波浪型圆柱涡激振动机理的数值研究
发布时间：2018-10-12 15:43
【摘要】：桥梁，是人类生活中离不开的重要的公共交通设施。在桥梁的诸多结构形式中，斜拉桥在当今大跨度桥梁中应用非常广泛，随着现代斜拉桥的跨度不断增大，斜拉桥拉索也趋于向更细长，材料更轻，柔性更大的方向发展，由于斜拉索具有柔度大、质量轻、阻尼小等特性，使得斜拉索更加容易由风载激励产生振动。其中，，涡激振动是斜拉索在低风速下最为常见的振动类型。本文结合近年来国内外学者对于钝体绕流及涡激振动研究的部分成果，由空气动力学减振原理入手，探讨一种对直圆柱展向改型而得到的波浪型圆柱的涡激振动特性，可为斜拉桥拉索的设计提供一些有益的思路和参考。 本文利用CFD软件FLUENT结合用户自定义程序UDF对直圆柱和波浪型圆柱在流场中的涡激振动进行了计算，其中，将圆柱在流场的运动简化为单自由度的弹簧-质量-阻尼系统模型，利用Newmark-方法求解圆柱的运动方程。本文首先对于雷诺数为200时的直圆柱的涡激振动作了详细的计算，得到圆柱横流向最大位移为0.543D。对尾流形态随频率比f n/f*s的变化的分析结果表明，当圆柱承受剧烈的涡激振动时，圆柱尾流的形态和旋涡间距将发生很大的变化。对质量比和约化阻尼的计算表明，质量比的大小对于圆柱振动系统的固有频率有较明显的影响，质量比越大，在发生共振时，圆柱的振动频率与圆柱的固有频率就越接近；约化阻尼的大小将影响圆柱的振动幅值，随着约化阻尼的增加，圆柱的振幅减小。 本文还选取了6个波浪型圆柱，分别对其固定绕流和涡激振动进行了数值计算。对于波浪型圆柱的固定绕流计算，分别获得了两个波长范围内的三种典型尾流形态，并对其进行了分析和阐述。对于不同的表面几何参数对波浪型圆柱的涡激振动响应的影响，得到了一些有用的结论：波浪型圆柱的流固耦合运动将会影响到其尾流结构，波浪型圆柱的固定绕流特性并不能为预测其涡激振动响应提供准确的参考，波长为2的波浪型圆柱可以通过增大波幅来减小涡振时的脉动位移，波面倾斜程度a/l并不决定波浪型圆柱的涡振响应。
[Abstract]:Bridge is an important public transport facility in human life. In many structural forms of bridges, cable-stayed bridges are widely used in today's long-span bridges. With the increasing span of modern cable-stayed bridges, the cable of cable-stayed bridges tends to be more slender, lighter and more flexible. Because of its high flexibility, light weight and low damping, the cable is more easily vibrated by wind excitation. Vortex-induced vibration is the most common type of vibration of stay cables under low wind speed. In this paper, based on the research results of blunt body flow and vortex-induced vibration at home and abroad in recent years, starting with the principle of aerodynamic vibration reduction, the characteristics of vortex-induced vibration of a wave-shaped cylinder obtained by spanned modification of a straight cylinder are discussed. It can provide some useful ideas and references for the cable design of cable-stayed bridge. In this paper, the vortex-induced vibration of a straight cylinder and a wave cylinder in the flow field is calculated by using the CFD software FLUENT and the user-defined program UDF. The motion of the cylinder in the flow field is simplified as a spring-mass-damping system model with a single degree of freedom. The Newmark- method is used to solve the equations of motion of a cylinder. In this paper, the vortex-induced vibration of a straight cylinder with Reynolds number of 200 is calculated in detail, and the maximum displacement of the cylinder is 0.543D. The results of the analysis of wake shape with frequency ratio f n/f*s show that the wake shape and vortex spacing of the cylinder will change greatly when the cylinder is subjected to violent vortex-induced vibration. The calculation of mass ratio and reduced damping shows that the magnitude of mass ratio has obvious influence on the natural frequency of cylindrical vibration system. The larger the mass ratio is, the closer the vibration frequency of cylinder is to the natural frequency of cylinder when resonance occurs. The magnitude of the reduced damping will affect the vibration amplitude of the cylinder, and with the increase of the reduced damping, the amplitude of the cylinder will decrease. In this paper, six wave-shaped cylinders are selected and their fixed flow and vortex-induced vibration are numerically calculated. For the calculation of the fixed flow around a wave-shaped cylinder, three typical wake patterns in two wavelength ranges are obtained, and analyzed and expounded. For the effect of different surface geometric parameters on the vortex-induced vibration response of a wave cylinder, some useful conclusions are obtained: the fluid-solid coupling motion of a wave cylinder will affect its wake structure. The fixed flow characteristics of a wave-shaped cylinder can not provide an accurate reference for predicting its vortex-induced vibration response. A wave-shaped cylinder with wavelength 2 can reduce the fluctuating displacement of vortex vibration by increasing the amplitude of wave. The slope of wave surface a / L does not determine the response of the wave cylinder to vortex vibration.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441.3
本文编号：2266683
[Abstract]:Bridge is an important public transport facility in human life. In many structural forms of bridges, cable-stayed bridges are widely used in today's long-span bridges. With the increasing span of modern cable-stayed bridges, the cable of cable-stayed bridges tends to be more slender, lighter and more flexible. Because of its high flexibility, light weight and low damping, the cable is more easily vibrated by wind excitation. Vortex-induced vibration is the most common type of vibration of stay cables under low wind speed. In this paper, based on the research results of blunt body flow and vortex-induced vibration at home and abroad in recent years, starting with the principle of aerodynamic vibration reduction, the characteristics of vortex-induced vibration of a wave-shaped cylinder obtained by spanned modification of a straight cylinder are discussed. It can provide some useful ideas and references for the cable design of cable-stayed bridge. In this paper, the vortex-induced vibration of a straight cylinder and a wave cylinder in the flow field is calculated by using the CFD software FLUENT and the user-defined program UDF. The motion of the cylinder in the flow field is simplified as a spring-mass-damping system model with a single degree of freedom. The Newmark- method is used to solve the equations of motion of a cylinder. In this paper, the vortex-induced vibration of a straight cylinder with Reynolds number of 200 is calculated in detail, and the maximum displacement of the cylinder is 0.543D. The results of the analysis of wake shape with frequency ratio f n/f*s show that the wake shape and vortex spacing of the cylinder will change greatly when the cylinder is subjected to violent vortex-induced vibration. The calculation of mass ratio and reduced damping shows that the magnitude of mass ratio has obvious influence on the natural frequency of cylindrical vibration system. The larger the mass ratio is, the closer the vibration frequency of cylinder is to the natural frequency of cylinder when resonance occurs. The magnitude of the reduced damping will affect the vibration amplitude of the cylinder, and with the increase of the reduced damping, the amplitude of the cylinder will decrease. In this paper, six wave-shaped cylinders are selected and their fixed flow and vortex-induced vibration are numerically calculated. For the calculation of the fixed flow around a wave-shaped cylinder, three typical wake patterns in two wavelength ranges are obtained, and analyzed and expounded. For the effect of different surface geometric parameters on the vortex-induced vibration response of a wave cylinder, some useful conclusions are obtained: the fluid-solid coupling motion of a wave cylinder will affect its wake structure. The fixed flow characteristics of a wave-shaped cylinder can not provide an accurate reference for predicting its vortex-induced vibration response. A wave-shaped cylinder with wavelength 2 can reduce the fluctuating displacement of vortex vibration by increasing the amplitude of wave. The slope of wave surface a / L does not determine the response of the wave cylinder to vortex vibration.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441.3
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