The excitation patterns and surface pressure characteristics of torsional vortex-induced vibration for typical bluff-body sections

As a commonly used bridge section, the 10:1 rectangular section shows strong sensitivity of vortex-induced vibration (VIV) to parameters such as angle of attack (AoA) and sectional geometry. To identify the excitation patterns of torsional VIV for a typical bluff-body section, wind tunnel tests and numerical simulations were employed to systematically investigate the surface load distribution characteristics and evolutionary patterns of flow fields during the torsional VIV process. During the research process, the vibration responses of four types of sections were first analyzed. Then, based on the flow field characteristics, the vorticity ratio was innovatively defined. The relationship between the average vorticity ratio and the amplitude was clarified, and the excitation patterns of torsional VIV at high AoA were summarized. The research results show that the lower leading-edge corner can effectively suppress the torsional VIV, and the presence of the leading-edge corner can significantly change the spatial distribution characteristics of the local mean pressure. However, the lower trailing-edge corner will exacerbate the torsional VIV. The unilateral asymmetric fluctuation of the surface pressure is the key factor inducing the torsional VIV. Additionally, the surface pressure in the key vibration-inducing region shows significant non-Gaussian characteristics during torsional VIV. The relationship between the mean vorticity ratio and torsional amplitude can be well fitted by an exponential function. Moreover, the amplitude of the torsional VIV at high AoA mainly depends on the leading-edge vortex and the impinging leading-edge vortex.