【作者】 秦银刚；

【导师】 周晓军；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2009， 博士

【摘要】 涡激振动是悬浮隧道研究中一个非常重要的问题,因为悬浮隧道在海流作用下会产生复杂的涡激振动以及频率“锁定”现象,并诱发流体与结构之间的相互作用,由此可导致结构失稳。由于横流向的涡激振动幅值比顺流向涡激振动幅值要大一个量级,因此本文着重研究悬浮隧道在横向涡激作用下的动力特性及其稳定性,所展开的研究工作主要有：1基于涡量运动学和动力学特性,针对悬浮隧道管段在运动中受到的流体荷载展开研究,推导出呈小振幅运动的悬浮隧道管段受到的流体荷载计算公式,在已知管段运动规律的前提下运用该公式能准确地计算出作用于悬浮隧道上的流体荷载；并对涡激振动机理进行总结,运用Morison方程估算作用于悬浮隧道上流体作用力。2将单跨悬浮隧道简化成两端简支的Euler-Bernoulli梁,采用分离变量法对单跨悬浮隧道的固有特性进行分析。研究表明：单跨悬浮隧道一阶固有频率的影响因素中附加质量系数对其影响最大,管段截面外直径影响次之,海水密度影响最小。将张力腿型多跨悬浮隧道简化为线性弹簧支撑的梁模型,采用Laplace正、逆变化求解多跨悬浮隧道管段固有动力特性。研究表明：多跨悬浮隧道固有频率随张力腿轴向等效刚度的增加而降低,悬浮隧道的固有频率与等效刚度之间成反比例关系；固有频率随着管段结构弹性模量、管段外直径的增加而增大,但不成线性关系。3利用混沌理论中的Melnikov方法分析单跨悬浮隧道在横流涡激作用下的稳定性判据,并对影响稳定性的因素进行分析。研究表明：随着跨度的增加,悬浮隧道稳定性降低；振动阶次越高悬浮隧道稳定性越好,在进行稳定性分析时可只分析一阶稳定性情况。悬浮隧道稳定性随洋流速度增加而呈下降趋势；管段弹性模量对稳定性呈线性影响关系；管段材料密度对稳定性影响也呈增加趋势；管段外直径对稳定性影响呈“勺子”状变化；流体阻尼系数对稳定性呈“V”字形影响；升力系数对稳定性呈下降阶跃函数影响关系。此外,将悬浮隧道管段振动视为对张力腿的参数激励而建立悬浮隧道张力腿振动模型,利用Lyapunov函数研究悬浮隧道张力腿在涡激作用下的稳定性判据。研究得出：张力腿稳定性随着振动阶次、结构刚度或初张力的增加都会呈增加趋势,但不呈线性变化关系；而随着参数激励频率、张力腿长度或动张力系数的增加稳定性会逐渐降低。4涡激振动模型试验结果表明：悬浮隧道的动力响应随着流速的增大而增大,其中振动最大位移随着流速增加呈线性增加。在相同流场环境条件下,增加支撑张力腿组数能减小管段结构的受力和动力响应幅值,但是会使张力腿的响应规律变得复杂；两节管段的动力响应规律与单节管段大体相同,单节管段悬浮隧道的速度响应幅值比两节管段悬浮隧道大。数值模拟结果表明：在管段迎流面和背流面分别出现正压区和负压区,来流速度越大,管段正负压区的压力值都越高,管段绕流场的分离点后移,漩涡释放频率也越大；圆形截面管体后形成的尾流区最大,椭圆形截面次之,多边形截面最小。5考虑悬浮隧道管段结构的非线性,在动力特性分析、稳定性分析及模型试验的基础上研究悬浮隧道管段在横向涡激作用下的动力响应。研究表明：对于单跨悬浮隧道发生首阶谐响应时的模态位移最大；悬浮隧道管段的弹性模量增大或管段外直径的增加都会对动力响应起抑制作用；而跨度的增加却会增大动力响应幅值；随着来流速度的增加悬浮隧道的动力响应幅值会增大。对于多跨悬浮隧道,增大张力腿的轴向刚度有助于抑制悬浮隧道管段的位移响应幅值；悬浮隧道管段位移响应幅值随着张力腿长度的增加而增加；不考虑非线性因素影响时随着张力腿间夹角越小对悬浮隧道管段动力响应的抑制作用越明显,而当考虑非线性因素影响时张力腿间夹角越小管段动力响应幅值越大。更多还原

【Abstract】 It is an important issue among the studies of submerged floating tunnel (SFT) for the vortex-induced vibration (VIV), the’lock-in’phenomenon and the fluid-structure interaction (FSI) of the submerged floating tunnel will occur when it undergoes the ocean current effect and the vortex-induced vibration will induce the submerged floating tunnel to become instable. Both vortex-induced transverse oscillation and in-line oscillation will occur when fluid flows around a structure. For the amplitude of transverse oscillation is larger than that in-line oscillation, in this dissertation, it focused on the dynamic characteristics and stability of submerged floating under transverse vortex-induced vibration and it carried out the main research work in the dissertation as followed:1 The dissertation premised that the amplitude of the oscillating SFT under vortex-induced effect was small, and derived the formula of fluid load based on the kinematics and dynamics characteristics of the vortex. It’s easily to determine the fliud load exactly acted on the SFT when its vibration regular had been known. The dissertation made a summary of the mechanism of vortex-induced vibration, and computed the fluid force acted on the SFT by Morison equation.2 The dissertation simplified single-span SFT as an Euler-Bernoulli beam simply suppored at both ends. It used separation of variables to analyze the intrinsic characteristics of the SFT. The study showed that the additional quality coefficient is dominant among those factors impacted on the first-order natural frequency of SFT, the impact of the outside diameter of pipe sections followed by, and the impact of the current density is nearly the least important. It simplified the multi-span SFT supported by tension-leg as a beam supported by linear spring, and it used the Laplace transformation and Laplace inverse transformation to study the intrinsic characteristics. The investigation showed with the equivalent axial stiffness increasing the natural frequency of multi-span SFT declined, and the intrinsic frequency is inversely proportional to the equivalent axial stiffness. With the elastic modulus of the SFT increasing the natural frequency increases, not being a linear relationship as well as the outside diameter of the tube.3 The dissertation derived the stability criterion of single-span SFT under the vortex-induced vibration from using of the Melnikov method of Chaos Theory. And it analyzed the factors affected the stability. The analysis showed that:With the increasing in spanlength, the stability of the SFT goes down. The higher of the vibration order the greater the stability greater of SFT is, therefore it can only consider the first-order stability on the stability analysis. With the increase of current velocity, the stability of the SFT dropped. The stability of the SFT increased linearly with the tube’s elastic modulus. It is an upward trend when the stability of the SFT affected by the material density of the SFT. The impact of the SFT’s outside diameter on the stability is of spoon-shaped, the impact of fluid damping on the stability is of V-shaped, however the impact of the lift coefficient on the stability is a decline step function. In addition it established the vibration equation of the tension leg on condition that considered the vibration of the SFT as parameters incentive. It derived the stability criterion of the tension leg under vortex-induced vibration from utilizing the Lyapunov function. The investigation showed the stability of tension inceased with vibration order, structural rigidity, or the initial tension, but not being a linear relationship.4 The result of the vortex-induced vibration model test showed that with the increase of current velocity, the dynamic response goes up, and the maximum vibration displacement increases linearly with current velocity. Under the same flow field conditions, the increase in the number of support can reduce the force acted on the SFT and reduce dynamic response amplitude, but the response regularity will be complicated. The axial strain of tension leg will increase follwed by the current velocity. The dynamic response regulerity of two tubes is the same as the one of single-tube, and the single-tube SFT’s response amplitude is larger than that of two tubes. Numerical simulation results showed that there are positive pressure zone in upstream surface area and negative pressure zone at the opposite point separately. The value of each area increased with the current velocity. Increasing the current velocity the separation point will prolong and the the vortex frequency will be greater. The wake area formed after the circular areas is the biggest, followed by elliptical cross section, the smallest of multilateral cross-section.5 This dissertation also studied the dynamic response under current effect based on considering the structural non-linearity, dynamic characteristics analysis, stability analysis and model test. The research showed:the first-order harmonic mode displacement is of maximum of the single-span SFT. Increasing the elastic modulus or the outside diameter of the SFT tube it will induce the dynamic response to decrease. With the span-length increasing, the dynamic response amplitude will rise, as well as the current velocity. With the axial stiffness of the tension leg increasing, the displacement response of multi-span SFT will go down.With the tension leg length increasing, the amplitude of displacement response will rise.The decrease of angle between the two tension legs contributed to curbing the displacement response amplitude more obvious when not considered the impact of non-linear factors, while when considered the impact of non-linear factors the smaller the angle between tension legs the greater amplitude of the dynamic response obtained.更多还原