LNG-FSRU船舶在波浪中的运动与液舱内流体晃荡的耦合数值分析

发布时间：2018-07-04 11:57

本文选题：液舱晃荡 + FSRU　；参考：《江苏科技大学》2016年硕士论文

【摘要】：随着FPSO、FSRU(Floating Storage and Re-gasification Unit)等大型载液船舶需求的增加,液舱晃荡这一经典问题再次受到学术界以及工程界的高度关注。晃荡研究方法主要包括试验研究、理论研究以及近几年发展较快的数值方法等。其中,试验研究结果准确,但研究周期长,成本也相对较高;理论研究在非线性方面的研究进展并不理想;数值模拟方面,相比计算时间长、占用资源大的有限元法以及计算流体方法,边界元法研究液舱晃荡更受研究者青睐。因为边界元法可以将研究问题降低一维来处理,在保证准确性的同时降低计算要求,减少计算时间。然而,边界元法往往会出现由于格林函数pq/1r的分母趋于零所带来的奇异积分的问题。针对这一问题,本文中应用的去奇异边界元法(DBIEM)将传统作法中原本直接布置于流体计算域表面节点上的所有奇点,移至计算域外面,即将积分表面与计算域表面分开,这样就很好的解决了奇点问题。本文除验证该方法准确性与适用性之外还将其应用于工程当中。以329mLNG-FSRU船为研究对象,研究FSRU船舶与液舱耦合作用下船体运动响应及液舱内部流体运动形态。主要内容如下:(1)建立FSRU船舶运动方程。根据三维频域势流理论中自由面格林函数方法,推导得到船舶在规则波中受到的波浪力,辐射力,绕射力等。接着求解船舶在波浪中的运动方程,计算得到船舶在波浪中六个自由度的运动响应。(2)通过传统边界元法,考虑液舱与FSRU船舶的频域耦合作用,基于BV水动力计算软件HydroSTAR分析带液舱船舶的水动力系数及运动响应,得到液舱、船体耦合作用下船舶运动响应,对比分析获得液舱晃荡对波浪中运动船舶的影响。接着进一步分析讨论了不同液舱形状,布置等情况下船舶运动受影响程度的大小。(3)基于去奇异边界元法,建立了模拟液舱内流体晃荡问题的流体动力学数值模型,并利用Fortran基于此方法研发了一套可以模拟任意尺度液舱晃荡的程序。研究了该方法的可靠性;确定了网格、时间步长、去奇异距离的取值范围;模拟了单向、双向不规则波激励下液舱内部流体的晃荡。(4)模拟FSRU实船液舱船体耦合下内部流体运动形态;选取典型工况下船体液舱耦合作用下船舶运动响应,通过程序将其施加为液舱边界条件。最终得到六个自由度运动共同作用时液舱船体耦合作用下液舱内部流体运动形态;为设计载液船舶或减摇水舱等的前期设计提供了快速有效的分析方法和技术手段。
[Abstract]:With the increasing demand of FSRU (floating Storage and Re-Gasification Unit), the classical problem of tank sloshing has been paid more and more attention by the academic and engineering circles. The research methods of sloshing mainly include experimental research, theoretical research and numerical methods which have been developed rapidly in recent years. Among them, the experimental results are accurate, but the research period is long and the cost is relatively high. Finite element method (FEM) and computational fluid method (CFM), which occupy a large amount of resources, are more popular in the study of tank sloshing. The boundary element method can reduce the one dimension of the research problem and reduce the calculation time and the accuracy of the method. However, the boundary element method often has the singular integral problem caused by the denominator of Green's function pq/1r tending to zero. To solve this problem, the desingular boundary element method (DBIEM), which is used in this paper, moves all singularities on the nodes of the surface of the fluid computational domain directly in the traditional method, that is to say, the integral surface is separated from the surface of the computational domain. This is a good solution to the singularity problem. This paper not only verifies the accuracy and applicability of this method, but also applies it to engineering. Taking 329mLNG-FSRU ship as the research object, the ship motion response and fluid motion pattern in the tank under the coupling of FSRU ship and tank are studied. The main contents are as follows: (1) the FSRU ship motion equation is established. According to the Green's function method of free surface in the theory of potential flow in three dimensional frequency domain, the wave force, radiation force and diffraction force of ship in regular wave are derived. Then the motion equation of ship in wave is solved, and the motion response of six degrees of freedom of ship in wave is calculated. (2) the coupling between tank and FSRU ship in frequency domain is considered by traditional boundary element method. Based on BV hydrodynamic calculation software HydroSTAR, the hydrodynamic coefficients and motion responses of ships with tanks are analyzed, and the ship motion responses under the coupling of tanks and hull are obtained. The effects of tank sloshing on the ship moving in waves are compared and analyzed. Then, the influence degree of ship motion under different tank shape and arrangement is discussed. (3) based on the boundary element method, a numerical model of fluid sloshing in tank is established. Based on this method, Fortran is used to develop a program that can simulate sloshing of tanks of any scale. The reliability of the method is studied, the value range of grid, time step size and the distance from singularity is determined, and the unidirectional simulation is given. The sloshing of fluid in tank under bidirectional irregular wave excitation. (4) simulating the internal fluid motion under the coupling of FSRU solid ship tank; selecting the ship motion response under the coupling action of ship tank under typical working conditions. It is programmed to be applied as a tank boundary condition. Finally, the fluid motion pattern of the tank under the coupled action of six degrees of freedom motion is obtained, which provides a rapid and effective analysis method and technical means for the design of liquid carrying ship or anti-roll tank.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U674.133.3

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