Study of a Rarefied Gas Driven by the Lid of a Micro cavity with a Diamond-Shaped Obstacle Using SRT-LBM

The present study numerically investigates the flow and temperature behavior of a rarefied gas confined in a two-dimensional square lid-driven micro-cavity, with particular emphasis on the influence of a centrally located diamond-shaped obstacle. The upper wall moves at a constant velocity, while the bottom wall and the obstacle are heated, and the remaining walls are maintained at a lower temperature. Simulations are carried out using the lattice Boltzmann method, employing diffuse scattering boundary conditions at the moving lid and combined bounce-back-specular reflection scheme at the stationary walls and obstacle surfaces. Two configurations are examined: a cavity without an obstacle and a cavity containing a heated diamond-shaped obstacle. Rarefaction effects are analyzed over a range of Knudsen numbers, with a tangential momentum accommodation coefficient of σ= 0.7 .The results show that increasing rarefaction enhances velocity slip, reduces velocity amplitudes, and weakens vortical structures. While the obstacle strongly perturbs the flow at low Knudsen numbers, its influence progressively diminishes as rarefaction increases, leading to smoother velocity fields and reduced flow disturbances.