Validation of hybrid numerical methods for aeroacoustic simulations in an industrial environment

Abstract

Airframe noise from deployed slats is considered to be the main contributor to the overall aircraft noise during approach and landing of modern airliners. Since it is generated in the vicinity of edges such as the slat trailing edge, recent slat designs attempt to achieve noise reduction by decreasing the flow velocity in this area through optimized slat positions with special focus to the slat gap. The main challenge for aircraft design is to combine noise reduction methods with aerodynamic performance requirements and therefore accurate but also fast numerical prediction methods are necessary. The goal of the present task is to demonstrate the capability of Computational Aeroacoustics (CAA) to predict slat noise in dependency of angle-of-attack (AoA), position settings, shape deformation and flight velocity in a timeframe compatible to industrial design needs. Therefore experimental data, measured by Pott-Pollenske et al. in the Large Low Speed Facility DNW-LLF of the German-Dutch Wind Tunnel foundation within the EU co-financed project OPENAIR, are compared to simulation data of two hybrid CFD/CAA approaches. Here the acoustic predictions rest on time-averaged steady flow solutions provided by Reynolds Averaged Navier-Stokes (RANS) simulation. In a subsequent acoustic step this steady flow data is translated into synthetic fluctuations of turbulent velocity or vorticity by DLR’s aeroacoustic simulation tools PIANO and DISCO to simulate the broadband turbulent sound field radiated from the high-lift system. […]