Blade-Vortex Interaction Noise Prediction Using a Rotor Wake Roll-Up Model

The theoretical methods used at ONERA for the blade› vortex interaction (BVI) noise prediction are described. Predictions are performed in e ve main steps: rotor trim, wake geometry, interacting vortices, blade pressure, and radiated noise. Three ways of introducing the wake ine uence in unsteady load computations are investigated. The e rst one assumes that the tip e laments of the wake lattices are dominant. The second one treats all of the e laments of the lattices as interacting vortices. The last one aims at modeling the local wake rolling-up and the vortex concentration. For each method, theoretical vortex geometries and intensities, loads, contours plots, and acoustic signatures are presented and compared to experiment. They show the benee t of using a roll-up model for BVI noise predictions. Indeed, the tip e lament assumption appears to not be general enough for realistic applications and the whole lattice approach does not seem reliable. On the contrary, fairly good aeroacoustic results are achieved using the roll-up model. Particularly, this modeling allows us to deal with rotor geometries and kinematics that are likely to generate inboard vortices.