Journal of Hydroelectric Engineering

水力发电学报

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2016 Vol. 35, No. 4 Published: 2016-04-25

	1	Ecological baseflow: Progress and challenge
		XU Zongxue, WU Wei, YU Songyan
		DOI: 10.11660/slfdxb.20160401
		Human activities through the building and operation of dams and reservoirs have significantly altered the natural hydrological regime, leading to impairment of river ecosystem function and biodiversity. The concept of ecological baseflow emerged to mitigate the impact of dams and reservoirs on the hydrological processes. Based on previous studies, the fundamental concept of ecological baseflow was reviewed. The principles of ecological baseflow, as well as previously and currently used estimation methods were summarized. Challenges and possible tendency in the estimation of ecological baseflow were also presented.
		2016 Vol. 35 (4): 1-11 [Abstract] ( 445 ) PDF (624 KB) ( 805 )

	12	Variable period progressive optimality algorithm for optimal dispatch of cascade reservoirs
		ZHANG Cheng, ZHOU Jianzhong, WANG Chao, ZHANG Yongchuan, MO Li
		DOI: 10.11660/slfdxb.20160402
		In optimal dispatch for cascade reservoirs, the progressive optimality algorithm (POA) suffers from premature convergence caused by poor initial solution . To solve the problem, this paper explores the key factors that influence the global convergence behavior of POA and presents a variable period progressive optimality algorithm (VPPOA). This new algorithm adopts a progressive differential strategy and a variable period strategy to replace respectively the approach used for solution of two-period optimal problems and the two-period optimal strategy in traditional POA, so that it can overcome the premature convergence problem caused by poor initial solution. Simulation results of optimal dispatch for the lower Jinsha River show that the gain in total electricity generation from VPPOA optimization is 0.15% more than that from POA and VPPOA-optimized solutions are nearly the same as those globally-optimized. Thus, this algorithm significantly reduces computational cost and improves the optimal dispatch of cascade reservoirs.
		2016 Vol. 35 (4): 12-21 [Abstract] ( 440 ) PDF (1299 KB) ( 911 )

	22	Numerical study on minor head loss of on-line emitters in drip irrigation laterals
		WANG Yalin, ZHU Delan, CHEN Junying, ZHENG Chao, LIU Yanfang, SONG Bo
		DOI: 10.11660/slfdxb.20160403
		Drip irrigation is one of the most effective irrigation methods in water saving irrigation, and accurate calculation of the head loss in its trickle laterals is the basis for its design. Calculation of the frictional head loss has been basically formed into a unified understanding, but the trends of minor head loss have not yet come to an agreement due to the complexity of emitter forms and diversity of emitter layouts. To examine the effects of on-line emitters on the local flow resistance and flow characteristic of laterals, this study has conducted laboratory tests on two types of laterals with different emitters. Water flows in these laterals were simulated using a computational fluid dynamics (CFD) method, and verified with the experimental data. The results show that numerical simulations were in good agreement with the experimental data and they provide useful information for investigation of the minor loss of emitters. We have conducted simulations for nine different designs of laterals and examined the influence factors of minor loss coefficient under different flow regimes. Simulations reveal that in both the laminar and turbulent flow cases, the minor loss coefficient of laterals decreased with an increasing Reynolds number, and increased with an increasing cross-sectional area ratio of the emitter to the pipe. The ratio of minor loss to frictional loss was related to the spacing of emitters and emitter discharge. The head loss of laterals in laminar regime was relatively small and may be neglected in preliminary calculation. This study would help the hydraulic calculation of drip irrigation laterals.
		2016 Vol. 35 (4): 22-31 [Abstract] ( 286 ) PDF (442 KB) ( 495 )

	32	Combined dispatching charts of cascade hydropower stations on Yalong River, Jinsha River and Yangtze River
		LI Yinyin, ZHOU Jianzhong, ZHANG Shiqin, HUANG Chunlei, YAN Dong
		DOI: 10.11660/slfdxb.20160404
		Hydropower station operation is based on an dispatching chart. Most of the existing studies, however, are focused on the dispatching charts for a single reservoir or single cascade of reservoirs, rather than multi-cascades. This paper decribes an approach to design a combined dispatching chart for joint scheduling of all the hydropower stations in a whole basin, by combining the single-reservoir dispatching charts of all the reservoirs in its sub-basins and taking the leading reservoirs in the upper reaches of each sub-basin or sub-cascade as the main control objective. As a case study, we have considered four leading reservoirs and three sub-basins: Ertan reservoir on the Yalong River, Xiluodu reservoir and Xiangjiaba reservoir on the Jinsha River, and Three Gorges reservoir on the Yangtze River. This approach adopts a method of power output allocation and an adaptive discrete differential progressive optimality algorithm to optimize the combined dispatching chart and maximize the generating capacity of each sub-cascade and the total capacity of the whole basin hydropower system separately, by means of numerical simulations based on the historical runoff records. Its application to the system of the above three sub-basins along with the four leading reservoirs indicates that the combined dispatching chart significantly improves the power generation benefit of this hydropower system while guaranteeing the power output of each sub-cascade.
		2016 Vol. 35 (4): 32-40 [Abstract] ( 421 ) PDF (679 KB) ( 744 )

	41	River-lake patterns to support lake functions of East Dongting Lake
		CONG Zhentao, LI Qinshu, ZHANG Danwu, ZHENG Ying
		DOI: 10.11660/slfdxb.20160405
		Dongting Lake, the second largest freshwater lake in China, is facing various challenges coming from relatively low water levels due to climate changes, the operation of the Three Gorges project, and the development of social economies. The lake functions are supported by certain hydrological conditions. This paper analyzes the river-lake patterns of this lake with different water stages at the Chenglingji hydrological station. These patterns are divided into four phases, i.e. river-like patterns at the water stages below 22 m, river-dominated patterns at the stages of 22-24 m, lake-dominated patterns at the stages of 24-26 m, and lake-like patterns at the stages above 26m, corresponding to lake-river indexes smaller than 1.0, 1.0-1.7, 1.7-4.3 and larger than 4.3 respectively. In-situ observations during 1950-2012 show that the annual mean percentage time periods during which the four phases occurred within a year, were 45%, 13%, 16% and 26% respectively. And the periods of both lake-dominated and lake-like patterns were presenting a decreasing trend. We have applied a wetted perimeter method to examine the relationship of lake functions versus water stage, and come to the conclusion: To maintain the functions of East Dongting Lake, the Chenglingji water stage should be in the range of 24-26 m and its annual occurrence longer than 60 days.
		2016 Vol. 35 (4): 41-46 [Abstract] ( 343 ) PDF (606 KB) ( 570 )

	47	Estimation of bankfull discharge at reach scale and influence factor analysis
		HE Li
		DOI: 10.11660/slfdxb.20160406
		Bankfull discharge at reach scale possibly contains the influence of various factors in a river reach and hence it is a better representative of the whole reach. This study has estimated such a bankfull discharge and the corresponding bankfull stage using a convergence method and WOL method based on morphological criteria respectively. The bankfull discharge and the convergence river length were estimated from the geometry data of the Inner Mongolia reach of the Yellow surveyed in the years of 1962, 1982, 1991, 2000, and 2004. Analysis shows that the river length for estimating the bankfull discharge at reach scale was increasing from 1962 to 2004. Other influence factors were also examined, including the definition of main channel and the averaged spacings of cross-sections and subsections. It reveals that the definition of main channel could be a significant factor in estimation of bankfull discharge.
		2016 Vol. 35 (4): 47-54 [Abstract] ( 303 ) PDF (1389 KB) ( 461 )

	55	Three-dimensional numerical simulation of dam-break flood routing based on fine terrain modeling
		WANG Xiaoling, SONG Mingrui, ZHOU Zhengyin, AO Xuefei, WANG Cheng
		DOI: 10.11660/slfdxb.20160407
		Previous three-dimensional numerical simulations of dam-break floods lacked detailed terrain modeling for complex underlying surface in urban regions. This paper presents a fine terrain modeling method based on TIN and NURBS. The method can be combined with an equivalent roughness method to distinguish the influences of flow resistance in different underlying surface conditions, so that it provides detailed underlying surface information for simulations of dam-break flood routing. To simulate the flood routing, a modified RNG k?ε model coupled with the VOF method was adopted and its accuracy was verified by model validation. We simulated dam-break flood cases for an urban reservoir with complex downstream inundation areas and analyzed the hydrological information including flood routing process, flow rate and water depth. The results show that the terrain modeling method reduces data storage and has good accuracy, and that the dam-break flood model simulates flood routing satisfactorily, thus reflecting the complex flow patterns and the details of the flows.
		2016 Vol. 35 (4): 55-66 [Abstract] ( 406 ) PDF (4718 KB) ( 812 )

	67	Characteristics of free surface vortices in hydraulic intakes
		SUN Hongliang, LIU Yakun
		DOI: 10.11660/slfdxb.20160408
		In this study, a flume experiment was conducted on free surface air-core vortices and the data was measured using Particle Image Velocimetry (PIV). Tangential velocity distributions, circulation distributions and water surface profiles of the vortices have been obtained. Based on these experimental data and theoretical analysis, we developed a mathematical model that describes the vortex characteristics including the equations for tangential velocity distributions and water surface profiles. Comparison with previous mathematical models shows that our model agrees with the experimental data better, and it gives a maximum tangential velocity of that is close to the measurements. The formulae presented in this paper can predict the same tendency of smooth and continuous variations as shown by our measurements. The results would help solve the vortex problems in the research and engineering application of hydraulic intakes.
		2016 Vol. 35 (4): 67-71 [Abstract] ( 332 ) PDF (922 KB) ( 802 )

	72	Numerical analysis of capsizing stability of ring gate during emergency shutdown of hydro-turbines
		MO Zhenwei, XIAO Juliang, WANG Gang
		DOI: 10.11660/slfdxb.20160409
		Unsteady Reynolds-averaged Navier-Stokes equations of viscous uncompressible fluid have been solved for simulations of three-dimensional unsteady turbulent flows to study the capsizing stability of a ring gate of hydro-turbines during emergency shutdown. The fluid dynamics software FLUENT was used to calculate the capsizing moments acting on the ring gate during emergency shutdown. A mathematical model of the capsizing stability was developed on the basis of an analysis on gravitational effects and capsizing moments, and the capsizing stability was evaluated using the model parameters of a specific ring gate. The results show that this ring gate had certain capsizing risk under an unbalanced lateral force in the whole emergency shutdown process and its resultant capsizing moment reached the maximum at a closing stroke of 95%. During its entire dynamic closing from the start to complete closure, its lateral displacements were always within certain limits inside the allowed gap between it and stay vanes. Therefore, the ring gate will not get stuck on the stay vanes, maintaining a well running stability during emergency shutdown.
		2016 Vol. 35 (4): 72-79 [Abstract] ( 383 ) PDF (1077 KB) ( 553 )

	80	Short-term prediction model of river tidal bores based on chaos optimization algorithms and BP neural networks
		WANG Ruirong, XUE Chu, CHEN Haolong
		DOI: 10.11660/slfdxb.20160410
		To improve the accuracy of tidal prediction, this paper presents a time series model using artificial neural network combined with chaos theory, and this model has been developed to overcome the limitation of empirical model and traditional neural network model. It determines the existence of chaotic behaviors in the data series of every-other-day difference in tidal time; then, phase-space reconstruction for the error series of empirical model is applied to neural network inputs. The model can give a prediction of errors that is useful for modifying or updating the final results. Prediction of the tidal times during one month at four tide observation stations on the Qiantang River shows that the model reduces the root mean square error (RMSE) by 83.9% and has accuracy higher than the traditional model.
		2016 Vol. 35 (4): 80-88 [Abstract] ( 316 ) PDF (876 KB) ( 746 )

	89	Roadbed deformation on reservoir bank for Jin'anqiao hydropower station
		LIU Wenyue, ZHANG Linghong, PENG Shaoyong, DUAN Xiang, DAI Xueyu
		DOI: 10.11660/slfdxb.20160411
		At the present time, many roads are built along a riverbank or reservoir bank. But changes in groundwater table as responses to the changes in reservoir stage, could cause the roadbed to subside or uplift, even into uneven deformation, resulting in failure of pavement structures and even landslides. In this work taking the study case of Jin'anqiao reservoir, a two-dimensional saturated-unsaturated seepage model for slopes in the reservoir region has been developed to simulate the time evolution of seepage flow in the conditions of water stage fluctuations, and to analyze the corresponding unsaturated subsidence of reservoir bank roadbeds, along with the influence of changes in reservoir stage on roadbed subsidence or uplift. The results show that the roadbed deformation is related to the fluctuations in reservoir stage and its time rate of change. First, the reservoir bank roadbeds and slopes take uplift deformation as reservoir stage rises, while they take subsidence deformation as the stage falls. Second, the subsidence or uplift of the slopes and roadbeds closer to reservoir bank depend more on the fluctuations in reservoir stage than do those farther away from the bank. Finally, there exists a positive correlation between the subsidence of reservoir bank roadbeds and the falling rate of reservoir stage.
		2016 Vol. 35 (4): 89-97 [Abstract] ( 317 ) PDF (1429 KB) ( 554 )

	98	Deformation coordination and seepage prevention of asphalt concrete core-wall and transition layers
		JIANG Shijun, YANG Jurui, TANG Min, WANG Qiang, LI Tantan
		DOI: 10.11660/slfdxb.20160412
		This study has conducted numerical simulations using a three-dimensional finite element method and an analysis on the deformation coordination of core-wall and the transition layers on its both sides for an earth dam with a homogeneous asphalt concrete core-wall in Yunnan province, focusing on core-wall anti-seepage effect and its trend of variation with core-wall thickness. A constitutive model for simulations of the dam body and core-wall was based on the Duncan E-B model. For the cases of different core-wall thicknesses, simulation data were analyzed and the deformation coordination and core-wall anti-seepage effects were compared. Results show that with core-wall thicknesses of 0.3, 0.4 and 0.5 m, most of the horizontal displacements can be well coordinated, but the stream-wise horizontal displacement is increased with an increasing core-wall thickness, resulting in an obvious arch effect in late stage, which is an adverse condition to horizontal deformation. As for vertical deformation, the subsidence of core-wall and transition layers becomes larger as elevation increases, and an increase in core-wall thickness will reduce the peak subsidence. Relative to the transition layers, subsidence of the upper core-wall is smaller while the lower part greater, so that a phenomenon that the whole core-wall has been "stretched" vertically can be observed. This provides a favorable condition to enhance the core-wall arching effect. Since the core-wall is dominated by compressive stress according to the calculations, hydraulic fracturing damage will be impossible. For a dam body imbedded with an asphalt concrete core-wall, its saturated surfaces are lowered significantly and its anti-seepage effects become better; the seepage flow decreases with an increasing core-wall thickness.
		2016 Vol. 35 (4): 98-107 [Abstract] ( 287 ) PDF (1102 KB) ( 670 )

	108	Analysis of influencing factors on penetration rates of double-shield tunnel boring machine
		XU Jian,YAN Yanbin, HU Xiaolin, LU Lijuan
		DOI: 10.11660/slfdxb.20160413
		This study has developed two-layer linear models using a method of progressively deleting insignificant explanatory variables based on the initial explanatory variables specified and by applying the principles of hierarchical linear model and quantitative theory, and analyzed the factors that influence the penetration rates of double-shield tunnel boring machines (TBM) using the in-situ data of tunnel No. 9 of the Tao River diversion project phase I. We also quantitatively describe the direct and indirect impacts by these factors, using model parameter estimates for the fixed effects of each explanatory variable in the models; based on these estimates, suggestions for better TBM operation are put forward. The results indicate that our method is feasible in prediction of the tunneling penetration rates, and it would be useful for forecasting the construction progress and control management in similar projects.
		2016 Vol. 35 (4): 108-116 [Abstract] ( 313 ) PDF (578 KB) ( 543 )

	117	Triaxial creep characteristics and models of remolded loess under separate and graded loading
		GUO Hong, LUO Yasheng, WANG Pengcheng
		DOI: 10.11660/slfdxb.20160414
		Three sets of consolidated drained triaxial creep tests along different stress paths have been performed using a SR-6 triaxial creep deformation meter for the samples of remolded loess taken from a loess slope in Xianyang city, Shaanxi. This study focuses on loess creep characteristics along two paths, i.e. separate loading and graded loading, and determines the parameters of Burgers model to establish an empirical conversion formula of stable creep deformation between these two paths and to develop a discrete element model of creep deformation. The results indicate that the overall trends of creep deformation along the two paths were nearly the same showing a decay tendency but on a certain level of deviatoric stress, a greater stable deformation was resulted under graded loading than separate loading. Burgers model can describe the creep properties of the loess samples satisfactorily, and the values of stable deformation can be conveniently converted between the two loading paths using the conversion formula. And our simulation results of the discrete element model are also satisfactory.
		2016 Vol. 35 (4): 117-124 [Abstract] ( 406 ) PDF (532 KB) ( 760 )

	125	Mixture design and properties of roller compacted concrete with high dolomite powder content
		GE Xueliang, LU Cairong, MEI Guoxing
		DOI: 10.11660/slfdxb.20160415
		An experimental study of roller compacted concrete with high dolomite powder content has been conducted for design of a hydropower station in Southwest China to expound and prove the feasibility of using dolomite powder as a substitute for fly ash and a mineral admixture of such concrete. The results show that roller compacted concrete of strength grade C9020 can be prepared by using dolomite powder content in the range of 50% ~ 55%, reducing water/cement ratio, and increasing cement content, through application of reasonable mixture design and parameter optimization. Its frost resistance and permeability resistance, along with its ultimate extension and tensile strength etc., can all meet design requirements. Thus, this study has proved the feasibility of high dolomite powder content technology for mix of roller compacted concrete.
		2016 Vol. 35 (4): 125-130 [Abstract] ( 313 ) PDF (453 KB) ( 556 )