基于多重网格的地表水文与二维水动力动态双向耦合模型研究

针对流域洪涝模拟模型的计算精度、格式稳定性及计算效率等问题,本文提出基于多重网格技术的地表水文与二维水动力动态双向耦合模型(M-DBCM)。地表水文模型采用非线性水库法模拟降雨产流和径流;二维水动力模型采用浅水方程模拟洪水演进过程。采用不同分辨率的网格划分计算区域,在粗网格区域采用地表水文模型模拟降雨径流过程;在细网格区域采用二维水动力模型模拟洪涝积水区的水流运动。地表水文和二维水动力模型通过内部耦合移动界面(Coupling Moving Interface, CMI)实现无缝连接,保证通过CMI的水量和动量等通量守恒,提高模型的模拟精度。采用时间显式格式同时求解地表水文和水动力模型,在不同区域采用不同的计算时间步长,以提高模型的计算效率。通过典型案例验证本文构建的耦合模型的性能,结果表明本文提出的动态双向耦合模型能够在保证模拟精度的同时提高计算效率。     

流域洪水模拟

通过对流域水流运动规律的分析，将流域的水流概化为调蓄单元的零维模拟、河道水流的一维模拟、行洪区水流的二维模拟、联系的处理及无资料径流的处理，对各部分的特点，采用相应的数值方法，统一进行求解，即构成了流域洪水模型，最后以淮河中下游段为试验区，进行了洪水还原计算，结果令人满意。     

大宁河流域降雨径流模拟研究

大宁河是三峡的一级支流,径流可迅速汇入三峡水库,其降雨径流模拟需要在较短计算时间内达到足够精度。鉴于此,本文分别采用SWMM和TANK模型来模拟大宁河地表径流过程和地下径流过程。模拟结果表明,该方法能够达到较好的精度,且使地表径流过程的模拟参数具有一定的物理定义,其经验可为缺乏地下资料流域的产汇流模拟提供借鉴。     

新疆叶尔羌河中游河段水沙运动的数值模拟

采用有限元法离散二维模型方程建立了新疆叶尔羌河中游河段水沙运动的平面二维数学模型,对常微分方程系数矩阵运用质量集中原则近似处理,而后采用"预报一校正一迭代"的差分计算格式求解常微分方程组,该计算过程稳定性较好、效率较高.在动边界问题上.引入虚拟水深处理后,可以保证数值计算的连续性.用该模型对叶尔羌河中游河段的水沙运动进行数值模拟,并把计算结果同实测值进行了对比验证,结果吻合良好.     

基于非结构网格的二维溃坝洪水数值模型

基于三角形非结构网格,采用有限体积法建立了平面二维水动力学模型,用于模拟复杂边界和地形下溃坝洪水的运动过程。该文采用中心迎风格式求解界面数值通量,并通过引入限制器技术对界面两侧变量进行重构,使其在空间上具有两阶精度。采用局部改变河床高程方法对界面重构变量进行修正来提高模型的干湿处理能力。该模型既能保证数值格式的和谐性,又能够确保整个计算过程中水深是非负的。通过采用三个典型算例的验证和一个实例溃坝洪水过程的模拟分析,计算结果表明:该模型能很好地捕捉复杂地形和边界条件下洪水演进过程中的洪水锋面运动、干湿节点转化、水深和流量变化等过程,具有很强的稳定性、水量守恒性和激波捕捉能力,特别适用于具有复杂地形和阻水结构物的溃坝洪水演进案例分析。     

溃堤洪水分析的一、二维水动力耦合模型及应用

建立一、二维水动力耦合数学模型以模拟溃堤洪水的演进过程,其中一维模型采用Preissmann格式离散,二维模型利用基于非结构网格的Roe格式离散。将道路、灌渠等特殊边界概化为宽顶堰并作线性处理,利用非结构网格与特殊边界的耦联,建立具有真实地形的耦合模型,并采用干湿水深理论对模型进行优化。将模型应用于黄河青铜峡河西灌区溃堤洪水的模拟,较为真实地再现了洪水在计算区域内的演进过程与淹没范围,体现了道路、灌渠等特殊边界的阻水效果与桥涵的过水效果。     

基于矢量糙率的栅格单元流量分配模型

本文认为地表径流在汇流过程中由于流域坡面上地质层理走向、人类耕作活动、天然植被分布等一系列影响使坡面不同方向上具有不同的曼宁糙率系数取值,从而对栅格单元内地表径流向下游各栅格单元的流量分配产生影响,基于这一认识本文提出矢量糙率的概念,并在分析以往模型的基础上,利用一维圣维南运动波方程结合曼宁方程建立了考虑糙率因素的栅格单元间地表径流流向及流量分配模型.经试验流域应用检验,该模型能更精确地模拟降雨径流过程.     

集总式喀斯特水文模型构建及其应用

针对大部分喀斯特流域属于无资料地区的现状,构建资料要求较低的集总式喀斯特水文模型(lumped karst hydrological model,LKHM)。LKHM以三水源新安江模型为基础,针对喀斯特流域二元三维的流域性质,在汇流计算层做了改进。将岩溶地貌概化为3类:溶沟、溶隙、管道,采用滞后演算法模拟溶沟对地表径流的调蓄作用,采用若干线性水库串联模拟不同大小口径的溶隙对地下径流的调蓄作用,将所有管道概化为一个大管道模拟地表径流与地下径流的交换;最后在贵州平湖流域进行模型检验和应用。结果表明:LKHM模拟精度较高,说明模型的结构、参数合理,具备一定的实用价值。     

考虑水沙相互作用的河堤溃决二维数值模型

该文建立了洪水漫堤导致河堤溃决的平面二维水沙运动数值模型,以模拟溃口扩展和堤身冲刷的过程。该模型基于有限体积法、采用显式格式求解平面二维水流运动和非平衡全沙泥沙输移方程,并考虑了边坡崩塌、底床急剧变形以及高浓度泥沙输移对水流运动的影响。溃口处的混合流场采用HLL approxim ate Riemann solver处理,非黏性土溃口边坡的崩塌采用不同干、湿静止角处理。通过对英国HR Wallingford实验室一组实验的计算,结果表明该模型能较好地模拟非黏性土堤坝溃决过程中的溃口展宽、坝体冲刷、流场分布以及溃口流量过程线。对模型参数的敏感性分析显示了水沙耦合溃决模型的非线性特征。     

流域非闭合特性对岩溶地区水文过程模拟的影响

岩溶地区通常发育有大量岩溶裂隙、管道和洞穴,构成错综复杂的地下输水网络,形成了独特的流域水循环模式。地下岩溶构造的存在会造成地下分水岭与地表分水岭的不重合,流域趋于非闭合状态。为了弄清岩溶流域非闭合特性对水文过程模拟的影响,本文以桂林岩溶地区潮田河(漓江支流)流域为研究区域,采用三水源新安江模型模拟该地区多年降雨径流过程。通过比较几组给定流域面积的模拟结果,分析了流域计算面积选取对潮田河流域水文模拟结果精度的影响,并探讨了流域非闭合特性影响下该地区的水体流动模式。研究结果表明:模型率定时,当流域计算面积由340 km~2变化至460 km~2时,NSE先增大后减小,RE值持续增大,两者在380~390 km~2时可同时达到最优;结合不同时间尺度下径流模拟精度的分析结果,给出了合理的流域计算面积,比基于地表分水岭提取的流域面积约小8.9%~11.2%,故部分水量可能通过地下岩溶构造流向邻近流域。合理的流域计算面积对潮田河流域径流模拟精度提高显著,尤其是提升了枯季径流的模拟。     

A Solution for Flood Control in Urban Area: Using Street Block and Raft Foundation Space Operation Model

The overdevelopment of urban area has decreased the city’s ground permeability and increased its surface runoff. Moreover, the urban area existing flood control system meets the high risk and new challenge for water resource management due to global warming and climate change. A huge idle raft foundation space of existing buildings in urban area is found to be practicable solution for urban flood control systems. Through the operation model using street block and raft foundation space in urban area can effectively reduce peak runoff during typhoon seasons and extreme rainfall periods. This study selected a certain street block in Taipei City and 47 typical typhoons as validation, and constructed a Street Block-Raft Foundation flood control model (SB-RF model). Firstly, the optimal solution for reducing peak runoff for the 47 typhoons was obtained using Linear Programming. Data from the optimal solution and Back Propagation Neural Network were then used to simulate the SB-RF model flood control. This paper not only demonstrates the effectiveness of proposed model in controlling urban floods, but establishes an expected average peak runoff reduction rate and proposes a methodology for optimizing flow controls. Results are proved to be useful as reference for urban flood control for urban area such as Taipei City during typhoon season.     

A COUPLED MORPHODYNAMIC MODEL FOR APPLICATIONS INVOLVING WETTING AND DRYING

This work presents a new finite volume Godunov-type model for predicting morphological changes under the rapidly varying flood conditions with wetting and drying.The model solves the coupled shallow water and Exner equations,with the interface fluxes evaluated by an Harten-Lax-van Leer-Contact(HLLC) approximate Riemann solver.Well-balanced solution is achieved using the surface gradient method and wetting and drying are handled by a non-negative reconstruction approach.The new model is validated against several theoretical benchmark tests and promising results are obtained.     

The Impacts of Climate Variability and Future Climate Change in the Nile Basin on Water Resources in Egypt

This paper describes the application of hydrologic models of the Blue Nile and Lake Victoria sub-basins to assess the magnitude of potential impacts of climate change on Main Nile discharge. The models are calibrated to simulate historical observed runoff and then driven with the temperature and precipitation changes from three general circulation model (GCM) climate scenarios. The differences in the resulting magnitude and direction of changes in runoff highlight the inter-model differences in future climate change scenarios. A 'wet' case, 'dry' case and composite case produced +15 (+12), -9 (-9) and + 1(+7) per cent changes in mean annual Blue Nile (Lake Victoria) runoff for 2025, respectively. These figures are used to estimate changes in the availability of Nile water in Egypt by making assumptions about the runoff response in the other Nile sub-basins and the continued use of the Nile Waters Agreement. Comparison of these availability scenarios with demand projections for Egypt show a slight surplus of water in 2025 with and without climate change. If, however, water demand for desert reclamation is taken into account then water deficits occur for the present-day situation and also 2025 with ('dry' case GCM only) and without climate change. A revision of Egypt's allocation of Nile water based on the recent low-flow decade-mean flows of the Nile (1981-90) shows that during this period Egypt's water use actually exceeded availability. The magnitude of 'natural' fluctuations in discharge therefore has very important consequences for water resource management regardless of future climate change.     

潮流数值模拟中动边界处理方法研究

论文提出了一种新的干湿判断方法来处理潮流数值模拟中潮间带上的动边界问题。文中的干湿判断方法主要是通过显式求解所得的“预估水深”和流速方向确定单元边的干湿状态。干湿判断过程中不仅考虑到水位对干湿状态的影响，而且包含了流速、流向和风应力等因素；判断过程不必分成“干”判断和“湿”判断两步进行。对三个测试算例进行了干湿判断模拟，模拟结果显示：干湿判断方法无明显的数值振荡，模拟结果的水面光滑；可以较准确的估计浅水处水体的蓄留能力，能保证干单元的水深均小于门限水深且为有限的正值；可以较准确的模拟潮间带上的动边界问题。     

区域雨水资源化潜力计算及时空分布规律研究

为充分利用雨水资源应对区域水资源紧缺问题,以黑龙江省松嫩平原为研究区,考虑地下水补给量和基流量对雨水资源化潜力的影响,引入分布式水文模型SWAT,提出了适用于研究区的雨水资源化潜力计算模型,计算了研究区的雨水资源化潜力,分析了研究区雨水资源化潜力时空分布规律。结果表明:研究区雨水资源化潜力在时间和空间上均存在一定差异,各分区之间以及同一分区不同年份雨水资源化潜力及其构成也存在较大的差异;生育期多年平均可利用雨水资源化潜力为343.78亿m~3,占生育期多年平均雨水总量的50.28%;各分区产流量在雨水资源化潜力中占比均较大,建议要注重提高降水径流汇集、径流蓄存和集雨补灌等相关技术;在土壤水增量占比大的分区要注重节水灌溉技术的应用。总体来看,黑龙江省松嫩平原地区雨水资源化潜力巨大,应该科学合理提高雨水资源利用率,保障区域农业可持续发展。     

Numerical simulation of shallow-water flooding using a two-dimensional finite volume model

A 2-D Finite Volume Model (FVM) is developed for shallow water flows over a complex topography with wetting and drying processes. The numerical fluxes are computed using the Harten, Lax, and van Leer (HLL) approximate Riemann solver. Second-order accuracy is achieved by employing the MUSCL reconstruction method with a slope limiter in space and an explicit two-stage Runge-Kutta method for time integration. A simple and efficient method is introduced to deal with the wetting and drying processes without any correction of the numerical flux term or the source term. In this new method, a switch of alternative schemes is used to compute the water depths at the cell interface to obtain the numerical flux. The model is verified against benchmark tests with analytical solutions and laboratory experimental data. The numerical results show that the model can simulate different types of flood waves from the ideal flood wave to cases over complex terrains. The satisfactory performance indicates an extensive application prospect of the present model in view of its simplicity and effectiveness.     

浅水动边界的干底Riemann解模拟

浅水动边界(干湿边界)问题具有广阔的工程应用背景,准确模拟动边界条件下的间断流动,并保证水量守恒是动边界计算的最大困难.论文针对有限体积法,应用能模拟间断流的干底准确Riemann解求解干、湿单元界面的数值通量.模型在动边界条件下静水、溃坝波和水面自由振荡等算例检验的基础上,应用到实际水库的溃坝波模拟.结果表明该方法能准确模拟动边界条件下的间断流动,具有稳定性好、精度高、水量守恒等优点.     

Numerical simulation of the internal wave propagation in continuously densitystratified ocean

A numerical model is proposed to simulate the internal wave propagation in a continuously density-stratified ocean, and in the model, the momentum equations are derived from the Euler equations on the basis of the Boussinesq approximation. The governing equations, including the continuity equation and the momentum equations, are discretized with the finite volume method. The advection terms are treated with the total variation diminishing （TVD） scheme, and the SIMPLE algorithm is employed to solve the discretized governing equations. After the modeling test, the suitable TVD scheme is selected. The SIMPLE algorithm is modified to simplify the calculation process, and it is easily made to adapt to the TVD scheme. The Sommerfeld＇s radiation condition combined with a sponge layer is adopted at the outflow boundary. In the water flume with a constant water depth, the numerical results are compared to the analytical solutions with a good agreement. The numerical simulations are carried out for a wave flume with a submerged dike, and the model results are analyzed in detail. The results show that the present numerical model can effectively simulate the propagation of the internal wave.     

Numerical Analysis of Surface Runoff for the Liudaogou Drainage Basin in the North Loess Plateau,China

The aim of this study is to realize a distribution hydrological model to calculate the rainfall-runoff process precisely for the development of the ravine in the north Loess Plateau. On the basis of the real investigation result to the vertical profile of soil in the Liudaogou drainage basin, which is located in the ravine of wind-water erosion crisscross region in the northern Loess Plateau, a vertical profile model for soil in the study area was set up, and a distribution-type hydrological model was developed by combining GIS with kinematic wave theory. This model was subsequently applied in the experimental drainage basin. The numerical simulation results show that the calculation of the rainfall-runoff process has relatively high precision (error less than 3 %). The model was used to calculate the rainfall-runoff process for 5 years (2005–2009) in the experimental drainage basin to deduce the yearly surface runoff volume and the annual runoff coefficient. The calculated average runoff coefficient for 2005–2009 is 0.11, and the average 5 year precipitation (437 mm) is almost equal to the yearly average precipitation, indicating that the annual runoff coefficient of the experimental drainage basin is approximately 0.10 to 0.15. The study provides a practical numerical method for estimating surface water resources for the wind-water erosion crisscross region of the northern Loess Plateau.     

地表水地下水的交互作用与耦合模拟

 传统的概念性水文模型存在不能对不同径流成分进行精确模拟和划分的局限性。而分布式水文模型基于其精确的物理基础和产流机制,充分考虑到不同径流成分的水力联系,在对流域进行土壤垂直分层和水平网格划分后可进行地表水、地下水的交互作用分析与耦合模拟。应用李兰教授开发的LL Ⅱ分布式水文模型和GIS技术,以宜昌黄柏河天福庙水库作为典型流域,根据连续日入库径流资料验证模型精度,对该流域的日入库径流过程进行地表水和地下水的连续耦合模拟与预测,取得了较好的模拟预测效果。