Wind tunnel measurements on the effects of leading edge geometry on surface pressures and wake flow of finite blunt plate

Abstract

In this paper, the surface wind pressure distribution and wake flow of finite blunt plates with different leading edge geometries are investigated. Particle image velocimetry and surface pressure measurement are performed on five typical leading-edge plates in a uniform wind. The results show that the wind pressure distribution on the blunt plate surface is largely affected by the leading-edge geometry. Specifically, as the leading edge angle increases from 60° to 180°, the peak values of the mean pressure coefficient and peak suction pressure coefficient decrease by 20.1 % and 11.6 % respectively. Meanwhile, the peak value of the r.m.s pressure coefficient increases from 0.041 to 0.126 and gradually approaches the mid-axis of blunt plate. In addition, larger separation angles lead to an increase in the reattachment length from 0.7d to 5.26d, but monotonically decrease the characteristic frequency of the plate. The analysis of the wake velocity field shows that an increase in leading-edge angle leads to an increase in the length of the low-velocity recirculation zone in the wake from 0.7d to 1.1d, and both the turbulent kinetic energy and Reynolds stress are larger in this region. Meanwhile, the flow streamlines and vorticity distribution become more unstable and complex, exhibiting a faster rate of evolution. Furthermore, the extraction of the wake structure using a proper orthogonal decomposition shows that the aerodynamic shape of leading edge has a limited effect on the large-scale vortex structure, but significantly affects small-scale vortex structure of high-order modes.