Numerical Simulation of Landing Gear Noise via Weakly Coupled CFD-CAA Calculations

The present work is relevant from the numerical prediction of aircraft noise via aeroacoustics hybrid methods. It is part of a more extensive effort, which final objective is the development of a robust and accurate CFD-CAA weak coupling methodology. Within this framework, we focus here on the so-called surface coupling approach, a technique that allows conducting weakly coupled CFD-CAA calculations. Such approach (which had been previously developed and validated on simpler cases) is here applied to a ralistic problem of aircraft noise, given by the acoustic emission of a nose landing gear in approach flight (a configuration that was addressed in the Airbus LAGooN program). For doing so, several preliminary tasks are first addressed, which are carefully handled and thoroughly detailed. Two CFD-CAA coupled calculations are then conducted, both being based on i) a same CFD dataset coming from an unsteady aerodynamic calculation (zonal DES), and ii) two distinct CAA calculations of different characteristics ; first, a CFD-CAA calculation is conducted for the so-called ‘baseline’ configuration (i.e. isolated gear within a free-field flow), so as to validate the coupling procedure, as well as to generate a reference solution for subsequent assessment of the mean flow effects induced by the experimental set-up. The validation of the coupling procedure is conducted via a direct comparison of the CFD-CAA results with either experimental or numerical (CFD, CFD-FWH) outputs obtained in the near-, mid, and/or far-field. With the view of assessing the mean flow effects, an alternative CFD-CAA calculation is then performed, which incorporates the realistic sheared jet flow characterizing the anechoic facility. This allows assessing the (partial) convection and refraction effects induced by such jet mean flow, which helps underscoring better the relevance of the present CFD-CAA hybrid approach when it comes to handle real-life noise problems.