【摘要】：橋梁，是人類生活中離不開的重要的公共交通設(shè)施。在橋梁的諸多結(jié)構(gòu)形式中，斜拉橋在當(dāng)今大跨度橋梁中應(yīng)用非常廣泛，隨著現(xiàn)代斜拉橋的跨度不斷增大，斜拉橋拉索也趨于向更細(xì)長，材料更輕，柔性更大的方向發(fā)展，由于斜拉索具有柔度大、質(zhì)量輕、阻尼小等特性，使得斜拉索更加容易由風(fēng)載激勵產(chǎn)生振動。其中，，渦激振動是斜拉索在低風(fēng)速下最為常見的振動類型。本文結(jié)合近年來國內(nèi)外學(xué)者對于鈍體繞流及渦激振動研究的部分成果，由空氣動力學(xué)減振原理入手，探討一種對直圓柱展向改型而得到的波浪型圓柱的渦激振動特性，可為斜拉橋拉索的設(shè)計(jì)提供一些有益的思路和參考。 本文利用CFD軟件FLUENT結(jié)合用戶自定義程序UDF對直圓柱和波浪型圓柱在流場中的渦激振動進(jìn)行了計(jì)算，其中，將圓柱在流場的運(yùn)動簡化為單自由度的彈簧-質(zhì)量-阻尼系統(tǒng)模型，利用Newmark-方法求解圓柱的運(yùn)動方程。本文首先對于雷諾數(shù)為200時(shí)的直圓柱的渦激振動作了詳細(xì)的計(jì)算，得到圓柱橫流向最大位移為0.543D。對尾流形態(tài)隨頻率比f n/f*s的變化的分析結(jié)果表明，當(dāng)圓柱承受劇烈的渦激振動時(shí)，圓柱尾流的形態(tài)和旋渦間距將發(fā)生很大的變化。對質(zhì)量比和約化阻尼的計(jì)算表明，質(zhì)量比的大小對于圓柱振動系統(tǒng)的固有頻率有較明顯的影響，質(zhì)量比越大，在發(fā)生共振時(shí)，圓柱的振動頻率與圓柱的固有頻率就越接近；約化阻尼的大小將影響圓柱的振動幅值，隨著約化阻尼的增加，圓柱的振幅減小。 本文還選取了6個(gè)波浪型圓柱，分別對其固定繞流和渦激振動進(jìn)行了數(shù)值計(jì)算。對于波浪型圓柱的固定繞流計(jì)算，分別獲得了兩個(gè)波長范圍內(nèi)的三種典型尾流形態(tài)，并對其進(jìn)行了分析和闡述。對于不同的表面幾何參數(shù)對波浪型圓柱的渦激振動響應(yīng)的影響，得到了一些有用的結(jié)論：波浪型圓柱的流固耦合運(yùn)動將會影響到其尾流結(jié)構(gòu)，波浪型圓柱的固定繞流特性并不能為預(yù)測其渦激振動響應(yīng)提供準(zhǔn)確的參考，波長為2的波浪型圓柱可以通過增大波幅來減小渦振時(shí)的脈動位移，波面傾斜程度a/l并不決定波浪型圓柱的渦振響應(yīng)。
[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.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U441.3

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