A LINEARIZED UNSTEADY AERODYNAMIC ANALYSIS FOR REAL BLADE SUPERSONIC CASCADES

The prediction capabilities of a linearized unsteady potential analysi s have been extended to include supersonic cascades with subsonic axia l flow. The numerical analysis of this type of flow presents several d ifficulties. First, complex oblique shock patterns exist within the ca scade passage. Second, the acoustic response is discontinuous and prop agates upstream and downstream of the blade row. Finally, a numerical scheme based on the domain of dependence is required for numerical sta bility. These difficulties are addressed by developing a discontinuity capturing scheme and matching the numerical near-field solution to an analytical far-field solution. Comparisons with semi-analytic results for flat plate cascades show that reasonable predictions of the unste ady aerodynamic response at the airfoil surfaces are possible, but aer oacoustic response calculations are difficult. Comparisons between fla t plate and real blade cascade results show that one effect of real bl ades is the impulsive loads due to motion of finite strength shocks.