Journal of Hydroelectric Engineering

水力发电学报

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2016 Vol. 35, No. 2 Published: 2016-02-25

	1	Tidal current energy update 2015—Hydrodynamics
		ZHANG Liang, SHANG Jinghong, ZHANG Zhiyang, JIANG Jin, WANG Xiaohang
		DOI: 10.11660/slfdxb.20160201
		Tidal current energy is a type of renewable and sustainable marine energy. Despite the complexity in exploitation, considerable improvement has been achieved since the beginning of the current century. This paper discusses the hydrodynamics progress through the perspective of equipment design and industrial application of tidal current energy technology, including tidal resources estimation, kinetic energy conversion, converters, and tidal farm array arrangement and design, then summarizes representative hydrodynamics problems, their theoretical models and numerical methods. Technical characteristics of converters and supporting structures are also analyzed to highlight new problems and developing trends in the present stage, offering references for optimal design of tidal energy converters and power station projects.
		2016 Vol. 35 (2): 1-15 [Abstract] ( 453 ) PDF (1399 KB) ( 1302 )

	16	Drought evolution characteristics in Wei River basin based on standardized precipitation evapotranspiration index
		TIAN Tian, HUANG Qiang, GUO Aijun, LIU Dengfeng, MING Bo
		DOI: 10.11660/slfdxb.20160202
		Drought is one of the major environmental and climate issues for humanity nowadays. A standard precipitation evapotranspiration index (SPEI) was used in this study to examine the drought evolution characteristics of the Wei River basin. Yearly and seasonal SPEI values have been calculated for each of the 21 meteorological stations in this basin, using the long series of precipitation, temperature and sunshine hours from 1960 to 2013, and the trend of yearly SPEI analyzed. We adopted methods of Mann-Kendall test, accumulative anomaly and ordered clustering to diagnose the mutation characteristic of yearly SPEI, and obtained a drought coverage and drought distribution characteristics of the basin. Results showed an overall decreasing trend in yearly SPEI with a mutation occurring in 1990, revealing a drought intensity increase in the basin from the level in 1960-1991 to a higher level in 1991-2013. The drought coverage for all the time scales in 1991-2013 except winter drought was higher than that in 1960-1991, and especially it was subjected to more rapid changes in spring. In 1991-2013, the frequency of moderate to severe drought was significantly higher than that in 1960-1991 and the frequency of continuous drought was also higher, signifying a condition of drought intensifying since 1991.
		2016 Vol. 35 (2): 16-27 [Abstract] ( 339 ) PDF (1327 KB) ( 500 )

	28	Temporal variation characteristics of annual precipitation and runoff in Luan River basin based on quantile regression
		FENG Ping, SHANG Song, LI Xin
		DOI: 10.11660/slfdxb.20160203
		Most current studies on the temporal variation characteristics of precipitation and runoff series focus on the mean features, and consequently the results provide little insight into the tail parts of distributions and are affected by anomalies easily. To solve this problem, we have applied a quantile regression method to the precipitation and runoff series of the Luan River basin. Pettitt test and Mann-Kendall test were used to analyze the temporal variations in terms of mean features. The results show that the annual precipitation series are essentially stationary while the annual runoff series manifest abrupt changes and hence are non-stationary. Therefore, no response relationship can be found between these two series. Then, we applied a quantile regression method to analyze the same series of precipitation and runoff using high and low levels of quantiles. It demonstrates that at different quantiles, the precipitation series in most sub-basins are stationary while the runoff series in all the sub-basins have a significant descending trend with a faster rate at high quantiles than those at low ones. And in several sub-basins, a good response relationship exists between precipitation and runoff at different quantiles, while in the whole basin, the relationship is not obvious due to the impact of human activities on runoff. This conclusion is useful to peer studies on temporal variations of precipitation and runoff.
		2016 Vol. 35 (2): 28-36 [Abstract] ( 292 ) PDF (935 KB) ( 446 )

	37	Hydropower-ecologic benefits tradeoff analysis of cascade reservoir operation
		LI Dongnan, ZHAO Jianshi
		DOI: 10.11660/slfdxb.20160204
		Operation of cascade reservoirs involves multiple objectives including flood control, hydropower generation and ecosystem protection, and environmental flow demand is usually an important constraint if the major objective is hydropower generation. In this paper, we develop a cascade reservoir operation model for hydropower-environmental flow tradeoff analysis, via a case study of the Lancang River cascade, i.e., the Nuozadu, Jinghong and Ganlanba reservoirs. The results show that an obvious competitive relationship exists between maximization of hydropower generation and minimization of environmental flow alteration ? the more hydropower generation the more alteration of environmental inflow, and vice versa. This relationship is characterized by fairly strong nonlinearity. When alteration index ε is in the range of 0.3 to 0.4, a small change in ε can result in a significant change in hydropower generation, thus showing the importance role of this sensitive window in balance between hydropower generation and biological demand. Moreover, relative to the natural river flow, hydropower operation changes the frequencies of high flow pulses and small floods, which can be improved by an operation rule of artificial flood release.
		2016 Vol. 35 (2): 37-44 [Abstract] ( 286 ) PDF (1207 KB) ( 783 )

	45	Study on ecological operation and influence of power generation of Longtan-Yantan cascade reservoirs on Hongshui River
		CHEN Lihua, YE Ming, YE Jiang, DENG Fangfang
		DOI: 10.11660/slfdxb.20160205
		This paper presents a study on discharge scheduling of cascade reservoirs considering ecological base flow and flood flow to relieve or partly eliminate the negative impacts of dam construction activities on ecology, via a case study of the Longtan-Yantan cascade reservoirs on the Hongshui River using its monthly minimum ecological flow and ecological flow of monthly appropriate frequency and considering special flood peak demands by four major Chinese carps. According to the features of ecological demands, we have examined scheduling schemes for four types of constraints respectively, i.e. basic engineering constraint, minimum ecological flow constraint, monthly frequency-appropriate ecological flow constraint, and artificial peak-minimum ecological flow constraint. In the case of final constraint, three sub-schemes were adopted for three different magnitudes of artificial flood peak respectively. For the four schemes, losses in power generation benefit were compared and analyzed. Results show that a simple adoption of higher ecological flows reduces power generation benefit significantly and a scheduling scheme combining artificial peak with minimum ecological flow is able to compensate the water demand by the specific biology downstream.
		2016 Vol. 35 (2): 45-53 [Abstract] ( 269 ) PDF (587 KB) ( 431 )

	54	Modeling bedload transport along river meanders
		HE Li, CHEN Dong, JIA Yafei, ZHANG Yaoxin
		DOI: 10.11660/slfdxb.20160206
		Field observation and flume experiments indicate that bedload sediment in meanders takes two simultaneous motions, one part along the same bank, and the other part to the opposite bank. However, few quantitative studies can be found in the literature. The authors have simulated the flow and bedload transport in a 110° sine-generated meandering laboratorial flume by applying a two-dimensional depth-averaged model of unsteady flow and sediment transport, viz. CCHE2D. The calculations indicate two erosion zones of distinctively high scour intensity created in the process of bed deformation, one in the foreside of point bars at convex bank and the other near concave bank. In the early stage of bed deformation, nearly all the sediment eroded from these two zones are transported along the same banks, neither crossing the channel centerline nor moving to the opposite bank. After the equilibrium topography is reached, however, the main flow will gradually converge to the concave bank. Meanwhile, the moving paths of all particles are constrained to a concave bank-crossing bars-concave bank belt.
		2016 Vol. 35 (2): 54-60 [Abstract] ( 428 ) PDF (953 KB) ( 495 )

	61	Shape optimization and hydraulic characteristic analysis of stilling basins with backward step and diffusing walls
		LUO Yongqin
		DOI: 10.11660/slfdxb.20160207
		In this study, physical model tests and numerical simulations of 3-D turbulent flows have been used to optimize the shape of a stilling basin downstream of the tunnel spillway at the Guanyinyan hydropower station through a series of shape modification, and a satisfactory new shape with a backward step and diffusing walls was obtained. Detailed analysis on major hydraulic characteristics, fluctuating pressure in the slab joints, and slab uplift force, shows that protective works should focus on an area at the basin bottom in a distance of 60m behind the step. A significant correlation exists between surface fluctuating pressure and joint fluctuating pressure, and the max uplift force on a unit area of the slabs is 0.4-1.6 times the rms value of surface fluctuating pressure. The test results provide technical support to design and operation of stilling basins.
		2016 Vol. 35 (2): 61-66 [Abstract] ( 254 ) PDF (750 KB) ( 408 )

	67	Evaluation on sand abrasion to Baihetan hydraulic turbines
		LU Li, LIU Juan, YI Yanlin, LIU Gongmei
		DOI: 10.11660/slfdxb.20160208
		Evaluation on sand abrasion to turbines can provide data support to the selection of anti-abrasion materials and the decision on anti-abrasion strategies and overhaul plans for the turbines that will work at the Baihetan hydropower station. In this work, we have conducted an experimental study on the anti-abrasion performance and wear behavior of the materials possibly to be used for the turbines, and simulated the conditions of flow and sands passing through the turbines on the rotating disc test stand of an erosion test system for hydraulic machinery (ETS-HM). Different sand concentrations and flow velocities were adopted for the simulation tests, and resultant abrasion depth on the sample material surface due to sand impacting damage was measured after completion of the tests. Empirical formulae of abrasion rate for different materials were obtained by fitting the test data with a multivariable linear regression method. Applying these formulae, we estimated possible sand abrasion to the proto turbines for a certain period of operation, including runner, guide vane, and other major components of the flow passage. The estimation reveals that the most severe abrasion occurs on the end walls of guide vanes and at the blade outlet edges near lower runner ring. At these two locations, surface abrasion depth will increase up to 2.66 mm and 1.75 mm after ten years of operation respectively, which fall in the allowable range specified in the national standard GB/T 29403—2012.
		2016 Vol. 35 (2): 67-74 [Abstract] ( 278 ) PDF (897 KB) ( 461 )

	75	Study on influence of freeze-thaw cycles on shrinkage of weathered sand-improved expansive soil
		YANG Jun, LIU Shiyi, ZHANG Guodong
		DOI: 10.11660/slfdxb.20160209
		This paper presents a study on the qualitative and quantitative relationships of shrinkage characteristics of weathered sand-improved expansive soil versus weathered sand content and the number of freeze-thaw cycles. The expansive soil samples of weathered sand contents of 0, 10%, 20%, 30%, 40%, and 50%, were tested with a contractometer to measure their shrinkage parameters at cycling times of 0, 1, 3, 6, 9 and 12. Test results showed that for soil samples of the same sand content, an increase in the number of cycles results in a decrease in linear shrinkage ratio, volume shrinkage ratio, contraction coefficient, and shrinkage limit. As the sand content is increased at a fixed number of cycles, shrinkage limit is increased while all the other three parameters decreases. At a fixed sand content, the relationship of linear shrinkage versus the number of freeze-thaw cycles is a power function, while the relationship of volume shrinkage versus freeze-thaw cycles is quadratic.
		2016 Vol. 35 (2): 75-81 [Abstract] ( 286 ) PDF (469 KB) ( 351 )

	82	Water retaining risk dynamic control model for high rock-fill dams under construction in flood season
		LIU Lian, HU Zhigen
		DOI: 10.11660/slfdxb.20160210
		Risk control of high rock-fill dam construction in flood season can be achieved by appropriate dam filling schedule. This study has introduced an adaptive control theory to the development of a water retaining risk dynamic control model and the design of control schemes on high rock-fill dam construction. The flood hydrograph is simulated by a first-order autoregressive time series model using measured flood series, and real-time risk can be calculated. Then, the rock-fill dam filling progress is adjusted dynamically by limiting the real-time risk to the accepted risk range, which can be taken as a desired trajectory on account of the risk preference of decision-maker. By such a dynamic adjustment, the real-time risk as entire trajectory will aim to track this desired trajectory to maximum coincidence. Application to a practical case shows that this dynamic control model can effectively control the risk to the expected target and explain why the maximum cost that the decision-maker is willing to pay tends to be stable in late flood season. This study provides support for the progress control and flood protection decision making.
		2016 Vol. 35 (2): 82-89 [Abstract] ( 339 ) PDF (440 KB) ( 509 )

	90	Study on prototype experiment of radial gates at Shuhe hydropower station
		HU Musheng, YANG Zhize, ZHANG Bing, GENG Honglei, XIAO Xiaohui
		DOI: 10.11660/slfdxb.20160211
		As hydraulic engineering technology is developing in China, increasingly more large-size radial gates come into use and the technologies of radial gate prototype tests must meet higher requirements. At present stage, no specialized norms for the prototype test technologies of hydraulic metal structures are available yet in China or overseas. This paper presents a comprehensive technical solution to the prototype experiment of radial gates based on analysis of their characteristics. In a case study of radial gate No.2 at the Shuhe hydropower station, we have adopted advanced technologies of instrumentation and data analysis and conducted a comprehensive evaluation and analysis on its characteristic parameters of working conditions, such as stress in main structures, deformation, dynamic characteristics, vibration responses, and operation forces. The results reveal incipient faults in gate operation ? gate arms laterally subjected to a large bending moment, unfavorable interaction of dynamic water load with low-frequency zones behind the gate and piers, and an instantaneous initial lifting force beyond the hydraulic hoist capacity. The findings are useful to ensure engineering safety and improve designs of radial gates.
		2016 Vol. 35 (2): 90-100 [Abstract] ( 307 ) PDF (2950 KB) ( 654 )

	101	Tangential interaction mechanism between very early-age concrete and structures
		CUI Wei, YANG Nana, SONG Huifang
		DOI: 10.11660/slfdxb.20160212
		Interaction mechanism between very early-age concrete and structures is very complicated, as it is effected by composition of concrete, behavior of structure surface, setting time of concrete, demoulding velocity, and lubricating condition. In this study, we have designed and conducted model tests for the measurements of tangential force at the interface of concrete and formwork in different conditions and analyzed the test data. The experimental results showed that the tangential force had two components, i.e. frictional force and bonding force, and at initial stage it largely came from the bonding effect of cement mortar. Its correlation with time became stronger as water-cement ratio decreased, while along with concrete setting, it increased significantly and the correlation also slightly increased. Demoulding velocity had little influence on this force, while lubricant could help to decrease it at initial stage and keep it steady in mid-late stages. To interpret the experimental results, we developed a micromechanical model for the interaction mechanism between concrete and structures.
		2016 Vol. 35 (2): 101-108 [Abstract] ( 252 ) PDF (693 KB) ( 416 )

	109	Experimental study on fracture toughness of concrete with different moisture contents
		ZHANG Guohui, LI Zongli, NIE Kangyi, LIU Minghui
		DOI: 10.11660/slfdxb.20160213
		Concrete structures are often subjected to conditions of different moisture contents, and the fracture toughness of concrete is affected significantly by its humidity. In this paper, we have conducted a systematic experiment study on concrete with different moisture contents. Concrete specimens C15, C20 and C30 were dried in an electric thermostatic drying oven until they had reached a completely dry state, and then they were immersed in water for 3, 10, 24, 48, 72, 120 and 240 h so as to achieve different moisture contents. Finally, three-point bending tests were conducted to measure their fracture toughness, and through analysis of the test data, prediction formulae for the relationship of fracture toughness versus moisture content were formulated. The results demonstrated an evident influence of concrete moisture content on fracture toughness, which took a significant decreasing trend with increasing moisture content and was decreased by 57% at saturated content from the value in completely dry condition. The P–COMD relation curves from the three-point bending tests can be divided into three stages, i.e. linear elastic deformation, steady crack extension, and unstable crack extension. As moisture content increased, the elastic stage gradually shortened, the steady extension stage lengthened, and the descending trend in the unstable stage became milder. Moreover, at a greater moisture content, the crack mouth opening displacement and the load-point deflection at the peak load condition were smaller, showing a lower deformability of concrete or its fracture toughness weakened.
		2016 Vol. 35 (2): 109-116 [Abstract] ( 299 ) PDF (1654 KB) ( 450 )

	117	Study on modal identification of powerhouse structures with closely spaced modes
		WANG Haijun, ZHENG Hanci, ZHOU Jifang
		DOI: 10.11660/slfdxb.20160214
		This paper presents a combined method for modal identification of hydropower house structures with closely spaced modes, which can reduce mode intensity and improve the precision of modal separation by combining a reverse attenuation index window with wavelet packet frequency division. After modal separation of a signal, a random decrement technique and spare time domain method are used to identify its modal parameters. We have applied this combined method in a case study of the signals of in-situ vibrations in a large-size hydropower house structure with closely spaced modes, and compared with finite element analysis results. The calculations showed that the identification results were in good agreement with the finite element calculations and the damping ratios identified were in the normal range of reinforced concrete structures.
		2016 Vol. 35 (2): 117-223 [Abstract] ( 254 ) PDF (427 KB) ( 516 )

	124	Simulation of dust migration at working faces during drill-blasting construction of underground hydropower houses
		HONG Kun, LIU Zhen, WANG Xiaoling, ZHU Zebiao
		DOI: 10.11660/slfdxb.20160215
		Ventilation during construction of underground hydropower houses has serious effects on construction efficiency and safety. This paper describes a 3D unsteady Euler two-phase turbulence model considering the effect of gas-solid interaction force, aiming at difficulties in dust discharge caused by complex structure with inter-connected tunnels. We have applied this model in a case study of the ventilation in drill-blasting construction for an underground hydropower house in China and analyzed the airflow structure and dust migration. The analysis reveals a relationship of dust distribution versus ventilation time and an eddy zone that forms near the working face and hinders dust discharge. A comparison of two different working faces shows similar airflow structures near them. For the ventilation scheme studied, dust concentration in the main powerhouse is significantly reduced with a longer ventilating operation, and it can meet the safety standard if ventilating operation takes roughly 1300s. The peak of dust concentration migrates continuously toward the tunnel outlet and its amplitude decreases with time.
		2016 Vol. 35 (2): 124-130 [Abstract] ( 244 ) PDF (2069 KB) ( 459 )