Application of Lattice-Boltzmann method to rotorcraft aerodynamics and aeroacoustics

The aim of this work is to evaluate the accuracy and the computational performances of the CFD/CAA solver PowerFLOW®, developed and distributed by Exa Corporation, to predict the unsteady aerodynamic loads, the rotor wake development and the noise radiation of helicopters in Blade-Vortex Interaction conditions. The employed benchmark configuration is the 40% geometrically and aeroelastically scaled model of a BO-105 4-bladed main rotor tested in the open-jet anechoic test section of the German-Dutch wind tunnel in the framework of the HART-II project. In the present study, only the baseline operating condition of the test matrix, without higher harmonic control, is considered. All simulations are performed by assuming a rigid blade motion, but a computational strategy is employed to take into account the effective elastic deformation motion of the blade measured during the experiments. As expected, modeling the elastic blade motion leads to more accurate predictions of both unsteady air-loads and noise footprint. The effects of the mesh resolution on the aerodynamic and aeroa-coustic prediction is investigated. As a conclusive effort, the effects of fuselage scattering on the noise footprint are evaluated by using the same computational model to simulate two additional configurations: the isolated rotor of the HART-II configuration and the same rotor installed on a different helicopter fuselage. Significant far-field noise scattering effects are observed.