波浪作用上软泥床面的粘性泥沙县扬

本文考虑波浪与软泥床面相互作用，建立了计算软泥床面上波浪剪应力的理论模型。     

波浪掀沙的动力学机理分析

本文从床面附近泥沙颗粒的运动特征出发，详细分析波浪作用下床面泥沙扬起的动力学机制，得到了波浪掀沙计算公式，计算结果与实测资料相吻合。研究表明淤泥质海岸泥沙颗粒的稳定性主要受制于颗粒间的粘结力和薄膜水压力，重力作用则居于次要地位，因此泥沙颗粒越细越难以起悬。     

波浪欣沙的动力学机理分析

本文从床面附近泥沙颗粒的运动特征出发，详细分析波作用下床面泥沙扬起的动力学机制，得到了波浪欣沙计算公式，计算结果与实测资料相吻合、研究表明淤泥质第岸泥沙颗粒的稳定性主要受制于颗粒间的粘结力和薄膜水压力，重力作用居于次要地位，因此泥沙颗粒越细越难以起悬。     

长江口非均匀细颗粒粘性泥沙扬动流速

泥沙的扬动流速是指泥沙颗粒跃起后不再回落到床面,而是悬浮于水中,并随水流运动前进时的临界流速.在4次野外调查的基础上,基于扬动流一般公式,对长江口区流向稳定时期同步观测的垂线平均流速、底部悬沙粒径、水深和泥沙沉速等数据进行回归分析,拟合长江口区非均匀细颗粒粘性泥沙杨动流速公式,相关系数达0.85以上.经该公式计算的长江口非均匀细颗粒粘性泥沙扬动流速值大于已有公式计算值.     

水流作用下粘性泥沙悬扬的动力分析

本文从水流与淤泥质床面的相互作用的动态角度来探讨粘性泥沙悬扬机理。水层采用粘性体模型，泥层采用粘弹性体模型，耦合求解水体和淤泥质床面的运动方程，得出界面的稳的水流临界流速、界面波波速和波长等，将理论结果与实验结果进行比较和讨论，得出了一些有意义的结论。     

波浪作用下悬沙浓度垂线分布的研究

根据波浪作用下的泥沙悬浮机理,即影响泥沙悬浮的主要因素从近床面的紊动扩散逐渐过渡到自由表面的波动水质点周期运动,提出了全水深悬沙扩散系数的表达式,建立了悬沙垂向时均浓度分布的显式解析模型,并进一步讨论了参考含沙量和床面摩阻系数的合理取值。计算值与测量值的比较表明,该浓度分布模型与不同尺度的水槽实验数据吻合较好。     

潮流和波浪作用下悬移质挟沙能力的研究

本文将湍流猝发理论用于潮流与波浪共同作用下挟沙能力的研究。基于湍流猝发的时空尺度得到波浪和潮流作用下床面泥沙上扬通量 ,然后根据连续律 ,建立了平衡近底含沙量的理论表达式。进而根据波浪掀沙和潮流输沙的模式 ,推导得出了物理概念清晰和充分考虑床面附近泥沙交换力学机理的潮流和波浪共同作用下的挟沙能力公式 ,经过黄河口实测资料的验证 ,计算与实测符合良好。     

波浪作用下涡动沙纹床面的悬沙运动数值研究

作者建立了波浪作用下的立面二维水沙数值模 型，并对涡动沙纹床面的悬沙运动进行研究。结果表明：悬沙颗粒的沉降速度较小时，其运 动受到涡动力特性的影响比较显著。而且在沙纹波峰断面和沙纹波谷断面，半个周期里都可 以观察到两个悬沙分布的峰值，主要是由于流动分离形成分离涡，涡运动携带泥沙颗粒而出 现峰值。计算成果在一定程度反映了涡动结构对悬沙运动的影响。     

波浪作用下沙纹床面上底部剪应力的实验研究

在沙质床面上传播的波浪当其强度超过一定条件时,将使沙质床面的形态发生变化而形成沙纹床面,沙纹床面上的底部剪应力与平床面上的底部剪应力有不同的形成机理。而沙纹床面上底部剪应力的研究是波浪沿程衰减和输沙研究的基础。本研究成功地实测了沙纹床面上的底面剪应力,并根据实验成果给出了沙纹床面底部摩阻系数和剪应力的计算公式。     

明渠挟沙水流中悬移质的床面平衡浓度

本文通过泥沙颗粒运动的概率密度输运方程，推导出床面附近运动的泥沙颗粒的概率密度函数及相应的泥沙颗粒向上运动和向下运动的通量，建立了计算明渠挟沙水流悬移质床面平衡浓度的关系式。通过与试验资料及经验公式的比较对本文建立的关系式进行了检验，结果表明本文所得计算公式与实际符合较好，可用于悬沙床面平衡浓度的计算。     

Impacts of wind waves on sediment transport in a large,shallow lake

Lake Okeechobee is a large, shallow subtropical lake, located in south Florida. Over the last several decades, Lake Okeechobee has experienced accelerated eutrophication due to excessive phosphorus loads from agricultural run‐off. Recycling of phosphorus from bottom sediments through resuspension is critical to addressing eutrophication of the lake and for water quality management. The present study investigates the impacts of wind waves on sediment transport in Lake Okeechobee, using measured data and the Lake Okeechobee Environmental Model (LOEM). The LOEM was fully calibrated and verified with more than 10 years of measured data in previous studies. Analysis of the measured data indicates significant wave height (SWH) and suspended sediment concentration are closely correlated to the wind speed in the lake. The nonlinear interaction of high‐frequency wind waves with relatively low‐frequency currents in the boundary layer plays a key role in sediment deposition/resuspension. Without considering the effects of wind waves, the bottom shear stress can be greatly underestimated. The spatial variations of key variables for sediment modelling, including SWH, water depth, orbital velocity, current velocity, bottom shear stress and sediment concentration, are discussed. In general, the near‐bottom wave velocity (and the associated bottom shear stress) is greater than or the same order of magnitude as the near‐bed current velocity (and the associated bottom shear stress) in this shallow water system. Although the sediment zones of Lake Okeechobee were described in previous studies, few published papers discussed its formation mechanisms. The findings of the present study include that the multiyear averaged bottom shear stress with wind‐wave effect plays a key role in forming the spatial patterns of the sediment zones. The study results are currently being used in lake management and in developing strategies for reducing phosphorus in the lake.     

Erosion of glacial till from the St. Clair River (Great Lakes basin)

Variations in water level observed in Lakes Michigan and Huron during the last few decades have motivated a comprehensive study involving climatic, hydrologic and hydraulic factors organized by International Joint Commission of the Great Lakes. It has been submitted, among other possible causes, that changes in conveyance in the St. Clair River could be contributing to the lowering of the upper Great Lakes water level. Sediment transport processes, in particular bed scour and erosion, can affect significantly a river's conveyance, thus creating the need to assess the erodibility properties of the river bed. To this end, laboratory tests were performed in order to obtain the value of the critical shear stress needed to erode the cohesive fraction of the bed sediment material, known as glacial till, from the St. Clair River. Different flows with increasing velocities were run up to the point where initial sediment erosion could be observed. Through detailed near-bed velocity measurements using a laser Doppler velocimetry (LDV) system, a value of 4.2 N/m² was obtained as the critical shear stress for the erosion of glacial till. A threshold for the critical shear stress for erosion of similar cohesive sediments was also found and expressed in dimensionless form. These results could be used in combination with mathematical models to estimate the risk of scour and erosion at locations where the glacial till is exposed to both strong currents and flow forces induced by the large navigation vessels commonly observed along the course of the St. Clair River.     

波浪作用下淤泥质底床泥体输移

建立了用于模拟波浪运动的水体引起底床软泥层振荡并导致泥体输移的垂向二维数值模型。该水-泥模型中应用了一个半经验的非线性的淤泥流变模型,该流变模型表达了淤泥体在循环剪切外力(波浪)作用下其应变及应变率与应力关系的显著的滞后回线特征。数值处理技巧上,为提高数值格式对水-泥界面附近流动的分辨力,较好地再现界面附近速度梯度大的流动特点,垂向网格方法是在水-泥界面的两侧区域均采用对数网格。模型验证是通过计算水波波高衰减率和底床软泥体输移速度,并与有关的实验测量数据进行比较。     

A NEW MEASURE FOR DIRECT MEASUREMENT OF THE BED SHEAR STRESS OF WAVE BOUNDARY LAYER IN WAVE FLUME

In this article, a shear plate was mounted on the bottom in a wave flume and direct measurements of the smooth and rough bed shear stress under regular and irregular waves were conducted with the horizontal force exerted on the shear plates by the bottom shear stress in the wave boundary layer. Under immobile bed condition, grains of sand were glued uniformly and tightly onto the shear plate, being prevented from motion with the fluid flow and generation of sand ripples. The distribution of the bottom mean shear stress varying with time was measured by examining the interaction between the shear plate and shear transducers. The relation between the force measured by the shear transducers and its voltage is a linear one. Simultaneous measurements of the bottom velocity were carried out by an Acoustic Doppler Velocimeter (ADV), while the whole process was completely controlled by computers, bottom shear stress and velocity were synchronously measured. Based on the experimental results, it can be concluded that (1) the friction coefficient groews considerably with the increase of the Reynolds number, (2) the shear stress is a function varying with time and linearly proportional to the velocity. Compared with theoretical results and previous experimental data, it is shown that the experimental method is feasible and effective, A further study on the bed shear stress under regular or irregular waves can be carried out. And applicability to the laboratory studies on the initiation of sediments and the measurement of the shear stress after sediment imigration.     

Sensitivity of a sediment transport model for Lake Michigan

A two-dimensional (vertical and cross-shore) sediment transport model was applied to several transects in southern Lake Michigan using observations of waves and currents recorded during the spring of 2000. Conditions during this period included several storms that are among the largest observed in the lake. The observations were used to examine the sensitivity of the model to variations in the input parameters (waves, currents, initial bottom sediment size distribution, settling velocity, and bottom stress required for erosion). The results show that changing the physical forcing (waves and currents) or the initial bottom sediment size distribution affected the results more than varying the particle properties (settling velocity and critical shear stress) or the size classes used to describe the size distribution. This indicates that for this model specification of input parameters are of first order importance and should be specified with some confidence before adding additional complexity by including processes such as flocculation and bed consolidation.     

The role of wind-wave related processes in redistributing river-derived terrigenous sediments in Lake Turkana: A modelling study

A complete annual cycle of the dynamics of fine-grained sediment supplied by the Omo and smaller rivers is simulated for Lake Turkana, one of the world’s large lakes, with the hydrodynamic, wave and sediment transport model Delft3D. The model is forced with river liquid and solid discharge and wind data in order to simulate cohesive sediment transport and resuspension. It simulates stratification due to salinity, wave generation and dissipation, and sediment advection and resuspension by waves and currents, with multiple cohesive sediment fractions. A comparison of the simulation results with remotely-sensed imagery and with available in-situ sediment deposition rates validates the model. By devising simulation scenarios in which certain processes were switched on or off, we investigated the contribution of waves, wind-induced surface and bottom currents, salinity-induced stratification and river jet, in resuspending and transporting fine sediments in the lake basin. With only the wind or river influence, most of the sediment deposition occurs in the first 10 km off the Omo River mouth and at a depth < 10 m. When waves are switched on, increased bed shear stresses resuspend most of the fine sediments, that are then deposited further and deeper in the first 30 km, in water depths > 30 m. This study sheds new light on sediment transport in Lake Turkana and in great lakes in general, favouring the view that wind-waves can be the main agent that transports sediment away from river mouths and to deeper areas, as opposed to river-plume or gravity-driven transport.     

DISSIPATION OF WAVE ENERGY ON VERY MILD SLOPE

1.　INTRODUCTIONOffshoreareasarewherepeoplefrequentlyengagevariouskindsofhumanactivities,forexamples,portbuilding.seawallconstruction,installationofoildrillingplatformandseashorepowerstation,etc.Whenstructuresplacedinshallowwateraredesigned,thedesignwaveheightalwaystakesthecriticalwaveheight-breakingwaveheight.ThecriticalwaveheightadoptedinChineseCodeisdeterminedbyGoda′smethod,whichiswidelyusedinmanycountries.Thismethodisbasedonthestudyofregularwavesonbottomslopei≥1/50.Themaximumwavehe…     

近海与河口粘性泥沙输移过程——第六届INTERCOH 2000综述

第六届近海与河口粘性泥沙输移过程国际学术会议主要包括以下内容 :1)粘性泥沙与湍流的相互作用 ;2 )淤泥动力特性的现场观测 ;3)粘性泥沙输移过程的数值模拟 ;4 )絮凝作用和絮凝团沉降速率 ;5 )淤泥底床侵蚀、固结过程。主要进展表现在 :1)分形理论被应用于粘性泥沙运动 ;2 )水声学技术、PIV技术的应用 ;3)原位剪应力测量装置 (ISIS)被应用于测量淤泥表面、床体上的侵蚀剪应力分布 ;4 )生物对粘性泥沙运动影响的研究 ,即利用环形水槽实验等 ,探讨异养细菌、超细胞聚合体对粘性泥沙稳定作用的影响 ;5 )一种健壮、有效的适应有限元数学模型 ,考虑絮凝、非牛顿流及高浓度下的湍流耗散 ,被用来解决粘性泥沙的输移问题。     

极平缓岸坡上的底部波能损耗

本文分别分析与计算了波浪在粉沙质海床、沙纹海床和淤泥质海床上传播时波高的衰减。研究表明，波浪在粉沙质海床上传播的渗透损耗可以忽略不计；波浪在沙纹海床上传播的底摩阻损耗比平滑粉沙底床上传播的损耗大，前者的摩擦系数约比后者值大一个数量级。波浪在淤泥质海床上传播的能量损耗最大，其损耗机遇也很复杂。为了便于比较，将波浪在淤泥质海床上的衰减换算成等价摩擦系数。并运用宾汉模型和波浪作用通量守恒原理计算了波浪在极平缓淤泥质海滩上传播时的衰减及沿程等价摩阻系数。与连云港波浪观测资料对比，符合较好。此外。理论计算发现沿程等价摩阻系数与水深关系较大，由深水至浅水逐渐增大，且水深越浅，增速越快。