Journal of Hydroelectric Engineering

水力发电学报

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2015 Vol. 34, No. 10 Published: 2015-10-25

	1	From digital dam toward smart dam
		ZHONG Denghua, WANG Fei, WU Binping, CUI Bo, LIU Yuxi
		DOI: 10.11660/slfdxb.20151001
		This paper first reviews the advancements in dam construction and development in hydraulic engineering, and summarizes the conceptualization of digital dam and its related research achievements. Then, we present an interpretation of the difference between the two concepts of digital dam and smart dam, based on a brief discussion on several disadvantages of digital dam, including insufficient depth in intelligent analysis of massive data and relatively low fusing level of site monitoring, simulation analysis and intelligent control. Smart dam is a new concept that is based on the digital dam conceptualization but emphasizes a specific form of dam development, i.e. adoption of new-generation information technologies as a basic means, such as Internet of things, intellectual technology, cloud computing, and big data. This concept also means a specific intelligent system of dam management and operation that is dynamic, refined, and perceivable in analysis and control. Besides, a smart dam often has distinctive features such as integrity, interoperability, fusion-expansibility, autonomy, and robustness. Third, we describe a basic framework of smart dams in detail, including a real-time information perception module, an interconnected real-time transmission module, an intelligent real-time analysis module, and an intelligent real-time management decision system, focusing on analysis of the progress and superiority of smart dams over digital dams in independent information collection, smart reconstruction analysis, intelligent decision, and integrated visualization. Finally, we explore key directions of smart dam research in fundamental theory, key technology, and management and operation system.
		2015 Vol. 34 (10): 1-13 [Abstract] ( 701 ) PDF (681 KB) ( 2017 )

	14	Drying shrinkage characteristics of magnesium slag and fly ash composite concrete
		CUI Zizhi, LI Shanshan, ZHANG Cheng, CHEN Dongdong
		DOI: 10.11660/slfdxb.20151002
		Aiming at the low utilization rate of magnesium slag and high requirement of modern concrete for dimension stability, we have designed an orthogonal test scheme to experimentally study the drying shrinkage characteristics of composite concrete mixed with magnesium slag and fly ash. Results show that the shrinkage increases with time following a trend of hyperbolic curve with a high correlation. Either magnesium slag or fly ash has inhibitory effect on shrinkage deformation and the former's effect is stronger. This inhibitory effect is enhanced when fly ash is added into magnesium slag composite. The effect of magnesium slag on drying shrinkage builds up gradually with time and tends to be stable at roughly 90 d. Only shrinkage occurred and neither expansion nor expandable harm in concrete has been observed during the testing period. Thus, it is feasible to add a certain amount of magnesium slag to compensate the shrinkage of concrete.
		2015 Vol. 34 (10): 14-19 [Abstract] ( 204 ) PDF (317 KB) ( 377 )

	20	Study on crack resistance of roller compacted concrete with MgO contents
		XU An, ZENG Li, LIU Gang
		DOI: 10.11660/slfdxb.20151003
		The property of retarded micro-expansion of MgO hydration products can improve the crack resistance of roller compacted concrete (RCC). Both macro and micro approaches were combined in this work to study the mechanical properties and microscopic morphology of MgO RCC with different MgO contents. An anti-crack coefficient was introduced to evaluate the improvement of crack resistance. The test results show that the MgO additive increases RCC compactness through micro-expansion of Mg(OH)2 and produces an expansion stress that can neutralize the tensile stress caused by temperature drop, and thus it improves the crack resistance of RCC and its mechanical properties.
		2015 Vol. 34 (10): 20-26 [Abstract] ( 164 ) PDF (770 KB) ( 405 )

	27	Calculation of return periods and design values of bivariate floods based on Copula function
		SHI Lixiang，SONG Songbai
		DOI: 10.11660/slfdxb.20151004
		The traditional method of flood frequency analysis based on univariate distribution is unable to consider the dependence structure between flood characteristics. This paper focuses on the calculation of return periods and design values of bivariate floods using the theory of Kendall return period. We have applied this calculation method to flood analysis for the Zhaoshiyao and Suide stations of the Wudinghe basin in North Shaanxi, using a bivariate Frank Copula to describe the joint distribution of flood peak and flood volume. To find the most appropriate values of design floods, a component-wise excess method and maximum likelihood method are adopted on three definitions of the return period: joint return period, co-occurrence return period, and Kendall return period. The results indicate that the design values calculated using both methods have no considerable difference, and that the design values on these definitions are the largest, intermediate and the smallest respectively. An examination on the three definitions shows that the former two distinguish dangerous regions by variable values. Both have a certain fault, but they can be applied satisfactorily in some specific cases. The latter makes the distinguishment by joint probability, thus avoiding overestimation or underestimation of the dangerous regions. Therefore, Kendall return period is recommended in general cases.
		2015 Vol. 34 (10): 27-34 [Abstract] ( 256 ) PDF (387 KB) ( 724 )

	35	Parameter estimation in hydrologic frequency analysis using non-quantitative historical flood and Bayesian approach
		SHANG Xiaosan, WANG Dong
		DOI: 10.11660/slfdxb.20151005
		Consideration of historical flood could improve the accuracy and reliability of flood frequency analysis. In practice, however, some historical floods cannot be quantitated and are difficult to use in a common deterministic methods, thus lowering the reliability of parameter estimation and design flood in the flood frequency analysis. This paper focuses on the coupling of a Bayesian method a maximum likelihood estimator in the frequency analysis using non-quantitative historical floods. This coupling method and its application are demonstrated in a case study of synthetic and measured flood series. Compared to several traditional deterministic method, the coupling method not merely makes it possible to make use of non-quantitative historical floods, but can improve estimation accuracy.
		2015 Vol. 34 (10): 35-41 [Abstract] ( 162 ) PDF (405 KB) ( 343 )

	42	Study on Pickands bootstrap moment estimation of generalized Pareto distribution parameters of extreme precipitations
		ZHAO Ruixing, ZHAI Yumei
		DOI: 10.11660/slfdxb.20151006
		The generalized Pareto distribution (GPD) is a good probability distribution model to describe peak-over-threshold (POT) series, but the determination of its threshold is a great challenge in practical application. To solve this problem, we herein describe a Pickands bootstrap moment method for estimation of the GPD parameters. The method is used to estimate the shape parameter of GPD and the optimum number of POT and calculate the threshold, then the scale parameter is obtained with the moment estimation method. This new method is applied to the daily precipitation series of the Beijing meteorological station and its results are compared with those estimated by the linear moment estimation method using the same threshold. The comparison shows that it has a good ability of parameter estimation for GDP and generalized extreme value (GEV). From the fitting of the GDP quantiles and POT series, their correlation coefficients are up to 0.997 or more while their standard deviation and maximum deviation are the lowest. These results indicate that the Pickands bootstrap moment estimation method is obviously superior to the linear moment estimation.
		2015 Vol. 34 (10): 42-50 [Abstract] ( 275 ) PDF (445 KB) ( 483 )

	51	Search space reduction method and its application to hydroelectric operation of multi-reservoir systems
		MING Bo, HUANG Qiang, WANG Yimin, WEI Jie, TIAN Tian
		DOI: 10.11660/slfdxb.20151007
		Joint operation of multi-reservoir systems is one of the most effective measures for direct control of regional water resources and it significantly increases the social, economic and ecological benefits compared with single reservoir operation. This paper describes a search space reduction method (SSRM) for solving hydroelectric optimal operation models of multi-reservoir systems, using the minimum output of a hydro plant and its discharge constraints to reduce the search space and overcome the shortcomings of the meta-heuristics in lower search efficiency and instable results. SSRM, when coupled with the meta-heuristics, can produce a high-quality initial population, and its search process is limited to an optimal search space that is closer to the feasible search domain. Thus, such reduction makes it easier to find the globally-optimized solution. We have adopted an effective algorithm, namely the cuckoo search (CS), in the optimization, and compared the traditional and reduced search spaces for a multi-reservoir system with given historical monthly inflows. A case study shows that SSRM, a simple and effective method for practical use, improves convergence and solution accuracy of the meta-heuristics.
		2015 Vol. 34 (10): 51-59 [Abstract] ( 232 ) PDF (605 KB) ( 545 )

	60	Assessment of power-generating benefits from cascade reservoirs integrated operation —A case study of Wu River cascade reservoirs
		WU Wenhui, ZHANG Shuanghu, ZHANG Zhongbo, JIANG Yunzhong, ZHANG Rui
		DOI: 10.11660/slfdxb.20151008
		Along with the emergence of joint operation situations in a cascade reservoir system, the current assessment method of reservoir power generation is unable to meet the needs of economic operation, and the assessment of jointly-operated complex systems is more difficult. To overcome the limitations of traditional methods, this paper presents a method of potential optimization assessment that uses an optimal operation model to calculate the power output and its completion rate for cascade reservoirs, and considers model constraints by the main factors of power output. Combing this method with traditional assessment, we have achieved a comprehensive assessment of cascade reservoirs, i.e. assessing the existing situation and guiding the future operation. In a case study of the Wu River cascade system, its current comprehensive operation level is assessed by a traditional method and our new method. The results show that this system has excellent operation levels and the major factors of its power generation are runoff, runoff forecasting, and power network stability. The assessment results are comprehensive and objective and provide a technical support to the Wu River cascade in operation level improvement, water-saving, and power output growth in the future.
		2015 Vol. 34 (10): 60-69 [Abstract] ( 221 ) PDF (389 KB) ( 406 )

	70	Multicore parallel chaos simulated annealing differential evolution algorithm for long-term operation of cascaded hydropower stations
		LI Baojian, CHENG Chuntian, Wang Sen
		DOI: 10.11660/slfdxb.20151009
		The traditional differential evolution (DE) could fall into local optimum easily when used for global optimization. To overcome this disadvantage, we herein present a new algorithm, namely the multicore parallel chaos simulated annealing differential evolution (PCSADE), for solving the optimization models of long-term operation of cascaded hydropower stations. This algorithm takes advantages of the chaos theory and the simulated annealing algorithm (SA) to enhance the DE algorithm and the Fork/Join parallel framework for higher computation efficiency. Particularly, it can make full use of the chaos theory's merits in handling strong randomness and ergodicity and the good local search ability of the SA algorithm to enhance its global search ability, and apply the chaos theory to the generation of initial populations and the dynamical adjustment to the DE algorithm's control parameters. And it replaces the selection operation of DE algorithm by a metropolis rule of the SA algorithm. Moreover, it can adopt the Fork/Join parallel framework for parallel computation of a complex simulation task. Application to the 14 hydropower stations on the Hongshui River show that PCSADE can make full use of the multicore resources of computers and improve the solution and efficiency significantly. Thus, our new algorithm is an effective and feasible method for long-term operation of hydropower stations.
		2015 Vol. 34 (10): 70-79 [Abstract] ( 279 ) PDF (373 KB) ( 340 )

	80	Optimal operation of hydropower stations using social spider optimization algorithm and its performance analysis
		WANG Wenchuan, LEI Guanjun, QIU Lin, XU Dong mei, Liu Huimin
		DOI: 10.11660/slfdxb.20151010
		An optimal operation model for hydropower station is characterized by high-dimension, nonlinearity, multiple constraints, and difficult model solution. To surmount these problems, this paper presents a social spider optimization (SSO) algorithm to solve such models. This new algorithm searches the global optimum using the synergy mechanism of social spiders, so that it can avoid premature convergence and local-optimum trapping and obtain stable results for optimal decision on reservoir operation. Its performances in a case study are compared with those of the dynamic programming (DP) and genetic algorithm (GA). The comparison shows that with a smaller number of parameters, it is superior in calculations and more robust and efficient in optimum searching. Therefore, the social spider optimization algorithm is an effective method for practical optimization of hydropower station scheduling models.
		2015 Vol. 34 (10): 80-87 [Abstract] ( 319 ) PDF (387 KB) ( 466 )

	88	Experiment on hydraulic performance of short-throat flume with flat base for field flow measurements
		XIAO Yizhou, WANG Wene, HU Xiaotao, WANG Yingying
		DOI: 10.11660/slfdxb.20151011
		Flow measurement is a key technique of agricultural water management in irrigation areas. At present, various types of flow-measuring devices are available for open channels, but few of them are suitable for field use. Parshall flume has a high accuracy but with a complex structure and high cost. This paper presents a modified Parshall flume that has a flat base, simple structure, and lower cost. This new flume is 774 mm long with a throat of 51 mm wide, and it is easy to carry around and install in the field. Its application range of discharge is 6-20 L/s of a single flume and up to 36 L/s of double flumes. We have taken water level measurements at 11 cross sections under 16 different discharges and obtained by data fitting an empirical formula of discharge versus inflow water depth for the conditions of free outflow. Relative to the measurements, the error of this formula is -0.11% on an average and 7.06% in maximum. Analysis on the variations in Froude number and specific energy at different control sections along the flume under different discharges shows that the critical depth occurs at a cross section near the rear end of the throat, which indicates that the throat length is appropriate.
		2015 Vol. 34 (10): 88-95 [Abstract] ( 255 ) PDF (738 KB) ( 292 )

	96	Hydraulic study and optimization of the open channel of pumped storage plant intakes
		LIU Jijun, GAO Xueping
		DOI: 10.11660/slfdxb.20151012
		This paper presents an experimental and numerical study of the flows in the inlet channel of a pumped storage plant intake based on hydraulic model tests on the inlet and outlet of the plant. We have developed a three-dimensional model using the RNG k-ε turbulence model and VOF method to optimize the open channel shape of primary design and eliminate the harmful flow circulations observed in the inlet channel. The optimized scheme of final recommendation increases the lateral diffusion angle of this design's inlet channel and installs a sill at the downstream end of the short diversion section that is located upstream of the diffusion and takes a lower bed elevation. Experiment shows that this end sill can effectively adjust the flow into more homogeneous velocity profiles at the cross sections and improve flow patterns in the inlet channel remarkably, completely eliminating all the flow circulations.
		2015 Vol. 34 (10): 96-102 [Abstract] ( 231 ) PDF (1619 KB) ( 525 )

	103	Study and simulation on ice jam process in river bends for Inner Mongolia reach of the Yellow River
		LI Chao, LI Changyou, LI Hongfang
		DOI: 10.11660/slfdxb.20151013
		River bends are the locations that initiate ice jams, and their subsequent development and accumulation of the incoming ice cause a water level rise. Study on ice jam process in river bends and its formation mechanism is a key issue of river ice research. This paper presents the results of field observation on the Yellow in the 2013-2014 winters and examines the mechanism of ice jam formation in various channel bends. We have applied DynaRICE a two-dimensional river ice model to simulation of the ice transport and ice jamming processes in the Sanhuhekou bend. The results show three key factors of ice jam formation: upstream ice concentration, upstream and downstream flow conditions, and riverbed bathymetry. This study provides an insight into the possible locations of ice jam initiation and a technical support to further study in ice prevention.
		2015 Vol. 34 (10): 103-110 [Abstract] ( 223 ) PDF (1093 KB) ( 390 )

	111	Study on hydraulic characteristics of sidewall aerators in high-head large-discharge spillway tunnel
		ZHANG Hongwei, LIU Zhiping, ZHNAG Dong, WU Yihong
		DOI: 10.11660/slfdxb.20151014
		Hydraulic characteristics of sidewall aerators in high-head large-discharge spillway tunnel have been studied by adopting a model test approach in this work. We made an analysis on the factors of aeration effect and the causes of sidewall water-wings and obtained two shapes of water wing-free sidewall aerators. These new shapes have good air-entraining behaviors and an ability to inhibit the formation of water wings on the sidewall via controlling the length of side cavity. The results also show that generally sidewall aerators produce a certain effect on the air entrainment near the bottom, and thus the bottom aerator and side aerator should be optimized as a whole. Finally, a discussion is presented on design principles and optimization methods for sidewall aerator shapes, based on a comprehensive analysis on the hydraulic characteristics of sidewall aeration.
		2015 Vol. 34 (10): 111-116 [Abstract] ( 197 ) PDF (510 KB) ( 421 )

	117	Angle of repose and angle of surface friction of sediment particles. An overview
		MENG Zhen, YANG Wenjun
		DOI: 10.11660/slfdxb.20151015
		A clarification of several concepts is presented: the angle of repose, natural slope, surface friction angle, internal friction angle, and contact friction angle of sediment particles. This is based on a review of typical experimental methods for determining the angle of repose and its major influencing factors, along with the factors of the angle of surface friction. We present a discussion on the effects of sorting coefficient η, kurtosis coefficient K and skewness coefficient S on the angle of repose of non-uniform sediment, derive a relationship of the angle of surface friction versus the relative hidden degree of sediment particles from the concept of sediment incipient motion, and analyze the difference between the angle of repose for particles under the flows and the dynamic angle of repose. Finally, we suggest some ideas about the experimental tests and applications related to non-uniform sediment.
		2015 Vol. 34 (10): 117-129 [Abstract] ( 306 ) PDF (1099 KB) ( 702 )

	130	Numerical simulations and analysis on wake flows of axial-flow tidal current turbines
		CHEN Zhengshou, LIU Yu, ZHAO Chen, Ng Chang Han
		DOI: 10.11660/slfdxb.20151016
		3D numerical simulations of the wake flows behind axial-flow tidal current turbines have been carried out using a CFD software to study the interference between the wakes behind different impellers in different conditions of rotor installation, focusing on a single-rotor model without duct and a ducted dual-rotor model with a shaft spacing of 1.8D (where D is the blade diameter) for comparison. Results show that, the wake flow of single-rotor model was relatively stable with a velocity nearly the same as outside the wake, except for the lower velocity in a small wake region of less than 1D from the rotor. In the case of dual-rotor model, we observed a stronger interference between the two rotors, a lower velocity in the wakes, and a lower energy loss in the wakes than the single-rotor case. This leads to a considerable increasement in energy conversion ratio of the rotors. Physical model tests have been conducted and the measurements verified the main conclusions above and the effectiveness of our CFD method.
		2015 Vol. 34 (10): 130-137 [Abstract] ( 280 ) PDF (1103 KB) ( 534 )

	138	Internal flow behaviour analysis of Francis pump-turbine in S-curve region with small guide vane opening
		ZHU Wei, XIAO Yexiang, YAO Yangyang, LUO yongyao, ZENG Chongji, WANG Zhengwei
		DOI: 10.11660/slfdxb.20151017
		S-shaped curve is a widespread characteristic of pump-turbines, which has significant impact on unit operation. It is important to analyze underlying causes and control methods. This study has conducted numerical simulations of the whole passage of a model pump turbine and examined the characteristics of 3-D flow in the S-curve region for small guide vane opening, focusing on four different operating points to analyze the behaviour of internal flow in the unit. We found out that a large number of vortices appeared in the vane and runner sections at the points near runaway. The vaneless region between the guide vanes and runner was featured with an obvious water ring, where only a small amount of water was able to flow into the runner at the turbine braking point. In the reverse mode, the flow was very complicated. A comprehensive analysis of the 3-D flow reveals that in the S-curve region, a backflow in the vaneless region will block up all the channels if the unit operates in the condition of small discharge. This makes the runner unable to keep operating in the small discharge at a higher speed, and hence the S-shaped bend is created around the runaway point on the characteristic curve.
		2015 Vol. 34 (10): 138-144 [Abstract] ( 205 ) PDF (3136 KB) ( 419 )