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《江苏科技大学学报(社会科学版)》2017,(5)
在分层流体模型中,两层流体分别以不同的速度平行于界面流动.文中探讨当点涡分别位于上层和下层流体中时,对界面波的影响.当点涡位于上层流体中时,应用势流理论和边界积分方程建立完全非线性的数学模型,构造关于非线性界面波的积分微分方程组,通过基于拟牛顿法的数值方法得到界面波的数值结果.与点涡在下层流体时引起的界面波比较,数值结果显示在等强度的点涡和相同的来流条件下,点涡位于上层流体中所引起的界面波振幅远小于点涡位于下层流体中所引起的界面波振幅,并且它们的振幅比值随着上层和下层流体密度比的增大而增大,但总是小于1. 相似文献
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横向规则波作用下的船舶倾覆 总被引:1,自引:0,他引:1
运用安全池理论研究了某近海干货船在横向规则波作用下的船舶倾覆问题.用阿当姆斯预估-校正法数值求解时域内单自由度非线性横摇方程.采用三维格林积分方程法计算水动力系数的频域特性.分析了非线性横摇方程中势流阻尼、非线性阻尼以及在横向规则波作用下波高和频率对安全池的影响. 相似文献
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文章基于有限体积法,通过控制壁面的波动方式,考察了动波浪壁面对低雷诺数下两自由度弹性支撑圆柱体涡激振动的抑制作用。结果表明:由圆柱两侧向下游行进的壁面波能抑制漩涡的脱落;适当的壁面波动频率能大幅降低圆柱的横向振动;当雷诺数Re=500时,随着约化速度的增大,动波壁圆柱的横向位移值相对标准圆柱体始终维持在较低值区间内(0~0.05D),动波壁圆柱流向位移值相对标准圆柱体的减小幅度逐渐增加。 相似文献
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管道系统在船舶行业中应用广泛,其振动及声辐射特性一直以来都是研究的热点.基于Timoshenko梁理论,本文首先利用传递矩阵法计算了单根充液管道的横向振动响应,并通过有限元计算和实验对比验证了计算方法.在此基础上,对管道系统的传递矩阵取特征值得到波传播参数,从而进一步分析了周期支撑的充液管道系统的振动波传递特性.由本文的计算结果可见,基于Timoshenko梁理论的横向振动响应比基于Euler-Bernoulli梁理论的结果更为精准,尤其是在较高频域内.此外,弹性支撑的刚度和间距会影响波阻和波传播带.本文工作将为周期支撑管系的减振提供一定的技术参考. 相似文献
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海上地震勘探中资料多次波的消除主要采用预测反褶积,也有采用诸如模式匹配和多域滤波等替代技术,这些技术的优势在于它们对预测出的多次波振幅的依赖较小.许多研究表明,没有一种方法是在所有情况下都能有效压制多次波的.模式匹配和多域滤波的消除技术在压制多次波的同时也衰减了有效信号.针对海底电缆资料的特点,目前多采用波场分离、双检求和技术来消除其中的多次波,而且获得了较好的效果.此项技术的关键是在如何求和上.叙述了海上多次波干扰与海底电缆地震资料的特点以及其处理特点,针对上述的特点介绍了相关的海底电缆资料多次波衰减方法,重点描述了一种新的消除多次波的求和方法及其应用实例. 相似文献
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应用相位聚焦技术在船模拖曳水池生成了基于等波陡谱的聚焦波群,采用极点对称模态分解(Extreme-point Symmetric Mode Decomposition,ESMD)方法研究了不同组成波带宽、不同聚焦波幅的聚焦波群的演化特性,重点分析了破碎与非破碎工况聚焦波群波面升高时间历程模态函数的瞬时频率、瞬时振幅和总能量的演化特性,研究发现基于总能量演化的聚焦位置分析可以较为准确地识别非破碎聚焦波群的实际聚焦位置,可以有效地描述聚焦波群发生破碎后继续传播和聚焦的演化过程,这些发现有助于深入理解非线性瞬态聚焦波群的演化特性。 相似文献
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本文研究了深海垂直杆件在波流联合作用下的波激-涡激-参激耦合振动特性.基于Hamilton原理,建立了垂直杆件的三维振动模型,考虑Morison力、涡激力和顶端变张力,对结构的波激-涡激振动和波激-参激-涡激联合振动进行数值模拟,求得杆件各点位移时历曲线,并针对时历曲线进行快速傅里叶变换得到能量频谱,从能量角度分析杆件振动特性.在此基础上,研究了振动幅值随流速、参激频率和参激幅值的变化规律.研究表明:在波流联合作用下,杆件振动出现非线性,轴向振动存在1/2和1/4亚频振动成分,拖曳力方向振动存在二倍波激频率成分;当涡泄频率接近杆件横向振动固有频率时,轴向振动和涡激振动振幅增加;存在参数激励时,杆件三个方向的振幅增大,振动对流速更加敏感;参激频率接近杆件固有频率时,轴向振幅和涡激振幅均增加,而当参激强度增加时,三个方向的振幅均增加,平衡位移不受影响. 相似文献
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《船舶与海洋工程学报》2020,(1)
The launching and recovery process of a human-occupied vehicle(HOV) faces more complex wave effects than other types of submersible operations. However, due to the nonlinearity between the HOV and its mother ship, difficulties occur in theoretically simulating their coupled motion and hydrodynamics. The coupled motion responses and the load under different regular wave conditions are investigated experimentally in this study. The optimized design of the experimental scheme simulated the launching and recovery process of the mother ship and HOV in regular waves. The attitude sensor performed synchronous real-time measurement of the coupled motion between the mother ship and HOV as well as obtained the load data on the coupled motion under different cable lengths. The results show that models in heading waves mainly lead to the vertical motion of the hoisting point. In beam waves, the transverse and vertical motions of the hoisting point occur in a certain frequency of waves.Under the heading and beam wave conditions, the longer the hoisting cable is, the greater the movement amplitude of the submersible is. Moreover, compared with the condition of the beam waves, the hoisting submersible has less influence on the mother ship under the condition of the heading waves. The findings provide theoretical support for the design optimization of the launching and recovery operation. 相似文献
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通过物理试验研究双色波传入细长港池并激发港池低频振荡,合理的试验布局降低了波浪二次反射对造波机的影响问题。利用快速Fourier变换和小波变换方法分析双色波在港内的幅频响应以及波浪能量的时-频分布情况,并利用小波二阶谱分析港内波浪不同成分之间的非线性相互作用过程。结果表明:当双色波短波频率对应港池不同共振频率时,通过波浪非线性相互作用产生的二阶长波在港内响应幅值不同;短波频率对应港池较低共振频率时,波浪会在港内聚集更多的能量;二阶长波以及高次谐波与双色短波之间呈复杂的非线性能量传递过程。 相似文献
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In the present paper,the effect of a small bottom undulation of the sea bed in the form of periodic bed form on the surface waves generated due to a rolling oscillation of a vertical barrier either partially immersed or completely submerged in water of non uniform finite depth is investigated.A simplified perturbation technique involving a non dimensional parameter characterizing the smallness of the bottom deformation is applied to reduce the given boundary value problem to two independent boundary value problems upto first order.The first boundary value problem corresponds to the problem of water wave generation due to rolling oscillation of a vertical barrier either partially immersed or completely submerged in water of uniform finite depth.This is a well known problem whose solution is available in the literature.From the second boundary value problem,the first order correction to the wave amplitude at infinity is evaluated in terms of the shape function characterizing the bottom undulation,by employing Green’s integral theorem.For a patch of sinusoidal ripples at the sea bottom,the first order correction to the wave amplitude at infinity for both the configuration of the barrier is then evaluated numerically and illustrated graphically for various values of the wave number.It is observed that resonant interaction of the wave generated,with the sinusoidal bottom undulation occurs when the ratio of twice the wavelength of the sinusoidal ripple to the wave length of waves generated,approaches unity.Also it is found that the resonance increases as the length of the barrier increases. 相似文献
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文章建立了波浪、海流和船体运动等载荷综合作用下的深水钻井隔水管非线性时域动力响应模型,模型考虑了顶部张力和隔水管内部泥浆对隔水管动力响应的影响,计人了张力沿隔水管长度的变化,并采用有限差分法求解了四阶偏微分运动方程.计算了随机波浪和规则波浪下船体运动对深水钻井隔水管非线性动力响应的影响,研究分析了船体平均偏移以及波频响应和低频响应的周期和幅值对深水钻井隔水管动力响应的影响.结果表明,船体运动对深水钻井隔水管动力响应有较大的影响,在随机波浪和海流作用下,考虑船体运动时,隔水管上部最大弯矩增大了59%.船体的平均偏移主要影响底部最大弯矩.船体波频运动对上部最大弯矩有较大影响,随着波频响应的周期和幅值的变化,上部最大弯矩变化较快,而低频响应的则主要影响隔水管上部弯矩. 相似文献
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Considering the static stability and the change of the displacement volume, including the influences of higher order nonlinear terms and the instantaneous wave surface, the nonlinear coupled heave-pitch motion was established in stochastic waves. The responses of heave-pitch coupling motion for the Truss Spar platform were investigated. It was found that, when the characteristic frequency of a stochastic wave is close to the natural heave frequency, the large amplitude pitch motion is induced under the parametric-forced excitation, which is called the Mathieu instability. It was observed that the heave mode energy is transferred to pitch mode when the heave motion amplitude exceeds a certain extent. In addition, the probability of internal resonant heave-pitch motion is greatly reduced while the characteristic wave frequency is away from the natural heave frequency. 相似文献
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This study investigates the freak wave impinging on a tension-leg platform through wave flume experiments. The freak waves are generated using the focused wave theory. By adjusting the wave focusing location, different incident wave scenarios at the structure location are produced. Simultaneous measurements of wave shape evolutions upon impingement, wave impact pressures on the platform deck, platform motions and tether forces are carried out for synchronized analyses of the wave kinematics/dynamics and structural responses. The variation of these parameters with the incident wave profile is studied. It is found that although applying less intensive local impact pressures as compared to the highly-breaking freak wave, the slightly-breaking or non-breaking freak wave imposes the same level of adverse effect on the platform's global stability in terms of motions and tether forces. In addition, the high-crest freak wave causes violent motions of the floating platform, which are likely to induce snap loads of large amplitude and high occurrence frequency in tethers. The published results would provide useful benchmarks for validating numerical and analytical models. 相似文献