Rotor Design to Attenuate Flow Distortion—Part II: An Unsteady Thin Airfoil Cascade Analysis

The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady thin airfoil cascade theory which can account for the distortion wave length, rotor chord and cascade solidity. The model consists of representing each blade by a moving doublet filament of finite length immersed in a compressible stream containing a velocity distortion. The study is limited to an unloaded, flat plate rotor. This model provides a new physical interpretation for the flow adjustments observed ahead of the rotor and for the generation of sound when an inlet distortion is imposed. The analytical results show the influence of solidity and other rotor design parameters on the distortion transfer. They are found to approach the semi-actuator disk results as the solidity tends to infinity.