赞比西河梯级水库的设计与管理——MCM2017 A题评论

<正>1 A题的背景与问题形成赞比西河是南部非洲第一大河,该河流经高原地区,穿越一系列峡谷地段,形成许多瀑布、急流,蕴藏着丰富的水能资源,总水能资源约达1 300亿kW·h。赞比西河上的卡里巴水坝是非洲较大的水坝之一,南非风险管理研究所在2015年的报告中指出:卡里巴大坝急需维护。由于赞比西河沿岸国家经     

基于WSD算法的水资源调度综合策略

为更好地解决水资源短缺的问题,逐层深入构建了预测模型、量化模型和调度决策模型。首先,利用改进的灰色预测方法分别建立可用水资源储量预测模型和水资源需求预测模型,结合实际情况,得到水资源调度、去盐碱化技术等单位成本的量化方法;然后,利用新提出的WSD算法以及AHP方法,从经济、环境以及自然3方面进行综合分析,建立了适应各地区实际情况的可持续发展水战略;最后,基于提出的模型和算法进行仿真,得出了一套解决2025年中国各地区水资源短缺问题的可行的水资源调度方案。     

多水库水资源系统的随机动态运行模型

具有多个水库的水资源系统是一种随机动态系统。研究这种系统的运行管理的目的是要确定一年内各时段中最优运行的策略。在建立优化运行模型时要解决两个问题。一是对于作为系统输入的天然迳流序列和作为系统约束的用水序列的处理方法；二是应用多维动态规划法推求优化运行模型的方法。     

减轻水库破坏深度的多目标调度模型与方法

本文根据出力均匀化的原则建立多目标优化模型求解出调度方案 ,并结合水库实例计算 ,指导水库实际的调度以减轻水库破坏程度 .     

基于最优出力分配的梯级总出力调度图优化

为提高梯级水库调度管理的科学水平和水资源利用效率,分析了蓄供水判别式法运用于梯级水库调度所存在的三点不足,以梯级调度期总发电量最大为目标,构建了基于梯级总出力调度图优化和时段内最优出力分配的双层嵌套模型,并给出了基于逐步收索方式和逐步优化算法的模型求解流程。以我国西南某流域梯级水库为实例进行计算,其结果与常规方案相比,不仅年发电量有所提高,保证出力和保证率也有较大程度的提升,验证了所建模型的合理性。     

主导权异质性视角下的过坝方式货运量分担率研究

翻坝公路与通航建筑物两类过坝方式的主导权,分别由货主和通航管理局所主导。针对货物过坝主导方的异质性,首先建立了各过坝方式的效用函数来分析主导权的转移机制。然后据此结合通航建筑物过坝原则,构建了货运量分担率多目标优化模型。最后以三峡工程为例,探讨了翻坝运输费率和船舶过坝顺序对分担率的影响,进而探讨了缓解大坝通航拥堵的决策机制。结果表明:提高翻坝公路的货运分担,可以有效改善船舶及货物的过坝运输状况;相比翻坝运输费率,降低装卸费率能更有效地提高翻坝公路货运分担水平;船舶过坝存在一个次序区间,使得水运货物经由通航建筑物过坝和经由翻坝公路过坝的效用相同。     

调水工程线路方案优选的灰色系统模型及其应用

调水工程为解决区域间水资源分布不均衡问题提供了一种有效途径 .调水工程线路方案的优选问题涉及社会、经济、环境、技术等多方面的因素 ,是一个复杂的多目标决策问题 .本文建立了其评价指标体系 ,应用 AHP法和信息熵方法相结合确定评价指标权重 ,建立了调水工程线路方案优选的灰色系统评价模型 .算例显示方法的有效性 .     

碾压混凝土坝渗流场与应力场耦合模型研究

针对碾压混凝土坝存在众多施工层面问题,提出了确定影响层厚度以及相应物理力学参数的方法;在此基础上,探讨并建立了碾压混凝土坝渗流场与应力场两场耦合模型,研制了相应的三维有限元程序．研究表明,结合试验和理论分析确定的碾压混凝土坝层面影响层的厚度、弹性模量和泊松比等参数更切合实际;提出的碾压混凝土坝渗流场与应力场两场耦合模型,能较好地体现两场耦合作用,开发的三维有限元模型能较充分反映碾压混凝土坝施工层面的特性．通过研究,为分析施工层面对碾压混凝土坝变化性态影响,以及了解大坝的应力和渗流的相互作用提供了科学依据．     

多星联合鲁棒性调度模型研究

在多星联合调度过程中,存在着很多不确定性因素,其中云层覆盖变化是主要的不确定性来源.本文针对考虑云层覆盖变化的多星联合调度问题,借鉴了连续函数的鲁棒性优化思想,提出了一种基于邻域的鲁棒性指标.在此基础上,建立了多星联合鲁棒性调度模型,给出了观测任务优先级的计算方法.实例研究表明,本文建立的模型能够在保证调度方案性能的基础上,获得鲁棒性强的调度方案.     

基于系统动力学模型的青岛市水资源承载力研究

在全面分析青岛市水资源现状的基础上,利用系统动力学方法建立了青岛市水资源承载力仿真模型,并对模型的有效性进行了检验.通过改变模型相关决策参数,仿真模拟了自然延续型、经济发展型、节水发展型、综合发展型4种不同方案下青岛市2011-2030年水资源承载力的动态变化情况.结果 表明,综合发展型方案是保证青岛市水资源可持续利用...     

Vegetation response to 30 years hydropower cascade exploitation in upper stream of Yellow River

The accumulated response of vegetation successive dam constructions and operations is an important concern, but the systematic assessment of impacts induced by cascade hydropower exploitation over long periods are seriously lacking. Using remote sensing data, the variations in grassland, the principal land cover in the upper catchment of the Yellow River, were investigated for eight dams constructed during the period 1977–2006. Two different scales—watershed scale and on-site area—were used to compare the changes in grassland and water area. Correlation coefficients from regression analyses showed that grassland area had more significant interactions with hydropower exploitation indicators in on-site scale than in watershed scale. The hydropower exploitation indicators had a more complex correlation with water area in watershed scale than in on-site scale. Consequently, observations of grassland area responses to successive hydropower exploitations were focused on the on-site region. The Normalized Difference Vegetation Index (NDVI) and the standardized NDVI, which can be used to analyze inter-annual climatic differences, were applied to identify the most heavily influenced vegetation zones. For different hydrological and micro-climatic conditions, the vegetation zones around reservoirs and along the main stream of Yellow River were analyzed, respectively. Two NDVI spatial principles at varied distances from the water demonstrated that the vegetation NDVI was recovering from 1994 to 2006. For distance of less than 10 km from water, the vegetation around reservoirs was better as the higher NDVI in 2006 than in 1977. The inter-annual NDVI comparison demonstrated that the critically affected vegetation zone was concentrated at distances of 0.1–0.4 and 1–6 km from the water. In on-site region, the grassland was further analyzed with elevation and aspect information, which indicated that grassland in sunny aspects was much disturbed. Detailed information about grassland response with water distance and the degradation characteristics provide the comprehensive assessment by cascade hydropower exploitation.     

Modelling the impact of dam failure scenarios on flood inundation using SPH

Flooding resulting from collapse of a dam is a highly destructive event. It is important to accurately predict the flow behaviour so that potential mitigation strategies can be investigated for disaster management planning. The meshless SPH method has previously been able to model this class of extreme flow events. In this paper, we extend the method to include modelling of dam wall fragments. Collisions between dam wall fragments, between fragments and terrain and full two-way coupling between fragments and the free surface water flow is included. This gives a method that can specifically investigate the impact of the dam wall failure scenario on the subsequent inundation. The historical St. Francis dam failure is used to demonstrate the impact of including the dam fragments. It also provides a means of quantitatively investigating their effect in terms of arrival time and water height at a downstream power station. The scenario with multiple independently timed failures of different parts of the wall (which closely matches the historical failure) gives excellent agreement with the observed data and gives the best match of all failure scenarios. Traditionally such modelling is performed by solving the two dimensional shallow water equations which is not able to capture the three dimensional nature of the flow in earlier stages of dam flooding. We specifically investigate the three dimensional nature of flow structures and formation of multiple downstream hydraulic jumps. These strongly influence water height and therefore control the extent of flooding of tributary valleys.     

Optimal stormwater management with two dams: the dynamics of the pump–to–fill policy†

We consider the management of water in two connected dams. Stormwater generated by rainfall flows into a large capture dam and is subsequently pumped to a smaller supply dam. Recently it was shown that the twin objectives of minimizing overflow and maximizing the amount of demand met are both achieved by the pump-to-fill policy, in which as much water as possible is pumped each day from the capture dam to the supply dam without allowing the supply dam to overflow. We present a simplifying reparameterization for this case and study the dynamics of the system.     

Barrier lake formation due to landslide impacting a river: A numerical study using a double layer-averaged two-phase flow model

A granular landslide impacting a river may lead to the formation of a landslide dam blocking the streamflow, and subsequently create a barrier lake. Should a barrier lake outburst, the flood may be destructive and spell disastrous consequences downstream. The last decade or so has witnessed a number of experimental and numerical investigations on barrier lake outburst flooding, whilst studies on barrier lake formation remain rare – a physically enhanced and practically viable mathematical model is still missing. Generally, barrier lake formation is characterized by multi-physical, interactive processes between water flow, multi-sized sediment transport and morphological evolution. Here, a new double layer-averaged two-phase flow model is proposed, which is an advance on existing continuum models that involve a single-phase flow assumption and presume a single sediment size, and discrete models that preclude fine grains and assume narrow grain size distributions. The proposed model is first validated against data from previous laboratory experiments of waves due to landslides impacting reservoirs and landslide dam formation over dry valleys. Then it is applied to explore the complicated mechanism and threshold for barrier lake formation. The water and grain velocities are shown to be disparate, characterizing the primary role of grains in driving water movement during subaqueous landslide motion and also demonstrating the need for a two-phase flow approach. The grain size effects are revealed, i.e., coarse grains and grain-size uniformity favour barrier lake formation. A new threshold condition is proposed for barrier lake formation, integrating the landslide-to-river momentum ratio and grain size effects. The present work facilitates a promising modelling framework for solving barrier lake formation, thereby underpinning the assessment of flood hazards due to barrier lakes.     

Nonlinear finite element reliability analysis of Concrete-Faced Rockfill (CFR) dams under static effects

The response of concrete slab on Concrete-Faced Rockfill (CFR) dams is very important. This study investigates the reliability of the concrete slab on a CFR dam by the improved Rackwitz–Fiessler method under static loads. For this purpose, ANSYS finite element analysis software and FERUM reliability analysis program are combined with direct coupled method and response surface method. Reliability index and probability of failure of the concrete are computed in the all critical points of the concrete slab by dam height. This study is also expanded for the reliability of CFR dams including different concrete slab thickness. In addition to the linear behavior, geometrically and materially non-linear responses of the dam are considered in the finite element analysis which is performed with reliability analysis. The Drucker–Prager method and the multi linear kinematic hardening method are, respectively, used for concrete slab and for rockfill and foundation rock. Finite element model used in the analyses includes dam–reservoir–foundation interaction. Reservoir water is modeled by the Lagrangian approach. Welded and friction contact based on the Coulomb’s friction law are considered in the joints of the dam. One-dimensional two noded contact elements are used to define friction. The self-weight of the dam and the hydrostatic pressure of the reservoir water are considered in the numerical solutions. According to this study, hydrostatic pressure, nonlinear response of the rockfill and the decrease in the concrete slab thickness reduce the reliability of the concrete slab of the CFR dam. Besides, the CFR dam models including friction are safer than the models including welded contact in the joints.     

Periodic behaviour for the evolutionary dam problem and related free boundary problems Evolutionary dam problem

The time dependent dam problem describing the seepage of a compressible or incompressible fluid in a porous dam is studied. We prove existence of solutions in a suitable weak sense, and uniqueness for rectangular dams. Existence or periodic solutions is established and questions ofstability and periodic behavior for large time are studied.     

Effect of channel connection on flow and salinity distribution of Danshuei River estuary

Numerical models are often used to evaluate the potential impact of human alteration of natural water bodies and to help the design the alternation to mitigate its impacts. A vertical (laterally integrated) two-dimensional hydrodynamic model was expanded to include the capability of simulating river loops as well as tributaries. The model was performed and applied to the Danshuei River estuarine system in northern Taiwan which consists of three major tributaries: the Tahan Stream, Hsintien Stream, Keelung River, and one river loop under the Chung-Hsin Bridge. The expanded model was reverified with observational field data of 2000. The verified model was then used to hindcast the river hydrodynamic conditions with a loop connection between the Danshuei River and Keelung River, which existed prior to 1965. It was found that the configuration of river loop connection has significant impacts on the residual transport along the connecting channel and the salinities in the connected river branches. The results show that the model may provide an ideal tool for management decision.     

Dam break flow computation based on an efficient flux vector splitting

Dam break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. In this paper, a 2D finite volume multiblock flow solver, able to deal with natural topography variation, is presented in detail. The model is based on an efficient Flux Vector Splitting method developed by the authors. A number of validation examples are comprehensively described.     

On a filtration problem through a porous medium

Summary We prove the existence of a unique solution for a free boundary problem relative to the stationary flow between two water reservoirs of different levels separated by a dam of a non-homogeneous porous medium. Entrata in Redazione il 5 maggio 1973.     

The fluid flow through porous media. Regularity of the free surface

The fluid flow through an earth dam separating two water reservoirs of different levels gives rise to a free boundary problem. In [1] we have proved the existence of a solution to this problem. In this paper we show that the free boundary is regular.