ANALYSIS OF HIGH REYNOLDS-NUMBER INVISCID VISCID INTERACTIONS IN CASCADES

An efficient analysis for predicting steady, strong, inviscid/viscid interaction phenomena, such as viscous-layer separation, shock/boundary-layer interaction, and trailing-edge/near-wake interaction, in turbomachinery blade passages is needed as part of a comprehensive analytical blade design prediction system. Such an analysis is described in the present paper. It uses an inviscid/viscid interaction approach, in which the flow in the outer inviscid region is assumed to be potential and the flow in the inner or viscous-layer region is governed by Prandtl's equations. The inviscid solution is determined using an implicit, least-squares, finite difference approximation; the viscous-layer solution is determined using an inverse, finite difference, space-marching method, which is applied along the blade surfaces and wake streamlines. The inviscid and viscid solutions are coupled using a semi-inverse global iteration procedure, which permits the prediction of boundary-layer separation and other strong-interaction phenomena. Results are presented for two cascades, with a range of inlet flow conditions considered for one of them, including conditions leading to large-scale flow separations. Comparisons with Navier-Stokes solutions are also given.