Reduced-Order Prediction of Unsteady Propeller Loading and Noise from Pylon Wake Ingestion

Abstract

Wake-ingesting propellers are attractive for low-speed propulsion due to their potential fuel savings and aircraft configuration benefits. Aeroacoustic concerns must be addressed for such installed pusher-propeller configurations, though limited validation of reduced-order models has constrained designers who require rapid and accurate predictions of unsteady blade loading and noise due to nonuniform inflow. The current work introduces a benchmark experiment aimed at low-speed pusher-propeller configurations including ingestion of thick wakes such as from an unstreamlined pylon or muffler. Data derived from wind-tunnel measurements on two-bladed propellers downstream of a blunt-ended NACA0015 airfoil include inflow characterizations, on-blade unsteady pressure measurements, and far-field aeroacoustic measurements. The experimental data are compared with blade-loading predictions stemming from existing indicial gust-response functions combined with Ffowcs Williams-Hawkings calculations of acoustic sources. A good correlation is found between the performance of the gust-response functions for blade loading and for far-field noise levels. The reduced-order approach presented here demonstrates promising accuracy, especially considering its low computational expense compared to computational fluid dynamics.