WAVE BOTTOM LAYERS DYNAMIC WITH SUSPENDED SEDIMENT OVER VORTEX RIPPLES

Vortex ripple is widely formed in the coastal region, and the dynamic of vortex is quite important because it is responsible for sediment transport. The flow structure around the vortex ripples can be modeled as 2D flow due to the geometry of the flow boundaries. In this paper, 2D Large-Ed-dy-Simulation (LES) method was used to predict the flow structure and the dynamic of vortex in the bottom layers under the action of the wave, the numerical simulation results show a completely process of vortex formation, evolvement and disappearance. Based on the study of flow structure, the suspended sediment transport was modeled in present paper. The simulated sediment concentrations were compared to measurements from the literature. The agreement between the time averaged simulated concentration profiles and measurements is satisfactory. For a high setting velocity, the suspended sediment is confined to the vicinity of the bed, and it is dominated by the local bottom shear stress. For a small setting velocity, the suspension is more dominated by the characteristic of vortex. There are two suspended sediment transport peaks observed in the cross-section at the trough and crest in the half period, the second peak is due to the separation bubble taking the sediment.     

水泵站进水池物理模型试验研究

为评估某海水取水泵站的布置设计,对其进行物理模型试验研究.在建模时,需要合理选择模型比尺,使模型与原型符合动力相似,几何相似和运动相似,并正确重现泵吸进口的涡流作用.为了促进系统良好的运行,采取措施对以下几个方面进行测量:设施内的水位,来自每个泵位置的流量,来流类型与水流分布,泵吸处的流速情况,泵室内部的涡流作用.次测试来流分布较差,出现了预旋和旋涡.通过对旋涡出现的原因进行分析,采取了不同的改良措施,有效消除了这些不良现象,保证了泵站取水安全.     

渤海湾海岸古气候环境及其对海岸变迁的影响

以渤海湾西岸这一典型淤泥质海岸为背景,从研究古气候环境出发,利用相关考古资料和前人的成果,重建渤海湾西岸全新世以来的气候环境,得到渤海湾的气候变化情况.通过分析孢粉化石资料,初步恢复渤海湾地区4个特征位置的古气候、古环境.针对渤海海域水环境,建立距今2500～2000年前、距今1000年前和公元2004年的渤海二维潮流数学模型,通过分析流场变化构建出从古至今海岸变迁演变过程(冲淤演变).研究古气候环境变化与海岸变迁的关系,探索古气候环境影响下的海岸变迁的内因和外延,综合古气候变化、海平面变化等影响因素,总结得出渤海湾海岸古气候环境(温度、降水、潮流风浪等)对海岸变迁的影响,并对未来海岸线的变化趋势进行预测.     

长江口深水航道回淤二维数值模拟分析

长江口深水航道整治工程位于长江口北槽,分三期完成。工程实施后,航道内每年均出现严重回淤现象,航道疏浚维护费用巨大。通过建立长江口深水航道二维数学模型,计算了1997、2001、2005、2009年4个不同时间段典型断面涨落潮流量,分析了长江口深水航道工程实施期间涨落潮流量的变化情况,探讨了航道回淤的原因。一期工程使航道中段落潮流量减小而上段落潮流量增加,二期工程后航道整体落潮流量减小,三期工程的实施减缓了航道落潮流量减小的趋势,而航道内落潮流量的减小可能是出现严重回淤的水动力原因。     

Composition and mechanical characteristic of riverbed soil in lower Yellow River

Yellow River is a typical wandering channel with large sediment content. Lack of systemic data about composition of riverbed and indexes of mechanical characteristic, the influence of composition and indexes of mechanical characteristic of riverbed was considered difficultly in physical and mathematical models. Mechanical characteristic of soil considered, identification standard of soil layer about riverbed was carried out based on strength resistance of cone tip and the ratio of friction resistance between lateral cone and cone tip, and comparative analysis is worked out with identification standard of indoor geotechnical test. Taking the typical wandering section of river from Baihe to Yiluo outfall as the example, cone penetration tests were carried out and indoor tests were worked out. Firstly, huge data about composition and mechanical characteristic of riverbed are achieved, it shows that the main components of riverbed in lower Yellow River are silty clay, silty loam, sandy loam, sand and so on. Secondly, physical and mechanical indexes of riverbed soil keep strong regularity. Finally, formation cause and change trend are achieved through the basic data of riverbed soil, thus it will improve the development of technology of (Line No. 1) physical model and numerical method for river research (Line No. 2).     

黄河下游高村-陶城铺河段边界阻力能耗与河床稳定性分析

从河床边界阻力能耗角度研究河床形态调整规律,引入河床稳定性指标,探讨与边界阻力能耗率的相关性。以黄河下游高村至陶城铺河段为研究区域,采用实测资料、理论解析与数值模拟相结合方法,基于不同年份河道地形,计算出不同流量条件下的水力要素与边界阻力能耗率,分析河床形态调整过程及边界阻力能耗率响应,讨论了边界阻力能耗率与河床稳定性关系。结果表明：边界阻力能耗率沿程均值和波动强度随着流量增大而增大;阻力能耗率随着过水面积或宽深比呈先减小后增大趋势,且与河床稳定指标呈正相关关系,但能耗率趋近最小值时,河床也可能发生下限失稳。通过优化河床断面形态,维持河床稳定情况下寻求边界阻力能耗率最小,能够提高河槽的输水输沙能力。     

不同入射角对河流弯曲演变的影响

水流经一定的入射角进入河道后,引起横、纵向的泥沙运动,导致床面形态发生剧烈变化,这对河道初始阶段的弯曲演变具有显著影响。通过自然模型实验的方法,借助模型小河来探讨这一过程。实验表明,入射角对河道初始阶段的弯曲演变具有显著作用,入射角改变了起始阶段的弯曲度和输沙规律,加速了河弯的出现,且随着入射角的增大,河道的弯曲度呈增...     

常曲率U型弯道水流结构与泥沙冲淤试验研究

通过在常曲率U型弯道水槽试验中采集的流速和水深过程数据,研究了弯道内水流结构及泥沙冲淤形态,分析了水流与床面之间的相互影响。试验发现:(1)弯道水流结构水面线发生扭曲,水流动力轴线及三个方向的垂线平均流速随流程和横向分布均有变化;(2)由于弯道特有的几何特征,使弯道中水流产生特有的弯道环流运动,弯道环流运动引起弯道泥沙的横向输移,形成弯道凹岸冲刷、凸岸淤积的冲淤特性,反之,床面形态的变化也使水流结构发生改变。研究所得结果可为河流泥沙研究提供参考。     

Shrinkage properties of compacted sand concrete used in pavements

Compacted sand concrete is being researched for potential usage in road construction because of shortage in gravel resources in many countries. However, one of the problems for this material with such application is shrinkage cracking. This paper presents the results of the unrestrained shrinkage test performed on three different compacted sand concrete mixes. Two existing shrinkage prediction models, namely the ACI 209 and the CEB 90, were used to fit the measured shrinkage data. The CEB 90 model with an application of a correction factor was found to perform well with compacted sand concrete. Based on the results of the shrinkage tests, joint spacing between compacted sand concrete slabs was calculated.