A hybrid molecular and continuum method for low-Reynolds-number flows Original Research Article

A novel hybrid method is proposed and developed combining the continuum boundary singularity method (BSM) and the molecular direct simulation Monte Carlo method (DSMC) for low-Reynolds-number flows in the transition regime. The flow about a single cylinder is used to test the proposed hybrid method. The DSMC is applied to an annular region enclosing the cylinder and the BSM is employed to solve the entire flow domain. The parameters used in the DSMC and in the coupling procedure, such as the number of simulated particles, the cell size and the size of the coupling zone, are determined by inspecting the convergence rate and accuracy of obtained solution. It is observed that in the partial-slip flow regime the results from the hybrid method match the ones from the BSM combined with the heuristic partial-slip boundary conditions. For higher Knudsen numbers, the differences in velocity and pressure drop between the hybrid and continuum BSM are significant that justify the use of hybrid method.