Review on the Progress and Issues in Liquid Tank Sloshing of Ships

With the development of large liquid cargo ships,liquid tank sloshing has gradually become a hot research topic in the area of shipping and ocean Engineering.Liquid tank sloshing,characterized by strong nonlinearity and randomness,not only affects the stability of the ship but also generates a huge impact force on the wall of the tank.To further investigate liquid tank sloshing,a comprehensive review is given on the research process of the most focused subjects of liquid sloshing.Summarizing the existing research will help to identify issues in the current field and provide useful references.The methods for investigating sloshing,the research progress and the situations worldwide are discussed.The advantages and defects of experiments and numerical simulations are also explored.The problems which need to be explored in the future are subsequently proposed.

Calculation of the Added Mass of a Liquid Tank's Bulkheads

The added mass coefficient and the water level index formulas for the same-phase and anti-phase vibration of rectangular liquid tanks' bulkheads were derived based on dry mode theory. Three fluid-structure interaction numerical methods including Fluid FEM and Fluid BEM were used in this case. The comparison of numerical and theoretical results by the present method shows that ANSYS/Fluid80 is more credible, the NASTRAN/Virtual Mass Method is more suitable for engineering calculations and results of the same-phase vibration by the present method is more accurate.

Improving the seismic performance of base-isolated liquid storage tanks with supplemental linear viscous dampers

Large tanks are extensively used for storing water,petrochemicals and fuels.Since they are often cited in earthquake-prone areas,the safe and continuous operation of these important structures must be ensured even when severe earthquakes occur,since their failure could have devastating financial and socio-environmental consequences.Base-isolation has been widely adopted for the efficient seismic protection of such critical facilities.However,base-isolated tanks can be located relatively close to active faults that generate strong excitations with special characteristics.Consequently,viscous dampers can be incorporated into the isolation system to reduce excessive displacement demands and to avoid overconservative isolator design.Nonetheless,only a few studies have focused on the investigation of seismic response of base-isolated liquid storage tanks in conjunction with supplemental viscous dampers.Therefore,the impact of the addition of supplemental linear viscous dampers on the seismic performance of tanks isolated by single friction pendulum devices is investigated herein.Four levels of supplemental damping are assessed and compared with respect to isolators′displacement capacity and accelerations that are transferred to the tanks.

Numerical Simulation of Gas-Liquid Flow in a Stirred Tank with a Rushton Impeller

The gas-liquid flow field in a stirred tank with a Rushton disk turbine,including the impeller region,was numerically simulated using the improved inner-outer iterative procedure.The characteristic features of the strirred tank,such as gas cavity and accumulation of gas at the two sides of wall baffles,can be captured by the simulation.The simulated results agree well with available experimental data.Since the improved inner-outer iterative algorithm demands no empirical formula and experimental data for the impeller region,and the approach seems generally applicable for simulating gas-liquid stirred tanks.

Numerical Study of Solid-Liquid Two-Phase Flow in StirredTanks with Rushton Impeller(Ⅱ) Prediction of Critical Impeller Speed

Three-dimensional solid-liquid flow is mathematically formulated by means of the 'two-fluid' approach and the two-phase k-ε-AP turbulence model. The turbulent fluctuation correlations appearing in the Reynolds time averaged governing equations are fully incorporated. The solid-liquid flow field and solid concentration distribution in baffled stirred tanks with a standard Rushton impeller are numerically simulated using an improved 'inner-outer'iterative procedure. The flow pattern is identified via the velocity vector plots and a recirculation loop with higher solid concentration is observed in the central vicinity beneath the impeller. Comparison of the simulation with experimental data on the mean velocities and the turbulence quantities of the solid phase is made and quite reasonable agreement is obtained except for the impeller swept volume. The counterpart of liquid phase is presented as well.The predicted solid concentration distribution for three experimental cases with the average solid concentration up to 20% is also found to agree reasonably with the experimental results published in the literature.

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.

Numerical Study of Solid-Liquid Two-Phase Flow in Stirred Tanks with Rushton Impeller (Ⅰ) Formulation and Simulation of Flow Field

The critical impeller speed, NJs, for complete suspension of solid particles in the agitated solid-liquid two-phase system in baffled stirred tanks with a standard Rushton impeller is predicted using the computational procedure proposed in Part I. Three different numerical criteria are tested for determining the critical solid suspension. The predicted NJS is compared with those obtained from several empirical correlations. It is suggested the most reasonable criterion for determining the complete suspension of solid particles is the positive sign of simulated axial velocity of solid phase at the location where the solid particles are most difficult to be suspended.

An Improved Spectral Analysis Method for Fatigue Damage Assessment of Details in Liquid Cargo Tanks

Errors will be caused in calculating the fatigue damages of details in liquid cargo tanks by using the traditional spectral analysis method which is based on linear system, for the nonlinear relationship between the dynamic stress and the ship acceleration. An improved spectral analysis method for the assessment of the fatigue damage in detail of a liquid cargo tank is proposed in this paper. Based on assumptions that the wave process can be simulated by summing the sinusoidal waves in different frequencies and the stress process can be simulated by summing the stress processes induced by these sinusoidal waves, the stress power spectral density(PSD) is calculated by expanding the stress processes induced by the sinusoidal waves into Fourier series and adding the amplitudes of each harmonic component with the same frequency. This analysis method can take the nonlinear relationship into consideration and the fatigue damage is then calculated based on the PSD of stress. Take an independent tank in an LNG carrier for example, the accuracy of the improved spectral analysis method is proved much better than that of the traditional spectral analysis method by comparing the calculated damage results with the results calculated by the time domain method. The proposed spectral analysis method is more accurate in calculating the fatigue damages in detail of ship liquid cargo tanks.

UNITIVE ANALYSIS SCHEMES ON PROBLEMS OF MULTIPLE MOVING BOUNDARIES WITH 3-D LIQUID-SOLID MULTIPLE NONLINEAR COUPLING FOR UPLIFT OF ANCHOREDLIQUID STORAGE TANKS

In the paper, 3-D analysis method with unitive schemes is set up, which is used to resolve the uplift with multiple moving boundaries and multiple nonlinear coupling for anchored liquid storage tanks. hi it, an algorithm of quasi-harmonious finite elements for arbitrary quadrilateral of thin plates and shells is built up to analyze the multiple coupling problems of general thin plates and shells structures with three dimensions, the complementary equations for analyzing uplifting moving boundary problems are deduced. The axial symmetry and presumption of beam type mode are not used. In it, an algorithm is put forward for analyzing the Navier-Stokes problems of unsteady, three-dimensional, and viscous liquid with sloshing of moving boundary surfaces in large amplitude under ALE frame by scheme of time-split-steps to which linear potential theory is not applied. The algorithms can be used to analyze the solid-liquid multiple nonlinear coupling problems with 3-D moving boundary with friction in multiple places.

Experimental study of power consumption, local characteristics distributions and homogenization energy in gas–liquid stirred tank reactors

In this paper, the power consumption, the vertical local void fraction and the local gas–liquid interfacial area are investigated in the aerated stirred tank reactors(STRs) equipped with a rigid-flexible impeller. Meanwhile, the regressive correlation based on power consumption and interfacial area is proposed. Then a novel homogenization energy(HE = RSDPtm) expression based on power consumption and local interfacial area is redefined and used to indicate the mixing efficiency. The optimal operating mode is selected based on the change of the HE value. This paper can provide research ideas for structural optimization of stirred reactors.

FREE BENDING VIBRATION OF ANNULAR CYLINDRICAL TANK PARTIALLY FILLED WITH LIQUID IN THE CONSIDERATION OF SURFACE WAVE

This paper studies the problem of free bending vibration of annular cylindricaltank partially filled with liquid in the consideration of surface wave.The exactformulae of the mode shape functions and frequencies are deduced.Results can beobtained by means of computer.The analysis shows that the effect of liquid on vibration of annular cylindrical tank is equivalent to different generalized distributivemasses attached to inner and outer cylinders respectively.

Comparison of base-isolated liquid storage tank models under bi-directional earthquakes

Seismic response of ground supported baseisolated liquid storage tanks are evaluated under bi-directional earthquakes. The base-isolated liquid storage tanks are modeled using mechanical analogs with two and three lumped masses (Model 1 and Model 2). Two types of isolation systems, such as sliding system and elastomeric system, are considered for the present study. The isolation systems are modeled using Wen’s equation for hysteretic isolation systems. Response of base-isolated liquid storage tanks, evaluated through two different modeling approaches, is compared. Both the models predict similar sloshing displacement. The effect of interaction between the mutually perpendicular seismic responses of the isolator is investigated for both the models. It is observed that interaction affects the peak seismic response of the base-isolated liquid storage tanks significantly, under the bi-directional earthquake components.

Bifurcation of elastic tank-liquid coupled sloshing system

The nonlinear equations of an elastic tank-liquid coupling system subjected to the external excitation are established.By means of the multi-scale method and the singularity theory,the bifurcation behaviors of the system are investigated and analyzed.The various nonlinear dynamical behaviors of the coupling system are obtained,which can further explain the relationship between the physical parameters and the bifurcation solutions.The results provide a theoretical basis to the realization of the parameter optimal control.

SOLID-LIQUID SUSPENSION SYSTEM IN AGITATED TANK WITH DRAFT TUBE

Solid-liquid suspension in an agitated tank with a draft tube was investigated witha newly developed infrared turbidimeter for measuring solid concentration.The diameter of theflared inlet transition tube and the distance from the inlet to the tank bottom are two importantparameters for draft tube design The NAX-4 impeller,developed in this study,is characterized byits high flow efficiency and low power consumption.Some modifications are made to the Bald′smodel by considering the effects of solid concentration and fluid viscosity on the critical speed forcomplete off-bottom suspension.The modified equation fits the experimental data satisfactority andcan be used in scale-up

两种直升机多舱油箱惰化系统代偿损失比较

针对某型直升机多舱油箱,设计了冷却空气控温和燃油热沉控温的2种多舱油箱惰化系统。基于AMESim平台搭建了这2种系统模型,研究了这2种系统的控温效果和各舱油箱参数变化规律,并且引入代偿损失指标对这2种系统性能进行评估。仿真结果表明:2种惰化系统均能控制膜前温度维持在90℃;燃油热沉控温的多舱油箱惰化系统在整个飞行过程中,各舱油箱中最高燃油温度小于32℃,没有超过许用限制;对于直升机而言,由于油箱相比大型客机而言体积较小,通过计算可得,冷却空气控温的多舱油箱惰化系统的燃油代偿损失小于燃油热沉控温的多舱油箱惰化系统的燃油代偿损失。仿真结果为多舱油箱惰化系统的设计和优化提供了参考依据。

考虑土-储罐-液体相互作用的隔震储罐简化力学模型及地震响应研究

为了寻求一种既能减震又能降低成本的储罐结构,提出一种隔震储罐结构体系,根据力的平衡原则推导了滚动隔震装置恢复力模型,得出了复合滚动隔震装置的恢复力模型。基于三质点模型和场地土模型,提出了考虑土-储罐-液体相互作用(STLI)的隔震储罐的简化力学模型和运动方程,并研究了考虑STLI效应和不考虑STLI效应时抗震储罐和隔震储罐在不同场地的地震响应。结果表明:隔震储罐能够有效地降低其基底剪力及倾覆弯矩,但对晃动波高的控制有限,建议在高烈度区,满足晃动波高的前提下,隔震储罐在设计时可以降低烈度。考虑STLI效应后,抗震储罐的基底剪力和倾覆弯矩明显降低,且从Ⅰ类场地到Ⅳ类场地差异率逐渐增大,软土场地降低最为显著。隔震储罐地震响应受STLI效应的影响较小,可以有效地隔断上部结构与场地土之间的耦联,弱化STLI效应对上部结构的影响。

半挂液罐车弯道安全车速优化控制

为降低半挂液罐车驶过弯道路段过程中的侧翻事故风险,提出了基于最优控制的半挂液罐车弯道安全车速优化控制方法。该控制方法以侧翻事故防控为优先目标,以高效通行为辅助目标,帮助半挂液罐车在驶向弯道时提前获得无横向失稳隐患的最优车速控制方案,实现“预防式”的车辆主动安全控制。同时为提高控制方案有效性,利用正弦波动方程拟合罐内液体纵向转移过程,结合基于改进准静态法的罐内液体横向偏移规律,构建了具有纵横双维度描述能力的罐内液体晃动模型,提高了最优控制问题成本函数中半挂液罐车横向稳态表征指标的准确性。仿真结果表明:受控半挂液罐车驶过弯道过程中的瞬时横向载荷转移率始终处于[-0.7,0.7]的安全范围内;不同弯道半径下车辆瞬时横向载荷转移率均有下降,且在弯道半径61 m时降幅最大;受控半挂液罐车最大瞬时横向载荷转移率最大降幅达到0.07;车速控制对道路通行效率的负面影响较小。该控制方法帮助半挂液罐车避免侧翻事故,适用于多种不同半径的弯道路段。

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。

高性能分离膜生产设备液体槽用橡胶密封型材的研制

介绍了高性能分离膜生产设备液体槽用橡胶密封型材的工作原理、配方组成和工艺设计。结果表明,采用EPDM基材、白炭黑/高岭土补强体系、硫黄/过氧化二异丙苯/N-环己基-2-苯并噻唑次磺酰胺/三烯丙基异氰脲酸酯并用硫化体系,研制的橡胶密封型材具有优异的耐水性、耐酸碱性、耐次氯酸钠性、耐溶剂性、高回弹性、低变形、耐老化性和高抗污染性等;有效解决了液体槽槽体与独立辊架横梁之间的密封,确保了生产过程中的稳定性和液体处理膜质量控制。

空间液氪气液分离装置流阻特性及数值模拟

为满足低温推进剂在空间微重力环境中的气液分离要求,针对液氪低温推进剂在轨管理与传输问题,建立筛网式气液分离装置单通道流动压力损失的理论预测模型,获取120 K饱和状态液氪在325×2300荷兰斜纹编织网中流动的泡破点压力。对比分析了不同低温流体、通道宽度、质量流量对过网压降的影响规律,获得了液氪在通道中流动的压降分布,并通过国外液氢过网压降实验数据对模型进行了验证。通过建立液氪单通道流动数值仿真模型,较好地预测了过网压力损失。