波流环境中垂向圆管射流三维运动和稀释过程模拟

采用大涡数值模拟方法建立了波流环境中垂向圆管射流三维物质输运数学模型,在此基础上分析了波流共同作用下射流运动和稀释过程,并探讨了波浪对射流三维时均浓度特征的影响。数模结果与实测数据的对比表明,该模型能够正确复演波流环境中射流速度和浓度沿水深分布的规律。引入了射流的三维浓度特征指标,即断面最小稀释度及其垂向位置和断面可视范围面积,发现随着波高或波周期的增大,波流环境中射流的断面可视范围面积逐渐增加,这说明波浪对射流的稀释起到一定的促进作用。     

波-流联合作用场中流的等效作用研究

针对波-流相互作用问题中的流速沿水深非线性分布的水流处理方法问题,提出了“等效均匀流”概念和相应理论,使非线性分布的水流作用等效为相应的均匀流作用,从而使问题大大简化.无论是二维顺、逆流问题还是三维波一流斜交折射问题,非均匀流都可以基于本文方法和理论予以近似处理,以采用等效均匀流概念计算的小尺度垂直桩桩的波一流联合作用力计算为例,对该理论和方法的应用作了初步的探讨和验证.     

黄河三角洲区域的波流相互作用数值分析

将三维水动力-生态模式COHERENS与第三代波浪模式SWAN结合起来,采用该耦合模式数值计算了黄河三角洲的波浪特征波高与特征周期情况,从而探讨水流和波动水位对波浪特征波高和特征周期计算结果的影响。总的说来特征波高、特征周期、流速的计算结果与观测值吻合得较好,说明了COHERENS模式和SWAN模式相结合而成的波流耦合模式能够较好地计算黄河三角洲地区的流场与浪场情况。研究这些动力因素的机制和时空变化规律,对于研究海岸、河口的泥沙运动,海岸侵蚀的机理,合理开发利用自然资源,防止海洋灾害具有十分重大的意义。     

波流联合作用下海底管道侧向运动数值分析

研究旨在提出波流联合作用下海底管道侧向运动数值模拟分析方法。通过建立三维离散刚体模拟海床,梁单元模拟海底管道,设置了两个载荷步模拟管道与土壤接触的过程,解决了实体模型不易收敛的问题。分析了不同管—土法向行为接触刚度、不同管—土切向行为摩擦系数、不同波流参数以及不同单位长度管道水下质量对海底管道侧向运动的影响。研究表明：海底管道的最大等效应力、最大侧向位移、最大接触压力以及最大横向摩擦剪应力对于管—土法向行为接触刚度的变化并不敏感;管道的最大侧向位移随着管—土切向行为摩擦系数增大而减小,呈现出线性变化的关系;当波高一定时,管道的最大侧向位移随着流速的增加而增大,并且波高越小,最大侧向位移随流速增加的速度明显越大;管道最大侧向位移随着单位长度管道水下质量的增加而减小,并且呈现出线性变化的关系。     

Altimeter Measurements of Wind and Wave Modulation by the Kuroshio in the Yellow and East China Seas

The Kuroshio is the major ocean current conveying heat and water mass in the Pacific Ocean. The impact of the Kuroshio on regional wind and wave distributions has been studied with spaceborne-altimeter measurements in the Yellow and East China Seas. In this region the Kuroshio trajectory is relatively stationary and the monsoon patterns dominate, making it an ideal natural laboratory for large scale air-sea-current interaction research. Major findings from this study include: (a) The Kuroshio exerts significant influence on the wind and wave distributions over a swath about 800-km wide along its path. (b) Seasonal average wind speeds reach a maximum near the Kuroshio axis. The magnitude of enhancement ranges between 20 and 50 percent. (c) The distribution of the surface wave heights displays similar spatial patterns to the wind-speed distribution. The Kuroshio effects on wave heights are further complicated by the hydrodynamic modulation of wave-current interaction and the influence of thermal stratification on wind-wave generation. (d) Kuroshio effects are most prominent in the first and last quarters of the year, and least prominent in the third quarter.     

Interaction of Streamwise and Wall-Normal Velocities in Combined Wave-Current Motion

The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity components has been compreheusively examined. Different from previous researches which attributed the deviation of velocity from the classical log-law to the wave Reynolds stress, i.e. - ρ uv^- only, this study demonstrates that the momentum flux caused by mean velocities, i.e., u^- and v^-, is also responsible for the velocity deviation, and it is found that the streamwise velocity for a flow in the presence of non-zero wall-normal velocity does not follow the classical log-law, but the modified log-law proposed in this study based on simplified mixing-length theorem. The validity of the modified log-law has been verified by use of available experimental data from published sources for combined wave-current flows, and good agreement between the predicted and observed velocity profiles has been achieved.     

Refraction-Diffraction Model for Irregular Wave and Directional Spectrum Considering Current

- A mild-slope equation for combined refraction and diffraction of random waves in the independent time current is derived using Kirby equation(1984). In the derivation, the frequency of random waves is represented based on the time series concept, by a typical frequency and its deviation part. Numerical results, compared with those of laboratory experiments, demonstrate that new set of irregular mild slope equation with current is of good adaptability.     

Hydrodynamic Characteristics of Submarine Composite Pipeline in a Wave-Current Coexisting Field

-A composite pipeline is defined as a pipeline system composed of one big pipe and one or several small pipes. Based on the theory of wave- current interaction and physical model test, the hydrodynamic characteristics of the submarine composite pipeline in wave-current coexisting field (both regular and irregular waves) are investigated. The so-called "modified diameter method" is used for analyzing the in-fine hydrodynamic coefficients of the composite pipeline, which are well related to KC number. The comparison of test data for regular and irregular waves shows that in the region of 90 > KC> 20, the results in these two cases can be unified. The effect of water depth is analyzed in details. The relationships between CD, CM and KC , which are based on the results of present research, may be used as a reference in engineering design.     

Interaction of waves with non-colinear currents

The present paper reports on a study of the interaction of a current-free monochromatic surface wave field with a wave-free uniform current field in a three-dimensional flow frame. The wave and the current fields are not necessarily collinear with each other. The formulation of the wave-current field is done under the assumption of irrotational and inviscid flow. We have developed the three dimensional expressions describing the characteristics of the combined flow in terms of mass, momentum and energy transport conservation. These equations are found efficient to describe the sought-for combined wave-current field. The parameters describing the wave-current field after the interaction are the surface disturbance amplitude and length, mean water depth, mean current-like parameter and direction of the combined flow, which would be calculated from a set of equations that satisfy conservation of mean mass, momentum and energy flux and a dispersion relation on the free surface before and after the interaction. The results are shown in terms of relative changes in wave heights and lengths, current-like parameters and final directions obtained for the combined wave-current field with respect to current-free wave and wave-free current pre-interaction parameters.     

A Higher Order BEM for Wave-Current Action on Structures ——Direct Computation of Free-Term Coefficient and CPV Integrals

1 .Introduction Research on wave action onforward moving bodies or wave-current action on structures is impor-tant in offshore and coastal engineering.For bodies withsimple geometry,analytic solutions have beendeveloped . Matsuiet al .(1991) and Emmerhoff and Sclavounos (1992) derived analytic solutionsforuniformcylinders infinite andinfinite water depth.Bao and Kinoshita (1993) expendedthe theorytotruncated cylinders .In engineering practice ,structures are complexand numerical methods have…