波浪与铰接多浮体系统相互作用的数值分析
发布时间：2019-01-18 13:28
【摘要】：本文基于线性势流理论,采用高阶边界元方法,在频域内对波浪与铰接多浮体系统相互作用的问题进行了数值分析。 超大型浮体、海上浮桥或者海蛇发电装置等复杂的海洋工程结构,可以看成由多个刚性浮体通过铰接方式组合在一起的一个多浮体系统。假设连接铰光滑无摩擦,各浮体之间根据铰接情况可以有相应的相对转动。该多浮体系统在波浪作用下的运动是一个非常复杂的耦合问题,不仅要计算波浪与浮体间的耦合作用,还要计算各个浮体之间的水动力耦合的影响,同时还要考虑浮体间的连接力对系统运动响应的影响。对于这类问题我们采用总模态分析法进行研究,每个浮体具有6个自由度,因此由N个浮体组成的多浮体系统的总模态数为6N个。根据线性势流理论,流场中的速度势可以分解为入射势、绕射势和6N个辐射势,采用高阶边界元方法,利用满足自由水面条件的格林函数建立在浮体表面满足的速度势积分方程,通过求解该速度势积分方程,得到绕射势和浮体产生单位幅值运动时的6N个辐射势,进而求出物体受到的波浪激振力和物体运动时产生的附加质量、辐射阻尼。对于置于局部地形上的多浮体系统,地形将对波浪场产生显著影响进而影响多浮体系统的水动力特性。对于这类问题,文中将局部地形视为一固定结构,与多浮体系统一同建立速度势积分方程,求解有局部地形时的波浪激振力和水动力系数。 对系统中每个浮体列运动响应方程,将浮体间的连接作用力作为外力,根据连接处的位移连续条件补充方程,得到以6N个响应幅值及浮体间连接力为未知量的方程组,通过求解该方程组得出系统各模态的运动响应幅值和连接力。对于浮体个数较多、连接方式比较复杂的多浮体系统,为了便于建立这一方程组,根据最小势能原理以及拉格朗日乘子法推导出约束矩阵并利用该约束矩阵给出这一方程组的统一写法。对于线弹性系泊的多浮体系统推导了系泊等效刚度的表达式,给出了考虑系泊系统时运动方程组的统一写法。 为了验证本文方法及建立的数值模型的正确性,分别计算了波浪与两个无连接浮体的相互作用、波浪与刚接和铰接多浮体系统的相互作用、波浪与系泊浮体系统的相互作用,并与已发表的结果进行对比,对比结果吻合较好。最后利用本文建立的数值模型分别研究了波浪入射方向、水深、铰接点位置、结构布置方式、局部地形、系泊等影响因素对铰接多浮体系统运动响应的影响,同时还计算了铰接多浮体系统在不规则波作用下的运动响应。
[Abstract]:Based on the theory of linear potential flow, the interaction between waves and articulated multi-floating bodies is numerically analyzed in frequency domain by using high-order boundary element method. Complex marine engineering structures such as super-large floating bodies, offshore floating bridges or sea snake power generation devices can be regarded as a multi-floating body system combined by multiple rigid floating bodies by hinged means. Assuming that the connection hinge is smooth and frictionless, the relative rotation between the floating bodies can be obtained according to the hinge condition. The motion of the multi-floating system under the action of waves is a very complicated coupling problem. It is necessary not only to calculate the coupling between waves and floating bodies, but also to calculate the effects of hydrodynamic coupling between various floating bodies. At the same time, the influence of the connection force between floating bodies on the system motion response should be considered. For this kind of problems, we use the total modal analysis method, each floating body has six degrees of freedom, so the total number of modes of the multi-floating body system composed of N floating bodies is 6N. According to the linear potential flow theory, the velocity potential in the flow field can be decomposed into incident potential, diffraction potential and 6N radiation potential. By using the Green's function which satisfies the free water condition, the velocity potential integral equation is established on the surface of the floating body. By solving the velocity potential integral equation, the diffraction potential and the 6N radiative potential of the floating body are obtained when the floating body produces the unit amplitude motion. Furthermore, the wave excitation force and the additional mass, radiation damping are obtained. For the multi-floating system placed on the local terrain, the topography will have a significant effect on the wave field and then affect the hydrodynamic characteristics of the multi-floating system. For this kind of problems, the local topography is regarded as a fixed structure, and the integral equation of velocity potential is established together with the multi-floating system, and the wave excitation force and hydrodynamic coefficient are solved. For the motion response equation of each floating body, the connection force between the floating bodies is taken as the external force, and the equations of 6N response amplitude and the connection force between the floating bodies are obtained according to the displacement continuity condition supplementary equation at the joint. The motion response amplitude and connection force of each mode of the system are obtained by solving the equations. In order to establish the equations for the multi-floating body system with more floating bodies and more complicated connection methods, According to the principle of minimum potential energy and Lagrange multiplier method, the constraint matrix is derived and the unified formulation of the equations is given by using the constraint matrix. The expression of mooring equivalent stiffness is derived for multiple floating body systems with linear elastic mooring, and a unified method for describing the equations of motion when mooring system is considered is given. In order to verify the correctness of this method and the numerical model established in this paper, the interaction between waves and two connectionless floating bodies, the interaction between waves and rigid and hinged floating bodies, and the interaction between waves and mooring floating bodies are calculated, respectively. The results are in good agreement with the published results. Finally, the effects of wave incident direction, water depth, hinge position, structure layout, local topography, mooring and other factors on the motion response of hinged multi-floating system are studied by using the numerical model established in this paper. At the same time, the motion response of hinged multi-floating system under irregular waves is calculated.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.2;P742
本文编号：2410767
[Abstract]:Based on the theory of linear potential flow, the interaction between waves and articulated multi-floating bodies is numerically analyzed in frequency domain by using high-order boundary element method. Complex marine engineering structures such as super-large floating bodies, offshore floating bridges or sea snake power generation devices can be regarded as a multi-floating body system combined by multiple rigid floating bodies by hinged means. Assuming that the connection hinge is smooth and frictionless, the relative rotation between the floating bodies can be obtained according to the hinge condition. The motion of the multi-floating system under the action of waves is a very complicated coupling problem. It is necessary not only to calculate the coupling between waves and floating bodies, but also to calculate the effects of hydrodynamic coupling between various floating bodies. At the same time, the influence of the connection force between floating bodies on the system motion response should be considered. For this kind of problems, we use the total modal analysis method, each floating body has six degrees of freedom, so the total number of modes of the multi-floating body system composed of N floating bodies is 6N. According to the linear potential flow theory, the velocity potential in the flow field can be decomposed into incident potential, diffraction potential and 6N radiation potential. By using the Green's function which satisfies the free water condition, the velocity potential integral equation is established on the surface of the floating body. By solving the velocity potential integral equation, the diffraction potential and the 6N radiative potential of the floating body are obtained when the floating body produces the unit amplitude motion. Furthermore, the wave excitation force and the additional mass, radiation damping are obtained. For the multi-floating system placed on the local terrain, the topography will have a significant effect on the wave field and then affect the hydrodynamic characteristics of the multi-floating system. For this kind of problems, the local topography is regarded as a fixed structure, and the integral equation of velocity potential is established together with the multi-floating system, and the wave excitation force and hydrodynamic coefficient are solved. For the motion response equation of each floating body, the connection force between the floating bodies is taken as the external force, and the equations of 6N response amplitude and the connection force between the floating bodies are obtained according to the displacement continuity condition supplementary equation at the joint. The motion response amplitude and connection force of each mode of the system are obtained by solving the equations. In order to establish the equations for the multi-floating body system with more floating bodies and more complicated connection methods, According to the principle of minimum potential energy and Lagrange multiplier method, the constraint matrix is derived and the unified formulation of the equations is given by using the constraint matrix. The expression of mooring equivalent stiffness is derived for multiple floating body systems with linear elastic mooring, and a unified method for describing the equations of motion when mooring system is considered is given. In order to verify the correctness of this method and the numerical model established in this paper, the interaction between waves and two connectionless floating bodies, the interaction between waves and rigid and hinged floating bodies, and the interaction between waves and mooring floating bodies are calculated, respectively. The results are in good agreement with the published results. Finally, the effects of wave incident direction, water depth, hinge position, structure layout, local topography, mooring and other factors on the motion response of hinged multi-floating system are studied by using the numerical model established in this paper. At the same time, the motion response of hinged multi-floating system under irregular waves is calculated.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.2;P742
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