一类Cassini贮箱液体小幅晃动问题的研究

针对航天工程中常见的某一类特殊几何形状贮箱(腰为圆柱,两底为半球),利用R itz变分法研究了其中液体的小幅自由晃动问题和横向受迫晃动问题,得到常重下液体晃动的固有频率和振型、速度势分布、波高变化、压力分布、液体作用于贮箱壁的力等用于指导工程实践的重要物理量.同时得出一个对于以后的研究具有指导性意义的结论:对于轴对称形状贮箱,当其作任意横向运动时,其中液体只有对应周向模态阶数为1的反对称模态才被激发.     

应用瑞利-里滋法分析储箱内液体晃动模态

将瑞利-里滋法进一步拓展到储箱内液体晃动的模态分析中,结合瑞利商给出储箱内带自由液面液体晃动基频的计算方程,使得瑞利-里滋计算模态的方法得到进一步的扩展,同时对液体晃动基频计算提出更为有效的计算方法.此外,应用有限元程序ADINA,对圆柱形储箱内带自由液面的晃动频率和模态进行数值模拟.研究了液面半径和深度对液体晃动固有频率和模态的影响.模拟得出的结论与瑞利商和里滋法的计算结论基本相符,从而验证了所提出的瑞利-里滋法解析解的有效性.所给出的解析方法适合任意储箱内液体晃动的模态分析.     

基于液固耦合的圆柱贮箱内液体防晃特性研究

考虑贮箱内液体与防晃板的液固耦合效应,采用商业有限元软件ADINA,分别建立了形状为中竖板、十字竖板、水平环和漏斗式板等4种不同类型防晃挡板的充液贮箱有限元模型.通过模态分析、自由晃动和强迫晃动等数值模拟计算,分别研究了不同类型防晃板对圆柱贮箱内液体晃动固有频率、晃动阻尼、晃动力和晃动力矩等晃动特性的影响.结果表明:由于环形防晃板更能有效的抑制贮箱内液体的晃动效应,同时能降低晃动固有频率,故实际工程中可优先考虑设置环形防晃板,有利于提高充液耦合系统的动力学性能和控制稳定性,对实际工程具有一定的理论参考价值.     

变厚度矩形薄板的屈曲和自由振动问题

本文用单三角级数把单向变厚度矩形板的屈曲和自由振动控制方程化为常微分方程特征值问题，转而采用ＣＤＥ求解器──插值矩阵法获解。本法求解简便、精度高。     

线性矩阵方程的迭代求解方法

在很多问题中会遇到线性矩阵方程的求解问题,如果线性矩阵方程用矩阵直积和矩阵按行或按列进行拉直,用向量表示未知数不仅不方便,而且占用空间较大,因此有必要讨论线性矩阵方程的数值求解方法.本文给出了线性矩阵方程的迭代求解方法,讨论了迭代方法收敛的条件,给出了线性矩阵方程的雅可比迭代方法和方阵乘幂求和方法,用数值例子基于Matlab程序验证了算法的可行性.     

危险品罐车液体晃动等效力学模型构建及验证

推导罐体内液体晃动的弹簧-质量-阻尼等效力学模型,以研究危险品罐车内液体横向晃动问题。首先,用势流理论建立液体自由晃动的运动方程,基于等效力学模型建立给液体施加正弦波横向激励的运动方程,对比两种方法罐体受到的力和力矩,获得固定液体高度、晃动液体高度、固定液体质量和晃动液体质量4个参数值;其次,用线性波理论求解液体晃动的固有频率,得到晃动液体的弹簧刚度;然后,通过实验获得晃动液体的阻尼系数;最后,搭建等比缩小试验台验证模型的准确性和有效性。运用等效模型分析具体算例,结果表明,充液比与横向激励均干扰罐内液体的自由流动。高阶的液体晃动固有频率数值越大,而等效刚度和阻尼系数的阶数越高数值越小;充液比为0.85左右时,晃动质量、等效刚度和阻尼系数均最大;罐体受到横向激励越大,罐内液体晃动越剧烈,且应避免充液比在(0.8,1)的工况运输危险品,以防发生危险事故。     

弹性圆柱壳的振动优化设计

研究了在任意轴对称边界条件下的圆柱壳的自由振动优化设计问题，即寻求圆柱壳的最优厚度分布使自振基频极大化。利用半解析元方法分析轴对称变厚度圆柱壳的自由振动，将求解自振基频归为求解广义特征值方程，使圆柱壳振动优化设计成为极大化最小特征值问题。典型算例表明了本方法的有效性。     

矩阵方程AX-XA=0的求解问题

在系统控制和数值计算方法中,经常遇到矩阵方程的求解问题.本文利用矩阵的直积和矩阵的拉直概念,给出矩阵方程的代数解.     

用试验数据修正混合的阻尼矩阵与刚度矩阵

研究用试验数据修正振动系统的双对称阻尼矩阵和对称次反对称刚度矩阵,利用二次特征值反问题的理论和方法说明了问题的可解性,借助正交基的方法将约束矩阵问题转化为常见的非约束问题,进而对首1的二次特征值反问题进行求解.并讨论了给定任意矩阵的最佳逼近问题,给出问题的最佳逼近解.     

液体贮箱焊接车削方法

专利号:200610116182.4专利权人:上海航天设备制造总厂简介:本发明公开了一种液体贮箱焊接车削方法,具体操作步骤为:(1)液体贮箱瓜瓣焊接;(2)液体贮箱上端面车削;(3)液体贮箱端盖焊接;(4)液体贮箱下端面车削;(5)液体贮箱下端框焊接。由于该液体贮箱焊接车削方法使用了一套组合夹具,其组件可在多道工序中重复使用,因此,夹紧定位的重复精     

正弦激励下矩形容器内液体晃动特性研究

为了获得容器内液体的晃动特性,采用数值模拟方法对正弦激励下矩形容器的晃动过程进行研究.通过用户自定义函数实现速度的加载,给定容器的刚体运动,通过计算结果与实验数据的对比验证数值方法的准确性;探究不同激励对矩形容器壁面受力及液面变化作用机制,揭示外部激励频率、激励幅值对液体晃动特性的影响规律.结果表明:一般情况下,液体晃...     

容器中液体的晃动对其上仪表应力强度的影响

采用有限元程序,根据Housner的液体晃动模型,计算了地震载荷作用下贮液容器上的测量仪表的应力分布情况,并总结了测量仪表上的应力分布规律。贮液容器的液体晃动模型包括了全脉冲模型和晃动模型,通过这两种模型中的计算结果的比较,研究容器中的液体晃动对于测量仪表的影响。计算结果表明,在相同的地震载荷作用下,与贮液容器中装满液体相比较,容器中的液体晃动对于测量仪表强度影响较小。     

三维大幅晃荡的Youngs-VOF法模拟

液货船液体舱室在摇荡运动激励下的大幅晃荡问题日趋成为研究热点.针对液箱三维大幅晃荡问题,考虑较低液体装载水平以及外激励频率为共振频率的条件,采用基于有限差分法的Youngs-VOF自由液面重构方法,计入因气体卷入带来的表面张力影响,实现液舱内合并、气体卷入等液面大变形现象的数值模拟,以及抨击压强的时历预报.大幅晃荡的液面大变形现象数值模拟结果与试验结果对比表明,Youngs-VOF能够实现有效模拟界面运动;同时抨击载荷计算结果与试验结果也较为一致;此外就表面张力对抨击压强的影响进行分析,表明有必要计入表面张力因素.     

Viscous liquid sloshing damping in cylindrical container using a volume of fluid method

Liquid sloshing is a kind of very complicated free surface flow and exists widely in many fields. In order to calculate liquid sloshing damping precisely a volume of fluid method based on finite volume scheme is used to simulate free surface flows in partly filled cylindrical containers. A numerical method is presented to simulate the movement of the free surface flow, in which a piecewise linear interface construction scheme and an unsplit Lagrangian advection scheme instead of Eulerian advection scheme are used. The damping performance of liquid sloshing in cylindrical containers under fundamental sloshing mode is investigated. There are four factors determining the surface-wave damping: free surface, boundary-layer, interior fluid and contact line. In order to study different contributions from these four factors to whole damping, several examples are simulated. No-slip and slip wall boundary conditions on both side wall and bottom wall of the cylindrical containers are studied to compare with the published results obtained by solving Stokes equations. In the present method the first three main factors can be considered. The simulation results show that the boundary-layer damping contribution increases while the interior fluid damping contribution decreases with increase of Reynolds number. Supported by the National Natural Science Foundation of China (Grant No. 10532010)     

Characteristic analysis of liquid forced nonlinear sloshing under low-gravity

Under low gravity,the Lagrange equations in the form of volume integration of pressure of nonlinear liquid sloshing were built by variational principle. Based on this,the analytical solution of nonlinear liquid sloshing in pitching tank could be investigated. Then the velocity potential function was expanded in series by wave height function at the free surface so that the nonlinear equations with kinematics and dynamics free surface boundary conditions were derived. Finally,these nonlinear equations were investigated analytically by the multiple scales method. The result indicates that the system's amplitude-frequency response changes from ‘soft-spring’ to ‘hard-spring’ in the planar motion with the decreasing of the Bond number,while it changes from ‘hard-spring’ to ‘soft-spring’ in the rotary motion.     

液舱内液体晃荡的SPH模型

自由液面的存在使液体晃荡问题具有很强的非线性和随机性.针对中等液位、高液位和在液舱底部加设防荡隔板情况下的液体晃荡问题,依据光滑粒子流体动力学理论,建立了液舱内液体晃荡模型.首先模拟了中等液位和高液位下的液体晃荡,将计算结果分别与线性复合叠加理论解做比较,其结果吻合较好,验证了所建模型的合理性.然后,模拟了在液舱底部加设防荡隔板时的液体晃荡,提出了防荡隔板处粒子分区搜索的边界处理方法.当外激励振幅A=0.025 m时,加设防荡隔板后液面晃荡最大与最小幅值较无隔板时分别减小33.3%和30.6%,当外激励振幅A=0.150 m时,其相应幅值分别减小73.3%和76.2%,说明在相同的外激励作用下适当地加设防荡隔板对减小液体晃荡幅值起到一定作用.     

Dynamic simulation of hydrodynamic model of drum level wave action and sloshing

In order to build the model of the drum level wave action and sloshing, based on the method of modularization modeling, the hydrodynamic model of drum level wave action and sloshing was developed, and dynamic simulation researches were carried out based on the model. The results indicate that both drum level and drum length have functional relations with period of drum level wave action and sloshing. When the drum level decreases or drum length increases, the period of drum level wave action and sloshing increases, density of liquid and number of sub-module division have little influence on the period of drum level wave action and sloshing. The model was validated by the analytical solution theory of liquid’s wave action and sloshing in cuboid container, and the 3D graphics of drum level wave action and sloshing was also obtained. The model can dynamically reflect the rules of wave action and sloshing of water in the container exactly.     

Three-dimensional forward modeling for magnetotelluric sounding by finite element method

A finite element algorithm combined with divergence condition was presented for computing three-dimensional(3D) magnetotelluric forward modeling. The finite element equation of three-dimensional magnetotelluric forward modeling was derived from Maxwell’s equations using general variation principle. The divergence condition was added forcedly to the electric field boundary value problem, which made the solution correct. The system of equation of the finite element algorithm was a large sparse, banded, symmetric, ill-conditioned, non-Hermitian complex matrix equation, which can be solved using the Bi-CGSTAB method. In order to prove correctness of the three-dimensional magnetotelluric forward algorithm, the computed results and analytic results of one-dimensional geo-electrical model were compared. In addition, the three-dimensional magnetotelluric forward algorithm is given a further evaluation by computing COMMEMI model. The forward modeling results show that the algorithm is very efficient, and it has a lot of advantages, such as the high precision, the canonical process of solving problem, meeting the internal boundary condition automatically and adapting to all kinds of distribution of multi-substances. Foundation item: Project(60672042) supported by the National Natural Science Foundation of China     

Preshaping法在液面振动控制中的应用

针对液体运送过程中的液面振动问题,利用拉格朗日法推导出液体振动数学模型,讨论Preshaping法的应用.通过仿真得到以下结论：只有两个加速度输入量时间间隔及幅值满足某些要求,才能使匀速运动时的液面振动为零;否则就无法实现对液面振动的控制.