大跨桥梁颤振与流动控制数值模拟

发布时间：2018-03-24 13:20

本文选题：软颤振　切入点：流动控制　出处：《哈尔滨工业大学》2015年硕士论文

【摘要】：在交通需求日益增长的趋势下,大跨桥梁取得了突飞猛进的发展。随着跨度增大,桥梁在结构上变为一种柔性体系,对风荷载作用极为敏感。桥梁硬颤振是一种风致自激发散性振动并极易造成结构毁坏。软颤振为渐发性颤振,没有明显的突发性颤振临界点,振动表现为等幅弯扭耦合振动。因此,研究硬颤振、软颤振及抑制桥梁风致颤振的流动控制方法对提高大跨桥梁的抗风设计水平和服役安全具有重大意义。本文采用CFD数值模拟方法研究了流线型桥梁主梁断面硬颤振和软颤振现象,并提出了采用主被动混合流动控制新方法抑制颤振。主要内容如下:建立苏通大桥和桃花峪黄河大桥施工状态下数值计算模型,采用CFD通用软件FLUENT模拟两座桥梁的静力三分力系数及流场特性,考虑了不同模型比例、网格数量、时间步长和计算风速对计算结果的影响规律,并将模拟结果与风洞试验结果进行对比分析,验证计算结果精确性并选择最优网格计算模型和求解策略,为下一步计算桥梁的风致振动奠定基础。利用强迫振动法和直接计算法计算不同攻角下两座桥梁的颤振临界风速,并比较两种数值方法计算结果与风洞试验结果的差异。直接计算法是利用FLUENT的用户自定义函数(UDF)和动网格技术实现桥梁断面的风致流固耦合振动模拟,结构振动响应采用四阶Runge-Kutta方法求解,得到各攻角下不同风速的结构动力响应时程曲线,进而得到颤振临界风速。同时,采用直接计算方法得到了两座桥梁发生软颤振现象的攻角和各攻角下发生软颤振风速范围。研究了不同响应状态下的桥梁断面尾流的旋涡脱落模式,解释了其产生原因及与响应之间的关系。通过在桥梁节段模型底部施加控制板,利用主被动吹、吸气相结合的流动控制方法抑制不同攻角下桥梁的颤振特性。对于非负风攻角,分析距断面底部不同距离控制板控制效果的优劣,并选择最优距离参数。对于被动方法控制效果不好的攻角采用主动吹、吸气方法,对于确定距断面底部距离的控制板,分析不同吹气和吸气速度对颤振特性的抑制效果,同时分析了相同吹、吸气流量下不同吹、吸气速度分布的控制效果。最后,通过断面附近速度流线与涡量等值线图揭示本文方法对颤振特性的控制机理。
[Abstract]:In the trend of increasing traffic demand, the long-span bridge has made rapid development. With the increase of span, the bridge becomes a flexible system in structure. The bridge hard flutter is a kind of wind-induced self-excited divergence vibration and can easily cause structural damage. The soft flutter is gradual flutter, and there is no obvious critical point of sudden flutter. The vibration is shown as the coupling vibration of equal amplitude, bending and torsion. Therefore, the hard flutter is studied. The methods of soft flutter and wind-induced flutter control are of great significance to the improvement of wind-resistant design and safety of long-span bridges. In this paper, the CFD numerical simulation method is used to study the hard fibrillation of the main girder section of streamlined bridges. Vibration and soft flutter, A new method of active and passive mixed flow control is proposed to suppress flutter. The main contents are as follows: the numerical calculation models of Sutong Bridge and Taohuayu Yellow River Bridge are established. The static three-point force coefficient and flow field characteristics of two bridges are simulated by CFD general software FLUENT. The effects of different model ratio, mesh number, time step size and calculated wind speed on the calculated results are considered. The simulation results are compared with the wind tunnel test results to verify the accuracy of the calculation results and to select the optimal grid computing model and solution strategy. The method of forced vibration and direct calculation are used to calculate the flutter critical wind speed of two bridges at different angles of attack. The results of the two numerical methods are compared with the results of the wind tunnel test. The direct calculation method is to simulate the wind-induced fluid-solid coupling vibration of the bridge section by using the user-defined function of FLUENT and the dynamic grid technology. The fourth order Runge-Kutta method is used to solve the structural vibration response. The time-history curves of the structural dynamic response under different wind speeds at different angles of attack are obtained, and the critical flutter velocity is obtained. The attack angles of soft flutter phenomena in two bridges and the range of soft flutter wind speed at each angle of attack are obtained by direct calculation method. The vortex shedding modes of cross-section wake under different response states are studied. By applying control panel at the bottom of the bridge segment model, the flutter characteristics of the bridge at different attack angles are restrained by using active and passive blowing and inspiratory flow control method. For the non-negative wind attack angle, the flutter characteristics of the bridge at different angles of attack are suppressed. The control effects of different distance control panels from the bottom of the section are analyzed, and the optimal distance parameters are selected. For the passive control methods, the active blowing and inspiratory methods are used to determine the distance from the bottom of the section. At the same time, the control effect of the same blowing rate, different suction flow rate and different suction velocity distribution on the flutter characteristics is analyzed. The control mechanism of flutter characteristics is revealed by using the contour diagram of velocity streamline and vorticity near the section.
【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

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