Π形板梁分离流扭转颤振机理数值研究

采用离散涡方法及流场可视化技术识别桥梁Π形板梁断面的旋涡脱落机制.流场可视化显示,来流绕过振动的Π形板梁断面时,在主梁断面前缘下部分离泡形成并发展为主涡结构,主涡结构沿主梁断面下表面漂移并经断面后缘下端进入尾流,主涡结构的形成时间及沿主梁断面的漂移过程对气动力起直接的主导作用;计算结果也表明恰当地布置稳定板能将颤振形态从单自由度扭转颤振转化为两自由度弯扭耦合颤振,颤振临界风速可明显提高.

Numerical study on the mechanism of torsional flutter for Π-shaped section

Four arrangements about vertical plate on Π-shaped section are investigated. A preliminary numerical study is undertaken to identify the vortex-shedding mechanism around deck based on random discrete vortex method. It can be concluded that the separation bubble generated at the lower windward corner and the main vortex structure developed from the separation bubble and its motion around the lower side of the prototype bridge deck are located at it lower surface and traveling across the lower side of the bridge deck downstream into the wake. The period of vortex shedding at the lower windward corner and development of vortex motion around the lower side of the prototype bridge deck make a direct influence on the value of the work done by the local suction pressure induced by the vortexes. Analysis results reveal that different arrange of vertical plates on Π-shaped section can convert torsional flutter to coupled flutter can increase the critical wind speed for the onset of flutter.