滚装船-滑动车辆浮基多体系统的横摇研究

波浪和内部滑动车辆共同作用,使滚装船的横摇加剧。这是许多滚装船发生倾覆的重要原因之一。本文对由滚装船和滑动车辆组成的浮基多体系统中,取滚装船的横摇角和车辆在甲板上的横向位移为此系统的两个自由度。考虑非线性恢复力矩和非线性阻尼力矩的影响,运用浮基多体系统动力学方法,建立了系统的动力学方程。以某型海峡滚装渡轮为例,对在若干车辆同步滑动和波浪共同作用下的滚装船非线性横摇响应和车辆位移响应进行了数值计算,并与线性响应进行了比较,得出了考虑非线性时横摇角显著偏大的结论。     

浮动冲击平台冲击环境对设备响应的影响

对浮动冲击平台提供给设备的冲击环境及舰载设备在不同冲击环境下的响应进行了数值模拟和理论分析。以美国中型浮动冲击平台为计算模型,将设备基座的冲击环境与德国规范BV 043-85进行了比较,为分析两个体系在设备抗冲击要求中谱加速度的差异,对不同舰载设备进行数值模拟计算,并通过虚拟约束边界模态方法,提出不同冲击环境下基础激励的多自由度系统响应的计算方法。数值分析及理论计算结果表明:冲击谱中谱加速度对舰载设备响应影响较小,而谱位移和谱速度对设备响应有较大影响,理论计算得到的多自由度系统响应与数值模拟结果较一致,同时在进行浮动冲击平台设计时可不考虑谱加速度对设备响应的影响。     

潮流发电装置运动衰减特性与不规则波响应

为了研究基于竖轴水轮机的漂浮式潮流能发电装置的运动衰减特性与不规则波响应,提出了基于船模拖曳水池的系泊试验方法,设计了试验模型和装置,构建了系泊试验平台,进行了组合模型的自由衰减试验、系泊衰减试验和系泊状态下的不规则波响应试验. 衰减试验中测量了模型的摇动衰减特性,不规则波响应试验中测量了系缆的拉力响应和组合模型的摇动响应. 试验研究得到了关于漂浮式潮流能发电装置的衰减运动特性和4级海况、0.6m/s流速时1号系缆的拉力响应以及组合模型的摇动响应. 研究可为基于竖轴水轮机的漂浮式潮流能发电装置的理论研究和工程应用提供参考和借鉴.     

多柔体系统动力学建模与优化研究进展

多柔体系统是由柔性部件和运动副组成的力学系统,在航空、航天、车辆、机械与兵器等众多工程领域具有广泛的应用前景, 其典型的代表包括柔性机械臂、直升机旋翼、卫星的可展开天线、太阳帆航天器等. 近年来,随着工程技术的发展,多柔体系统动力学问题日益突出,尤其是含变长度柔性部件的多柔体系统,不仅涉及其动力学 建模与计算,还涉及其动力学优化设计. 事实上,部件柔性对多柔体系统的动力学行为影响很大,直接影响到优化结果,因此需要发展基于多柔体系统动力学的优化设计方法. 本文首先阐述了多柔体系统动力学优化的研究背景及意义,简要回顾了多柔体系统动力学建模的3类方法:浮动坐标方法、几何 精确方法和绝对节点坐标方法,并介绍了含变长度柔性部件的多柔体系统动力学建模方法. 系统概述了多柔体系统动力学响应优化、动力学特性优化和动力学灵敏度分析3个方面的研究进展,并从尺寸优化、形状优化和 拓扑优化 3 个方面综述了多柔体系统部件优化的研究进展. 本文最后提出了在多柔体系统动力学优化研究中值得关注的若干问题.      

水浮力对浮桥动力响应特性的分析

为了研究水介质的浮力对桥梁静态响应、特别是动态响应的影响,了解水浮力在桥梁动力响应上的作用及其大小,利用虚功原理和振型叠加法对桥梁运动的控制方程进行求解,并编制了通用的求解程序,通过对比简支梁桥和浮桥各阶振型的传播速度、静力作用、单阶荷载作用以及移动荷载作用下的动力响应,得出水浮力的存在大大降低了浮桥的挠度,使得浮桥的动力响应存在临界长度,即简支梁桥的运动整体性强,而浮桥的运动局部性强,对浮桥进行动力分析时,可以在临界长度以内进行处理,而不必对整个桥梁进行求解.     

多体空气动力学研究进展

多体飞行器普遍存在于航空航天、空天和武器领域中, 主要有以下三大类型: (1) 多个飞行器相互不接触的近距离飞行; (2) 多体飞行器相互接触或组合飞行; (3) 多体飞行器回收或解锁分离过程的相对运动. 多体飞行器在飞行、回收或分离过程中存在相互的流场干扰或作用, 使多体飞行器具有不同于孤立体飞行器的流动物理或特征, 特别是在超声速、高超声速的多体流动中, 多体间存在多重激波反射、衍射以及激波与旋涡、激波与边界层相互干扰或作用, 这些复杂流动能显著地改变多体飞行器的空气动力学特性. 作者引入“多体空气动力学”概念对多体飞行器这一类问题进行概括和总结, 并阐述其基本内涵、应用场景和研究方法/手段及典型多体构型的超声速/高超声速流动结构和特征.      

Transient response of a moving spherical shell in an acoustic medium

A ring-stiffened spherical shell is submerged in an acoustic medium. The shell is thin and elastic. The acoustic medium is inviscid, irrotational and compressible. The center of mass of the shell is subjected to a translational acceleration which is an arbitrary function of time. The absolute displacements of the shell are expressed in terms of the relative displacements and the displacement of the base of the shell, base being defined as the rigid ring placed at the equator. The motion of the acoustic medium is governed by the wave equation. The transient response of the shell is investigated numerically. The results are compared with the results of the in-vacuo response. The effects of the plane wave approximation and the base velocity on the transient response of the shell are studied. The numerical results show that the plane wave approximation accurately predicts the response of the shell in the acoustic medium for short times after excitation. The displacements of the shell in fluid are larger than those in vacuo. But when the base of the shell is restrained from translating, the displacements in fluid are smaller than those in vacuo. Therefore, base translation has a very significant effect on the transient response of the shells submerged in an acoustic medium.     

移动车辆作用下弹性基础无限长梁的动力响应

通过坐标变换方法,研究了匀速移动的车辆对弹性基础无限长梁的动力响应,给出了位移和内力的计算方法,将车辆简化为移动力,移动质量,移动的振动质量三种模型,比较了它们对梁的影响,对某型带式舟桥的数值分析表明,振动质量模型较合理,给出了浮桥计算时,动力放大系数的建议值     

应用浮动冲击平台考核舰载设备响应分析

为研究安装甲板模拟器的浮动冲击平台系统考核舰载设备的机理,对整个系统建立有限元模型进行数值模拟并建立力学模型进行了理论分析。根据船体甲板结构产生的垂向低通滤波特性,提出甲板模拟器具有减缓高频冲击并满足设备安装频率要求的作用。将被试设备的浮动冲击平台考核系统简化为有阻尼的三自由度系统强迫振动模型,通过拉普拉斯变换方法求解了不同冲击环境下被试设备的响应。数值模拟与理论计算结果比较吻合,被试设备响应迅速达到峰值后逐渐衰减,振动频率由高频向低频过渡,在分析浮动冲击平台舰载设备考核系统长时间响应时需考虑阻尼的影响。     

The coupling dynamical modeling theory of flexible multibody system

Based on the deformation theory of elastic beams, the coupling effect between the coupling displacements of a point on the middle line of beam and large overall motion is presented. The “coupling matrix library” and Jourdain's variation principle and single direction recursive formulation method are used to establish the general coupling dynamical equations of flexible multibody system. Two typical examples show the coupling effect between coupling displacements and large overall motion on the dynamics of flexible multibody system consisting of beams. The project supported by the National Natural Science Foundation of China (No. 19832040).     

TRAJECTORY TRACKING CONTROL AND VIBRATION SUPPRESSION OF SPACE-BASED ROBOT WITH ELASTIC FOUNDATION

讨论了基座存在弹性情况下,载体位置无控、姿态受控的漂浮基空间机械臂惯性空间轨迹跟踪控制及基座弹性振动主动抑制问题。由系统位置几何关系及动量守恒关系,建立了系统运动Jacobi 关系;之后利用拉格朗日方法并结合系统动量守恒关系建立了系统动力学方程。基于奇异摄动理论的两种时间尺度假设,将该方程分解为描写系统刚性运动的慢变子系统与描写系统弹性振动的快变子系统。对慢变子系统设计了基于计算力矩法的轨迹跟踪控制器;对于快变子系统则设计了线性二次最优控制方案。数值仿真证实了提出的控制方法的有效性。     

DYNAMIC RESPONSE OF HIGH SPEED TRAIN MEETING IN OPEN AIR,MEETING IN TUNNEL AND PASSING TUNNEL1)

明线会车、隧道会车和过隧道工况下的气动压力波对高速列车的动力响应和运行安全产生很大影响,本文建立了三辆编组的高速列车动力学模型,通过数值仿真得到了列车在三种工况下的车体所受的气动力,基于数值积分分析了列车的动力响应和脱轨系数。研究发现：明线会车和隧道会车工况相比,车辆的侧向运动相反。 明线会车和过隧道时,气动载荷对列车的脱轨系数影响较小,而隧道会车时,气动载荷作用对尾车的安全性影响较大。     

移动荷载下上覆弹性板饱和地基的动力响应

用半解析法对移动条形荷载作用下上覆弹性板饱和两相弹性介质的动力响应问题进行了研究。由忽略土粒压缩和土体自重的Biot波动方程出发,对荷载进行Fourier展开。假设响应函数形式,利用待定系数法求解了考虑固液耦合作用的两相介质在移动荷载作用下的土体位移,有效应力及孔压表达式。求解过程中考虑了土体和弹性板之间的相互作用,并假设土体与弹性板的竖向位移相等。通过计算给出了各参数对土体位移和孔压响应和的影响。数值结果表明弹性梁刚度对位移和孔压响应有较大影响。     

Rolling of a Heavy Ball in a Spherical Recess of a Translationally Moving Body

The dynamic behavior of a heavy homogeneous ball rolling without slipping in a spherical recess of a translationally moving body is analyzed. The equations of motion of the ball are derived based on Appell's nonholonomic mechanics. The evolution of the dynamic system in time is analyzed numerically.     

Active sloshing control in a smart flexible cylindrical floating roof tank

An exact three dimensional fully-coupled hydro-elastic analysis for transient liquid sloshing in a partially-filled vertically-standing flexible circular cylindrical shell container fitted with a freely floating smart piezo-sandwich thin elastic circular plate is presented. The problem formulation is based on the linear water wave theory, the classical (Kirchhoff/Sanders) thin plate and shell models, Maxwell's equations of electrodynamics, Stokes’ transformation, and eigen-function expansions in cylindrical coordinates. The control action is achieved by combined volume displacement and volume velocity feedbacks (VDF, VVF) implemented in a second order active damping (AD) compensator via two competent evolutionary heuristic optimization techniques that systematically tune the controller gain parameters while constraining the floating panel displacement and control voltage. The uncontrolled and controlled transient responses of the coupled hydro-elastic system under various external disturbances (i.e., a harmonic base excitation, a real seismic event, a severe launch vehicle liftoff event, and a distributed impulsive transverse load on the floating panel) are calculated by means of Durbin's numerical inverse Laplace transform scheme. Moreover, the free vibration characteristics of the coupled fluid/structure interaction (FSI) system are briefly studied. The superior performance of the proposed active floating roof control configuration in effective suppression of the key hydro-elastic parameters (panel displacement, and shell displacements/stresses) is demonstrated. It is also found that, in the current FSI control problem, the Multi-objective Particle Swarm Optimization (MOPSO)-based ADC outperforms the Non-dominated Sorting Genetic Algorithm (NSGA-II)-based method, in terms of convergence rate and computational effort. Limiting cases are examined and the precision of results is verified by comparisons with the existing data as well as with the results produced by a commercial finite element package.     

基于信号分解和切比雪夫多项式的多体系统区间不确定性分析方法

参数的不确定性会对多体系统动力学响应产生显著影响, 区间分析方法只需根据不确定性参数的边界信息, 便可实现在多体系统动力学分析中考虑参数的不确定性. 考虑区间参数不确定性, 采用切比雪夫区间方法(Chebyshev interval method, CIM)在分析多体系统动力学响应时, 随着时间的增大, 响应边界精度会越来越低. 为解决CIM的这一问题, 本文将信号分解技术与切比雪夫多项式结合, 采用切比雪夫多项式分别对HHT变换(Hilbert-Huang transform, HHT)和局域均值分解(local mean decomposition, LMD)得到的瞬时幅值和瞬时相位近似, 提出CIM-HHT方法和CIM-LMD方法, 以获得含区间参数的长周期动力学响应边界. HHT和LMD分解能够将多体系统的多分量响应分解为多个单分量和一个趋势分量(残余分量)之和, CIM-HHT和CIM-LMD对每个分量的瞬时幅值和瞬时相位、和趋势分量采用切比雪夫多项式近似, 进而建立系统响应的耦合模型, 可以得到系统的动力学响应边界. 最后, 考虑单摆和曲柄滑块机构中的参数不确定性, 验证了CIM-HHT和CIM-LMD方法的有效性. 结果表明, 相比CIM, 在长周期区间动力学响应分析中CIM-HHT和CIM-LMD能够获得较准确的结果. 此外, 相比CIM-HHT, CIM-LMD具有更弱的末端效应, 计算精度更高.      

Field tests and theoretical analyses concerning the rolling resistance of a track-laying vehicle due to plastic deformation

Submerged vehicles, especially those with floating tanks, are subjected to rolling resistance due to soil under various vehicle operating conditions, soils, and external forces. It is desirable to obtain simple, general solutions for the peak contact pressure and rolling resistance due to plastic deformation. In this paper, these theoretical analyses for a track-laying vehicle are presented and related to tests on submerged sands.     

Dynamics of dual pontoon floating structure for cage aquaculture in a two-dimensional numerical wave tank

The trend of using floating structures with cage aquaculture is becoming more popular in the open sea. The purpose of this paper is to investigate the dynamic properties of a dual pontoon floating structure (DPFS) when attached to a fish net by using physical and numerical models. A two-dimensional (2-D) fully nonlinear numerical wave tank (NWT), based on the boundary element method (BEM), is developed to calculate the wave forces on the DPFS. The wave forces on a fish net system are then evaluated using a modified Morison equation. The comparisons of dynamic behaviors between numerical simulations and experimental measurements on the DPFS show good agreement. Results also display that a fish net system causes the resonant response of body motions and mooring forces to be slightly lower due to the net's damping effect. Finally, for designing the rearing space of cage aquaculture, the influences which net depth and net width have on the DPFS dynamic responses are also presented in this paper.     

气泡及其破碎兴波对浮动冲击平台影响探究

基于LS-DYNA软件中的ALE算法，对近水面水下爆炸气泡脉动过程进行数值模拟并与实验结果进行对比，验证了近水面近壁面混合边界有限元模型和参数设置的正确性。设置不同爆炸工况，对气泡及其破碎兴波对浮动冲击平台影响进行探究，结果表明:在水下爆炸过程中，气泡、自由面、浮动冲击平台会发生强烈的耦合作用，在气泡脉动阶段，气泡会诱导出涌流和水冢效应，影响浮动冲击平台的安全性和使用性；冲击波是影响浮动冲击平台冲击环境的主要因素，由于气泡的低频性，气泡脉动及水冢对浮动冲击平台的直接冲击作用，会小幅度增加浮动冲击平台冲击环境的谱速度值、谱位移值，对谱加速度值几乎无影响；水冢抨击水面所形成的波浪和气泡破碎兴波，对浮动冲击平台造成的激励载荷呈周期性，其周期与波浪周期相同。波浪的激励载荷仅通过激励其对应频率的浮动冲击平台共振来改变平台的冲击环境。波浪载荷很小，对浮动冲击平台的冲击环境影响较小。