双自由度圆柱体的涡激振动研究
发布时间：2018-11-08 13:34
【摘要】：在海洋工程领域,很多关键部件都具有类似圆柱体形状,由流体力学理论可知,这些海洋结构物极易受到粘性漩涡引起的结构振动和动力载荷作用,尤其当其固有振动频率和漩涡脱落频率一致时,整个结构物的涡激振动(Vortex-induced Vibration,VIV)会变得更加剧烈,最终导致结构物的疲劳破坏。本文在详细回顾和总结国内外关于立管涡激振动研究方法和最新动态的基础上,首先利用CFD中FLUENT模块求解不可压粘性流体中的Navier-Stokes方程,同时自编UDF (User Defined Function)接口程序和结合动网格技术数值分析了双自由度下的圆柱受迫振荡和自激振动问题;基于范德波尔方程提出了双尾流振子模型,再联合结构振子方程得到一种双尾流耦合振子模型。论文的主要内容总结为以下几点:1、构建了固定圆柱体绕流场的数值计算模型,将计算结果和文献中试验、数值结论对比从而验证了本文使用的数值计算方法和模型的可靠性,这为后续开展圆柱受迫振荡和自激振动的数值计算奠定基础;2、为了开展后续的均匀流和振荡流联合作用下涡激振动研究,首先对低雷诺数下均匀流中的圆柱体进行横向和双自由度受迫振荡研究,分别研究了振动频率和幅值对受迫振荡的影响,具体分析了升力系数和阻力系数时间历程曲线、尾流场的漩涡脱落频率和尾涡结构变化情况;分析了圆柱体在均匀流和振荡流联合作用下的受迫运动响应特征,发现振荡流改变了受迫振荡的锁定区间、水动力系数和尾涡脱落模式;3、数值模拟了双自由度弹性支撑圆柱体的涡激振动问题,计算得到了尾流场的漩涡脱落频率、振动位移时间历程曲线、圆柱系统的运动轨迹以及水动力系数时历曲线等运动响应特征和尾涡脱落情况;本文分别研究了质量比和阻尼比对双自由度弹性支撑圆柱体涡激振动的影响;数值模拟了圆柱体在均匀流和振荡流联合作用下的自激振动特征,结果表明振荡流扩大了自激振动的锁定范围,并且使得顺流向振动幅值大大增加,甚至超过了横向所能激发的最大幅值;4、基于Van der Pol方程提出了双尾流振子概念,用耦合振子模型准确地预报了试验中双自由度圆柱的涡激振动算例;通过对模型参数的讨论,确定了最优的耦合参数组合;在较高的顺流向与横向结构自振频率比算例下,观察到了一种由两个“8”字形叠加的新型圆柱运动轨迹。
[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.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U661.44;P75
本文编号：2318648
[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.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U661.44;P75
【参考文献】
相关期刊论文 前3条
1 王俊高;付世晓;许玉旺;宋磊建;;振荡来流下柔性立管涡激振动“分时特性”试验研究[J];振动与冲击;2014年21期
2 唐国强;滕斌;吕林;勾莹;张建侨;宋吉宁;;深海柔性立管涡激振动经验模型建立及应用[J];中国海洋平台;2010年03期
3 陈伟民;张立武;李敏;;采用改进尾流振子模型的柔性海洋立管的涡激振动响应分析[J];工程力学;2010年05期
相关博士学位论文 前3条
1 邓跃;低雷诺数下均匀流和振荡流共同作用的圆柱体受迫振动和涡激振动研究[D];中国海洋大学;2014年
2 秦伟;双自由度涡激振动的涡强尾流振子模型研究[D];哈尔滨工程大学;2013年
3 黄智勇;柔性立管涡激振动时域响应分析[D];上海交通大学;2008年
相关硕士学位论文 前3条
1 郑婷婷;螺旋侧板抑制海洋立管涡激振动的机理研究[D];江苏科技大学;2013年
2 张友林;海洋立管涡激振动抑制方法研究[D];江苏科技大学;2011年
3 梁亮文;低雷诺数下圆柱横向受迫振荡和涡激运动的数值分析[D];上海交通大学;2009年
，本文编号：2318648
本文链接：https://www.wllwen.com/kejilunwen/haiyang/2318648.html
