桥梁主梁端部翼板颤振主动控制流固耦合计算

Flutter active control studies of bridge with flaps attached to deck edge by FSI calculation

安装主动控制翼板是提高大跨度桥梁颤振稳定性的一种有效方法。运用流固耦合技术对桥梁颤振主动控制进行计算分析,可以考虑气动翼板的大幅度扭转以及气动翼板和主梁端部的气动干扰效应。通过对商用软件FLUENT二次开发,建立了竖弯和扭转流固耦合数值仿真计算模型,并对主梁端部安装了主动控制翼板的大海带桥的颤振稳定性进行了数值仿真计算分析。系统地研究了前后翼板相对于主梁的角速度对颤振性能的影响。数值仿真计算结果表明:没有采用主动控制翼板时,颤振临界风速计算值和风洞实验值吻合良好。采用主动控制翼板后,当前翼板角速度与主梁反向,后翼板角速度与主梁同向时控制效果良好。且随着气动翼板角速度增大,主梁扭转位移减小。旋涡脱落图表明:作用在翼板的流场和作用在主梁的流场相互干扰,因此作用在整个系统上的力矩变化不仅来源于气动翼板的力矩,而且来源于流场形态的改变。计算表明在上述良好的控制时,气动翼板提供反向力矩,且与作用在主梁上的力矩相位相反,最大限度地平衡了作用在主梁上的力矩,使作用在主梁系统上的力矩均值减小,这是主动控制翼板提高桥梁颤振稳定性的原因之一。最后研究了气动翼板合适长度,计算表明:当气动翼板长度为主梁宽度的10%~15%时,颤振主动控制效果较好。

Long span suspension bridges,due to their flexibility and lightness,are much prone to flutter instability.A relatively new research area on aerodynamic stability for long span bridges is based on actively controlled flaps attached along the girders.Different from previous research,this paper proposes a new method to study the question.By secondary development of commercial computational fluid dynamics software FLUENT,the paper establishes a two-dimensional bending and torsional fluid-structure interaction numerical model to study flutter stability of a long span suspension bridges with active control wing plate which is attached directly to the edges of the deck.This method not only allows the large amplitude motion of the wing plate,but also considers the interaction between the aerodynamic force of the main beam and wing plate.The flutter stability is studied by controlling the rotational velocity of the wing plates with respect to that of the bridge deck.Numerical results show that the flutter critical wind speed of girder without wing plate is in good agreement with wind tunnel test.It is an optimal control law that the leading surface rotates in the opposite direction and the trailing surface rotates in the same direction with respect to the deck motion.The maximum torsional displacement amplitude decreases when increasing the rotational velocity of the winglet with respect to that of the deck.The rule is consistent with the conclusion of the wind tunnel experiment of relevant literature.The vortex shedding flow shows that in this system the flow patterns around the deck and flap are interacted by each other.So the stabilizing moment not only comes from the aerodynamic forces generated on control wing plates but can also be achieved through modification of the aerodynamic forces induced on the bridge deck.The calculated results show that in the optimal control,the aerodynamic wing provides the reverse moment and the moment phase is opposite to that of the main beam.It will maximize the moment balance of the main beam and decreases the average moment on the main beam system.This may be one of the reasons to improve the flutter stability of bridge with active wing plate.Finally,the proper length of the aerodynamic wing plate is studied.The calculation results show that the flutter active control is better when the wing length is 10%-15%of the main beam width.