NUMERICAL-ANALYSIS OF FLOW THROUGH OSCILLATING CASCADE SECTIONS

Analysis techniques are needed for modeling transonic flows in oscillating cascades with real blade geometries. In the present work, a time-marching, finite difference code has been developed for modeling inviscid flow through oscillating cascades by solving the compressible, unsteady Euler equations. The code uses a deforming grid to capture the motion of the airfoils. Results are presented for both flat plates and mildly loaded biconvex airfoils. Comparisons with small-perturbation theory and experimental data are shown. The flat plate comparisons show good qualitative agreement with the theory. Quantitative agreement seems to be at least partially dependent on resolving the leading-edge singularities. Predictions are presented for cases with biconvex airfoils in both subsonic and transonic flows. For certain cases, the results show better agreement with the experimental data than results from the flat plate small-perturbation theory. This suggests that including the effects of loading can be important for the successful prediction of the unsteady flowfield. However, the quantitative agreement is not always as good and is a function of the interblade phase angle and inflow Mach number. Therefore, predictions from the Euler code should be treated with caution and further research is needed to model the unsteady flow for general cases, particularly for super-resonant flows.