Computation of wall pressure fluctuations in compressible turbulent channel flows

An accurate description of the spatiotemporal characteristics of the fluctuating surface pressure in wall-bounded flows is important for predictions of structural vibration and acoustic radiation. In this study direct numerical simulations are performed using high-order non-dissipative schemes to investigate the unsteady wall pressure in compressible channel flows at Mach numbers of 0.4 and 1.5 and friction Reynolds numbers of up to 510. The simulations are shown to capture both convective and acoustic contributions to the wavenumber-frequency spectra of wall-pressure fluctuations. At fixed frequencies acoustic peaks are identified at streamwise acoustic wavenumbers. These peaks are much lower than the convective peaks and decrease with decreasing Mach number. At Mach 0.4, the acoustic peaks are several orders of magnitude weaker than the convection peaks, indicating very small acoustic contributions, which is in contrast to predictions from semi-empirical models. The effect of a small surface hump on the wall pressure statistics will also be discussed.