Exploring aerodynamics of a rectangular cylinder using flow field and surface pressure synchronized testing technique

Abstract

This study uses two wind tunnel testing approaches: a sole high-frequency pressure scanning (HPS) approach, and a synchronized particle image velocimetry (PIV) and multipoint pressure scanning (SPMPS) approach, to investigate aerodynamic characteristics of a rectangular cylinder. HPS and SPMPS share identical experimental settings and device arrangements, while the SPMPS sampling frequency is much lower than HPS because the PIV system has a low sampling frequency in this study. SPMPS can simultaneously capture the flow field and surface pressure information. PIV measurement provides instantaneous flow field information, helping to analyze flow characteristics, and surface pressure taps offer both high- and low-frequency surface pressure information. It was found that for the rectangular cylinder, the zones of high turbulent kinetic energy and turbulent shear stress are associated with the lower negative pressure coefficient. In addition, diverse coherent structures in the instantaneous flow field resemble different critical points such as the saddle point, the repelling focus, and the attracting focus, and these coherent structures are associated with drastic changes in the pressure distribution or extreme pressure values. In particular, there is a visible flow reattachment, and the lift coefficient is more sensitive to the pressure distribution around the trailing edge of the rectangular cylinder. The convective velocity of wall pressure fluctuations is calculated based on the spatial temporal correlation of HPS information, and the convective velocity on the upper surface of the cylinder of SR = 3.25 is around 3.1 m/s providing evidence that Taylor's hypothesis breaks down for wall pressure fluctuations.