共查询到18条相似文献，搜索用时 359 毫秒
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为了解极端波浪非线性特征,明确波群在演化过程中的水动力学特性,针对一系列高斯波群进行了深水物理试验分析。试验结果显示,增加波陡或波群宽度,均可使波面偏度Sk发生明显变化,尤其当波浪发生破碎后,在破碎区域内,波面偏度变化范围剧烈增大,说明该偏度极大值可能作为判断破碎的一个指标。波陡和波群宽度对波面不对称度影响程度不同:当波陡或波群宽度增加后,波峰不对称度所受影响最大,波峰前端波谷不对称度次之,波峰后端波谷不对称度所受影响最小,但仍不可忽略。在波浪演化过程中,幅值谱出现不同程度频带下移,波浪破碎后,会出现永久频带下移;当调制不稳定发生时,随着调制不稳定指数增加,频带下移量呈现快速增长趋势。 相似文献
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本文将小波分析用于波群结构和波群中波破碎的研究。实验结果表明,波群中波动的振幅不是关于波群中央对称的,而是波群前部波动的振幅较大。这种不对称性导致波群前部单个波的波陡较大,后部单个波的波陡较小,当谱宽度增大时波群前部与后部单个波的平均波陡之差增大。波群前部波陡较大导致波群前部的波动最容易发生破碎,而不是波群中央的波动最容易发生破碎,波群中波动最可能发生破碎的位置距波群中央的长度为波群长度的1/6。 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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了解波浪破碎速度场的分布特性对于波浪破碎物理机制的研究极为重要,同时,对比研究不同类型破碎产生的气液混合区的演化特征有利于波浪白冠覆盖率模型的完善。在实验室水槽,生成了深水临界波、单次崩破波和单次卷破波,采用图像测速技术获取了波浪破碎图像、波面下水体和气液混合区速度场。结果表明,崩破波的水平向速度u和垂直向速度v在波峰前和波峰后的分布极为不对称,其水平向最大速度umax并不位于峰顶,而是在主导波峰前0.7ηm ax处;卷破波的umax出现在波峰峰顶前端极小的区域内,且该区域与周围区域的速度梯度极大。崩破波和卷破波生成的气液混合区发展特征也存在差异：崩破波的umax值大、影响区域长、混合区厚度较小、各区域影响时间短;而卷破波的各项特征参数与崩破波形成对比。 相似文献
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群发性是风浪破碎的显著特征,最近的研究表明风浪破碎研究应该基于波群而不是单个波。本文探讨破碎波群区别于非破碎波群的显著特征指标。依据一系列风浪破碎实验数据,采用多种判据与实验现场目测的破碎标记信号相结合的原则划分破碎波群与非破碎波群,考查波群特征量、单个波几何特征量、局地破碎判据指标、波包络几何特征量以及波群能量结构特征量等5大类28个指标在破碎波群与非破碎波群上的分布差异。结果表明:波陡、峰前波陡、瞬时波面斜率、运动学判据指标和动力学判据指标等在破碎非破碎波群上的分布几乎没有交叠;后两者尤为理想,分布明显分离,是破碎波群区别于非破碎波群的显著指标;而其它各指标在破碎波群非破碎波群上的分布都有不同程度的交叠,不能单独依据它们区分破碎波群与非破碎波群。 相似文献
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浅水破碎波对直立圆柱作用力的试验研究 总被引：2，自引：0，他引：2
分析了桩柱破波力的构成特性,认为破碎波与桩柱作用过程中在不完全绕流区将出现由于附连质量迅速变化引起的冲击力和柱前后波面高度差引起的附加压差力;影响破碎波对直立圆柱作用力的因素应该包括确定破波特性的水底坡度i、入射深水波陡H_0/L_0及代表圆柱对破波作用影响的相对柱径D/H_0。通过从i=1/100到1/15五种底坡上桩柱破波力的系统试验,探索了桩柱破波力的作用特性,归纳了计算桩柱破波力的经验公式。 相似文献
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内波是海洋中普遍存在的波动形式。内孤立波是典型的非线性内波,多发于陆架边缘海,如南海等海域,对陆架海域有重要影响。本文针对内孤立波在陆架地形上的传播问题,先基于弱非线性与全非线性数值模型,模拟了不同振幅、地形高度条件下内孤立波的演化的过程,探讨了动力系数对内孤立波演化过程的影响,对比了两模型的模拟结果在内孤立波演化过程、能量分配以及能量耗散的差异,后分析了南海的动力系数分布特征。结果表明,在内孤立波不发生破碎的情况下,弱非线性模型与全非线性模拟结果相近。当发生破碎过程时,弱非线性模型可准确模拟头波,但无法通过强非线性的破碎过程耗散能量,只能以裂变的方式辐射能量。在弱非线性模型中,随地形高度增加,频散系数减小到零,平方非线性系数由负转正,立方非线性系数绝对值增大一个量级,并主导陆架地形上内孤立波的演化过程。通过对比南海夏季与冬季非线性内波动力系数空间分布,发现内孤立波在传播过程由于夏季平方非线性效应、立方非线性效应与频散效应较强的影响,其在夏季更易发生陡化与裂变,波列发生频率高。 相似文献
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在实际海况中,由于波浪组分方向不同,使海浪常表现为三维短峰波,与二维长峰波相比,有诸多异同特征。为了研究三维畸形波生成和演化过程中异常大波的外部特征以及大波间的关联,本文采用色散和方向聚焦方法在物理水池中模拟了短峰畸形波的整个生成和演化过程。研究结果表明,生成和演化过程中出现的异常大波沿着方向分布函数峰值方向演化,具有一定程度“对称”特征;根据异常大波的特征参数可将该过程分成3～4个典型的阶段,这意味着可以根据异常大波的特征参数判断其所处阶段及预测其演化趋势;三维畸形波生成和演化过程可能会跳过“波群”或者“深谷”阶段,与二维畸形波相比,时-空范围较小,这意味着在三维波浪场中,与畸形波相关的深谷和波群的发生概率较低。 相似文献
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粤东后江湾近岸长重力波特征分析 总被引：2，自引：0，他引：2
利用粤东后江湾近岸有限水深(包括碎波带)4个测点的压力波数据,依据波谱分析方法对4个测点的入射波有效波高、长重力有效波高、有效波陡、波面谱、谱宽度和谱尖度参量进行了统计和对比分析.分析认为,在近岸有限水深条件下,波浪由近岸(相对水深0.201)到破、碎波带运动过程中,(1)长重力波有效波高呈增大趋势,至破、碎波带位置增幅最为明显;(2)入射波有效波高至破、碎波带区域达到最大,在破波带外有限水深区域呈现先增大后减小的变化趋势;(3)有效波陡、谱宽度参数呈增大趋势;(4)波浪内部能量向高、低频段发生转移,至破、碎波带区域转移程度最为明显,在峰值频率的高、低频段形成谱峰;长重力波谱强度在破、碎波带区域明显高于对应有限水深测点. 相似文献
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Experimental Investigation on the Extreme Waves Induced by Single Wave Packets in Finite Water Depth
Single Gaussian wave groups with different initial wave steepness ε_0 and width N are produced in laboratory in finite depth to study the nonlinear evolution, the extreme events and breaking. The results show that wave groups with larger ε_0 will evolve to be several envelope solitons(short wave groups). By analyzing geometric parameters, a break in the evolution of the wave elevation and asymmetric parameters after extreme wave may be an indicator for the inception of refocus and the maximal wave moving to the middle, namely, wave down-shift occurs. The analysis of the surface elevations with HHT(Hilbert-Huang Transform), which presents the concrete local variation of energy in time and frequency can be exhibited clearly, reveals that the higher frequency components play a major role in forming the extreme event and the contribution to the nonlinearity. Instantaneous energy and frequency in the vicinity of the extreme wave are also examined locally. For spilling breakers, the energy residing in the whole wave front dissipates much more due to breaking, while the energy in the rear of wave crest loses little, and the intra-wave frequency modulation increases as focus. It illustrates that the maximal first order instantaneous frequency f_1 and the largest crest tend to emerge at the same time after extreme wave when significant energy dissipation happens, and vice versa. In addition, it shows that there is no obvious relation of the CDN(combined degree of nonlinearity) to the wave breaking for the single Gaussian wave group in finite water depth. 相似文献
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文章基于长乐海滩前滨剖面的实测波浪数据, 通过统计分析以及谱分析的方法, 探讨了潮汐过程中长乐海滩波浪参数及耗能过程的变化规律。结果表明, 观测期间内波浪以混合浪为主, 各测点谱型较宽, 存在多峰振荡现象。向岸传播过程中, 波能耗散的形式为窄频域向宽频域转变, 能量分布趋于分散, 高频波能减小, 低频波能反而有所上升, 波浪破碎后生成长重力波。破波带内的能量衰减与波浪传播距离具有良好的相关性, 破碎波能在破波带内大约衰减了98.3%。潮汐水位对波浪具有明显的调制作用。入射波能随潮汐水位的增加而有所增加, 且水位越高, 入射波能分布越分散。破波带内的有效波高和潮汐水位具有显著的正相关关系。潮汐过程中固定测点的波谱变化与波浪沿剖面的波谱变化具有明显的相似性。 相似文献
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《Applied Ocean Research》2004,26(3-4):137-146
A theoretical approach is applied to predict the propagation and transformation of nonlinear water waves. A semi-analytical solution was derived by applying an eigenfunction expansion method. The solution is applied to analyze the effect of wave frequencies and wave steepness on the propagation of nonlinear waves. The main attention is paid to the wave profile, the wave energy spectrum, and the changes of wave profile and energy spectrum due to the interaction of wave components in a wave train. The results show that for waves of low steepness the nonlinear wave effects and effects associated with the interaction of water waves in a wave train are of secondary importance. For waves of moderate steepness and steep waves the effects associated with the interactions between waves in a wave train are becoming significant and a train of initially sinusoidal waves may drastically change its form within a short distance from its original position. The evolution of wave components has substantial effects on the wave spectrum. A train of initially very narrow-banded waves changes its one-peak spectrum to a multi-peak one in a fairly short period of time. Laboratory experiments were conducted in a wave flume to verify theoretical approaches. The free-surface elevation recorded by a system of wave gauges was compared with the results provided by the semi-analytical solution. Theoretical results are in a fairly good agreement with experimental data. A reasonable agreement between theoretical results and experimental data is observed often even for relatively steep waves. 相似文献
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In this paper,flume experiments are focused on sediment transport inside and outside the surf zone.According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump,formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves.Assuming that the sediment diffusion coefficient,which is related with energy dissipation,is proportional to water depth,formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves,and the prediction shows a good agreement with the measurement. 相似文献
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A numerical wave tank is used to investigate the onset and strength of unforced wave breaking, and the waves have three types of initial spectra： constant amplitude spectrum, constant steepness spectrum and Pierson-Moscowitz spectrum. Numerical tests are performed to validate the model results. Then, the onset of wave breaking is discussed with geometric, kinematic, and dynamic breaking criteria. The strength of wave breaking, which is always characterized by the fractional energy loss and breaking strength coefficient, is studied for different spectra. The results show how the energy growth rate is better than the initial wave steepness on estimating the fractional energy losses as well as breaking strength coefficient. 相似文献
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A numerical wave tank is used to investigate the onset and strength of unforced wave breaking, and the waves have three types of initial spectra: constant amplitude spectrum, constant steepness spectrum and Pierson-Moscowitz spectrum. Numerical tests are performed to validate the model results. Then, the onset of wave breaking is discussed with geometric, kinematic, and dynamic breaking criteria. The strength of wave breaking, which is always characterized by the fractional energy loss and breaking strength coefficient, is studied for different spectra. The results show how the energy growth rate is better than the initial wave steepness on estimating the fractional energy losses as well as breaking strength coefficient. 相似文献
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The substructures of offshore wind turbines are subjected to extreme breaking irregular wave forces. The present study is focused on investigating breaking irregular wave forces on a monopile using a computational fluid dynamics (CFD) based numerical model. The breaking irregular wave forces on a monopile mounted on a slope are investigated with a numerical wave tank. The experimental and numerical irregular free surface elevations are compared in the frequency-domain for the different locations in the vicinity of the cylinder. A numerical analysis is performed for different wave steepness cases to understand the influence of wave steepness on the breaking irregular wave loads. The wave height transformation and energy level evolution during the wave shoaling and wave breaking processes is investigated. The higher-frequency components generated during the wave breaking process are observed to play a significant role in initiating the secondary force peaks. The free surface elevation skewness and spectral bandwidth during the wave transformation process are analysed and an investigation is performed to establish a correlation of these parameters with the breaking irregular wave forces. The role of the horizontal wave-induced water particle velocity at the free surface and free surface pressure in determining the breaking wave loads is highlighted. The higher-frequency components in the velocity and pressure spectrum are observed to be significant in influencing the secondary peaks in the breaking wave force spectrum. 相似文献
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A. K. Laing 《新西兰海洋与淡水研究杂志》2013,47(4):541-553
A model is described for hindcasting or forecasting waves in finite‐depth waters. The model is particularly applicable to coastal sites where the water is depth‐limited. The wave energy density spectrum is modelled in the frequency‐directional domain. For each spectral component a ray is defined along which wave energy propagates to reach the site. For sites exposed to the open ocean a background spectral wave model is required to provide input to the ray endpoints. Further growth and dissipation is then effected along the rays according to the local wind and water depth. The model was used to hindcast wave spectra over a period of 9 months for a site in the Canterbury Bight, New Zealand. The results were compared with measurements from a Waveridcr buoy at the site. The model succeeds in explaining about 40% of the variance in measured significant wave heights. However, the present application is handicapped by errors inherent in the background spectral model and in specifying the local wind. 相似文献