【作者】 王剑；

【导师】 毕继红；

【作者基本信息】 天津大学 ， 结构工程， 2013， 博士

【摘要】 风雨激振是指斜拉桥拉索在特定风雨条件下的低频、大幅度振动，会使斜拉索发生疲劳破坏，降低斜拉索的使用寿命。由于这一现象涉及气、液、固三相耦合问题，其产生机理至今尚未明确，对此本文应用将滑移理论与CFD技术相结合建立理论模型及基于VOF法建立有限元模型的方法分别模拟斜拉索的风雨激振现象，深入系统的研究斜拉索表面水线振荡与斜拉索气动力及其振动之间的相互作用，揭示其产生机理，主要研究内容包括：考虑水膜形态变化对风压力和风摩擦力的影响,将滑移理论与CFD技术相结合提出了斜拉索风雨激振问题的理论模型，基于滑移理论和单质点单自由度振动理论建立了耦合的水膜运动方程和斜拉索振动方程。忽略斜拉索振动对水膜形态变化的影响，应用已建立的理论模型研究不同风速、不同风向下的斜拉索表面水膜形态和气动力变化规律及其内在联系，发现只有当气流方向与斜拉索下倾方向一致，且风速处于斜拉索发生风雨激振的风速范围内时，水膜形态变化及其引起的斜拉索气动力变化均呈现出明显的周期性，二者频率均接近斜拉索的自振频率，说明水线与斜拉索之间的共振是引发风雨激振现象的主要因素。考虑斜拉索振动对水膜形态变化的影响，应用已建立的理论模型进行斜拉索表面水膜形态变化与斜拉索振动间的双向耦合研究，分析发现当风速处于斜拉索发生风雨激振的风速范围内时，斜拉索表面会形成明显的上水线和下水线，同时斜拉索发生大幅度振动，振动主频接近斜拉索的自振频率，水膜形态变化及其引起的斜拉索升力变化具有相似的周期性，主频均有斜拉索的自振频率相近；进一步说明水线与斜拉索之间的共振是引发风雨激振现象的主要因素。将气液两相流理论与VOF法相结合，提出了模拟风雨共同作用下斜拉索表面水线的形成的新方法；应用这一方法对不同风速条件下受重力和气流共同作用时的水线初始形成时间、位置和形态进行了深入研究；在此基础上，应用点源补水的方式实现斜拉索表面水膜的连续和质量守恒，模拟风雨作用下斜拉索表面水线的形成与振荡，得到斜拉索表面水线运动规律和斜拉索气动力，并通过将气动升力施加到单质点单自由度模型上得到斜拉索的振动响应，研究水线运动对斜拉索气动力变化及其振动的影响，得到了与应用滑移理论数值计算相类似的结论，即上水线与斜拉索间的共振是产生风雨激振现象的主要原因。更多还原

【Abstract】 Rain-wind induced vibration (RWIV) is a large amplitude and low frequencyvibration of cables of cable-stayed bridges under wind and rain, which may cause thefatigue failure of stay cable and reduce its service life. As RWIV is a very complexproblem of coupling oscillation of gas, liquid and solid, its mechanism is still unclearso far. For this reason, in this paper RWIV of saty cable is simulated by combininglubrication theory with computational fluid dynamics (CFD) method and finiteelement method based on Volume of fluid method (VOF method), respectively. Onthis basis, the mutual influences of water film evolution, lift and vibration of cable areanalysed to reveal the mechanism of RWIV. The main research contents include:Considering the influence of wind pressure coefficient and friction coefficient onmorphology of water film around stay cable, a theoretical model for simulation ofmorphological change of water film around stay cable under wind and rain bycombining lubrication theory with CFD method is presented. And then2D coupledequations of water film evolution and cable vibration are presented for the first timebased on the combination of lubrication theory and vibration theory of single-modesystem.Negelcted the effect of cable vibration on the change of water-film morphology,the relations between the lift and the change of water-film morphology around staycable with different wind speeds and directions are investigated by theoretical model.The results show that only when wind speed is located in the certain region whenRWIV occurs and stay cable is down inclined along wind direction, the change ofwater-film morphology and the lift of stay cable have obvious periodicity with thesame frequency closed to cable natural frequency, which confirms the conclusion thatthe resonance between rivulets and cable may be one of the main reasons for RWIVThe two-way coupling between the change of water-film morphology aroundcable and cable vibration is studied by theoretical model considering the effect ofcable vibration on the change of water-film morphology. The results show that in thewind speed range when RWIV occurs, upper and lower rivulets are formed on cablesurface, and cable vibrates with large amplitude and the dominant frequency closed toits natural frequency. The variation of water film morphology and the lift of cable alsodisplay a significant periodicity with the similar frequency, which is similar to cable natural frequency. These further explain that the resonance between rivulets and cablemay leads to RWIV.A new method to simulate the evolution of rivulets on stay cable surface ispresented combining gas-liquid two-phase theory and volume of fluid method (VOFmethod). The initial time of rivulet formation, rivulet location and morphology underdifferent wind speeds and gravity are investigated by this method using CFX software.On this basis, the formation and oscilation of rivulets around cable are simulated bythe way of water supplement on point source, which can ensure the continuousdistribution and mass conservation of water film. The aerodynamic lift obtained byCFX is applied to a single degree of freedom model of stay cable to calculate cablevibration response. Similar to the numerical calculation results by lubrication theory,the conclusion that the resonance between upper rivulet and cable causes RWIV canbe drawn by study the influence of rivulet motion on aerodynamic lift change andvibration of stay cable.更多还原