共查询到19条相似文献，搜索用时 453 毫秒
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定量评估冰川变化对干旱区流域/区域水资源管理、海平面上升以及冰川自然灾害预防等十分重要。从冰川产流(消融)和汇流两个水文物理过程出发,介绍了国内外冰川水文模型的研究进展,对目前应用最广的两类消融模型——基于气象因子的统计模型和基于物理机制的能量平衡模型进行了分析和讨论;从冰川表面、内部以及下部汇流3个方面阐述了冰川汇流模型所取得的成果。表明冰川产流(消融)模型已相对较为成熟,而冰川汇流过程目前仍处于探索阶段。构建适合不同规模和类型冰川的、包含冰川运动信息的分布式冰川水文物理模型是今后的研究重点。 相似文献
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国外汇流理论若干进展 总被引：3，自引：1，他引：3
一、引言汇流是在径流形成过程中发生的一种重要水文现象。汇流理论所研究的是河渠中、坡面上和流域内水流的不稳定运动。 1871年,圣维南提出了水流不稳定运动的基本微分方程组。从此开始了汇流理沦研究的水力学途径。 1931年,M·A·维利加诺夫提出了等流时线概念;1935年,G·T·麦片锡提出了马斯京根洪水演算法; 相似文献
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建立了适用于栅格单元系统的基于运动波理论的降尺度新安江模型(KWXAJ)。在栅格单元中采用新安江模型计算产流,运动波模型进行坡面汇流演算。模型中,为考虑上游坡地单元入流的径流入渗(run-on)效应,在进行坡地产流计算时,降雨及上游坡面流及壤中出流被同时作为来水输入新安江模型。在运动波模型中,糙率系数依据土地利用方式及洪水量级确定。选取淮河史灌河流域黄泥庄以上集水区域,作为研究区域。用流域历史上的13次洪水过程来率定和验证此模型。研究表明,run-on机制对流域产汇流预测有重要影响,其显著影响流域内土壤蓄水量时空分布,进而改变产汇流机制。数据分析还显示,不考虑run-on机制将导致模拟洪峰滞后。 相似文献
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为满足新形势下雨洪管理实践的需求, 揭示有效不透水下垫面对城市水文过程的影响, 需研发考虑有效不透水下垫面的城市雨洪模拟模型。将不透水下垫面分为道路和屋顶, 综合运用地理信息系统、城市雨洪模型等技术手段, 基于不同分类属性分步确定有效不透水面积; 考虑模型复杂性、建模数据可用性和模型预测能力, 确定模型结构。区分有效不透水下垫面和非有效不透水下垫面产汇流过程, 将具有高度异质性的城市下垫面离散成具有均匀或准均匀特性的子汇水区, 考虑不同下垫面各子汇水区内部及子汇水区之间汇流路径, 采用不同的产汇流计算方法, 构建了精细模拟模型, 可为城市洪涝防治及海绵城市建设提供技术支撑。 相似文献
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以介于微分方程和概率论之间的边缘数学分支随机微分方程的数学模型,对水库调洪过程中的随机现象和规律进行数学描述和分析,试图全面正确地综合各种不确定性因素对库水位随机过程的影响.根据水库蓄洪量具有Wiener过程特性的分析,推导了带有随机输入项和随机初始条件的调洪演算Ito方程.在此基础上,运用Fokker-Planck向前方程,求介了调洪过程库水位的概率密度分布.计算成果表明,运用随机微分方程进行水库的调洪演算,有利于正确分析水库调洪的随机过程和进一步开展水库泄洪风险分析. 相似文献
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一种新的概念性水文模型及其应用研究 总被引：1，自引：1，他引：0
传统的概念性水文模型描述降雨径流过程时做了很多简化,因此在实际应用中也存在许多不足之处.张文华对传统的产汇流模型做出了一些改进:将霍顿下渗能力曲线与实际的下渗曲线的有机联系在一起,建立了考虑前期土壤含水量和变雨强的产流计算方法;地下汇流计算增加考虑了地下径流量在进入含水层前的填蓄过程;地表汇流计算将等流时线法与单位线法有机地结合起来,从而同时考虑了下垫面的调蓄和推移作用;河道汇流采用非线性化的槽蓄方程进行演算.本文将张文华提出的一系列产汇流计算方法进行耦合,组成了一种新的概念性水文模型.模型主要由公式推导所得,物理机制较强,在长江中游龙河流域应用时峰现时差为2.5小时,确定性系数为76.6%,结果表明模型比较可靠. 相似文献
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为了提高传统径流汇流模拟的时效性,提出了一种基于通用计算的径流汇流模型。模型采用纳维-斯托克斯作为基础方程。首先,文章探讨了利用通用计算进行径流汇流模拟的实现方法并设计了模拟计算流程。然后,以涪江流域中段为研究区域,将流域内25个常规站和区域站的实况降水数据为数据源,分别利用本文径流汇流模型和FloodArea模型对流域进行径流模拟,并将两种模型模拟结果与水文站实测数据进行对比分析。结果发现,基于通用计算的径流汇流模型不仅在模拟效率上相对于FloodArea模型有很大程度的提高,而且模拟结果具有更小的水位变化误差,与水文站实测水文数据具有更好拟合效果。模拟时效性和结果准确性的同时提升表明本文的径流汇流模型对暴雨洪涝预警预报具有重要的意义。 相似文献
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B. P. Harlamov 《Mathematical Geology》2003,35(4):431-449
Zones of increased concentration formed by a solvent flowing from a source are considered. A matehmatical model for forming such zones is proposed. It takes into account that such a zone is composed of a set of independent particles. Hence the distribution of a substance around the source can be explained by movement of an individual particle. In the model this movement is a continuous semi-Markov process with terminal stopping at some random point in space. Parameters of the process depend on the velocity field of the flow. Forward and backward partial differential equations for the distribution density of a random stopping point of the process are derived. The forward equation is investigated for the centrally symmetric case. Solutions of the equation demonstrate either a maximum or a local minimum at the source location. In the latter case a concentric ring around the source is formed. If different substances vary in their absorption rates, they can form separable concentration zones as a family of concentric rings. 相似文献
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以映射和叠加原理为基础，探讨了均质、等厚承压含水层中地下水向完整井作三维运动时，地下水稳定运动基本微分方程的求解方法，并与裘布衣公式作了对比。由于求解时考虑了地下水流速的水平、垂直分量，故所得结果较裘布衣公式更为准确与合理。 相似文献
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An alternative method of solution for the linearized ‘theta‐based’ form of the Richards equation of unsaturated flow is developed in two spatial dimensions. The Laplace and Fourier transformations are employed to reduce the Richards equation to an ordinary differential equation in terms of a transformed moisture content and the transform variables, s and ξ. Separate analytic solutions to the transformed equation are developed for initial states which are either in equilibrium or dis‐equilibrium. The solutions are assembled into a finite layer formulation satisfying continuity of soil suction, thereby facilitating the analysis of horizontally stratified soil profiles. Solution techniques are outlined for various boundary conditions including prescribed constant moisture content, prescribed constant flux and flux as a function of moisture change. Example solutions are compared with linearized finite element solutions. The agreement is found to be good. An adaptation of the method for treating the quasilinearized Richards equation with variable diffusivity is also described. Comparisons of quasilinear solutions with some earlier semi‐analytical, finite element and finite difference results are also favourable. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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在研究节理的渗流时,渗流控制方程对节理渗流分析结果具有显著影响。首先介绍了节理渗流分析中的控制方程：Navier-Stokes方程、Stokes方程、Reynolds方程和立定定理,并分析了各控制方程在节理渗流分析中的适用性。以Reynolds方程作为渗流分析控制方程,建立了粗糙节理渗流空腔模型。然后以节理试件为研究对象,在实测节理三维表面形貌并计算隙宽分布后,分别进行相同渗流边界条件下的室内渗流试验和空腔模型计算,得到节理在不同接触状态下的渗流量实测值和计算值,并分别将计算结果与立方定理下的空腔模型、将整个节理简化为光滑平行板模型的立方定理以及速宝玉经验公式的计算结果进行比较,结果表明,Reynolds方程下的节理渗流空腔模型计算结果与实测值最为吻合,可以较为准确地反映节理的渗流情况。同时,根据Reynolds方程下空腔模型得到的渗流流量分布可以呈现节理渗流的曲折现象,为从本质上研究节理渗流特性奠定了理论基础。 相似文献
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A number of phenomena and processes in geosciences can be summarized by second order partial differential equations. The major numerical methods for their solution include the classical finite difference method and the finite element method newly developed in the last two or three decades. Since 1977 the author has proved that for the Laplace and Poisson equations, these two methods are identical and are different only in the process of formulation. For transient problems, such as heat conduction in the earth and the groundwater and oil-gas unsteady flow in porous media, there are some differences in resulting linear algebraic euqations. In general, two methods give similar results, but when the time step is decreased to some extent, the resulting algebraic equation will be consistent with the anti-heat conduction equation rather than the original heat conduction equation. This is the reason why unrealistic potentials are produced by the finite element method. Such a problem can be overcome by using the 相似文献
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Numerical identification of diffusion parameters in a nonlinear convection–diffusion equation is studied. This partial differential
equation arises as the saturation equation in the fractional flow formulation of the two-phase porous media flow equations.
The forward problem is discretized with the finite difference method, and the identification problem is formulated as a constrained
minimization problem. We utilize the augmented Lagrangian method and transform the minimization problem into a coupled system
of nonlinear algebraic equations, which is solved efficiently with the nonlinear conjugate gradient method. Numerical experiments
are presented and discussed.
This work was partially supported by the Research Council of Norway (NFR), under grant 128224/431. 相似文献
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This paper presents the development of a mathematical model for methane gas migration in coal seams. The major focus of this model is the coupling between the gas flow and deformation of solid coal. The effect of diffusion of adsorbed methane gas from the solid matrix to the voids has been taken into account. The adsorption of gas in the coal seam causes a two-phase state of gas flow. The governing equation for the two-phase gas flow is a non-linear partial differential equation with non-linear boundary conditions. A finite element model has been developed for simulation of the distribution of pressure and concentration of methane gas due to gas migration in coal seams. 相似文献