COMPUTATION AND SIMULATION OF WAKE-GENERATED UNSTEADY PRESSURE AND BOUNDARY-LAYERS IN CASCADES .1. DESCRIPTION OF THE APPROACH AND VALIDATION

The unsteady pressure and boundary layers on a turbomachinery blade ro w arising from periodic wakes due to upstream blade rows are investiga ted in this paper. A time-accurate Euler solver has been developed usi ng an explicit four-stage Runge-Kutta scheme. Two-dimensional unsteady nonreflecting boundary conditions are used at the inlet and the outle t of the computational domain. The unsteady Euler solver captures the wake propagation and the resulting unsteady pressure field which is th en used as the input for a two-dimensional unsteady boundary layer pro cedure to predict the unsteady response of blade boundary layers. The boundary layer code includes an advanced k-epsilon model developed for unsteady turbulent boundary layers. The present computational procedu re has been validated against analytic solutions and experimental meas urements. The validation cases include unsteady inviscid flows in a fl at-plate cascade and a compressor exit guide vane (EGV) cascade, unste ady turbulent boundary layer on a flat plate subject to a traveling wa ve, unsteady transitional boundary layer due to wake passing, and unst eady flow at the midspan section of an axial compressor stator. The pr esent numerical procedure is both efficient and accurate in predicting the unsteady flow physics resulting from wake/blade-row interaction, including wake-induced unsteady transition of blade boundary layers.