Three‐dimensional flow structure around small‐scale bedforms in a simulated gravel‐bed environment

Pebble clusters are common small‐scale morphological features in gravel‐bed rivers, occupying as much as 10 per cent of the bed surface. Important links exist between the presence of pebble clusters and the development of flow structures. These links are poorly understood at the three‐dimensional level. Particularly neglected has been the effect of clusters on the lateral flow characteristics. A laboratory study was conducted using a hydraulic flume, within which simulated pebble clusters were superimposed onto a plane bed of gravel material. High‐resolution three‐dimensional flow data were collected above the bed at two different flow depths using an acoustic Doppler velocimeter. The results present evidence of the importance of lateral flow in the development of turbulent flow structure. Narrow regions of high lateral and downstream turbulence intensity exist to both sides of clusters and in a three‐dimensional separation zone in their lee. This may indicate the presence of horseshoe‐type vortical structures analogous to those identified in less hydraulically rough environments. However, it is likely that these structures are more complicated given the mutual interference of the surrounding medium. The lateral flow was also identified as a key component in the upwelling identified by other authors in the lee of pebble clusters. The results of the vertical flow analysis confirm the hypothesis that six regions with distinct vertical flow characteristics exist above clusters: flow acceleration up the stoss‐side of the cluster; recirculation behind the cluster in the wake region; vortex shedding from the pebble crest and shear layer; flow reattachment downstream of the cluster; upwelling of flow downstream of the point of reattachment; and recovery of flow. Copyright © 2001 John Wiley & Sons, Ltd.     

辽东湾丛式钻井陀螺侧钻及导向钻井防碰技术

本文介绍渤海辽东湾实验区AI平台丛式定向井最后钻完的3口侧钻绕障井。在有邻井和本井套管磁干扰情况下,特别是与邻井间距最小仅为0.6m,采用陀螺定向侧钻以及导向钻井技术相结合,安全顺利的钻完了这3口井。总结和介绍了侧钻、防碰的工艺特声,以及安全措施。研究和分析了使用陀螺定向侧钻,钻速与造斜率,井眼轨迹合理控制等问题。     

湖南境内沿倾向发育较深的脉状矿床的地质特征及规律

湖南省境内有些脉状矿床，沿倾向延伸的长度为水平长度的数倍，而且还有侧伏规律。若脉状矿床发育于缓倾角的断层带上时，矿脉往往受断层上盘板岩、断层带上的泥质的或硅质的断层胶结物所控制，矿脉则发育于其下面；若矿脉发育于高角度的断裂裂隙中时，则矿脉往往是相互平行的多条，且呈雁行排列。这些特点和规律，对地质勘查具有指导意义。     

新城－黄陂走滑韧性剪切带的动力分异作用

本文通过对新城－黄陂断裂带中合河－殷店右行走滑韧性剪切带内糜棱岩类岩石化学成分、稀土元素及微量元素随Ｓｓ－Ｓｃ夹角和古差异应力（△δ）的变化梯度的研究，初步探讨了右行走滑韧性剪切带的动力分异作用。     

对穿时普遍性的解释

穿时是沉积地层的基本属性,其根本原因是地层的形成作用,即沉积作用本身。有沉积作用就有穿时(侧向加积);或者小范围内不穿时但大范围内必穿时(纵向加积)。海水进退只能影响穿时的具体形式而不是穿时的本质原因或必要条件。板块的运移和增生不仅造成了沉积地层的穿时,还造成了火山地层的穿时。这种穿时与沉积作用直接引起的穿时有本质不同,本文称之为构造穿时。     

SILTATION RATE IN A TRENCH DREDGED ON FLOODPLAIN IN ESTUARY

I. INTRODUCTIONA discharge of 100--200 m3 / s is needed to be diverted from a tidal reach and utilized as cooling water for a Droposed power plant in the Yangtze Estuary. The diversionchannel is divided into two parts by a levee along the river bank, an open channel stretchinside the levee is connected with a trench dredged on the floodplain, as shown in Pig. 1.Since the flow and sediment regimes in these two stretches are different, analysis is madeseparately for each of them.11. ESTI…     

Lateral heterogeneities in the upper and mid-mantle conductivity in Argentina

Regional studies of Sq variations measured at five permanent observatories in Argentina were performed to estimate the distribution of the electrical conductivity of the upper and mid-mantle, reaching a depth of approximately 800 km. After separating the total field into its parts of external and internal origin, the in duced field was modeled, applying two-dimensional techniques. Additionally, induction arrows and an equivalent apparent resistivity curve were calculated A north-south heterogeneity was detected, showing an increase of the conductivity of the shallower layers north of the profile, which may be related to the presence of high volcanic activity in the area.Also at CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas).