Prediction and Validation of the Aerodynamics, Structural Dynamics, and Acoustics of the SMART Rotor Using a Loosely-Coupled CFD-CSD Analysis

The capability of active trailing-edge flaps (TEFs) for inplane, low-frequency noise reduction is analyzed using a loosely-coupled CFD-CSD simulation methodology. The calculations were performed for a high speed flight condition using prescribed 5=rev and 3=rev harmonic actuation of the TEFs. Structural bending moments and rotor performance parameters from the CFD-CSD simulations were predicted ahead of time, and subsequently validated against the measurements available from the 2008 DARPA/Boeing/NASA/Army wind tunnel tests. The results show good correlation with measured values providing confidence in the solution methodology. A phasesweep study of the sinusoidal 1:5°=3p TEF inputs indicates that the maximum noise reduction (up to 4.65 dB) can be obtained around the phase angle of 240°. Comparisons with the experiments show that the optimum phase is consistent with the measurements, and the overall sound pressure level reductions are comparable to those predicted by the experiments. Further analysis indicates that the primary driver for the noise reductions is the 3=rev variation in the normal force time histories caused by changes in the elastic twist response to the TEF-induced pitching moment variations.