Journal of Hydroelectric Engineering

水力发电学报

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2021 Vol. 40, No. 3 Published: 2021-03-25

	1	Hydraulics of high-speed flows: recent achievements and future outlook ^Hot!
		ZHANG Jianmin
		DOI: 10.11660/slfdxb.20210301
		In the past 40 years, the construction of water conservancy and hydropower projects in China has developed rapidly. A large number of world-class hydropower projects have been built, and a variety of innovative technologies have emerged, which has promoted the research on flood discharge and energy dissipation of the high head and large discharge flows in China to reach the global advanced level. This paper focuses on a review of the latest research achievements in flood discharge and energy dissipation of high head and large discharge in China, including full section aeration and erosion reduction technology, high arch dam flip bucket energy dissipation of air collision and non-collision nappes from surface and deep outlets, high gravity dam energy dissipation of multi-layer submerged jet bottom flows, stepped spillways, and internal flow energy dissipators of dovetail flip buckets, roll flip buckets, tunnel plugging, and swirl generators. A prospect of high dam hydraulics in the future is presented.
		2021 Vol. 40 (3): 1-18 [Abstract] ( 384 ) PDF (5063 KB) ( 1528 )

	19	Advances in research of optimal rainwater infrastructure configuration in sponge city construction
		JIANG Chunbo, LI Jiake, GAO Jiayu, LV Peng, YAO Yutong, LI Huai’en
		DOI: 10.11660/slfdxb.20210302
		Climate change and rapid urbanization have modified the process of urban eco-hydrologic cycle, aggravating urban problems such as water shortage, water environment pollution, water ecology destruction, and rainstorm flood disaster. This paper presents a systematic summary of the core indexes and control points of sponge city construction in new and rebuilt urban areas with different planning objectives, to obtain the spatial optimal allocation scheme and multi-objective cost-benefit optimal curve of a system coupling low impact development (LID) facilities or green infrastructure (GI) with urban gray infrastructures. Aimed at the existing issues in research, a regional optimal allocation pattern of rainwater infrastructure is constructed, comprising three major parts–performance index database of rainwater infrastructure, cost-benefit quantification, and computer aided decision-making. The key parameters and performance indexes of typical LID facilities in numerical calculation and model simulation are discussed. Then, the method of quantifying sponge city construction with cost and benefit indexes is analyzed by applying the theory of environmental economics. Finally, multi-objective intelligent optimization schemes are explored for improving urban water environment, water ecology, water resources, and water security with limited cost input. Meanwhile, model simulations are combined to realize the virtuous cycle and sustainable development of urban ecology and hydrology.
		2021 Vol. 40 (3): 19-29 [Abstract] ( 420 ) PDF (2408 KB) ( 1670 )

	30	Variations in flow and sediment in Dongting Lake and its influencing factors after operation of Three Gorges dam
		RAN Xueyan, ZHU Dejun, LI Danxun
		DOI: 10.11660/slfdxb.20210303
		Reservoir construction modifies the relationship between rivers and lakes and affects the downstream flow and sediment conditions, thereby impacting the river basin, human life, and social development. Using the 2003-2019 data series of runoff and sediment discharge in the Dongting region, variation trends in flow and sediment are analyzed using Mann-Kendall trend test and slip averaging, focusing on their abrupt changes through Mann-Kendall mutation analysis. The results show that for this period, significant variations with abrupt change points are noticeable in the annual sediment discharges at Dongting Three Entrances and the annual runoffs at the hydrological stations of Mituosi and Kangjiagang, while no significant variation can be detected in the annual runoff at the Entrances’ other stations or in the annual runoff or sediment discharge in the Dongting Four Tributaries. The abrupt change points of flow and sediment at Mituosi were in 2014 and 2010 respectively, while the rest were around 2008. The incoming flow and sediment from the Yangtze mainstream, which had been obviously affected by the 2008 test impoundment to 175 m of the Three Gorges dam, was an important factor of the variations in Dongting’s water and sediment. And sand mining and other factors were also possibly related to the scour and deposition in this lake.
		2021 Vol. 40 (3): 30-38 [Abstract] ( 197 ) PDF (903 KB) ( 484 )

	39	Conceptual modelling of bank erosion processes at typical sections in braided reach of lower Yellow River
		WANG Yingzhen, XIA Junqiang, DENG Shanshan, ZHOU Meirong
		DOI: 10.11660/slfdxb.20210304
		In recent years, significant channel evolution has occurred in a braided reach of the lower Yellow River (LYR), and a key factor of its channel lateral deformation is bank erosion that has negative influence on the stability of this reach. To investigate the bank erosion, this study develops a cross-section-scale conceptual model for simulating the time development of bank erosion at the cross-sections of Fanzhuang and Jiahetan observed in the flood season of 2004, and identifies the key factors of bank erosion. The results indicate that the calculated cumulative erosion widths were 413 m and 733 m for these two typical sections, agreeing well with the observations in-situ; the calculated time variations in bank erosion width were consistent with those in lateral bank-toe erosion width, demonstrating the unfavorable effect of large lateral erosion widths on bank stability. By the calculations, erosion width is decreased with an increase in soil erosion strength. The decreases in bank erosion width were 34% and 33% at Fanzhuang and Jiahetan respectively when soil erosion strength increasing from 0.1 to 0.3 N/m2. And at these two sections, the bank erosion widths were decreased by 10% and 7% respectively when the bank-toe deposition ratio of collapsed soil increasing from 50% to 100%, showing a favorable effect of high bank-toe deposition ratios on river bank stability.
		2021 Vol. 40 (3): 39-49 [Abstract] ( 159 ) PDF (1020 KB) ( 626 )

	50	Short-term power balance model considering cost of abandoned hydropower
		JI Changming, ZHAO Yawei, ZHANG Yanke, MA Haoyu
		DOI: 10.11660/slfdxb.20210305
		To raise the level of hydropower consumption during flood season, an objective of minimizing abandoned hydropower cost is added to the previous minimum cost model, and a short-term power balance model that takes this cost into account is developed for the power system. And an improved particle swarm optimization algorithm is formulated based on a rolling correction strategy to overcome the difficulty in obtaining effective feasible solutions satisfying large-scale complex constraints and to avoid premature convergence and local optimization. Calculations of the Dianzhong regional power grid in Yunnan Province shows that relative to the minimum cost model, although the cost of the other energy sources is increased by 1.42 million Yuan, the abandoned hydropower in flood season is decreased by 7.14 million kWh and the total system cost by 7.0%. Relative to the minimum abandoned hydropower model, although the abandoned hydropower is increased by 2.85 million kWh, the thermal power cost is decreased by 17.95 million yuan and the total system cost by 21.7%. In the period of peak regulation capacity lacking, a proper arrangement of the other power stations for peak regulation can effectively reduce the abandoned hydropower and total cost.
		2021 Vol. 40 (3): 50-63 [Abstract] ( 177 ) PDF (706 KB) ( 594 )

	64	Influence of field observation on effectiveness of data assimilation using EnKF algorithm for large-scale river network
		GU Luhua, LAI Xijun
		DOI: 10.11660/slfdxb.20210306
		Accurate simulation of large-scale river networks is still a difficult issue at present, and uncertainty in real environments is responsible for the inefficiency in improving the accuracy of traditional simulation methods. Data assimilation, which fuses data and observations, is an important method to improve the accuracy of practical predictions. This paper develops an assimilation model integrating the Taihu basin river network model and ensemble Kalman filtering algorithm to explore how field observations impact the assimilation effectiveness. The results show the water conservancy zones in this basin are relatively independent, thereby requiring a certain amount of observations in each zone to achieve effective assimilation results. And for each zone, two or three observation points with a sampling interval of 1-2 days will be enough to reduce the simulation errors by about 40% in comparison to the traditional method. The predicted stages of Taihu basin agree with observations with the maximum prediction error of flood stage no more than 0.02 m at stations of Yixing, Danyang, and Changzhou.
		2021 Vol. 40 (3): 64-75 [Abstract] ( 276 ) PDF (1882 KB) ( 562 )

	76	Frequency analysis of annual precipitation based on Johnson distribution
		CHANG Haohao, SONG Songbai, WU Haijiang, CHEN Defang
		DOI: 10.11660/slfdxb.20210307
		The Johnson distribution has many transformation forms, and therefore it can achieve a good curve fitting capability through complicated transformation curves. This article discusses parameter estimation using the moment method, quantile method, ordinary least square method (OLS), weighted least square method (WLS), and diagonal weighted least square method (DWLS). These five methods are used for curve fitting and the fitted Johnson distributions are compared with the fitting of P-Ⅲ distribution. To calculate precipitation frequency, we select the data series of annual precipitation at four meteorological stations (Dingbian, Yichuan, Zhidan and Wuqi) in northern Shaanxi, and use the Johnson distribution and the five parameter estimation methods to estimate the parameters of these data series. The results show that the annual precipitation frequency curve based on the Johnson distribution model can effectively fit the series; and DWLS gives the best fitting, followed by the moment method, OLS, WLS, and quantile method. In addition, the fitting of Johnson distribution is slightly better than that of P-Ⅲ distribution.
		2021 Vol. 40 (3): 76-83 [Abstract] ( 191 ) PDF (683 KB) ( 487 )

	84	Operation method of hydropower stations based on search space reduction strategy using equal flow regulation method
		HUANG Chengjian, XIE Yangyang, LIU Saiyan, BIAN Jili
		DOI: 10.11660/slfdxb.20210308
		Reasonable operation methods help improve the power generation profits of hydropower stations. Generally, numerical simulation methods can obtain feasible solutions easily, but often have difficulty in finding out the optimal solutions. By contrast, an optimization method could obtain optimal solutions, but its given search space is often too large, thereby making the solutions unsatisfactory. Considering the characteristics of the methods of these two types, this study develops a new optimal operation method of hydropower stations based on search space reduction strategy using the equal flow regulation method. In this new method, equal flow regulation is adopted to numerically simulate the operation process, and the search space is reduced according to the process simulated. Then, in this reduced space, the operation model of hydropower stations is solved using an optimization method. A case study shows that this search space reduction method is suitable for applying the swarm intelligence algorithm to solve the operation model of hydropower stations. Under the same swarm intelligence algorithm and the same operation model of a hydropower station, it can increase the annual average power yields and firm power outputs significantly and reduce the annual average volume of waste water significantly. And in the reduced search space, the swarm intelligence algorithm converges much faster, and the standard deviations are much smaller. Thus, our new method proves effective in improving the optimization degree, convergence speed, and solution stability of swarm intelligence algorithms, very useful for the optimal operations of hydropower stations.
		2021 Vol. 40 (3): 84-95 [Abstract] ( 129 ) PDF (2533 KB) ( 358 )

	96	Effect of clearance cavitation on pressure pulsation characteristics of bulb turbine
		XU Hongquan, HE Chenglian, MENG Long, ZHANG Yiyang
		DOI: 10.11660/slfdxb.20210309
		Severe vibration and noise of bulb turbines at hydropower stations is the main cause of unstable operation. Up to the present, the previous research of bulb turbine stability has focused on rotational frequency and vortex frequency rather than the harm of high power rotational frequency pressure pulsations and their causes. In this paper, the theory of destructive effect of cavitation on hydraulic mechanical stability is applied to study clearance cavitation in bulb turbines, and the relationship between clearance cavitation and such pressure pulsations is demonstrated and analyzed by combining theoretical analysis with prototype and model test verification. This paper describes the pressure pulsations in the draft tubes of model and prototype bulb turbines, along with the vibration frequency characteristics and working conditions in prototype; and points out that the cause for the high power rotational frequency pressure pulsations is the occurrence of cavitation at runner blade tip clearances and guide vane tip clearances. This study proves that the blades passing frequency pressure pulsations and their second and third harmonics are induced by the clearance cavitation between the blade tips and the discharge ring or runner hub, and the guide vanes passing frequency pressure pulsations induced by the guide vane tip clearance cavitation.
		2021 Vol. 40 (3): 96-102 [Abstract] ( 234 ) PDF (1194 KB) ( 814 )

	103	Aerodynamic characteristic analysis of impulse turbine in conditions of steady flow and reciprocating flow
		YU Yang, ZHAO Mingren, YU Jianxing, LI Zhenmian, GAO Yang, XU Lixin
		DOI: 10.11660/slfdxb.20210310
		To make full use of the energy of reciprocating flow in the oscillating water column, this study numerically simulates and analyzes the performance of an impulse turbine in the conditions of steady air flows and reciprocating air flows, including analysis of the input coefficient, torque coefficient and efficiency. Accuracy of the numerical calculations is verified through comparison to previous studies in the literature. The results show that as important geometric parameters of the impulse turbine, the outer diameter clearance should be about 1 mm and the number of moving blades be 30. In reciprocating flow modes, the performance curve of an impulse turbine has a hysteresis loop due to its different performances in acceleration and deceleration stages. And because of different pressure drops in these two stages, the input coefficient curve has a clockwise hysteresis loop, while the efficiency curve has an anticlockwise hysteresis loop. In contrast, the torque coefficient shows no obvious hysteretic behavior. Comparison of the results of steady and reciprocating flows reveals the lower reciprocating flow frequency results in the turbine performance closer to that of the steady flow case.
		2021 Vol. 40 (3): 103-112 [Abstract] ( 211 ) PDF (4598 KB) ( 504 )

	113	Application of neural network response surface in rheological inversion of rockfill dam
		ZHOU Xinjie, SUN Xinjian, GUO Huashi, LI Qiaoying, GUAN Zhixuan
		DOI: 10.11660/slfdxb.20210311
		Rheological parameters of rockfill are important for long-term safety analysis of high concrete face rockfill dams (CFRDs). Parameter inversion can accurately obtain rheological parameters to meet the practical long-term deformation law. This paper uses Backpropagation (BP) neural network and Radial basis function (RBF) neural network to construct the response between the parameters to be inverted and the measured displacement, and introduces the root mean square error (RMSE), the average absolute percentage error (MAPE), and the linear regression determination coefficient (R2) in the statistical regression prediction model to comprehensively compare the mapping capabilities of different neural network response surface. They can improve the efficiency and accuracy of parameter inversion. Results show that the evaluation indexes of RBF neural network response surface are better than those of BP neural network response surface. Therefore, we adopt RBF neural network response surface and multi-population genetic algorithm (MPGA) to obtain the rheological parameters after inversion and use them for finite element calculation. It is found that the obtained settlement values of the Xujixia concrete face rockfill dam agree well with the measured ones both in magnitude and in distribution.
		2021 Vol. 40 (3): 113-123 [Abstract] ( 177 ) PDF (850 KB) ( 471 )

	124	Density-based detection of clustering outliers in long-term monitoring data
		LI Mingchao, LI Minghao, REN Qiubing, SHEN Yang
		DOI: 10.11660/slfdxb.20210312
		A density-based clustering outlier detection algorithm using improved local outlier factors is presented for analysing long-term hydraulic structure monitoring data. It is aimed at the problems that the distribution assumptions are difficult to meet, the number of outliers to be processed is limited, and the outliers are difficult to effectively be quantified. It divides the long-term data set into extreme clusters, outlier clusters, and normal clusters; in each cluster, anomalous possibilities are assigned in different ways, and it obtains an anomalous possibility that considers independent variables and effect sizes comprehensively. Its sequence diagram realizes the identification and quantitative analysis of long-term data sets of hydraulic structures. The core algorithm requires no distribution assumptions. This method can improve the definition of the reachable distance for the local outlier factor algorithm, expanding the difference between high and low anomaly coefficients. Thus, it can easily distinguish the outliers from other data points. Based on the long-term monitoring data from a water transfer project, their credibility is calculated using such a sequence diagram for cases where the number and locations of outliers are unknown. Using the credibility as the weight of the regression model, the predictions are greatly improved in comparison to the unweighted model, verifying the effectiveness of our new method.
		2021 Vol. 40 (3): 124-133 [Abstract] ( 184 ) PDF (570 KB) ( 558 )

	134	Image-based quantitative and efficient identification method for concrete surface cracks
		WANG Chao, JIA He, ZHANG Sherong, SHI Zheng, WANG Xiaohua
		DOI: 10.11660/slfdxb.20210313
		The convolutional neural network (CNN) algorithm is commonly used in automated crack detection, but its current version is too complicated involving many training parameters, high equipment configuration requirements, and low detection real-time performance. This paper develops a lightweight CNN method (LFNet). This simplified version of CNN reduces the number of training parameters, and then analyzes and extracts cracking features from the images of cracked concrete through a threshold division weight method based on Gaussian gradient change. Finally, it calculates the crack width using a Euclidean distance algorithm. Comparison with experimental results shows LFNet is better than previous methods of classical convolutional neural network and achieves an accuracy, recall and F1 value of 97.9%, 98.3% and 98.1% respectively. Its calculation errors of characteristic crack widths can be controlled within a range of 0.5 mm.
		2021 Vol. 40 (3): 134-144 [Abstract] ( 358 ) PDF (1995 KB) ( 1007 )

	145	Effects of reservoir bottom wave absorption on dynamic response of gravity dams
		LI Yanpeng, LI Jianbo, LIN Gao
		DOI: 10.11660/slfdxb.20210314
		Reservoir bottom wave absorption is an important part of the interaction in a gravity dam-foundation-reservoir system. In this study, the absorption is simulated using an acoustic structure coupling method and impedance boundary conditions. An example verification analysis shows that an accurate curve of hydrodynamic pressure distribution over the dam surface can be obtained in the case of different coefficients of reservoir bottom reflection at the same excitation frequency or the case of these coefficients taking the same value at different excitation frequencies. Analysis of the new Fengman gravity dam supports the conclusion that the reflection coefficient has significant influence on the pressure distribution, and an increase in the coefficient will enhance the amplitude of hydrodynamic pressure and consequently the dynamic response of the dam. The influence of the old Fengman dam, located in the upstream, on the new one is examined, revealing the existence of the old dam brings about significantly larger amplitudes in the variations of hydrodynamic pressure over the whole surface of the new dam.
		2021 Vol. 40 (3): 145-154 [Abstract] ( 180 ) PDF (1766 KB) ( 470 )

	155	Study on the super high arch dam structure adapting to the columnar basalt base
		XU Jianrong, LAI Daoping, WU Guanye, HE Mingjie, WANG Xianbiao, ZHANG Weidi
		DOI: 10.11660/slfdxb.20210315
		The columnar basalt rock develops in the dam site area of Baihetan hydropower station. Its deformation modulus is relatively low owing to its poor integrity. Especially, it shows the characteristics of anisotropy and easy relaxation after excavation. It is the first time that the columnar basalt rock is chosen as the base of super high arch dams at the site of Baihetan Hydropower Station. The structural form of expanded foundation was put forward for the design of the super high arch dam to adapt to the characteristics of the columnar basalt at the base. By applying the three-dimensional finite element method, the thrust force expanding mechanism and the effect of expanded foundation were studied, and the effect of the relaxation of the columnar basalt on the arch dam was also studied. The capability of the expanded foundation of the arch dam to adapt to the foundation characteristics of the columnar basalt rock layers was demonstrated by computation results.
		2021 Vol. 40 (3): 155-164 [Abstract] ( 184 ) PDF (2176 KB) ( 512 )

	165	In-situ experimental study on deformation behaviors of lining structure for shield tunnels under high internal pressure
		HUANG Jingwu, YAN Zhenrui, LI Daimao, TANG Xinwei, YAO Xiaoqing
		DOI: 10.11660/slfdxb.20210316
		For the construction of urban water conveyance underground shield tunnels under high internal pressure, we propose a separate lining structure of self-compacting concrete (SCC)-lined steel pipe, and present an in-situ experiment on this new structure for exploring its deformation behaviors that was conducted in the test section of a water resources allocation project in Pearl River Delta. Flexible capsules are used to simulate the high internal pressure in the tunnel; the testing technology of fiber Bragg grating and distributed optical cables used to monitor the structure deformation. The results show that as the internal pressure increases, the deformation in the segment, self-compacting concrete, and steel pipe are increased gradually; the strain distributions at the concrete’s inner arc surface and the segment’s arc surface are more uniform than those at the concrete’s outer arc surface. The composite drainage plate can effectively separate the segment and the self-compacting concrete. The deformation in the steel pipe manifests characteristics of overall tension and local bending, and is significantly affected by internal pressure.
		2021 Vol. 40 (3): 165-172 [Abstract] ( 164 ) PDF (1729 KB) ( 575 )