Effects of Perforated Baffle on Reducing Sloshing in Rectangular Tank:Experimental and Numerical Study

A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this experimental rig to estimate the free surface fluctuation and pressure distribution by changing external excitation frequency of the shaking table. An in-house CFD code is also used in this study to simulate the liquid sloshing in three-dimensional （3D） rectangular tank with perforated baffle. Good agreements of free surface elevation and pressure between the numerical results and the experimental data are obtained and presented. Spectral analysis of the time history of free surface elevation is conducted by using the fast Fourier transformation.

Optimization of Baffled Rectangular and Prismatic Storage Tank Against the Sloshing Phenomenon

The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using Open Foam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon.The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of h_b/h_w=0.5-0.75 in the present study(where h_b and h_w are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with R_A= 0.9-1.0(where R_A=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of h_b can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases.However, as the normalized motion amplitude parameter, a/L(The parameter a is the motion amplitude), exceeds0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.

Numerical Simulation of Sloshing in Rectangular Storage Tank Using Coupled FEM-BEM

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.

Dynamic response of liquid-filled rectangular tank with elastic appendages under pitching excitation

Nonlinear dynamics of liquid-filled rectangular tank with elastic appendages are studied. Based on the assumption of ideal fluid, the coupling dynamic equations of rigid tank, elastic appendages and liquid fuel are derived using H-O principle. In the case of pitch excitation, the modified potential function and wave height function are introduced to describe the moving boundary of fluid, then Galerkin＇s method is used to discretize the dynamic equations into ordinary differential equations. The natural frequencics of the coupling system are formulated in liquid depth, the length of the tank, etc. The formulae are confirmed by numerical simulations, which also show that the effects of liquid and elastic appendages on the attitude angular of rigid.

Optimization of a Dual-Baffled Rectangular Tank Against the Sloshing Phenomenon

A dual-baffled rectangular tank with different configurations is proposed to reduce the sloshing effect,and design optimization is conducted through numerical simulations with open-source software,namely OpenFOAM,based on the computational fluid dynamic model.A series of physical experiments in the dual-baffled rectangular tank is performed for model validation and design optimization with the measured water surface elevation distributions along the tank.The optimization uses the calculated maximum horizontal force exerted on the tank and entropy generation(EG)as the criterion.Results show that the dual-baffle configuration positioned at the tank center is more effective in reducing the sloshing than that of the single baffle when the relative baffle height and initial water depth ratio(Hb/Hw,where Hb and Hw represent baffle height and static water depth,respectively)are larger than 0.5.However,such an effect then diminishes when the ratio is larger than 0.75.The effect of the dual-baffle configuration on the sway motion under the condition of different motion amplitudes and frequencies is also evaluated.The results show that the reduction in the maximum horizontal force is almost the same for dual-and single-baffled configurations and reaches the minimum when the sway motion amplitude is near 0.03 m.The dual-baffled configuration for the angular frequency of the sway motion is more effective than the single-baffled in reducing the sloshing at the low angular frequencies but is only less effective at high angular frequencies.Furthermore,the optimal baffle inclination angle is 85°when the inclined straight and curved baffles are used,and curved baffles can successfully decrease the horizontal force exerted on the tank and EG.

Intelligent Layout Method of the Powerhouse for Tank & Armored Vehicles Based on 3-Dimensional Rectangular Packing Theory

Probes into a new and effective method in arranging the powerhouses of tank & armored vehicles. Theory and method of 3-dimensional rectangular packing are adapted to arrange effectively almost all the systems and components in the powerhouse of the vehicle, thus the study can be regarded as an attempt for the theory's engineering applications in the field of tank & armored vehicle design. It is proved that most parts of the solutions attained are reasonable, and some of the solutions are innovative.

Application of Rectangular Integral to Numerical Simulation of Hydraulic Transients in Complex Pipeline Systems

The hydraulic oscillation of surge tank was analyzed through numerical simulation.A rectangular integral scheme was established in order to improve the numerical model.According to the boundary control equation of surge tank, the rectangular integral scheme omits the second-order infinitesimal and simplifies the solving process.An example was provided to illustrate the rectangular integral scheme, which is compared with the traditional trapezoid integral scheme.Appropriate numerical solutions were gained through the new scheme.Results show that the rectangular integral scheme is more convenient than the trapezoid integral one, and it can be applied to the numerical simulation of various surge tanks in complex pipeline systems.

A Comparative Study on Hydrodynamic Performance of Double Deflector Rectangular Cambered Otter Board

In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.

波纹夹层结构增强的新型罐式集装箱及其设计方法

罐式集装箱因安全性高、承载量大、性价比高、运输灵活以及可以实现多种运输方式快速切换等特点,成为液体货物点对点运输的主要装备。近年来,大容量、高承载能力成为罐式集装箱发展的主流方向。提出了一种波纹夹层结构增强的新型矩形罐式集装箱,并建立了新型罐式集装箱罐体结构的理论设计方法。应用该方法设计了承载能力为1 MPa的新型罐式集装箱罐体,并将设计结果与有限元仿真计算结果进行对比。研究结果表明,相较于传统罐式集装箱,新型罐式集装箱的容量效率提升了17.2%;理论设计方法计算的应力分布特征与有限元计算结果一致,最大误差为6.21%,该理论设计方法可以满足工程需要。理论设计方法可以对任意正交各向异性夹层结构增强的新型罐式集装箱罐体进行设计,具有较高的可移植性。

防回油冲击液压油箱结构改进

液压系统有向集成化、轻量化发展的趋势。液压油箱小型化,会导致油液回油时产生回油冲击,造成油箱内部发生卷气现象,使油液中气体污染物含量增高,影响油液品质,甚至在油箱透气帽处发生油液飞溅现象,影响系统密封性。针对油箱的使用工况,分析仿真模型的适用条件,建立AGV小车油箱的有限元仿真模型,分析初始情况和结构改进后油箱内部的油液运动状态。对AGV小车进行验证性实验,对比数值模拟结果,回油液面状态相近,仿真模型计算效果良好,基于仿真模型得到能够减轻该油箱回油冲击的油箱结构改进方法。

污水处理矩形沉淀池和斜管沉淀池对比试验

为探究不同形式的沉淀池对污水处理效率的影响,采用5.0 m^(3)/h的中试装置,以改良AAO工艺为主要生化处理单元,分别设置矩形沉淀池及斜管沉淀池作为二沉池进行试验,通过优化污泥回流方式、溶解氧及污泥浓度控制,在探究改良AAO工艺最佳运行工况的基础上,在不同水温下对两种沉淀池出水水质及运行稳定性进行对比分析。结果表明,斜管沉淀池的启动时间小于矩形沉淀池,能有效应对130%的进水负荷率,出水SS的质量浓度稳定达到10 mg/L以下并节省25%的占地面积,在低温下仍能保证较好的固液分离效果,但需要配置相应的反冲洗设备定期冲洗,提高运行稳定性。

变壁厚矩形水池有限元分析及经济性研究

对于平面尺寸很大、池壁为竖向单向受力的钢筋混凝土矩形水池,工程设计一般对池壁采用变壁厚以达到节约造价的目的。依据工程实例通过对多个变壁厚矩形水池模型进行有限元分析,总结变壁厚池壁的内力特点。对变壁厚矩形水池进行经济性分析,总结矩形水池通过采用变壁厚降低造价的使用条件。

二维矩形水槽晃荡过程的SPH方法模拟

新型LNG船的液仓内液体晃荡涉及非线性自由表面大变形运动。针对容器的运动所激发的内部流体的强迫晃荡问题,该文运用光滑质点水动力学(SPH)方法对二维矩形水槽的纵荡过程和纵摇过程进行了数值模拟。纵荡过程中边界处的自由液面高度的时间历程曲线与前人的结果相比符合较好,结果还显示了当激励频率接近容器一阶固有频率时出现了对容器上边界的砰击和自由水面的破碎现象,并分析了砰击作用对计算的影响;同时考虑纵荡和纵摇激励时,模拟表明当相位相同时波面的运动幅度最小,而相位差为180度时波面的运动幅度最大,并且其综合效果是非线性的。

平流式沉淀池数值模拟分析

利用前人已建立的二维沉淀池数学模型计算沉淀池内水流的流场和过流曲线,并进行验证,结果表明,该模型能够很好地模拟沉淀池中水流的流动以及示踪剂在池内的流动过程.利用该模型,分别计算平流式沉淀池在不同挡板位置、进水口流速和沉淀池长高比下的水流流场、悬浮物的浓度场,并用示踪剂分别计算其过流曲线.分析比较挡板位置、进水口流速、沉淀池长高比等对沉淀池运行效果的影响,并依此确定沉淀池合理的挡板位置、长高比和进水口流速.

PHOENICS数值模拟平流式二沉池流场

本文利用CFD商用软件PHOENICS,模拟平流式二沉池内的流线和速度分布。结果表明池内的实际流场与理想沉淀池之间存在着很大的差异,特别是在挡板前后存在着两个极为明显的涡流区,影响二沉池的沉淀效果。并且还考虑了不同的回流比对二沉池流态产生的影响。

平流二次沉淀池两相流二维数值模拟

为了模拟平流二次沉淀池存在密度差异时的流动,选取两相流混合模型和RNGk-ε两方程紊流模型对平流二沉池流动进行了数值模拟,并将模拟结果同埃施(Esch R E)提出的明流弗汝德数理论及二沉池实际运行状态进行了比较。结果表明,数值模拟结果与明流临界弗汝德数理论吻合,同二沉池实际运行状态的符合性也较好,验证了该模型模拟存在密度差异的混合液的流动的有效性。

矩形容器中流体晃动等效模型的建议公式

根据矩形容器中流体晃动等效模型的精确解,采用非线性拟合算法,给出了等效模型中脉冲质量及其位置的拟合公式,本文给出的拟合公式比精确解简单、且计算精度远高于Housner公式,可以作为精确解良好的替代公式。建议采用本文公式(3)～(8)作为矩形容器内流体晃动等效模型的计算表达式。

平流式沉淀池水流三维CFD模拟

建立了平流式沉淀池水流的三维两相流模型,在动量方程中考虑了相间界面力的作用,以及悬浮物体积分数和两相间密度差的影响;应用计算流体力学软件STAR-CD对模型进行求解.结果表明,沉淀池内宽度方向速度分布是非均匀的;进水口下方和污泥斗上方存在回流区;进水区水流湍动能较大,而沉淀区内很小;同时比较了出水口处是否设置挡板以及挡板深度对流场的影响.以Imam的实验结果进行验证,流场模拟值与实验值吻合很好.

基于SPH方法的二维矩形舱液体晃荡数值研究

储液舱内液体晃荡是当外激激励频率与容器内部液体自由液面的固有频率接近时,液体产生的剧烈共振运动.采用光滑粒子流体动力学(SPH)方法,在二维矩形舱低载液率横荡和横摇激励下,自由液面共振频率附近4个激励频率处开展数值研究.对比数值和对应实验中全局自由液面波形和冲击压力时程发现,SPH方法可以很好地模拟液体晃荡时的波形,如水跃、破碎波等自由液面的大变形运动.此外,该方法可用于模拟和评估非共振区域晃荡荷载的特性.建议采用两相流来模拟共振频率下液体剧烈的晃荡运动.

带弹性附件充液矩形贮箱俯仰运动动态响应

首先建立了俯仰运动矩形贮箱刚-液-弹耦合系统在外力矩作用下的耦合动力学模型,给出满足边界条件的速度势函数和液面波高的级数表达式,采用伽辽金法离散,将动力学模型转化为常微分方程组,得到刚-液-弹耦合系统的固有频率,给出简单的近似表达式,分析了转动中心距静液面不同位置时刚-液-弹耦合系统各阶固有频率的变化规律,系统转动中心距静液面较近时,耦合后液体反对称模态和刚体的固有频率对比耦合前减小,较远时则增大,最后进行数值验证,比较分析了液体和弹性体对刚体姿态的影响.