Computation of the BVI noise for the BO105 Model Rotor in forward flight and comparison with wind tunnel tests

The vortex lattice method jointly used with a local conformal mapping (to transform the thin blade into a thick one) is briefly described. This method is applied to a four-bladed rotor (BO105-Model Rotor) for two flight conditions. The noise emission in a plane below the rotor is calculated with an acoustic code which is based on the Ffowcs-Williams and Hawkings (FW-H) equation and the results are compared with tests in the German-Dutch wind tunnel. The aerodynamic results (thrust curve, wake evolution, vortex shedding) are analyzed. The contour map of the peak-to-peak noise shows the dependence of the results on the cutoff distance, on the method of regularization, on the flight parameters and on the thick profile type. Nevertheless, in all cases, the computed noise pressure level is near the measured one and the noise directivity shows the predominance of the advanced blade/vortex interaction. Some problems remain to be solved, especially the influence of a smaller time step.