Numeric Modeling of the Noise Emission of a Pusher Propeller UAV Configuration

Aircraft noise models are required to account for the aircraft specific noise emissions in design and operation of Unmanned Aerial Vehicle (UAV) systems. While in the past most aircraft noise models were based on a semi-empiric modeling approach, a solely numeric approach is demonstrated in this work. A hybrid Computational Fluid Dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H) model is utilized to evaluate noise emissions of a pusher propeller UAV configuration. This model is capable of resolving all relevant tonal and broadband aeroacoustic sound sources by employing a scale resolving turbulence modeling. In-flight noise measurement data of this UAV is processed for validation of the numeric noise model. This validation is conducted for two cruise flight operating points. Firstly, noise hemispheres from measurement and numeric simulation are directly compared and, secondly, the computed noise hemispheres are interpreted as noise models and compared to the respective time domain flyover noise measurement data. Additionally, single event noise metrics are computed from measurement data and from numeric simulations and the results are compared. Measurement and numeric simulation data are in basic agreement regarding magnitude of sound pressure level and directivity of the noise emission and they are in higher agreement regarding single event noise metrics.