Journal of Hydroelectric Engineering

水力发电学报

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2016 Vol. 35, No. 7 Published: 2016-07-25

	1	Developments in seismic safety evaluation methods and aseismic measures for high rockfill dams
		KONG Xianjing, ZOU Degao, LIU Jingmao
		DOI: 10.11660/slfdxb.20160701
		In this paper, the recent developments in seismic safety evaluation and aseismic measures for high rockfill dams were reviewed, including advanced constitutive models, dam-foundation-water dynamic interaction, high-performance non-linear dynamic FEM software, numerical simulation of failure process, and aseismic measures of concrete slab, and etc. After that, some future research trends on earthquake-resistance analysis of high rockfill dams were discussed, such as the seismic response analysis, mechanical properties and constitutive relations of rockfill, computing technology, and seismic safety evaluation method.
		2016 Vol. 35 (7): 1-14 [Abstract] ( 324 ) PDF (1585 KB) ( 1344 )

	15	Discrete element modeling of microwave-induced rock damage at different discontinuity scales
		TANG Yang, XU Guobin, SUN Liying, XU Linyu, DU Chenqu
		DOI: 10.11660/slfdxb.20160702
		In simulation of microwave-induced rock damage, various achievements have been made in recent years, but most of them are based on the theory of continuous medium. This study has examined two-phase materials composed of quartz and plagioclase components under different discontinuity scales and different levels of exposure to microwave radiation, using the discrete element method of a particle flow code PFC2D. The results indicated that this method was successful in simulation of rock cracking process: initiation, development and coalescence of the cracks. And the micro-cracks were initiated at the boundary of high absorption phase, i.e. quartz crystals, expanding outward around and extending into the plagioclase material. Finally, a network of radial tensile cracks was mobilized. The simulated patterns of cracks agree well with those observed in experimental tests of microwave radiation. The results of the present study provide a new approach of numerical simulation to microwave-induced damage using the discrete element method.
		2016 Vol. 35 (7): 15-22 [Abstract] ( 457 ) PDF (1386 KB) ( 905 )

	23	Optimal operation of cascade reservoir hydropower generation based on precipitation forecasts
		XU Wei, PENG Yong
		DOI: 10.11660/slfdxb.20160703
		Efficiency and stability of cascade reservoirs in hydropower generation can be improved by using the data of quantitative precipitation forecasts (QPFs), but the improvements are affected by high uncertainties in QPFs. To enhance the usefulness of inflow forecasts resorting to QPFs, precipitation forecasts were divided into several levels and the probability distributions of the actual precipitation at different levels analyzed in this study. Then, a parameter-simulation-optimization (PSO) model and hedging rule curves (HRCs) were used to construct a PSO-HRCs model for hydropower operation, which fuses the reservoir storage and inflow as a single variable and thus makes the solution computationally tractable. Based on the probability distributions, the PSO-HRCs model can generate precipitation, inflow and operation policy for different probabilities, and hence the corresponding risks and losses in water releasing and storing schemes can be evaluated. This paper presents a case study of the Hun River cascade reservoir system that used the QPFs of ten days lead time, issued by the Global Forecast System (GFS), the U.S. National Centers for Environmental Prediction, to analyze and compare the efficiency and stability of hydropower generation with different probabilities.
		2016 Vol. 35 (7): 23-33 [Abstract] ( 387 ) PDF (598 KB) ( 487 )

	34	Analysis of hydrological regime changes in the midstream Han River using range of variability approach
		ZHANG Sa, BAN Xuan, HUANG Qiang, LIU Dengfeng
		DOI: 10.11660/slfdxb.20160704
		Hydrological regime plays a crucial role in river ecologic systems. Analysis on the effects of dams on the regime of a river using the range of variability approach (RVA) can provide key information for protection of its ecological integrity. In this study, this approach was applied to hydrological regime changes at the Xiangyang and Yicheng stations on the midstream Han River in the period of 1952-2013. We selected the year 1974 as the change point and divide for analysis of hydrological deviation rate and hydrological change, and analyzed the midstream hydrological changes using five sets of hydrological indexes: runoff level, frequency, duration, time of occurrence, and distribution of change rate. The results show that under the control of Danjiangkou dam that started in 1974, the water levels at these two stations were generally lower, and the change in the water level was most significant at Xiangyang while mild at Yicheng. This study would be useful for evaluation of the downstream of Han River and water resources management.
		2016 Vol. 35 (7): 34-43 [Abstract] ( 372 ) PDF (2315 KB) ( 855 )

	44	Variation analysis of lowest navigable water levels in major rivers in Guangdong province
		XU Qiangqiang, XIE Ping, LI Peiyue, WU Ziyi, ZHAO Jiangyan
		DOI: 10.11660/slfdxb.20160705
		Due to intense interference from climate change and human activities in recent years, the traditional consistent design methods for calculation of design lowest navigable water level no longer meet the demands. In this study, a hydrological variation diagnosis system has been applied to analysis of annual mean water level series for four major rivers in Guangdong: East River, West River, North River, and Hanjiang River. Results show that moderate or strong variations in river level have been detected at the outlet control stations of these rivers. Then, we applied a synthetic duration curve method to the series of river level under the changing environments, using two separate daily water level sub-series segmented at the change point, and compared the calculations of design lowest navigable water level based on the pro- and post-changepoint sub-series and the whole series. The results indicate that climate change has caused an increase of more than 30% in navigation depth at the Chaoan station while a decrease of more than 30% at other stations. A frequency guarantee rate method was also adopted to diagnose the annual series of characteristic navigation levels, and this revealed change points of different forms and degrees in these series corresponding to different guarantee rates. Thus, our results show the existing problems with the two traditional methods in calculation of inconsistent water level series.
		2016 Vol. 35 (7): 44-54 [Abstract] ( 307 ) PDF (973 KB) ( 723 )

	55	Impact of climate change and human activities on runoff variation in Beiluo River basin
		ZHANG Lianpeng, LIU Dengfeng, ZHANG Hongxue, HUANG Qiang, MENG Xianmeng
		DOI: 10.11660/slfdxb.20160706
		Studies on the attribution of runoff variation under climate change and human activities are valuable to understanding runoff change. This paper analyzes the quantitative contribution of climate change and human activities to runoff variation, using the Budyko assumption and TOPMODEL with application to a case study of the Beiluo River basin of the Wei River. We have examined 25 scenarios of temperature and precipitation changes in the possible range of climate changes, and analyzed the influence of all these scenarios on the runoff. Simulation results show that historic precipitation and runoff took a decreasing tendency while temperature had a rising trend and both temperature rising and precipitation decreasing made contribution to runoff change. But human activities were the major cause for runoff decreasing over the last 50 years and this had a contribution rate up to 58.9% and 65.2% by the two methods respectively. Under different scenarios, the variation in monthly runoff shows a wide range and the influence of precipitation change is stronger than that of temperature change, indicating precipitation change as a major factor of the future variation in water resources.
		2016 Vol. 35 (7): 55-66 [Abstract] ( 533 ) PDF (965 KB) ( 1101 )

	67	Prediction model for head loss in drip irrigation laterals based on dimensional analysis
		DING Falong, WANG Wen’e, HU Xiaotao
		DOI: 10.11660/slfdxb.20160707
		The effects of pipe length, emitter spacing and operating pressure of drip irrigation laterals on their total head loss were studied in this work using laboratory tests. The results showed that the total head loss was increased with inlet pressure or pipe length, but decreased with emitter spacing. Of these three factors, the variation in head losses caused by inlet pressure took the mildest trend. In the complicated calculation procedure of a drip lateral, six physical parameters were considered: mean inlet velocity υ0, drip lateral diameter D, pipe length L, emitter spacing s, kinematic viscosity of water ν, and gravitational acceleration g. We have developed a multiple regression model using four dimensionless variables of υ0D/ν，υ02/gD，LD/s2 and ε (contraction ratio of the emitter installation section) for prediction of head loss. By this model, we derived a formula for calculation of the energy loss and formulated a method to determine the pressure at any location along the drip lateral through analysis of the corresponding energy gradient. The predicted values agree well with the experimental measurements. Our results would help hydraulic design and evaluation of drip irrigation systems.
		2016 Vol. 35 (7): 67-74 [Abstract] ( 285 ) PDF (1035 KB) ( 471 )

	75	Golden mussel biofouling and its prevention in pumped-storage power plants
		XU Mengzhen, LI Wei, YU Dandan, QIANG Jie, HU Zhiping, YAO Guoyou
		DOI: 10.11660/slfdxb.20160708
		Pumped-storage power plants (PSPs) aim to solve the conflict between power supply and demand at the peak and trough of power consuming, ensuring grid safety, economic growth, and stable production. Invasion and biofouling of golden mussel (Limnoperna fortunei) in PSPs, however, is attracting wide public attention because in recent years the biofouling has caused severe problems in the operation of PSPs. The specific operation mode of PSPs is commonly taken as the major cause for such biofouling in water intakes and tunnels. A PSP releases water stored in its upper reservoir to the lower one when it generates power during peak power-consuming hours, and pumps water back to its upper reservoir during low demand hours. During water releasing and pumping, golden mussel veligers are stirred up from the reservoir bed and transported into the intakes, tunnels, and the other structures reachable by the flow; then they are settled down on the walls of all the structures they have touched, causing biofouling, structure corrosion, and even pipe clog. Particularly, the small tubes of the PSP cooling water system are under a high risk of being clogged, often causing a shutdown accident. This study presents an overview on the latest advances in preventive measures against golden mussel biofouling in PSPs based on previous studies, overseas experiences, and our own experiences. For large-scale water-intake pipes of PSPs, the risk of clogging is low and therefore the basic strategy should focus on pipe wall resistance to the corrosion. Certain environment-friendly, economically-desirable coating materials, e.g. SK-Polyurea and SK-Epoxy YEC, which have been shown very effective in terms of biofouling resistance and pipe-wall durability, are recommended according to our experimental study. For small-scale PSP cooling water systems, we propose a control device of the veliger density in water flow that integrates the measures of attachment-attracting, settling, and veliger killing and thus effectively reduces biofouling risk.
		2016 Vol. 35 (7): 75-83 [Abstract] ( 530 ) PDF (2021 KB) ( 1102 )

	84	Numerical simulation of velocity distributions in aeration tanks influenced by different aeration tube arrangements
		LIU Yuling, BAI Ge, SHAO Shipeng, WEI Wenli
		DOI: 10.11660/slfdxb.20160709
		Aeration tank is a core device in treatment of activated sludge waste water, and understanding its flow structure is crucial to improvement of its oxygen transfer and sewage treatment. An Euler-Euler multiphase flow model combined with a standard k-ε turbulence model (FLUENT 6.3) has been used in this study to simulate a typical plug-flow aeration tank. We analyzed the velocity distributions for two cases of different aeration tube installation, located at the tank centerplane and near a tank wall, and compared their velocity uniformity coefficients and velocity differences between the gas and liquid phases at characteristic cross sections. Our findings are that in the near-wall case the flow is more uniform and the velocity difference of two phases smaller, which is a favorable condition for flow mixing in the tank. In this case, the distribution of gas-phase volume fraction over the central longitudinal section at different time is more uniform. Thus, aeration tube installed near a tank wall is a case where both the flow structure and gas content are beneficial to oxygen and mass transfer between the two phases, leading to a higher rate of oxygen utilization and lower energy consumption. The results are useful for optimization of waste water treatment designs.
		2016 Vol. 35 (7): 84-90 [Abstract] ( 517 ) PDF (848 KB) ( 1018 )

	91	Effect of reflux hole on internal flow characteristics of outer recirculation self-priming centrifugal pumps
		MOU Jiegang, WU Zhenxing, ZHOU Peijian, WU Denghao, GU Yunqing, ZHENG Shuihua
		DOI: 10.11660/slfdxb.20160710
		Due to its special role in adjusting internal flow structure, a reflux hole is a key device that affects the performance of outer recirculation self-priming centrifugal pumps. To examine its effects, the internal flows have been numerically simulated in this study for an efficient self-priming sewage pump of ZW type with a reflux hole connecting the gas-liquid separation chamber to the volute. Results show that this reflux hole had a significant effect on the internal flow and pump performance. It produced a circular flow and a considerable increase in head loss and hence reduced pumping lift significantly. As the pump flow rate was varied, the pressure distribution at the chamber and volute sides of the hole was changed in a regular way, and the flow patterns near the hole inlet and outlet also changed. A change in the hole cross-sectional area caused a change in the pressure drop from the hole inlet to outlet and a change in the hole flow rate, thus modifying the external characteristics of the pump.
		2016 Vol. 35 (7): 91-98 [Abstract] ( 429 ) PDF (3288 KB) ( 936 )

	99	Experimental study on power stabilization control of intermittent wave energy generators
		SONG Ruiyin, LI Yue, CHEN Junhua, LIN Zuan, CHENG Shaoke
		DOI: 10.11660/slfdxb.20160711
		This paper presents a new intermittent wave energy generator (WEG) with a hydraulic energy storage accumulator that converts unstable wave energy into stable output power in electrical power generation, and describes its components and working principle along with a real-time control method for stabilizing the output power based on experimental test database. Theoretical models were constructed for the relationship of load versus working pressure and the relationship of hydraulic motor pressure drop versus opening ratio of the proportional flow valve. The latter relationship was verified by experimental data collected using LabVIEW, and a control curve of the opening ratio was used to stabilize the flow rate of hydraulic motor. Experimental results show that the output power of generators can be maintained stable within a certain range and the new WEG, when combined with hydraulic energy storage accumulator and real-time control based on experimental test database, is an effective device for generation of stable and smooth output power.
		2016 Vol. 35 (7): 99-105 [Abstract] ( 316 ) PDF (1076 KB) ( 1008 )

	106	Unsteady cavitation characteristics of mixed-flow pump impeller operating in multi-conditions
		LI Jingyue, LAI Xide, ZHU li, ZHAO Xi, LUO Li
		DOI: 10.11660/slfdxb.20160712
		Cavitation is one of the key factors that reduce hydraulic efficiency and service life of pump impeller. This study has conducted full-passage CFD simulations of the unsteady gas-liquid two-phase flows in a mixed-flow pumping system to optimize the impeller and improve the pump performance against cavitation, focusing on unsteady cavitation characteristics at operating flow rate in the range of 0.5Q ~1.0Q, spatial distribution and time variation of cavitation, and effects of different net positive suction head (NPSH) on cavitation volume fraction. The results show that cavitation inception occurs at the inlet edges of blade suction sides and cavitation of higher volume fraction gathers near the inlet edges of blades. In the conditions of NPSH lower than a certain threshold, impeller channels will be dominated by cavitation. As the operating flow rate is reduced, the NPSH threshold is decreasing, but serious cavitation is developing faster and cavity content is increasing exponentially.
		2016 Vol. 35 (7): 106-111 [Abstract] ( 345 ) PDF (1077 KB) ( 810 )

	112	Cracking resistance behaviors of ultra-high volume fly ash dam concrete at early age
		ZHAO Zhifang, LI Chao, ZHANG Zhenyu, WANG Weilun, ZHOU Hougui
		DOI: 10.11660/slfdxb.20160713
		This study investigates cracking resistance behaviors of ultra-high volume fly ash conventional dam concrete (UHVFACDC) at early age using a temperature-stress testing machine (TSTM), with a comprehensive consideration of temperature history, constraint, deformation and stress of concrete from the prospective of wholism to overcome the deficiency in the traditional methods of thermal cracking property evaluation of concrete at early age. The experimental results show that in comparison with the reference concrete, this fly ash concrete has lower hydration temperature rise, and cracking temperature and its cracking temperature drop is larger. And during hardening, it manifests a smaller coefficient of thermal expansion and a higher degree of tensile creep. All this indicates that UHVFACDC of great early-age cracking resistance is a promising type of green high-performance dam concrete.
		2016 Vol. 35 (7): 112-119 [Abstract] ( 428 ) PDF (546 KB) ( 1070 )

	120	Experimental study on operation characteristics of oscillating-buoy wave energy converters
		YANG Cen, ZHANG Yongliang
		DOI: 10.11660/slfdxb.20160714
		Oscillating-buoy is a major type of wave energy converters (WECs) that convert wave energy into hydraulic or electric energy, and its performance significantly affects its availability and efficiency of wave energy utilization. This paper presents an experimental study on the operation characteristics of oscillating-buoy wave energy converters, and analyzes the effect of nonlinear external load, geometric arrangement and mooring system on dynamic responses, flow rate and conversion efficiency. The results show that for a fixed size WEC, the maximum efficiency can be achieved at its optimal wave frequency and external load. The optimal geometric arrangement depends on external load. For large external loads, a single buoy WEC has an efficiency greater than other geometric arrangements. The efficiency of a two-buoy WEC is increased when fewer mooring constraints are imposed.
		2016 Vol. 35 (7): 120-126 [Abstract] ( 370 ) PDF (671 KB) ( 985 )