Simulation–Optimization Modeling: A Survey and Potential Application in Reservoir Systems Operation

This paper presents a survey of simulation and optimization modeling approaches used in reservoir systems operation problems. Optimization methods have been proved of much importance when used with simulation modeling and the two approaches when combined give the best results. The main objective of this review article is to discuss simulation, optimization and combined simulation–optimization modeling approach and to provide an overview of their applications reported in literature. In addition to classical optimization techniques, application and scope of computational intelligence techniques, such as, evolutionary computations, fuzzy set theory and artificial neural networks, in reservoir system operation studies are reviewed. Conclusions and suggestive remarks based on this survey are outlined, which could be helpful for future research and for system managers to decide appropriate methodology for application to their systems.     

Correction to: How Does the Coupling of Real‑World Policies with Optimization Models Expand the Practicality of Solutions in Reservoir Operation Problems?

Water Resources Management -     

Optimal Design and Operation of a Hydropower Reservoir Plant Using a WEAP-Based Simulation–Optimization Approach

Water Resources Management - Optimal design and operation of a hydropower reservoir is a complex optimization problem in terms of formulation and solution. In this study, a...     

Multi-Objective Hydraulic Optimization of Diversion Dam’s Cut-Off

The seepage flow beneath a hydraulic structure is formed by the hydraulic head difference between the upstream and downstream sides. Cut-off walls are often applied, as an expedience, to reduce the seepage flow through the foundation of diversion dams and to enhance the efficiency of these dams. In this research, perhaps for the first time, a novel methodology is propounded to assess the optimum characteristics of cut-off walls in diversion dams in order to ameliorate hydraulic interactions between the diversion dam foundation and the cut-off walls behavior, also their construction cost is minimized. The results are used to train and validate the Multi-Layer Perceptron (MLP) simulation model. Then MLP, as a meta-model for simulation of the hydraulic behavior of cut-off walls, is coupled with a robust multi-objective optimization algorithm, Non-dominated Sorting Genetic Algorithm-ΙΙ (NSGA-ΙΙ), to create a trade-off between the intended goals. Finally, Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE) decision making model and Nash-Harsanyi bargaining model are utilized to find the compromise design optimal solution on the trade-off curve. Results demonstrate that the best agreed-upon design optimal solution using PROMETHEE and Nash-Harsanyi bargaining models can be considered as (10, 3.84, 32) meters and (2.47, 10, 29.22) meters for optimum depth of the upstream and downstream cut-off walls and the optimum distance between them, respectively.     

Updating of Feed Pumps for 150 – 1200-MW Power Units at the Kaluga Turbine Plant

Suggestions concerning updating of main feed pumps of Russian thermal power plants are considered. Causes of pump failure are analyzed and recommendations are given for improving their operating characteristics. The updating of PN 1500-350-1 pumps at the Kaluga Turbine Plant (replacement of eight-channel guide vanes by twelve-channel whole-milled ones, use of 'cellular' seals, additional hydrostatic bearing unit in the middle stage of the rotor, and process measures) has substantially improved the vibration characteristics and increased the reliability. The pump of the 800-MW generating unit of the Perm Regional Hydro Power Plant has run for 5000 h. Recommendations are given for further improvement of the characteristics and the reliability. It is shown that the condensate-feed system can be simplified and made more reliable by realizing a circuit without booster and using preliminary startup of an axial-vortex stage in the feed pump. The updating performed by the KTP is flexible and adaptable to financial possibilities of customers.     

A numerical analysis of the influence of the cavitator’s deflection angle on flow features for a free moving supercavitated vehicle

When a high-speed cavitated weapon moves under water, the flow properties are important issues for the sake of the trajectory predication and control. In this paper, a single-fluid multiphase flow method coupled with a natural cavitation model is proposed to numerically simulate the flee moving phase of an underwater supercavitated vehicle under the action of the external thrust. The influence of the cavitator＇s deflection angle ranging from -3~ to 3~ on the cavity pattern, the hydrodynamics and the underwater trajectory is investigated. Based on computational results, several conclusions are qualitatively drawn by an analysis. The deflection angle has very little effect on the cavity pattern. When the deflection angle increases, the variation curves of the vertical linear velocity, the lift coefficient and the pitching moment coefficient become flatter. In the phase of the second natural cavitation, at a same time, the greater the deflection angle is, the lower the drag and the lift coefficients will be and the higher the pitching moment coefficient becomes. At the finishing time of the free moving phase, when the deflection angle lies in the small range of -1~ - 1~, the position of the center of mass and the pitching angle of the vehicle are more close to each other. However, when the deflection angle is less than -1° or greater than 1°, the position of the center of mass and the pitching angle change greatly. Ifa proper deflection angle of the cavitator is adopted, the underwater vehicle can navigate in a pseudo-fixed depth.     

A Study on the Large-scale System Decomposition—Coordination Method Used in Optimal Operation of a Hydroelectric System

Abstract

The optimal operation problem of multiple hydroelectric reservoir systems is very complex because of the large dimensions. Large-scale system decomposition-coordination methods, which can simplify complex problems into several interrelated sub-problems to avoid the “curse of dimensionality” and to obtain the global optimum on the global through coordination among sub-systems, is particularly well suited for optimizing large-scale, multi-reservoir systems. Applying this kind of theory and method, this paper studies and analyzes the problems of optimal operation of multiple hydroelectric reservoir systems in series, and sets up the optimal operation model of hydroelectric reservoir systems in series. On this basis, a practical example of two hydroelectric reservoirs in series on the upper reaches of the Yellow River in China is calculated and analyzed and the results are satisfactory. It is believed that applying this model can cut down the dimensions of the problem notably and that the theory and method are effective for real time operation.     

An Improved “Dynamic Control Operation Module” for Cascade Reservoirs

Reservoirs are one of the most efficient projects for water resources management, and also play an important role in flood control and conservation. Dynamic control of the reservoir flood limited water level (FLWL) is considered as an effective factor to ensure safety of the flood control during the flood season. The maximum allowed water level of cascade reservoirs is also a fundamental key element for implementing reservoir water level dynamic control operation. In this paper, we discussed and improved “Dynamic Control Operation Module for Cascade Reservoirs” (DCOMR). Therefore, a set of new formulas and new methodologies were proposed (NDCOMR) which considers intermediate variables forecast information, the release of the upstream reservoir and interval flow forecast information in effective lead times, which is applied to the dynamic operation of the maximum allowed water level of cascade reservoirs. The Bikou and Miaojiaba cascade reservoirs were selected as a case study. Based on numerical experiment results, the maximum allowed water level of cascade reservoirs at current time determined by NDCOMR was much safer than that determined by DCOMR. The NDCOMR is more rational and safer than DCOMR for flood control, without the need of reducing flood control standard.     

A Probabilistic Multiperiod Simulation–Optimization Approach for Dynamic Coastal Aquifer Management

Combined simulation–optimization (CSO) schemes are common in the literature to solve different groundwater management problems, and CSO is particularly well-established in the coastal aquifer management literature. However, with a few exceptions, nearly all previous studies have employed the CSO approach to derive static groundwater management plans that remain unchanged during the entire management period, consequently overlooking the possible positive impacts of dynamic strategies. Dynamic strategies involve division of the planning time interval into several subintervals or periods, and adoption of revised decisions during each period based on the most recent knowledge of the groundwater system and its associated uncertainties. Problem structuring and computational challenges seem to be the main factors preventing the widespread implementation of dynamic strategies in groundwater applications. The objective of this study is to address these challenges by introducing a novel probabilistic Multiperiod CSO approach for dynamic groundwater management. This includes reformulation of the groundwater management problem so that it can be adapted to the multiperiod CSO approach, and subsequent employment of polynomial chaos expansion-based stochastic dynamic programming to obtain optimal dynamic strategies. The proposed approach is employed to provide sustainable solutions for a coastal aquifer storage and recovery facility in Oman, considering the effect of natural recharge uncertainty. It is revealed that the proposed dynamic approach results in an improved performance by taking advantage of system variations, allowing for increased groundwater abstraction, injection and hence monetary benefit compared to the commonly used static optimization approach.

     

Citizens’ Perceptions on Water Conservation Policies and the Role of Social Capital

Planning and implementing environmental policies for the sustainable management of water resources is a challenging task. In order to improve the effectiveness of these policies it is essential to explore their social implications. The present article aims to investigate environmental policies focusing on domestic water conservation and their interconnection with social capital elements. In particular, by means of an empirical study conducted in an insular community of Greece, citizens’ perceptions are explored concerning the restrictions imposed from different environmental policy instruments for water consumption and their perceived level of effectiveness. Furthermore, the influence of social capital parameters on these perceptions is investigated. Aggregated indicators of social capital are estimated with Confirmatory Factor Analysis measuring social and institutional trust, participation in social networks and compliance with social norms. Through the results of ordinal regression models it is evident that significant connections exist between elements of social capital and perceptions of citizens towards water consumption policies.     

Presentation at the Closing Ceremony of TCDC Training Workshop on SHP for Asia-Pacific

Our memorable training workshop is going to an end now. It is my pleasure to send a remark on this grand closing ceremony. First of all, I＇d like to express my warm congratulations to the full success of the workshop which has been achieved under joint effort of HRC staff and all of you the distinguished participants. Now, I would like to talk about 5 points in the followings ：     

Decomposition-ANN Methods for Long-Term Discharge Prediction Based on Fisher’s Ordered Clustering with MESA

Water Resources Management - Precise and reliable long-term streamflow prediction contributes to water resources planning and management. Artificial neural network (ANN) have shown its remarkable...     

Test and Analysis on Soil Characteristics for the South Main Dyke of Jingjiang River

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Optimal Design of Barrage Profile on Anisotropic Soil Using Multi‐Objective Optimization Approach

Weirs and barrages are costly hydraulic diversion structures; therefore, any attempt to improve their design is a worthy contribution. Diversion structures, such as weir or barrage, may be designed on permeable formations considering homogenous soil properties. But in reality, soil properties are hardly homogeneous. In this paper, an approach is described to determine an economically efficient barrage profile by considering soil’s anisotropic behaviour. Hydraulic conductivity is considered to be an anisotropic soil property. An optimization-based methodology is developed to obtain the optimal barrage profile. The minimization of the material cost and minimization of the exit gradient is considered for multi-objective formulation. The multi-objective formulation is solved using NSGA-II, and a Pareto optimal front is obtained for different degrees of anisotropy. The flow interaction under a diversion structure in anisotropic soil is incorporated using the Modified Lane theory and is embedded in optimization formulation. The developed methodology is illustrated with a barrage profile as a hydraulic structure. A parametric study is carried out to study the effects of varying barrage design elements on the barrage’s optimum material cost.