【摘要】：在海洋工程領(lǐng)域,很多關(guān)鍵部件都具有類似圓柱體形狀,由流體力學(xué)理論可知,這些海洋結(jié)構(gòu)物極易受到粘性漩渦引起的結(jié)構(gòu)振動和動力載荷作用,尤其當(dāng)其固有振動頻率和漩渦脫落頻率一致時,整個結(jié)構(gòu)物的渦激振動(Vortex-induced Vibration,VIV)會變得更加劇烈,最終導(dǎo)致結(jié)構(gòu)物的疲勞破壞。本文在詳細(xì)回顧和總結(jié)國內(nèi)外關(guān)于立管渦激振動研究方法和最新動態(tài)的基礎(chǔ)上,首先利用CFD中FLUENT模塊求解不可壓粘性流體中的Navier-Stokes方程,同時自編UDF (User Defined Function)接口程序和結(jié)合動網(wǎng)格技術(shù)數(shù)值分析了雙自由度下的圓柱受迫振蕩和自激振動問題;基于范德波爾方程提出了雙尾流振子模型,再聯(lián)合結(jié)構(gòu)振子方程得到一種雙尾流耦合振子模型。論文的主要內(nèi)容總結(jié)為以下幾點(diǎn):1、構(gòu)建了固定圓柱體繞流場的數(shù)值計算模型,將計算結(jié)果和文獻(xiàn)中試驗(yàn)、數(shù)值結(jié)論對比從而驗(yàn)證了本文使用的數(shù)值計算方法和模型的可靠性,這為后續(xù)開展圓柱受迫振蕩和自激振動的數(shù)值計算奠定基礎(chǔ);2、為了開展后續(xù)的均勻流和振蕩流聯(lián)合作用下渦激振動研究,首先對低雷諾數(shù)下均勻流中的圓柱體進(jìn)行橫向和雙自由度受迫振蕩研究,分別研究了振動頻率和幅值對受迫振蕩的影響,具體分析了升力系數(shù)和阻力系數(shù)時間歷程曲線、尾流場的漩渦脫落頻率和尾渦結(jié)構(gòu)變化情況;分析了圓柱體在均勻流和振蕩流聯(lián)合作用下的受迫運(yùn)動響應(yīng)特征,發(fā)現(xiàn)振蕩流改變了受迫振蕩的鎖定區(qū)間、水動力系數(shù)和尾渦脫落模式;3、數(shù)值模擬了雙自由度彈性支撐圓柱體的渦激振動問題,計算得到了尾流場的漩渦脫落頻率、振動位移時間歷程曲線、圓柱系統(tǒng)的運(yùn)動軌跡以及水動力系數(shù)時歷曲線等運(yùn)動響應(yīng)特征和尾渦脫落情況;本文分別研究了質(zhì)量比和阻尼比對雙自由度彈性支撐圓柱體渦激振動的影響;數(shù)值模擬了圓柱體在均勻流和振蕩流聯(lián)合作用下的自激振動特征,結(jié)果表明振蕩流擴(kuò)大了自激振動的鎖定范圍,并且使得順流向振動幅值大大增加,甚至超過了橫向所能激發(fā)的最大幅值;4、基于Van der Pol方程提出了雙尾流振子概念,用耦合振子模型準(zhǔn)確地預(yù)報了試驗(yàn)中雙自由度圓柱的渦激振動算例;通過對模型參數(shù)的討論,確定了最優(yōu)的耦合參數(shù)組合;在較高的順流向與橫向結(jié)構(gòu)自振頻率比算例下,觀察到了一種由兩個“8”字形疊加的新型圓柱運(yùn)動軌跡。
[Abstract]:In the field of marine engineering, many key components are similar to the cylindrical shape. According to the theory of fluid dynamics, these marine structures are easily subjected to structural vibration and dynamic loads caused by viscous vortex. Especially when the natural vibration frequency is the same as the vortex shedding frequency, the vortex-induced vibration (Vortex-induced Vibration,VIV) of the whole structure will become more intense, resulting in the fatigue failure of the structure. In this paper, based on a detailed review and summary of the research methods and latest dynamics of vortex-induced vibration in risers at home and abroad, the Navier-Stokes equation in incompressible viscous fluid is solved by using FLUENT module in CFD. At the same time, the self-made UDF (User Defined Function) interface program and the dynamic grid technique are used to analyze the forced and self-excited vibration of a cylinder with two degrees of freedom. Based on Van der Bohr equation, a double wake oscillator model is proposed, and a coupled oscillator model is obtained by combining the structural oscillator equation. The main contents of this paper are summarized as follows: 1. A numerical model of the flow field around a fixed cylinder is constructed. The comparison of numerical results verifies the reliability of the numerical methods and models used in this paper, which lays a foundation for the subsequent numerical calculation of forced and self-excited cylindrical oscillations. 2. In order to study the vortex-induced vibration under the combined action of uniform flow and oscillatory flow, the transverse and two-degree-of-freedom forced oscillations of a cylinder in a uniform flow with low Reynolds number are studied. The effects of vibration frequency and amplitude on forced oscillation are studied respectively. The time history curves of lift coefficient and drag coefficient, the vortex shedding frequency of wake field and the variation of wake vortex structure are analyzed in detail. The characteristics of forced motion response of cylinder under the combined action of uniform flow and oscillating flow are analyzed. It is found that the oscillatory flow changes the locking interval, hydrodynamic coefficient and wake vortex shedding mode of forced oscillation. 3. The vortex-induced vibration of a two-degree-of-freedom elastic supported cylinder is numerically simulated, and the vortex shedding frequency and vibration displacement time history curve of wake flow field are obtained. The motion response characteristics and wake shedding of cylindrical system such as motion trajectory and time-history curve of hydrodynamic coefficient; In this paper, the effects of mass ratio and damping ratio on the vortex-induced vibration of a two-degree-of-freedom elastic braced cylinder are studied. The self-excited vibration characteristics of a cylinder under the combined action of uniform flow and oscillating flow are numerically simulated. The results show that the oscillatory flow expands the locking range of the self-excited vibration and increases the amplitude of the vibration along the flow direction. Even more than the most significant value can be excited by the transverse; 4. Based on the Van der Pol equation, the concept of double wake oscillator is proposed, and an example is given to accurately predict the vortex-induced vibration of a cylinder with two degrees of freedom in the experiment by using the coupled oscillator model, and the optimal coupling parameter combination is determined by discussing the parameters of the model. A new type of cylindrical motion trajectory superimposed by two "8" shapes has been observed under the example of high frequency ratio of natural vibration to that of transverse structure.
【學(xué)位授予單位】：哈爾濱工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：U661.44;P75

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本文編號：2318648