A numerical study of the effects of the vertical baffle on liquid sloshing in two-dimensional rectangular tank

The liquid sloshing in a moving partially filled rectangular tank with a vertical baffle is investigated. A numerical algorithm based on the volume of fluid (VOF) technique is used to study the nonlinear behavior of liquid sloshing. The numerical model solves the complete Navier–Stokes equations in primitive variables by using of finite difference approximations with the moving coordinate system. The ratio of baffle height to the initial liquid depth has been changed in the range of 0≤h_B/h≤1.2. The critical baffle height to reach the roof of the tank and the baffle height beyond the liquid does not get over the baffle anymore have been investigated. The vortex originated by the flow separation from the baffle tip became weaker with increasing the baffle height. In order to assess the accuracy of the method used, some results with baffle height are compared with the experimental results. Comparisons show good agreement for slosh loads in the cases investigated. The free surface elevation and the time variations of pressures have been also presented.     

Transient sloshing in half-full horizontal elliptical tanks under lateral excitation

A semi-analytical mathematical model is developed to study the transient liquid sloshing characteristics in half-full horizontal cylindrical containers of elliptical cross section subjected to arbitrary lateral external acceleration. The problem solution is achieved by employing the linear potential theory in conjunction with conformal mapping, resulting in linear systems of ordinary differential equations which are truncated and then solved numerically by implementing Laplace transform technique followed by Durbin's numerical inversion scheme. A ramp-step function is used to simulate the lateral acceleration excitation during an idealized turning maneuver. The effects of tank aspect ratio, excitation input time, and baffle configuration on the resultant sloshing characteristics are examined. Limiting cases are considered and good agreements with available analytic and numerical solutions as well as experimental data are obtained.     

The sloshing of stratified liquid in a two-dimensional rectangular tank

The sloshing of inviscid liquid of stratified density in a rectangular tank is analyzed.As the flow is no longer irrotional,the governing equation is found to be quite different from the Laplace equation used for the liquid of constant density.In particular it contains terms of mixed temporal and spatial derivatives.The problem is solved based on the variable separation method and Laplace transform for the constant Vaisala-Brunt frequency.It is found that the stratification of density may have small effects...     

用于石油罐的光纤传感液位测量系统

许多石油化工企业的油品储存罐仍使用着靠人工读数的浮子式液位测量装置，其工作效率低、误差大，而且无法实现自动化控制和管理。针对这种情况，采用先进的光纤传感技术在人工浮子液位计的基础上研制了一种新型的液位测量系统。该系统利用力平衡原理测量液位，利用光纤传感器探测和传输信号，采用自制的光码盘实现光信号的调节。该系统的现场测试结果表明，系统在测量范围为0～1000mm时，测量误差≤±6mm、相对误差＜2％。现场应用表明，该系统的各项性能指标符合生产要求，并且运行稳定，性能可靠。     

Low-gravity liquid nonlinear sloshing analysis in a tank under pitching excitation

Under pitch excitation, the sloshing of liquid in circular cylindrical tank includes planar motion, rotary motion and rotary motion inside planar motion. The boundaries between stable motion and unstable motion depend on the radius of the tank, the liquid height, the gravitational intension, the surface tensor and the sloshing damping. In this article, the differential equations of nonlinear sloshing are built first. And by variational principle, the Lagrange function of liquid pressure is constructed in volume integration form. Then the velocity potential function is expanded in series by wave height function at the free surface. The nonlinear equations with kinematics and dynamics free surface boundary conditions through variation are derived. At last, these equations are solved by multiple-scales method. The influence of Bond number on the global stable response of nonlinear liquid sloshing in circular cylinder tank is analyzed in detail. The result indicates that the system's amplitude–frequency response changes from a ‘soft-spring’ to a ‘hard-spring’ in the planar motion with the decreasing of the Bond number, while it changes from a ‘hard-spring’ to a ‘soft-spring’ in the rotary motion. At the same time, jump, lag and other nonlinear phenomena of liquid sloshing are discovered.     

Parameter identification of new bidirectional tuned liquid column and sloshing dampers

A tuned liquid column and sloshing damper (TLCSD) is introduced in this study. It shows dynamic behavior of both tuned liquid column damper (TLCD) and tuned liquid damper (TLD) in the direction of two axes perpendicular with each other. As a preliminary study for applying the TLCSD to bidirectional control of building structures, one of objectives of this study is to derive analytical dynamics to investigate coupled effects due to TLCD and TLD. Another objective is to investigate the effect of coupled control force due to TLCD and TLD on the dynamic characteristic of the TLCSD based on analytical dynamics. Shaking table test is undertaken to experimentally grasp dynamic characteristics of TLCSD under white noise excitation with various amplitude levels. Its dynamic characteristics are expressed by the transfer function from the shaking table acceleration to the control force generated from a TLCSD. The analytical dynamics of TLCSD is derived from the equivalent linearized TMD model. The coupled dynamics of TLCSD is expressed in terms of those of both TLCD and TLD. Finally, the key parameters of both TLCD and TLD are identified based on the coupled dynamics proposed in this study, which include the mass ratio of horizontal liquid column to total liquid for a TLCD, and the participation factor of the fundamental liquid sloshing for a TLD and damping ratio for both cases.     

氢原子传输及负氢离子产生全三维数值模拟研究

理论分析了负氢离子源中中性粒子传输特性及引出电极表面产生负氢离子(H^-)的物理过程, 研究了引出孔传输率对氢原子传输的影响,深入剖析了氢原子与不同属性导体壁碰撞以及碰撞后反射的物理情景.基于CHIPIC软件平台,成功研制了全三维 Particle-in-cell with Monte Carlo Collision 氢原子传输及负氢离子产生物理过程的模拟算法,并采用JAEA 10A负氢离子源进行模拟验证.模拟达到稳态后,氢原子平均能量约为0.57 eV, 且H原子呈现+Y漂移,当非均匀氢原子束轰击引出壁时,导致产生的负氢离子空间分布不均匀. 这些模拟结果都与文献符合,验证了算法的可靠性.     

气体电离的全三维电磁粒子模拟/蒙特卡罗数值研究

深入研究电子束对中性气体电离的物理机理,在粒子模拟(PIC)软件CHIPIC的基础上,设计了蒙特卡罗(MCC)电离碰撞模块,并对电子与离子同时进行了跟踪,成功研制了全三维电磁PIC/MCC代码.通过该软件对填充氦气相对论返波管的模拟,对全三维电磁PIC/MCC代码进行验证.模拟结果显示:填充气体可以中和空间电荷限制效应,有效提高电流大小;填充适量的气体可提高功率峰值,扩展脉冲宽度;过量的气体则会缩短脉冲宽度、降低峰值功率.     

低温储罐充液后夹层压力变化规律

低温储罐在充液后内罐因温度下降而冷缩,夹层空间增大,同时夹层温度也将下降,综合作用使夹层真空度升高及绝对压力下降,这对低温容器绝热是有利的。为了计算充液后夹层压力的大小,研究了低温容器充液后内罐冷缩及夹层温度变化情况,给出了夹层压力的计算公式。实例计算表明充液后夹层压力下降显著。     

Voltage calculations for annular tanks partly-filled with charged liquid

A Bessel function expression is developed for the voltages produced when annular tanks (vertical axis cylindrical tanks with central conductors) are filled with liquids of uniform charge density. The expression is used to calculate the maximum surface voltage and this is compared with the maximum voltage predicted for tanks without a central conductor. Previous estimates of the percentage voltage reduction produced by a central conductor during tank filling have indicated a reduction of about 42% for practical tank dimensions. The new results, which are obtained with a more realistic model geometry, suggest a reduction of only about 29%.     

Linear and nonlinear 2D finite element analysis of sloshing modes and pressures in rectangular tanks subject to horizontal harmonic motions

The influence of nonlinear wave theory on the sloshing natural periods and their modal pressure distributions are investigated for rectangular tanks under the assumption of two-dimensional behavior. Natural periods and mode shapes are computed and compared for both linear wave theory (LWT) and nonlinear wave theory (NLWT) models, using the finite element package ABAQUS. Linear wave theory is implemented in an acoustic model, whereas a plane strain problem with large displacements is used in NLWT. Pressure distributions acting on the tank walls are obtained for the first three sloshing modes using both linear and nonlinear wave theory. It is found that the nonlinearity does not have significant effects on the natural sloshing periods. For the sloshing pressures on the tank walls, different distributions were found using linear and nonlinear wave theory models. However, in all cases studied, the linear wave theory conservatively estimated the magnitude of the pressure distribution, whereas larger pressures resultant heights were obtained when using the nonlinear theory. It is concluded that the nonlinearity of the surface wave does not have major effects in the pressure distribution on the walls for rectangular tanks.     

Anyonic loops in three-dimensional spin liquid and chiral spin liquid

We established a large class of exactly soluble spin liquids and chiral spin liquids on three-dimensional helix lattices by introducing Kitaev-type's spin coupling. In the chiral spin liquids, exact stable ground states with spontaneous breaking of the time reversal symmetry are found. The fractionalized loop excitations in both the spin and chiral spin liquids obey non-Abelian statistics. We characterize this kind of statistics by non-Abelian Berry phase and quantum algebra relation. The topological correlation of loops is independent of local order parameter and it measures the intrinsic global quantum entanglement of degenerate ground states.     

A three-dimensional Eulerian method for the numerical simulation of high-velocity impact problems

In the present paper, a three-dimensional （3D） Eulerian technique for the 3D numerical simulation of high-velocity impact problems is proposed. In the Eulerian framework, a complete 3D conservation element and solution element scheme for conservative hyperbolic governing equations with source terms is given. A modified ghost fluid method is proposed for the treatment of the boundary conditions. Numerical simulations of the Taylor bar problem and the ricochet phenomenon of a sphere impacting a plate target at an angle of 60~ are carried out. The numerical results are in good agreement with the corresponding experimental observations. It is proved that our computational technique is feasible for analyzing 3D high-velocity impact problems.     

Smouldering in fixed beds of oil shale grains. A three-dimensional microscale numerical model

A three-dimensional, microscale numerical model for the simulation of smouldering in fixed beds of solid fuels is presented. It solves the local governing equations, and therefore explicitly accounts for the coupling of the transport and reaction mechanisms on the microscopic scale. This article describes the conceptual and numerical apparatus and provides illustrative examples of calculations. Extensive applications will be presented in two companion papers.     

A theoretical and numerical resolution of an acoustic multiple scattering problem in three-dimensional case

This paper develops an analytical solution for sound, electromagnetic or any other wave propagation described by the Helmholtz equation in three-dimensional case. First, a theoretical investigation based on multipole expansion method and spherical wave functions was established, through which we show that the resolution of the problem is reduced to solving an infinite, complex and large linear system. Second, we explain how to suitably truncate the last infinite dimensional system to get an accurate stable and fast numerical solution of the problem. Then, we evaluate numerically the theoretical solution of scattering problem by multiple ideal rigid spheres. Finally, we made a numerical study to present the “Head related transfer function” with respect to different physical and geometrical parameters of the problem.     

A comparative study of the PIV and LDV measurements on a self-induced sloshing flow

Particle Imaging Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) measurements on a self-induced sloshing flow in a rectangular tank had been conducted in the present study. The PIV measurement result was compared with LDV measurement result quantitatively in order to evaluate the accuracy level of the PIV measurement. The comparison results show that the PIV and LDV measurement results agree with each other well in general for both mean velocity and fluctuations of the velocity components. The average disagreement level of the mean velocity between PIV and LDV measurement results was found to be within 3% of the target velocity for the PIV system parameter selection. Bigger disagreements between the PIV and LDV measurement results were found to concentrate at high shear regions. The spatial resolution and temporal resolution differences of the PIV and LDV measurements and the limited frames of the PIV instantaneous results were suggested to be the main reasons for the disagreement.     

Deformation of three-dimensional monodisperse liquid foams

We have used a new experimental method to produce and deform three-dimensional monodisperse foams. Uniaxial deformation causes transitions in the foam in which the number of close-packed bubble layers perpendicular to the direction of elongation changes by one. We predict the critical strains at which such transitions occur by calculating the foam energy as a function of strain. These calculations are approximate with simplifying assumptions regarding the geometry of the bubbles. The foam deforms by nucleation and subsequent glide of dislocations which consist, in one configuration, of pairs of 12- and 16-faced cells along a close-packed direction of the foam. We describe these line defects and identify the topological transformations that occur in glide. These are neighbour switchings associated with a 4-sided face that rotates changing the adjacencies of the cells. These T4 operations occur in an avalanche and cause movement of the dislocation while preserving its identity. Received 16 July 2001