Underbody wind noise sources are complex flow structures involving separation, vortex convection, and reattachment; with strong dependence on the detailed underbody geometry. Typically, the largest underbody noise sources originate from flow separations at the wheels, wheelhouse, engine/exhaust system, suspension, and structural cross-members. The resulting pressure fluctuations excite the underbody floor-pan structure and radiate into the vehicle interior as low-frequency noise. Accurate simulation of these noise sources requires solution of the time-varying flow structures and resulting wall pressure fluctuations (WPF) on the underbody surfaces. In addition, the ability to accurately capture energy-containing anisotropic structures and convection of cascaded turbulent structures over a wide range of length scales is necessary. Visualization of the flow structures that result in high WPF on underbody panels is useful to provide insight into geometry features that are good candidates for design improvement. This kind of noise source identification is extremely difficult to achieve experimentally, and is often not possible until far too late in the design process.
