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．  

VLCC液舱晃荡仿真模型

分别采用3D模型和2D模型对VLCC液舱进行晃荡仿真,通过对两个模型的流体流动情况和对应位置压力的比较,得出短期搜索及长期分析中采用2D模型方案进行VLCC液舱晃荡仿真分析是可行的结论. 讨论两种模型的计算效率,认为2D模型方案可以大大提高仿真效率,具有工程实用性.  

Numerical simulation of structure response outfitted with a tuned liquid damper

An integrated fluid–structure numerical model has been developed to simulate the response of a single degree of freedom (SDOF) structure outfitted with a Tuned Liquid Damper (TLD). The structure is exposed to random external excitations. A non-linear, two-dimensional, flow model has been developed using the finite-difference method. Unlike most existing flow models, the present model does not include any linearization assumptions; it rather solves the entire nonlinear, moving boundary, flow problem under conditions leading to large interfacial deformations. The free surface has been reconstructed using the volume of fluid method and the donor–acceptor algorithm. The Duhamel integral method has been used to determine the response of the structure. The effectiveness and accuracy of the flow model has been validated using a set of benchmark problems and experimental data. The numerical results of this model have been compared with results of an equivalent TMD model. The present fluid–structure model can be used as a valuable tool for performance evaluation and design of more effective tuned liquid dampers.  

Design optimization of containers for sloshing and impact

A multidisciplinary design and optimization (MDO) method is presented to support the design process of partially filled liquid containers subject to the disciplines of sloshing and impact analyses. Experimental techniques are used to understand sloshing as a phenomenon and to evaluate the computational fluid dynamics code. Validation includes qualitative comparison of visual free-surface behavior and quantitative comparisons of pressure measurements in the time and frequency domain. The liquid motion exhibits good comparisons in time. Deviations are caused by both the experimental signal filtration process and deficiencies in the low-frequency measurement capability of the accelerometer. The first two odd oscillatory modes are accurately captured. An objective function for the quantitative evaluation of the sloshing phenomenon is proposed. For impact, the von Mises baffle stress is used. Single and multidisciplinary optimization formulations using LS-OPT are presented and examined. The multidisciplinary optimum proved to be a compromise between the optima obtained when considering the two single disciplines independently.  

Comparison of finite element and pendulum models for simulation of sloshing

The pendulum model is a cost effective tool for the simulation of sloshing. However, the accuracy and applicability of the model has not been well established. In this article, we compare the simulation results obtained from the pendulum model and a more complicated finite element model for sloshing of liquids in tanker trucks. In the pendulum model, we assume that the liquid in the tanker is a point mass oscillating like a frictionless pendulum subjected to an external acceleration. In the finite element model, we solve the full Navier-Stokes equations written for two fluids to obtain the location and motion of the free surface. Stabilized finite element formulations are used in these complex 3D simulations. These finite element formulations are implemented in parallel using the message-passing interface libraries. The numerical example includes the simulation of sloshing in tanker trucks during turning.  

Modeling and Simulation of Vehicles Carrying Liquid Cargo

A method for modeling and simulation of the dynamics ofvehicles subject to liquid slosh loads is presented. The vehiclecomponents are modeled as a multibody system, the sloshing liquiddynamics is determined from solving the instationary, incompressibleNavier–Stokes equations under consideration of free surfaces. Toanalyze the overall system dynamics, the concept of modular simulationis applied decomposing the dynamic system into subsystems. The rigidbody and fluid subsystems are modeled by separate software codes whichare coupled by the transfer of in- and output variables duringsimulation runtime.To account for the vehicle motions, thefluid equations of motion are transformed into a moving frame ofreference, inputs and outputs of the fluid subsystem are derived. Forsolving the incompressible Navier–Stokes equations, efficient methodshave to be applied. The system of equations resulting from a FiniteVolume discretization is solved by a multigrid method, the location offree surfaces is determined by a Volume-of-Fluid approach. To validatethe methods for modeling fluid dynamics, benchmark calculations of theflow around a cylinder and the collapse of a water column are presented.The proposed method for modeling the interaction of sloshingliquids and vehicle motions is used to determine the brakingcharacteristics of partially liquid-filled tank vehicles. It is shownthat a loss of directional control due to wheel lock-up is more likelyfor tank vehicles with sloshing liquid cargo than for vehicles loadedwith equivalent rigid cargo because of the dynamic liquid load shift.  

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.  

误差激励作用下三维矩形液舱晃荡数值仿真

原始激励的随机小幅变化会对晃荡载荷造成不确定影响,往往具有较强的随机性和非线性现象.通过计算流体力学(Computational Fluid Mechanics,CFD)方法构造三维矩形液舱载液率为85%的晃荡数值模型,并基于相同条件开展模型晃荡实验;通过追踪自由表面变化和晃荡冲击压力时程比较分析验证数值模型的有效性.基于原始激励构造一定误差变化范围(2%,5%和10%)内的误差激励,通过数值模拟分别提取拐角监测位置处的晃荡载荷时程曲线.研究结果表明:在不同误差激励下,虽然晃荡波形和频率基本一致,但压力峰值偏差与误差大小不呈现正相关效应,最大偏差约为33.17%;微小激励误差有可能对晃荡载荷结果造成较大的偏差影响.  

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.  

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%.