Numerical Analysis of Propeller-Airfoil Interaction in a Distributed Propulsion System Using a Hybrid LES and FW-H Approach

Distributed propulsion is a promising approach that could achieve less emission, higher efficiency, and maneuverability for future Urban Air Mobility aircraft. However, the aerodynamic interactions between propellers and airfoils could lead to additional noise emissions. The present work conducted high-fidelity numerical investigations for a tractor-configured distributed propulsion system to gain further insights into the noise generation mechanisms due to propeller-airfoil interactions. Large-eddy simulations with adaptive mesh refinement are performed to predict the turbulent near flow field of the propulsion system, and the Ffowcs-Williams and Hawkings method is employed to determine the noise emission to the far field. Comparison of the simulation results with reference data demonstrates good accuracy of the numerical methods. The impingement of the propeller tip vortex leads to unsteady loading on the leading edge of the wing that is dominated by the blade passing frequency. Leading-edge separation bubbles occur on the retreating side of the propeller, yielding additional airfoil turbulent boundary layer noise sources. The far-field noise of the distributed propulsion system, however, is dominated by the propeller's unsteady loading noise, and the installation effect causes a slight increase of 1 to 2 dB in tonal and broadband noise levels as is shown by additional predictions of the acoustic field of an uninstalled distributed propellers and an isolated wing.