The effect of turbulence intensity on the unsteady gust loading on a 5:1 rectangular cylinder

Abstract

The present work aims to study the effects of turbulence intensity on the three-dimensional spatial distribution of unsteady gust loading on a 5:1 rectangular cylinder. Three types of grids are adopted to produce uniform turbulent flows with different turbulence intensities and constant integral scales. The experimental results show that the turbulence intensity has a noticeable influence on the gust loading. An increase in the turbulence intensity results in a stronger spanwise correlation of the fluctuating pressures on the side surfaces. To reveal the three-dimensional aerodynamic effects of turbulence, a closed-form solution of a three-dimensional aerodynamic admittance function (3D AAF) is presented based on Ribner's three-dimensional spectral tensor theory. This 3D AAF model is expressed in terms of two-dimensional aerodynamic admittance function (2D AAF) for transversely fully correlated gusts and the gust-related spanwise correlation factor. The proposed 3D AAF can explain the mechanism of the three-dimensional aerodynamic effect of turbulence, which results in a more correlated lift force. It is observed that the filtered bandwidth in the spanwise direction amplifies as the turbulence intensity decreases, suggesting that the large-scale vortices in the separated flow are contaminated by smaller eddies. Consequently, the spanwise correlation of the lift force on a 5:1 rectangular cylinder will have the opposite tendency. Notably, it is confirmed that the 2D AAF depends only on the cross-sectional shape rather than the turbulence intensity.