Implicit boundary conditions for direct simulation Monte Carlo method in MEMS flow predictions

A simple implicit treatment for the low speed inflow and outflow boundary c onditions for the direct simulation Monte Carlo (DSMC) of the flows in micr oelectromechanical systems (MEMS) is proposed. The local mean flow velocity , temperature, and number density near the subsonic boundaries were used to determine the number of molecules entering the computational domain and th eir corresponding velocities at every sample average step. The proposed bou ndary conditions were validated against micro-Poiseuille flows and micro-Co uette flows. The results were compared with analytical solutions derived fr om the Navier-Stokes equations using first-order and second order slip-boun dary conditions. The results show that the implicit treatment of the subson ic flow boundaries is robust and appropriate for use in the DSMC of the flo ws in MEMS.