扁平流线型箱梁涡激振动雷诺数效应研究

A study of Reynolds number effect on vortex-induced vibrations of a flat streamline box girder

风洞试验作为研究涡激振动的重要手段,由于其本身条件的限制,可能存在雷诺数效应问题,造成试验值和实际值的偏差。为了研究扁平流线型箱梁涡激振动的雷诺数效应,选取某大跨度斜拉桥的扁平流线型箱梁作为研究对象,利用风洞测振试验,通过调节模型系统自振频率,实现不同雷诺数下的涡激振动,研究扁平流线型箱梁的涡激振动特性及其雷诺数效应;利用风洞测压试验,研究了主梁断面的风压分布规律及其对涡激振动的贡献。结果表明:扁平流线型箱梁的涡激振动存在明显的雷诺数效应,高雷诺数下的振幅较低雷诺数下更小;在某一雷诺数下,与下表面相比,主梁上表面对涡激振动的贡献更大,尤其是腹板区域的下游部分;在不同雷诺数下,主梁脉动风压分布存在显著差异,脉动风压系数随雷诺数的改变是造成涡激振动雷诺数效应的原因。

Wind tunnel test, an important approach to investigate vortex-induced vibration, may lead to the Reynolds number effect due to the limitations in scale and wind velocity. Moreover, the Reynolds number effect would also cause the deviation between the test values and real values. To investigate the Reynolds number effect on vortex-induced vibration of a flat streamlined box girder, the girder of a long-span cable-stayed bridge was selected to be the subject. In the vibration test, by adjusting the natural frequency of the dynamic model, vortex-induced vibrations under different Reynolds numbers were obtained to achieve the vibration characteristics and related Reynolds number effects. The wind pressure distribution of the girder surface and its contribution to the vortex-induced vibration were obtained in the pressure test. The results show that the vortex-induced vibration of the flat streamlined box girder is intensively affected by the Reynolds number. The vibration amplitudes at higher Reynolds numbers are lower than those at lower Reynolds numbers. The contribution of the upper surface of the girder to the vortex-induced vibration is greater than that of the lower surface, especially the downstream area. Under different Reynolds numbers, the fluctuating pressure distributions of the girder are significantly different, and the variation of the fluctuating pressure coefficient with the Reynolds number may be the reason for the Reynolds number effect of the vortex-induced vibration.