Journal of Hydroelectric Engineering

水力发电学报

Office Online

Included Databases

The journal is included in the following databases:
(i)Scopus,
(ii)The Chinese Science Citation Database Source Journals,
(iii)The Chinese Science Journal Abstract Database,
(iv)The Chinese Science and Technology Papers Statistics and Analysis Database,
(v)China Newspaper Subscription Guide Information Database,
(vi)Chinese Academic Journals (CD).


2015 Vol. 34, No. 4 Published: 2015-04-25

	1	Study on hierarchical rules of Three Gorges reservoir for regulating small and medium floods
		HU Ting, ZHOU Man, WANG Hai, HU Xinge, GAO Yan
		In recent years, the upstream inflow of Three Gorges reservoir (TGR) is decreasing and in the upper reaches controlling reservoirs are being built up and running successively. Meanwhile, the requirements of flood control, power generation, navigation, etc. on TGR are enhanced increasingly. In these new circumstances, the reservoir's original design operation mode cannot satisfy the latest demands very well and may cause a great amount of flood resources to be wasted. This paper describes new hierarchical operation rules and multiple schemes for TGR to regulate water level according its inflow of small and medium floods through analysis on the historical record of its special water levels and outflows. Results indicate that without lowering the design flood control standard, these new rules can significantly improve the regulation in flood season and the comprehensive utilization benefits, in alleviating the pressure in lower reaches via more reasonable flood interception, extending navigation period, and utilizing flood resources more effectively. Compared with the original operation, the annual average power output during flood season is increased by 8%.
		2015 Vol. 34 (4): 1-7 [Abstract] ( 156 ) PDF (16442 KB) ( 100 )

	8	Runoff responses to climate change in Qinglong river watershed based on SWAT model
		QU Jihong，SHI Hongwang，LI Zhiyan
		Climate change impacts on temporal and spatial patterns of water resources and assessment of this impact is important. To study runoff responses to climate change, we developed a distributed hydrological model of the Qinglong River watershed on the platform of Soil and Water Assessment Tool (SWAT), accounting for digital elevation models of the watershed and its data of land use, soil types, etc. A sequential uncertainty fitting version 2 (SUFI2) algorithm in SWAT-CUP software was used for sensitivity analysis, calibration, validation, and uncertainty analysis, including sensitivity analysis on the t-Stat and p-Values and model evaluation in terms of efficiency coefficient Ens and its correlation coefficient R2, Pfactor, and Rfactor. The results indicate that this model based SWAT is applicable to river watershed runoff modeling. In its application to simulations of the river runoff in different level years, hypothetical schemes of climate change were designed by combinations of precipitation and temperature conditions. Simulations show a significant influence of climate change on runoff. The runoff is increased by an increase in precipitation or air temperature and it is more sensitive to precipitation.
		2015 Vol. 34 (4): 8-15 [Abstract] ( 157 ) PDF (22493 KB) ( 143 )

	16	Copula function method and its application to prediction of runoff
		CHEN Jing, WANG Wensheng
		Copula function is used to combine the correlation degree and relevance pattern of independent variable and dependent variable. A joint distribution function can be constructed, and its interrelated structure with the two variables is analysed. Then, expressions for the relation of the marginal distribution of dependent variable versus the joint distribution are formulated, and the unknown value of dependent variable is predicted through a combination with the known sample value of probability distribution of independent variable. Case study of annual runoff prediction shows that this Copula prediction method has a clear theoretical basis and it is stable and accurate. This method not just provides new ideas for hydrological prediction, but offers new insights into Copula function.
		2015 Vol. 34 (4): 16-21 [Abstract] ( 191 ) PDF (13727 KB) ( 135 )

	22	Tsinghua hydrological model based on representative elementary watershed coupling sediment and its application
		LIU Dengfeng,TIAN Fuqiang,HUANG Qiang
		The establishment of the watershed hydrological model at the macro-scale and the simulation of the sediment delivery in the catchment are the key research issues in the watershed hydrological modeling, in which the coupling simulation of the water and sediment in the watershed is the key issue. On the basis of the hydrological model based on Representative Elementary Watershed which is applicable to macro-scale, the paper introduces the sediment erosion and delivery to build up the water-sediment coupling model. With the simulation of the changing channel slope in the water-sediment delivery, the model achieves the water-sediment coupling modeling in nature. To deal with the limitation of the channel coding of binary tree, the virtual computation unit is used into the model. The high-resolution remote sensing image is employed to measure the river width and it provides a new method for the hydrological modeling in the ungauged basins. The results shows that, the performance of the hydrological modeling is very good, and simulated and observed sediment discharge are consistent in terms of total sediment load and intra-annual process. Most of the channel slopes of the watershed are steady and parts of the reaches are in the evolvement.
		2015 Vol. 34 (4): 22-30 [Abstract] ( 190 ) PDF (23384 KB) ( 307 )

	31	Application of historical flood-concerned mixed distribution with different tail types of PDFs
		TANG Yihan, CHEN Xiaohong, YE Changqing, ZHANG Jiaming, ZHANG Lijuan
		Historical flood-concerned mixed-distribution method (HFCMM) not only extends sample length of flood runoff data but improves the traditional flood frequency analysis lacking physical ground. This study applied this method to Annual Maximum Flood(AMF) series from the Wujiang basin and developed a mixed-distribution model of annual maximum flood runoff, using historical flood-concerned L-moment for parameter estimation. Comparison of the modeling results for different Probability Distribution Function(PDF) tail types shows that HFCMM increases the recurrence intervals of high flood flows and improves their flood frequency analysis by adopting heavy-tailed or three-parameter mix-tailed PDFs but not two-parameter mix-tailed PDFs. But with thin-tailed PDFs fitting, the method reduces the recurrence intervals of low flood flows, and thus this fitting is not recommended. For flood frequency analysis of the Wujiang basin by HFCMM, the distributions of GLO and GEV fit better than the traditional Pierson III.
		2015 Vol. 34 (4): 31-37 [Abstract] ( 185 ) PDF (47162 KB) ( 115 )

	38	Study on optimization of water resources allocation in the Tarim River
		HUANG Qiang，ZHAO Guannan，GUO Zhihui，ZHOU Haiying
		Aiming at a solution to the Tarim River basin's drought, fragile ecological environment, and other issues, this paper analyzes its existing conditions of water resources development and utilization, then proposes ideas for its rational allocation of water resources and principles and priorities of water supply and develops a figure of water distribution network nodes. We established a model for optimal allocation of water resources that minimizes the total shortage of water, using an optimization algorithm for solution of the model. Seven scenarios of different configurations were examined, and by a comparison of their results we recommended two water resources allocation schemes for two target years of planning respectively, satisfying the requirements of guaranteed rate. This study is a technical support to achieving global control and reasonable allocation of the water resources in the Tarim river basin, and would also be useful for water resources allocation in other arid regions.
		2015 Vol. 34 (4): 38-46 [Abstract] ( 176 ) PDF (23422 KB) ( 278 )

	47	Experimental study on energy dissipation ratio of pure steps on stepped spillway
		ZHANG Feng, LIU Hansheng
		At present, energy dissipation ratio is a factor widely used in the study of energy dissipation characteristics of stepped spillways, but smooth spillways also have a definite rate of energy dissipation and only the difference in energy dissipation ratio between a smooth spillway and stepped spillway has practical significance. This paper describes a new parameter, the energy dissipation ratio of pure steps, and presents our experimental results on this parameter. On the hydraulic models of stepped spillway, three mean bottom slopes and different step heights were tested systematically. Analysis on the measurements indicates that under different unit discharges and different step heights, pure steps have a dissipation ratio of 5% less than that of stepped spillway and their dissipation ratio varies linearly with the length of flow path. As a result, their dissipation ratio per unit flow path under different discharges or different step heights can be regarded as a constant. The analysis also shows a change of 10.4% in the ratio when the mean spillway slope is decreased from 55° to 32°. Thus, the energy dissipation ratio of pure steps is a suitable parameter for simplification and improvement on energy dissipation study.
		2015 Vol. 34 (4): 47-50 [Abstract] ( 211 ) PDF (10617 KB) ( 348 )

	51	Study on impact of flaring gate pier shapes on aeration and energy dissipation of stepped spillway
		HOU Xiaoxia, YANG Jurui, XIONG Changxin
		New energy dissipater of flaring gate pier combined with stepped spillway has effectively solved the problems of high-velocity flow caused by high working head and large unit discharge. This study applied a 3D flow model with RNG turbulence modeling, VOF water vapor two-phase modeling, and PISO algorithm for velocity-pressure coupling on FVM geometry reconstruction of iterative solution, to simulations of aerated flows over a stepped spillway and its energy dissipation behaviors. At the spillway entrance are Y-shape flaring gate piers and their contraction ratios of 0.7, 0.445 and 0.4 were examined and compared. The results show that under different contraction ratios of the piers the cross-sectional average of air concentration fluctuates with a decreasing global trend along the flow, and that the aerated regions over the steps are reduced when the contraction ratio is decreased. Over the initial several steps, the flow is full aerated and the mean air content at a fixed section is higher at a smaller contraction ratio. And the mean content near the top step faces takes an outward transverse trend of first decreasing then increasing from the center-line, while that near the vertical step faces takes a downward trend of first increasing then decreasing. Over the steps near the spillway outlet, the mean air content at a fixed section is lower at a smaller contraction ratio. And the mean content near the top step faces increases outward, while that near the vertical step faces decreases downward. The energy dissipation rate of this stepped spillway is increased with a decreasing contraction ratio of the Y-shape flaring gate piers.
		2015 Vol. 34 (4): 51-58 [Abstract] ( 198 ) PDF (16734 KB) ( 331 )

	59	Analysis on numerical simulations of hydrodynamic conditions in Egongyan reach after operation of Three Gorges reservoir
		LUO Quansheng，GENG Yajie
		This article is based on the Three Gorges reservoir's operation at water level 175 m and the collected data of topography, hydrology and sediment measurements. We examine the backwater effects in the fluctuating backwater zone of the reservoir after its impoundment. A 2D depth-integrated flow model was adopted in the framework of a SMS surface water simulation code for simulation of the representative Egongyan reach located in the middle of the fluctuating backwater zone, focusing on its hydrodynamic and bedload transport conditions and their responses to the impoundment. The results provide technical support to analysis of riverbed evolution, waterway management, and waterway regulation.
		2015 Vol. 34 (4): 59-62 [Abstract] ( 189 ) PDF (12392 KB) ( 235 )

	63	Review and prospect of vertical distribution by non-equilibrium sediment concentration theory
		ZHAO Lianjun, WU Guoying, WANG Jiayi
		Relationship of longitudinal transport and vertical distribution of sediment in a river is the one of mutual interdependence. Vertical distribution law of concentration in non-equilibrium transport is a core subject of the theory and its in-depth study is of great significance to advancement in river sediment discipline. Recent theoretical studies on this subject are lacking, while a great number of correspinding results for equilibrium tranpsort including relatively mature theories were previously reported. This paper focuses on an analysis of Hanqiwei's theory about the sybject, and suggests that further discussion is needed on his assumption that the parameter of vertical average concentration distribution in equilibrium transport is applicable to derivation of the formula for non-equilibrium cases. We also suggest that it would be impossible to achieve a breakthrough in the vertical distribution law of sediment concentration in non-equilibrium transport until a great numbe of detailed flume tests are completed. And a demonstration of such tests is included.
		2015 Vol. 34 (4): 63-69 [Abstract] ( 198 ) PDF (18584 KB) ( 94 )

	70	Hydrodynamic simulation of multi-pendulum wave power converter
		LI Chenglong, ZHANG Jun, HE Hongzhou, YANG Shaohui,QU Quanyou
		Multi-pendulum wave power converter is a device for better ability to capture wave energy by taking advantage of its multi-pendulums. Hydrodynamic performances of a multi-pendulum system and a single pendulum system are examined in this study, using numerical simulation on the three-dimensional potential theory and considering different gap sizes of pendulum. The results show that in a multi-pendulum system, the interaction of its multi-pendulum produces resonances of peak values different from those in a single pendulum system, and that as the gap size increases, its influence on hydrodynamic performance takes a trend of first increasing then decreasing.
		2015 Vol. 34 (4): 70-76 [Abstract] ( 150 ) PDF (17153 KB) ( 85 )

	77	Study on roughening method of hydraulic model with grass cushions
		ZHAO Haijing，TIAN Shimin，WANG Pengtao3，SUN Dongpo
		A series of experimental tests on roughening method with grass cushions were conducted in this study. The ranges of roughness induced by different grass cushions were determined and a relationship of roughness versus Froude number obtained. We also analyze the influence of these cushions on the bottom flow and suggest the minimum flow depths suitable for application of the roughening method. The method was applied in hydraulic model tests on integrated schemes of regulating the Qian’an reach of the Luan River. The experimental results illustrate that the enhanced roughness by grass cushions satisfies the requirements of hydraulic modeling, and improves the modeling results of the characteristics of river channels.
		2015 Vol. 34 (4): 77-82 [Abstract] ( 133 ) PDF (16441 KB) ( 76 )

	83	Study of hydrodynamics and morphology relationships for macro-tide estuaries
		HAN Zengcui，TANG Ziwen，YOU Aiju，CAO Ying，XING Yun
		By the definition of bed forming discharge, sediment transports during flood tide and ebb tide of various tidal frequencies were calculated for a tidal estuary. The results show that the bed forming effects are the strongest at annual average runoff combined with mean ebb tide, so the bed forming discharge of this estuary should be the ebb-tide discharge. Tidal estuaries can be categorized as two types, namely general estuary and tidal bore estuary. The former's characteristics of cross section depends on average ebb-tide discharge and average sediment concentration, while for the latter, its width of cross section depends on average flood-tide discharge, and its corresponding depth, longitudinal widening rate and bed slope of river channel are determined by both flood-tide and ebb-tide discharges and sediment concentration. This paper formulates a series of empirical relationships between hydrodynamics and morphology for macro-tide estuaries. Using the measured cross-sectional bed profiles of five estuaries in Zhejiang province, we have verified these formulas of river regime, including cross-sectional area, width and depth, width-depth ratio, widening rate, expanding rate of cross-section area, river bed slope, etc. Their average calculation errors are less than 10%, and the calculations with errors exceeding 90% are less than 20%. The formulas, through certain conversion, show that the cross sections below half-tide levels correspond to the ones for sediment recipient motions.
		2015 Vol. 34 (4): 83-90 [Abstract] ( 214 ) PDF (17701 KB) ( 274 )

	91	Features and effects of recent cross-section adjustment in gravel and sand bed reaches of Jingjiangriver
		HAN Jianqiao, SUN Zhaohua, CAO Qixin, HUANG Ying
		By using the hydrologic, morphological and geological observations in the Yangtze reach from Zhicheng to Dabujie, cross-section deformation and its spatial variations are examined and responses of water level to this deformation are investigated. The inconsistency in cross-section adjustment in different regions is revealed. In the upper reach, lateral erosion is the major deformation and erosion intensity is greater in an expanding section than contracting section, causing the channel wider and shallower at low level. In the lower reach, down-cut erosion dominates the deformation at all the water levels and the channel develops toward the opposite, narrower and deeper. The difference of the two reaches in dominant deformation is a result of the comprehensive effect of different mainstream swings and riverbed materials. Water level drop caused by erosion under different discharges, is uneven in magnitude over the whole reach, greater in the sections of lateral erosion than vertical erosion. Thus, Changmenxi is a location of deformation transition from lateral erosion to down-cut erosion and the protective measures should be distinguished.
		2015 Vol. 34 (4): 91-97 [Abstract] ( 185 ) PDF (22751 KB) ( 73 )

	98	Study and practice of the Three Gorges Reservoir regulations for sedimentation reduction in its tail region
		ZHOU Man，HUANG Renyong，XU Tao
		Afterthe impoundment of the Three Gorges Reservoir, major period of erosion in the tail reaches has gradually changed from the period of September to October undernatural condition to fluctuating period of April to June. In order to increase the erosion in fluctuating period and reduce the sedimentation in local reaches which may block navigation. Regulations to reduce sedimentation in the tail area of the reservoir are presented based on one-dimensional unsteady flow-sediment model. It is shown that better erosion effects can be achieved by controlling the stage in front of the dam within the range of 160~162m and the stage fall in a day within 0.4~0.6m in the condition of Cuntan flow about 7000m3/s. According to these results, in-situ experiments were successfully completed in the fluctuating periods of 2012 and 2013. Analysis of the measured data indicate that the total erosion in the tail reaches is 2.411 and 4.413 million m3 during the two years' regulation periods respectively, a good effect in sedimentation reduction. The measured data in 2012 were used to validate the mathematical model. A comparison with the calculations shows that the model is effective in qualitative calculation of erosion and deposition and basically reasonable in quantities for most of the reaches.
		2015 Vol. 34 (4): 98-104 [Abstract] ( 87 ) PDF (17125 KB) ( 92 )

	105	Study on small-fluctuation transient process in long diversion tunnel of hydropower station on infinite power grid
		LI Ling，YANG Jiandong，LIU Meiqing
		For a hydropower station with long-distance diversion tunnel, extremely large inertia of the tunnel flow leads to long fluctuation cycles, large amplitudes and slow decay of the water level in its surge tank. For those stations on an isolated grid, the regulation quality of transient process in small fluctuations using the traditional PID control law is poor and the fluctuations decay slowly. In this case, the cross-sectional area of surge tank often needs to be increased to improve stability, resulting in a higher project cost. If the stations connect to an infinite power grid, however, no previous studies on their stability and regulation quality are available. This paper constructs a detailed simulation model of hydraulic-mechanical-electric systems on infinite power grid, using the platform of Matlab software and its toolbox of Simulink and SimPowerSystems. This model is used to study the stability and regulation quality of hydropower stations with long diversion under small fluctuations. The results lay a basis for design and operation control of such hydropower stations.
		2015 Vol. 34 (4): 105-110 [Abstract] ( 151 ) PDF (14085 KB) ( 80 )

	111	Study on energy dissipation method - lateral jetting of side spillway into plunge pool
		LIU Wen，DENG Jun，WEI Wangru，XIA Pengfei，LIU Xiaoxuan
		This article describes a new layout of side spillway that scatters water flow laterally into an existing parallel-arranged plunge pool to achieve energy dissipation. Hydraulic model tests and numerical simulations were used in the study focusing on analysis of hydrauliccharacteristics of the flow over spillway and the flow patterns in plunge pool. The results show that removal of one part of the sidewall at an appropriate location combined with a sloping pool bottom can provide a condition for a certain portion of the flow to fall laterally into the pool uniformly along its way. At the opposite sidewall of spillway, a circular-curve contraction is adopted and extends downstream up to its joint with the pool sidewall. This contraction helps the rest portion of flow to jet into the pool along a path over the lateral nappe. Thus, the total jet nappe takes a shape of “∩” and it is fully stretched and expanded, then dispersed up to its pool plunging location, so as to avoid excessive impact pressure on the pool bottom. This spillway layout can not only produce little affect on the normal running of plunge pool in the case of other releasing structures in operation, but make a full use of the rear part of the existing plunge pool for dissipation of more energy, which could lead to a great saving of project investment.
		2015 Vol. 34 (4): 111-118 [Abstract] ( 153 ) PDF (21029 KB) ( 85 )

	119	Study on stress-deformation and hydraulic fracturing of rockfill dam with asphalt concrete core
		WU Hailin，PENG Yunfeng，DU Xiaofan， RAN Hongzhou
		In order to study the static characteristics of rockfill dam with asphalt concrete core in XinjiangProvince, the nonlinear three-dimensional finite element method was employed. The Duncan-Chang E-B model was chosen in this paper to simulate the filling and storing processes of the dam. Based on the theory of linear-elastic fracture mechanics, the hydraulic fracturing analysis of asphalt concrete core is performed. According to the analysis results, the stress intensities and deformation values were within safety ranges, but the asphalt concrete core wall has obvious arching effect. So we need to study the risk of hydraulic fracturing on core. The hydraulically fracturing criterion of the core is established on the based of the fracture mechanics theory, and the probability of hydraulic fracturing on core can be obtained by pre-defined fracture in the possible position. The analysis shows that the fracture could not propagate, local hydraulic fracturing couldn't occur.
		2015 Vol. 34 (4): 119-127 [Abstract] ( 180 ) PDF (25405 KB) ( 216 )

	128	Study on water stability of clayey soil under soil-water-electrolyte systems
		CHEN Hua, FAN Heng-hui, NIE Yong, HE Zhi-qiang
		Theory of electric double layer shows that the cationic type of aqueous solution and its concentration influence dispersivity of clayey soil. The dispersive characteristics of this soil in a soil-water-electrolyte system were studied for solutions containing different concentrations and cations through pin-hole tests, crumb tests, and disintegration tests on non-dispersive soil, transitional soil, and dispersive soil. The results show that non-dispersive soil behaves dispersive or transitional in a solution containing a certain content of alkaline and sodium ions and conversely, the dispersivity of both dispersive soil and transitional soils is weakened gradually by an increase in the concentration of electrolyte solution. For dispersive soil in deionized water, if its dispersivity is increased, the speed of its disintegration becomes slower and a longer time is needed for a full disintegration. For non-dispersive soil in any types of electrolyte solution or in deionized water, the rate of its disintegration is nearly the same, while dispersive soil in a solution of greater electrolyte concentration takes a faster rate and a shorter time of full disintegration, gradually approaching those of non-dispersive soil. A most prominent behavior of dispersive soil in disintegration is a mutation point that appears in a disintegrated soil-weight range of 20%~40% as a threshold beyond which a full disintegration will be completed in a very short time. The results also indicate that clay soil varies in dispersivity with its external media environment. Thus, a change in dispersivity of clay can be achieved in practical engineering through a change in the concentration of local seepage water. This study suggests that great attention should be paid to the mutation of dispersive soil in its disintegration, so as to avoid a rapid destruction of hydraulic structure beyond the threshold.
		2015 Vol. 34 (4): 128-138 [Abstract] ( 145 ) PDF (24922 KB) ( 224 )

	139	Analysis on seismic responses of high arch dam to SV waves of oblique incidence
		DU Xiuli， XU Haibin， ZHAO Mi
		This paper studies an input method of oblique plane seismic waves for three-dimensional calculation, which is based on a time-domain wave method coupled to an explicit finite element method with viscous-spring artificial boundary conditions. Application of this method to seismic responses of the Xiaowan arch dam under SV waves of oblique incidence is also examined. The results indicate that the responses of this dam are significantly different from those under P waves. The incidence angles of SV waves can cause more sensitive responses of displacement spectrum in low frequency domain, a range crucial to aseismic safety. Under incidence in stream direction the amplitude magnification coefficient of displacement spectrum is significantly decreased by an increase in its angle, while under incidence in transverse direction the coefficient is significantly increased.
		2015 Vol. 34 (4): 139-145 [Abstract] ( 201 ) PDF (18744 KB) ( 93 )

	146	Review and new analytical solution for internal water pressure transmission coefficient of steel penstocks with yieldinglayer
		ZHANG Yunliang
		Mechanical properties of the yielding layer have great influence on the internal water pressure on steel liners and their surrounding concrete in penstocks of hydropower station. This paper frist gives a review on the existing analytical solutions for internal water pressure transmission coefficient, and points out their drawbacks, such as the neglect of material nonlinearity and residual strain of yieldinglayer, and the gaps between steel pipe, cushion layer and surrounding concrete. Then, we present a new analytical solution considering the gaps and material nonlinearity and its verification and application in an example calculation. This study comes to the conclusions that an effective stiffness of the yieldinglayer can be defined and calculated by using a ratio parameter of effective compressive modulus over effective thickness, and that at constant effective stiffness the pressure transferred to the concrete is also constant. This work is useful for selection of material and geometrical parameters of the yielding layer.
		2015 Vol. 34 (4): 146-151 [Abstract] ( 166 ) PDF (12542 KB) ( 98 )

	152	Extraction of non-stationary vibration symptoms for hydraulic turbine using improved CWT gray moment with time-scale window
		CHEN Xiyang，TAO Ying，YAN Haiqiao，ZHANG Kewei
		Coefficients of continuous wavelet transform (CWT) of the characteristic components of a non-stationary signal can be assembled for high-amplitude energy region in time-scale plane. An improved CWT gray moment with time-scale window is constructed in this paper to represent the information implicated by a CWT coefficient figure and it can be used as a quantitative time-frequency symptom of the signal. Simulation results show that this method captures effectively the time-frequency amplitudes of mutations components and its successful application to vibration analysis on the hydraulic turbines at the Three Gorges hydropower station has produced useful time-frequency information of non-stationary vibrations. Thus, the CWT method provides a new quantitative approach to extraction of hydraulic turbine vibration symptoms.
		2015 Vol. 34 (4): 152-156 [Abstract] ( 148 ) PDF (13864 KB) ( 297 )

	157	Calculation of lubricity and analysis of influencing factors for small spring-supported thrust bearing
		ZHI Falin， HU Weiqiang， YAN Zongguo， WANG Zhengwei
		Small spring-supported thrust bearing, advantageous in great bearing capacity and good heat dissipation, is widely used in the hydro turbine. To study this type of bearing, we calculated three-dimensional thermo-elastic hydrodynamic lubrication and developed a new method of equivalent spring stiffness. And we examined the influences of the thrust pad's elastic deformation and thermal deformation and the spring's compression deformation, including the factors of thrust bearing performance, i.e. rotation speed, initial temperature, thickness of thrust pad, etc. This paper presents the results and a discussion on the relationship of bearing performance versus different arrangement of the spring and comes to a conclusion that the performance depends on the number of springs in the oil region and central thrust pad's radial region and the number should be optimized at the design stage.
		2015 Vol. 34 (4): 157-162 [Abstract] ( 192 ) PDF (17314 KB) ( 82 )

	163	De-noising of hydropower unit throw based on EEMD and approximate entropy
		AN Xueli，PAN Luoping，ZHANG Fei
		A de-noising method of hydropower unit throw signals based on ensemble empirical mode decomposition (EEMD) and approximate entropy is presented. This method decomposes the throw signals into several intrinsic mode functions (IMFs) and calculates the approximate entropy for each function. Those functions of approximate entropy less than a certain preset threshold, then are reconstructed so as to eliminate the abnormal noises of the signals. It also compares the two methods of wavelet transform and EEMD in terms of their calculations of root mean square error, correlation coefficient, and signal-to-noise ratio. The results show that the EEMD method is superior in its adaptability and de-noising performance and very suitable for online de-noising of hydropower unit throw signals.
		2015 Vol. 34 (4): 163-169 [Abstract] ( 197 ) PDF (16777 KB) ( 95 )

	170	Analysis on environmental discharge of large-scale hydropower project using carbon footprint theory
		ZHANG Sherong，PANG Bohui
		A hybrid life cycle assessment method based on the carbon footprint theory is described in this paper to analyze the greenhouse gas emissions of large hydropower projects throughout their whole life cycle, focusing on demonstration of their effects on carbon emission reduction. This method, in application to the overall layout scheme of concrete gravity structures for a huge hydropower project, considers four stages of its life cycle: material and equipment production, transportation, construction, and operation and maintenance. The results show a total carbon emission of 1145.49×104t CO2e, average annual emissions of 25.46×104t CO2e, and carbon emission factor of 14.09g CO2e/kWh, which are on a level of only 1.71 percent of the corresponding coal power plant's emission. From high to low percentage of contribution to the total CO2 emission at the four stages, operation and maintenance stage of 50% comes first, then production stage of 45% and construction stage of 3%, and last transportation stage of 2%. Thus, to lower the emission, the use of cement and steel should be reduced, the construction technology of filling and excavation be improved, and the reservoir be cleaned up. This study provides more evidences that large-scale hydropower projects are clean energy resources.
		2015 Vol. 34 (4): 170-176 [Abstract] ( 196 ) PDF (18162 KB) ( 104 )

	177	Describing trust state of construction general contracting parties under DBB mode based upon study of interview and content analysis method
		YIN Yilin, HU Wenzheng, DU Yaling, LIU Yige
		Previous studies suggest that trust is a key factor in success of construction projects, and how to describe the trust state between the owner and contractor of a construction project is a very important part of project implementation. This paper summarizes the previously reported key events that represent trust in the DBB mode, and recognizes grips that can measure trust state using the data of interviews and a content analysis method, focusing on clarification of the contract parties' behaviors of trust state. Based on this, we develop a dynamic elevation model of owner-contractor trust state for the overall process of a construction project. The results have shown that the trust grips, as a measure of trust state, can help contacting parties understand better the partner's trust level and judge the effectiveness of various measures for improving the trust state, thus promoting the probability of project success.
		2015 Vol. 34 (4): 177-183 [Abstract] ( 169 ) PDF (19900 KB) ( 75 )

	184	Analysis on positive externalities of hydropower projects
		ZHENG Tengfei，QIANG Maoshan，CHEN Wenchao，WANG Jianing
		Problems of migration, ecology and benefits sharing become the most important constraints at the existing stage of China’s hydropower development after restrictions of technology, funds and market. It is necessary to build a benefit sharing system to consider reasonably all stakeholders' benefits during the life cycle of projects. This paper focuses on the output factors of hydropower projects in a benefit sharing system and the evaluation on the factors' positive externalities. Name generator is used to identify the system's output factors, which are divided into economic factors, social factors, ecological factors, etc. We analyzed the positive externalities of the factors by the externality theory, and obtained an externality analysis framework including grim benefit, disaster prevention benefit, navigation benefit, and greenhouse gas reduction. This framework has been applied to analysis of the Three Gorges project, and its results show that positive externalities exist in hydropower projects and should be fully considered in evaluation of the projects to achieve a reasonable benefit sharing system and a more effective transaction mechanism. The result lays a basis of benefit sharing system and is useful to harmonious development of hydropower resources in guiding practice and policy-making.
		2015 Vol. 34 (4): 184-190 [Abstract] ( 201 ) PDF (17824 KB) ( 84 )

	191	Study on the runoff response to climate change-a case study of source region of the Yellow River
		LV Jiqiang, SHEN Bing, LI Huaien, JIANG Yi
		In order to better understand the runoff response to climate change in the upper reaches of the Yellow River, we develop joint distribution models base on multivariate Copula theory. And obtain the quantitative relationship between the main climate factors and runoff changes through the analysis of multiple dependent structures. The results show that the runoff at the JiMai gauging station affected by climate change obviously. In the past 53 years, the Copula dependent degree index of runoff and major meteorological factors, such as temperature, precipitation, potential-evaporation capacity (Penmanand-Monteith formula) are 0.03, 0.46, 0.13, while the dominant influencing meteorological factors of runoff changes are not the same for different stages. Recharged from precipitation, ice and snow, permafrost melt water and groundwater, the runoff show a complex evolutionary process.
		2015 Vol. 34 (4): 191-198 [Abstract] ( 193 ) PDF (14243 KB) ( 301 )