Numerical Assessment of the Noise Signature Sidewall Contamination of a Linear Cascade With Moving Bars

Abstract

The effect of the finite extent of a linear cascade on the acoustic and vortical modes generated at the cascade exit by a set of moving bars located at the inlet is assessed by means of a numerical study. The sidewall interference is studied for an airfoil, which is representative of the midsection of a low pressure turbine airfoil. The deviations from the purely periodic steady state have been also investigated. It is concluded that both the unsteady pressure distributions on the airfoil and the mode-decomposition at the cascade exit show a reasonable matching with the purely periodic case, provided that the nominal interblade phase angle is taken into account to postprocess the numerical data. This conclusion is a key element to the investigation of the scattering and propagation of pure tones in turbomachinery in high speed linear cascades.