兰州大学机构库 >土木工程与力学学院
方柱涡激振动的数值模拟与机理研究
Alternative TitleNumerical Simulation and Mechanism Reasearch of Vortex-Induced Vibration of A Square Cylinder
蔚杰
Thesis Advisor武建军
2017-05-01
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword涡激振动 漩涡 弹性支撑方柱 横向振动 流向振动
Abstract

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7.31< <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 、质量比 、质量-阻尼联合参数 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 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。

Other Abstract

The phenomenon of vortex-induced vibration(VIV) is common in nature and engineering field. When viscous fluid passes through unstreamlined structures, such as flexible vegetation, large-span bridges, high-rise buildings, high chimney stacks, as well as marine pipelines, alternate eddy form and shed from the wake of them. Meanwhile periodic force will be loaded on these structures and they will viberate in the direction perpendicular to the flow. The problem of vortex-induced vibration is therefore a fascinating feedback between body motion and vortex motion. Most study on VIV are carried out in tunnel, but few by means of numberical simulation. This paper analysises the vortex-induced vibration of one degree of freedom and two degrees of freedom elastic support cylider by using a fluid-structure-interaction udf program and dynamic mesh method. The main contents are as follows:

1. The problem of vortex-induced vibration of one degree of freedom elastic support cylider is first studied in the range of 7.31< <15.23. The maxium amplititud obtained from this simulation is compared with the experimental result of Kumar et al., it shows very well agreement. So it proves the reliability of the fluid-structure-interaction udf program and the simulation method. The phenomenon of ‘lock-in’, ‘beat’, ‘phase switch’ have been observed in the simulation. The transverse vibration reduce the intensity of wind load both in transverse direction and in approaching direction. 2. Results of previous research indicate that frequency ratio ,mass ratio ,mass-damping parameter  are important parameters in the problem of VIV. Square cylinders with different mass ratio and mass-damping parameter have been studied in this paper to find the relationship between  and amplititude of vibration、wind load、initiate velocity of ‘phase switch’. 3. The mechanism of ‘phase switch’ is also studied in this paper, with the help of flow field analysis. A kind of diffraction velocity related to vibration is found near the square cylinders, it reduces velocity contrast in transverse direction, and its variation change the initiate velocity of ‘phase switch’. 4. Two degrees of freedom of elastic support cylider is modeled. Resonance properties both in transverse direction and flow direction have been studied. This step try to make sure what degree impact on wind load when cylinder viberate in flow direction. A simple using condtion of using 1-DOF VIV system subsititute 2-DOF VIV system is given in this paper.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226548
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
蔚杰. 方柱涡激振动的数值模拟与机理研究[D]. 兰州. 兰州大学,2017.
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