The Effects of Acoustically Lined Walls on Cascade Flutter

Abstract

The effect of acoustically lined walls on cascade flutter is investigated theoretically using a semi-actuator disk model, which permits the considerations for flow turning and total-pressure-loss due to cascades. The three-dimensional flow fields, upstream, inside and downstream of the cascade are solved separately, and then joined properly at the leading edge plane and the trailing edge plane. The acoustic characteristics of walls in each region are specified by the uniform acoustic admittance. It is shown that an acoustically lined wall can stabilize as well as destabilize blade oscillation, depending on its acoustic admittance. The value of wall admittance which is effective for suppressing blade oscillation differs from the one effective for noise reduction. It is therefore suggested that the acoustic lining used for jet engines may work under an off-design condition for stabilizing blade oscillation.