反调节水库非恒定流数值模拟          下载免费PDF全文

魏根群  陈璧宏  宿晓辉 《水科学进展》2001,12(4):491-498

采用二维水深平均方程组作为控制方程,利用边界拟合法进行坐标变换,采用有限体积法计算反调节水库的流场。在计算中,由于已知上游泵站抽水流量及下游枢纽供水流量,且上下游均找不到水位流量关系,上下游边界均为流速边界条件,没有压力边界条件,解不惟一,所以采用全水库水量平衡方程作为补充方程来补充定解条件。  相似文献   

A New Methodology for Singularity Modelling in Flow Simulations in Reservoir Engineering     

Y. Ding  L. Jeannin 《Computational Geosciences》2001,5(2):93-119

In this paper, numerical methods for flow simulation in the well vicinity are discussed. Flux truncation errors are analyzed on gridblocks near the well. Due to the singularity of the well, standard numerical schemes are not efficient for near well flow simulations. To improve simulation accuracy, a new methodology, using a change of coordinates to make near well pressure linear, is presented for the singularity modelling. Based on this new approach, two numerical schemes, a two-point flux approximation scheme and a multi-point one, are proposed. These schemes are accurate for the near well modelling and are suitable for any kinds of gridblocks.  相似文献   

The perimeter-area fractal model and its application to geology   总被引：14，自引：0，他引：14  

Qiuming Cheng 《Mathematical Geology》1995,27(1):69-82

Perimeters and areas of similarly shaped fractal geometries in two-dimensional space are related to one another by power-law relationships. The exponents obtained from these power laws are associated with, but do not necessarily provide, unbiased estimates of the fractal dimensions of the perimeters and areas. The exponent (D_AL) obtained from perimeter-area analysis can be used only as a reliable estimate of the dimension of the perimeter (D_L) if the dimension of the measured area is D_A=2. If D_A<2, then the exponent D_AL=2D_L/D_A>D_L. Similar relations hold true for area and volumes of three-dimensional fractal geometries. The newly derived results are used for characterizing Au associated alteration zones in porphyry systems in the Mitchell-Sulphurets mineral district, northwestern British Columbia.  相似文献   

Tracer measurements in groyne fields for the quantification of mean hydraulic residence times and of the exchange with the stream     

Hans‐Peter Kozerski  Ren Schwartz  Thomas Hintze 《洁净——土壤、空气、水》2006,34(3):188-200

Tracer experiments were carried out in groyne fields (GF) of the river Elbe near Havelberg (Germany) in order to estimate the hydraulic connectivity with the river channel. The characteristic times of the five groyne fields, which were estimated from the exponentially declining tracer curves in 43 runs, ranged between 15 min and 69 min and did not correlate with the water level. Methodological investigations show that single point injection and two measurements (in the outflowing water and in the dominant region) are sufficient to provide robust in‐situ tracer curves. Using simplified mathematical simulations with connected stirred tanks, the conditions are investigated for the development of breaks in tracer curves and for the occurrence of significant errors in the estimation of intrinsic residence times. It was shown that an initial uniform dye distribution is not mandatory for the estimation during steady states. In special cases, point injections are more advisable. Moreover, the mean hydraulic residence time was found to be not equivalent to the estimated characteristic time. In fact, it is mostly overestimated by tracer experiments. The degree of overestimation depends on mixing and the volumetric proportions between the different parts of the GF and can be calculated from measured dye concentration differences. For example, an overestimation of 32% was calculated for a groyne field with a commonly found circulation flow pattern.  相似文献   

洞庭湖泥沙淤积数值模拟模式   总被引：4，自引：0，他引：4       下载免费PDF全文

施勇  栾震宇  胡四一 《水科学进展》2006,17(2):246-251

在确保沙量守恒的非恒定流、非均匀沙的二维水沙数学模型的基础上,通过洞庭湖水沙输运和河床变形计算实践,比较了两种冲泻质与床沙质的转化模式,提出了包括冲泻质在内的泥沙淤积模式和水沙动边界计算模式.从洞庭湖泥沙输运和河床变形计算的结果看,洞庭湖泥沙淤积数值模式具有较好的稳定性和较高的模拟精度,说明所建湖泊泥沙模型的良好性能和具有推广运用的前景.  相似文献   

地图信息量的量测和评价     

张法 《四川测绘》2006,29(1):21-24

本文介绍了测度地图信息量的原理及方法,提出一种测度地图信息量的改进方法—特征信息量法,并在1:1万、1:5万、1:25万、1:100万地形图上分别选出图上100 cm2、实地域相重的三种地区,即居民地稀疏区(高山)、居民地中密区(丘陵)、居民地稠密区(平原)进行试验,最后对地图信息量进行评价并提出改进意见。  相似文献   

长江中下游河道冲淤演变的防洪效应          下载免费PDF全文

徐照明  徐兴亚  李安强  张黎明  胡春燕 《水科学进展》2020,31(3):366-376

近年来长江中下游来沙量持续减少,河道面临长距离、长历时的冲淤调整,河道蓄泄关系发生变化,对防洪造成影响。在长江中下游河道冲淤及其蓄泄能力变化预测成果的基础上,对比计算了现状和未来河道蓄泄能力条件下,遇1954年洪水,长江上游水库防洪调度和中下游地区超额洪量的变化情况。结果表明,未来随着长江中下游河道进一步冲刷,河道槽蓄容积增加,相同防洪控制水位下的河道安全泄量增大,三峡水库在进行防洪调度时可下泄流量增大,总拦蓄洪量减小,长江中下游地区总超额洪量减小,但超额洪量在地区分布上存在从上游向下游转移的情况。  相似文献   

三维地理信息系统中几何特征的误差模型   总被引：1，自引：0，他引：1  

史文中 《武汉大学学报(信息科学版)》1998,(1)

本文提出了三维地理信息系统中几何特征的误差模型。基于面表示的三维ＧＩＳ的特征被分为点、线段及线,该模型给出这些特征的一种误差描述,即围绕着这些几何特征的量测值的一个范围。  相似文献   

中国数字地震台网数据管理中心日常工作软件的升级和应用     

邹立晔  郭燕平 《地震地磁观测与研究》1998,19(3):60-69

文中阐述了中国数字地震台网数据管理中心（ＣＤＳＮ ＤＭＣ）日常工作软件的升级和升级后新软件的主要功能,并结合新软件的主要命令及运行实例,对升级后软件的实际应用作了简要叙述。  相似文献   

Numerical simulation of NAPL flow in the subsurface     

L.K. Kuiper  T.K. Illangasekare 《Computational Geosciences》1998,2(3):171-189

A three-dimensional, three-phase numerical model is presented for simulating the movement of immiscible fluids, including nonaqueous-phase liquids (NAPLs), through porous media. The model is designed to simulate soil flume experiments and for practical application to a wide variety of contamination scenarios involving light or dense NAPLs in heterogeneous subsurface systems. The model is derived for the three-phase flow of water, NAPL, and air in porous media. The basic governing equations are based upon the mass conservation of the constitutents within the phases. The descretization chosen to transform the governing equations into the approximating equations, although logically regular, is very general. The approximating equations are a set of simultaneous coupled nonlinear equations which are solved by the Newton-Raphson method. The linear system solutions needed for the Newton-Raphson method are obtained using a matrix of preconditioner/accelerator iterative methods. Because of the special way the governing equations are implemented, the model is capable of simulating many of the phenomena considered necessary for the sucessful simulation of field problems including entry pressure phenomena, entrapment, and preferential flow paths. The model is verified by comparing it with several exact analytic test solutions and three soil flume experiments involving the introduction and movement of light nonaqueous-phase liquid (LNAPL) or dense nonaqueous-phase liquid (DNAPL) in heterogeneous sand containing a watertable. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献