Journal of Hydroelectric Engineering

水力发电学报

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2022 Vol. 41, No. 8 Published: 2022-08-25

	1	Calculations of bank stability of riprap revetment in Jingjiang reach and analysis of its influencing factors
		XIA Junqiang, ZHOU Yueyao, DENG Shanshan, ZHOU Meirong
		DOI: 10.11660/slfdxb.20220801
		A bank stability analysis model of underwater riprap revetment is presented that has been adopted to calculate the riprap failure processes at two typical cross sections of Beimenkou in the lower Jingjiang from 08/2017 to 10/2018. The impacts of different factors on revetment collapse are examined, including near-bank velocity, bed erosion and deposition, riprap-rock size, and bank slope. The calculations show that in this period, generally the riprap revetment was relatively stable with an average collapse ratio as low as about 5%. This ratio grew as flow velocity increased, and its growth became sharp at a certain critical velocity value that was higher in the condition of riprap with a larger angle of repose. A similar variation trend also showed between the collapse ratio and bed scour depth. With the increasing riprap-rock size or the decreasing underwater slope, the collapse ratio decreased gradually. Generally, riprap revetment with an underwater slope lower than 1:2.0 showed better stability.
		2022 Vol. 41 (8): 1-11 [Abstract] ( 187 ) PDF (1239 KB) ( 288 )

	12	Entropy production evaluation of a tidal turbine under yawed flow condition
		SONG Ke, YANG Bangcheng, DUAN Weihua
		DOI: 10.11660/slfdxb.20220802
		Tidal horizontal-axis turbines deployed in open water are often inevitably subject to yawed flow conditions, which can cause negative effects on their performance. The detailed hydraulic performance of such a turbine is investigated by numerically solving the Reynolds-averaged Navier-Stokes equations and a shear-stress-transport turbulence model; its simulated entropy production characteristics are examined. The results show that as the inflow yaw angle increases, the power and thrust are reduced and the optimum tip speed ratio (TSR) declines, while the power and thrust fluctuation amplitudes are increased. At a fixed yaw angle, entropy production increases with TSR; at an increasing yaw, it decreases at low TSRs and then grows at high TSRs. A larger yaw also leads to larger entropy production fluctuation amplitudes. In addition, a flow field analysis reveals that the yaw angle determines the downstream wake deflection direction and alters the wake shape significantly. Most of the entropy production loss takes place behind the blade tip and hub where large scale flow separation and vortices occur; this is naturally the main origin of high entropy production in the turbine. This study demonstrates the hydraulic characteristics, the mechanism of entropy production, and the locations of entropy production in a horizontal-axis turbine, laying a basis for its optimal design.
		2022 Vol. 41 (8): 12-19 [Abstract] ( 206 ) PDF (945 KB) ( 410 )

	20	Study on micro-oscillator energy capture characteristics of typical semi-submersible platform structure
		FANG Zhijie, LIU Yanjun, XUE Gang
		DOI: 10.11660/slfdxb.20220803
		Semi-submersible platform has a broad application prospect in the field of marine resources development, but there exists a problem of insufficient energy supply for platform equipment. In this study, a common semi-submersible platform is simplified into three typical floating foundations, and a wave power generation device is integrated into the foundation, so that a motion equation can be derived to couple the foundation and its floats. A hydrodynamic simulation code, i.e. AQWA, is used to carry out numerical simulations and parametric analysis, and the effects of several factors on the float’s energy capturing characteristics are obtained－wave incidence, the cross-sectional shape of the floating foundation, its diameter, and its distance to the foundation. The results show that for the microarray float, a four-prism foundation can enhance its energy capture in a specific wave incidence, while a three-prism shape makes it better adapted to wave excitation from all directions. A cylindrical floating foundation has a significant masking effect, weakening the float’s energy capture to a large extent. Wave incidence has a great influence on the floats around a four-prism or three-prism foundation, but little influence on the floats based on the cylindrical foundation. The average power output of a microarray float can be improved significantly by increasing its diameter or its distance to the cylindrical foundation.
		2022 Vol. 41 (8): 20-29 [Abstract] ( 165 ) PDF (599 KB) ( 395 )

	30	Two-dimensional numerical simulations of water-sediment transport in lower Yellow River wandering reach based on moving grids
		ZHANG Zhihong, PENG Yang, LUO Shiqi, YAO Lishuang
		DOI: 10.11660/slfdxb.20220804
		To address the issue of moving grids adapted to intense bank erosion in a wandering river reach, a two-dimensional mathematical model is developed based on moving grids and an orthogonal curvilinear body-fitted coordinate system using the arbitrary Lagrangian-Eulerian method, aimed at the unsteady flow and sediment transport in a wandering reach of the lower Yellow River. Then, for the grid moving terms of the basic equations of flow and sediment transport under the orthogonal curvilinear body-fitted coordinates, a new formula is derived that allows the equations to obey the geometric conservation law. We also develop an approach to moving the grid nodes on the moving boundary through an algorithm of transfinite arc length interpolation. Finally, we verify this new model against the 2013 measurements of the wandering reach between Huayuankou and Gaocun. The results demonstrate that this grids-moving model is able to reproduce flow and sediment transport, river bed aggradation and degradation, and bank-floodplain scour and retreat in the studied wandering reach, and that it is also applicable to the other lower Yellow River reaches.
		2022 Vol. 41 (8): 30-41 [Abstract] ( 116 ) PDF (2734 KB) ( 486 )

	42	An ensemble Kalman filter method for adaptive operation of hydro-wind-solar hybrid power systems
		LIU Zheyuan, LIU Pan, LI He
		DOI: 10.11660/slfdxb.20220805
		The hydro-wind-solar hybrid power system is an important approach to achieving energy transition and carbon neutrality. Traditional medium- and long-term operation models for such systems ignore the variations in hydropower, wind and solar resources caused by climate change and human activities, so they often formulate operating rules that are static and difficult to adapt to the changing environment. In this work, we adopt an ensemble Kalman filter to study the adaptive operation of the system. First, an optimal operating trajectory is obtained using the deterministic optimal operation of the system; then, a decision variable and an independent variable are identified for the operating function, and a linear operating function is constructed. Finally, the parameters of the operating function are updated dynamically using the ensemble Kalman filter, forming adaptive operating rules. This procedure is applied in a case study of the Jinping I hydropower station along with the wind and photovoltaic power stations nearby. The result shows that in the validation period, the new adaptive operating rules achieve a power output increase of 645 and 53 million kW·h against the conventional and static rules, respectively. This demonstrates these new rules can adapt to the changing environment through tracking changes in the optimal operating trajectory.
		2022 Vol. 41 (8): 42-53 [Abstract] ( 173 ) PDF (2992 KB) ( 495 )

	54	Application of data mining techniques in real-time correction of flood forecasts
		CHEN Xin, LIU Yanli , ZHANG Jianyun, CAO Meng, HE Ruimin, JIN Junliang, WANG Guoqing, BAO Zhenxin
		DOI: 10.11660/slfdxb.20220806
		Real-time correction, as the last barrier to improving forecast accuracy, is an important part of flood forecasting. To address the problem of poor correction of flood process and flood elements, a joint real-time correction method combining a Kalman filter and a K-nearest neighbor algorithm is developed through selecting the rainfall runoff series of the basin and the eigenvalues of its historical flood data and constructing a storm flood feature database, in combination with a case study of the watershed above Tunxi of Hengjiang River. The results show that relative to the uncorrected model or single correction method, this new method is more effective in reducing forecast errors of flood peak, volume, and flood peak time, while it can maintain stability and accuracy for a forecast period of six hours or shorter. It could play an important role in improving flood forecast accuracy, effective early warning, and disaster prevention and mitigation for small- and medium-sized rivers or similar regional flood forecasting.
		2022 Vol. 41 (8): 54-62 [Abstract] ( 193 ) PDF (2269 KB) ( 489 )

	63	Typical disaggregation models and their application in disaggregating daily precipitation field
		LI Xin, JIN Ling, CHEN Yuanfang
		DOI: 10.11660/slfdxb.20220807
		High-resolution precipitation data are crucial for continuous hydrological modelling of the urban and small catchments with a short time of runoff concentration. In this study, we simulate hourly precipitation fields for nine meteorological stations surrounding Nanjing, using three daily-to-subdaily precipitation disaggregation models－i.e. single-site, regional, and multi-site disaggregation models－to disaggregate the daily precipitation data of the flood seasons (May to September) of 1983-2012. To evaluate the performance of these models, we apply multiple performance measures, including distributional statistics, extreme value distribution, spatial correlation, and intra-day wet and dry spell characteristics. Results show all the models give satisfactory simulations of distributional statistics, precipitation extremes, and intra-day wet and dry spell characteristics. Among them, only the multi-site model successfully simulates the spatial correlation of the observed hourly precipitation field, and it is more appropriate for distributed hydrological modelling. The results are useful for urban rainfall-runoff modelling and analysis.
		2022 Vol. 41 (8): 63-76 [Abstract] ( 156 ) PDF (4228 KB) ( 291 )

	77	Multi-temporal characterization analysis of remotely sensed precipitation downscaling in the Luanhe River Basin, China
		DONG Jiaping, YE Yuntao, GU Jingjing, CAO Yin, DUAN Hao, ZHAO Hongli, JIANG Yunzhong
		DOI: 10.11660/slfdxb.20220808
		To improve the spatial resolution of satellite precipitation products to meet the need for fine hydrological research, a convolutional neural network-based precipitation downscaling model is developed. It adopts the relationships of precipitation versus NDVI, DEM, slope, slope direction, latitude, and longitude from the Global Precipitation Observation Program multi-satellite precipitation product (IMERG) of better accuracy for regions in China. We also examine its overall performance and variations in its parameters for different timescales of a year, season, month, and ten-day. Results show that agreement indices of annual, seasonal and monthly downscaled results exceed 0.94, 0.89, and 0.69 respectively in comparison with original data; the model can also characterize precipitation at the ten-day scale. Compared with China Gauge-Based Daily Precipitation Analysis (CGDPA) data, the average agreement indices of annual, seasonal, monthly and ten-day downscaled results are 0.58, 0.78, 0.68, and 0.47 respectively; the similarity of model parameters increases gradually with the depth of the model layers. This study shows that this deep learning model has good convergence and good potential for basin-wide downscaling applications.
		2022 Vol. 41 (8): 77-91 [Abstract] ( 153 ) PDF (6823 KB) ( 271 )

	92	Study on CA-BINN dynamic path planning model for gravel soil core paving
		SUN Jiaen, WANG Jiajun, YU Jia, WANG Xiaoling, LI Qihu, LIN Weiwei
		DOI: 10.11660/slfdxb.20220809
		The existing operation path of gravel soil core paving mostly adopts static planning, which fails to consider dynamic changes of the obstacles in a complex operation environment such as bulldozers and dump trucks. To take this case into account, we develop a CA-BINN dynamic path planning model for gravel soil core paving in this paper. Based on the cellular automata (CA) modeling theory, this new model abstracts cellular state information－e.g. dynamic obstacles and paving thickness－from the real-time perceived complex working environment data, and conducts real-time reconstruction of a dynamic construction environment. It inputs this external information into a biological inspired neural network (BINN) algorithm, and reconstructs its neural activity value under the CA framework for calculation of the diversion equation, achieving the dynamic path planning of multi-pile overall paving operation. In this procedure, the paving operation of single material piles takes the indexes－e.g. paving integrity and invalid path ratio－as the objective functions, and dynamic path planning is realized using the three knife CA rule we formulated in the on-site three knife (three times moving material pile) construction. Engineering application shows that our new model not just has high safety and adaptability to complex dynamic operation environments, but can reduce path length, turning times and invalid path ratio by 1.9%, 42.9% and 48% respectively, and improve the paving smoothness by 7% against the static planning model. Compared with manual operation, it increases paving smoothness by 28% and reduces invalid path ratio by 47%, thus improving paving quality and efficiency significantly.
		2022 Vol. 41 (8): 92-103 [Abstract] ( 115 ) PDF (7314 KB) ( 64 )

	104	Effect of temperature on bending performance of hydraulic asphalt concrete beams
		HAN Qunzhu, SONG Ge, ZHANG Yingbo, SONG Honglin, SONG Qingxiang
		DOI: 10.11660/slfdxb.20220810
		In this work, bending tests on hydraulic asphalt concrete beams under temperature of -30 °C to 25 °C are carried out, and the influence of temperature on mechanical properties of hydraulic asphalt concrete panels is examined. Results show that, (1) the stress-strain characteristics of the concrete is closely related to temperature. In the range of - 30 °C to 0 °C, the stress-strain curve is nearly linear, and the stress of the specimen reaches the peak first and then plummets, showing a brittle failure. In the range of 0 °C to 25 °C, the specimen undergoes a certain degree of plastic deformation after its peak stress, and then it fractures, showing a ductile failure; (2) As temperature rises, both flexural strength and flexural modulus of the concrete decrease gradually, and deformation capacity increases; as temperature drops, peak strain decreases; (3) For concrete under different temperature conditions, an empirical formula is put forward in this study and it calculates the variations in flexural properties to a good agreement with the test results.
		2022 Vol. 41 (8): 104-112 [Abstract] ( 123 ) PDF (522 KB) ( 180 )

	113	Study on compaction characteristics of anti-seepage material mixed with gravel for core wall of earth-rock dams
		DING Fei, ZHANG Yanyi, YANG Jian, FAN Henghui, DENG Gang, ZHANG Yinqi
		DOI: 10.11660/slfdxb.20220811
		Compaction characteristics of the core wall soil material reflects the compacting effect in the construction of a real dam project. In this work, a mixture of aeolian sandy soil material and granite gravel material is selected for experimental tests on compaction characteristics under the conditions of different water contents, different gravel ratios, and different compacting efforts. For this gravel-mixed soil, the relationship of its dry density versus water content, ratio of gravel and compacting effort is examined. The test results show that with the increase in water content, the compaction curves of the mixed soil present a parabolic relationship with a trend of increasing first and then decreasing. Under heavy compacting effort, the compacted dry density of the soil material increases first and then decreases with the increasing gravel content; while under light compacting, it increases with a nearly proportional and linear trend. For the mixed soil with a fixed gravel ratio under the increasing compacting effort, its compacted dry density increases gradually and tends to converge.
		2022 Vol. 41 (8): 113-120 [Abstract] ( 145 ) PDF (1665 KB) ( 259 )

	121	Ultrasonic combined determination method for setting process of dam concrete
		CUI Bo, WANG Zijun, LIU Changxin, REN Bingyu
		DOI: 10.11660/slfdxb.20220812
		How to determine the setting state of fresh concrete is crucial to the quality control of dam concrete construction. The traditional measurement of concrete setting time uses the penetration resistance method, which is detrimental and difficult to achieve real-time continuous monitoring of the setting. Most of the emerging ultrasonic nondestructive monitoring is a method that adopts a single transmission or reflection, but its measurement is affected greatly by the incident angle, and its calculation of wave velocity requires an accurate determination of the arrival time of the first wave through manual calculations. Aimed at these problems, this paper develops a method of ultrasonic transmission-reflection joint measurement to accurately calculate the setting time of dam concrete. We conduct an experimental study of monitoring concrete setting state, construct a neural network model based on the Levenberg-Marquaredt (L-M) algorithm, and train it using the time point data set determined by energy index. This new method has been applied to the setting test of dam concrete C25 and compared with the reflection method and the transmission method both based on energy analysis, and the transmission method based on wave velocity analysis. The results show the maximum relative error of its setting time calculations is reduced by 2.5% - 18.7%. The correlation coefficients of its calculated initial setting time and final setting time with the real values are 0.89 and 0.96 respectively, verifying its accuracy and theoretical and practical significance in the quality control of dam concrete construction.
		2022 Vol. 41 (8): 121-133 [Abstract] ( 92 ) PDF (3735 KB) ( 430 )

	134	Research on cascaded neural network algorithm for concrete crack detection
		ZHANG Huilin, LI Denghua, DING Yong
		DOI: 10.11660/slfdxb.20220813
		This paper presents a concrete crack detection method based on cascaded neural networks in complex environments, aiming at the problems of the traditional deep learning crack detection method in complex environments: low robustness, poor edge area identification accuracy, and large errors in damage quantification results. In this three-step method, first it uses the improved semantic segmentation model to preliminarily identify cracks in complex environments, and determines roughly a cracking area of interest in the image. Then, it optimizes the rough segmentation image using the mask based on pyramid pooling to accurately capture the context information of the crack edge. Finally, it calculates crack width using the image pixel resolution with the QR code targets and a crack width parameter acquisition algorithm. The test results show that compared with the traditional crack identification, this method improves significantly in the five evaluation indicators－precision rate, recall rate, accuracy rate, F1 score and intersection ratio－and achieves an overall detection accuracy of higher than 95%, thereby realizing the detection and quantitative analysis of concrete cracks in complex environments.
		2022 Vol. 41 (8): 134-143 [Abstract] ( 247 ) PDF (1537 KB) ( 780 )

	144	Water-conveyance functional reliability analysis of aqueducts subject to coupled randomness from structural parameters and excitations
		ZHANG Wei, WANG Bo, XU Jianguo, HUANG Liang
		DOI: 10.11660/slfdxb.20220814
		The reliability of reinforced concrete (RC) aqueduct structures that suffer the influence of various random factors is crucial to the safe operation of water diversion projects. For a large hydraulic RC aqueduct or important water conveyance structure, it is of great practical significance to ensure its water conveyance function reliability under the influence of various random factors. Based on the latest achievements in the field of structural random dynamics and damage failure analysis, a random dynamic analysis method of aqueduct structures is presented in this paper, which considers reasonably the randomness of structural parameters of a large RC aqueduct and the randomness of its seismic excitation. Reliability indexes are formulated according to its water conveyance function requirements; a method is developed to calculate its water conveyance function reliability under combined random conditions. A comparative analysis of the reliability is made systematically in a case study of an aqueduct in operation under the influence of different random factors. The result shows that for an RC aqueduct under combined random conditions, its random dynamic response has more significant variability than that of only the randomness of its seismic excitation considered, and its reliability level is lowered considerably. This reveals the influence of seismic excitation randomness on the response and reliability of an aqueduct structure is obviously greater than that of material parameter randomness. Thus, it is very necessary to consider comprehensively the combined influence of the above two random factors in calculation of the water conveyance function reliability of aqueduct structure.
		2022 Vol. 41 (8): 144-152 [Abstract] ( 88 ) PDF (3014 KB) ( 370 )