方柱涡激振动的数值模拟与机理研究

发布时间：2018-01-30 07:20

本文关键词： 涡激振动漩涡弹性支撑方柱横向振动流向振动　出处：《兰州大学》2017年硕士论文　论文类型：学位论文

【摘要】：涡激振动是一种在自然界和工程领域中广泛存在的现象。当风、水流等流体流经柔性植被、大跨度桥梁、高耸烟囱、海底管线等非流线形结构时,便会在其尾流区诱发周期性的漩涡脱落,同时在结构上形成与来流速度垂直的周期性流体作用力,进而导致结构在这一方向上的周期性振动。涡激振动问题的本质是物体运动与尾涡运动之间的反馈。目前对涡激振动现象的研究主要以风洞试验为主,数值研究较少。本文采用udf涡激振动控制程序+动网格的方法分别模拟了单自由度和二自由度弹性支撑方柱的涡激振动问题,主要研究内容如下:1.本文首先研究了单自由度弹性支撑方柱在7.31U*15.23(对应实际风速4.74m/s～9.87m/s)风速范.围.内的涡激振动问题,数值模拟结果与Kumar等人的风洞试验结果吻合程度较好,证明本文自编udf程序的可靠性以及本文模拟方法的合理性,数值模拟过程中捕捉到了“锁定”、“拍”、“相位开关”现象,同时发现结构的横向振动改变了横向与流向上流体力的作用强度。2.已有的研究结果表明,频率比fst*、质量比M~*、质量-阻尼联合参数M~*ζ是影响涡激振动响应的主要参数。本文对不同质量比、质量-阻尼联合参数的方柱进行了涡激振动分析,研究M~*和M~*ζ的改变对振幅、“相位开关”启动的风速值以及对流体作用力的影响。3.研究“相位开关”启动机理,首先,对方柱周围速度场进行分析,本文发现,振动方柱周围存在与运动相关的振动绕流速度,它的出现减小了结构横向的速度差,并可以改变“相位开关”启动的风速值。4.对流场中的二自由度振动方柱进行建模,研究二自由度振动方柱分别在横向共振与流向共振状态下的运动规律,并且考虑流向振动对流体作用力的影响,给出单自由度系统代替二自由度系统进行涡激振动分析的使用条件。
[Abstract]:Vortex-induced vibration is a widespread phenomenon in nature and engineering. When wind, water and other fluids flow through flexible vegetation, long-span bridges, towering chimneys, submarine pipelines and other non-streamline structures. Periodic vortex shedding will be induced in the wake region and periodic fluid forces perpendicular to the inflow velocity will be formed at the same time. The essence of the vortex-induced vibration problem is the feedback between the body motion and the wake vortex-induced vibration. At present, wind tunnel experiments are the main research on the vortex-induced vibration phenomenon. There are few numerical studies. In this paper, the vortex-induced vibration of a square column supported by a single degree of freedom and two degrees of freedom is simulated by using the dynamic grid method of udf vortex-induced vibration control program. The main contents of this paper are as follows: 1. In this paper, we first study the single degree of freedom elastic bracing column at 7.31 UL 15.23 (corresponding to the actual wind speed of 4.74 m / s / s = 9.87 m / s). Vortex-induced vibration in wind speed. The results of numerical simulation are in good agreement with the results of wind tunnel test by Kumar et al., which proves the reliability of the udf program and the rationality of the simulation method in this paper. During the numerical simulation, the phenomena of "lock", "beat" and "phase switch" are captured. At the same time, it is found that the transverse vibration of the structure changes the force intensity of transverse and upward flow. The frequency ratio is fstn, the mass ratio is Mn, and the combined mass-damping parameter My * 味 is the main parameter that affects the response of vortex-induced vibration. In this paper, the mass ratio is different. Vortex-induced vibration analysis of a square column with combined mass-damping parameters is carried out to study the effect of the changes of M ~ (2 +) and M ~ ((1)) * 味 on the amplitudes. Study on the starting mechanism of the phase switch. Firstly, the velocity field around the opposite column is analyzed, and it is found in this paper. The velocity of vibration flow around the vibration square column is related to the motion, which reduces the velocity difference in the transverse direction of the structure. And can change the wind speed value of "phase switch" start. 4. The two-degree-of-freedom vibration column in the flow field can be modeled, and the motion law of the two-degree-of-freedom vibration column in the state of transverse resonance and flow resonance respectively can be studied. Considering the effect of the flow direction vibration on the fluid force, the application conditions of vortex-induced vibration analysis by the single-degree-of-freedom system instead of the two-degree-of-freedom system are given.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB123

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