Characteristics of Wall Pressure Fluctuation in Curved Turbulent Boundary Layers

Direct numerical simulations at a low Mach number Formula: see text are conducted to investigate the complex interplay between near-wall turbulence and wall pressure fluctuations in curved turbulent boundary layers. The study focuses on two forward-facing chamfered steps with distinct curvatures, each featuring an upstream concave wall blending into a downstream convex wall. Curvature-induced pressure gradients influence Reynolds shear stress distributions and cause the mean velocity profile to deviate from the classical logarithmic law. Building on these fundamental observations of mean flow and turbulence statistics, the curvature effects on wall pressure fluctuations are further examined. Space–time correlations show that the convection velocity of wall pressure fluctuations first increases and then decreases, correlating with pressure gradient variations. A quantitative evaluation of seven recently developed semi-empirical models of wall pressure spectra reveals varying predictive performance across frequency bands, with most exhibiting larger prediction errors in the high-frequency region. Results suggest that accounting only for local pressure gradients is insufficient to accurately model the wall pressure spectra in curved turbulent boundary layers. Instead, boundary-layer parameters capable of more precisely capturing upstream pressure gradient history effects over curved walls with rapid transitions of pressure gradients should be incorporated into the curved wall pressure modeling.