Measurement of the low-wavenumber component within a turbulent wall pressure by an inverse problem of vibration.

An experimental validation is implemented for the measurement of a weak acoustic component within a turbulent wall pressure by an inverse problem of vibration. The turbulent flow is generated by a forward-facing step in a wind tunnel. In addition to the flow, an acoustic source with a low level excites the plate and plays the role of an additional acoustic component to be identified. The inverse methods called the force analysis technique and the corrected force analysis technique are used to compute the wall pressure fluctuations from the measurement of the plate vibration using an array of 13 accelerometers. The results show that contrary to the conventional techniques using pressure sensors, the inverse methods have a very good signal-to-noise ratio at the low wavenumbers. Indeed, the plate vibration is much more sensitive to the acoustic component than to the aerodynamic part. Moreover, this study shows that both methods can be used to isolate the weak acoustic part and identify its frequency spectrum.