The Coupled CFD/Free-Wake Method for Numerical Prediction of Rotor BVI Noise

A coupled Navier-Stokes/free-wake method is developed to predict the rotor aerodynamics and wake. The widely-used Farassat 1A formulation is adopted to predict the rotor noise. In the coupled method, the Reynolds-averaged Navier-Stokes (RANS) solver is established to simulate complex aerodynamic phenomena around blade and the tip-wake is captured by a free-wake model without numerical dissipation in the off-body wake zone. To overcome the time-consuming of the coupling strategy in previous studies, a more efficient coupling strategy is presented, by which only the induced velocity on the outer boundary grid need to be calculated. In order to obtain blade control settings, a delta trimming procedure is developed, which is more efficient than traditional trim method in the calculation of Jacobian matrix. Several flight conditions are simulated to demonstrate the validity of the coupled method. Then the rotor noise of operational load survey (OLS) is studied by the developed method as an application and the computational results are shown to be in good agreements with the available experimental data.