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1.
双曲余弦海脊上海啸俘获波的解析与数值研究 总被引：4，自引：3，他引：1
海啸能被大洋海脊引导以俘获波的形式沿其传播上万千米，且因其特殊的运动方式，携带巨大能量影响远场地区的港口，严重威胁海岸安全。本文首先基于线性浅水方程，推导了双曲余弦平方海脊上俘获波的波面解，其为μ阶ν次的连带勒让德函数的第一类解和第二类解的组合。进一步推导出其对应的频散关系，其中对于确定的频率ω，存在无穷多个波数ky与之对应。采用MIKE21-BW模型，模拟了产生于海脊脊顶处的海啸在理想双曲余弦平方海脊上的传播变形过程。结果表明，小部分能量以自由先驱波进行传播，海啸波的波能大部分被海脊俘获。海脊俘获波沿着海脊方向为行进波，随着海啸波传播时间的增加，波浪在沿着海脊方向的延展范围也逐渐增大，波高逐渐减小、波的个数逐渐增加。俘获波能量主要由不同频率以相同速度传播的具有孤立波特性的波浪成分和能量主要集中在特定频率范围内的波浪成分组成。 相似文献
2.
越洋海啸会受大洋海脊的引导以俘获波的形式沿其传播上万千米,其携带的巨大能量会严重影响远场地区、威胁海岸地区的安全。本文基于MIKE21-BW模型,分别模拟0°(直海脊)至90°(直角弯曲海脊)不同弯曲角度海脊上俘获波的传播变形过程,并定量比较其能量分配。结果表明,海脊俘获波传至海脊转弯处,少部分能量会泄露出海脊重新以自由波的形式扩散至整个海域;部分能量会被反射回来形成与初始海啸波相反方向的俘获波沿海脊传播,反射的能量会随着海脊弯曲角度的增加而增加;还有一部分能量继续沿着弯曲的海脊向前传播,其随着海脊弯曲的角度增加而减小。 相似文献
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当波浪传播至近岸浅水区时易发生破碎,波浪破碎后水体直接拍击单桩结构,其波浪作用力显著增大,可能导致结构失稳破坏。首先建立包括斜坡海床的数值波浪水槽,并与已有研究进行对比验证。进而开展考虑斜坡海床可渗透性的孤立波数值模拟,分析孤立波传播与浅水化破碎特征,着重研究竖直单桩上破碎波浪力的特性,及其与单桩位置、海床渗透率的关联性。数值研究发现:对于低渗透率海床,随着单桩位置由深水向岸线位置变动,其所受波浪力先增后减,所受波浪力最大的桩体位置随海床渗透率增加而从波浪破碎点前方移动至破碎点后1D处,而在高渗透率海床上不同位置处桩体所受波浪力均较小;随海床渗透率等梯度增加,海床消波作用逐渐增强,波浪破碎进程延缓,波浪破碎点向岸线方向加速移动,单桩上破碎波浪力呈整体下降趋势,但可能因波浪破碎点的位置变动导致部分位置桩体所受波浪力异常增大。 相似文献
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珊瑚岛礁海岸波流动力复杂、地貌形态特殊、工程响应未知, 波浪传播变形和波生环流对建筑物安全、地形地貌演变、防灾减灾和生态环境保护都有重要影响。本文从大范围大洋海脊导波与岛礁波浪俘获、中等尺度的礁坪-潟湖-裂口系统波流特性、建筑物前沿的局部波流特性及工程响应等三种不同空间尺度上综述了波流运动特性研究的新进展, 主要包括深水大范围的海脊波浪引导与岛礁波浪俘获的理论解析、礁坪-潟湖-裂口系统整体物理模型实验、基于大水槽实验的建筑物影响下波流演化过程及越浪量和波浪力计算方法, 并提出亟需深入研究的重点内容。 相似文献
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采用能量聚焦的方式产生深水破碎波,并通过增加输入波陡使发生不同强度的波浪破碎现象。实验中,沿水槽中心位置布置22个浪高仪,分析波浪传播过程中的波面演化特征。对水槽不同位置处波面数据进行波能谱与小波能谱分析,发现在聚焦波传播过程中,低频能量部分保持相对稳定,而一次谐波高频部分先逐渐拓宽,经过破碎区域后又逐渐恢复。能量在高频部分有所损失,这种现象在破碎时更加明显,且破碎强度越大,越显著。波浪未破碎时,由于波浪传播过程中高频部分拓宽,导致聚焦前后特征频率略有增加,特征群速和特征周期略有减小;当波浪破碎时,由于破碎导致的能量损失比较明显,且卷破时更加明显,导致破碎后特征频率减小,特征群速和特征周期增大。 相似文献
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越洋海啸能够被大洋海脊引导并沿海脊传播至远场地区，虽然传播速度较慢，但携带较大的能量，会对远场地区造成灾害影响，相关研究对于提高海啸传播特性本质的认识具有重要意义。本文基于线性长波方程，推导出了抛物型对称海脊引导波完整解析理论。研究表明对称型海脊同时存在对称与反对称引导波，其自由水面波动可以表示为虚宗量Bessel函数形式。利用海脊中心对称条件给出了描述其频率与波数的频散关系。基于所提理论进一步分析讨论了引导波的运动特性，包括频散关系、波速度、能量传播速度与波面空间分布等。本研究为揭示地形坡度由脊顶至两侧逐渐增加的海脊引导波运动特征，预测实际越洋海啸中最具威胁性海啸波的到达时间提供了理论依据。 相似文献
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通过测试一系列不规则波工况研究了防浪建筑物存在下珊瑚礁海岸附近短波、低频长波和增水的变化规律，并对比了防浪建筑物的不同位置情况。分析结果表明：波浪在沿礁传播过程中，短波波高沿礁坪持续衰减，低频长波波高沿礁坪逐渐增大，波浪增水则沿礁坪基本保持不变；海岸附近短波随着防浪建筑物与礁缘距离的变大而减小，低频长波则在防浪建筑物处于礁坪后部时达到最大，防浪建筑物位置的变化对于礁坪波浪增水的影响可以忽略。通过理论分析证明了珊瑚礁地形上低频长波是由于群波破碎造成的破碎点移动而产生的；当特定波况作用于特定位置的防浪建筑物时，低频长波在礁坪上会发生一阶共振效应导致其能量在海岸附近达到最大值。 相似文献
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结合椭圆型缓坡方程模拟近岸波流场 总被引：6，自引：3，他引：6
波浪向近岸传播的过程中,由波浪破碎效应所产生的近岸波流场是近岸海域关键的水动力学因素之一.结合近岸波浪场的椭圆型缓坡方程和近岸波流场数学模型对近岸波浪场及由斜向入射波浪破碎后所形成的近岸波流场进行了数值模拟.计算中考虑到波浪向近岸传播中由于波浪的折射、绕射、反射等效应使局部复杂区域波向不易确定,采用结合椭圆型缓坡方程所给出的波浪辐射应力公式来计算波浪产生的辐射应力,在此基础上耦合椭圆型缓坡方程和近岸波流场数学模型对近岸波流场进行数值模拟,从而使模型综合考虑了波浪的折射、绕射、反射等效应且避免了对波向角的直接求解,可以应用于相对较复杂区域的近岸波流场模拟. 相似文献
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波浪作用下海底斜坡滑动稳定性分析中,一般未考虑海底坡度引起的波浪浅水效应,即不考虑波浪在斜坡面上的变形导致的波压力变化,降低了其计算结果的可靠性。本文基于沿斜坡面传播的线性波浪理论,考虑波浪的浅水效应,利用波浪与重力作用下海底斜坡的有效应力场,计算海底斜坡滑动稳定性安全系数。在验证海底斜坡滑动稳定性计算结果可靠性的基础上,分析了坡度对海底斜坡瞬态波浪响应及其滑动失稳特征的影响。结果表明,由于波浪沿斜坡面传播的浅水效应,相对于水平海床,波浪作用下斜坡最大瞬态应力和孔隙水压力随着坡度的增加基本呈线性增加趋势,最大水平位移呈非线性增加趋势;相比于坡底水平段海床的滑动区,斜坡面上滑动区的深度和水平方向滑动范围均有所增加,且坡度越大,这种效应越显著;相比于饱和海床,非饱和条件下,坡度对斜坡体滑动特征的影响程度有所降低。 相似文献
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Based on the linear shallow water equations,an analytic solution of trapped waves over a symmetric parabolicprofile submerged ridge is derived.The trapped waves act as propagating waves along the ridge and as standing waves across the ridge.The amplitude gets the maximum at the ridge top and decays gradually towards both sides.The decaying rate gets more gently with higher modes.Besides,an explicit first-order approximate dispersion relation is derived to simplify transcendental functions in the exact solution,which is useful to describe trapped waves over shallowly submerged ridges in reality.Furthermore,the trapping mechanism of the submerged ridge waveguides on the trans-oceanic tsunami propagation can be explained by the ray theory.A critical incident angle exists as a criterion to determine whether the wave is trapped.Besides,a trapped parameter γ is proposed to estimate the ratio of the energy trapped by the oceanic ridge if a tsunami is generated at its top. 相似文献
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This paper investigates wave-by-wave control of a wave energy converter using incident wave prediction based on up-wave surface elevation measurement. The goal of control is to approach the hydrodynamically optimum velocity leading to optimum power absorption. This work aims to study the gains in energy conversion from a deterministic wave propagation model that accounts for a range of group velocities in deriving the prediction. The up-wave measurement distance is assumed to be small enough to allow a deterministic propagation model, and further, both wave propagation and device response are assumed to be linear. For deep water conditions and long-crested waves, the propagation process is also described using an impulse response function (e.g. [1]). Approximate low and high frequency limits for realistic band-limited spectra are used to compute the corresponding group velocity limits. The prediction time into the future is based on the device impulse response function needed for the evaluation of the control force. The up-wave distance and the duration of measurement are then determined using the group velocity limits above.A 2-body axisymmetric heaving device is considered, for which power capture is through the relative heave oscillation between the two co-axial bodies. The power take-off is assumed to be linear and ideal as well as capable of applying the necessary resistive and reactive load components on the relative heave oscillation. The predicted wave profile is used along with device impulse response functions to compute the actuator force components at each instant. Calculations are carried out in irregular waves generated using a number of uni-modal wave spectra over a range of energy periods and significant wave heights. Results are compared with previous studies based on the use of instantaneous up-wave wave-profile measurements, both without and with oscillation constraints imposed. Considerable improvements in power capture are observed with the present approach over the range of wave conditions studied. 相似文献
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本文基于真实地形、潮汐的高分辨率三维MITgcm海洋环流模式，对南海北部a波（大振幅波列形式）和b波（孤立子形式）的生成与传播特征进行了数值研究。首先，我们总结和分析了这些波动的生成与传播特征。然后我们计算了吕宋海峡的能量收支。能量的生成在一天内有三个极大值，其中最大值对应a波的生成。吕宋海峡西边界的能通量一天内有两个极大值，较大的那个对应a波的生成而另一个对应b波的生成。我们设计了敏感性试验来探究吕宋海峡东西海脊对a、b波的生成和传播造成的影响。通过对比敏感性实验和标准试验的结果，发现对于a波的生成东海脊必不可少，但西海脊几乎没有影响。西海脊削弱了a波的振幅但未对a波波速造成明显的影响。b波来自于从东海脊生成的扰动信号。西海脊加强了这个扰动信号但减慢了它的传播速度。 相似文献
14.
Hui Qian Ping-Tung Shaw Dong Shan Ko 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(12):1521-1531
A three-dimensional nonhydrostatic numerical model is used to study the generation of internal waves by the barotropic tidal flow over a steep two-dimensional ridge in an ocean with strong upper-ocean stratification. The process is examined by varying topographic width, amplitude of the barotropic tide, and stratification at three ridge heights. The results show that a large amount of energy is converted from the barotropic tide to the baroclinic wave when the slope parameter, defined as the ratio of the maximum ridge slope to the maximum wave slope, is greater than 1. The energy flux of internal waves can be normalized by the vertical integral of the buoyancy frequency over the ridge depths and the kinetic energy of the barotropic tides in the water column. A relationship between the normalized energy flux and the slope parameter is derived. The normalized energy flux reaches a constant value independent of the slope parameter when the slope parameter is greater than 1.5. It is inferred that internal wave generation is most efficient at the presence of strong upper-ocean stratification over a steep, tall ridge. In the Luzon Strait, the strength of the shallow thermocline and the location of the Kuroshio front could affect generation of internal solitary waves in the northern South China Sea. 相似文献
15.
Numerical analyses for the Bragg resonant reflection of carrier waves associated long waves due to sinusoidally varying seabeds are performed by using a set of coupled ordinary differential equations derived from the Boussinesq equations. The Boussinesq equations are firstly approximated with the Fourier decomposition. The coupled governing equations are then derived and used to simulate evolution of both short and long wave components. It is also found that wave groups are generated by two carrier waves with slightly different frequencies. The wave energy of the initial wave components is transferred to other harmonic components during propagation over a long distance. Evolution and reflection of both short and long waves were largely affected by nonlinearity. 相似文献
16.
An investigation undertaken recently by the Division of Regional Geoecology and Marine Geology of the Karpinsky All-Russian
Research Geological Institute in the coastal zones of the Eastern Gulf of Finland allowed finding some specific relief forms
of both near-shore bottom topography and shoreline shape. First of all, among the most interesting objects, the sand ridges
on the surface of submarine terrace (between Repino locality and Cape Lautaranta) should be mentioned. These ridges are elongated
at an angle to the shoreline and are located beyond the limits of wave action. The other interesting morphological type is
represented by longshore sand waves up to some hundreds of meters long and some tens of meters wide near the Bol’shaya Izhora
locality. Longshore sand waves move along the southern coast of the gulf, this causing alteration of erosion and accretion
zones and leading to formation and degradation of the sand spits. Shore-face-connected ridges are believed to develop under
the action of drift currents generated during the passage of deep west cyclones. It is shown that the ridge turned toward
the current gives rise to a convergence of the cross-shore flows over the crest and provokes a shift of the maximum velocity
toward the front side of the structure. Associated changes in sediment discharges result in accumulation and growth of the
ridge. The origin of wavelike features in the shoreline contour (longshore sand waves) is due to a very oblique wave approach
caused by predominance of the west winds blowing along the axis of the gulf. Under these conditions a small perturbation of
the shoreline contour is shown to manifest a trend to increase with time. 相似文献
17.
Akio Maeda 《Journal of Oceanography》1971,27(4):163-174
Phase velocity of semi-diurnal internal waves is determined from differences between phases at three stations which were situated to form a triangle in the vicinity of sta. T (29N, 135E). The wave phases are estimated from temporal variations in depths of isotherms obtained from serial measurements of vertical temperature profiles at these stations. The measurements were carried out in cooperative operation of two vessels, the R. V.Tansei-maru and theNojima, during the period from 30 July to 1 August 1965. Wave propagation with the speed of about 2 m/s in the direction from east to west is obtained as an average over several isotherms of temperature from 19C to 23C. The area of measurement is to the west of Izu-Mariana ridge and the distance from the ridge to the station is about 500 km, which would be about 5 times as large as the wave length of the internal waves under consideration, and so it is possible to suppose that the internal waves observed generated at the ridge and propagated to the area without being subjected to serious refraction, scattering, reflection and decay. 相似文献