Modeling Interior Noise due to Fluctuating Surface Pressures from Exterior flows

There are many applications in which exterior flow over a structure is an important source for interior noise. In order to predict interior “wind noise” it is necessary to model both: (i) the spatial and spectral statistics of the exterior fluctuating surface pressures (across a broad frequency range) and (ii) the way in which these fluctuating surface pressures are transmitted through a structure and radiated as interior noise (across a broad frequency range). One approach to the former is to use an unsteady CFD model. While CFD is used routinely for external aerodynamics, its application to the characterization of exterior fluctuating surface pressures for broadband interior noise problems is relatively new. Accurate prediction of both the convective and acoustic wavenumber content of the flow across a broad frequency range can therefore present some challenges. This paper presents a numerical investigation of the spatial and spectral statistics contained in the flow downstream of a simplified side-mirror. Two distinct concentrations of energy are observed in wavenumber space at the convective and acoustic wavenumbers. This therefore opens up the possibility of describing a complex windnoise source in terms of the superposition of two simple analytical sources that can be fit to CFD data.