Numerical Simulation of the Aerodynamics and Acoustics of a Wall-Mounted Spoiler

A steep descent with deployed spoilers is a potential noise abatement procedure. This study investigates noise sources solely due to spoilers by examining a spoiler mounted on a flat plate. An experimental database consisting of aerodynamic loads, microphone measurements, on-surface pressure distributions, hot wire anemometry, and particle image velocimetry is presented. Numerical simulations, performed using a lattice Boltzmann solver ProLB, are validated against these experimental data. While the geometry is relatively simple, this is still a challenging case to accurately predict numerically, particularly the boundary-layer separation bubble that occurs upstream of the spoiler. The flow is characterized by an arch-type broadband wake without any coherent vortex shedding. There is a horseshoe vortex that originates upstream of the spoiler and wraps around both sides of the spoiler. Inboard of the horseshoe vortex there are a pair of ground vortices with the opposite sign vorticity to the horseshoe vortex. A combination of band-filtered on-surface pressures and three-dimensional numerical beamforming was used to determine the noise sources. As well as the broadband bluff body wake and the horseshoe vortex, the beamforming showed that the ground edge vortices and the spoiler side edges were the dominant acoustic sources.