汽车罐车横向运动液体晃动动力学特性模拟

针对部分充液罐车横向运动时罐体内液体的晃动问题,基于多相流模型,运用VOF法对罐车在高速转弯或紧急避让时罐内液体的晃动动力学特性进行了数值模拟.分析了罐车防波板数量、结构以及充液比、侧向加速度等因素对液体晃动动力学特性的影响.模拟结果表明:防波板横向布置可显著降低罐内液体对罐壁的侧向冲击力,且布置一块较大面积的防波板即可达到较好的防波效果;随着充液比的增大,液体横向晃动减小,并能快速趋于平稳;随着罐车侧向加速度的增大,液体横向晃动增大,进而影响车辆侧向稳定性.     

轴向运动梁的横向振动分析

论述了轴向运动梁横向振动问题以及研究轴向运动梁横向振动问题的方法,指出对轴向运动梁横向振动问题研究中存在的一些错误并进行了更正.针对一端可看作固定边界条件的轴向运动悬臂梁,基于连续体的模态叠加法,推导出含自重效应的轴向运动梁动力响应的计算公式,进行实例计算,并对计算结果进行了详细的讨论,得出影响轴向运动梁振动响应的因素主要有速度和运动方向.     

轴向运动导电导磁梁的磁弹性振动方程

针对磁场环境中轴向运动导电导磁梁磁弹性耦合振动的理论建模问题进行研究.基于Timoshenko(铁木辛柯)梁理论并考虑几何非线性因素,给出轴向运动弹性梁在横向双向振动下的形变势能、动能计算式以及电磁力和机械力的虚功表达式.应用Hamilton(哈密顿)变分原理,推得磁场中轴向运动Timoshenko梁的非线性磁弹性耦合振动方程,并给出了简化形式的Euler-Bernoulli(欧拉 伯努利)梁磁弹性振动方程.根据电磁理论和相应的电磁本构关系,得到载流导电弹性梁所受电磁力的表达式,基于磁偶极子-电流环路模型给出铁磁弹性梁所受磁体力和磁体力偶的表述形式.通过算例,分析了轴向运动导电弹性梁的奇点分布及其稳定性问题.     

考虑滩地植被的复式断面河道水流的二维解析解

针对滩地植被化的复式断面河道的水流特性,从沿水深积分的紊流时均运动微分方程出发,基于恒定均匀流的假设,给出了植被作用下河道水流水深平均流速沿横向分布的二维解析解.其中,将植被对水流的影响归结为拖曳力项,在模型中计及了二次流的影响,并对二次流强度系数K的取值进行了初步探讨.分别对顺直河道横断面和蜿蜒河道的顶点断面进行了计算,计算结果与试验资料符合良好,表明给出的二维解析解可用于植被作用下复式断面河道水流水深平均流速沿横向分布的数值预报.     

计及弯曲刚度的印刷运动薄膜横向振动控制研究

研究了不同边界条件下,计及弯曲刚度的轴向运动薄膜横向振动的主动控制问题.建立计及弯曲刚度的印刷运动薄膜的计算模型.利用有限差分法,对轴向运动薄膜的振动微分方程进行离散,推导出轴向运动矩形薄膜横向振动控制系统的状态方程.采用次最优控制法,对不同边界条件下轴向运动矩形薄膜横向振动进行主动控制研究.计算结果表明:采用次最优控制法能够在短时间内迅速、有效地降低运动薄膜的振动强度,并使之衰减趋近于0.作动器作用在固定位置点处时,对运动薄膜施加控制后,四边简支边界条件下的控制效果好.作动器作用在不同位置点处时,两种边界条件下中心点处的控制效果最好.计算证明次最优控制法能够有效地抑制印刷过程中计及弯曲刚度的轴向运动薄膜的横向振动,从而提高印刷套印精度,保证精密印刷质量.     

移动载荷作用下轴向运动载流梁的参强联合共振

研究磁场环境中移动载荷作用下轴向运动梁的磁弹性参强联合共振问题.以轴向运动载流梁为研究对象,建立横向磁场中受移动载荷作用下梁的力学模型.应用Hamilton(哈密顿)原理,得到梁的非线性磁弹性振动方程.利用Galerkin(伽辽金)积分法和多尺度法,推得以移动载荷为变量的幅频响应方程.通过数值计算,绘制了振幅随调谐参数、拉力扰动幅值、移动载荷、磁感应强度的变化规律曲线图,分析了电流密度、磁感应强度、移动载荷等变量对参变系统动力学特性的影响.结果表明:系统呈现典型的参强联合共振特性;移动载荷、磁感应强度能够起到抑制共振幅值多值现象的产生.     

量子微腔中原子束偏转与衍射的横向动量效应

通过推广Fröhlich变换方法,在大失谐条件下,研究了腔场中超冷原子质心运动的动量转移问题.分析微腔-原子系统的动力学演化,得到了场-原子动量交换所导致的原子束偏转和衍射与腔场统计分布的关系.理论分析特别考虑了横向动量对腔中原子运动的影响.     

粘弹性运动带动力响应分析

基于Kelvin粘弹性材料本构模型及带运动方程,建立了运动带非线性动力学分析模型.基于该模型和Lie群分析方法推导了匀速运动及简谐运动带线性问题的解析解;基于该非线性模型的数值仿真讨论了运动带材料参数、带稳态运动速度、扰动速度对系统动态响应的影响.结果表明:1)当带匀速运动时,无论系统是线性还是非线性,运动带横向振动"频率"都随着带运动稳态速度增加而减小.2)随着材料粘性增加,系统耗散能力逐渐增强,动态响应逐渐减小.3)当带运动速度简谐波动时,系统动态响应随扰动速度增大而增大.扰动频率对带横向振动影响较大.     

基于气体运动论的差分算法对管道流动数值研究

从分析研究求解Boltzmann模型方程的气体运动论数值计算方法特点出发,设计了几种求解离散速度分布函数不同精度的差分显式与隐式气体运动论数值格式.通过对不同Knudsen数下一维非定常激波管内流动、二维槽道流问题计算研究与应用测试,分析了不同差分格式数值离散效应对计算结果的影响,研究讨论了提高气体运动论数值算法计算效率的途径和差分离散处理所适用的计算准则等问题.     

在微重力条件下无限长方柱中的自然对流*

为了研究在宇宙空间微重力环境中.自然对流对流体运动的影响,将变量展成Grashof的摄动级数,使用摄动理论将Navier-Stokes方程组简化成:关于温度T的Poisson方程,关于流函数ψ的非齐次biharmonic方程.选取一无限长封闭方柱体,假定在柱体边界上预先给定一种线性温度分布,使用数值计算方法求解上述简化方程组,得到各阶流函数和各阶温度值,进而详细地研究了方柱中流体的运动状况,分析和讨论了某些参数,如Grashof数和Prandtl数对流体运动的影响,最后将计算结果与由未简化方程推算的结果进行比较,证实近似方法正确地简化了复杂的流体运动过程,并且可以推广、运用到三维问题上.     

Prestress Losses in the Stabilizing Cables of a Composite Saddle-Shaped Cable Roof

The paper deals with a square composite saddle-shaped cable roof 30 × 30 m in the plan, which is formed by two orthogonal cable groups joined with a compliant support contour. The kinematic invariability of the roof is achieved by prestressing the cable net. From the viewpoint of material consumption, the cable roof has rational geometrical characteristics. A hybrid composite cable on the basis of CFRP, GFRP, and steel is considered as a material for contour cables. The load-carrying and the stabilizing cables are made of steel. Prestress losses in the stabilizing cables are determined for three variants of prestressing. The possibility of reducing the consumption of cable materials by prestressing each cable of the net by an individual force is revealed.     

Exact mode shapes for a continuous tether

The vibrational problem of a tether modeled as a cable terminated by two end masses is considered (dumbbell configuration). For an inextensible cable the mode shapes are combinations of Legendre functions. The spacing of the frequencies depends on the mass ratios of the end masses and the cable mass. For the extensible cable, the exact vibrational problem is set up. The conditions under which approximations by more simple models are valid are derived.     

Decreasing the Displacements of a Composite Saddle-Shaped Cable Roof

The structural possibilities of decreasing the compliance of a composite saddle-shaped cable roof having a compliant support contour are investigated. The use of a supporting contour consisting of cables joined together with tie-bars is considered as a structural method enabling one to decrease the compliance of the roof. Each cable of the support has its own initial flexure. The method is most efficient from the viewpoint of material consumption per unit of covered area relative to the increasing rigidity and prestress level of the cable net.The efficiency of the method was evaluated by a numerical experiment, which was carried out for a composite saddle-shaped cable roof 50 × 50 m in the plan. The roof was formed by two orthogonal cable groups joined with a compliant supporting contour. A hybrid composite cable based on a carbon-fiber-reinforced plastic, a glass-fiber-reinforced plastic, and steel was considered as a material for the cable net in combination with steel. The material consumption and the maximum vertical displacement of the cable net in relation to the initial geometrical characteristics of the supporting contour were obtained. A possibility of decreasing the maximum vertical displacements of the roof by 8% was established.     

Modeling and vibratory characteristics of a mass-carrying cable system with multiple pulley supports in span range

A theoretical dynamic model of a multi-segment mass-carrying cable system with multiple pulley supports is derived. Unlike many existing analytical cable models, the relative movement between the cable and pulley supports is considered here. The cable is modeled as a combination of a number of segments connecting the mass and the pulley supports. The Hamilton principle is used to account for the relative moving boundaries between the cable and the pulley supports. From the continuity conditions, boundary conditions and force equilibrium conditions, the non-dimensional unforced undamped characteristic equation is obtained. The natural vibratory characteristics for this kind of cable are also determined. The effects of the mass ratio and sag-to-span ratio on the frequency spectra are studied. The Pareto chart of the fundamental frequency of the multi-segment cable is examined. The results show that the frequencies are either sensitive to or independent of non-dimensional parameters in certain parameter ranges. Veering phenomena also appear between the frequencies of two approaching modes.     

Control of an extending nonlinear elastic cable with an active vibration control strategy

An active control strategy based on the fuzzy sliding mode control (FSMC) is developed in this research for controlling the large-amplitude vibrations of an extending nonlinear elastic cable. The geometric nonlinearity of the cable and the fixed–fixed boundary of the cable are considered. For effectively and accurately control the motion of the cable with the active control strategy developed, the governing equation of the elastic cable is established and transformed into a multi-dimensional dynamic system with the 3rd order Galerkin method. The active control strategy is developed on the basis of the dynamic system, and the control strategy is applicable to multi-dimensional dynamic systems. In the numerical simulation, large-amplitude vibrations of the cable are effectively controlled with the control strategy. The results of the research demonstrate significances for controlling the cable vibrations of an elevator in practice.     

On the determination of natural frequencies and mode shapes of cable-stayed bridges

An accurate analysis of the natural frequencies and mode shapes of a cable-stayed bridge is fundamental to the solution of its dynamic responses due to seismic, wind and traffic loads. In most previous studies, the stay cables have been modelled as single truss elements in conventional finite element analysis. This method is simple but it is inadequate for the accurate dynamic analysis of a cable-stayed bridge because it essentially precludes the transverse cable vibrations. This paper presents a comprehensive study of various modelling schemes for the dynamic analysis of cable-stayed bridges. The modelling schemes studied include the finite element method and the dynamic stiffness method. Both the mesh options of modelling each stay cable as a single truss element with an equivalent modulus and modelling each stay cable by a number of cable elements with the original modulus are studied. Their capability to account for transverse cable vibrations in the overall dynamic analysis as well as their accuracy and efficiency are investigated.     

3D mathematical model and numerical simulation for laying marine cable along prescribed trajectory on seabed

In this paper, we establish a mathematical model, that is, an initial-boundary value problem of partial differential equations (PDE), to describe the three dimensional (3D) motion of a marine cable being laid onto the seabed of varying depth. Based on this PDE model, a numerical method for simulating dynamically the moving process of marine cable is developed, which can be used to determine the cable laying operations in practice such that the marine cable can be laid on the prescribed position on seabed.     

缆机起重作业驾驶员的操作行为可靠性研究

缆机是大坝浇筑过程中的主要运输设备之一,缆机驾驶员操作水平直接关系缆机起重作业安全.为有效提高缆机起重作业驾驶员操作行为可靠性,预防起重作业安全事故,针对缆机起重作业周期性多维运动的特点,分解驾驶员操作流程;剖析操作行为失误,建立驾驶员行为模式;从时间角度量化操作流程,计算缆机驾驶员操作行为响应失误概率;构建操作行为可靠性分析模型,定量表达操作行为可靠性,分析人因失误对缆机起重作业安全事故的影响.结果表明,吊具与吊罐对接、混凝土卸料等作业过程的缆机驾驶员操作行为可靠性低,需加强安全培训,严格考核制度,从根本上提高缆机驾驶员操作行为的可靠性,以期提升缆机生产效率,实现预防安全事故的目标.     

Finite Element Modelling of Moored Vessels

In this paper, we develop a new finite element model for a cable suspended in water. Global existence and uniqueness of solutions of the truncated system is shown for a slightly simplified equation describing the motion of a cable with negligible added mass and supported by fixed end-points. Based on this, along with well known results on local existence and uniqueness of solutions for symmetrizable hyperbolic systems, we conjecture a global result for the initial-boundary value problem. The FEM model for the cable is assembled to give a model of a multi-cable mooring system, which, in turn, is coupled to a rigid body model of the floating vessel. The result is a coupled dynamical model of a moored vessel, which can be applied to applications such as turret-based moored ships, or tension leg platforms.