Minimal Modeling for Noise and Vibration Propensity of Low-Speed Axial Flow Rotor Blades Due to Vortex Shedding

Abstract

Abstract. The subject of the paper is the phenomenon of shedding of vortices (termed herein as profile vortex shedding) from the region being upstream of the trailing edge (TE) of sections of blade profiles. The shed vortices correspond to noise generation at the trailing edge, and lift force fluctuations which cause temporarily fluctuating bending moments on the blade. The simplified models presented herein aim at capturing the main qualitative trends and giving order-of-magnitude quantitative estimates on vortex shedding noise and vibration. A synthesis is given on the results of investigations on a classic RAF-6E profile and on a circular-arc cambered plate profile of 8% relative camber, both considered as being representatives for low-speed axial flow rotors. The flow field related to the various numerical simulation scenarios has been surveyed in detail, for comprehension of underlying physics. The results of minimal models have been processed in a merged way for the two blade profiles, they have been generalized and compared to literature data for validation purposes. The vortex noise model is found to resolve the qualitative trends and can be further developed for brief quantitative predictions. The lift force fluctuation model captures the order of magnitude of computational results effectively.