Subsonic flow past an oscillating cascade with finite mean flow deflection

Abstract

A theoretical model for predicting the aerodynamic response due to a finite-deflection cascade oscillating in a subsonic stream is described. Based on the assumption of small amplitude harmonic blade motions, the unsteady flow is treated as a small fluctuation about the nonuniform mean flow. The mean or steady flow is determined as a solution of the full potential equation while the unsteady flow is governed by a linear equation with variable coefficients which depend on the steady flow field. Numerical solutions based on this general aerodynamic model have been obtained for simple cascade configurations. Selected results for sharp-edged blade profiles are described. Those for flat plate cascades are shown to be in good agreement with previous analytical predictions for both subresonant and superresonant blade motions. Predictions for double circular arc and thin circular arc profiles reveal that blade thickness has a significant effect on the unsteady response while the effect of flow turning due to blade camber is only minimal.