COMPUTATION OF STEADY AND UNSTEADY VISCOUS FLOWS USING A SIMULTANEOUSLY COUPLED INVISCID-VISCOUS INTERACTION TECHNIQUE

An interacting viscous-inviscid method for efficiently computing stead y and unsteady low Mach number viscous flows with separation is presen ted. The inviscid region is modeled using a finite element discretizat ion of the full potential equation. The viscous region is modeled usin g a finite difference boundary layer technique. The two regions are-si multaneously coupled through the requirement that the edge velocities of the two regions be equal, and through an injection velocity arising from the displacement thickness. For unsteady flows, the fluid how is assumed to be composed of two parts: a mean or steady flow plus a har monically varying small unsteady disturbance. This assumption results in a nonlinear description for the mean flow, and a linear description for the small disturbance unsteady flow. For the solution of the mean how the nonlinear governing equations are reduced to a series of line ar matrix equations using Newton iteration. The resulting mean how sol ution is then used to form the variable coefficients of the linearized unsteady equations, which are solved directly. The present method is able to compute flows with separation, and in the case of unsteady flo ws, flows with moving separation and reattachment points. (C) 1995 Aca demic Press Limited