Large-scale turbulence effect on streamwise surface pressures in separated and reattaching flows

This paper investigates the influence of large-scale freestream turbulence on aerodynamic pressure fluctuations on a rectangular cylinder based on large eddy simulation (LES) and wind tunnel experiments. The integral length scale of the freestream turbulence is up to 40 times the characteristic length of the bluff body. The LES computational model is validated through pressure measurements and particle image velocimetry (PIV) experiments. The study reveals a convergence phenomenon in turbulence length scale effects and identifies three key convergence characteristics in (1) spectral-spatial properties of wind pressures, (2) the non-Gaussian nature of negative peak pressures, and (3) the spanwise correlation of lift forces. These findings provide a reference for estimating the most unfavorable wind loads in engineering practice when the turbulence scale is uncertain. Furthermore, the paper explores the specific interactions between flow field fluctuations and wind pressure fluctuations on the rectangular cylinder. The results show that large-scale vortices outside the time-averaged shear layer induce significant low-frequency fluctuations in wind pressures, which, in turn, modulate the low-frequency flow fluctuations within the shear layer near the wall. This insight clarifies research priorities in turbulence blockage effects within wind engineering. Additionally, this study investigates the mechanism behind the elevation of fluctuating wind pressure under turbulent inflow conditions. It is found that this elevation stems from intensified momentum exchange outside the time-averaged shear layer, primarily driven by the upward convection of low-speed momentum near the shear layer and its intensified mixing with large-scale vortices in the incoming turbulence. © 2025 Author(s).