基于SPH方法的弹性体贮箱内液体晃动特性分析

采用Abaqus中的光滑粒子流体动力学(Smoothed Particle Hydrodynamics,SPH)求解器分析贮箱液体晃动.通过理论解验证SPH算法分析液体晃动的可行性;考察贮箱模型分别为弹性体和刚体时的压力变化,可知刚体贮箱的峰值压力比弹性体的大且其峰值出现更早;考虑贮箱为弹性体,研究在各因素下充液贮箱的晃动特性,包括充液量、晃动转角、液体材料属性和周期等.当贮箱充液量为2/3左右时,贮箱受液体晃动影响最明显;随着晃动转角的增大或周期减小,贮箱结构变形显著增大;液体材料属性对贮箱的影响有限.     

圆柱形贮箱液晃系统稳定性边界分析

本文研究了纵向激励下液晃系统的稳定性边界.首先利用等效摆模型获得纵向激励下液体晃动的等效动力学Mathieu方程,然后利用摄动法得到随阻尼、储液高度及贮箱直径变化时的液晃系统的稳定区域.结果表明,液体晃动阻尼、储液量及贮箱尺寸对晃动稳定性具有显著影响.     

谐波平衡法求解俯仰运动矩形贮箱中液体非线性晃动

针对俯仰运动贮箱中液体的晃动用变分原理建立了一类新的Lagrange函数,以此为基础可以解析方式来研究俯仰运动贮箱中液体的非线性晃动．首先将速度势函数Φ在自由液面处作波高函数叩的Taylor级数展开,从而导出自由液面运动学和动力学边界条件非线性方程组;然后用谐波平衡法(HBM)假设其解为各次主导谐波叠加的形式,并代入方程组中得到含有未知系数相应多个代数方程式;最后用Broyden法对代数方程组求解．以无挡板开口二维、刚性矩形贮箱为例,研究了液体的大幅晃动,就液体晃动的幅值而言,在一定激励频率范围内,理论计算值与试验结果吻合较好,同时液面波高出现明显的零点漂移现象．     

求旋转椭球形贮箱内液体小幅晃动基频的一种新方法

针对旋转椭球形贮箱内液体小幅晃动,建立了原点位于与箱于箱内静液面接触线处相切的圆锥的顶点的球坐标系,用高斯超几何级数解析表达速度势和波高的模态函数,通过伽辽金方法把变分方程转变为一个标准的特征值问题形式的频率方程,求解了不同尺寸比例的椭球形贮箱在不同的充液比和不同的Bond 数情况下液体小幅晃动的基频,把所求结果和已有...     

Cassini贮箱防晃设计

液体晃动会对飞行器动力学和控制系统造成影响,为了降低液体晃动带来的负面影响,本文从被动控制角度出发,对常见的Cassini贮箱提出几种防晃设计方案,并探索不同因素对贮箱防晃性能的影响.通过Flow3d商业流体软件对比分析环形挡板贮箱、扇叶挡板贮箱、环形浮板贮箱的性能后,给出了一种挡浮板复合结构贮箱,并通过对比验证了这种...     

液体晃动对飞行器控制系统影响分析

对于小幅晃动的充液飞行器流固耦合问题,可以采用等效力学模型来描述液体晃动.然而在研究液体对刚体的影响上,暂未有人从频域的角度进行建模.本文在已知液体各阶模态等效力学模型的基础上,利用虚功率原理和线性小扰动原理给出充液飞行器纵向模态舵偏角到姿态传函,并根据主导极点概念将充液飞行器高阶系统近似为二阶系统典型传递函数,以携带横放圆柱贮箱飞行器为例,分析了不同充液比和贮箱尺寸对典型传函系数的影响.结果表明,液体质量和转动惯量主要影响飞行器传递系数、时间常数,使得飞行器机动性和纵向模态自然频率降低;而液体晃动主要影响典型传函中相对阻尼系数,使得飞行器纵向相对稳定性降低.     

考虑推进剂晃动的火箭液固耦合分析的比拟算法

对于弹性容器与不可压无黏液体之间的线性耦合问题,已有缩聚对称形式的液固耦合系统有限元方程.利用比拟算法获得液固耦合系统的系统矩阵,将问题转化为通用有限元程序可以解决的问题.以包含贮箱的火箭模型为例,求解火箭的模态特性,其中包括由液体晃动所引起的火箭振动模态.结果表明此类模态与重力加速度有关,频率随重力加速度的增大而增大.     

微重力环境下刚液耦合系统液体晃动混沌现象研究

微重力下,柱形贮箱内液体晃动的速度势模态和表面位移模态难以解析表达,为揭示液-刚耦合运动的非线性特性,不失一般性地用常重力下液体晃动的速度势模态和表面位移模态近似表示微重力下液体晃动的速度势模态和表面位移模态.用泰勒级数展开法分析了微重力下柱形贮箱内的液体晃动,运用Lagrange方法导出了微重力下贮箱内液体与结构耦合系统的无量纲动力学方程组,并用Matlab软件对该方程组进行数值计算,发现当系统稳定时,面内、外模态分别具有同类的稳态动力学行为,包括静止、周期运动、准周期运动和混沌运动;在不同的外激励参数下,面内、外模态的稳态动力学行为发生变化.     

全管理柱形表面张力贮箱设计中的强度问题

卫星推进系统的贮箱设计除需考虑静强度和外压稳定性外，随机振动和正弦振动也是卫星发射和运行中的重要环境条件，因此卫星贮箱的设计必须作动力响应计算以便对所设计结构作出安全性结论。由于贮箱内充有大量液体，表面张力管理装置大部分浸于液体中，液－固耦合的影响必需在计算中予以考虑。本文就柱形表面张力贮箱的有限元动力计算方法，建模，计算结果和对结构设计的影响加以论述。     

微重力环境中重力梯度加速度引起的流体晃力和力矩的模拟

本文研究了关于旋转轴在贮箱的非对称轴上且远离贮箱的几何中心情况下，流体在微重力环境中由重力梯度加速度诱发的晃动特性，建立了问题的数学模型并对模型进行了数值模拟，我们以精密X光光变天文物理实验卫星（简称AXAF－S）作为研究对象，获得了由于旋转运动引的重力梯度加速度的数学表达式。关于晃动问题的数值是以卫星固连的非惯性坐标系为基础，目的是寻求一种较为易处理且适合于流体力学方程的边界和初始条件，通过数值计算获得了流体作用于卫星贮箱上的力和力矩。     

The Data Analyses of a Vertical Storage Tank Using Finite Element SOFT Computing

With the rapid development of the petrochemical industry, the number of largescale oil storage tanks has increased significantly, and many storage tanks are located in potential seismic regions. It is very necessary to analyze seismic response of oil storage tanks since their damage in an earthquake can lead to serious disasters and losses. In this paper, three models of vertical cylindrical oil storage tank in different sizes, which are commonly used in practical engineering are established. The dynamic characteristics, sloshing wave height and hydrodynamic pressure of the oil tank considering the liquid-structure coupling effect are analyzed by using ADINA finite element software, which are compared with the result of the standard method. The close numerical values of both results have verified the correctness and reliability of finite element model. The analytic results show that liquid sloshing wave height is basically in direct proportion to ground motion peak acceleration, the standard method of portion sloshing wave height calculation is not conservative. The hydrodynamic pressure generated by liquid sloshing caused by ground motion is not negligible compared with the hydrostatic pressure. The tank radius and oil height have a significant effect on the numerical value of hydrodynamic pressure. The ratio of the hydrodynamic pressure and hydrostatic pressure, which is named hydraulic pressure increase coefficients, is related to the height, which given by the GB 50341-2014 code in China have a high reliability. The seismic performances of tank wall near the bottom needs to be enhanced and improved in the seismic design of the oil tank.     

基于拉格朗日描述的罐车内液体晃动模拟

基于拉格朗日描述的柔性多体系统动力学理论,采用绝对节点坐标有限元方法描述液体大变形运动,开展铁路液罐车内液体晃动模拟研究.本方法能够模拟液体自由表面的连续性变化,并适用于研究具有复杂外形容器的内部液体晃动问题.基于流体力学牛顿体基础理论,推导液体粘性方程和满足体积不可压缩的条件方程;采用基于绝对节点坐标方法描述的实体单元进行液体网格划分;采用罚函数方法描述液体与罐体之间的接触关系,组建液体-罐体耦合多体系统动力学方程.仿真计算液罐车内液体的横向和纵向晃动行为,发现液体自由表面形状呈非线性变化,不同断面处的高度和形状不同.     

基于流固耦合的非满载液罐车制动性能分析

为研究非满载充液罐车紧急制动过程中液体晃动剧烈程度,采用有限单元法对液罐车减速过程中液体晃动进行模拟.分析了相同充液比下全防波板的数量差异、相同表面积的部分防波板安装位置对液体冲击力的影响,同时,将液体压力作为负载加载到防波板上研究防波板应力变化.仿真结果得出：纵向布置的全防波板随数量的增加,可以明显降低减速过程中液体对前封头的冲击力；与相同表面积的下端防波板相比,上端防波板对降低冲击力的影响较小；将液体晃动得到的压力作为防波板载荷输入,应力最大值出现在第二块防波板处.     

Analytical and numerical study of the effects of an elastically-linked body on sloshing

In order to investigate the effects of an elastically-linked moving body on liquid sloshing inside a tank, an analytical formulation and a numerical approach were proposed to assess hydrodynamic loads in a partially filled rectangular tank with a body connected to the tank by springs. The analytical approach was developed based on the potential theory to calculate fluid velocity field, and the dynamics of the liquid sloshing coupled to the moving body are described as a mechanical system with two degrees of freedom. The coupling between the fluid and the moving body is given by a damping force calculated based on the body geometry and the fluid velocity field. The proposed numerical approach is based on the Moving Particle Semi-implicit (MPS) method, which is a Lagrangian particle-based method and very effective to model nonlinear hydrodynamics due to fluid–structure interaction. In the numerical approach, the rigid body is modeled as a cluster of particles and the motions are calculated considering its mass, moment of inertia, hydrodynamic loads and springs restoring forces. The elastic link between the body and tank is modeled by applying Hooke’s law. Simple cases of floating body motion were used to validate the numerical method. Finally, analytical and numerical results were compared. Despite its simplicity, the analytical approach proposed in the present work is an efficient approach to provide qualitative understanding and a first estimate of the moving body effects on the sloshing inside the tank. On the other hand, the numerical approach can provide more detailed information about the coupling phenomena, and it is an effective mean for the assessment of the reduction of the sloshing loads due to the moving body with elastic link. Finally, the effectiveness of the concept as a sloshing suppressing device is also investigated.     

液体晃动条件下飞艇水箱动力响应仿真分析

为了增加重载飞艇的载重能力,在满足结构强度要求下飞艇上的贮水水箱需要采用薄壁结构、轻质材料等方法来减轻重量。水箱在空中受到风载荷或其他载荷的作用,会导致水箱中的液体发生晃动,水箱在液体晃动和外部载荷共同作用下,可能会遭到破坏。考虑流固耦合作用对水箱结构的影响,分别从液体小幅晃动和大幅晃动两种情况对水箱动力响应进行研究。对于大幅晃动的情况,以试验所得风载荷加速度函数作为激励,利用计算流体动力学(CFD)方法进行仿真分析。分析结果表明,小幅晃动条件下,即使水箱发生共振,其结构也不会遭到破坏;大幅晃动条件下,1. 3 mm以下壁厚钢材料水箱和2.1 mm以下壁厚铝合金材料水箱结构会遭到破坏。该分析结果可为水箱部分设计参数的确定提供参考依据。     

三维薄膜型FLNG储舱晃荡载荷的数值仿真

针对浮式液化天然气(Floating Liquefied Natural Gas,FLNG)船大型储舱内的液体晃荡问题,分别以薄膜型储舱的1∶20模型及原型为研究对象,采用CFD仿真方法分析百年一遇生存海况下液舱内晃荡载荷的基本规律和危险工况.结果表明:在真实海况下,现有FLNG储舱设计中的晃荡冲击载荷主要来源于船体纵向运动,可能出现的最大冲击载荷约为0.4 MPa,主要发生在纵舱壁与横向隔水舱的拐角位置,危险载液率为20%~30%及90%.     

Finite element analysis of fluid-structure interaction effect on liquid retaining structures due to sloshing

Fluid-structure interaction problems, which may be categorized into different types, have attracted the attention of engineers because of their numerous practical applications. Sloshing of liquid in a liquid filled container subjected to external excitations and coupled interaction between the liquid and container wall due to sloshing is one such problem. The focus of the present paper is on the development of a numerical scheme using finite element technique to calculate the sloshing displacement of liquid and pressure developed due to such sloshing. The scheme is extended to study the coupled effect of sloshing and container wall movement due to change in the liquid pressure.     

Comparison of finite element and pendulum models for simulation of sloshing

The pendulum model is a cost effective tool for the simulation of sloshing. However, the accuracy and applicability of the model has not been well established. In this article, we compare the simulation results obtained from the pendulum model and a more complicated finite element model for sloshing of liquids in tanker trucks. In the pendulum model, we assume that the liquid in the tanker is a point mass oscillating like a frictionless pendulum subjected to an external acceleration. In the finite element model, we solve the full Navier-Stokes equations written for two fluids to obtain the location and motion of the free surface. Stabilized finite element formulations are used in these complex 3D simulations. These finite element formulations are implemented in parallel using the message-passing interface libraries. The numerical example includes the simulation of sloshing in tanker trucks during turning.