with periodic boundary condition and gas flow in a long microchannel (the ratio of the length to the height L/H=100) with pressure boundary condition over a wide range of Knudsen numbers. The influence of the rarefaction effect on the velocity profile, the mass flow rate, and the non-linear pressure deviation distribution along the long microchannel are investigated.