【作者】 张华；

【导师】 李廷秋；

【作者基本信息】 武汉理工大学 ， 船舶与海洋结构物设计制造， 2014， 硕士

【摘要】 复杂海洋环境下的流固耦合问题是当今诸多学者在海洋工程领域中研究的重点。其中，动边界问题和多物体问题是研究流固耦合问题的重点之一。动边界问题主要包括两方面，即自由液面和物体运动边界，在船舶与海洋工程领域内经常涉及到的动边界问题包括船舶耐波现象以及波浪运动和翻卷等。而随着海洋发展战略逐步向深海延伸，多物体问题日益呈现出来，如海洋平台与储油轮、海洋平台与工程船等。在传统的基于贴体网格和动坐标系的计算流体力学方法中，对动边界和多物体的处理存在困难，主要体现在网格处理和多物体的描述上。为了克服这些缺点，本文以粘性不可压缩Navier-Stokes方程为基础，对其采用有限体积法离散，并结合大涡数值模拟和VOF方法，以及非边界拟合的切割网格法，构建了一套基于单一固定坐标系的描述多物体波激运动数值响应模型，较好的模拟了多个物体在波浪作用下的波激运动，实现了多个刚性结构物与流体的相互作用。本文主要从以下几个方面展开研究工作：（1）总结目前船舶与海洋工程领域中关于刚性多物体运动响应的研究现状与存在的问题，在此基础上提出本文研究的主要内容以及关键技术；（2）构建在固定坐标系下描述多物体波激运动的六自由度运动响应方程。传统方法中对动物体的描述大多是基于动坐标系，考虑粘性流体中如果用动坐标系描述物体会使流场控制方程变得冗长且求解复杂，特别是对于多个动物体，因而本文在充分利用切割网格技术的优势下，建立固定坐标系下的运动响应方程；（3）提出新的物面压力计算方法。由于多物体波激运动中物体周围流场呈现强烈的非线性，导致计算时物面处的压力振荡较大，直接影响到流体动力计算的稳定性，所以本文提出一种物面压力计算方法，用以缓解物面压力波动。本文通过对不同算例进行模拟，计算结果表明了在波浪作用下，多物体压力和波高的变化较单物体强烈；波激运动较静止物体有更高的波面升高和物面压力；与强制运动相比，可反映流场对结构物的影响。本文最后模拟了多个物体波激运动的响应，通过显示流场与结构物响应等结果，分析出多物体波激运动较单物体波激运动更复杂。本文的计算结果为以后深入研究多体刚性结构物波激运动打下了基础。更多还原

【Abstract】 Fluid-structure interaction problem of marine structures in the complex oceanenvironment is now the hot topic in ship and ocean engineering field,in which themoving boundary problem and multi-body problem is one of the key problems.Moving boundary problem mainly includes two aspects, namely, free surface andobject boundary. The popular moving boundary problems in the field of ship andocean engineering include ship seakeeping and the wave motion and folding, etc. Asthe ocean development strategy stretching gradually to the deep sea, multi-bodyproblems appear increasingly, such as offshore and FPSO, offshore platform andengineering ship, etc.Body-fitted grid and moving coordinate system in the traditional CFD methodshave much trouble in dealing with moving boundary problem and multi-bodyproblem, mainly reflects in the description of the grid processing and multi-body. Inorder to overcome these shortcomings, this paper based on finite volume method todiscrete incompressible Navier-Stokes equations, combined with large eddysimulation and VOF method, and the cut-cell method, to build a multi-bodyself-excited motion response numerical model based on single fixed coordinatesystem. And better simulated the multi-body self-excited motion under wave action,and finally realized the interaction between the multiple rigid structure and the fluid.This article mainly includes the following aspects of work.(1) Conclusion the research status and existing problems of rigid multi-bodymotion response, and on this basis, we put forward the main contents and keytechnologies of this paper.(2) Build a multi-body motion response equation based on fixed coordinatesystem. The traditional method of describing the moving body are mostly usingmoving coordinate system. Considering describing the body in the viscous fluid byusing moving coordinate system can make the Navier-Stokes equations become longand complex, especially for multiple moving body, this paper established the responseequation of the motion of the fixed coordinate system by making full use of the advantage of the cut-cell technology.(3) New surface pressure processing method is put forward. Due to the strongnonlinear flow around the objects while in the multi-body wave excitation motion,leads to the larger pressure oscillation at the body surface, directly affects the stabilityof hydrodynamic calculation. So this paper puts forward a kind of surface pressurecalculation method, in order to reduce the surface pressure fluctuation.This article simulated different cases. The results show that the changes ofpressure and wave height are greater in multi-body than that in sigle object. And waveexcitation movement gets higher wave elevation and greater surface pressure thanthat while the object keep stationary. And compared with the forced motion it canbetter reflect the influence on structure of flow field. In the end, the article simulatedmulti-body wave excitation movement response, through showing the flow field andthe response of the structures, analysis the multi-body wave excitation is morecomplex than single body wave excitation. The results of this paper laid thefoundation for future in-depth study of self-excited motion of rigid multi-body.更多还原