Synchronous wall-pressure and velocity measurements were acquired within a fully developed turbulent boundary layers over a smooth rigid surface under the effects of three mean pressure gradients. This allowed the development of a wavenumber-frequency cross-spectrum between the correlated pressure and velocity fluctuations. Measurement acquired for a friction Reynolds number of 3200–3300, and at a boundary layer parameter β between −0.81 and +0.68 at a wall-parallel plane located at a x 2 + ≈ 250 . Results show that both the streamwise and wall-normal velocity components are of equal relative importance when correlated with wall-pressure fluctuations. The wavenumber-frequency spectra of the pressure-velocity cross-terms collapse on one another for the three pressure gradient cases; however, the sub-convective levels of pressure and streamwise velocity spectrum show elevated levels for the adverse pressure gradient case, as high as 10 dB, when compared to the favorable pressure gradient case.
Butt et al. (Thu,) studied this question.