The aim of this study is to provide a better understanding of the effects of a pressure gradient on the wall pressure beneath an equilibrium turbulent boundary layer. In particular, the effects on the aerodynamic part and on the flow noise are investigated. Excitation of the walls of a vehicle by turbulent boundary layers indeed constitutes a major source of interior noise in the field of transport industry. It is necessary to take into account the presence of a pressure gradient to represent the effect of the curvature of the walls, e.g. for the cockpit of an airplane. To this aim, simulations of turbulent boundary layers in presence of adverse and favorable pressure gradients are carried out using direct noise computation by solving the compressible Navier-Stokes equations. This method provides both the aeroacoustic contribution and the hydrodynamic wall-pressure fluctuations, which are responsible for the vibro-acoustic response of a panel. Results show that an adverse pressure gradient leads to higher levels of the direct acoustic emissions whereas lower levels are obtained in presence of a favorable pressure gradient. The study of the autospectra of the wall pressure fluctuations for the different gradients cases yield to the same hierarchy of levels. We further observed that these effects are amplified with the increase in the intensity of the gradient. First results for a high-Reynolds-number zero-pressure-gradient turbulent boundary layer are reported to figure out the influence of the Reynolds number in our numerical analyses.
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