浸没在流场中的双壳结构波动特性

以浸没在流体声介质中的双层圆柱壳为研究对象,给出了静压下双壳流固耦合系统频散方程,基于Muller-Newton法和围线积分法分别开展了实数域和复数域频散方程的计算。探索了静水压力对双壳频散特性和输入功率流的影响规律。在此基础上,分析了不同周向模态下双壳结构波的传递性质。结果表明:4.5 MPa静水压力降低了高阶周向模态下低阶波的传播速度;在n=0时静水压力增大了输入功率流的峰值;各种传播波随着无量纲频率的增加表现为弯曲波、拉伸波和扭转波等形式。     

多源激励下浮筏功率流特性的有限元分析

以船用浮筏为研究对象,在有限元方法的基础上,提出了利用四端参数法计算输入上层隔振器功率流、利用导纳法计算输入基座功率流的研究方法,并结合单自由度隔振系统验证了方法的准确性。利用该方法计算分析了扰动特性相同以及扰动特性不同的两设备激励力间的相位关系对输入基座功率流的影响。计算结果表明当设备的扰动特性相同时,相位关系对功率流的影响较为复杂,且影响不容忽视;当相位差为π时对应的低频段功率流最小。当两设备的扰动特性不同时,相位关系对输入基座功率流的影响取决于每台设备的激励谱与该台设备单独工作时隔振效果的综合。     

浮筏隔振系统功率流的矢量四端参数方法

针对多输入多输出的复杂浮筏隔振系统,建立了多方向耦合振动传递的矢量四端网络参数模型.给出了浮筏各个子结构的矢量四端网络参数矩阵,为浮筏隔振系统各个层面的振动传递和噪声预报提供了工程估算方法.通过具体算例,数值分析了浮筏各子系统结构参数变化对基座输入功率的影响.使用该方法可以方便地得到浮筏隔振系统各个层面的振动和噪声功率特征参量,并可推广到结构更加复杂的振动系统的计算分析.     

一种П型结构CLC功率谐振逆变器

本文介绍了一种新型双向电流源П型功率谐振逆变器.运用经典交流分析法,推导了逆变器的电流传输增益和输入/输出功率,讨论了不同开关频率和负载对输出功率的影响,并利用电路仿真验证了所做的理论分析.     

统计能量分析子系统的划分

应用统计能量分析(SEA)计算结构声辐射,子系统划分对计算结果产生影响.将平板和圆柱壳划分为多个子结构,考察子系统划分对计算结果的影响.计算结果表明,吻合频率以上,平板各种子系统划分方式和单块平板计算的辐射声功率差别小于0.1 dB;吻合频率以下,计算的辐射声功率随子系统划分的份数增加而增加,X2Y2划分方式和单块平板有3 dB左右的差别.圆柱壳划分为多个圆柱壳子系统,随轴向划分的增加,划分为多个圆柱壳结果的峰值向高频迁移,1.6 kHz以上频段,轴向划分为10个子圆柱壳,与单个圆柱壳差别为1.8～2.6 dB.     

加肋圆柱壳体的振动功率流

本文研究环肋圆柱壳在周向线分布余弦简谐力激励下由振源输入壳体的功率流及沿壳体传播的功率流,分析了肋骨参数对功率流的作用,结果表明:各内力功率流分量的比例主要取决于激励频率和周向模态,而几乎不受肋骨的影响,除非该肋骨产生了波的衰减域。     

高效E类功放在无线电能传输系统中的应用

功率放大器作为无线电能传输系统的输入功率源,其性能的高低决定了整个电能传输系统的优劣。为了解决传统功率放大器效率较低的问题,设计了一款高效率E类功率放大器。该功放为L型匹配输出,以达到抑制谐波和匹配输出的目的。分析及测试表明,在E类功率放大器中采用高品质因数电感可以有效提高无线电能传输系统的传输效率。     

基于统计能量分析法的高铁轮轨减振降噪研究

为降低高速铁路的振动和噪声,根据统计能量分析方法,建立了轮轨噪声的预测模型.将整个轨道系统划分为:钢轨垂向振动子系统和声空腔子系统；然后建立了子系统间功率流平衡方程；计算了阻尼损耗因子、模态密度和耦合阻尼损耗因子等统计能量参数.在以上理论分析基础上预测了轮轨噪声.结果表明:阻尼损耗因子和机车速度分别增加l倍,则声压级分...     

基于海水环境下ICPT系统电磁耦合器的研究

感应耦合电能传输技术(ICPT)是近来兴起的一种新型电能传输模式。针对深海环境下海流扰动影响ICPT系统传输性能稳定的问题,利用ANSYS有限元仿真软件分析电磁耦合器不同间隙下耦合系数和电感参数随磁芯偏心量的变化趋势。建立含有补偿电容的互感等效电路,计算分析系统谐振情况下系统功率和传输效率的影响因素,仿真研究系统功率和传输效率随输入电压、负载电阻、频率和线圈匝数的变化规律,为提高海水环境下ICPT输系统的优化设计提供参考。     

基于波分析法油膜刚度对轴系扭转振动影响的研究

为确保带减速齿轮箱主推进系统的可靠性,文章对船舶轴系的扭转振动进行了研究。首先根据各组成部件的特点将轴系分解为连续和离散的两个子系统,分别利用波分析法和多自由度系统分析法列出连续子系统的波动形式及离散子系统的振动微分方程,同时考虑了减速齿轮箱油膜刚度的影响。然后根据两子系统连接处的动态平衡和连续条件,建立整个轴系在扭转振动模式下总运动方程,通过求解总方程得到系统的位移响应。该扭转振动分析被应用到某LNG船带减速齿轮箱的轴系振动计算中,通过考虑轴系减速齿轮箱啮合齿面间油膜刚度使轴系扭转振动模型更接近轴系实际运转工况。计算结果显示：随着减速齿轮箱啮合齿面间油膜刚度的增加,最大轴系扭转应力向低转速区域偏移。这对船舶轴系转速禁区的划分产生极大的影响。有助于防止因不良轴系振动计算引起轴系事故的发生。     

考虑流体静压时充液圆柱壳的输入能量流特性

研究了内部流体静压力对充液圆柱壳的受迫振动能量流的影响。静压力作为预应力计入壳体振动方程当中，壳体和流体分别采用Fliigge方程和Helmholtz波动方程。分析了耦合系统在周向线分布余弦载荷下的动态响应．用傅立叶变换和反变换实现空间域与波数域之间的相互转换，采用留数定理求取系统的响应并得到耦合系统的输入能量流。结果表明，周向模态数n=0时，静压力对耦合系统的输入能量流影响很小；n较大时，在中低频下静压力使输入能量流曲线沿频率轴右移，由于输入能量流的峰值点处的频率对应于频散曲线中各支传播波的截止频率，对应传播波的截止频率升高，高频时则基本无影响。随着静压力以及周向模态数的增大，输入能量流受到的影响程度也增大。     

复杂系统误差传递的主次作用分析与控制

系统观测目标误差渗透着系统误差和随机误差,系统误差和随机误差的分离与溯源理论和应用一直是误差分析的难点和热点。文中基于系统误差和随机误差的互相关系与传递特征,提出了以传递函数为基础的误差传递模型,并基于该模型,将复杂系统划分为若干个子系统,分析了各子系统在观测目标误差中的主次作用（ primary and secondary position a-nalysis,PSPA）。算例表明,该理论能够分析得出引起观测误差灵敏度较高的子系统,这对于误差溯源、分析和控制误差,提高观测目标的精度具有一定的指导意义。     

Physical processes in the ROFI regime

The distinctive feature of all ROFI (Regions Of Freshwater Influence) systems is the input of significant amounts of buoyancy as freshwater from river sources. If the spatial scale is unrestricted by coastal topography and stirring is weak, this input tends to drive a coast-parallel flow in which the Coriolis force constrains a wedge of low density water against the coastal boundary. Without frictional effects, this flow is subject to baroclinic instability which induces large meanders and eddies in the flow but in, many ROFIs, the tidal flow induces frictional effects which stabilise the density driven flow.In the absence of the effects of rotation and stirring, the buoyancy input tends to induce stratification through an estuarine circulation in the direction of the gradient. When stirring is applied, by the action of wind, waves or tidal flow, the density current is suppressed but is rapidly re-established when stirring ceases, as in the Linden-Simpson (1988) laboratory tank experiments. In real ROFI systems, a combination of all these processes operates so that the structure of the water column and the flow is the result of a competition between the stratifying influence of buoyancy input and the net stirring effect of the wind, waves and the tides. This competition is more difficult to analyse than the heating-stirring competition, because freshwater buoyancy input is not spatially uniform but enters at discrete sources along the coast and its subsequent spreading has to be determined.While the springs-neaps cycle in tidal stirring imposes a regular fortnightly modulation on vertical mixing, the influence of the wind is irregular and depends, not just on the magnitude of the stress, but also on the direction in which it acts. In some exposed shallow water situations there may also be significant stirring due to waves generated by non-local winds.ROFI systems are further complicated by the action of tidal straining in which differential advection, due to vertical shear in the tide, interacts with the density gradient to generate fluctuations in vertical stability at the tidal frequency which, in some cases, are of sufficient amplitude to switch the water column between stable stratification and vertical density homogeneity each tidal cycle. This straining along with the other ROFI processes have been incorporated into a series of 1-D models to provide a more objective test of the hypotheses about the mechanisms involved. Comparison of model hindcasts with observations indicate that we now have a first-order understanding of the complex behaviour of ROFIs.On a global scale it is clear that ROFIs represent an important component of the shelf-sea environment of particular concern in relation to the impact of pollutant discharges. To date, most studies of ROFI's have concentrated on systems in temperate latitudes but attention needs to be focused on the very extensive ROFIs in tropical regions where most of the world's river discharge enters the ocean. In monsoonal regions, these inputs exhibit strong seasonal modulation which may, in competition with tidal stirring, result in an annual cycle of stratification and the formation of fronts.     

具有高阶导数自由表面边界条件的两层流体无波势和多级的构建（英文）

There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace's equation(or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace's equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential.     

Construction of wave-free potentials and multipoles in a two-layer fluid having free-surface boundary condition with higher-order derivatives

There is a large class of problems in the field of fluid structure interaction where higher-order boundary conditions arise for a second-order partial differential equation. Various methods are being used to tackle these kind of mixed boundary-value problems associated with the Laplace’s equation (or Helmholtz equation) arising in the study of waves propagating through solids or fluids. One of the widely used methods in wave structure interaction is the multipole expansion method. This expansion involves a general combination of a regular wave, a wave source, a wave dipole and a regular wave-free part. The wave-free part can be further expanded in terms of wave-free multipoles which are termed as wave-free potentials. These are singular solutions of Laplace’s equation or two-dimensional Helmholz equation. Construction of these wave-free potentials and multipoles are presented here in a systematic manner for a number of situations such as two-dimensional non-oblique and oblique waves, three dimensional waves in two-layer fluid with free surface condition with higher order partial derivative are considered. In particular, these are obtained taking into account of the effect of the presence of surface tension at the free surface and also in the presence of an ice-cover modelled as a thin elastic plate. Also for limiting case, it can be shown that the multipoles and wave-free potential functions go over to the single layer multipoles and wave-free potential.     

基于自适应噪声抵消的源识别及其相关性研究

对参考输入相关的ANC的基本原理进行推导,通过仿真,对参考输入的相关性和ANC结果精度的关系进行研究。仿真结果表明:在信号信噪比较高的情况下,典型的是弱宽带噪声背景上叠加强线谱情况,参考信号之间的相关性对ANC抵消结果没有太大的影响,水池试验证实了自适应抵消方法应用于计水下航行器源识别分析的可行性。     

基于一个二维修正水弹性方法的集装箱船体梁动态前极限强度评估研究

海上极端波因其巨大的波高常常导致船体的极限破坏。该文提出了一个二维的修正水弹性方法来研究一个集装箱船船体梁在极端波中的动态前极限强度。传统的极限强度评估基于准静态方法,没有动态效应被考虑。而船体在波浪下的动态结构响应是基于水弹性方法,传统的水弹性方法并不能计算船体梁的动态非线性强度。该二维修正的水弹性方法考虑时域波浪和非线性船体梁之间的耦合,将水弹性方法和Smith方法结合,用Smith方法计算船体梁的刚度,而其刚度与船体梁的强度和变形曲率有关。所以该时域的非线性刚度被用于修改水弹性方法里的常数项的结构梁刚度。几组极端波模型被用以产生船体梁的大变形和非线性动态垂向弯矩。文中分别采用修正水弹性方法和普通水弹性方法,通过改变四个重要的极端波参数如极端波最大波高、规则波的波高、波速和波长等来研究其对船体梁船中处的大变形转角和非线性垂向弯矩的影响,通过采用修正的水弹性方法计算得来的结果与水弹性方法计算得来的结果相比较,得到了一些差异和结论。     

不规则波浪在陡坡上非线性传播变形的试验研究

通过试验研究了不规则波浪在一陡坡(1:10)上的传播过程中的非线性特征。为达到研究目的,在试验水槽中以JONSWAP谱为靶谱生成了两组随机波浪。试验结果显示,在坡前常水深区域和坡顶,两种波况下波高分布均符合瑞利分布;但是在变浅区域两种波况的波高分布却不尽相同。应用基于小波变换的二阶相位谱来分析波浪在传播过程中的非线性相位耦合特征,结果表明：随着水深的变浅,波浪的非线性逐渐增强并且参与非线性相互耦合的频率成份也越来越多。通过二阶相位谱发现：随着水深的减小,参与最强的非线性相位耦合频率向高频处移动。另外通过傅立叶频谱、二阶谱以及二阶频谱共同分析陡坡上两组波况下低频波浪的演化情况。     

疲劳载荷作用下焊接点三维线弹性弯曲裂纹路径预测

利用二阶摄动方法研究了疲劳载荷作用下结构线弹性裂纹的弯曲扩展问题并求解了三维动态应力强度因子.利用二阶摄动方法研究了疲劳载荷作用下裂纹路径预测时的应力准则与能量准则之间的关系.就均匀物质而言,在二阶摄动分析理论的框架内,两种准则指明了相同的三维疲劳弯曲裂纹扩展路径.但在具有非均匀断裂韧度的物质中,能量准则优越于应力准则.作为二阶摄动方法的实际运用,研究了焊接结构中疲劳线弹性裂纹的形态特征和弯曲扩展路径问题,综合考虑了诸如远场动态作用应力、焊接残余应力、局部物质衰变以及不同尺寸的缺陷的存在等因素,绘制出疲劳载荷作用下退化区域中裂纹弯曲扩展的临界轨迹曲线.     

基于OpenFOAM开源程序的无反射数值波浪水槽

基于计算流体动力学开源程序OpenFOAM,通过在质量守恒方程中添加质量源来实现域内源造波,结合VOF法捕捉自由表面,并采用阻尼消波,建立了二维无反射数值波浪水槽。算例结果表明,所建立的二维无反射数值波浪水槽可以较好地模拟行进波和立波,并且能够较好地避免边界反射及二次反射。