outflow Boundary conditions for Direct Numerical simulation of Compressible Flows

摘要

Outflow boundary conditions for direct numerical simulation of compressible flow are proposed. In the newly developed boundary conditions, flow field near the outflow boundary is decomposed into compressible and incompressible parts by Helmholtz decomposition. Navier-Stokes Characteristic Boundary Conditions (NSCBC) are used for compressible part. Convective-viscous boundary conditions with transport equation for pressure (CVBCTP) which produce very accurate results in incompressible flows are applied for incompressible part. Both boundary conditions are superposed to define final one. The new boundary conditions are applied to three test cases which are acoustic wave propagation, a single vortex passing through boundary and a single vortex with acoustic wave propagation. The results show that the present boundary conditions provide a significant improve- ment over the conventional boundary conditions.