Nose Landing Gear

Introduction

Landing gear is one of the dominant sources of airframe noise for aircraft on approach, and accurately predicting the unsteady flow around its complex geometry is a demanding test for any scale-resolving CFD solver. The Partially-Dressed, Cavity-Closed Nose Landing Gear (PDCC-NLG) is a benchmark problem from the AIAA Workshop on Benchmark Problems for Airframe Noise Computations (BANC), based on a high-fidelity 25%-scale model of the Gulfstream G550 nose landing gear. In the partially-dressed configuration the hydraulic lines, steering mechanism and light cluster are removed and the gear cavity is sealed, giving a well-defined geometry for benchmarking aeroacoustic simulations.

The model was tested in the Basic Aerodynamics Research Tunnel (BART) at NASA Langley Research Center at a freestream velocity of 56.6 m/s (Mach 0.166) and a Reynolds number of 73,000 based on wheel diameter. The experimental campaign collected steady surface pressures, fluctuating surface pressures from dynamic pressure transducers distributed over the gear, and planar PIV measurements. HiPer's predictions of the unsteady surface pressure spectra are compared against the BART measurements below.

Unsteady Surface Pressure Spectra

The power spectral density (PSD) of the fluctuating surface pressure is compared against the BART measurements at sensor locations distributed across the gear — the main strut, torque arm, drag links, doors and wheels. Capturing these spectra requires the simulation to resolve the turbulent structures shed by upstream components and their interaction with downstream parts of the gear, the mechanism that drives landing gear noise. HiPer captures both the level and the spectral shape of the measured surface pressure fluctuations across the sensor locations.