Ffowcs Williams-Hawkings acoustic analogy for simulation of NACA 4-(3)(08)-03 propeller noise in take-off condition

The goal of the paper is the evaluation of a RANS based approach for propeller noise prediction for typical aircraft take-off conditions characterized by zero free stream speed. The propeller geometry adopted for the study is the vintage NACA 4-(3)(08)-03 subsonic propeller, chosen for the wide amount of experimental data available at different rotational speeds (from 1600 to 4850 rpm) and different configurations (2-Blades and 7-Blades). The applied methodology is based on a Multiple Reference Frame RANS approach for the prediction of the steady-state load on the blades coupled with the Ffowcs Williams-Hawkings (FW-H) Acoustic Analogy, based on the Farassat & Brentner formulation of moving surfaces, for noise modelling. Optimized mesh-building guidelines and simulation strategy are provided in order to perform complete aerodynamic and aeroacoustic calculation in a time compatible with industrial design process requirements. Results of the simulation are compared with experiments showing the ability of this approach to predict noise with a discrepancy that lies in a range between 1 to 3 dB for higher rotational speeds. Investigations at lower rpm were carried out by performing an unsteady simulation as the flow field is characterized by separated flow on the blade, with a significant increase of computational time.