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.     

基于浅水波理论液体晃动初值问题的数值模拟

针对日益受到关注的液体晃动问题,提出了一种基于浅水波理论的研究方案.该方案采用浅水波理论而非势流理论导出系统控制方程,并通过哈密顿体系表达;利用中心有限差分法和Stormer-Verlet算法进行空间和时间离散;模拟了不同初值条件下的液体晃动情况并对比分析了影响系统非线性响应的主要因素.结果表明,基于浅水波理论能有效解决液体晃动问题;与Euler格式对比,Stormer-Verlet算法精度较高;除共振外对于系统非线性响应的影响容器初始位移比初始速度更显著;非共振情况一定条件下,充液容器运动过程中液体晃动能起到阻尼作用.     

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.     

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.     

储箱内液体晃动动力学分析及防晃结构优化

基于光滑粒子流体动力学( SPH)方法对无阻尼板和装有阻尼板的矩形储箱在加速度激励作用下,储箱内液体的晃动与冲击进行了三维数值模拟,将测试点的计算压力及液体晃动模拟与试验进行了对比,吻合较好.从而验证了SPH方法在求解具有强非线性液体大幅晃动问题方面的准确性和优越性.分析表明:阻尼板的安装对液体的晃动特性具有显著的影响...     

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...     

充液箱位置对航天器耦合特性影响分析

分析了液体非线性晃动时充液箱位置对带弹性帆板充液航天器刚-液-弹之间耦合特性的影响.假设耦合系统绕系统质心做俯仰运动,首先采用已推导的刚-液-弹耦合系统俯仰运动非线性动力学方程组,得到系统固有频率,给出固有频率简单近似解析表达式,分析充液箱位置对系统各阶固有频率的影响.随后应用多尺度法对耦合系统液体一阶主共振进行解析分析,发现充液箱位置是决定幅频曲线软、硬特性转换点的重要参数.给定外激励力矩时,不同充液箱位置稳态解对应多解现象,并随着激励频率改变,稳态解幅值随充液箱位置的变化曲线发生分岔.     

基于SPH的充液刚体刚-液耦合动力学建模

本文考虑刚-液耦合效应,基于SPH方法建立充液刚体动力学模型,该动力学模型不仅适用于微幅晃动问题,还适用于大幅晃动问题.首先建立了非惯性系下液体晃动的方程,其中,边界条件采用镜像虚粒子法.通过计算各流体粒子的绝对加速度,得到粒子惯性力对刚体质心的主矢和主矩,用达朗贝尔原理计算得到向质心简化的晃动力和晃动力偶矩,并引入刚体的约束方程,建立了考虑刚-液耦合的充液刚体的动力学方程.首先对给定周期性运动的充液刚体的液面振荡进行数值仿真,验证了建模方法的有效性;然后通过对受周期性激励力作用的充液刚体的运动和液面振荡进行数值仿真,分析了不同参数下系统的刚-液耦合特性.     

多腔充液晃动的等效特性

用等效力学模型法研究了多腔体充液晃动问题.在单腔体等效模型的基础上给出了多腔体充液体的等效模型,并分析了液体分散到多个腔体后对飞行器带来的影响.结果表明,从频带的改善到作用力的减少等方面,一般情况下多个腔体的力学特性更有利于飞行器的动力学与控制设计.     

充液航天器姿态的自适应非线性动态逆控制

讨论了充液航天器大角度姿态机动自适应非线性动态逆控制设计.推导了航天器-液体晃动耦合系统动力学方程.采用单摆等效力学模型对液体燃料晃动进行动力学建模.由于充液航天器控制系统的强耦合非线性,故采用神经网络构造系统的自适应非线性动态逆控制器.通过实际算例对该控制器的跟综性能进行了测试,结果证明该自适应非线性动态逆控制器在包...     

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%.     

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.     

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．     

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。     

Numerical simulation of liquid sloshing phenomena in partially filled containers

In the simulation of the dynamic load excited by sloshing in a partially filled tank, appropriate boundary conditions need imposing to calculate the impact pressure. Traditionally, a thin artificial buffer zone is adopted near the tank ceiling and a linear combination of free surface dynamic and rigid wall boundary conditions are imposed inside the buffer zone. This investigation demonstrates that no special treatment is needed to describe the free surface, because a two-fluid approach based on a level set method is used to solve the Reynolds-averaged Navier-Stokes (RANS) equations in both water and air regions and the interface is treated as a variation of the fluid properties. All the boundary conditions adopted are those usually accepted in solutions of Navier-Stokes or Euler equations. Sloshing in a rectangular tank excited by a horizontal harmonic motion is assessed numerically at different filling levels and excitation frequencies. The dependency of numerical solution on grid resolution, time step size and the interface thickness are investigated. Further, numerical tests are conducted for a rectangular tank with both 45° and 60° chamfered ceiling corners subject to a harmonic rolling motion. The comparison of computed results with experimental data show the developed numerical method is capable of the simulation of dynamic pressure loads exerted on the tank walls and ceiling excited by fluid sloshing.     

微重环境下Cassini贮液腔中液体晃动特性研究

针对我国某一型号大型卫星液体燃料Cassini贮箱（腰为圆柱,两底为半球）,应用有限元方法研究了微重环境下液体的小幅晃动问题和横向受迫晃动问题,采用Galerkin方法得到了系统的有限元离散方程；得到了晃动固有频率和等效力学模型参数.针对周期脉冲激励,推导了液体作用于贮箱壁的晃动力和晃动力矩计算公式并给出了数值计算结果和分析结论.     

Active vibration control of a fluid/plate system using a pole placement controller

We consider the problem of active reduction of the structural vibrations induced by the sloshing of large masses of fuel inside a partly full tank. The proposed study focuses on an experimental device mimicking an aircraft wing made of an aluminium rectangular plate equipped with piezoelectric patches at the clamped end and with a cylindrical tip tank, more or less filled with liquid. After deriving a representative finite-dimensional model of the complete system, containing the first five structural modes of the plate and the first three liquid sloshing modes, a controller is computed. Since our main scope is to control the most energetic mode of the structure, a full state-feedback method coupled with an observer is used. Finally, the controller is also tested for different initial conditions/perturbations and the results are compared with the ones obtained with an H _∞ controller. Experimental results illustrate the relevance of the chosen strategy.