Journal of Hydroelectric Engineering

水力发电学报

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2023 Vol. 42, No. 3 Published: 2023-03-25

	1	Flow measurement accuracy of sediment-laden open channel flows-taking time-difference ultrasonic flowmeters as examples ^Hot!
		DUAN Yanchong, YANG Yuting, WANG Zhongjing, LI Danxun
		DOI: 10.11660/slfdxb.20230301
		The influence of sediment on the flow measurement accuracy is an important problem in hydraulics. In this study, taking time-difference ultrasonic flowmeters as examples, the potential sediment influence on their measurement accuracy in sediment-laden open channel flows was investigated based on indoor experiments at different sediment concentrations (0 ~ 27 kg/m3, natural sand from the Yellow River irrigation district in Ningxia with medium particle size of 0.015 mm was used). The flow measurement errors were quantified and compared against the benchmark devices of sediment insensitive pipe electromagnetic flowmeter and Parshall flume. The results indicate that ultrasonic flowmeters overestimate the flowrate and the deviation increases with sediment concentration. In the concentration range of our study, the multi-channel box-type ultrasonic flowmeters are insensitive to the sediment concentration and suffer a maximum deviation of 7%, while the single-channel measurements are very poor with a deviation up to 300% - 500% under the influence of sediment.
		2023 Vol. 42 (3): 1-12 [Abstract] ( 160 ) PDF (4969 KB) ( 268 )

	13	Deep learning model guided by physical mechanism for reservoir operation
		ZHANG Wei, ZHENG Yalian, LIU Zhiwu, LIU Pan, LI Mengjie
		DOI: 10.11660/slfdxb.20230302
		Machine learning and other related technologies find increasing applications to extracting manual operation experiences from massive data in the practice of reservoir regulation. However, reservoir operation schemes solely based on machine learning fail to describe reservoir operation with enough accuracy, resulting in outliers in calculation results and a lack of operational experience. This paper constructs a deep learning model guided by the physical mechanism for reservoir operation, taking the water balance constraint, monotonicity constraint, and boundary constraint as the penalty terms of loss functions; data enhancement is used to include the factor of rare flood operations in the data sets of model training and verification. Results show this model is effective in simulating reservoir decisions for conventional operations and rare flood operations. It better satisfies the water balance equation, reduces negative flows effectively, and improves high flow simulation accuracies in comparison with the benchmark model, thus promoting the realization of intelligent reservoir operation.
		2023 Vol. 42 (3): 13-25 [Abstract] ( 242 ) PDF (1326 KB) ( 490 )

	26	Effect of DEM data sources and resolutions on watershed flood simulations
		LI Jianzhu, LI Leijing, ZHANG Ting, KANG Yanfu, ZHANG Bo, FENG Ping
		DOI: 10.11660/slfdxb.20230303
		This study constructs a HEC-HMS model to simulate flood hydrographs to examine the effect of DEM data sources and resolutions on the simulations. We take an ASTER 30 m digital elevation model (DEM) and unmanned aerial vehicle (UAV) 3D tilt photography 7 cm high-resolution DEM as the data sources, and obtain ten DEMs with the resolutions of 1m, 5m, 10m, 20m and 30m by resampling. This method has been applied to 20 flood events in the semi-arid and sub-humid Liulin watershed of the 1995-2021 period. The results show that the model constructed by the 1m resampling DEMs from the 7 cm high-resolution data sources has relatively good performance; its mean relative errors are 16.4% and 15.7% for flood peak flow and runoff depth simulations, respectively, with a mean NSE value of 0.657. For the ASTER 30 m DEMs-based model, its errors are 16.0% and 18.7% and its mean NSE value is 0.646. The other DEMs-based HEC-HMS models, featured with different resolutions and data sources, show little difference in flood simulations.
		2023 Vol. 42 (3): 26-40 [Abstract] ( 167 ) PDF (1381 KB) ( 374 )

	41	Analysis of runoff changes and their causes under climate changes in upper Yarlung Zangbo River basin
		YANG Dawen, WANG Yuhan, TANG Lihua, YAN Dong, CUI Tonghuan
		DOI: 10.11660/slfdxb.20230304
		The Yarlung Zangbo River is a river of rich water resources, but its upper reach runoffs are impacted significantly by climate changes, glacier and frozen soil degradation. This paper develops a distributed eco hydrological model (GBEHM) coupled with cryospheric process modeling to simulate the runoff changes in its upper basin, focusing on an analysis of the variation trends of the hydrological elements in the study area and a quantitative assessment of the impact of climate changes. The results show that from 1981 to 2010, the annual runoff and evapotranspiration in this basin experienced a significant increase, and precipitation increase contributed most to the runoff increase. This period saw a 7% decrease in the permafrost area, a 30.6 cm/10a increase in the thickness of the permafrost active layer, and a 7.3 cm/10a decrease in the annual maximum freezing depth of seasonal frozen ground. The water reserves in the glaciers were decreased significantly at a rate of 1 billion m3/a, while their melting runoff increased at 2.7 mm/a.
		2023 Vol. 42 (3): 41-49 [Abstract] ( 256 ) PDF (1570 KB) ( 571 )

	50	Hydraulic optimization and performance analysis of high rotating speed pump as turbine
		ZHAO Yong, ZHANG Yan, XIAO Yexiang, WANG Chengpeng, WANG Shenghui, ZHANG Jin
		DOI: 10.11660/slfdxb.20230305
		A pump in reverse as turbine has wide application. Besides renewable energy power generation, it can also be used for high-pressure residual energy recovery in high-energy-consumption industries, but generally with a low hydraulic efficiency. To improve its efficiency, the CFD method can be used to optimize its hydraulic performance in combination with the design theory of hydraulic turbines. This study optimizes the impeller of a centrifugal pump as turbine using an orthogonal experimental method, and applies it to seawater desalination energy recovery with a rated speed of 12000 r/min and certain external dimensions limited. We examine the optimized turbine in detail, using experimental and numerical methods and focusing on its hydraulic performance and flow characteristics. Results show that compared with the initial design, the orthogonally optimized design is improved evidently in its impeller’s flow separation and vortex flows and its hydraulic efficiency. The calculations of performance characteristic curves agree well with the tested trends. At the rated speed, with the increasing water head, its hydraulic efficiency increases first and then decreases; its optimal hydraulic efficiency is 85.5%. Under partial working conditions, the farther away from the optimal point, its hydraulic efficiency will be reduced accordingly, and its internal flow state will become more complex.
		2023 Vol. 42 (3): 50-59 [Abstract] ( 113 ) PDF (3626 KB) ( 420 )

	60	Effect of inlet and outlet angles of positive guide vanes on performance of multistage hydraulic turbine
		MIAO Senchun, ZHANG Jiawei, WANG Xiaohui, SHI Fengxia, YANG Junhu
		DOI: 10.11660/slfdxb.20230306
		To reveal the influence of the inlet and outlet angles of positive guide vanes on the performance of a multistage hydraulic turbine, a three-stage centrifugal pump is examined in this study. These angles are derived analytically from the geometric parameters of the impeller and reverse guide vanes by using the equal velocity moment; three kinds of guide vane models are designed. Then, these three new schemes and the initial scheme are numerically simulated and compared based on the computational fluid dynamics code CFX. The results show that the new schemes significantly improve the efficiency under various flow conditions, and widen the range of high-efficiency operation. Among them, Scheme C of the new designs has the best performance, with an efficiency increase by 2.2% under the optimal operating condition. The new schemes also improve the internal flow state of a multistage hydraulic turbine－ more uniform pressure distributions between its positive guide vanes and impeller; smaller vortex area near the inlet of the impeller blades in all 4stages; a significant reduction of the high turbulent kinetic energy area near the inlet. This study would help the design and further optimization of multistage hydraulic turbine guide vanes.
		2023 Vol. 42 (3): 60-69 [Abstract] ( 152 ) PDF (4983 KB) ( 179 )

	70	Multivariable water level prediction model based on convolution radial basis network
		WANG Hailin, ZHU Jialiang, HE Zhengxi, ZHOU Xinzhi
		DOI: 10.11660/slfdxb.20230307
		Accurate prediction of river water levels is of great significance for a high-quality dispatching and management of the water resources in the basin, but the prediction accuracy of a traditional machine learning model is usually difficult to improve further due to the complexity and nonlinear correlation of hydrological data. This paper develops a more accurat4e model of multivariable water level prediction based on a convolution radial basis network. It extracts the spatiotemporal features of hydrological variables fully in parallel, using a multi-layer two-dimensional convolution network; then it achieves high-accuracy predictions of river water levels through a radial basis function network. To verify this model, a numerical experiment is carried out focusing on the predictions of the Qingxi River basin in Sichuan. The results show that compared with four classical models, its root-mean-square error is reduced by 0.039 at least, and the Nash efficiency coefficient increased by 0.056 at least. Compared with the AR-RNN model with the same inputs, its maximum error and root-mean-square error are reduced by 0.348 and 0.017 respectively, verifying its good applicability and effectiveness in basin water level predictions.
		2023 Vol. 42 (3): 70-81 [Abstract] ( 112 ) PDF (3516 KB) ( 431 )

	82	Advances in seismic safety assessment research of high asphalt-concrete core dams
		DENG Mingjiang, SUN Benbo, XU Jia
		DOI: 10.11660/slfdxb.20230308
		Construction of mountain reservoirs and dams will be critical to the key infrastructure projects in Western China for a long time in future, and it is also essential to develop hydropower resources and realize rational allocation and effective regulation of water resources. However, this region is affected significantly by frequent earthquakes and complex operating environments; Dam construction and long-term security are faced with severe challenges. A high asphalt-concrete-core wall dam is a main type of the mountain dams, and its seismic safety during the life cycle is paramount. This paper presents a comprehensive review of the status quo of seismic safety assessment of such dams in China and abroad and its trends in recent years, and examines in detail the problems with seismic safety research, covering several aspects, i.e., nonlinear dynamic constitutive models of asphalt concrete, interface between rockfill and asphalt-concrete-core wall, constitutive models of the interface between asphalt-concrete-core wall and concrete base, high asphalt-concrete-core wall dam-foundation interaction systems, earthquake resistance security assessment, and so on. And we sum up the development trends of seismic safety evaluation theories and methods for high-asphalt concrete core wall dams, and clarify key research directions to help the decision-making of major national engineering construction and sustainable development.
		2023 Vol. 42 (3): 82-91 [Abstract] ( 139 ) PDF (760 KB) ( 309 )

	92	Combination of experimental and empirical methods for dispersivity evaluation of Jingyang loess and its underlying mechanism
		LYU Xinjiang, CHENG Wenchieh, WANG Lin, WU Aifang, XUE Zhongfei
		DOI: 10.11660/slfdxb.20230309
		Dispersive soil is prone to erosion when subjected to significant hydraulic gradients, also referred to as piping failure. In the case of earth dams, such failure can cause a grave threat to residents surrounding. This creates a pressing need for a systematic study on the dispersive mechanism of cohesive soils. In this work, we evaluate the dispersivity of loess specimens taken from Jingyang, Shaanxi, through combining pinhole test, pore water salts test, and empirical formula, focusing on the key factors of dispersivity and the underlying mechanism for loess changing from agglomeration to dispersion structure. The results show that the soil is prone to disperse when its pH value is alkaline and its cation content and exchangeable sodium ion content meet the conditions of CNa+ > 1 mmol/L and ESP > 7%, respectively. Comparison with similar problematic soils in other countries reveals that for the Jingyang loess, its electric potential ξ is mainly influenced by the pH value rather than the clay content or liquid limit; Its relatively low dielectric constant is due to a low liquid limit. Its soil salt content or moisture content can affect the change in the soil-water mixture dielectric constant in the imaginary part, i.e., the change in dielectric loss, but its dispersivity remains significant.
		2023 Vol. 42 (3): 92-102 [Abstract] ( 67 ) PDF (1038 KB) ( 213 )

	103	Study of data-driven methods for predicting soil liquefaction-induced lateral displacement
		ZHANG Yifan, WANG Rui, ZHANG Jianmin, ZHANG Jianhong
		DOI: 10.11660/slfdxb.20230310
		A machine learning-based method is developed based on the liquefaction-induced lateral displacement database of Youd et al., 2002, and applied to the simulation of some soil displacement cases in recent earthquakes. We collect the histories of these cases, and then predict them using the existing engineering experience methods to explore the applicability of the model, showing the Youd 2018 method has a good performance. To obtain an optimal machine learning model, this paper discusses the applicability of five models－BP neural network (BPNN), radial basis neural network (RBF), decision tree (DT), random forest (RF), and support vector machine (SVM). We find that the performance of RF is superior to the other machine learning methods. It has high computational efficiency and good data scalability, and can well reflect the characteristics of the data available to this study. Its prediction accuracy is increased by 18.17% relative to the Youd 2018 method. In addition, a sensitivity analysis is carried out of the influencing factors of liquefaction-induced lateral deformation simulation using the RF model.
		2023 Vol. 42 (3): 103-117 [Abstract] ( 221 ) PDF (984 KB) ( 177 )

	118	Risk management practices of large cascade hydropower projects in lower reach of Jinsha River
		FAN Qixiang, ZHANG Chaoran, HONG Wenhao, GONG Dehong, XU Junxin, WANG Zhilin, YANG Zongli, LIN Peng, WENG Wenlin, LI Guo, ZHENG Bin, LI Ming
		DOI: 10.11660/slfdxb.20230311
		Hydropower development in the lower Jinsha River is of great significance to carbon peaking and carbon neutrality goals. It is a significant contribution to the formation of a clean, low-carbon, safe and efficient energy system and the promotion of coordinated economic and social development in the western regions. Aimed at the challenges in hydropower construction to the "four high, three big, two sides and one strict" management, this paper summarizes the practical experience of hydropower development in this reach, and presents a comprehensive analysis of engineering construction risk and project entity construction management ability. The main results involve engineering construction management concepts, project management modes, green hydropower practices, and industry-college-institute collaborative innovation mechanism, etc. These practices are based on the effective solution of key problems and technical and management challenges, ensuring smooth construction and on-schedule power generation of the hydropower stations in the lower Jinsha River. Our research findings may also be applicable to development and construction of similar river basin projects.
		2023 Vol. 42 (3): 118-131 [Abstract] ( 153 ) PDF (3317 KB) ( 825 )

	132	Study on hydraulic coefficient inversion of unsaturated hydraulic concrete
		HUANG Yaoying, ZHANG Yao, XU Xiaofeng, HE Yiyang, BAO Tengfei
		DOI: 10.11660/slfdxb.20230312
		Concrete materials in most zones of real hydraulic structures are generally in an unsaturated state. When such hydraulic concrete is subjected to water in its service period, unsaturated water absorption occurs, resulting in an increase in its internal water content, so that it will experience moisture expansion deformation that affects the stress and strain state of the structure. In order to improve the accuracy of moisture diffusion coefficient and moisture expansion coefficient of unsaturated hydraulic concrete, this paper presents an inversion method for calculating these coefficients based on a combination of "measured moisture expansion strain - orthogonal design - neural network - numerical calculation". Its feasibility is demonstrated by combining with the laboratory wet expansion test data of unsaturated hydraulic concrete under typical ages. The results show that for the hydraulic concrete immersed in water for 28 days at a water-binder ratio of 0.5, its water diffusion coefficient, shape coefficient and wet expansion coefficient are 3.98×10-12 m2/s, 6.07 and 3.08×10-3, respectively.
		2023 Vol. 42 (3): 132-140 [Abstract] ( 117 ) PDF (1502 KB) ( 253 )

	141	Study on temperature of heterogeneous rock-filled concrete considering layered filling process
		XU Xiaorong, XIAO Anrui, LIANG Ting, JIN Feng, YU Shunyao, QIU Liuchao
		DOI: 10.11660/slfdxb.20230313
		To study the non-uniform spatial and temporal distributions of the early-age temperature of rock-filled concrete (RFC), this study develops a numerical method for simulating heterogeneous RFC, considering the layered filling process of self-compacting concrete (SCC) and discrete rockfill particles. We examine variations of RFC temperature by combining with the data from the prototype experiment of temperature in the Shibahe reservoir. The results show that in the initial stage of SCC pouring and filling, the mixing of concrete with non-uniform placement temperature is completed in several hours. The second stage of the RFC early age, or a synchronous temperature rise process of the rockfill and SCC, takes roughly 2-3 days, during which the rockfill promotes hydration heat absorption with a rockfill temperature rise and a rising rate both lower than those of SCC. After that, the overall RFC temperature tends to be stable and homogeneous with a trend of decreasing slowly. On a lift surface, the rockfill ratio of its different areas may be slightly different, and a higher value occurs in the area with lower average temperature. In summer construction, attention should be paid to the areas near steel formworks, because they feature a high temperature peak and steep temperature gradients due to few rocks in their upstream seepage-prevention layers or downstream triangle areas. Concrete pouring imposes a significant influence on the shallow surface layer of a lower bin, causing a secondary temperature rise of about 6 ℃ and little effect on the layer below the 1.0 m depth. For a lift surface with a short SCC pouring period, an efficient alternative is to use a homogeneous RFC model to simulate the temperature during the construction period, but it should select reasonably an equivalent placement temperature and an equivalent adiabatic temperature rise.
		2023 Vol. 42 (3): 141-152 [Abstract] ( 88 ) PDF (3147 KB) ( 192 )