ON THE USE OF POD FOR IDENTIFYING ACOUSTIC AND TURBULENT COMPONENTS OF AN INHOMOGENEOUS WALL PRESSURE FIELD

In automotive industry, the acoustic comfort is become of primarily interest. Car window which is one of the relevant acoustic transmission paths, has to support two distinct pressure loadings: a Turbulent Boundary Layer excitation (turbulent component) and the acoustic component related to acoustic waves generated in the flow. In this study, Proper Orthogonal Decomposition is applied to two wall pressure databases in order to identify each component (acoustic and turbulent) of available databases. First, an inhomogeneous synthesized wall pressure field is considered. Second, Lattice Boltzmann Method is used to simulate the turbulent flow around a realistic car. Then wall pressure field is extracted on a specific area of the car window and used to perform POD application. In each test case, it is observed that at high frequencies, low order POD modes are associated with acoustic component of the aeroacoustic wall pressure field. Indeed, the spatial footprint of the first POD modes is dominated by the largest wavelengths, detecting at the smallest frequencies and associated with the most energetic turbulent part. To validate such separation, the frequency-wavenumber spectrum analysis as well as statistical analysis are performed.