A Numerical Study of Installation Effects of the Rudimentary Landing Gear Benchmark Problem

Abstract

A weakly compressible, wall-modelled Large-Eddy Simulation (WMLES) solver is used to predict the aerodynamic flow and far-field acoustics of the 4-wheel Rudimentary Landing Gear (RLG) from the Benchmark Problems for Airframe Noise Computations (BANC). The main purposes of this study are to test (1) methods to computationally model the mounting plane that was used in the experiments and (2) choice of solid FW-H surfaces to correctly predict the far-field noise including the installation effects. Both weakly compressible and incompressible solvers were used to simulate the flowfield. The reflective mounting plane was modelled with slip and no-slip boundary conditions. Predictions of far-field acoustics using different solid FW-H surfaces are compared with experimental measurements. With an incompressible solver, reflection peaks were absent from the predictions using only the landing gear as an integral surface, but could be partially recovered by adding the landing gear’s mirrored image into the FW-H integral surface. For the weakly compressible solutions, these reflection peaks were captured by using the landing gear surface as the FWH integral surface. However, the peaks were amplified by including the landing gear’s mirrored image. Using an FW-H integral surface that consisted of the landing gear and slip-wall mounting plane was found to generate excessive low-frequency far-field noise with a weakly compressible solver. The over-prediction with these FW-H surfaces, was eliminated by modelling the mounting plane with the exact dimensions and a no-slip boundary conditions.