ANALYSIS OF HIGH REYNOLDS-NUMBER INVISCID VISCID INTERACTIONS IN CASCADES

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