抄録
For the numerical analysis of the time-dependent incompressible Navier-Stokes equations, several kinds of fractional step methods have been presented successfully However, there are still some problems about the boundary conditions of pressure Poisson equation. In general time-dependent problem with the open boundary it is difficult to prescribe the velocity itself on the outlet boundary, therefore in the conventional analysis those boundary conditions which are for example normal stress equal to zero, normal gradient of pressure equal to zero or pressure equal to zero have been adopted. In the present paper, a new approach for the open boundary condition of pressure Poisson equation has been proposed in which the pressure boundary values can be update for each time step by solving the boundary pressure Poisson equation which consists of the elements adjacent to the open boundary. The present approximation method is effective for the flow-through problems or the out-flow problems, like as wind engineering in architecture. In order to demonstrate the validity, the numerical results about back step flow and vortex shedding problem have been shown with R_e≦10^4.
