Evaluation Of Shaft Angle Effects On Dynamic Stall Based On Low- And High-Fidelity Aero-Elastic Rotor Simulations

Abstract

This paper investigates the effect of tilting a rotor backward on dynamic stall at a moderate advance ratio using low-fidelity (free wake) and high-fidelity (Computational Fluid Dynamics) approaches. The first objective pursued is to evaluate the capability of the low-fidelity approach to provide accurate results for such flight conditions. A second objective is to precisely identify the evolution of the mechanisms leading to dynamic stall under high-load conditions. The low-fidelity approach is found to predict the main features of the blade-vortex interaction leading to dynamic stall on the retreating blade, with a lower intensity compared to high-fidelity results (especially when the rotor is tilted backward). It however misses a second dynamic stall event occurring on the rear blade that is mainly due to an interaction with root and stall vortices. This leads to slightly different values and trends of thrust coefficients with respect to the collective pitch angle near stall compared to high-fidelity results.