Variance-reduction kinetic simulation for characterization of surface and corner effects in low-speed rarefied gas flows through long micro-ducts

Microfluidic-MEMS (micro-electromechanical system) devices consist of complex subsystems in which the transfer of mass, momentum and energy is critical. This is often achieved by a pressure gradient-driven, low-speed rarefied gas transport in long micro-ducts. Gaseous rarefaction, and geometrical properties of micro-ducts, such as cross-section profile and surface roughness, play a decisive role in the segregation of the flow into inertia-driven and surface-dominated domains. In this work, a parallel stochastic kinetic particle solver that solves the low-variance Boltzmann Bhatnagar-Gross-Krook (BGK) formulation is utilized to study isothermal rarefied gas transport through polar and triangular cross-sections. The effect of geometrical features such as surface proximity to the inertial core and the role of corners, are characterized. A novel parameter to indicate surface influence is introduced, which can be gainfully used in MEMS design and optimization.