长波和水流作用下浮泥流动机理研究

基于宾汉模型,并运用量级分析方法建立了长波、水流作用下浮泥运动简化方程。简化后的浮泥运动方程是一个非线性的常微分方程。运用解析与数值混合的方法进行求解,计算量很小。讨论了水流对泥面的剪应力、波幅、波长、浮泥层厚度以及浮泥密度等多组参数对浮泥输运速度的影响。研究表明,存在波浪的情况下,即使水流对泥面的剪应力远小于浮泥屈服应力浮泥也能出现定向的输运。     

Sediment Transport in Rivers and Coastal Waters

Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.     

风暴过程中潮滩悬沙浓度和悬沙输运的变化及其动力机制——以长江三角洲南汇潮滩为例

悬沙浓度是淤泥质海岸重要的环境指标。为探讨潮滩悬沙浓度和悬沙输运对风暴事件的响应过程及其动力机制,于2014年9月\"凤凰\"台风过境前、中、后在长江三角洲南汇潮滩进行了现场观测,获得同步高分辨率的水深、波高、近底流速和浊度剖面时间序列(9个潮周期)。结果表明,风暴中平均和最大波高、波-流联合底床剪切应力、悬沙浓度和悬沙输运率可比平静天气高数倍;风暴期间高潮位低流速阶段悬沙沉降导致近底发育数十厘米厚的浮泥层(悬沙浓度大于10 g/L)。研究认为风暴事件中淤泥质海岸悬沙浓度和悬沙输运的剧烈变化其根本动力机制是风暴把巨大能量传递给近岸水体,进而显著增大波-流联合底床剪切应力,导致细颗粒泥沙再悬浮。     

水动力时空变化对近岸风浪演化的影响——以渤海湾西南岸为例

采用SWAN模型和ADCIRC模型建立了风浪、潮汐和水流联合作用的耦合数值模式,并通过渤海湾西南岸实测资料对该模式进行了验证。利用该模式分析了近岸区水位和流场时空变化对风浪模拟结果的影响,计算结果表明水位变化对近岸区风浪模拟结果有显著影响,特别是中等大风过程高潮位时波高受水位影响的变化幅值可达0.5m以上,且水深越浅影响越大。但在岸滩平缓的近岸海域由于流速、流向的时空变化不太剧烈,流场作用和波浪辐射应力作用对波浪场的影响都基本可以忽略。在模拟近岸风浪过程时,应选用耦合模式。     

强海况下波流相互作用对有效波高的影响研究

波流相互作用作为非线性科学的前沿课题,一直受到国内外广大学者的关注。本文以2016年第1号超强台风“尼伯特”为例,基于波流耦合模式研究了台风影响期间强海况下波流相互作用对有效波高的影响。研究表明：（1）波流耦合模式可有效提高强海况下海浪的模拟精度;（2）波流相互作用对有效波高的影响与波向和流向之间的夹角关系密切：当波向与流向大致相同时,波流相互作用使有效波高减小;当波向与流向大致相反时,波流相互作用使有效波高增大;当波向与流向之间的夹角越接近90°时,波流相互作用对有效波高的影响越小。波流相互作用对有效波高的影响最大可达1.5 m。     

弱流场调制下的海面微波散射模拟研究

根据海面微波散射的多尺度模型以及波流相互作用理论,对一维弱流场调制下的海面微波散射截面进行了数值模拟。结果表明,利用数值方法直接求解波作用量方程获得的海浪调制谱并结合多尺度模型可以较好地模拟弱流场引起的雷达散射截面的变化。内波等海洋现象调制了海浪谱,使得雷达散射截面反映出这些海洋特征,整个调制过程的模拟对于分析这些海洋现象并更好地利用其雷达数据具有重要意义。     

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.     

日照豪迈码头港池布局对泥沙输移影响研究

港池的布局会改变其周边海域水动力条件及其泥沙冲淤状况,为了进一步了解其影响程度,本文以山东日照豪迈重工临港厂区运输码头的改造工程为研究对象,利用平面二维数值模型MIKE21/3 Integrated Models,建立了潮流和波浪耦合作用下的泥沙输移数值模型,对该工程附近海域进行了波浪、潮流和泥沙输移的数值模拟。同时采用实测数据对数值模型进行了验证,数值模拟结果与实测资料拟合较好,表明MIKE21能有效地模拟运输码头及其周围海域潮流的变化过程。以日照豪迈重工临港厂区运输码头为依托,基于数值模拟结果,分析不同改造方案下的水动力条件和泥沙冲淤状况。结果表明:港池布局对水动力条件影响甚微,对地形地貌冲淤影响较大;模拟结果确定港池南向开口为最佳改造方案,为工程的规划和设计提供科学依据。     

波浪运动在底边界层的湍流结构数值研究

本文基于$ k $-$ varepsilon $ 模型研究了波流边界层内湍流结构特征。研究结果表明,时均流速分布数值解与实验结果高度吻合。一个波周期内湍流结构特征（如：涡量、湍动能、湍动能耗散率等）呈周期性变化规律,波浪作用引起涡量、湍动能及湍动能耗散率均在减速阶段减小,在波谷处达到最低值,而后在加速阶段增大,并在波峰处达到最大值。近壁面处湍流结构变化幅值较大（湍动能耗散率变化可达53%）,远离壁面处变化幅值较平均值较小（仅3%）。波流边界层厚度在减速阶段增加,在加速阶段减小。本文所建立的数值模型克服了现有模型因采用“高雷诺数方法”引起的近壁区精度不高问题,可较好地描述波浪作用下湍流结构演变过程的物理机制,为河口海岸地区泥沙运动、岸滩演变及海洋可再生能源的开发利用提供一些指导意义。     

波浪作用下浮泥悬扬浓度特性研究

为研究不同波浪环境下,水底浮泥层产生泥沙悬扬后其浓度的分布特性,使用浊度计测定浊度的方法确定水体中泥沙的浓度,并在水槽实验中改变水深、浮泥厚度及造波机的频率和振幅,观察水槽中悬浮泥沙浓度的变化情况,获得水深、波浪频率、波幅以及浮泥厚度对底床泥沙悬扬的影响,分析泥沙浓度的垂向分布特征等。实验结果显示,水深对底床泥沙悬扬的影响最为显著,其他实验参数的影响均不十分显著。同时,通过垂向输沙平衡的分析,得到一个可描述泥沙垂向浓度分布的理论公式,并利用水槽实验结果进行验证。对比结果显示,理论公式所得曲线与实验结果曲线变化趋势一致,部分工况下,理论值稍稍偏大。     

Numerical Modeling of Water Wave Interaction with A Soft Mud Bed

A vertical 2-D numerical model is presented for simulating the interaction between water waves and a soft mud bed. Taking into aceotmt nonlinear theology, a semi-empirical theological model is applied to this water-mud model, reflecting the combined visco-elasto-plastic properties of soft mud under such oscillatory external forces as water waves. In order to increase the resolution of the flow in the neighborhood of both sides of the inter-surface, a logarithmic grid in the vertical direction is employed for numerical treatment. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes.     

波流联合作用下深水铰接塔平台的组合共振

研究了深水铰接塔平台在波流联合作用下的组合共振特性。将平台顶部工作单元简化为集中质量,塔柱和浮力仓简化为均匀直杆,建立了铰接塔平台运动分析模型。考虑海流和波浪对平台的作用,应用Morison公式计算铰接塔平台瞬时位置所受水动力,依据拉格朗日原理建立了铰接塔平台的强非线性运动方程。分别考虑波浪作用和波流联合作用,采用数值计算方法,计算了高400m、塔柱直径15m的浮力塔平台的多种组合共振响应。研究表明,波浪作用下平台将出现2vm＋vn组合共振,波流联合作用下平台将出现vm＋vn组合共振、2vm＋vn组合共振。     

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.     

Wave Scattering by Double Slotted Barriers in A Steady Current： Experiments

The adoption of slotted breakwaters can be an ideal option in the protection of very large near-shore floating struc-trees that may extend offshore to a considerable water depth. In this paper, we experimently investigated the behaviour of wave transmission and reflection coefficients of double slotted barriers in the presence of a steady opposing current. The experimental results show that opposing currents have only minor effects on wave reflection, but can significantly reduce the wave transmission through double slotted barriers. The experimental results suggest that coastal currents should be taken into consideration for an economical design of slotted breakwaters.     

Effects of Topography and Current on Horizontal Irrotational Waves in Shallow Water

Based on the Boussinesq assumption,derived are couple equations of free surface elevationand horizontal velocities for horizontal irrotational flow,and analytical expressions of the correspondingpressure and vertical velocity.After the free surface elevation and horizontal velocity at a certain depth areobtained by numerical method,the pressure and vertical velocity distributions can be obtained by simplecalculation.The dispersion at different depths is the same at the O(ε)approximation.The waveamplitude will decrease with increasing time due to viscosity,but it will increase due to the matching ofviscosity and the bed slope.thus,flow is unstable.Numerical or analytical results show that the waveamplitude.velocity and length will increase as the current increases along the wave direction.but theamplitude will increase.and the wave velocity and length will decrease as the water depth decreases.     

Numerical investigation of the effect of current on wave focusing

In the present study,a numerical wave tank is developed to simulate the nonlinear wave-current interactions based on High Order Spectral(HOS) method.The influences of current on wave focusing are investigated by use of numerical model.The current is assumed to be constant in space.Focused waves with different amplitudes and frequency spectra are simulated with and without current.The focused wave characteristics,such as surface elevation,the maximum crest and frequency spectrum,with different current are compared.The results show that the opposing current increases the maximum crest and the energy transform during wave focusing process,and vice versa for the following current.