A study of aeroacoustics of two-dimensional generic vehicle profile

A D-shaped body, an elongated rectangular cylinder with rounded leading edge embodying the cross-section of a generic car body, is a popular generic vehicle profile used in the study of automotive aerodynamics. While extensive studies for a flow past D-shaped body mainly focus on the wake unsteadiness and drag reduction strategies, the associated aeroacoustics are less thoroughly investigated. The objective of the present study is to gain more insight on the flow-acoustic interaction for a flow past D-shaped body at low Mach number and moderate Reynolds number, where early flow separation and shear layer formation over the trailing edge are observed consistent with predominantly two-dimensional coherent structures. To this end, the D-shaped body aeroacoustics is investigated by direct aeroacoustics simulation (DAS), which solves unsteady, compressible Navier-Stokes equations in two dimensions, using the conservation element and solution element (CE/SE) method. This flow is dominated by a geometry induced separation and characterized as a wake flow. The separated flow is accompanied by alternating vortex shedding from the trailing edge. As vortex sheds from one side, a negative pressure pulse is generated at that side, while a positive pressure pulse forms at the opposite side. This alternating phenomenon eventually leads to the generation of acoustic waves that propagate radially toward the far field. The DAS solution is validated using experiment and numerical results in literature and the sound generation is studied quantitatively. Deduced that the far field definition in the present study is at least further than one acoustic wavelength, the DAS solution has shown well agreement with the theoretical aeroacoustics theories. The present research conducts detail investigation on the flow-acoustics interaction of a two dimensional generic vehicle profile and provides insight into the noise reduction strategies for automobile applications.