Thermal microscale gas flow simulation using wall function and bounce-back scheme: Modified lattice Boltzmann method

Rarefied gas flow with heat transfer was simulated utilizing a modified lattice Boltzmann method with two relaxation times (TRT) for the gas flow and single relaxation time (SRT) for heat transfer in the microchannel. The analytical function for capturing the effect of the Knudsen layer on the slip velocity was used. Anti-symmetric relaxation time was obtained (ASRT) by applying the boundary condition at the wall surfaces (bounce-back distribution functions) to improve the accuracy of slip velocity. The fluid temperature jump at the wall is considered by utilizing a second-order implicit scheme for capturing the temperature boundary condition at the wall. The Zou-He boundary conditions were also used for the flow at both the inlet and outlet of the microchannel. The bounce-back distribution functions were applied at the walls. In addition, a non-equilibrium temperature boundary condition is implemented at the geometry inlet. At the microchannel outlet, the zero-gradient temperature condition was also imposed. The simulation results were compared with those obtained from the linear Boltzmann method and direct simulation Monte Carlo (DSMC), and good agreement was found.