FFOWCS Williams-Hawkings Acoustic Analogy for Simulation of NASA SR2 Propeller Noise in Transonic Cruise Condition

Acoustic comfort is a big issue for the turboprop aircraft manufacturing industry, and therefore the development of quick and efficient numerical tools is a key point for the design-to-noise approach to airframe components. CFD approaches such as LES and DES are becoming more commonly employed in predicting aerodynamic generated noise for complex geometries, but these numerical methods are still very demanding of CPU usage for the industrial design process as used in the case of high speed propeller for turboprop applications. The goal of this paper is the simulation of propeller noise in transonic conditions based on a RANS approach for the aerodynamic computation of blade loads, coupled with Ffowcs Williams-Hawkings (FW-H) Acoustic Analogy, based on the Farassat & Brentner formulation of moving surfaces for the prediction of Sound Pressure Levels. The propeller geometry used for the calculations is the 8-blade NASA SR2 transonic propeller, chosen for the wide wind tunnel experimental data provided by NASA for different rotational speed and asymptotic Mach numbers. Results of the simulations are compared with experiments, showing the ability of this approach to predict noise with a discrepancy within a few dB for the different simulated conditions and microphones locations. Particular attention is given to the set of corrections to be applied to acoustic experimental data in order to be consistently compared with free field CFD results. The CFD simulation strategy has been refined to perform complete aerodynamics and aeroacoustic calculations with highly competitive computational cost.