A Numerical Study on the Structure and Dynamics of Turbulence in Oscillatory Bottom Layer Flow over A Flat or Rippled Bed

1 .IntroductionUnder the influence of surface waves ,sandripples often appear on beaches . Whenthe amplitudeof water oscillationis sufficientlylarge ,vortices are formed onthe lee of every sand ripple crest . A-mongthese vortices ,the most important are t…     

砂质海岸岸滩侵蚀演变模式探讨——以山东南部海岸侵蚀岸段的岸滩演变为例

在分析山东南部海岸几十年来的地形观测资料的基础上，运用砂质海岸等深线变化预测理论，建立该区的岸滩侵蚀演变预测模型，研究了该区域岸滩演变规律。实测资料验证表明：预测结果合理，基本反映了本区岸滩演变的特征。     

Gradation affects basic mechanical characteristics of Chinese calcareous sand as airport subgrade of reefs

Abstract

Construction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content.     

16米风化砂回填地基的深层振密加固

结合北方某重力式深水 ( -1 6.0 m)码头沉箱后壁 1 4.5 m范围的回填风化砂经深层振密处理这一工程实例 ,介绍了回填砂振密的技术要求、施工工艺和方法及振密效果的检测。同时对施工与检测中的某些技术问题提出了自己的看法。     

中国海岸风成沙ESR测年的研究

介绍ＥＳＲ测年的基本原理，并讨论风成沙Ｇｅ心测年的可行性、风成沙Ｅ＇心的特征、测年误差及可靠性等问题。１９９２－１９９３年在渤、黄、东、南海沿岸采集的１００余个风成沙样品ＥＳＲ测年实验表明，绝大部分海岸风成沙的年龄为１－７万年。     

珠江口伶仃洋锋的类别及其对沉积的影响

根据近年在珠江口伶仃洋的观测资料，对比国外有关河口锋的定义，归纳了伶仃洋内几种锋的现象，计有潮侵锋、岬角锋及湖水退急时的浅滩锋等。解释了锋生的原因与潮汐进退，特别与随潮入侵的咸水关系。文中也探讨了这些锋对沉积环境的影响，认为它是陆架水入侵河口地区的一种不容忽视的沉积动力过程。     

黄河三角洲河道沉积规律研究Ⅱ. 建林边滩沉积作用机理

通过对建林边滩沉积物粒度分布、粒度参数及水体流变性质的分析，阐述了黄河三角洲上河道水流属于牵引流范畴，与低含沙水流无本质上的差别，并探讨沉积物搬运和沉积的基本特征。     

江苏岸外辐射沙脊群东沙稳定性研究

东沙是江苏岸外辐射沙脊群中的第二大沙洲,具有独特的地形地貌和水动力条件,对它进行稳定性研究为揭示整个辐射沙洲及其邻近岸滩的动态演变都非常有益。通过利用多年遥感卫片资料、1998年取得的现场水文泥沙观测资料和东沙滩面表层沉积物资料等,对东沙的地形地貌特征、沉积特征和东沙两侧潮汐通道的水流泥沙特征等进行了详细分析。研究结果表明,东沙的沙脊偏于西侧,西侧滩面较窄、高程较高且岸线较为顺直,东侧滩面较宽、高程较低且岸线较为破碎;西洋和陈家坞槽均处于冲刷状态,净输沙的主要方向为输向槽外或输向条子泥;东沙近三十年来面积有所缩小且有外围向中央收缩的趋势,尤其以向东、向南方向的迁移最为明显。     

底部浮泥表层推移速度分布的ADCP—GPS估测方法

ADCP对底跟踪走航观测的流速数据中包含水体底部浮泥、底沙运动信息,对比GPS定位方法算出的水体流速数据可以分离出浮泥相对于GPS定位的运动信号,从而达到对底质推移观测的目的。     

Two-Dimensional Mathematical Model of Tidal Current and Sediment for Oujiang Estnary and Wenzhou Bay

A 2-D mathematical model of tidal current and sediment has been developed for the Oujiang Estuary and the WenzhouBay. This model accomodates complicated features including multiple islands, existence of turbidity, and significant differ-ence in size distribution of bed material. The governing equations for non-uniform suspended load and bed load transport arepresented in a boundary-fitted orthogonal curvilinear coordinate system. The numerical solution procedures along with theirinitial conditions, boundary conditions, and movable boundary technique are presented. Strategies for computation of thecritical condition of deposition or erosion, sediment transport capacity, non-uniform bed load discharge, etc. are suggested.The model verification computation shows that, the tidal levels computed from the model are in good agreement with the fielddata at the 18 tidal gauge stations. The computed velocities and flow directions also agree well with the values measuredalong the totally 52 synchronously observed verticals distributed over 8 cross sections. The computed tidal water throughputsthrough the Huangda‘ao cross section are close to the measured data. And the computed values of bed deformation fromYangfushan to the estuary outfall and in the outer-sea area are in good agreement with the data observed from 1986 to 1992.The changes of tidal volumes through the estuary, velocities in different channels and the bed form due to the influence of thereclamation project on the Wenzhou shoal are predicted by means of this model.