大跨悬索桥桥塔尾流场影响区内吊索大幅风致振动的数值模拟

发布时间：2018-06-18 21:38

本文选题：悬索桥 + 吊杆　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：悬索桥由于其跨径大,美观轻盈,受力合理而成为大跨度桥梁的首选形式。但靠近桥塔的吊杆长细比很大,自振频率低,风吹过桥塔时沿顺风向发生较大分离,并在尾流形成较大尾流涡街,其尾流场影响区大,下游吊杆可能在这种尾流影响下发生振幅很大的驰振。长此以往,柔性吊杆很容易因振幅过大或相互之间的碰撞而发生破坏。本文通过基于有限体积法的计算流体力学方法,对吊杆在尾流影响下发生风致振动的响应进行研究。首先为了验证本文所用数值方法的可靠性,对单圆柱的固定绕流和流致振动进行了二维模拟。发现雷诺数较小时得到的气动力特征值与试验结果吻合很好,雷诺数较大时,本文得到的气动力结果比试验略大。这是因为雷诺数较小时流动界面的相关性小,雷诺数较大时,实际流动呈现三维特性,而二维模拟比较规则。对单圆柱的涡致振动在?=0.0208,=100时不同折减风速下进行了模拟,将得到的位移幅值与相同工况下前人的结果进行了比较,结果基本吻合。其次,对长方形排列四圆柱在没有桥塔尾流影响下的固定绕流和流致振动进行了模拟,发现在=45°时,四圆柱的横风向位移最大幅值均达到最大值,柱2和柱4的顺风向位移最大幅值也达到了最大值,并且柱4两方向位移最大幅值与单圆柱振动结果相比均有大幅增加,因此认为此时四圆柱间的相互气动影响最为不利。最后,对吊杆在桥塔尾流影响下的固定绕流和流致振动进行了模拟,对于固定绕流,发现零风向角下吊杆的气动力与单圆柱绕流结果相比有明显减小,此时吊杆升力变化的一阶频率与桥塔漩涡脱落频率完全相同,当来流风向角增大时,后排吊杆出现了升力变化开始由桥塔尾流和自身漩涡脱落共同控制的现象。对于流致振动,发现吊杆的大幅振荡是由于其自振频率与桥塔漩涡脱落频率相近时,在桥塔尾流的激励下,产生了类似于共振现象的沿椭圆形轨道的大幅振动。
[Abstract]:The suspension bridge has become the first choice of long-span bridges because of its large span, beautiful and lightness and reasonable force. However, the length of the suspension pole near the bridge tower is very large, the frequency of its self vibration is low, the wind blowing across the bridge tower is more separated along the wind direction, and the tail flow forms a large wake vortex street, and the tail flow field has a large influence area, and the downstream hanger may be affected by the wake. In the long run, the flexible hangers are easily damaged by excessive amplitude or collision between each other. In this paper, the response of the hanger to wind induced vibration is studied by the computational fluid mechanics method based on the finite volume method. First, the reliability of the numerical method used in this paper is verified. It is found that the aerodynamic characteristics of the Reynolds number are in good agreement with the experimental results. When the Reynolds number is large, the aerodynamic results are slightly larger than those of the test. This is because the correlation of the Reynolds number is smaller than the hourly flow interface, and the actual flow is larger when the Reynolds number is larger. The vortex induced vibration of a single cylinder is simulated under the different wind speed at =0.0208 and =100. The amplitude of the displacement is compared with the previous results under the same working condition, and the results are basically consistent. Secondly, the four cylinders in the rectangular arrangement are fixed under the influence of the tail flow without the bridge tower. The flow around and flow induced vibration are simulated. It is found that the maximum amplitude of the horizontal displacement of the four cylinders at =45 degrees reaches the maximum. The maximum amplitude of the displacement of the column 2 and the column 4 is also the maximum, and the maximum amplitude of the column 4 and two direction has a significant increase compared with the single cylinder vibration. Therefore, it is considered that the phase between the four cylinders is at this time. The mutual aerodynamic influence is most unfavorable. Finally, the fixed flow and flow induced vibration of the suspenders under the influence of the tail flow of the bridge tower are simulated. For the fixed flow, the aerodynamic force of the hanger is obviously reduced compared with the result of the single cylinder, and the first frequency of the lift change is exactly the same as the vortex shedding frequency of the bridge tower. When the wind direction angle increases, the lift force of the rear hanger appears to be controlled by the tail flow of the bridge tower and the vortex shedding of its own. For the flow induced vibration, it is found that the large oscillation of the hanger is due to the close frequency of its self vibration frequency to the vortex shedding frequency of the bridge tower, and the resonance phenomenon along the ellipsoid is produced under the excitation of the bridge tower tail flow. The large vibration of a circular orbit.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.3;U448.25

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