Journal of Hydroelectric Engineering

水力发电学报

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2022 Vol. 41, No. 2 Published: 2022-02-25

	1	Mechanism and harmony regulation of human-water relationship in Yellow River basin ^Hot!
		ZUO Qiting , LI Jiawei, YU Lei
		DOI: 10.11660/slfdxb.20220201
		Human-water relationship is complex and involves many elements. It is important to find an effective approach for harmonious regulation of the existing conflicts on the basis of the mechanism hidden in the relationship. Using a case analysis of the Yellow River basin, this paper elucidates the complexity of human-water relationship from three aspects, complexity in the human system and the water system, complexity in their coupling, and complexity in their interaction. We examine the interaction process in human-water relationship, and reveal its mechanism based on the interaction of these two components; then, we summarize the issues in the existing human-water relationship observed in the case basin, and present an new idea － using harmonious regulation to improve such relationship. The results of two case studies, “Yellow River water distribution” and “harmony equilibrium between water resources and economy-society development”, show that facing such a complex relationship involved in this basin, we can adopt the theory and method of harmonious control to achieve an optimized water distribution plan that improves the level of its regional harmony and its human-water relationship, thus proving the approach is valid and useful.
		2022 Vol. 41 (2): 1-8 [Abstract] ( 192 ) PDF (2193 KB) ( 630 )

	9	Propagation threshold of meteorological drought to different levels of hydrological drought. A case study of Qinhe River basin
		LIU Yongqiang, HUANG Shengzhi, GUO Yi, LIU Yongjia, LI Ziyan, HUANG Qiang
		DOI: 10.11660/slfdxb.20220202
		A systematic quantification of the thresholds for the propagation from meteorological drought to different levels of hydrological drought is useful in guiding the early warning and delicacy management of hydrological drought. In this paper, a standardized precipitation index and a standardized runoff index are used to characterize meteorological drought and hydrological drought, respectively, for the Qinhe River basin of Loess Plateau; the run theory is applied to identify drought events, and merge or reject drought events to match both types of drought events. Then, Bayesian networks combined with Copula functions are used to construct models to solve for the propagation thresholds. Results show that when the level of hydrological drought is raised, the threshold is elevated and the intensity of a meteorological drought is weakened in the propagation. For the Qinhe River basin, the duration thresholds of meteorological droughts are 12.8, 21.8 and 30.9 months for triggering moderate, severe and extreme hydrological droughts, respectively, corresponding to the intensity thresholds of 14.2, 22.4, and 30.0, respectively, and its drought tolerance ability is related to the basin meteorological and underlying surface conditions.
		2022 Vol. 41 (2): 9-19 [Abstract] ( 376 ) PDF (2519 KB) ( 754 )

	20	Long-term optimal operation atlas of reservoirs considering remaining benefits and its application
		AI Xueshan, MU Zhenyu, GUO Jiajun, CHEN Senlin, YANG Baiyin, GAO Zhiyun
		DOI: 10.11660/slfdxb.20220203
		The optimal operation chart of a hydropower station is a useful tool to guide its optimal operation, and the remaining benefit is a key factor restricting the effect of an operation scheme. Based on the information of historical flows at the dam site, this paper calculates the long-term remaining benefit for the reservoir storage at year end. And, from the magnitude and frequency of the inflows in each period, we calculate optimal expected benefits for different reservoir water stages at the beginning of each period in a reverse order starting from year end, using the dynamic programming method. Then, optimal decision charts are made for different typical inflow conditions in each period based on the different reservoir stages at its beginning, so that the charts of all the periods can serve as an optimal operation atlas for long-term power generation of the reservoir. A case study of the Nam Ou VII hydropower station in Laos shows this new method offers long-term operation schemes that are simple and on clear principles, achieving a benefit of 1.03% higher than traditional operation and 0.87% higher than function-based operation. This demonstrates that for long-term optimal operation of reservoirs, it is of great significance to make use of historical runoffs and flow predictions and to consider the impact of reservoir decision on remaining benefits.
		2022 Vol. 41 (2): 20-30 [Abstract] ( 149 ) PDF (926 KB) ( 460 )

	31	Study on multi-objective cooperative decision making of flood control water levels of reservoirs
		LI Xiaoying, ZHANG Yan, TONG Zechun
		DOI: 10.11660/slfdxb.20220204
		Controlling the flood limit water levels of a reservoir by stages is an effective approach to raising flood water utilization rates. In this study, by dividing flood season into different stages using the circular distribution method, we determine benefit index sets and risk index sets for a staged control of the limit water levels, and construct a multi-objective collaborative decision-making model that can coordinate conflicts between risk and benefit. Then, we calculate a utility function for each index set, determine a payoff function and a reachable utility set, and solve for the ideal Nash negotiation solution using a nonlinear programming method. And by the theory of pattern recognition, an optimal scheme can be determined; a certain preference for risk or benefit can be realized using the current situation point as the basis for benefit-risk negotiation decision and then adjusting this point. In a case study of the Xianghongdian Reservoir, we adopt a condition of risk and benefit valued equally, and obtain the optimal flood control levels of 126.5 m and 127.0 m for pre-flood and post-flood stages, respectively. It shows that by raising the risk at the corresponding risk status point, a risk preference in pre-flood stage can be realized, resulting in a greater value of the risk payoff function and thus a lower optimal limit water level. Similarly, by raising the benefit at this point, a preference for benefit in post-flood season can be realized with a greater value of the benefit payoff function and a higher optimal limit water level.
		2022 Vol. 41 (2): 31-42 [Abstract] ( 155 ) PDF (681 KB) ( 981 )

	43	Analysis of minor head losses in manhole of drainage system
		LIU Yan, XIA Junqiang, ZHANG Hao, ZHOU Meirong, DONG Boliang
		DOI: 10.11660/slfdxb.20220205
		Besides frictional head losses in an urban drainage system, its minor head losses are significant under certain conditions and cannot be ignored in the design. Based on the model experiment of a sewer pipe system and its manhole, the minor loss coefficient of the manhole has been calculated for different working conditions, and an analysis of the calculated results is also presented. These results show that the flow ratio of the main pipe to branch pipe is a major factor that has a great effect on minor loss coefficients, and that with an increasing flow ratio, the increase in these coefficients can reach up to 1.2. The manhole shape and the angle between the main and branch pipes ranks second, two minor factors causing a minor loss coefficient change of less than 0.2 each. The downstream water depth and discharge of the outlet pipe has little impact on the coefficients; a comparative analysis of our experimental data with previous studies shows installing symmetric branch pipes reduces the minor losses. The results help an in-depth understanding of the variations in the manhole minor losses for optimizing urban drainage system design and improving practical urban flood management.
		2022 Vol. 41 (2): 43-54 [Abstract] ( 280 ) PDF (3852 KB) ( 336 )

	55	Numerical inversion of creeping vibration of emergency gates and its influencing factors
		WANG Yanzhao, XU Guobin, LIU Fang
		DOI: 10.11660/slfdxb.20220206
		To study the phenomenon and influencing factors of the creeping vibration of an emergency gate, this study examines the vibration characteristics and determines the vibration type based on the prototype gate vibration response during gate closing operation. By analogy with dry friction self-excited vibration in tribology, we develop a mathematical model of closing stage vibration to invert the gate vibration response, and examine the influences of closing speed, gate mass, friction coefficient on the vibration behavior. The results show the creeping vibration of the gate is a special type of self-excited vibration with its amplitude growing gradually during gate closing. Transformation between dynamic and static friction of the gate and its tracks is the fundamental cause of creeping vibration, and the intensity of vibration response is proportional to panel water pressure and the difference between dynamic and static friction coefficients. Gate closing speed imposes great influence on gate vibration; a threshold closing speed, depending on the static friction coefficient, has been observed for judging the creeping vibration mode of the gate. Gate mass affects the initial deformation of steel ropes and the closing time, and thus influences the creeping vibration. The closure of the gate increases the length of steel ropes and decreases the system stiffness, leading to an increase in amplitude and period of vibration.
		2022 Vol. 41 (2): 55-62 [Abstract] ( 108 ) PDF (2009 KB) ( 290 )

	63	In-plant economical operation of hydropower stations considering graded hydro-unit vibration zones
		LIU Rui, WANG Yimin, CHANG Jianxia, MA Changhong, GU Qi, BA Gui, MA Dahai, DANZENG Jinmei
		DOI: 10.11660/slfdxb.20220207
		Distinguishing hydro-unit vibration zones is the core that affects safe and economical operation of a hydropower plant. This study focuses on the difference in hydro-unit vibration intensity under different loads and adopts an idea of graded vibration zones, i.e. dividing the vibration zone into an operation-forbidden zone, an unrecommended zone, and a stable zone. Then, we construct an in-plant economical operation model of hydropower stations taking these graded zones into account, and solve it using a particle swarm algorithm. Application to the Zangmu hydropower station shows that in comparison to a single operation-forbidden zone, this new method predicts an increase as low as 0.69% in the water consumption by the plant operated in the allocated output mode, while keeping unit operation more stable with lower vibration. Thus, adoption of graded vibration zones improves model applicability to the real conditions of a hydropower station and helps find operation schemes that are more economical.
		2022 Vol. 41 (2): 63-71 [Abstract] ( 169 ) PDF (1335 KB) ( 377 )

	72	Correction to unbalanced moment calculations of turbine runners using stress bar method
		DU Zhipeng, WU Jianjie, LIU Nian, YIN Zhongkai
		DOI: 10.11660/slfdxb.20220208
		Residual unbalanced moment is a key index to evaluate the build quality of turbine runners. In the runner static balance system based on the stress bar method, the unbalanced moment calculated using the balance equation often deviates significantly from the real counterweight moment, which affects the calculation of the real residual unbalanced moment. Through analysis of the balance state of a real balance system, this paper first points out the bending deformation of the stress bar’s surveying rod will cause its bending moment to deviate from the real unbalanced moment of the runner. Then, considering engineering application cases, we examine the preconditions of concentrated deformation and small deformation, and derive a formula to correct the difference between the stress bar bending moment and the real unbalanced moment of the runner for the case of the stress bar with its fixed end lower or higher than the runner centroid. Finally, a case study proves our correction formula can reduce calculation errors effectively and help improve the build quality and key performance of turbine runners.
		2022 Vol. 41 (2): 72-78 [Abstract] ( 115 ) PDF (1609 KB) ( 181 )

	79	Multi-scale experiment of mechanical property degradation of a laterite soil under dry-wet cycling
		YUAN Zhihui, TANG Chun, YANG Puji, GAN Jianjun
		DOI: 10.11660/slfdxb.20220209
		To investigate the multi-scale effect of degrading mechanical properties of laterite soils under dry-wet cycling, we conducted mercury intrusion tests, scanning electron microscope tests, micro-fracture tests, and triaxial compression tests, focusing on analysis of the damage to the micro-meso structure of a remolded laterite soil and its deterioration of macroscopic mechanical properties. And the multi-scale mechanism of soil mechanical property degradation is explored. Results show that: (1) the micro-structure of remolded laterite is damaged by dry-wet cycles obviously: its gradation becomes slightly denser and most of the particles are modified closer to the spherical shape. The frequency of particle orientation is modified, but it is overall isotropic with a dominant orientation only locally. The probability distribution index of particle area increases and transforms to that of smaller particles. The total pore volume increases and small pores transform into medium and large ones. This increase is involved in pore transformation, serving as the main source of more medium and large pores; (2) Under dry-wet cycling, the evolution of remolded laterite meso-cracks experiences three stages: crack initiation of humidification, development with the cycling, and later stableness. The development of fracture rate and fracture width mainly occurs in the initial five cycles and is stabilized in the late stage; (3) Owing to the action of dry-wet cycles, the shear strength of remolded laterite degrades significantly. The cohesion decreases in an inverse ￠S￠ type, which occurs in the initial five cycles and tends to be stable later. The internal friction angle decreases linearly to a small extent. Based on the results above, the multi-scale mechanism of remolded laterite mechanical properties deterioration can be summarized. The expansion potential of total pore volume, matrix potential of pore expansion and penetration weakening, cementation strength weakened by dissolution of cement material, and particle structure modified by repeated water migration under the action of dry-wet cycling － all these factors together cause damage to soil microstructure and then make the micro-cracks expand into meso-cracks, resulting in degraded soil integrity and deteriorated macroscopic mechanical properties.
		2022 Vol. 41 (2): 79-91 [Abstract] ( 124 ) PDF (2937 KB) ( 345 )

	92	Best-fit maturity method for predicting fracture properties of concrete
		MI Zhengxiang, LI Qingbin, HU Yu
		DOI: 10.11660/slfdxb.20220210
		To predict the fracture properties of concrete exposed to different temperatures, variations in activation energy with age are examined for different fracture parameters. A best-fit maturity method for determining the fracture properties is developed and verified using laboratory experimental data. The effect of activation energy and datum temperature on the prediction accuracy of fracture parameters is discussed. The results show that activation energy differs between different fracture properties and varies at different development levels of a given fracture parameter, and its values determined using different temperature ranges are unequal. The method developed in this study can accurately predict the fracture properties of concrete. The optimal activation energy (or datum temperature) varies with temperature ranges and fracture properties. No constant optimal activation energy (or datum temperature) can be found for prediction of the fracture properties of concrete at different temperatures.
		2022 Vol. 41 (2): 92-101 [Abstract] ( 120 ) PDF (614 KB) ( 411 )

	102	Prediction of aqueduct deformation based on time series decomposition and machine learning
		ZHAO Pengyuan, WANG Renchao, MA Yuming
		DOI: 10.11660/slfdxb.20220211
		Monitoring the safety of aqueducts is of great significance to ensure the stability of long-distance water delivery in the South-to-North Water Diversion Project. This paper develops a combined prediction model for aqueduct deformation based on time series decomposition and machine learning, aimed at the problem of insufficient prototype observation data mining in previous aqueduct deformation predictions of low accuracy. First, a singular spectrum analysis is used to decompose the deformation monitoring data of an aqueduct into three parts: trend, seasonal, and remainder components. Then, we adopt a kernel-based extreme learning machine to predict the seasonal and trend components, and construct a prediction model of the remainder components using the long short-term memory and phase-space reconstruction theory. These prediction results are superimposed to construct a combined aqueduct deformation prediction model through time series decomposition and machine learning. Against the deformation monitoring data from the Shuangjihe branch aqueduct, this combined model is verified. The results show it is a robust model with a prediction accuracy higher than that of conventional prediction models.
		2022 Vol. 41 (2): 102-112 [Abstract] ( 148 ) PDF (1525 KB) ( 535 )

	113	Study on location management technology for construction resources in complex scenes of hydropower projects
		FAN Qixiang, LIN Peng, XIE Liang, LIU Yuanda, ZHU Qiang, LI Guo, GU Bin, WEI Pengcheng
		DOI: 10.11660/slfdxb.20220212
		Technology of construction resource positioning in complex scenes is of great significance to large-scale hydropower project construction. Based on field tests and construction practices of Wudongde and Baihetan hydropower station in Southwest China, this paper focuses on different scenarios and different tasks with application of the location technologies of LBS, GPS/Beidou with real-time differential (RTK), and low-power Bluetooth (BLE). We construct a hybrid positioning technology model and a corresponding system that satisfy the needs of different scenarios, different job positioning accuracies, and different speeds of communication response. An electronic map based on GIS combined with spatial layout and structural characteristics is developed; the project area is divided into grids by the requirements of construction and project management. We develop a terminal-network-cloud system for onsite location, realizing multi-terminal refined, personalized and customized three-dimensional real-time dynamic management of the real locations of construction resources. This study shows that the digital and intelligent transformation of hydropower project construction management needs developing location technology and its support.
		2022 Vol. 41 (2): 113-124 [Abstract] ( 145 ) PDF (2681 KB) ( 481 )