船舶碰撞数值仿真的附加质量模型

根据船舶碰撞的运动滞后和局部损伤特性 ,采用附加质量处理流体 结构耦合作用 ,用详细的有限元模型表达撞击船首和被撞船侧的直接涉撞区结构 ,而将非碰撞区的船体结构视为刚体 ,形成一个附加质量模型用于碰撞仿真计算。附加质量模型不仅建模工作量小 ,而且CPU时间也大大减少。算例表明 ,附加质量模型与流固耦合模型的分析结果具有良好的一致性 ,可以满足一般的工程精度要求。     

三峡升船机船—水—厢耦合系统的非线性有限元时域计算

根据三峡升船机船厢的受力特点，在船厢的纵剖面上建立了非线性水波方程和船—水—厢的耦合运动方程。对非线性水波方程利用摄动理论进行分解得到一阶方程和二阶方程，然后运用伽辽金法得到耦合的有限元离散方程，结合精细积分法进行时域计算。计算采用平面八节点等参单元，并给出了若干算例。     

计算流体力学在工程流体力学课程中的应用与实践

随着时代发展,适应大学生特点的教学改革在不断进行,要求教师培养学生的学习能力而不是单纯的传授知识.针对本科生工程流体力学课程的教学模式进行改革,将计算流体力学引入到工程流体力学课堂.5年的教学实践,证明其对学生们的工程流体力学课程和后续专业课的学习有很大帮助.文中以实例的形式介绍了将计算流体力学与本科生流体力学课程结合的方法与实践,深入探讨了教学改革.该实践是提高教学质量的有价值的尝试.     

考虑粘性作用情况下船在船厢中运动的水动力学分析

从根据浅水特性在垂直方向所平均化的N-S方程出发,利用有限元计算船舶进出船厢时的水动力学过程和船舶运动过程中的升沉、纵倾及船舶与厢底的最小间隙.由于在平均过程中保留了粘性项,同时产生了底摩擦项,使得到的数学方程更接近真实物理问题,另一方面也增加数值计算的稳定性.本文提出了随非惯性系一起运动的开边界的辐射条件.关于压力的求解,在船底与自由表面分别利用压力泊松方程求压力及自由表面利用连续方程求波高的求解方法.由针对三峡升船机的数值模拟的计算结果看,计算结果合理,计算方法稳定.     

附加质量变化率在航行体出水过程中的影响研究

航行体出水运动过程中,附加质量逐渐减小,在一些研究其出水运动的模型中,只考虑了随状态变化的附加质量值,而没有充分考虑附加质量的变化过程。本文通过建立航行体出水运动物理模型和对航行体出水过程的受力分析,构建了出水过程的动力学方程。为了更加准确模拟航行体出水情况,在进行理想流体作用力求解时,引入附加质量变化率研究附加质量在出水过程中的变化以及对出水过程的影响。通过对数学模型的仿真分析表明,在计算模型中考虑附加质量变化率能显著提高模型的计算精度。     

在实验模态分析中如何消除附加质量附加刚度对实模态参数的影响

本文讨论了在实验模态分析中如何消除附加质量和附加刚度对实模态参数影响的方法.为了验证方法的有效性,文中给出了算例和实际应用的例子.文末还讨论了输入数据的误差和输入模态的阶数对结果的影响.     

Melnikov方法在输流管混沌运动研究中的应用

对基础简谐运动激励下两端固定输流管道的混沌运动进行了研究，推导出了系统的运动方程，确定了系统存在的平衡点及其稳定性，计算出了未扰系统的同宿轨道，并利用Melnikov方法得到了系统发生混沌运动时参数需满足的临界条件，同时还利用相平面图和：Poincare映射等方法对管道的混沌运动进行了数值模拟，通过比较发现，由Melnikov方法确定的临界参数值要稍小于数值模拟中首次观察到混沌运动时对应的临界值。     

计算流体力学在炼钢中的应用和发展

介绍了计算流体力学应用到炼钢过程中所面临的边界条件和材料物性数据等问题．并着重评述了钢包精炼和连铸结晶器过程中流动及相关现象研究概况,指出炼钢过程中数值模拟的目标不是获得描述某给定过程的精确数值,而是获取过程知识,特别是获取实验无法得到的信息．数值模拟不能代替实验,相反是扩大实验的内容．将来的炼钢过程数值模拟工作将面临更复杂的三维、时间相关的多相反应系统或气金渣等自由表面问题的挑战．      

考虑当地涡旋运动修正的湍流模型在非定常空化湍流流场计算中的应用

为了更精确地模拟当地涡旋运动对复杂非定常空化湍流流动的影响,考虑当地涡旋运动特性对标准k-ε湍流模型进行了修正;并采用该修正模型对二维Clark-Y水翼周围非定常空化湍流场进行了计算;通过与实验结果进行对比,分析并验证了该修正模型计算结果的有效性。研究表明:该修正湍流模型根据当地涡旋效应对湍动能输运方程中的生成项进行修正,可以有效解决标准k-ε模型对湍动能的过度预测问题,得到的空化核心区域时均湍动能和湍流黏性的预测结果降低了约30%,与实际值更为接近;标准k-ε模型计算所得的时均空泡长度不大于0.6倍弦长,而修正模型计算所得的时均空穴可以覆盖水翼吸力面;修正模型可以准确预测水翼吸力面表面空泡的非定常脱落过程,包括附着空穴的拉伸和断裂,以及脱落空泡的逐渐消失。     

在两层不同爆速炸药滑移爆轰作用下飞板运动的数值计算研究

本文研究用低爆速炸药复盖高爆速炸药在定滑移爆轰作用下飞板运动的计算方法,并对惯性复盖与炸药复盖的结果作出相互比较。     

Numerical analysis of fluid flow and added mass induced by vibration of structure

IntroductionInmanycases ,theeffectofasurroundingfluidonstructuralvibrationscannotbeneglected .Forexample ,analyzingthefreevibrationsofshipsmustcalculatetheaddedmassofthesurroundingwater[1].Mostspacecraftcomponentsarelow_density ,low_stiffnessandwithwide_openedareas,sotheeffectofsurroundingairisobviousandcannotbeneglectedinthenumericalsimulationoftheirmodaltestonground[2 ].Sinceairflowinducedbythestructuralvibrationswithlowfundamentalfrequencyandsmallamplitudemotion (Forexample ,thefundamental…     

The added mass coefficient of a dispersion of spherical gas bubbles in liquid

Models published in the two-phase flow literature for the added mass coefficient of a dilute bubbly dispersion are discussed and compared. It is shown that the differences between the models are mainly due to the different ways in which the added mass is defined. Also, approximate expressions for the added mass coefficient of non-dilute bubbly dispersions are given. Finally, the use of the models in an equation for the average motion of the bubbles is briefly discussed.     

An experimental and numerical study of heave added mass and damping of horizontally submerged and perforated rectangular plates

Forced harmonic heave motions of horizontally submerged and perforated rectangular plates are studied experimentally and numerically at both a deep and shallow submergence. The steady-state vertical forces are expressed in terms of added mass and damping coefficients. The numerical results are partly obtained by combining potential flow with linear free-surface conditions and a nonlinear viscous pressure loss condition at the mean oscillatory plate position. A domain decomposition technique is applied with a boundary element method in the inner domain and an analytical representation of the velocity potential in the outer domain. A drag term accounts for the vortex shedding at the outer plate edges. The numerically predicted Keulegan–Carpenter number dependent heave added mass and damping coefficients agree reasonably with experimental values, in particular for the deeper submergence.     

Mixed compatible element and mixed hybrid incompatible element variational methods in dynamics of viscous barotropic fluids

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Calculation of the Flow around a High-Pressure Turbine Blade with Cooling-Jet Injection from Slots at the Leading Edge

A fully vectorised, basically three-dimensional finite-volume multi-block method for flows with complex boundaries is applied in a stripped-down two-dimensional version for the investigation of the flow field in the leading-edge region of a high-pressure turbine blade with slot cooling-jet injection. The calculation results are compared with experiments and the numerical results of other investigators. The present method yields excellent agreement with the experiments for the isentropic Mach number distributions on the blade surface. All numerical results for the velocity field were found to be in very good agreement with each other and with experiments on the suction side, while the agreement is not as good on the pressure side.     

A new type of plate bending element

Based on a two-field generalized variational principle, a new type of arbitrary quadrilateral plate bending element, with four nodes and with the effect of transverse shear deformation taken into account, is proposed. The element is applicable to a wide range of plate thickness and an explicit expression of stiffness matrix can be obtained. Therefore, it possesses the distinguished features of general applicability, high precision and less computer time.     

Flow field calculation and its experimental verification for inertia stage of marine gas turbine air intake filter

A numerical method is presented in this paper for the solution of flow field in marine gas turbine air intake filtration channel. The flow field was successfully calculated by this method, and aerodynamic characteristics were obtained for various types of filtration channels. This work is expected to be of practical importance for the design of such filters. Upstream difference was adopted to discretize the non-conservative type N-S equation for two-dimensional, time-dependnet, viscous and incompressible flow, and the stability, convergence, accuracy and artificial viscosity of the resulting difference equation were examined. This equation can be used to calculate viscous flows with Reynolds number up to tens of thousands. Also presented in this paper is a calculation method for treating wall vortex at boundary inflection points. Careful studies show that calculation based on the difference equational and wall vortex treatment proposed here are in good agreement with experimental results.     

基于Reynolds边界的滑动轴承动力学系数的计算及应用

运用有限元方法,在不需要额外求解Reynolds方程的情况下,求解了具有Reynolds边值条件的流体润滑问题,使得同时完成动力积分过程中非线性油膜力及影响Floquet乘子求解的油膜力Jacobian矩阵的计算成为可能;运用打靶法及预估-校正和打靶法相结合的延续算法考察了轴承-转子系统的非线性不平衡响应及其随轴承设计参数改变而出现的分岔现象,实现了计算量的有效减少。     

可压缩多介质流动的间断有限元方法

采用间断有限元方法、LS方法和通量装配技术相结合,建立了一种计算可压缩多介质流动的有效 方法。计算中以光滑Heavside函数构造流体比热比和重新初始化方程中的符号距离函数,并采用通量装配 技术抑制界面附近的非物理振荡。为解决可压缩多介质流动提供一种新的手段。