Transient‐state groundwater flow in various geometries with wells at arbitrary positions: analytical methods

We have developed a method for analytically solving the porous medium flow equation in many different geometries for horizontal (two‐dimensional), homogeneous and isotropic aquifers containing impermeable boundaries and any number of pumping or injection wells located at arbitrary positions within the system. Solutions and results are presented for rectangular and circular aquifers but the method presented here is easily extendible to many geometries. Results are also presented for systems where constant head boundary conditions can be emulated internal to the aquifer boundary. Recommendations for extensions of the present work are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

瞬变电磁法在断层含水性评价中的应用

本文介绍了瞬变电磁法在煤矿水文地质勘探中的具体应用效果.采用瞬变电磁法对落差较大断层的含(导)水性进行测量,不仅可有效地控制断层的空间位置,而且可定性地判断断层的富水性,其测量结果与已知水文地质资料吻合较好.     

Multiple bipolar structure of normal magnetic field at the magnetopause

We describe how a local plasma structure can be changed by a transverse shear flow using numerical simulation to investigate the disturbance process near the magnetopause. The results show that magnetic field lines are bent by transverse shear flow disturbance near the current sheet region. There are multiple bipolar structures of the normal magnetic field in the numerical simulation. We term this new feature as K-point magnetic reconnection, realistic for discussing space observations.     

中尺度地形扰动的非线性问题半解析解

将大气和海洋中f-平面上中尺度地形的扰动问题统一起来作为一个地球物理流体力学问题，应用涡度、能量和经圈动量守恒条件，将原来高度非线性方程变成一个二阶椭园型非线性方程，用数值模拟方法分析了大气中的过山运动和海洋中的沿岸上升流，给出了与观测接近的模拟结果以及运动过程对内部物理参数和外界条件的敏感性分析。所提方法可供进一步的动力学分析和数值研究参考。     

Sediment-activation depth values for gentle and steep beaches

This paper analyzes methods and terminologies used in literature for the determination and characterization of vertical distribution of sediment-activation depth, which is bottom sediment layer affected by hydrodynamic processes. Studies on this topic include assessments carried out during short time spans, from minutes to few hours or longer periods, from a tidal cycle to several days. In the first case, activation is generally named “mixing depth” and is calculated by evaluating vertical distribution of fluorescent tracers. In the second case, it is referred to as “disturbance depth” and is generally evaluated using plugs of marked sand and rods, or rods with a loose-fitting washer. Vertical cross and longshore distribution of mixing and disturbance depth values, recorded in different works with different techniques, were also analyzed highlighting the conceptual differences between used methods and obtained results. In a further step, a data set from literature on this topic was gathered to obtain new formulations between disturbance depth and beach and wave characteristics as well as morphodynamic beach state, expressed throughout the surf scaling parameter and the surf similarity index. Good linear regressions were observed between these variables, obtaining expressions that can be easily used in a wide range of beach states, from dissipative and intermediate to reflective ones.     

大地形对正压扰动演变影响

本文着重研究大地形对正压大气迭加在非均匀纬向基本气流上挑动演变的影响。用WKBJ方法推导了正压扰动的频率和频散关系以及波作用量所满足的方程。当基本流场定常且存在无限长的东西向山脉时,则有波作用量守恒。据此,获得了正压不稳定的必要条件:即在所考察的平面域内至少在某点或某些点上含地形效应的某一物理量等于零,扰动就可能得到发展。对波包动能的倚时变化的讨论得知,在无摩擦正压纬向非均匀基流的情形,地形对扰动动能并无直接影响,即导波和曳波分别在西风急流的南侧和北侧得到加强,并分别在西风急流的北侧和南侧强度减弱。扰动的发展由扰动的结构所决定。导波和曳波的波长缩短总伴同其轴线倾向于东西向相联系,而它们的波长伸长总是与其轴线倾向于南北向同时发生。还指出,正压扰动的加强(或减弱)与波长的伸长(或缩短)不是必然的联系,它的成立是有条件的。     

Sample Disturbance in Soft and Sensitive Clays: Analysis and Assessment

Despite the sophisticated methods employed to obtain high quality samples, they are prone to disturbance, due to stress release, let apart, due to sampling tools and techniques adopted. Critical reappraisal of different methods suggest that any method of sample quality assessment involving strength and deformation parameters would enable easier implementation and correct other engineering parameters for estimated sample disturbance. In this technical paper, sample disturbance index, using merely the slopes of compression paths, (representing mechanical response), in the pre- and post-yield stress regimes under odeometric loading conditions is proposed. This method is based on single oedometer test results on samples of unknown degrees of disturbance during sampling and handling. The unique feature of this approach is that the ideal rigid plastic material behavior is taken as reference. This eliminates the need for any additional experimental data or any calculations from the relationships formulated with any set of assumptions.     

Numerical modeling of long waves in shallow water using Incremental Differential Quadrature Method

Incremental Differential Quadrature Method (IDQM) as a rapid and accurate method for numerical simulation of Nonlinear Shallow Water (NLSW) waves is employed. To the best of authors’ knowledge, this is the first endeavor to exploit DQM in coastal hydraulics. The one-dimensional NLSW equations and related boundary conditions are discretized in space and temporal directions by DQM rules and the resulting system of equations are used to compute the state variables in the entire computational domain. It was found that the splitting of total simulation time into a number of smaller time increments, could significantly enhance the performance of the proposed method. Furthermore, results of this study show two main advantages for IDQM compared with other conventional methods, namely; unconditional stability and minimal computational effort. Indeed, using IDQM, one can use a few grid points (in spatial or time direction) without imposing any stability condition on the time step to obtain an accurate convergent solution.     

龙口港湾大振幅假潮的成因分析

龙口湾位于山东半岛北部,莱州湾东北隅,为莱州湾的一个附属海湾.海湾湾口朝向西南,湾廓近似半圆形,属半封闭海湾.龙口验潮站位于湾顶(图1),水深7m.