Journal of Hydroelectric Engineering

水力发电学报

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2022 Vol. 41, No. 12 Published: 2022-12-25

	1	Structural vibration behavior and vibration reduction of bucket foundation wind turbines
		LIAN Jijian, ZHOU Huan, DONG Xiaofeng, JIANG Qi, JIANG Junni
		DOI: 10.11660/slfdxb.20221201
		With the wide application of bucket foundation in China, its performance monitoring in engineering practice has been the key to the operation safety of offshore wind turbines (OWTs). In this study, the vibration displacement of a prototype OWT with a bucket foundation is observed and compared with a monopile foundation OWT. First, based on the measured natural frequencies, foundation stiffness is calculated using the genetic algorithm. Then, the vibration level of the two OWTs are calculated and compared. Results show that of the two foundations, the difference in horizontal stiffness is 7%, while the bucket foundation has a rotational stiffness ten times greater than the monopile. And the bucket foundation OWT features a displacement larger than the monopile type at a wind speed lower than 6 m/s, but above this threshold the trend reverses. At a low wind speed, the occurrence of 3P resonance leads to a larger displacement of the bucket foundation, which, nevertheless, can be reduced by 54.4% through applying an optimized operation strategy. This study shows bucket foundation has superiority in both anti-overturn stability and vibration control.
		2022 Vol. 41 (12): 1-9 [Abstract] ( 149 ) PDF (1367 KB) ( 423 )

	10	Compression characteristics of anti-seepage material mixed with gravel for core wall of earth-rock dam
		ZHANG Yanyi, DING Fei, LI Jian, FAN Henghui, DENG Gang, CHEN Han
		DOI: 10.11660/slfdxb.20221202
		Settlement and deformation of the earth-rock dam body after completion is an important concern in engineering practice. In this work, an experiment was conducted on the compression characteristics of a gravel-mixed soil material－an aeolian sandy soil material mixed with a granite gravel material, focusing on the influence of gravel proportion, stress level, and compactness. The test results show that the compressibility of this mixture is significantly higher than that of the soil; its compression modulus increases with the increasing vertical stress, but with a further vertical stress increase, the increase rate of the modulus decreases gradually. Both gravel proportion and compactness have an evident effect on the modulus. With an increase in gravel proportion or compactness, compression modulus shows a basically increasing trend. However, we also find excessive gravel proportion will reduce compression modulus due to particle breakage caused by the vertical stress of gravel. The void ratio of gravel-mixed soil decreases with vertical stress; it decreases rapidly under low stress while it tends to be stable under high stress. Finally, combining with the variation trends in compression modulus, we investigate the optimal adjustment of gravel proportion in the core wall at different heights of the dam body.
		2022 Vol. 41 (12): 10-18 [Abstract] ( 94 ) PDF (1166 KB) ( 202 )

	19	Incentive mechanism of water conservancy project construction supervision
		ZHANG Huicong, LIU Yang, ZHANG Jiying, XIONG Qian, KANG Yanling, TANG Wenzhe
		DOI: 10.11660/slfdxb.20221203
		Incentive mechanism is increasingly used to promote the construction management of water conservancy projects. It is important how the owner applies incentives to the construction supervision of a water conservancy project for better project delivery. Most of the previous studies in the literature focused on the effect of a specific incentive measure on construction supervision, lacking a holistic study on different incentive measures with empirical evidence support. This paper constructs and verifies an incentive model for water conservancy project construction supervision (WCPCS) that is based on a survey of the Ningxia water conservancy project delivery, aimed at the current common problems and main influencing factors of the incentive mechanism in WCPCS in China. This model is used to reveal the interactions among incentive resources, incentive measures, incentive implementation, and incentive effect so as to improve the performance of WCPCS in China. We develop a performance evaluation and incentive implementation system of WCPCS. Incentive resources and incentive measures on the supervision need to be appropriately combined with learning, innovation, project process and project outcomes, so that the incentives can better guide construction supervision, create motivations for supervisors, and improve project performance. To improve the incentive effect of WCPCS, such measures should be taken, i.e., improving the supervision performance evaluation system, arranging sufficient resources in incentive schemes, and explicating construction supervision tasks and their priorities in incentive measures.
		2022 Vol. 41 (12): 19-26 [Abstract] ( 139 ) PDF (458 KB) ( 255 )

	27	BOA-PID tracking control of unmanned roller for high core rockfill dam compaction under dynamic disturbance
		SHI Mengnan, WANG Xiaoling, WANG Jiajun, CUI Bo, GUAN Shiwei
		DOI: 10.11660/slfdxb.20221204
		Accurate tracking control of an unmanned roller is of great significance to ensuring compaction quality. However, high-core rockfill dams feature a wide range of the particle size of dam materials, an uneven thickness of the paving layer, and a great heterogeneity of the roller working surface; all these factors lead to large dynamic disturbances to roller control. The traditional proportional-integral-derivative (PID) control algorithm uses fixed parameters for deviation correction, and confronts difficulties in timely correction of the tracking deviation caused by dynamic disturbances. Aimed at this issue, this paper uses the butterfly optimization algorithm (BOA) to dynamically optimize the PID control parameters and develops a BOA-PID unmanned roller tracking control method. A body tilt model is constructed to correct the positioning error of the roller under the condition of an uneven working surface; the correction distance is dynamically predicted based on a kinematic model. Then, by taking the minimized correction distance as the goal function, PID is dynamically optimized by BOA including its proportional, integral and differential parameters. Finally, a steering control value for the roller is calculated using the optimized PID, so as to overcome the dynamic disturbance under the complex condition of high-core rockfill dams. This paper gives a case study of the Lianghekou Dam－a large-scale water conservancy and hydropower project in Southwest China－where we have conducted field experiments to verify the effectiveness of this BOA-PID control method. Results show that its correction capability is better than that of GA-PID (genetic algorithm), PSO-PID (particle swarm optimization), DA-PID (dragonfly algorithm), or traditional PID. And it can realize an accurate tracking control of the unmanned roller under the complex condition of high-core wall rockfill dam construction, and reduce the average tracking error of the rockfill material (4.44 cm) and the core wall material (3.32 cm) to a level below 5 cm.
		2022 Vol. 41 (12): 27-37 [Abstract] ( 116 ) PDF (4313 KB) ( 316 )

	38	Energy evolution of concrete with cold joints under sulfate admixture wet-dry cycling
		MEN Bo, QIN Yuan, KOU Jialiang, DANG Faning, LIANG Da, SHI Le, ZHOU Heng
		DOI: 10.11660/slfdxb.20221205
		Concrete specimens with cold joints are manufactured with one-piece pouring and multiple pouring at the intervals of 0.25 d, 0.5 d, 1 d, 7 d, and 28 d to investigate their energy evolution under loads and the cycling of sulfate solution wetting and drying. The cycling effect on the strength and energy evolution are examined by conducting a uniaxial compression experiment and energy calculations. The results show that for the concrete with cold joints, the wet-dry cycling causes a first-increase-then-decrease trend in the time development of its strength, elastic strain energy, dissipation energy at damage stress, and peak stress. All these parameters present a declining tendency with the increasing pouring interval. And as the number of wet-dry cycles increases, the energy storage level Kad at damage stress first decreases and then increases, showing a larger Kad is related to higher susceptibility of concrete to damage. Thus, Kad can be used as an indicator for concrete damage early warning.
		2022 Vol. 41 (12): 38-49 [Abstract] ( 129 ) PDF (2048 KB) ( 307 )

	50	Effects of canyon contraction and reservoir stage on Xiluodu arch dam dynamic response
		YUAN Rui, QIU Yixiang, WANG Jinting, SHI Hongtao
		DOI: 10.11660/slfdxb.20221206
		The Xiluodu arch dam is located in the earthquake-prone southwest region, and its seismic analysis and evaluation is of great significance. In this work, a nonlinear damage analysis model of the arch dam-reservoir water-foundation system is used to analyze the influence of canyon contraction on the dynamic response of this dam under different reservoir stages. The results show that the deformation will aggravate plastic damage to the dam at its abutment and in its middle part near the abutment and the orifices, while a high reservoir stage can alleviate the adverse effect of canyon contraction.
		2022 Vol. 41 (12): 50-58 [Abstract] ( 79 ) PDF (1419 KB) ( 195 )

	59	Study on bonding properties and influencing factors of fiber and cement matrix
		QIN Yuan, LIU Jinge, XU Chengyong, DANG Faning, ZHOU Heng, SHI Le
		DOI: 10.11660/slfdxb.20221207
		The toughness of fiber reinforced concrete comes from the bridging effect of fibers, and the core of this effect depends on the bonding performance of fibers and cement matrix. To explore the concrete toughening mechanism of fibers, we conduct single fiber pull-out tests (SFPT) for polypropylene fiber-reinforced concrete under different conditions of curing ages (0 - 28 d), pull-out rates (1 - 30 mm/min), fiber anchorage lengths (10 - 60 mm), and fly ash contents (0 - 30%). Based on the principle of energy dissipation and the experimental data, we work out a mathematical relationship of the concrete toughness index versus the energy absorption index for fiber pull-out, and develop a calculation and analysis method for the influencing factors of interfacial bond strength based on the generalized grey relational theory. The results show that with the increase in curing age, pull-out rate or fiber anchorage length, the bond strength of the polypropylene fiber-cement matrix interface increases gradually, but the toughness index is better at the curing age of 18 h, and peaks at a pull-out rate of 6 mm/min and an anchorage length of 20 mm. And the interface bonding performance is the best at the fly ash content of about 20%. Based on the general grey correlation analysis method, mathematical correlation is clarified between the interfacial bond strength and the four factors. This study deepens our understanding of fiber-cement bonding and promotes the design and application of fiber-reinforced concrete.
		2022 Vol. 41 (12): 59-68 [Abstract] ( 112 ) PDF (687 KB) ( 268 )

	69	Analysis on characteristics and driving factors of drought risk transmission in Southwest China
		XU Xiaole, PENG Tao, LIN Qingxia, DONG Xiaohua, WANG Youxin, LIU Ji, CHANG Wenjuan, WANG Gaoxu
		DOI: 10.11660/slfdxb.20221208
		The study of drought risk transmission and its driving factors is of great significance for drought early warning and water resources management. We use the standardized precipitation index to analyze the drought characteristics of different time scales in Southwest China. Three risk factors, vulnerability, exposure and resilience, are used to assess regional comprehensive drought risk; And the characteristics and driving factors of drought risk transmission are examined using a Markov chain and random forest algorithm. The results show the spatial patterns of drought duration and severity are roughly the same in different time scales. The order of high to low drought risk in Southwest China is Sichuan, Chongqing, Yunnan, Guangxi, and Guizhou provinces. If an area is adjacent to a low-risk one, its drought risk level will decrease at a relatively high probability, and vice versa. East Asian Summer Monsoon Index and Atlantic Multidecadal Oscillation are the key factors causing the drought in Chongqing, Sichuan, Yunnan, and Guangxi, while Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation are the main causes of drought in Guizhou.
		2022 Vol. 41 (12): 69-79 [Abstract] ( 141 ) PDF (2299 KB) ( 528 )

	80	Characteristics of runoff changes in Ju River basin and attribution analysis
		MU Quanpeng, LU Kexin, YANG Guang, ZHANG Yixin, DONG Jingbing, LI Hefang, WU Qingliang
		DOI: 10.11660/slfdxb.20221209
		Understanding the influencing factors of runoff changes and quantifying their contributions are important for regional planning and rational utilization of water resources. In this paper, a linear regression method, a five-year moving average method, and rescaled range (R/S) analysis method were used to illustrate the variation patterns of hydrological elements in the Ju River basin. The Mann-Kendall mutation test and an ordered clustering method were used to determine the years when sudden changes occurred in the runoff series at the Huangling Station. Then, the runoff series is analysed by using a complementary relationship method based on Budyko's hypothesis, combined with the Slope Change Ratio of Accumulative Quantity (SCRAQ) method. The results show that over the period of 1967-2019, the mean annual precipitation in this basin was on the rise, the annual potential evapotranspiration and annual runoff depth were on the decline, and the annual amount runoff changed abruptly in 1985. The contribution of climate change to runoff change in the Ju River basin was 24.04% and 11.71% by the two methods, respectively, and the contribution of human activities was 75.96% and 88.29%, respectively. Intense human activities such as water conservation measures and coal mining were the main drive of runoff reduction in the basin.
		2022 Vol. 41 (12): 80-89 [Abstract] ( 209 ) PDF (2126 KB) ( 203 )

	90	Multi-objective optimization method for water hammer protection against pump failure in long-distance water transfer systems
		WANG Tiao, ZHAN Hang, WAN Wuyi
		DOI: 10.11660/slfdxb.20221210
		Protection measures of a long-distance water pipeline system are usually necessary to mitigate the water hammer effect since it can cause vibration and rupture. To optimize the water hammer protection measures and improve their cost and reliability, a multi-objective optimization method is developed based on the Random Forest (RF) algorithm and Non-dominated Sorting Genetic Algorithm-II (NSGA-II). First, a hydraulic transient model based on the method of characteristics is used to obtain an expected sample set; based on this set, an RF prediction model is used to establish the relationships between the optimization variables and the optimization objectives. Then, a multi-objective optimization model is constructed and used to find the Pareto frontier solution set, by taking the highest water hammer pressure, the highest dimensionless reversal speed, and the lowest protection cost as its objective functions. This study shows our method can quickly generate optimized protection schemes that balance the requirements of different targets, thus significantly improving the design of water hammer protection for long pipeline systems.
		2022 Vol. 41 (12): 90-99 [Abstract] ( 96 ) PDF (988 KB) ( 394 )

	100	Parameter sensitivity analysis of dynamically coupled one-dimensional morphodynamic model. Case study of lower Yellow River
		CHENG Yifei, XIA Junqiang, ZHOU Meirong, LOU Shujian, LI Dongyang
		DOI: 10.11660/slfdxb.20221211
		Some parameters used in the numerical simulations of fluvial process are usually determined empirically, but their effects have not been examined quantitatively in previous studies. This paper describes a 1D morphodynamic model based on the dynamical coupling of flow and sediment transport, and discusses its simulations of flood routing processes in the lower Yellow in the 2020 flood season. Simulation results indicate (i) time variations in water level and discharge are accurately reproduced, with Nash-Sutcliffe Efficiency Coefficients (NSEs) larger than 0.85 and RMSEs less than 15% of the corresponding mean values. (ii) Although the simulated peak sediment concentration is larger than its measured value, an insignificant difference exists in the patterns of simulated and measured hydrographs. (iii) The calculated volume of riverbed deformation is close to its value measured using the method of cross-sectional riverbed topography. The global sensitivity analysis method proposed by Sobol is adopted to evaluate the effects of some input parameters on the simulations, by taking the NSEs of hydrological indicators at the hydrometric stations as the objective functions. Our findings indicate the importance of an input factor depends on the choice of objective functions. Comparison of sensitivity indexes calculated using different objective functions reveals comprehensive roughness is most sensitive among all the input parameters. When the objective function is the NSE of sediment concentration, the parameters of higher first-order index and total index values are the coefficient of the sediment transport capacity formula and the exponent for recovery coefficient calculation. Generally, a certain parameter combination has quite different sensitivity behaviors under different objective functions, while different parameter combinations could generate comparable effects under the same objective function. Global sensitivity analysis demonstrates the individual effects of different parameters and their interactive effects on the model results, helping improve model calibration for simulations of fluvial process.
		2022 Vol. 41 (12): 100-110 [Abstract] ( 72 ) PDF (1398 KB) ( 299 )

	111	Mobile surface flow field measurement technology and its application
		WANG Hao, KONG Xiangju, GONG Yumin, YANG Feiqi, FU Dabao, WU Wei
		DOI: 10.11660/slfdxb.20221212
		A flume experiment of flows around a bridge pier and bed load transport is conducted to analyze the turbulent structures using an innovative method of surface flow field measurement. In this experiment, move shooting is carried out with a high-speed camera moving along the flume, and the images are clipped out through intelligent identification of the coordinates of ground control points. The technologies of particle tracking velocimetry (PTV) and feature matching velocimetry (FMV) are both used to calculate the instantaneous flows, and then a large area of surface flow field is obtained through meshing and interpolation in the measurement region. The results show (1) this method improves the accuracy and dimensions of surface flow field measurement and broadens its application condition. (2) The FMV method can identify more accurately the flow details in the zones of high rotation intensity beside and behind the cylinder, and its measurements of the average velocity profiles are more consistent with the flow characteristics. (3) We have observed that during bedload movement, the time-average velocity on the turbulent surface still features a high-low alternating streaky structure, with the high and low velocity streaks corresponding to the sand ridge and sand trough respectively. This proves the turbulent flow and the bed form interact to form a stable time-average structure, and also verifies the rationality of the large-scale streamwise vortex model.
		2022 Vol. 41 (12): 111-121 [Abstract] ( 83 ) PDF (6591 KB) ( 260 )

	122	Study on runaway characteristics of tubular turbine for residual pressure power generation
		WANG Peng, GAO Jiawei, LUO Xingqi, LU Jinling, XUE Qiyao, ZHU Guojun
		DOI: 10.11660/slfdxb.20221213
		As tubular turbine power generation technology develops, wider application is found in industries to recover the residual pressure energy of circulating water systems. This paper combines the 1D method of characteristics (MOC) and the 3D computational fluid dynamics (CFD) method to develop a coupling method for simulating the flows in a pipeline network equipped with a tubular turbine. We focus on the simulations of the runaway process in the real system and an analysis of its flow and runner stress characteristics. The results show that the time required to switch from the steady state to the runaway state shortens as the moment of inertia decreases. For the pressure fluctuations at the monitoring points in the runner and draft tube sections, their amplitudes take greater values at the runner blade frequency and its higher harmonics. During runaway, the axial force on the runner decreases greatly, while the radial force increases greatly and oscillates violently; an evident alternating trend appears in the blade surface pressure, and a negative pressure zone occurs near the blade edge on its inlet side. And large vortices develop gradually in the draft tube and diffuse towards the pipe wall along the main flow.
		2022 Vol. 41 (12): 122-134 [Abstract] ( 103 ) PDF (3408 KB) ( 209 )

	135	Model for predicting deterioration trends of hydropower units based on machine learning
		LAN Jiafa, ZHOU Yuhui, GAO Zeliang, JIANG Ben, LI Chaoshun
		DOI: 10.11660/slfdxb.20221214
		Hydropower units deteriorating poses a significant effect on the safe and stable operation of hydropower stations and even on power grid systems; accurate analysis of their operation status needs an accurate prediction of the deterioration trend. This paper presents a hybrid model for predicting this trend based on the extreme gradient boosting (XGBoost) algorithm, the variational mode decomposition (VMD) algorithm, the bidirectional gated recurrent (BiGRU) neural network, and the attention mechanism (AM). First, we use the XGBoost algorithm to construct a health state model of hydropower units considering the influences of working head, active power, and guide vane opening. And this model is applied to predict the deteriorating trend in a period of several years. Then, we decompose the deteriorating trend using VMD and obtain several intrinsic model functions (IMF) that are relatively stable; for each IMF component, we construct a BiGRU-AM model. Finally, all the components are superimposed to give the final trend prediction. Application in a case study shows our method can accurately describe the deterioration trend of hydropower units and improve the accuracy of unit deterioration predictions significantly.
		2022 Vol. 41 (12): 135-144 [Abstract] ( 200 ) PDF (1803 KB) ( 289 )

	145	Joint noise reduction and feature extraction of acoustic emission signals for hydraulic turbines under cavitation
		LIU Zhong, WANG Wenhao, ZOU Shuyun, LI Xianwei, ZHOU Zehua
		DOI: 10.11660/slfdxb.20221215
		Understanding the acoustic emission signals from hydraulic turbines under flow cavitation and its variations with cavitation intensity is essential for monitoring cavitation. To overcome the difficulty in feature extraction from acoustic signals due to noise pollution, this paper develops a feature extraction method based on noise reduction through adaptive local iterative filtering and singular spectrum analysis, and on intrinsic time scale decomposition combined with feature parameters. First, an acoustic signal is initially denoised using the adaptive local iterative filtering combined with correlation coefficients to filter out evident noise components; the remaining components are reconstructed and further denoised via singular spectrum analysis. Adding the resulting signals to the trend component completes the whole noise reduction. Then, an intrinsic time scale decomposition algorithm is used to decompose the noise-reduced signal, screen out its effective components, and calculate their absolute energy and relative energy entropy. Finally, their variation trends with the cavitation coefficient are examined. The results show the variations in absolute energy and relative energy entropy with the cavitation coefficient manifest better regularity, offering an effective indicator of the developing status of hydraulic turbine cavitation.
		2022 Vol. 41 (12): 145-152 [Abstract] ( 93 ) PDF (924 KB) ( 176 )

	153	GMM-DBSCAN multi-scale cleaning of vibration signals from hydropower units in complex operating conditions
		LIU Yi, LIU Wei, SHI Yousong, ZHOU Jianzhong, ZHANG Yongchuan
		DOI: 10.11660/slfdxb.20221216
		Most of the vibration monitoring signals of hydropower units contain a large amount of abnormal data, which severely affect the assessment and prediction of unit health status. Considering the relationship between the unit vibration and its working condition, this paper presents a multi-scale cleaning method of unit vibration signals based on Gaussian Mixture Model and Density Based Spatial Clustering Applications with Noise (GMM-DBSCAN). First, DBSCAN is used to clean initially the vibration anomalies in the whole range of working conditions, and GMM is used to calculate the probability of different working conditions and divide their intervals. Then, for each of the intervals, a density clustering cleaning threshold for DBSCAN is calculated using its probability density, and its abnormal vibration data are cleaned. This method has a cleaning rate of abnormal data of up to 6.3‰, which has been verified using the vibration data monitored at the Pubugou hydropower station under the different working conditions of its one-year operation. Meanwhile, artificial anomaly data are used to verify the method. The results show the method can effectively clean out the isolated outliers and dense abnormal points of unit vibration signals, thus improving the health status evaluation and prediction of hydropower units.
		2022 Vol. 41 (12): 153-162 [Abstract] ( 131 ) PDF (3309 KB) ( 415 )