Coupled uRANS and FW- H Analysis of Installed Pusher Propeller Aircraft Configurations

Abstract

In this paper the aeroacoustic phenomena characteristic of a pusher-propeller cofiguration and their aerodynamic causes are discussed and analyzed. The work was done in the frame of the European-funded project CESAR (Cost Effective Small AiRcraft). The configuration under study is an industrially relevant design with a wing-mounted pusher propeller, which features a close coupling of the turboshaft engines exhaust nozzles and a five bladed propeller. An established numerical analysis approach is applied in this study, which couples a high-fidelity unsteady aerodynamic simulation using the DLR TAU-Code with the DLR APSIM Code for a subsequent aeroacoustic evaluation. APSIM computes the sound propagation into the fareld based on the Ffowcs-Williams/Hawkings (FW-H) equations. A detailed analysis of the contributions of various components of the installation as well as flight condition specific parameters toward the overall noise generation by the propeller is presented. Furthermore, the possible scattering effect of the wing and nacelle is discussed. A detailed analysis of specific aspects of the numerical approach for the aeroacoustic analysis is made through a comparison between the results achieved using both a FW-H impermeable and permeable formulation. The numerical error due to both jet exhaust and propeller wake impingement on the FW-H permeable surface as well as the impact of cutting a hole in this permeable surface to avoid possible issues of these effects are discussed.