Journal of Hydroelectric Engineering

水力发电学报

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2015 Vol. 34, No. 9 Published: 2015-09-25

	1	Real-time load-adjusting method of cascade hydropower plants considering hydrological regime-changing conditions
		ZHOU Jianzhong, YUAN Liu, LU Peng, QIAO Qi, MO Li, WANG Chao
		DOI: 10.11660/slfdxb.20150901
		The changing of runoff in the river basin or upstream or the inaccuracy of inflow forecasts may result in a mismatch between the hydropower generation based on actual inflow and the planned load of the grid based on deterministic inflow forecasts. In such circumstances, if the hydropower plants still follow their original plan in operation, they will be likely to violate water level constraint or bring about a mass of surplus water. To solve these problems, a real-time load-adjusting method of cascade hydropower plants considering inflow-changing conditions is presented herein. Under inflow increasing, this method can guide the plants to generate more electricity by reducing surplus water release and be able to adjust thermal power output to absorb the spare hydroelectric power; under inflow decreasing, it can reasonably redistribute the load among plants considering the effect of energy storage in the cascade reservoirs and redeploy the thermal power to offset the deficit in hydropower generation by the grid load demands. Its feasibility and effectiveness was demonstrated in a case study of a hydroplant cascade on the Central China Power Grid, including the plants at Sanbanxi, Baishi, Tuokou and Wuqiangxi. The results show that our new method can effectively reduce the adverse impact of hydrological regime changing on the dispatches for upcoming periods. And the method can work out a plan adjustment that meets the requirements of hydropower plant operation and ensures the safety and stability of power grids.
		2015 Vol. 34 (9): 1-9 [Abstract] ( 254 ) PDF (691 KB) ( 372 )

	10	Influence of high and low precipitations and underlying surface changes on runoff in the Luan River mainstream
		FU Jun, FENG Ping
		DOI: 10.11660/slfdxb.20150902
		On the basis of monthly precipitation and runoff observations in the upper reaches of the Luan River basin over the period of 1961-2011, rainfall-runoff regression relationships have been studied by dividing this study period into three smaller periods (1961-1983, 1984-1999 and 2000-2011). For each period, two rainfall-runoff multivariate regression models have been developed for high and low flow periods, respectively, using a rainfall-runoff double mass plot method and the two-sample Kolmogorov-Smirnov test. All of the regression models for the three periods have passed the significance tests, with the average runoff residuals being less than 15% and determination coefficients greater than 68%. Based on these regression models, we have quantitatively analyzed the impact of changes in both precipitation and underlying surface on the runoff in the control catchment of the Sandaohezi hydrological station. The results reveal that under the condition of underlying surface over 1961-1983, the precipitation during 1984-1999 and 2000-2011 can generate 8.08% more and 25.34% less runoff than 1961-1983 respectively; under the rainfall condition of 1961-1983, the change in underlying surface over 1984-1999 and 2000-2011 can generate 19.4% and 43.16% less runoff than 1961-1983 respectively. This would affect the inflow discharge of the Panjiakou reservoir to some extent.
		2015 Vol. 34 (9): 10-19 [Abstract] ( 273 ) PDF (442 KB) ( 325 )

	20	POME with constraints of moments and its application to hydrological stochastic simulations
		LIU Dengfeng, WANG Dong, WANG Yuankun
		DOI: 10.11660/slfdxb.20150903
		The principle of maximum entropy (POME), a non-parametric inference technique with complete mathematical framework, has been increasingly applied in water resources. POME is substantially an optimization problem and the probability density function (PDF) is derived with forms of constraints. However, previous studies have focused little attention on constraints that are in form of moments, subjectively specifying the order of moments, which may have limitations in determining optimal POME distributions. The main contribution of this study is to present a POME framework considering the optimal order of moments, with analyses of the convergence of different moments with common distributions and a theoretical-empirical approach determining the optimal order of moments. This technique has been applied with hydrological data collected from the Yangtze River and the Yellow River. The series simulated with the technique is analyzed by comparison with measured series. Results indicate a good performance with all the measured statistics falling within the boxplot.
		2015 Vol. 34 (9): 20-28 [Abstract] ( 168 ) PDF (769 KB) ( 381 )

	29	Evaluation of water resources utilization efficiency in China under gradient development
		CHEN Wu, XU Xinyi, WANG Hongrui, CUI Shengyu
		DOI: 10.11660/slfdxb.20150904
		Water resources utilization efficiency is one of the key issues in water resources study. This paper presents the development of an evaluation model of water resources utilization efficiency using a method of improved rank correlation analysis. This model uses an evaluation index system constructed specifically for China, consistency test for selecting index ranks suggested by experts to eliminate the orders that fail the test and the idea of circular revision, to unify the index ranks of importance. It determines the relative importance of two adjacent indexes according to the ratios of their standard deviations. The model has been applied to the efficiency evaluations for 31 provincial administrative districts of China. The results indicate that the utilization efficiency is lower in the western regions and higher in the eastern regions. We have used the Moran’s I index to examine the global and local spatial distributions of the utilization efficiency in China under gradient development. This reveals that the utilization efficiency has strong spatial dependence and most of the districts are characterized by a HH, or LL, type. Thus, we conclude that China’s existing water resources utilization efficiency is featured with obvious gradient development, and suggest that systematic policies and measures should be taken to reduce the regional differences.
		2015 Vol. 34 (9): 29-38 [Abstract] ( 191 ) PDF (471 KB) ( 269 )

	39	Optimal water dispatching model for urban landscape and its application
		KANG Mengxin,TIAN Yimei, SI Yanjie
		DOI: 10.11660/slfdxb.20150905
		An optimal water dispatching model for landscape water quantity and quality has been developed and applied to Tianjin Coastal New Area, as a case study, to meet the demand on maintain urban landscape water quantity and quality and achieve high economical efficiency of water operation and maintenance. The present study shows that this model is able to minimize the daily cost of urban landscape water operation and maintenance under the condition of reasonable operation parameters such as the volume of water replenishment and the periods of replenishment and circulation. The results are helpful to optimization decision on the technical schemes of urban landscape water treatment, water quality management, and water operation and maintenance.
		2015 Vol. 34 (9): 39-45 [Abstract] ( 201 ) PDF (332 KB) ( 326 )

	46	Eulerian-Lagrangian simulations of suspended sediment deposition in open channels
		XIAO Baiqing, LI Ran, RONG Guiwen
		DOI: 10.11660/slfdxb.20150906
		A mathematical model for suspended sediment deposition has been developed based on an Eulerian-Lagrangian approach to explore the trajectories of suspended sediment particles in open channels. This model adopts a standard k-ε turbulence model for calculation of the turbulent flows and it calculates sediment particle tracks using a Lagrangian method and considering various forces on the particles, including: the effective gravitational force, drag force, virtual mass force and Saffman lift force. Compared with the traditional diffusion model and two-fluid model, the new model avoids the limitation on inflow sediment conditions that must be specified by measured sediment concentration distributions. Its prediction accuracy and reliability have been verified using a classical experiment of suspended load transport with net deposition, including a comparison between the predicted longitudinal variations of sediment concentration and measured ones. A non-monotonic vertical profile of sediment concentration that observed from the experiment has been also predicted with a good accuracy.
		2015 Vol. 34 (9): 46-51 [Abstract] ( 211 ) PDF (337 KB) ( 473 )

	52	Study on mechanism of riverbank collapse caused by subsoil erosion
		YAO Zhixiong, ZHOU Jian, WU Bo
		DOI: 10.11660/slfdxb.20150907
		Seepage erosion has been a major cause of riverbank failure in the geology conditions of sandy and clay soils forming double and multilayer structures. Riverbank collapse caused by seepage erosion is an interaction of water and soil with a complex failure mechanism. A correct understanding of the influence factors is of great significance to engineering management. This paper focuses on analysis and comparison of two major failure modes, i.e. shearing failure and overturning failure, using the theory of seepage failure and wedge stability method and considering the process of actual bank failure. Results show that the erosion development and stability of embankment depend on four key factors: water level variation, embankment height, sand permeability, and the tilt angle of sand layer. Water filling into the cracks on the bank backside greatly enhances bank instability. Due to the progressive feature of erosion development, the bank collapse caused by an abrupt water level drawdown is always delayed.
		2015 Vol. 34 (9): 52-58 [Abstract] ( 247 ) PDF (528 KB) ( 302 )

	59	Analysis of bankfull discharge at reach scale in the lower Wei River
		HE Li, YAN Yunxia, YAN Ming
		DOI: 10.11660/slfdxb.20150908
		As an important parameter, the bankfull discharge is morphologically significant in the study of river morphology, sediment motion, flood dynamics and their ecological impacts. Previous researchers have pointed out that the determination of bankfull discharge is more relevant at river reach scale than at a local scale. Based on the geometry data obtained from the lower Wei River, in this paper we analyze the variation of bankfull discharge at reach scale (QBFR) in fluvial process. To identify the bankfull elevation of each cross section, we adopted a method of Wolman (WOL) that is based on the surveyed cross-sections and geometric criterion. The method of convergence was used to calculate QBFR. The analysis result indicates that the QBFR of this river reach is well correlated with its inflow discharge and sediment conditions. Besides, according to the length of convergence that depends on the fluvial processes, field observations of QBFR should be extended in order to improve its identification.
		2015 Vol. 34 (9): 59-63 [Abstract] ( 235 ) PDF (439 KB) ( 315 )

	64	Experimental study of runoff velocity and sediment yield affected by gravels of engineering deposits in loess area
		LI Jianming1，WANG Wenlong，LI Hongwei，HUANG Pengfei，GUO Mingming，DONG Yukun，LI Yanfu
		DOI: 10.11660/slfdxb.20150909
		Erosion processes on engineering deposits of construction projects are different from those in farmland and fallow land due to their loose accumulation, coarse texture, complex composition, and steep slope. For this reason, such erosion is often considered typical of artificially-accelerated types. We have developed physical models for the deposited bodies with different slopes and different gravel contents based on field surveys on a large number of engineering deposits, focusing on the impacts of gravel content on runoff velocity and sediment yield in the condition of simulated rainfall. Results show that 1) flow velocity increases rapidly in the initial 3 min rainfall and then tends to be relatively stable. At slopes less than 25°, flow velocity on the slope of a deposited body that contains gravels is lower than that on a pure soil slope because gravels enhance the curvature of flow path and hence reduce flow velocity. A power function can fit well the relation of average stable velocity versus rainfall intensity and gravel content, while a binary linear relation fits better for slopes greater than 25°. 2) Sediment-yielding rate shows a decreasing volatility in the initial 12 min runoff and then tends to be stabilized, with its initial value 1.7 ~ 3.1 times greater than the stable stage. In each rainfall test, a peak of sediment yield was observed after 3 min runoff. An increase in rainfall intensity from 1.0 to 1.5 mm/min leads to an increase of 82.7% ~ 117.3% in the average yielding rate. There exists a threshold slope of about 25° that maximizes the yielding rate up to a peak 1.3 ~ 1.7 times those at other slopes. At the initial and stable stages, the yielding rate on pure soil slope was 0.6% ~ 28.7% greater than gravels-containing slope. 3) Average sediment yielding rate shows significant correlation with flow velocity in the entire erosion process including the initial and stable stages. The amount of erosion increases by 74.0% ~ 95.9% as rainfall intensity increases by 50%, and the erosion on pure soil slope is always greater than the corresponding gravels-containing slope erosion. Generally, the erosion in the initial 12 min runoff contributes 38.3% ~ 50.7% to the total erosion in the entire process. Thus, to control soil and water loss from the engineering deposits, a particular emphasis should be laid on those conservation measures that are effective at the initial stage of rainfall or runoff.
		2015 Vol. 34 (9): 64-74 [Abstract] ( 232 ) PDF (414 KB) ( 300 )

	75	Study on some key problems of river closure in mountainous regions
		XI Hao
		DOI: 10.11660/slfdxb.20150910
		River closure is not merely a key link in the construction of hydropower projects, but a control item that influences the entire construction progress. Along with the expansion of China’s hydropower development to the west, an increasing number of mountain river diversion and closure projects will be built. Based on a hydropower station project and using diversion and closure hydraulics along with model test data, this paper focuses on several key issues: immediate blocking and proceeding for protection of closure gap bottom and its effect, the effect of flow-deflecting secondary dyke on enhancement of the tunnel diversion ratio, the effect of rock pit at the diversion tunnel inlet on the diversion ratio, and whether or not to make further advance of the downstream cofferdam. Our research findings can solve these common problems in mountain river closure, thus ensuring a process of safe and reliable closure and remarkable economical benefits. This study would provide reference and guidance for closure design and construction of similar projects.
		2015 Vol. 34 (9): 75-84 [Abstract] ( 192 ) PDF (581 KB) ( 363 )

	85	Study of real-time detection of bedload transport rate using image recognition technology
		SUN Dongpo, GAO Ang, LIU Mingxiao, WANG Pengtao, MA Tengfei, ZHAO Yafei
		DOI: 10.11660/slfdxb.20150911
		In this paper, we describe a new approach to real-time detection of bedload transport rate using image recognition technology, based on the characteristics of bedload transport. This method can be used to determine the particle composition of bedload and its transport rate of each compositional component, and thus the dynamic transport rate, which is difficult to measure by the traditional methods, can be directly measured in real-time. The flume experiment indicates that the method of bedload transport rate measurement based on image recognition has good reliability. Application to real-time dynamic detection shows that the transport of fine particles is stable with continuous variation while the transport of coarse particles is characterized by obvious intermittency. The non-contact detecting method presented herein can achieve dynamic monitoring on the transport process of non-uniform bedload, real-time tracking of the particle composition and each component's transport rate, and tracking of the strip transport rate. It can also lower the ill conditions of curve fitting in calculation of transport rate. Thus, the method would enrich bedload measurement and help the study of non-uniform bedload transport.
		2015 Vol. 34 (9): 85-91 [Abstract] ( 224 ) PDF (540 KB) ( 364 )

	92	Pump failure water hammer propagation formula considering friction in long-distance water supply system
		ZHANG Jian, LI Dongzhou, JIE Shaopeng, YI Pengfei
		DOI: 10.11660/slfdxb.20150912
		Transient pressure distribution along a pipeline is important to water hammer protection for a long-distance water supply system. Once pump failure occurs the pressure behind the pump drops quickly after pump failure, and a long pipeline will be involved. Using the method of characteristics (MOC) and theoretical analysis, this paper analyzes the propagation of water hammer along the pipeline, and derives a formula for transient pressure decrease along the pipeline. The results show a good agreement of this formula with MOC calculation, and indicate that the pressure drop is diminishing along the pipeline if its wall friction is considered. The formula that takes an explicit form, is more convenient in the design of water hammer protection schemes.
		2015 Vol. 34 (9): 92-97 [Abstract] ( 291 ) PDF (385 KB) ( 343 )

	98	Extension correction method for dynamic characteristics of large and medium-sized irrigation pumps
		MAO Jiansheng, ZHANG Rengong, WANG Wanliang, CHENG Xialei
		DOI: 10.11660/slfdxb.20150913
		Some large and medium-sized irrigation water pumps in China have run for a long time, and their existing dynamic characteristics are significantly different from the design conditions. To obtain more accurate dynamic characteristics of these pumps, first we obtained the raw data of dynamic characteristics from the raw material of pump source, design data, and efficiency curve of the motor, etc. Second, the dynamic characteristics were corrected using a static correction method of exponential decay and a dynamic training method of the extension neural network in combination with the measurements of pump sets in practical operation. Finally, we developed a large and medium-sized irrigation pumps dynamic characteristics analysis code V3.0 that integrates the two methods into a single module. Practical application shows that the modified equation of pump power characteristics that is used in this code, can describe the real engineering conditions. And typical characteristic curves produced by the code have a reasonable spacing and follow the same trend without intersecting. The data fitting errors of the code are low and the actual results of the code applications are satisfactory. This study would lay a basis for further study on the optimization of joint operation of the pumps and the gates.
		2015 Vol. 34 (9): 98-106 [Abstract] ( 180 ) PDF (749 KB) ( 232 )

	106	Analysis on impact of guide bearing system on characteristics of hydro turbine shaft system
		PENG Yuerong, LAI Xide, ZHANG Weibin, GOU Qiuqin, TANG Jian
		DOI: 10.11660/slfdxb.20150914
		Characteristics of guide bearing are fundamental factors of the vibration characteristics and stability of turbine generator shafts. The properties of guide bearing depend on its geometric parameters and boundary conditions. This paper examines and analyzes the vibration behaviors of a turbine unit shaft to study the influence of different geometric parameters and boundary conditions of the bearing on the characteristics of the shaft, by using the method of single variable parameters and changing the number of bearing tiles, tile clearance, tile angle, and oil film temperature. We obtained the influence trend of guide bearing on the shaft system characteristics via an analysis of the shaft behaviors in terms of critical speed and logarithmic decrement rate. Results show that with the increase in the number of bearing tiles and tile angle or the decrease in oil film temperature, bearing eccentricity gradually decreases and minimum oil film thickness increases gradually, while with the increase in radius clearance, both bearing eccentricity and oil film thickness are increased. Also with the changes in the geometric parameters of the shaft, the first-order critical speed and the logarithmic decrement rate change little, but the second-order critical speed presents a different trend.
		2015 Vol. 34 (9): 106-113 [Abstract] ( 157 ) PDF (584 KB) ( 525 )

	114	Structure design of composite-material turbine blade by method of laminated element
		LI Fang, WANG Dazheng
		DOI: 10.11660/slfdxb.20150915
		Turbine blade of composite material is one of the key components of a tidal stream turbine, and the choice of its structural form is particularly important to blade safety. This paper presents a finite element model that generates regular laminated elements in a top-down procedure to simulate the blades of composite material. This method insures the elements consistent in their local coordinate systems and subsequently leads to consistent principle directions of the composite material of a blade. To implement the model, a set of APDL commands are coded on the basis of ANSYS software. We calculated the strength and stiffness of blade to confirm the thickness of blade layer, the number of layers, and the ply stacking direction of fibers. The model analysis of blade can be applied to blade resonance checking. The results indicate that our approach is effective and applicable and provides a reference for structure design of composite-material blade.
		2015 Vol. 34 (9): 114-118 [Abstract] ( 175 ) PDF (337 KB) ( 386 )

	119	Effects of water body on dynamic characteristics and seismic responses of run-of-river hydropower house
		SUN Wei, HE Yunlong, Miao Jun, YU Huqi, LI Wei, XIONG Kun
		DOI: 10.11660/slfdxb.20150916
		A complete plant structure-foundation-water body coupling FEM model have been developed to study the effects of water bodies in the flow passages and reservoir on the dynamic characteristics and seismic responses of a run-of-river hydropower house. This model adopts potential-flow fluid elements to simulate these water bodies, and a viscous-spring boundary for considering the radiation damping of the foundation. The results show that the water bodies have a significant effect on the vibration frequencies and seismic responses of the powerhouse and that neglecting the effects of water body may be unfavorable to the structural design of powerhouse. Simulation errors could be produced by simplification in those methods that simulate the water body in the reservoir only, such as the added mass model or potential fluid model, because the water bodies in the flow passages have a significant effect. Thus, the effect of water bodies in the flow passages must be considered for more accurate simulations.
		2015 Vol. 34 (9): 119-127 [Abstract] ( 278 ) PDF (1045 KB) ( 361 )

	128	Significance of aseismic design of hydro-generator units in southwest China

		DOI: 10.11660/slfdxb.20150917
		Earthquakes often cause a great impact on or even do harm to buildings, equipment, and facilities. It is necessary to strengthen the detection and analysis of earthquake impacts on the operation safety of hydro-generator units. This paper focuses on the earthquakes of intensity above M5.0 that occurred in southwest China in recent years and describes their impacts on the operation safety through monitoring and analyzing the stability parameters of large hydro-generator units owned by China Three Gorges Corporation. Meanwhile, by the finite element analysis results of the electromechanical equipment at modern hydropower stations, we conclude that operation safety of hydro-generator units that have adopted aseismic design will not be affected when suffering from earthquakes below the basic seismic intensity.
		2015 Vol. 34 (9): 128-137 [Abstract] ( 261 ) PDF (1492 KB) ( 267 )

	138	Analysis of soil arching in high core-wall rockfill dam
		GAO Ang, SU Huaizhi, LIU Chungao
		DOI: 10.11660/slfdxb.20150918
		Soil arching effect of core wall could reduce its vertical stress and induce horizontal fractures, resulting in hydraulic fracturing that threatens dam safety, and this is particularly significant in high core-wall rockfill dams. This study has focused on a 300 m high-grade core-wall rockfill dam. We herein analyze the stress in the dam body and its settlement trend using FEM simulations and monitored data, then discuss the effects of dam materials on the core wall and the locations with severe soil arching effect. Finally, we evaluate the possibility of hydraulic fracturing caused by soil arching and describe how the stress transfer in core wall varies vertically with elevation. Results show that the largest settlement of core wall calculated by FEM is slightly smaller than the monitored value, and no tensile stress in the dam was observed. On the base of core wall the arching effect is obvious in the downstream, while above the base it can be obviously observed only near the dam axis but not strong enough to cause hydraulic fracturing. Generally, the arching effect is greatly influenced by the elastic modulus ratio of core wall over dam shell and the Poisson's ratio of core wall. Above elevation 780 m, the soil arching effect is quite severe, causing a greater reduction in top-down stress transfer.
		2015 Vol. 34 (9): 138-145 [Abstract] ( 270 ) PDF (435 KB) ( 417 )

	146	Compaction quality evaluation of rockfill dam based on compaction and material parameters
		WANG Rui, ZHONG Denghua, WU Binping, YUE Pan
		DOI: 10.11660/slfdxb.20150919
		Compaction quality depends on compaction parameters (rolling speed, vibration status, rolling passes, and compacted thickness) and material parameters (moisture content, uniformity coefficient, and curvature coefficient). Real-time compaction parameters at any location can be obtained using real-time quality monitoring technology of rockfill dam construction. The material parameters, however, are uncertain and difficult to be monitored in real-time, which results in an uncertainty in compaction quality evaluation. Based on the pit sampling data, this paper establishes a nonlinear mapping relationship between input (compaction parameters and material parameters) and output (dry density). Therefore, the dry density at any location of the entire rolled working unit can be fitted using real-time compaction parameters and material parameters (generated by improved Bootstrap method) as input. Results show that dry density, when fitted with compaction parameters as input, is greater and more concentrated than its real value. After adding the material parameters in the input, however, the dry density is more dispersely distributed and has a greater uncertainty, which gives a more objective fitting and reduces the sidedness of pit sampling and compaction parameters control.
		2015 Vol. 34 (9): 146-152 [Abstract] ( 223 ) PDF (858 KB) ( 311 )

	153	Modeling and simulations of buoys array for multipoint direct-drive wave energy converter
		YANG Shaohui, HE Guangyu, HE Hongzhou, WANG Fengying
		DOI: 10.11660/slfdxb.20150920
		A new multipoint direct-drive wave energy converter is presented and the device’s working principle is described. The simulation model of the buoys array was established and parameter setting and finite element mesh generation were conducted. This model was used to analyze the hydrodynamic response characteristics of the buoys array under different wave directions with the buoys being in three arrangements including: a circular type, a double rows type and a single row type. The influence of different buoy arrangement types on energy conversion capability has also been examined. Results reveal that the buoy array is more stable and efficient when all of the buoys are arranged in circular type and the best buoy spacing is about 8 to 10 meters.
		2015 Vol. 34 (9): 153-158 [Abstract] ( 200 ) PDF (356 KB) ( 583 )