Journal of Hydroelectric Engineering

水力发电学报

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2021 Vol. 40, No. 10 Published: 2021-10-25

	1	Analysis of upstream migrating channels based on characteristics of fish swimming in variable flow field
		SUN Lin, YI Wenmin, ZHANG Xinglei, LI Jia, AN Ruidong
		DOI: 10.11660/slfdxb.20211001
		Hydropower development impacts the habitat of migratory fishes significantly. Predicting the upstream migrating passage of target fish in their migration period can provide a basis for construction of fishway facilities so as to mitigate the negative effects. This study selects a research area in the reach downstream from the Huduxi hydropower-navigation project, takes Leptobotia elongate, Onychostoma sima and Gobiobotia bouleugeri as the target fish, and divides the study area into flow zones of different velocities by the swimming performance of these fishes. We obtain flow velocity suitability curves suitable for different fish-passing targets, and numerically simulate typical flow rates in the study area in the fish-passing period. Then, based on the suitability curves, we can evaluate the flow velocity suitability of different fish-passing targets for the study area, and use the evaluations to predict an upstream migrating channel that satisfies the multi-target fish-passing conditions. The results show that the location of fish passage optimized through flow velocity suitability evaluation varies with the channel flow rate. It goes through the mainstream zone under low-flow conditions, while through both sides of the mainstream zone under high-flows. And the proportion of the passage area to the total area also varies with the flow rate, with its low-flow values about 3 to 4 times its high-flow values. By the fish migrating channel predicted in this study, we make suggestions to optimize the layout of fishway inlet and the operation and dispatching of the power station, providing a basis for protecting the related fishes.
		2021 Vol. 40 (10): 1-9 [Abstract] ( 204 ) PDF (4411 KB) ( 606 )

	10	Experimental study of effects of sediment concentration on cavitation erosion in high velocity flows
		DONG Zhiyong, SUN Jinyang, LI Yuhang, XU Xuyi
		DOI: 10.11660/slfdxb.20211002
		The effect of sediment concentration on cavitation erosion in high velocity flows is studied experimentally in a small looped water tunnel. First, we prepare artificially sediment-laden flows with low, moderate and high concentrations in the inner tank of the tunnel, and measure the volume concentration using an infrared suspended solid analyzer. Pressure in the cavitation erosion zone at different concentrations is measured using a dynamic pressure acquisition system. Then, we use concrete specimens of different concrete ages and different mix proportions and install them in the cavitation zone and cavitation erosion zone separately. An erosion and abrasion test run takes five hours and the weight loss per hour is used as the cavitation erosion rate and abrasion rate. The experimental results show that at a grain diameter of d50 = 1.09 mm and concentration of S = 0 ~ 30 kg/m3, time-averaged pressure and cavitation number in the cavitation erosion zone rise with an increase in concentration, promoting the occurrence of cavitation erosion. With mix proportion and age fixed, cavitation erosion intensifies with an increase in concentration, and the eroded area expands. The anti-cavitation erosion capacity of specimens with a higher strength is greater than that with a lower strength at different concentrations; the greater increase in concentration, the greater difference in the capacity. Prolonging cure time of a concrete specimen enhances its anti-cavitation erosion capacity at different concentrations. For the same test time, the abrasion rate of a concrete specimen is much smaller than its cavitation erosion rate, indicating cavitating action far stronger than sediment abrasion action in high velocity sediment-laden flows.
		2021 Vol. 40 (10): 10-18 [Abstract] ( 226 ) PDF (1403 KB) ( 620 )

	19	Advances and challenges to optical flow applications in measurement of highly aerated flow field
		TANG Rongcai, WANG Hang, BAI Ruidi, SANG Wei, LIU Wei
		DOI: 10.11660/slfdxb.20211003
		Velocity measurement of highly aerated flows is a key issue in air-water two-phase flow research and hydraulic engineering. Bubbly flows, self-aerated or artificially-aerated, are very complicated in evolution mechanism and rapid turbulent fluctuations; currently-used techniques are limited in accurate measurements of their flow velocity and turbulences. Optical flow-based flow visualization technologies attract a great interest in the field of image recognition due to its unique advantages. The optical flow method enables calculation of the high-resolution optical fields for the meso-scale movement of air bubbles by using the brightness of pixels on the image, thereby making up for the shortcomings of traditional particle image velocimetry. This paper discusses the principle of classical optical flow methods and reviews the existing optical flow technologies applicable to highly aerated flows, so as to provide a comprehensive picture of the advances and the state of the art in the aerated flow visualization applications of these technologies. Then, we sum up the key processing techniques and parameter selections for applications to the complicated cases of highly aerated flows. Finally, the challenges and frontiers of related theoretical and practical issues faced in highly aerated flow measurements are discussed, and their future development directions are prospected.
		2021 Vol. 40 (10): 19-29 [Abstract] ( 165 ) PDF (1469 KB) ( 580 )

	30	Comparison of flow velocity distributions in open channel with continuous and uniform submerged vegetation
		ZHANG Weile, WU Shiqiang, WU Xiufeng, GAO Ang, WANG Fangfang
		DOI: 10.11660/slfdxb.20211004
		Flow velocity distribution of a river under the influence of vegetation is an important index for evaluating its flood discharge capacity and a major factor of riverbed stability and river safety. This paper sums up recent advances in the research of flow velocity distributions of vegetated rivers in China and abroad, focusing on the patches of submerged vegetation with continuous and uniform distributions. We expound the formation mechanism of flow velocity profiles, and analyze the state-of-the-art research and its shortcomings in formulating analytical solutions for the zoned flow velocity distributions and developing average flow velocity models. Based on the literature, applicability and accuracy of previous average flow velocity models are evaluated. We emphasize that for river channels with vegetation patches of continuous and uniform distribution, most of the previous studies on the solution for flow velocity have focused on single vegetation type and simple vegetation shape in straight channels under uniform flow conditions. And future research of the flow velocity distributions should put more efforts on the resistance coefficients of submerged vegetation, bed stress under the influence of vegetation, non-uniform flow conditions, and flexible vegetation patches of finite sizes.
		2021 Vol. 40 (10): 30-44 [Abstract] ( 177 ) PDF (1274 KB) ( 531 )

	45	Analysis and modeling of tailwater level characteristics of hydropower stations
		JIA Benjun, ZHOU Jianzhong, CHEN Xiao, ZHANG Yongchuan, TIAN Mengqi
		DOI: 10.11660/slfdxb.20211005
		This paper focuses on how to analyze and model accurately the tailwater level characteristics of hydropower stations, so as to achieve high accuracy predictions. First, we reveal the aftereffect characteristics of tailwater level variations at hydropower stations by combining qualitative and quantitative analysis, and explore preliminarily the key influencing factors of the variations based on a Pearson correlation analysis. Then, we construct a polynomial fitting model and a support vector regression model, and compare and analyze their performances in prediction of tailwater level variations Case studies of the Xiluodu-Xiangjiaba cascade and Three Gorges-Gezhouba cascade show a significant aftereffect is produced by a two-hour variation in the tailwater stages of the four hydropower stations. And the support vector regression model with reservoir discharge of the present and previous periods and reservoir tailwater stage or downstream tributary discharge as inputs is a practical, reliable and accurate in prediction of the tailwater levels.
		2021 Vol. 40 (10): 45-59 [Abstract] ( 151 ) PDF (3351 KB) ( 534 )

	60	Study of water balance change and its influence on water stage in the Qinghai Lake
		WANG Xinyu, GAO Bing
		DOI: 10.11660/slfdxb.20211006
		This paper develops a water balance equation for the Qinghai Lake using its water stage and meteorology observations for the period of 1961 to 2015, estimates its annual precipitation, evaporation and inflow, and analyzes the time trends of its water balance components. Regression analysis is used to examine the contribution rates of different factors to the time variations in its water stage. The results show the water stage in the lake decreased before 2005 and since then has risen evidently. Its annual precipitation is 14.6×108 m3, annual inflow runoff 24.4×108 m3, and annual evaporation 40.1×108 m3. In the period of 1961 to 2015, precipitation on the lake showed an increasing trend; its inflow runoff has increased significantly since 2003 and evaporation decreased since 2000. Inflow increase and precipitation increase together with reduced evaporation was the cause of lake stage rising after 2005, with the inflow runoff contributing the largest proportion of 38.2% to the stage variations.
		2021 Vol. 40 (10): 60-70 [Abstract] ( 194 ) PDF (2847 KB) ( 571 )

	71	Risk operation of inhibiting salt tide invasion and its space-time transmission in Xijiang watershed
		BAI Tao, LI Lei, HUANG Qiang, WU Yunchen, LIU Xia
		DOI: 10.11660/slfdxb.20211007
		As salt tide invasion in the Pearl River becomes increasingly severe in dry season, the risk of inhibiting the invasion is aggravated by uncertainty in the runoff, gravely lowering the safety of water supply across the watershed. This paper describes the uncertainty in the river runoff based on probability density distribution, and constructs a basic framework of single-source risk operation. In a case study of five reservoirs in the Xijiang watershed, we formulate a quantitative relationship of the runoff forecast error versus the systematic risk of inhibiting salt tide invasion, and reveal how the risk is transmitted in space and time. The forecast error is divided into three grades, and the threshold of each risk leapfrogging across the grades is determined. The results show that as the forecast error increases, the risk occurs earlier, the number of salt-inhibiting days and the risk value are increased. In time, the risk transfers from time to time in a cumulative way; in space, the risk transfers from upstream to downstream and from tributaries to the main stream. The risk leapfrogs from light to medium grade when the forecast error exceeds 16%, and from medium to heavy grade when it exceeds 21%. The results have significant application to risk regulation and control for the Xijiang watershed and to water supply security assessment for the Guangdong-Hong Kong-Macao Greater Bay Area.
		2021 Vol. 40 (10): 71-80 [Abstract] ( 116 ) PDF (547 KB) ( 444 )

	81	Rapid simulations of storm water runoff in urban community scale. Case study of a community compound in Fuzhou City
		YE Chenlei, XU Zongxue, LEI Xiaohui, CHEN Yang, BAN Chunguang, SU Heng
		DOI: 10.11660/slfdxb.20211008
		With the rapid development of urbanization, most cities in China are faced with increasingly severe flood problems. In this paper, a storm water management model (SWMM) is constructed on a community compound scale, and its parameters are determined using the genetic algorithm. Then, two types of most representative rainstorms are selected using a fuzzy identification method based on an analysis of precipitation over the study area. Finally, a long short-term memory (LSTM) model is developed for this area based on the dataset of its different rainfall data and SWMM simulations, a relationship between its rainfall and runoff is obtained, and the LSTM model is evaluated against different conditions. The results show that LSTM simulations agree roughly with those of SWMM, but its peak flood fitting is slightly deviated. Compared with SWMM simulations, LSTM simulated peak floods are smaller for small rainfall and greater for greater rainfall, and LSTM performs the best for medium rainfall. The peak flow fitting is better with 50 hidden layer elements, but more elements will produce an even better effect on the peak flow.
		2021 Vol. 40 (10): 81-94 [Abstract] ( 195 ) PDF (4217 KB) ( 642 )

	95	Scientific basis and quantitative method for water allocation of trans-province rivers
		CUI Shibo, LUO Lin, HU Shiruo, ZHAO Jianshi
		DOI: 10.11660/slfdxb.20211009
		Water allocation of trans-province rivers is the basis and premise to manage the conflicts between human water demands and natural water demands and the clashes among water uses by different provinces. It is essentially a type of benefit allocation that should be based on both the natural sciences and social sciences. This paper discusses several basic principles for water resources allocation based on the theory of justice in politics and the theory of property rights in economics, and develops a quantitative model for water allocation of trans-province rivers, considering water supply-demand relationship and hydrological characteristics. Applications of this model to case studies of the basins of Wuding River and Wei River demonstrate its uses in two scenarios of water surplus and water shortage. The results show that it meets the basic human and natural water demands, and its optimized allocation scheme can alleviate the social conflicts and is easy to implement. Thus, it helps better balance the conflicts of domestic water use, economic water use, and ecological water use among the riparian provinces.
		2021 Vol. 40 (10): 95-104 [Abstract] ( 136 ) PDF (835 KB) ( 379 )

	105	Improved procedure to determine turbine efficiency by thermodynamic method
		CAO Dengfeng, ZHANG Peng, ZHOU Ye, ZOU Zhichao
		DOI: 10.11660/slfdxb.20211010
		In determining turbine efficiency, the thermodynamic method obtains turbine discharge and efficiency through measuring specific energy per unit, with no direct measurement of discharge, but its accuracy is affected significantly by uneven velocity profiles at low-pressure sections. Focusing on this problem, this paper presents an improved iteration procedure to determine flow velocity at low-pressure sections, discharge and efficiency. It saves test work due to avoiding direct measurement of flow velocity. In the calculation procedure, we iterate the corrective terms of specific mechanical energy and flow velocity at the low-pressure sections, and obtain a final velocity that better represents the mean flow velocity at the low-pressure sections, so that the resulted efficiency is more accurate than direct measurement. Test results show that specific mechanical energy, turbine discharge and efficiency can be worked out by only several iteration steps, which can meet engineering test requirements, demonstrating the procedure is an improvement on the application of the thermodynamic method to low-head turbine measurements.
		2021 Vol. 40 (10): 105-111 [Abstract] ( 167 ) PDF (587 KB) ( 520 )

	112	Unit stability analysis for Jixi pumped-storage hydropower station
		ZHANG Fei, NI Jinbing, LIU Ren, WEI Huan
		DOI: 10.11660/slfdxb.20211011
		Jixi pumped-storage hydropower station is the first hydropower station employing pump-turbine units with splitter blades developed by the domestic manufacturer, thereby catching attentions from many parties. During the commissioning of its first unit, several research teams conducted comprehensive tests on its running stability, including shaft run-outs, stationary component vibrations, and pressure pulsations.This paper employs the method of tracking the time-domain peak-to-peak values as well as using the spectrum technique in frequency domain to analyze the measured data, and discusses the characteristics of unit stability in different working modes﹣stable pumping operation, stable generating operation, pump mode startup, and turbine mode startup under load increasing. The testing results indicate that in stable running conditions, all the peak-to-peak values of the shaft run-out and stationary vibration are in Zone A of the specifications, thus meeting the requirements of safe operation. A pump-turbine unit with splitter blades has much more complicated frequency spectra of pressure pulsations in comparison with a routine Francis pump-turbine. In stable on-cam running of pump mode, dominant frequencies at certain measuring points vary with water head. For the startup processes of pump mode and turbine mode, the unit stability parameters meet the requirements of operation.
		2021 Vol. 40 (10): 112-123 [Abstract] ( 141 ) PDF (1742 KB) ( 657 )

	124	Simulation of faced rockfill dams considering temperature change and long-term deformation
		CHEN Hui, DENG Gang, ZHANG Yanyi, ZHANG Yinqi
		DOI: 10.11660/slfdxb.20211012
		Cracking of face slabs of a concrete faced rockfill dam is one of the key factors affecting its safety and performance. Based on the ABAQUS software, this study carries out secondary development to simulate the long-term deformation of rockfill material and the hydration heat of concrete, imposing a boundary of temperature varying in space and time. We examine the joint action mechanism of continuously increasing in the long-term deformation of rockfill body and spatiotemporal variations in environmental temperature, combining with a case study of a concrete faced rockfill dam in Laos. The main cause of a large number of early horizontal cracks on the panel is revealed－excessive along-slope tensile stress in the panel surface layer that is caused by temperature rising due to concrete hydration heat and by ambient temperature changes in early time after concrete casting. Results show that the tensile stress calculated in the condition of temperature change is higher than that under constant temperature. Thus, this study suggests an important perspective for selecting slab concrete casting timing and controlling temperature cracks or deformation cracks.
		2021 Vol. 40 (10): 124-134 [Abstract] ( 132 ) PDF (1756 KB) ( 512 )

	135	Intelligent monitoring instrumentation and system for construction quality of dynamic compaction based on multi-perceptions
		LIU Quan, ZHANG Hongyang, WU Zhi, JIN Yinlong, GAO Qiaoyu, LI Feiyu , YOU Chuan, ZHAO Yueliang
		DOI: 10.11660/slfdxb.20211013
		Tamping pit positioning, tamping count and tamping settlement are three basic indicators for monitoring the quality of dynamic compaction construction. How to measure tamping settlement is usually a challenge to traditional monitoring techniques, and the dilemma between its efficiency and accuracy are difficult to reconcile. This study developes a full set of multi-perception integrated intelligent monitoring instrumentation for monitoring dynamic compaction construction quality, a supporting intelligent monitoring software, and a monitoring system with an active measurement target based on photogrammetry. A real time kinematic Global Navigation Satellite System (GNSS-RTK) and a magnetic azimuth sensor are integrated to realize the coordinated positioning of the ramming machine and tamping pit, and tamping count is recorded using machine vision and temporal pattern recognition. We have also developed an information cloud platform for releasing monitoring data collected using the instrumentation. All the above systems and instruments working together can realize a real time measuring system for tamping pit positioning, tamping count monitoring, and tamping settlement calculation. Field experiments of dynamic compaction construction prove that the accuracy and efficiency of our monitoring instrumentation and system meets the engineering requirements. The results help develop new intelligent construction monitoring instruments and promote the monitoring level.
		2021 Vol. 40 (10): 135-146 [Abstract] ( 155 ) PDF (2657 KB) ( 523 )

	147	Deformation prediction of rockfill dams based on time series decomposition and deep learning
		LENG Tianpei, MA Gang, XIANG Zhenglin, MEI Jiangzhou, GUAN Shaoheng, ZHOU Wei, GAO Yu
		DOI: 10.11660/slfdxb.20211014
		Deformation monitoring data of a rockfill dam are a time series that can be mined using a time series prediction model for analysis of its variation trend. This paper presents a new method for rockfill dam deformation prediction. First, we use a seasonal-trend decomposition procedure based on loess (STL) to decompose the deformation monitoring data of a rockfill dam into three parts: secular trend, seasonal variation, and irregular variation. Then, an empirical mode decomposition (EMD) method is used to stabilize the irregular variation. Finally, we adopt a long short-term memory (LSTM) technique to predict the decomposed sequences and a Bayesian optimization method to optimize the parameters. To evaluate the accuracy of this method, we numerically simulate the Shuibuya concrete faced rockfill dam for different training time, prediction time, and numbers of outliers; and compare it with other time series prediction models. The results show our new method is more accurate and applicable to evaluating rockfill dam performance.
		2021 Vol. 40 (10): 147-159 [Abstract] ( 344 ) PDF (4452 KB) ( 968 )

	160	Dynamic monitoring model for dam deformation with spatiotemporal coupling correlation characteristics
		REN Qiubing, LI Mingchao, SHEN Yang, LI Minghao
		DOI: 10.11660/slfdxb.20211015
		Dam deformation behavior is a consequence of long-term interaction of many factors, and its evolution pattern usually involves two dimensions: time and space. However, previous intelligent modeling of dam deformation lacks a comprehensive consideration of time and space variations, and a large amount of spatiotemporal information needs to be further excavated from the prototype observation data. This paper develops a dynamic monitoring model for dam deformation with spatiotemporal coupling correlation characteristics from two view angles: time-series correlation for a single measurement point, and spatial correlation of multiple measurement points. This model takes the gated recurrent unit (GRU) neural networks as core layers to model and learn the inherent time-varying patterns in a historical deformation data series, and constructs the features of spatial variations through iterative extraction of effective deformation factors. It uses a soft attention mechanism to improve the probability weight allocation rule of the GRU hidden states, thus achieving adaptive learning of key information. Its effectiveness is verified in a case study of the Fengman concrete gravity dam. The results show that this monitoring model can accurately simulate the dynamic deformation evolution of a dam, and are more accurate in extrapolation prediction than conventional monitoring models.
		2021 Vol. 40 (10): 160-172 [Abstract] ( 199 ) PDF (923 KB) ( 873 )