液舱内大幅晃荡引起的压强预报

本文基于流体体积(VOF)法就部分装载液体的液舱内的晃荡压强进行了二维数值计算.为了模拟大幅晃荡引起的冲击压强,重点对数值计算较为敏感的速度边界条件进行了数值处理.通过对某一矩形液舱内的液体晃荡的计算,得到了自由表面位置和压强的时间历经曲线.计算结果同实验值的比较显示:本方法可以用于计算预报大幅晃荡引起的载荷.     

基于Level-set法的液舱液体晃荡数值模拟

船舶液舱中液体晃荡现象已引起人们的深刻关注,液体晃荡载荷与效应成为航行中载液船舶安全性评估的重要内容之一.该文基于Level-set法,对一矩形液舱的两种工况下舱内的液体晃荡进行了数值模拟.通过计算,得到了液面起伏和压强的时间历经,结果显示Level-set方法可有效地模拟液体晃荡问题.     

液舱内三维液体非线性晃荡的数值模拟

晃荡是一种非常复杂的非线性液体流动现象,载液船舶的晃荡问题颇受关注,因为在外界的激励下液舱内会产生剧烈的晃荡现象,巨大的晃荡冲击力会造成结构的破坏.文中建立了三维晃荡数学模型及数值计算模型,借助处理自由表面的VOF(volume of fluid)方法对液舱内液体晃荡的自由表面进行追踪,编制程序实现了液舱内三维液体非线性晃荡的数值模拟,并就三维刚性液舱内粘性液体的自由晃荡和强迫晃荡做了分析,讨论了液体不同粘性系数对晃荡的影响.模拟结果证明了三维晃荡理论的可行性.     

基于SPH法的二维液体大幅晃荡数值模拟

随着海上液化天然气的开采和卸载的发展,LNG船部分充满舱的晃荡问题变得非常重要,成为船舶力学研究热点课题.文中采用光滑质点水动力学方法对二维液舱内液体大幅晃荡问题进行了数值模拟.将计算得到的波面图与试验结果进行了对比,吻合较好,验证了此法处理大幅晃荡问题的可行性.     

基于VOF法的半球-圆柱体液舱晃荡数值模拟

利用三维建模软件建立了纵荡激励下半球-圆柱体液舱内粘性液体晃荡的数值模型,利用计算流体动力学软件对不同工况下的液体晃荡进行了数值模拟,得到了液体对各监测点的作用力和液舱模型的一阶固有振动周期,分析了不同装载率、不同激励幅值、不同激励频率对液舱内液体晃荡的影响。     

三维弹性液舱晃荡数值模拟

文章建立了弹性液舱晃荡的数值计算方法。结构域采用有限元法进行离散,流体域的控制方程则采用有限体积法进行数值离散,结构域和流体域之间通过ALE法实现耦合。文中以31.6万吨VLCC实船的液舱简化模型为研究对象,基于MSC.Dytran对液舱内的晃荡载荷以及与弹性液舱的耦合作用进行了计算。首先将舱壁刚化,晃荡载荷与其它CFD计算结果进行比对,验证了计算方法的可行性及正确性。然后在此方法的基础上,模拟了三维弹性液舱内液体的晃荡,以研究外界激励、装载率等参数变化对晃荡载荷与响应的影响,揭示了弹性液舱内液体的晃荡特性。     

液舱内流体晃荡特性数值研究

本文利用VOF法对矩形液舱内液体晃荡进行数值计算。首先对舱内无任何隔板时液体晃荡作了模拟,并与相关文献中的实验结果进行了比较;然后在舱底中间设置一道不同形式的防晃隔板,对液体晃荡进行了计算。从结算结果看,本文提出的方法可以用于分析液舱内液体的运动和载荷,为设计合理的液舱结构形式提供理论依据。     

LNG船液舱晃荡数值模拟

为了研究船的液舱晃荡问题,基于CFD软件Fluent,计算、分析了LNG实船液舱内液体的三维晃荡特性.首先通过与试验数据的比较,验证了三维数值模型的正确性,分析了网格等要素对监测壁面压力的影响.其次通过数值模拟,分析了舱长变化对液体晃荡的影响,说明了三维研究的必要性.最后对LNG船的液舱晃荡进行了三维数值模拟.结果表明,数值计算模型可行,能准确揭示晃荡中的各种现象.     

基于Level-set法的液体晃荡与弹性液舱耦合作用研究

对基于Level-set法模拟液舱液体晃荡的数值模型进行了改进,实现了对大幅晃荡引起的抨击载荷的模拟.运用水弹性力学理论论述了液体晃荡与弹性液舱耦合作用的分析方法,建立了相应的水弹性力学方程.数值算例与实验结果的比较验证了对抨击载荷模拟的正确性;通过对晃荡载荷引起的结构响应的计算分析,得出一些关于结构响应特性的重要结论.     

Experimental Study and Numerical Simulation of Sloshing in VLGC Tanks with Internal Structures

文章对VLGC液舱模型内的晃荡做了数值及试验研究.装在液舱不同位置的5个压力传感器用于测量纵摇情况下晃荡对舱壁的冲击压力.同时建立了计算流体动力学的模型来模拟舱内的晃荡,采用基于RANS控制方程的标准资-着湍流模型,其中VOF法用于追踪自由表面,动网格技术用于更新计算网格.通过与试验压力时间历程的比较,验证了数值方法的有效性;数值研究了没有内部结构及有内部结构情况下的液舱模型,并且讨论了强肋框、水平桁及制荡舱壁对于压力及液舱内液体固有频率的影响.     

Numerical simulation of viscous liquid sloshing by moving-particle semi-implicit method

A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method （ICCG）, the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface.     

矩形液舱横荡流体载荷的Fluent数值模拟

采用CFD软件Fluent对二维矩形液舱不同舱内水深、不同激振频率时的横荡进行数值计算,并将数值结果与实验结果进行比较。结果表明,Fluent可以模拟自由面的翻卷和破碎运动现象,其对于距自由面较深点处流体载荷的计算结果与实验值相符合,但对于自由面附近点,尤其是舱顶上点处的砰击载荷,其计算结果与实验值差别较大。因此,对大幅晃荡的数值模拟仍需进一步研究。     

基于OpenFOAM的船舶与液舱流体晃荡在波浪中时域耦合运动的数值模拟

波浪中载液船舶运动激励舱内液体的晃荡,舱内液体晃荡产生的冲击力同时作用在舱壁上,进而影响船舶的运动姿态。波浪中船体水动力和时延函数是在势流理论范畴下采用切片法和脉冲响应函数方法计算获得的,液舱内液体非线性晃荡是基于粘性流理论实时计算模拟,两者耦合建立了波浪中载液船舶与液舱流体晃荡耦合的运动方程。论文基于开源CFD开发平台OpenFOAM,自主开发实现了船体运动与液舱晃荡的耦合计算程序,并进行了相应的数值模拟计算和验证工作。该方法完整地考虑了波浪、船体和液舱晃荡之间的耦合作用,并结合船体内外流场特点分别采用了势流和粘性流理论,具有较高的计算效率。通过数值模拟计算和模型实验研究表明,数值模拟计算能够清晰显现出液舱晃荡对船体全局运动影响,船体运动计算结果与模型实验结果吻合良好。     

大型补给舰船液舱晃荡载荷计算方法

随着补给舰船的大型化,补给舰船中的液舱晃荡问题开始凸显。为给大型补给舰船的液舱结构设计提供方便、可靠的晃荡载荷输入,基于改进的VOF法,以Youngs法重构自由液面,结合部分单元参数概念,提出了一种精度更高且数值稳定的、处理非矩形复杂舱室边界晃荡载荷的计算方法。通过对不同装载情况的液舱晃荡进行数值分析,并与Hirt-Nichols算法以及实验结果进行对比,证明该方法可有效改进自由表面的模拟效果,提高舱室内部速度、加速度和压力的预报精度。网格敏感性分析证明该方法的数值稳定性较好,较粗的网格也能达到较高的精度。所建立的晃荡载荷计算方法可用于对补给舰船的液舱晃荡设计载荷进行快速、准确的预报。     

采用耦合有限元、边界元方法的矩形储液舱中液体晃荡数值仿真(英文)

Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on tank perimeter. In this research, a numerical code was developed to model liquid sloshing in a rectangular partially filled tank. Assuming the fluid to be inviscid, Laplace equation and nonlinear free surface boundary conditions are solved using coupled FEM-BEM. The code performance for sloshing modeling is validated against available data. To minimize the sloshing pressure on tank perimeter, rectangular tanks with specific volumes and different aspect ratios were investigated and the best aspect ratios were suggested. The results showed that the rectangular tank with suggested aspect ratios, not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing pressure efficiently.     

Comparative assessment of liquid sloshing in dry and wet storage tank of floating offshore platform

In order to explore the characteristics of the single-layer liquid sloshing in offshore dry oil storage tank and the two-layer liquid sloshing in offshore wet oil storage tank, two series of experiments were carried out: one was free surface sloshing in a closed rectangular tank partially filled with colored water, and the other was interfacial sloshing in the identical tank but completely filled with white oil and colored water. The tank was mounted on a shake table and was subjected to harmonic horizontal excitation with different excitation amplitudes and a wide range of excitation frequencies, including the first seven natural modes of single-layer or two-layer liquid system. The present study find that the frequency responses of interfacial sloshing wave are analogous to those of the free surface sloshing wave, but smaller in amplitudes. The experiments also produce results that are unique to the two-layer liquid sloshing. For example, when the external excitation frequency is equal to or close to the odd mode natural frequency of two-layer liquid system, a complicated three-dimensional (3D) gravity-capillary wave might be generated at the oil-water interface. Finally, the comparisons of free surface and interfacial sloshing in the viscous damping ratio, higher sloshing modes, impact pressure amplitude and mass center displacement were conducted, which revealed the superiority of wet storage technology in structural safety and dynamic stability.     

Numerical simulation of violent sloshing by a CIP-based method

In this article, a new computational fluid dynamics simulation approach based on the constraint interpolation profile (CIP) method is applied to tackle the violent sloshing problem. The present study considers two-dimensional sloshing phenomena in a rectangular tank. By the proposed method, the sloshing problem is viewed as a multiphase problem that includes water and air flows. A stationary Cartesian grid is used and the free surface is solved by an interface capturing method. The CIP combined unified procedure (CCUP) scheme was adopted for the flow solver, and both the CIP scheme and the CIP conservative semi-Lagrangian with cubic interpolation polynomial (CIP-CSL3) scheme were used for interface capturing. For validation of the numerical method, a physical experiment was conducted with a rectangular tank for several frequencies and filling heights. A convergence check was first performed for the method. The numerical simulation results on violent sloshing show that the use of the CIP-CSL3 scheme as an interface capturing procedure gives much better results for the pressures and free-surface profiles than the conventional CIP scheme.