【作者】 胡克；

【导师】 林哲；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2010， 硕士

【摘要】 随着社会不断发展,人类在科技和经济上都取得了巨大的进步,对于能源的需求不断增加使得浅海区域的油气开发已经不能满足人类的需要,海洋工程领域正在向深水推进,而其中以立管为代表的圆柱状海洋结构物广泛应用于海洋平台式离岸工程和海底管道系统。人们所要解决的深水钻探的最主要的问题之一就是解决管状物的涡激振动(VIV, Vortex-induced Vibrations)。当前,对于海洋平台中立管的涡激振动预报主要是通过实验来取得其水动力系数的,对于数值模拟的结果使用的较少。本文采用目前应用较为广泛的商业计算流体力学软件FLUENT数值模拟了刚性圆柱体的涡激振动实验,实验的雷诺数为10000,属亚临界雷诺数,实验内容包括静止时所受到的涡激振动以及振荡情况下的出现锁定现象时刚性圆柱水动力,将计算结果与实验值进行对比分析,发现升力系数和阻力系数的相对误差在20%以内,分析了可能存在的误差原因。在海洋资源开发的另一方面——深海养殖的开发也是越来越受到我国乃至世界各国的重视,人们都在寻求更好的养殖环境以及更高质量的养殖产品,因此将网箱推向了更远的深海,即深水网箱养殖应运而生。深海网箱体积庞大,而且往往要受到比近海更为恶劣的海况环境的考验,所以其水动力性能一直是各国海洋工程领域的热点话题。不过网箱整体的结构虽然庞大,但其组成的部件,如浮架、网衣相对于大型海洋结构物以及船舶而言仍属于小尺度漂浮柔性结构物,这类结构物与波浪和水流的相互作用机理的研究有待发展。对于浮架的研究,本文将其简化为圆形横截面的二维模型,在有来流情况下求解静止以及垂向振动于水面的浮杆的水动力。对于具有自由液面的圆柱的粘性流场,自由液面采用VOF(Volume of Fluid)法进行处理。通过大量的试算,选取一个合适的湍流模式,并确定湍流参数。本文研究的主要目的有两个一是当前比较重视的海洋工程领域的立管涡激振动的实验研究进行数值模拟,首先因为实验对于涡激振动的水动力的预报比较准确而应用广泛,但是成本较高,而使用CFD软件成本较低但是预报精度不够,本文尝试对于其中的一个涡激振动实验进行模拟,较为直观的计算出相对误差,为以后的数值模拟奠定基础；二是对于深海渔场的水动力研究进行一个数值预报,因为实验的准备工作通常都较为复杂,而做出一个准确的预报对于实验的顺利进行和对于数值的采集都极为重要,所以本文尝试使用FLUENT软件对水面上的简化后的渔场网箱浮架进行水动力求解。更多还原

【Abstract】 With the rapid development of society, human beings have made great progress both in science and technology and economy. Oil and gas exploitation at shallow water have failed to meet human’s ever-growing demand for energy. Offshore oil and gas industry, thus, are striding forward to deep sea. Particularly, more and more pivotal components of the circular cylinder shape represented by marine risers are widely used in the offshore platform and subsea pipeline systems, therefore it’s of great practical significance to carry out research on forced oscillation and vortex-induced vibration(VIV) of circular cylinder. Currently, hydrodynamic coefficients of vortex-induced vibration are obtained by experiments, the rapid development in numerical methods and hardware performance, however, have resulted in advanced computer facilities which allow the more extensive studies of numerical simulations of the fluid-structure interaction. This paper presents a numerical simulation of a rigid cylinder’s vortex-induced vibration with the application of the widely used commercial computational fluid software FLUENT, presenting the subcritical Reynolds numbers 10000. The experiment analyse at length of the rigid cylinder’s vortex-induced vibration when it’s still and the hydrodynamics of lock-in phenomenon when it’s oscillating. The relative error between lift coefficient and resistant coefficient is within 20% when compare the calculation result with the experimental data, and then try to analyse the reason of error if there be.The development of deep-sea aquaculture, on the other hand of marine resource exploitation, has drawn more and more concern from our country and the rest of world. Aiming to seeking the better aquaculture environment as well as the high quality aquaculture products, people have driven the net cages to the deep sea. Deep sea cage aquaculture,hence, was brought into being. Attribute to the fact that deep sea cage is bulky and frequently tested by the more adverse environment at deep sea, thus its hydrodynamics has always been the hot spot in marine engineering. Whereas, although net cage is bulky, its components such as floating frame and webbing are small flexible floating structures when compared with large marine structure. The principle development of such structures’interaction with wave and current is awaited. As for the floating frame, the research simplifies it as a two-dimensional model with circular cross section, resolving its hydrodynamics under the conditions when it’s still and vertically vibrating from the horizontal plane. As for the cylindrical viscous flow field with free surface, the free surface is dealt with the method of VOF(Volume of Fluid), and the turbulence model as well as parameters are settled through large numbers of trails.The two main purposes of this research are: One is the numerical simulation of vortex-induced vibration of circular cylinder in marine engineering. Above all, the forecast for the hydrodynamics of vortex-induced vibration with the method of experiment is widely used and relatively precise; the cost, yet, is high. The using of software CFD, on the contrary, is low in both cost and precision. This paper strives to calculate the relative error intuitively through one of the simulations of the vortex-induced vibration to lay a foundation for the following numerical simulations.The other is the numerical forecast for the hydrodynamics of deep sea fishery. As for the preparation for experiment is complicated and time-consuming, and a precise forecast is significant to the experiment processing smoothly and the collection of data. Hence this paper tries to find hydrodynamics solutions to the simplified floating frame of sea cage with the use of the software FLUENT.更多还原