A study for optimum utilization of the Damodar water resources

The study describes the existing and proposed water resources development in the Damodar river basin and the systems study carried out for estimating the consequences of implementing a proposed set of management and development measures. A simulation model was considered appropriate for the study and a computer program developed by theus Army Corps of Engineers was used. The results of various simulation runs are discussed. The analysis of results have indicated that an integrated operation of all reservoirs on the Damodar system, both existing and proposed, would help in maximization of utilisation and benefits. It is also concluded that a simulation model would help not only the long range planning but also the day-to-day operation.     

Optimizing water supply and hydropower reservoir operation rule curves: An imperialist competitive algorithm approach

Efficient reservoir management requires the implementation of generalized optimal operating policies that manage storage volumes and releases while optimizing a single objective or multiple objectives. Reservoir operating rules stipulate the actions that should be taken under the current state of the system. This study develops a set of piecewise linear operating rule curves for water supply and hydropower reservoirs, employing an imperialist competitive algorithm in a parameterization–simulation–optimization approach. The adaptive penalty method is used for constraint handling and proved to work efficiently in the proposed scheme. Its performance is tested deriving an operation rule for the Dez reservoir in Iran. The proposed modelling scheme converged to near-optimal solutions efficiently in the case examples. It was shown that the proposed optimum piecewise linear rule may perform quite well in reservoir operation optimization as the operating period extends from very short to fairly long periods.     

单相水流阶段煤层气井裂隙水运移的临界裂隙尺寸数学模型

查明煤层气井排采的单相水流阶段裂隙水运移的裂隙临界尺寸大小,能为煤层气井的压力传播研究提供理论依据。根据煤储层孔裂隙结构特征,构建了煤储层地质概念模型;基于弹塑性力学理论,构建了单相水流阶段煤储层裂隙中水运移的力学平衡方程;结合有效应力原理和损伤理论分析了裂隙周围的应力分配与损伤演化,建立了一种适用于不同储层条件的单相流阶段水运移的煤储层裂隙临界尺寸的数学模型。晋城寺河矿煤储层条件下的计算结果表明:原始状态下煤储层水运移的临界尺寸为0.1μm,所得结果与其他学者实验室测试结果基本相符。同时还得出:随着排采过程中水的产出,水运移的煤储层裂隙的临界尺寸有增大的趋势,但变化幅度较小,仍在0.1μm左右。所建模型能较准确预测不同条件下煤储层单相水流阶段水运移的煤储层裂隙临界尺寸及排采过程中临界尺寸的变化规律。     

Optimal scheduling of hydro-thermal power systems considering the flood risk of cascade reservoirs

The increased flood risk linked to global warming affects the safety of cascade reservoirs, with direct effects on the stable operation of power systems. In this article, an optimal scheduling framework for hydro-thermal power systems considering the flood risk of cascade reservoirs is presented. First, the extreme value theory-based peak over threshold model is adopted to build a generalized Pareto distribution of extreme flood inflow for a single reservoir. Then, the Copula function is used to build a joint probability distribution function of extreme inflow for cascade reservoirs during a flood period. Based on the superior performance of the conditional value at risk (CVaR) in characterizing the tail risk of the cascade reservoir spillway safety margin, a CVaR constraint for cascade reservoir flood prevention is proposed, and a scheduling model for hydro-thermal power systems considering the flood prevention risk of head-dependent cascade reservoirs is presented. Secondly, Rockafeller and Uryasey reformulation and sample average approximation are employed to transform the proposed model with a CVaR constraint into a convex solvable optimization model. Finally, a modified IEEE 14-node system is used to verify the better performance of the proposed model than that of the models with the chance constraint and with the independent normal distribution of extreme flood inflow. The impacts of flood prevention confidence level and Monte Carlo sample size on the optimal scheduling results are analysed quantitatively.     

蓄滞洪区洪水演进一、二维数值仿真及其在洼淀联合调度中的应用

为了实现蓄滞洪区内各洼淀实时洪水调度,考虑到蓄滞洪区内复杂河网与洼淀交错的情况,建立了河道、滞洪区联合计算的一、二维衔接洪水演进数学模型,在考虑铁路、公路、堤防及桥涵等阻水建筑物等复杂边界条件下,采用有限体积法进行离散和求解。结合蓄滞洪区实时洪水调度仿真系统的总体框架,建立了模拟洪水在蓄滞洪区内任意位置的水位、流速、淹没水深、历时等演进过程的一、二维洪水演进数值仿真系统。结合大清河实测资料对东淀滞洪区洪水演进进行了模型验证,结果基本吻合,并应用该系统对大清河滞洪区五洼联合调度方案进行了实时模拟,分析了洼淀联合调度下出现的倒淀现象,对不同方案进行了比较分析,实现了实时的洪水调度分析。     

大庆油田台肇地区低渗透储层裂缝及其开发对策研究

介绍了大庆油田外围典型的低渗透储层——台肇地区葡萄花油层中东西向、南北向、北西向和北东向4组高角度构造裂缝，其发育程度依次由强变弱。受现今地应力影响，近东西向裂缝连通性好，地下张开度和渗透率大，是该区主渗流方向；其次是北西向、北东向裂缝，近南北向裂缝渗透性较差，裂缝发育程度受岩性、层厚、断层、构造应力等因素影响。根据地质条件和油藏数值模拟，认为该区适应于用矩形井网和菱形井网开发，效果比反九点和五点井网好。低渗储层由于裂缝发育，降低了地层破裂压力，注入压力容易超过地层破裂压力，使注入水沿裂缝快速流动，引起水     

Transient thermal behavior of a water heater system driven by a heat pump

A dynamic model of a water heater system driven by a heat pump was designed to investigate transient thermal behavior of the system which was composed of a heat pump and a hot water circulation loop. Finite volume method was applied to describe the heat exchangers, and lumped parameter models were used to analyze the compressor and the hot water reservoir. Dynamic performances were evaluated as the hot water temperature changes for various sizes of the hot water reservoir. In order to compare the performance characteristics, time scale was normalized by the time constant determined from a quasi-steady state simulation of the system. From the simulation, the smaller size of the water reservoir was found to have larger transient performance degradation, and the larger size caused additional heat loss during the hot water storage period. Therefore, the reservoir size should be optimized in a design process to minimize both the heat loss and the performance degradation.     

Mixed integer simulation optimization for optimal hydraulic fracturing and production of shale gas fields

Optimal development of shale gas fields involves designing a most productive fracturing network for hydraulic stimulation processes and operating wells appropriately throughout the production time. A hydraulic fracturing network design—determining well placement, number of fracturing stages, and fracture lengths—is defined by specifying a set of integer ordered blocks to drill wells and create fractures in a discrete shale gas reservoir model. The well control variables such as bottom hole pressures or production rates for well operations are real valued. Shale gas development problems, therefore, can be mathematically formulated with mixed-integer optimization models. A shale gas reservoir simulator is used to evaluate the production performance for a hydraulic fracturing and well control plan. To find the optimal fracturing design and well operation is challenging because the problem is a mixed integer optimization problem and entails computationally expensive reservoir simulation. A dynamic simplex interpolation-based alternate subspace (DSIAS) search method is applied for mixed integer optimization problems associated with shale gas development projects. The optimization performance is demonstrated with the example case of the development of the Barnett Shale field. The optimization results of DSIAS are compared with those of a pattern search algorithm.     

Optimizing water tanks in water distribution systems by combining network reduction,mathematical optimization and hydraulic simulation

In the last two decades, water consumption in Germany has been decreasing, which causes the water tanks and pipes in water distribution systems to work inefficiently. This paper proposes a method that supports the planning process for tanks in water distribution systems. The method uses a combination of network reduction, mathematical optimization and hydraulic simulation. The mathematical optimization model is a non-convex Mixed Integer Quadratically Constrained Program (MIQCP) that is solved by a piecewise linearization. As this may lead to many binary variables and therefore high computing times, the size of the water distribution system model is reduced before building the optimization model. After applying several network reduction techniques and using a piecewise approximation of the original model, there may be some hydraulic differences between the original network model and the reduced network model. To make sure that the solution obtained in the optimization process is feasible in the original water distribution system model, the solution is verified by a hydraulic simulation. If the solution is not feasible, the reduced model has to be modified and solved again until the hydraulic simulation verifies a solution as feasible. In this paper, each of these processes is described and the results indicate the usefulness of each of them.     

Optimal design of distributed treatment systems for the effluents discharged to the rivers

This paper presents a methodology for the optimal synthesis of distributed treatment systems of effluents discharged into a main river to meet water discharge quality constraints. The methodology is based on a new superstructure that is formulated and solved as a multi-objective mixed-integer nonlinear programming model. A material flow analysis technique is used to track the pollutants through the watershed considering the combined effects of the inputs, outputs (i.e., agricultural, residential, industrial, and so on) and the chemical transformations. A disjunctive programming model is implemented for selecting the optimal location of the distributed treatment system. Prior to the optimization and based on the pollutants considered, a discretization approach is implemented to determine from simulation the removal efficiency and the unit cost of given configurations and operating conditions of the selected treatment units. Therefore, the optimization process determines the removal efficiency used to treat the effluents and the flow rate treated. Simultaneous minimization of the total annual cost of the distributed treatment system and the contaminant concentration of the discharge to the catchment of the watershed are considered as two objective functions. Three case studies (one in Mexico and two in Egypt) have been selected to illustrate the methodology. Results show that significant savings can be obtained when the distributed treatment system is implemented. Finally, the proposed methodology can be used for supporting governmental decisions (i.e., it provides the investment required for a specific water quality).     

Numerical analysis for electrokinetic soil processing enhanced by chemical conditioning of the electrode reservoirs

A numerical analysis was undertaken for enhanced electrokinetic soil processing. To perform chemical conditioning of the electrode reservoirs, the electrokinetic soil process employed a membrane as a barrier between the electrode reservoirs and the contaminated soil. An alkaline solution was purged in the anode reservoir that was bounded by the membrane. A mathematical model was used for demonstration of pH change and phenol removal from a kaolinite soil bed, the prediction of pH variations in both electrode reservoirs, and the determination of an optimized injection time of the anode-purging solution. The time-dependent dispersion coefficient was employed in consideration of the averaging effect of the velocity profile on a one-dimensional transport. The estimation of pH and phenol profiles in the soil bed reasonably agreed with the experimental data. The simulation revealed that the removal efficiency of phenol from the kaolinite soil could be improved by maintaining pH of the anode solution.     

Investigation of the propagation of pollutants in water reservoirs

A mathematical model for investigating the problem of the propagation of pollutants in water reservoirs on salvoed (instantaneous) discharge is suggested. To calculate dilution, a method developed on the basis of the equation of turbulent diffusion in cylindrical coordinates is suggested. The method allows one to determine the concentration of pollutants at an arbitrary distance from the place of their discharge. The conditions for the formation of local pollution zones in a water reservoir are considered.     

Improved operating policies for multipurpose use: A case study of Bhadra Reservoir

The operation of Bhadra reservoir project is studied using optimization (overyear and within year storage model) and simulation (with both historic and synthetically generated monthly streamflows) based on a 52-year record of monthly inflow data for irrigation and hydropower generation. Bed turbine operation is found to be the key issue in maximizing the total hydropower production. The reservoir operation is studied for thirteen different policies of bed turbine operation using simulation. These simulation runs are carried out for a specified irrigation demand with historic data. The probability distribution of the maximum possible hydropower production is arrived at by simulating the reservoir operation with 4 different sets of synthetically generated monthly streamflows, each having sequences of different lengths, for two promising policies. A comparison of results made with the actual operation over a 11-year period shows that substantial increase in the total hydropower generation is possible with the identified policies without undue deficits in meeting the specified irrigation demands.     

Earthquake‐induced hydrodynamic pressures on a 3D rigid dam–reservoir system using DRBEM and a radiation matrix

The dual reciprocity method is applied to determine the hydrodynamic pressure distribution in a three‐dimensional dam–reservoir system subjected to earthquake excitation. The reservoir domain is idealized as a finite region of irregular geometry adjacent to the dam followed by an infinite domain of uniform cross‐section in the upstream direction. The reservoir hydrodynamic pressure response is governed by the Helmholtz equation subject to free surface, dam–reservoir interface, absorbing bottom/banks and radiation boundary conditions. A three‐dimensional (3D) dual reciprocity model is developed to determine the hydrodynamic pressure in the finite reservoir domain. A radiation matrix is developed and introduced to relate the hydrodynamic pressure and its normal derivative on the interface between the finite and infinite domains. The three‐dimensional radiation model used is developed by applying a two‐dimensional dual reciprocity formulation along the interface of the finite and infinite reservoirs together with a continuum solution in the upstream direction of the infinite domain. The model is compared for the hydrodynamic response of a three‐dimensional rectangular reservoir and found to be in excellent agreement with results obtained from a model based on the analytical formulation existing in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

Extending the lifetime of the running electrolyte in capillary electrophoresis by using additional compartments for external electrolysis

The use of two additional reservoirs to accommodate the electrodes of the power source is proposed to improve the stability of the running electrolyte in capillary electrophoresis. The basic idea is to use salt bridges to connect those reservoirs to the ones containing the capillary ends. Although simple, there are several issues that can be considered in the design and implementation of such system in order to prevent undesired transference of material between the electrolysis and the main reservoirs. The use of a sealed electrolysis reservoir without a gas phase, the use of materials that ensure volume stability, and the use of bridges as long as possible are three basic directions. A compromise is involved in the dimensions of the sectional area of the bridge, because a small area diminishes the amount of a species transferred by diffusion but leads to an undesirable increase of the electrical field during the electrophoretic running. Thus, a bridge composed of a main wide-bore tube connected to a small-bore capillary seems to give the best performance for practical use. A simple electrolysis-separated system was adapted to a preexisting capillary electrophoresis system, and its performance was evaluated with a mixture of tartaric, malic, and succinic acids that was separated in sodium benzoate solution (pH 5.5) using the original equipment and the modified one. Due to the water electrolysis and the small buffering capacity of the electrolyte, there was a significant pH change and consequently changes in the effective mobilities of the analytes and loss of resolution after a few runs using the original equipment. Using the electrolysis-separated system, no significant change in the migration time and resolution was observed even after 15 runs. Besides the freedom to prepare running electrolytes with electroactive species or unbuffered solution, high throughput and the use of small reservoirs, such as the ones used in microfluidic devices, are the main advantages of the system.     

Partial constraint satisfaction approaches for optimal operation of a hydropower system

Optimal operation models for a hydropower system using partial constraint satisfaction (PCS) approaches are proposed and developed in this study. The models use mixed integer nonlinear programming (MINLP) formulations with binary variables. The models also integrate a turbine unit commitment formulation along with water quality constraints used for evaluation of reservoir downstream water quality impairment. New PCS-based models for hydropower optimization formulations are developed using binary and continuous evaluator functions to maximize the constraint satisfaction. The models are applied to a real-life hydropower reservoir system in Brazil. Genetic Algorithms (GAs) are used to solve the optimization formulations. Decision maker's preferences towards power production targets and water quality improvements are incorporated using partial satisfaction constraints to obtain compromise operating rules for a multi-objective reservoir operation problem dominated by conflicting goals of energy production, water quality and consumptive water uses.     

Numerical simulation study of shale gas reservoir with stress-dependent fracture conductivity using multiscale discrete fracture network model

The exploitation of shale gas has increasingly become the focus of worldwide energy industry. Due to the existence of natural/hydraulic fractures, most of the shale gas reservoirs exhibit high degree of heterogeneity and complexity which leads to the stress-dependent fracture conductivity of shale gas reservoir. Discrete fracture network (DFN) model is adopted in this research since the conventional continuum model cannot meet the numerical simulation requirements of fractured shale gas reservoir. A series of experiments about the fracture properties stress-dependent have been conducted on some shale core samples, the stress-dependent fracture conductivity correlation is selected and incorporated into the mathematical model to characterize the reduction of fracture conductivity potential with the reservoir pressure drop. The DFN model is applied to a shale gas reservoir with fracture network to study the effect of the stress-dependent fracture conductivity on the shale gas well performance. The results show that the effect of fracture conductivity reduction with pressure drop on the shale gas well performance depends on both the initial fracture conductivity and matrix permeability. The complex interactions between the fracture and matrix permeability should be considered when select the appropriate size of proppants for fracturing.     

Study of a complex water resources system with screening and simulation models

The study describes a sequential iterative modelling process for a complex water resource system. Two types of analytical models are used to find a reasonably small set of possible systems optimal design alternatives for a complex river basin. These models are a linear programming deterministic continuous (lpdc) model and a linear programing deterministic discontinous (lpdd) model. Linear programing has been used with linear approximation of the nonlinear functions. A simulation program has been developed which continues screening on the basis of the information obtained from the linear programing model. The models are developed in the context of analysis of the Narmada river, a large river basin in India, for which in the first instance alternative combinations and capacities of six major dams have to be decided.     

固相萃取-高效液相色谱法测定某水库型水源地微囊藻毒素

采用优化的固相萃取一高效液相色谱法对某水库型水源地微囊藻毒素污染进行了为期1年的监测,同时测定了相关的水质指标和藻类种群结构。结果表明：该水库在春末和夏、秋季检出了3种微囊藻毒索（MC—YR、MC—RR、MC—LR）,以MC—YR为主,夏季是藻毒素污染的高峰时段,其浓度与水库环境条件、藻类生物量有密切的关系。     

河网水动力及综合水质模型的研究

采用Preissmann 4点隐式差分格式离散一维圣维南方程组,应用三级联解法求解河网水动力数学模型。基于河道-节点-河道算法的河网水质模型的求解特点,在WASP的水质模型理论基础上,建立了河网非稳态水动力综合生态水质数学模型,考虑了多个污染物变量的耦合计算、变量之间的相互转化和迁移。利用模型对4个河网算例进行验证。验证表明,水位和流量过程计算值与实测值吻合很好,各水质变量的计算值和实测值也符合较好,可见模型是合理可靠的,为河网的水质预测和管理提供了一个较为简便实用的工具。