Wind Wave Growth

A recent formula for the lift force on a low speed wing of circular arc cross-section [1] is adapted to the upward pressure force on the crests of a surface gravity wave propagating in the wind. In both cases, the main feature is the utilization of the air’s compressibility. At and near a wave crest, it is predicted that the air density is increased over the ambient value and that the air density decreases inversely as the square of the upward distance from the radius of curvature of the crest. As a consequence, the air pressure also decreases upward inversely as the square of the same distance. Therefore, an upward pressure force on each crest occurs which presumably will make the crests grow. Growth rates are largest for small wavelengths and large mean slopes of the wave surface. Contrary winds should produce wave growth (not damping) as well as no wind at all.

Analytically Derived Wind Wave Growth Relations

By the use of the 3/2 power law presented by Toba combined with the significant wave energy balance equation forwind wave, wind wave growth at a limited fetch is analytically investigated. The new wind wave growth relations(WWGRs) are analytically derived with sheltering coefficient and wind drag coefficient as parameters. The geometricalaverage of observational values of sheltering coefficient and the arithmetic average of observational values of wind drag co-efficient are applied to determine the new WWGRs. Comparisons with existing empirical WWGRs are made.

The Fractional Power Law of Wind Wave Growth in Deep Water for Short Fetch

Combining the 3/2 power law proposed by Toba with the significant wave energy balance equation for wind waves, wave growth in deep water for short fetch is investigated. It is found that the variations of wave height and period with fetch have the form of power function with fractional exponents 3/8 and 1/4 respectively. Using these exponents in the power functions and through data fitting, the concise wind wave growth relations for short fetch are obtained.

Spatial evolution equation of wind wave growth

Based on the dynamic essence of air-sea interactions, a feedback type of spatial evolu-tion equation is suggested to match reasonably the growing process of wind waves. This simple equation involving the dominant factors of wind wave growth is able to explain the transfer of en-ergy from high to low frequencies without introducing the concept of nonlinear wave-wave interac-tions, and the results agree well with observations. The rate of wave height growth derived in this dissertation is applicable to both laboratory and open sea, which solidifies the physical basis of using laboratory experiments to investigate the generation of wind waves. Thus the proposed spa-tial evolution equation provides a new approach for the research on dynamic mechanism of air-sea interactions and wind wave prediction.

NEW WIND WAVE GROWTH RELATIONS

In the present paper combining the relationship between wave steepness and wave age with the significant wave energy balance equation for wind wave, a new wind wave growth relation is presented. Comparisons with the other existing wind wave growth relations show that the results in present paper accord better with the wind wave growth process.

Analysis of ERS-2 scatterometer winds and wind-wave calculation for eastern China seas

在中国海上的风系在在那里的气候变化起一个重要作用。在这篇论文，盖住 1998 的时期的 ERS-2 scatterometer 风和 25-41 °N 的区域， 117-13O °E 被分析并且在一样的时期和地点与 NCEP 风和浮标相比弯屈，到估计多好 ERS-2 数据反映真实的风政体，至少为这个区域。结果显示 ERS-2 scatterometer 风比 NCEPwinds 接近浮标观察。另外，一种新风波浪生长关系被使用计算波浪参数。

Similarities of Some Wind Input and Dissipation Source Terms

Wind input parameterizations proposed by Jeffreys, Sverdrup and Munk, and Plant are analyzed. It is found by analogy that the similarity of integrals of the three wind input parameterizations exists. Wave breaking dissipation parameterizations proposed by Tsikunov, Hasselmann, and Phillips are also analyzed. Likewise it is found by analogy that the similarity of integrals of the three dissipation parameterizations exists. The similarities of wind input and dissipation are applied to the investigation of the fetch-limited growth of wind waves, together with the 3/2 power law presented by Toba. Some semi-empirical formulas concerning the growth of wave height and period with fetch are presented. The results from the formulas are in good agreement with previous field observations.

风生浪各阶段特征演化数值模拟

风波增长现象广泛存在于自然中.尽管通过实验研究已经提出了多种理论假设,但由于风场和波场的随机性和多尺度特性,未能通过实验获得可靠的原理解释其机理.随着计算流体力学的发展,对风波演化进行数值模拟以研究其生成机理更为便利.文章基于自主开发的直角网格两相流求解器,结合高阶数值格式和VOF(volume of fluid)界面捕捉方法,对阶段和指数增长阶段组成.为分析能量特征,计算了能量集中的主要波数,并结合波高、波斜率与波数的变化与实验相对比.在一维波数空间中统计能量分布,与Kolmogorov-ZakharovE (k)~k^(-15/4)幂律进行对比.在二维波数和时域空间中,增长前期应用Phillips线性增长理论和共振加强后的增长模型对风波线性增长阶段进行验证;增长后期应用Miles理论对风波指数增长进行验证.揭示了风波增长不同阶段的机理特征,观察到在指数增长开始前,波浪的线性增长存在初始响应阶段、风压稳定阶段和风压受扰阶段,分别具有不同的机理特征.证明了波浪演化的初始线性阶段是由湍流波动产生的随机尾流叠加占主导,而后期的指数增长阶段是由增长率和摩擦速度正相关占主导.原始的Phillips理论仅在增长初始响应阶段准确,使用共振加强修正后则在初始响应后也符合实际增长,而Miles理论仅在单色波阶段时才准确.相较于对波陡有限制的动态曲线网格求解器,应用5阶WENO (weighted essentially non-oscillation)和动量-质量一致推进方法修正的VOF方法也可用于分析风波增长问题的求解,并能准确捕捉到更多风波增长的细节.

深水风浪的风区指数律

对已有根据观测提出的幂函数形式风浪成长关系进行了分析。发现这些风浪成长关系在消去无因次风区后一致地与 3 /2指数律相协调 ,尽管它们原来存在较大的不协调性。发现Jeffreys ,Sverdrup和Munk以及Plant的风能输入源函数在谱积分意义下具有相似性 ,而Tsikunov ,Hasselmann和Phillips的破波耗散源函数在谱积分意义下也具有相似性 ,尽管这些源函数的原始形式和物理背景显著地不同。利用有效波能量平衡方程 ,将 3 /2指数律和发现的风能输入及破波耗散源函数相似性相结合 ,提出了深水风浪随风区成长的分式指数律 ,以得到的分式指数律拟合已有基于观测提出的风浪成长关系提出了半经验的风浪成长关系 ,与已有观测数据符合。

风浪成长关系的分析及其对3/2指数律的支持

系统地分析比较了迄今根据观测已提出的一些风浪成长关系。通过研究发现 :这些风浪成长关系式存在较大的不协调性。然而 ,当消去无因次风区后 ,由这些关系式得到的无因次波高与无因次周期关系却与 3/ 2指数律有着非常好的协调一致性。还分析 Wen etal构造出的代表平均状况的风浪成长关系。发现由这一风浪成长关系得到的无因次波高与无因次周期关系是与平均状况的 3/ 2指数律完全一致的。上述风浪成长关系构成对 3/ 2指数律的观测支持 ,从而说明了 3/ 2指数律的普遍性。

南海北部风浪特征的计算

探讨南海北部海域风浪成长时有效波高与风速、风时、风区之间的关系,同时分析了5种风浪要素的推算方法,探讨其在南海北部海域的适用性。结果表明:1)在南海北部,风速和风时呈现线性增长的关系,风速越大,风浪从过度状态成长到充分成长状态所需风时就越长;风速大小和风区长度之间满足平方关系,风速越大,风浪充分成长所需风区长度就越长。2)在南海北部,有效波高的大小与风速的大小、风时的长短、风区的长度3者密切相关。3)SMB方法、W ilson IV方法和青岛方法,在计算南海北部的风浪关系中体现出了一定的稳定性和适应性。

风浪对湖泊浮游生物影响的研究进展

风浪在自然水体中广泛存在,是浮游生物生存环境的本质特征。在湖泊(特别是浅水湖泊)中,风浪过程广泛影响着水体的物理、化学特性,并直接和间接对浮游生物产生重要影响。综述了风浪对湖泊浮游动物、浮游植物和浮游细菌影响的相关研究。风浪对浮游生物的时空分布及其在塑造浮游生物系统的结构和功能中发挥了至关重要的作用:风浪条件在浮游生物的行为、营养盐吸收速率和通量、捕食及其生长、竞争和演替等方面均具有广泛且重要的影响,并显著影响着水体食物网的结构和功能,最终对湖泊生态系统的结构和功能产生潜在的影响。提出了未来研究的主要方向为进一步揭示全球气候变化条件下风浪在湖泊中的生态环境效应,为富营养湖泊的治理和管理提供新的认识和决策支持。

基于ERA-Interim再分析资料的南沙海域风、浪场特征分析

基于ERA-Interim再分析资料,统计分析了南沙海域的风场、海浪场的时空特征,并进一步研究了风浪成长关系,建立了适用于南沙海域的风浪模型。月平均场分析结果表明:在季风期,南沙海域的月平均有效波高与风场的时空分布特征有良好的对应关系,位于中南半岛的东南部存在一个风速和有效波高的大值中心,冬季强于夏季,中心位置随季节转换稍向下风向移动。频率分析结果表明:南沙海域全年以4级以内风力和3级以内海浪出现的频率最高,6级以上大风和5级以上海浪主要出现在冬季风期间;全年最大风速和浪高出现在10、11月,最大风速达到8级,最大有效波高可达6级,但频率非常小;整个海域风速和浪高最小的时期是4—5月。