共查询到10条相似文献，搜索用时 109 毫秒
1.
《中国海洋工程》2015,(4)
The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave?current effect, and confirm that the method of measuring bed shear stress under wave?current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave?current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided. 相似文献
2.
Numerical Simulation of Local Scour Around A Large Circular Cylinder Under Wave Action 总被引：1，自引：0，他引：1
A horizontal two- dimensional numerical model is developed for estimation of sediment transport and sea bed change around a large circular cylinder under wave action. The wave model is based on an elliptic mild slope equation. The wave-induced current by the gradient of radiation stress is considered and a depth integrated shallow water equation is applied to the calculation of the current. The mass transport velocity and the bed shear stress due to streaming are considered, which are important factors affecting the sediment transport around a structure due to waves, especially in reflective areas. Wave-current interaction is taken into account in the model for computing the bed shear stress. The model is implemented by a finite element method. The results of this model are compared with those from other methods and agree well with experimental data. 相似文献
3.
Sediment transport in the Hangzhou Bay is extremely complicated due to its bathymetry and hydrodynamic conditions. The ECOMSED model is employed to simulate three-dimensional (3-D) cohesive sediment transport in Hangzhou Bay. Dynamical factors such as Coriolis force, tides, salinity, river discharges, and waves are considered in the model. The wave parameters, including the significant wave height, period, and direction, are calculated with the SWAN model. The Grant-Madsen model is introduced for the bed shear stress due to the combined effect of waves and currents. The formulation of bed shear stress used to calculate the sink/source terms is modified based on previous research that sufficiently validated the formulation with measurement data. The integrated model of the above-mentioned models is applied to simulate sediment transport in Hangzhou Bay. The results of the simulation agree well with field observations concerning the distribution of suspended sediment, indicating that the sediments are remarkably suspended in Hangzhou Bay under the action of waves and currents. 相似文献
4.
本文基于OpenFOAM建立三维波浪数值水槽,模拟计算植被水域波浪作用下的床面切应力,分析了入射波高、植被密度、植被淹没高度、水流对植被水域波浪作用下床面切应力的影响。结果表明:纯波时,由于植被的阻水作用,植被水域床面切应力沿程衰减,其衰减程度与入射波高、植被密度及植被淹没高度呈现正相关;与纯波时相比,在波浪和同向流共同作用下正向床面切应力幅值增大,负向床面切应力幅值减小;弱水流对植被水域床面切应力的大小及分布无明显影响;强水流时,床面切应力在植被水域先增大后逐渐减小并在植被水域后显著降低。 相似文献
5.
The intertidal erosion rate of cohesive sediment: a case study from Long Island Sound 总被引：2，自引：0，他引：2
Over the past decades, many attempts have been made to generate useful bottom erosion models for the study of cohesive sediment movement. This study addresses some of the key questions involved in determining the functional relationship between erosion rate and bottom shear stress. Current, wave, and turbidity data were collected from a bottom mounted instrument array in a moderately energetic estuarine environment. The bottom shear stress was calculated from a wave–current interaction model. The erosion rate was derived from the observed sediment concentration using a vertical mixing model. Examination of the relationship between erosion rate and bottom stress showed that the erosion rate varied at intertidal frequency. When averaged over the tidal fluctuation, the erosion rate remained approximately constant at low stress, but increased sharply when the shear stress rose above a critical value. This suggests two-stage erosion. The bed has a layered structure, in which a thin layer of loose, high water content material overlies a more consolidated bed. The top layer of high water content material (fluff) was easily disturbed and re-suspended by tidal currents, but the consolidated bottom layer was eroded only under conditions of high shear stress. 相似文献
6.
7.
在河口海岸工程中,常常会面临岸滩冲蚀、岸线演变、航道淤积、建筑物底部淘刷等涉及泥沙起动和输运的问题,而水流对底床的剪切力是研究泥沙起动与输运的重要参数。本文利用自行设计的底床剪切力测量装置,在不同流速的水流中,分别在固定砂床(定床)和可移动砂床(动床)上进行了底部剪切力的直接测量;同时,根据试验中声学多普勒流速仪(ADV)测得的流速信息,采用湍流动能法对底床剪切力进行了估算。结果显示:当比例系数取值0.19时,估算出的底床剪切力与测量值吻合较好。对测量结果进行分析后发现,流速较小、砂粒未起动时,动、定砂床上的底部剪切力大致相同;在有砂粒起动的情况下,动床上的底部剪切力比定床上的大,相对差值最大约20%。因此当涉及底床剪切力的问题时,需要先确认床面形式,然后再进行分析研究。 相似文献
8.
海底沉积物再悬浮及其分布取决于海洋水动力、沉积物类型与床面形态之间复杂的相互作用,准确地理解和确定沉积物再悬浮过程对于沉积物输运的研究具有重要的意义。本文在祥云湾海洋牧场典型海域开展现场原位观测,获取研究区波浪、海流及悬浮沉积物浓度数据;分析了波、流作用下海底边界层悬浮沉积物垂向分布特征,并探究了海洋水动力和床面形态对悬浮沉积物垂向分布的影响。结果表明,研究区波流之间的相互作用不显著,沉积物再悬浮受控于风暴浪作用,风暴浪作用下底床切应力可以达到沉积物临界切应力的10～15倍,沉积物的再悬浮滞后于风暴浪作用2～3 h。在波浪荷载微小的情况下,悬浮沉积物垂向分布呈现"I"型,波浪荷载下,悬浮沉积物垂向分布呈现幂指函数分布,表现为"L"型;床面形态随波、流作用而演化,影响沉积物的再悬浮过程,u_(?w)/u_(?c)=1.00可作为波浪和海流起主导控制作用的床面形态的判别依据,纯波浪荷载作用下的u_(?w)/u_(?c)显著高于波浪主控作用下,但二者之间的界线随着波浪荷载的增加而升高。 相似文献
9.