Wave Reflection Coefficient Spectrum

1 .IntroductionWavereflectionfromstructuresisanimportantfactorforthedesignofthestructures .Therehavebeenmanyresearchesonwavereflectionwithregularwavesandmonochromaticirregularwaves .Miche( 1 951 )proposedanon dimensionalMichenumberMfornormallyincidentirregularwavesconsideringwavebreakingbecauseofthedeepeningofwavesteepnessontheslopeofbreakwaters .ThereflectioncoefficientisproportionaltoM ,i.e .,Kr ∝M =4g( 2π) 5/ 2tan5/ 2 α(Hsf2p) ( 1 )wheregisthegravitationalacceleration ,Hsthesignifican…     

风浪状态对海面拖曳系数的影响

通过对四种参数化方法的比较,认为风海雷诺数RB较风速、波龄和波陡能更好地描述拖曳系数CDN。利用分组平均法对CDN与RB关系进行处理,得到最佳的CDN参数化方案。利用COARE3算法测试了四种依赖海况的粗糙长度,与实测结果进行了比较,结果表明CDN与RB的关系式更真实地反映了海-气界面动量交换过程。     

Statistical Simulation of Boxing Day Tsunami of The Indian Ocean and a Predictive Equation for Beach Run up Heights Based on Work-Energy Theorem

The tsunami similar to the one that has occurred in December 26, 2004 (Boxing Day Tsunami) in the Indian Ocean is simulated using the expression derived from Modified Weibull Distribution (for maximum wave height simulation) for extreme wave height predictions. The tuning coefficient plays a significant role in estimating the tsunami heights at various stages. It follows well defined mathematical laws at different stages. It is time dependent in the first three stages and depth dependent in the last two stages. The beach run-up heights estimated by the expression derived from the work-energy relation are comparable with observed values with reasonable accuracy.     

Comparison of Ocean Surface Wind Stress Computed with Different Parameterization Functions of the Drag Coefficient

Depending on the choice of reference wind speed, the quantitative and qualitative properties of the drag coefficient may vary. On the ocean surface, surface waves are the physical roughness at the air-sea interface, and they play an important role in controlling the air-sea exchange processes. The degree of dynamic influence of surface waves scales with wavelength. Drag coefficient computed with the reference wind speed at an elevation proportional to the wavelength (for example, U _λ/2) is fundamentally different from the drag coefficient computed with the wind speed at fixed 10 m elevation (U ₁₀). A comparison has been carried out to quantify the difference in wind stress computation using several different parameterization functions of the drag coefficient. The result indicates that the wind stress computed from U ₁₀ input using a drag coefficient referenced to U _λ/2 is more accurate than that computed with drag coefficient functions referenced to U ₁₀.     

利用伴随同化方法估计渤海潮汐模式的底摩擦系数

利用伴随同化方法，根据岸边潮位站的水位观测资料反演渤海二维非线性潮汐模型的底摩擦系数。计算结果与潮位站观测资料符合良好。结果表明利用伴随同化方法从岸边潮位观测资料估计潮汐模式的底摩擦系数是可行的。     

两层流体中矩形箱浮体的附加质量和阻尼系数

研究了两层流体中矩形箱浮体的辐射问题。基于特征函数匹配理论,针对矩形箱浮体的三种振荡运动模式(横荡、垂荡和横摇),建立两层流体中矩形箱浮体辐射势的求解方法,导出矩形箱浮体附加质量和阻尼系数的计算公式。对所建立的求解模型进行了数值计算分析,结果表明在矩形箱浮体的某个振荡频率范围内,流体的分层效应对其附加质量和阻尼系数有显著影响的。     

Investigation and comparison of one-dimensional (1-D) analytical models prediction for salt intrusion condition in two selected estuaries

Abstract

In this paper, two analytical models used worldwide to assess salinity variation in alluvial estuaries are applied to the Ashtamudi estuary, a Ramsar site, southwest coast of India; and Bouregreg estuary, in northwest part of Morocco. The estuaries’ bathymetry is described by an exponential function. Both models are quite similar and use a predictive equation for the dispersion in the estuary mouth (D₀). The major difference between the two models is the use of the constant value of K?=?0.5 for the Van der Burgh coefficient (K) and the introduction of the correction factor ζ, which is a function of damping (δ) and shape (γ). The performance of these two models was evaluated by comparing their results with field measurements; this revealed that both analytical models apply well to both the estimation of salinity distribution and the prediction of salt intrusion in the Ashtamudi and Bouregreg estuaries (Ashtamudi: RMSE = 0.60–1.22 ppt; Bouregreg: RMSE = 0.92–2.71 ppt). One model agrees more with the field measurements of salinity distribution along the estuaries axis; the second underestimate and overestimate some values of salinity distribution along the estuaries. Possibly, the constant value of K?=?0.5 for the Van der Burgh coefficient (K) has applicability limits for the estuaries under tidal conditions. The specifying of the parameterization may be a field of research.     

近海湍流三维数值模拟中的重整化群模式

利用重整化群理论来确定近海湍流数值模式中的垂向涡动粘性系数，并对冬末春初琼州海峡的潮流场特征进行数值模拟。结果表明，重整化群模式的待定常数少，应用方便可行，其计算结果也比常用的湍流封闭模式的计算结果更加合理。     

黄河口及邻近海域表层沉积物中锌的研究

作者于1984年夏季测定了黄河口及邻近海域表层沉积物中Zn、Fe、Mn、Cu及有机质的含量。结果表明:河口及近岸海域表层沉积物中Zn含量较高Zn与有机质、Fe、Mn、中值粒径呈正相关,相关系数为: γ_(Zn-Org)=0.704 γ_(Zn-Fe)=0.858 γ_(Zn-Mn)=0.802 γ_(Zn-Mdφ)=0.906 本文提出表层沉积物中Zn的地球化学形式、含量及其分布。在调查区表层沉积物中总锌平均含量为80.47mg/kg,其中可交换部分为0.48％,碳酸盐结合部分占5.16％,铁—锰氧化物结合部分占15.5％,有机物结合部分占9.15％,残渣部分为69.3％。     

夏季北黄海冷水团多年变化特征分析

本文根据横贯北黄海冷水团的大连—成山角断面的４２年观测资料，采用“相似系数”方法分析了北黄海冷水团的分布范围、低温中心位置、厚度、相对体积、温、盐特征等的多年变化特征。根据诸特征的标准离差，将这４２年北黄海冷水团划分为强、弱和平年三种情况