Coupled simulation of transient bed evolution in alluvial channels

Abstract

In dealing with the transient sediment transport problem, the commonly used uncoupled model may not be suitable. The uncoupling technique is intended to separate the physical coupling phenomenon of water flow and sediment transport into two independent processes. Very often, as a result, severe numerical oscillation and solution instability problems appear in the simulation of transient sediment transport in alluvial channels. The coupled model, which simultaneously solves water flow continuity, momentum and sediment continuity equations, gives fewer numerical oscillation and solution instability problems. In this article, a coupled model using a matrix double-sweep method to solve the system of nonlinear algebraic equations has been developed. Several test runs designed on the basis of a schematic model have been performed. The numerical oscillation and solution instability problems have been investigated through a comparison with those obtained from an uncoupled model. Based on the proposed case studies, it can be concluded that, for transient bed evolution, the performance of the coupled model is much better than that of the uncoupled model. The numerical oscillation is reduced and the solution is more stable. This newly developed coupled model was also applied to the Cho-Shui River in Taiwan. This application study implied that the effect of the peaky flood wave propagation on the bed evolution could be simulated better by the coupled model than by the uncoupled model.     

华北地区GPS地壳应变能密度变化率场及其构造运动分析

利用GAMIT软件将华北地区GPS地壳形变监测网1995、1996及1999年3期观测数据同全球IGS跟踪站资料进行了统一处理,并采用基线向量单天解及其全协方差矩阵和武汉大学PowerAdj Ver3.0软件在ITRF97框架下进行了GPS网整体平差,得出了相对于欧亚板块的水平运动速度场;进一步利用GPS速度场计算华北地区GPS地壳应变率场及应变能密度变化率场. GPS结果表明:华北地区现以(3-12mm/a)±3.4mm/a速度相对于稳定的欧亚板块向东或东南方向运动;唐山-河间-磁县是一个压缩活动边界,大同-太原则是一拉张活动边界,呈略带右旋的拉张运动;北京-天津-渤海湾地区,以及邢台地区是高剪应变率地区;张家口-北京-天津-渤海湾地区,以及济南地区是高应变能密度变化率地区,地壳积累能量高,且渤海湾地区处于面膨胀变化率正、负值过渡带,那里可能存在与地震危险性有关的应变能积累背景.     

华北地区GPS地壳应变能密度变化率场及其构造运动分析

利用GAMIT软件将华北地区GPS地壳形变监测网1995、1996及1999年3期观测数据同全球IGS跟踪站资料进行了统一处理,并采用基线向量单天解及其全协方差矩阵和武汉大学PowerAdj Ver3.0软件在ITRF97框架下进行了GPS网整体平差,得出了相对于欧亚板块的水平运动速度场;进一步利用GPS速度场计算华北地区GPS地壳应变率场及应变能密度变化率场. GPS结果表明:华北地区现以(3-12mm/a)±3.4mm/a速度相对于稳定的欧亚板块向东或东南方向运动;唐山-河间-磁县是一个压缩活动边界,大同-太原则是一拉张活动边界,呈略带右旋的拉张运动;北京-天津-渤海湾地区,以及邢台地区是高剪应变率地区;张家口-北京-天津-渤海湾地区,以及济南地区是高应变能密度变化率地区,地壳积累能量高,且渤海湾地区处于面膨胀变化率正、负值过渡带,那里可能存在与地震危险性有关的应变能积累背景.     

根据重、磁资料探讨中国东部及其邻域断裂体系

对中国贺兰山－龙门山以东的中国陆、海及其邻域，在分析地球物理场特征的基础上进行断裂体系研究．基本以重、磁资料为基础，结合地质资料，重点讨论断裂构造，进而揭示出断裂体系主要分为板块边界断裂带、块体边界断裂带和块体内部断裂带．这些断裂反映出研究区＂东西成带、南北分块＂的特征。     

A generalized solution for groundwater head fluctuation in a tidal leaky aquifer system

A new analytical solution is developed for describing groundwater level fluctuations in a coupled leaky confined aquifer system which consists of an unconfined aquifer, confined aquifer, and an aquitard in between. The aquifer system has a tidal boundary at the seashore, a no flow boundary at remote inland side, and a confined aquifer extending under the sea and terminated with an outlet-capping. This new solution has shown to be a generalisation of most existing analytical solutions for a tidal aquifer system which includes single confined and leaky confined aquifers. In addition, the solution is used to explore the influences of the dimensionless leakance of the outlet-capping, the dimensionless hydraulic diffusivities, and the leakages of the inland and offshore aquitards on the head responses in the leaky confined aquifer.     

Nearshore Wave Field Analysis Using SAR Images

1 .Ｉｎｔｒｏｄｕｃｔｉｏｎ1ＴｈｉｓｓｔｕｄｙｗａｓｓｕｐｐｏｒｔｅｄｂｙＮＳＣｉｎＴａｉｗａｎｕｎｄｅｒｔｈｅｐｒｏｊｅｃｔＮｏ .ＮＳＣ 89 2 611 Ｅ 0 0 6 0 4 0 . Ｃｏｒｒｅｓｐｏｎｄｉｎｇａｕｔｈｏｒ.Ｅ ｍａｉｌ:ｄｊｄｏｏｎｇ @ｐｃｈｏｍｅ .ｃｏｍ .ｔｗ　　Ｏｃｅａｎｗａｖｅｓ ,ｗｈｉｃｈａｒｅｅｘｔｒｅｍｅｌｙｒａｎｄｏｍ ,ａｒｅｄｉｒｅｃｔｌｙａｎｄｉｎｄｉｒｅｃｔｌｙｄｅｐｅｎｄｅｎｔｏｎｍｅｔｅｏｒｏｌｏｇｉ ｃａｌ,ｈｙｄｒｏｌｏｇｉｃａｌ,ｏｃｅａｎｏｇｒａｐｈｉｃａｎｄｔｏｐｏｇ…     

Analysis of Wave Directional Spreading by Bayesian Parameter Estimation

A spatial array of wave gauges installed on an observatoion platform has been designed and arranged to measure the lo-cal features of winter monsoon directional waves off Taishi coast of Taiwan. A new method, named the Bayesian Parameter Estimation Method(BPEM) , is developed and adopted to determine the main direction and the directional spreading parame-ter of directional spectra. The BPEM could be considered as a regression analysis to find the maximum joint probability of parameters, which best approximates the observed data from the Bayesian viewpoint. The result of the analysis of field wave data demonstrates the highly dependency of the characteristics of normalized directional spreading on the wave age. The Mit-suyasu type empirical formula of directional spectrum is therefore modified to be representative of monsoon wave field. More-over, it is suggested that Smax could be expressed as a function of wave steepness. The values of Smax decrease with increas-ing steepness. Finally, a local directi     

贵港市气象诱因地质灾害监测预测系统

地质灾害诱发因素中降雨是主要的因子之一,通过建设中尺度自动站网络收集基础数据,建立地质灾害预报工具,提高地质灾害预报准确率,建立地质灾害工作平台,实现部门之间的资料共享和会商。     

黑潮-亲潮交汇区涡旋演变调控作用下的叶绿素三维特征

黑潮-亲潮交汇区普遍存在的涡旋运动,可通过物质输运和再分配调控叶绿素浓度的时空演变,进而影响该海域的海洋生态环境。基于卫星高度计资料和叶绿素再分析数据,利用流矢量、归一化复合分析等方法,构建不同类型涡旋的各个演变阶段、不同水平尺度范围内,对应的叶绿素浓度三维结构,分析探讨黑潮-亲潮交汇区涡旋运动对叶绿素浓度时空演变的调控作用。结果表明,冷涡区（300 m以浅,3倍半径范围）的叶绿素浓度高值区,自下而上,逐渐扩展至涡心西北方向,且随着深度的增加,叶绿素浓度先增后减。随着气旋涡的演变,各水层叶绿素浓度高值由外向内,逐渐向涡心扩展,而平均半径内的叶绿素浓度输运总量在其稳定期达到最高。暖涡影响范围内的叶绿素浓度总体比冷涡区稍高,其垂向大致呈递减趋势,由上而下,叶绿素浓度低值大致由涡心东南向西北扩展,且随着反气旋涡的演变,叶绿素浓度高值逐渐向涡旋边缘聚集。