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.     

Trace Elements Analysis of Geological Samples by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

ＩＮＴＲＯＤＵＣＴＩＯＮＬａｓｅｒａｂｌａｔｉｏｎｉｎｄｕｃｔｉｖｅｌｙｃｏｕｐｌｅｄｐｌａｓｍａｍａｓｓｓｐｅｃｔｒｏｍｅ ｔｒｙｉｓａｎｉｎｃｒｅａｓｉｎｇｌｙｄｅｖｅｌｏｐｅｄａｎａｌｙｔｉｃａｌｔｅｃｈｎｉｑｕｅｆｏｒｓｏｌｉｄｓａｍｐｌｅａｎａｌｙｓｉｓ.ＬＡ ＩＣＰ ＭＳｏｆｆｅｒｓａｔｔｒａｃｔｉｖｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｈｉｇｈｓｅｎｓｉｔｉｖｉｔｙ ,ｌｏｗｄｅｔｅｃｔｉｏｎｌｉｍｉｔｓ,ｍｉｎｉｍａｌｓａｍｐｌｅｐｒｅｐａｒａ ｔｉｏｎ ,ｌｅｓｓｏｘｉｄｅｓｉｎｔｅｒｆｅ…     

简单海气耦合的线性和非线性Rossby波

采用忽略Ｒｅｙｌｅｉｇｈ摩擦和Ｎｏｗｔｏｎ冷却的定常，线性大气模式和地转动量近似下的非线性海洋模式。这里包含了大气通过线性风应力影响海洋，海洋通过加热过程影响大气的物理机制。用相平面理论讨论了海气耦合作用对简单耦合线Ｒｏｓｓｂｙ波和非线性Ｒｏｓｓｂｙ波的影响。     

热带太平洋线性海气耦合系统的主模与ENSO

本文利用包含海洋表面边界层、线性海洋大气动力学以及完整的关于不均匀气候态线性化SST预报方程的热带太平洋海气耦合模式， 在真实的气候背景态和参数域内，研究了海气耦合系统的特征值问题，确定了线性耦合系统主模的特征周期及其稳定性特征，进而揭示了主模和ENSO的关系。结果表明:准两年振荡是线性海气耦合系统中的最不稳定模态，且只有该模态类似于ENSO水平结构。因此，准两年振荡很可能是海气耦合系统固有的最根本性的振荡过程。本文也对准两年振荡的形成与年循环的关系以及它在ENSO时间尺度形成中的作用进行了讨论。     

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。     

On the stability of a coupled ocean atmosphere system in the presence of wave-CISK

The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst (UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state, the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon is indicated.     

2D Coupled 3D:A New Numerical Model for Dual - Structured - Aquifer System

２Ｄ　Ｃｏｕｐｌｅｄ　３Ｄ：Ａ　Ｎｅｗ　Ｎｕｍｅｒｉｃａｌ　Ｍｏｄｅｌ　ｆｏｒＤｕａｌ－Ｓｔｒｕｃｔｕｒｅｄ－Ａｑｕｉｆｅｒ　Ｓｙｓｔｅｍ￥ＣｈｅｎＣｈｏｎｇｘｉ；ＦａｎｇＳｈｕｚｈｅｎ；ＬｉｎＭｉｎ（ＦａｃｕｌｔｙｏｆＥｎｖｉｒｏｎｍｅｎｔａｌＳｃ...