Fully-Dressed Main and Nose Landing Gear Aeroacoustics: LBM-Based Simulation and Experimental Validation

Abstract

Direct Noise Computation (DNC) of real, fully-dressed main and nose landing gear is carried out using wall-modelled LES (WM-LES) LBM simulations. State-of-the-art LBM solver ProLB is used for simulations. The major focus of this contribution is to evaluate the numerical methodology against the experiments conducted at DLR-AWB open jet facility. Besides validation, a substantial part of this investigation is to identify significant noise source(s) from the gears via simulations. To this end, noise characteristics, using the far-field noise spectra are assessed. Both landing gears belong to an aircraft of medium-range class. They are of 1:3.5 model-scale size with a resulting wheel diameter of 0.327 m and 0.268 m, respectively. A key aspect of these model-scale gears is to preserve all the minute geometrical details of the real gears, including bolts, pins, springs, etc. Simulations for the main gear used a free-field type computational setup without the wind tunnel nozzle and collector. Besides WM-LES LBM simulations of the main gear, a RANS simulation of the main gear is also carried out using the DLR TAU code. Aerodynamic results (ProLB, RANS) and aeroacoustic results (ProLB) compared for the main gear show a fairly good agreement with the measurements. A discussion of the best practices derived for the comparison of aeroacoustic results, with a specific focus on solid FW-H extrapolation versus DNC is included. An attempt to reproduce a noise reduction trend with simulations using a modified side-stay is also discussed. Nose gear simulations employ a complex wind tunnel setup, including a converging nozzle, foams surrounding the nozzle exit section, but without a collector. For the nose gear, preliminary near-field aerodynamic and far-field acoustic comparisons are discussed.