波浪與鉸接多浮體系統(tǒng)相互作用的數(shù)值分析
發(fā)布時間：2019-01-18 13:28
【摘要】：本文基于線性勢流理論,采用高階邊界元方法,在頻域內(nèi)對波浪與鉸接多浮體系統(tǒng)相互作用的問題進行了數(shù)值分析。 超大型浮體、海上浮橋或者海蛇發(fā)電裝置等復雜的海洋工程結(jié)構(gòu),可以看成由多個剛性浮體通過鉸接方式組合在一起的一個多浮體系統(tǒng)。假設連接鉸光滑無摩擦,各浮體之間根據(jù)鉸接情況可以有相應的相對轉(zhuǎn)動。該多浮體系統(tǒng)在波浪作用下的運動是一個非常復雜的耦合問題,不僅要計算波浪與浮體間的耦合作用,還要計算各個浮體之間的水動力耦合的影響,同時還要考慮浮體間的連接力對系統(tǒng)運動響應的影響。對于這類問題我們采用總模態(tài)分析法進行研究,每個浮體具有6個自由度,因此由N個浮體組成的多浮體系統(tǒng)的總模態(tài)數(shù)為6N個。根據(jù)線性勢流理論,流場中的速度勢可以分解為入射勢、繞射勢和6N個輻射勢,采用高階邊界元方法,利用滿足自由水面條件的格林函數(shù)建立在浮體表面滿足的速度勢積分方程,通過求解該速度勢積分方程,得到繞射勢和浮體產(chǎn)生單位幅值運動時的6N個輻射勢,進而求出物體受到的波浪激振力和物體運動時產(chǎn)生的附加質(zhì)量、輻射阻尼。對于置于局部地形上的多浮體系統(tǒng),地形將對波浪場產(chǎn)生顯著影響進而影響多浮體系統(tǒng)的水動力特性。對于這類問題,文中將局部地形視為一固定結(jié)構(gòu),與多浮體系統(tǒng)一同建立速度勢積分方程,求解有局部地形時的波浪激振力和水動力系數(shù)。 對系統(tǒng)中每個浮體列運動響應方程,將浮體間的連接作用力作為外力,根據(jù)連接處的位移連續(xù)條件補充方程,得到以6N個響應幅值及浮體間連接力為未知量的方程組,通過求解該方程組得出系統(tǒng)各模態(tài)的運動響應幅值和連接力。對于浮體個數(shù)較多、連接方式比較復雜的多浮體系統(tǒng),為了便于建立這一方程組,根據(jù)最小勢能原理以及拉格朗日乘子法推導出約束矩陣并利用該約束矩陣給出這一方程組的統(tǒng)一寫法。對于線彈性系泊的多浮體系統(tǒng)推導了系泊等效剛度的表達式,給出了考慮系泊系統(tǒng)時運動方程組的統(tǒng)一寫法。 為了驗證本文方法及建立的數(shù)值模型的正確性,分別計算了波浪與兩個無連接浮體的相互作用、波浪與剛接和鉸接多浮體系統(tǒng)的相互作用、波浪與系泊浮體系統(tǒng)的相互作用,并與已發(fā)表的結(jié)果進行對比,對比結(jié)果吻合較好。最后利用本文建立的數(shù)值模型分別研究了波浪入射方向、水深、鉸接點位置、結(jié)構(gòu)布置方式、局部地形、系泊等影響因素對鉸接多浮體系統(tǒng)運動響應的影響,同時還計算了鉸接多浮體系統(tǒng)在不規(guī)則波作用下的運動響應。
[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.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：P731.2;P742
本文編號：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.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：P731.2;P742
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