Comparison of several open boundary numerical treatments for laminar recirculating flows

Several open boundary conditions (OBCs) are compared and evaluated in the framework of the SIMPLE algorithm using staggered and non‐staggered grid systems. The benchmark laminar flow test cases used for the OBC evaluation are Poiseuille‐Benard flow in a channel and stratified backward‐facing step flow. The investigated OBCs are linear explicit step space extrapolation, Orlanski's monochromatic wave, and pressure extrapolation. Orlanski's and pressure extrapolation open boundary treatment for unsteady and steady flows, respectively, yield little reflection and has proved to be adequate for engineering calculations.