Journal of Hydroelectric Engineering

水力发电学报

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2023 Vol. 42, No. 1 Published: 2023-01-25

	1	Experimental study on impermeability of hydraulic concrete with microorganisms ^Hot!
		MENG Yongdong, HE Zhuqing, CAI Zhenglong, TIAN Bin, XU Xiaowei, WANG Dingjie, DING Yi
		DOI: 10.11660/slfdxb.20230101
		Effective improvement of the impermeability of hydraulic anti-seepage concrete structures is the key to durability enhancing. In this work, we conduct impermeability tests on hydraulic concrete mixed with Bacillus Coriolis, and analyze the influence of the additive concentration on impermeability. Through nitrogen adsorption tests, we examine the micro-pore characteristics of concrete samples, and reveal the influencing mechanism of Bacillus Coriolis on impermeability. The results show the impermeability of concrete can be significantly improved by adding mineralized microorganisms. With the increase in microbial concentration, the water permeability coefficient of the 28 d concrete samples tends to decrease sharply and then slowly; at a microbial concentration of 9.8×107 cells/mL, the decrease of 92% is the largest. Micro-analysis of nitrogen adsorption shows that adding microorganisms into concrete reduces the number of medium- and large-size pores and refines the concrete pore size, and that the peak diameters of the most probable holes are reduced by up to 47.7%. This improves effectively the pore structure in hydraulic concrete and reduces its pore connectivity, thus enhancing its impermeability significantly.
		2023 Vol. 42 (1): 1-8 [Abstract] ( 136 ) PDF (1964 KB) ( 369 )

	9	Deformation separation method and data-driven evaluation of arch dam performance
		GUO Jinhua, LIU Xiaoqing, LI Tongchun, GAO Lingang
		DOI: 10.11660/slfdxb.20230102
		The monitored displacements of an arch dam body are decomposed into two parts: one caused by dam body loading and the other by the constrained effect of dam foundation. Then, a set of equations that take the minimum systematic error of the monitored and predicted values as the objective function, can be established for the two unknowns－constrained foundation displacement and dam body elastic modulus. And they are solved simultaneously from a large body of monitored displacement data combined with PSO to achieve data-driven effect. A case study of a dam body on a complicated dam foundation shows that relative to FEM calculations, the dam body displacements calculated using this new method have relative errors in the range of 1.5%, with the exception of the nodes (with 3% errors) near its interface with the foundation, proving our method is effective and accurate. Application to the Baihetan arch dam reveals that the displacement calculations feature a reasonable spatial pattern of relative errors, and the deformation separation results are close to the real case, which validates our new displacement model.
		2023 Vol. 42 (1): 9-18 [Abstract] ( 111 ) PDF (2736 KB) ( 270 )

	19	Damage analysis of concrete cold joint surface under sulfate wet-dry-salt corrosion cycling
		QIN Yuan, JI Wenzhe, LIANG Da, GUAN Ke, ZHOU Heng
		DOI: 10.11660/slfdxb.20230103
		Groundwater and soils in the western regions of China are rich in sulfate, which impairs concrete structures and reduces their service life. During concrete pouring, a cold joint forms between two concrete layers; on its surface, many micro-cracks and large pores serve as the main channels for salt ions to flow and cause a weakness prone to salt erosion damage. This study conducts experimental compression-shear tests on concrete specimens and examines the adhesion degradation of the cold joint surface and its variations under sulfate dry-wet-salt corrosion cycling, focusing on the joints with pouring intervals of 0.25 d, 0.5 d, 7 d and 28 d under the condition of 0, 30, 90 and 150 cycles. The results show that a longer pouring interval lead to lower adhesion on the joint surface while a shorter one to greater variations in the adhesion, which follow a logarithmic relationship. Within 30 dry-wet-salt corrosion cycles, the effect of pouring interval on the corrosion resistance of the joint surface is insignificant, while this effect increases gradually after 90 cycles. Accelerating adhesion failure on the cold joint surface is possible in the case of a long pouring interval and a large number of cycles.
		2023 Vol. 42 (1): 19-29 [Abstract] ( 108 ) PDF (1883 KB) ( 280 )

	30	Study on stochastic dynamic analysis and seismic effect of face slabs of high rockfill dams
		XU Bin, RONG Zhuo, PANG Rui, ZHOU Yang
		DOI: 10.11660/slfdxb.20230104
		For a high concrete face rockfill dam (CFRD) under strong ground motions, the middle and upper parts of its face slabs usually produce high tensile stress along the slope, possibly resulting in horizontal cracks and leakage. It has been proved that setting permanent horizontal joints in the areas prone to high tensile stress can reduce the stress effectively. However, most of the previous studies on the effect of anti-seismic measures used a single ground motion for deterministic analysis, lacking consideration of the randomness of ground motions. This paper presents a stochastic dynamic method for determining along slope zones with high stress of the face slab, together with a discussion on the length of horizontal joints and an application to a 300 m high dam. The area influenced by horizontal joints and their effect of stress reduction are investigated by using the generalized probability density evolution method and focusing on a specific direction and typical elements, which shows the effectiveness of horizontal joints serving as a new measure for anti-seismic protection from the perspective of probability.
		2023 Vol. 42 (1): 30-39 [Abstract] ( 115 ) PDF (1191 KB) ( 256 )

	40	Ultra-short-term predictions of wind power based on parallel machine learning
		LI Jinlong, WANG Yiming, CHANG Jianxia, JIANG Wenxi, WANG Xuebin
		DOI: 10.11660/slfdxb.20230105
		In view of the intermittent, random and fluctuating characteristics of wind power output and the time-consuming drawback of its previous combined forecasting models, a combined wind power prediction model is developed based on a combination of the parallel technology, ensemble empirical mode decomposition (EEMD), and bidirectional long short-term memory (BiLSTM) neural networks. First, the initial sequence of wind power output is decomposed into a series of intrinsic mode functions using EEMD. Then, a parallel BiLSTM neural networks sub-model array for the intrinsic mode functions is constructed with the help of the multi-process message passing interface, and a Bayesian optimization algorithm is used to calibrate the hyperparameters of each sub-model. Finally, wind power predictions are obtained by synthesizing the parallel sub-model prediction sequences. Example verification shows that this prediction model has certain advantages over the five models compared in terms of one-step prediction, multi-step prediction, and execution efficiency. The results are useful for the formulation of power grid generation plans and the economic operation of power systems.
		2023 Vol. 42 (1): 40-51 [Abstract] ( 188 ) PDF (2004 KB) ( 496 )

	52	Improvement of Soil Conservation Service Curve Number model under different antecedent moisture conditions and rainfall intensities
		LIANG Fengming, WANG Jie, HAO Meng, CHEN Jiadong, LI Jiao, HU Xiaodong
		DOI: 10.11660/slfdxb.20230106
		Antecedent moisture condition and rainfall intensity are key factors that affect the runoff prediction accuracy of the Soil Conservation Service Curve Number (SCS-CN) model. Analyzing how the model behaviors depend on the two factors for different basins plays a crucial role in model improvement. This study uses partial correlation analysis and K-means cluster analysis to improve the SCS-CN model, based on the data of rainfall and runoff from five basins in semi-arid, semi-humid and humid regions. The results show that regrouping the antecedent moisture condition intervals for these basins improves its prediction ability greatly, and reduces its average deviation significantly, increasing the Nash-Sutcliffe efficiency by 42.8% on average. This model can also be improved by introducing the maximum 10 min rainfall intensity, which increases the efficiency to a certain extent and shows an improvement for the semi-arid and semi-humid basin better than that for the humid basin. The revised models have achieved good results for the study basin with an average deviation of less than 7 mm. Except for the Chengcun basin in the non-flood period, the Nash-Sutcliffe efficiency is over 0.93 or an average increase by 89%, and the Root Mean Square error is reduced by 29.2 mm.
		2023 Vol. 42 (1): 52-64 [Abstract] ( 153 ) PDF (5170 KB) ( 235 )

	65	Evaluation of urban river network connectivity by coupling connection number and graph theory
		MEN Baohui, LIU Jingping
		DOI: 10.11660/slfdxb.20230107
		A river network diagram model is constructed for the main rivers and man-made canals to analyze the connectivity of the Luoyang River network under the background of urbanization. Connectivity is evaluated by the five element connection number and calculated using a coupling model of the set pair analysis and graph theory, revealing its value of 1.34 for the Luoyang river network. In the graph model, each of the six canals connecting the river channels are removed separately, and accordingly six connecting schemes are formulated with connectivity values of 1.06, 1.25, 1.23, 1.29, 1.19, and 1.27, respectively. The results show the influence of the six canals on the connectivity of the network can be ranked,from strong to weak: Yellow-to-Luo water diverting canal, connecting canal of Yi River and Luo River, Yellow-to-Chanhe water diverting canal, Zhenhe-to-Jianhe water diverting canal, Zhongzhou Canal, Luohe-to-Yihe water diverting canal. This coupling model realizes a comprehensive evaluation of functional connectivity and structural connectivity. And it can improve, through analysis of the connectivity factors using the set pair potential of five element subtraction, the connectivity of a water system in terms of water volume, reservoir operation capacity, river bank ecology, water quality, etc.
		2023 Vol. 42 (1): 65-76 [Abstract] ( 135 ) PDF (1834 KB) ( 320 )

	77	Study on ecological flows based on high-efficiency and high-accuracy habitat model
		YANG Lu, HOU Jingming, WANG Pan, WANG Tian, CHENG Long, MA Yi, GAO Xunjun, LIU Yuan
		DOI: 10.11660/slfdxb.20230108
		To achieve a harmony of hydropower development and ecological protection, scientific, quantitative, and efficient analysis of the impact of hydropower station operation on river ecosystem has become a hot research topic in water conservancy. This paper describes a high-efficient and high-accuracy habitat suitability model that couples a habitat suitability model with a hydrodynamic model based on the finite volume method using Godunov scheme, and GPU acceleration technology. Using this coupling model, we simulate the spawning habitats under different river discharges, in a case study of an upper Yellow River section downstream of Yehu Gorge, to determine the ecological flow suitable for spawning of the target fish, Gymnocypris eckloni, after completion of the hydropower station. The results show that under the discharges of 87.5 - 139.0 m3/s and 338.0 - 562.5 m3/s, the effective habitat area suitable for reproduction of this fish covers more than 90.0% of the largest habitat area. To ensure a good condition of the spawning habitat, we suggest an ecological flow be around 499.2 m3/s after completion of this hydropower station. The results are useful for ecological protection of the native fish habitats in the upper Yellow River and also for evaluation of hydropower project impacts on aquatic organisms.
		2023 Vol. 42 (1): 77-85 [Abstract] ( 129 ) PDF (2077 KB) ( 303 )

	86	Study on effect of groove length on hydraulic characteristics of backward facing step flows
		ZHANG Weile, WANG Fangfang, WU Shiqiang, WU Xiufeng, XU Zhun, SUN Chenguang
		DOI: 10.11660/slfdxb.20230109
		A numerical simulation method is used to study the effect of groove length on backward-facing step flows at the Reynolds numbers of 6500 and 9000, focusing on the distributions of flow velocity and turbulent kinetic energy and the variations in time-average reattachment distance in the conditions of different groove lengths. The results show that (1) this distance is reduced by the groove, but it is less affected by groove length and tends to a constant value at the length no less than 7 times the step height. This constant distance is 12.0% shorter than that of no groove. (2) At the step section, the distribution of turbulent kinetic energy varies with groove length, and turbulence intensity is increased. With the groove length no less than 7 times the step height, turbulent kinetic energy features an S-shaped distribution, and it peaks at a position of roughly 0.3 times the section height above the step; with a shorter groove length, it peaks at roughly 0.1 times the section height first and then drops to the minimum at roughly 0.6 times the section height. (3) Using the scale factor, an approximate reattachment distance of backward steps, well correlated with the time-average reattachment distance, is calculated to explain the mechanism of turbulence affecting the flows. An increase in turbulence promotes the sinking of the free shear layer and shortens the time for the shear layer to reattach to the downstream wall, thus shortening the time-average reattachment distance.
		2023 Vol. 42 (1): 86-94 [Abstract] ( 115 ) PDF (727 KB) ( 312 )

	95	Key technologies and application of flow field dynamic visualization platform
		LI Wenda, ZHANG Shanghong, HOU Jun, YANG Xiyan
		DOI: 10.11660/slfdxb.20230110
		Reproducing a real-time flow field is an important approach for examining hydrodynamic processes and helping find the laws underlying flow motions, and becomes a challenging hotspot in computer simulation studies. Application of flow visualization technology enables a more direct and complete information acquisition for end users. This study develops a B/S structure channel flow visualization platform with application to the flows in the Bei River navigation channel, focusing on the Image Based Flow Visualization (IBFV) technology. In this platform, integration of dynamic visualization with a cesium framework is achieved by adopting both the render to texture technology and the ping-pong technology－commonly used in general-purpose graphics processing; this viewpoint-based dynamic rendering method can be used to demonstrate effectively the details of layer-dependent flows. In the application, our new method generates a series of coherent images at a high operating rate of 60 frames per second. Thus, it would promote the application of flow field visualization technologies for far-end access through a certain Web-supported system.
		2023 Vol. 42 (1): 95-103 [Abstract] ( 248 ) PDF (4647 KB) ( 263 )

	104	Characteristics of time-series variations and driving factors of Poyang Lake outflows
		MAO Jingqiao, PENG Jirong, CAI Haibin, ZHANG Peipei
		DOI: 10.11660/slfdxb.20230111
		The middle Yangtze River, Poyang Lake, and its five tributaries form a complex "river-lake" system, and understanding the time-series variation characteristics of the lake outflow and its driving factors is key to regulation and improvement of the river-lake relationship. This paper first selects 12 potential drivers of the outflow and illustrates the multi-collinearity among these drivers by combining the correlation coefficient evaluation criterion method and principal component analysis. Then, we construct a mathematical model of the lake outflow based on the random forest regression method, and use it to quantify the relative importance and effects of different potential drivers on the outflow. The results show that 1) no multi-collinearity has been observed among six driving factors－outflows from the Ganjiang, Fuhe, Raohe and Xiushui tributaries, lake stage at Xingzi, and outflow from the Three Gorges reservoir, which can fully characterize the multiple driving effects of the tributaries, lake water stage, and Yangtze mainstream. 2) We reveal that the top three effects come from lake stage, Yangtze mainstream discharge, and Ganjiang River outflow; the influence of the main driving factors is complicated and nonlinear. And relationships among all these six factors are also complicated and their influences are different. This study would deepen our understanding of the relationship underlying this river-lake system and be useful for river-lake regulation.
		2023 Vol. 42 (1): 104-113 [Abstract] ( 127 ) PDF (795 KB) ( 275 )

	114	Nonlinear active disturbance rejection control of hydraulic turbine regulating system considering dead zone
		ZHOU Dongdong, WANG Bin, AI Bo, ZHANG Wenjing, GAO Yuanchen
		DOI: 10.11660/slfdxb.20230112
		An active disturbance rejection control method based on an improved state error feedback law is developed for a hydraulic turbine regulating system with a nonlinear dead zone and mechanical time delay. First, we develop a mathematical model for such systems considering the gap characteristics in the transmission process of its electro-hydraulic servo system, and transform the state space equation with the dead zone and time delay characteristics into a controllable standardized mathematical model through coordinate transformation. Then, a proportional integral derivative (PID) link is introduced to design a new active disturbance rejection controller that can eliminate the chatter in error signals processed by the state error feedback control law. Finally, we analyze the system error equation based on the Lyapunov stability theorem, and prove the convergence of the extended state observer. The simulation results show that this new controller has a better control effect than the PID control or the traditional active disturbance rejection control under various operating conditions, verifying its effectiveness, superiority and practical significance.
		2023 Vol. 42 (1): 114-127 [Abstract] ( 106 ) PDF (893 KB) ( 230 )

	128	Optimization and experimental verification of pivot position of flapping hydrofoil
		HUA Ertian, SU Zhongxin, XIE Rongsheng, CHEN Wanqian, TANG Shouwei, LUO Haitao
		DOI: 10.11660/slfdxb.20230113
		To solve the problem of insufficient hydrodynamic force in plain river networks, a bionic flapping hydrofoil in compound harmonic motions is used to push water under ultra-low head operating conditions. Based on the finite volume method (FVM) and the overlapping moving grid technology, the optimal position of the hydrofoil pivot is determined by using numerical simulations and experimental tests. The result shows that an inverse Karman vortex street appears as the wake of the flapping hydrofoil, and the pivot position affects the deflection degree of the street, the strength of the leading edge vortex, and the time change in its instantaneous state. As the pivot moves towards the trailing edge, the water pushing efficiency rises first and then declines with an optimal value 2% - 5% higher at L = 0.2c than that of the pivot near the leading edge. The hydraulic characteristic curve of a flapping hydrofoil features similar to that of a traditional pump, and its maximum head is lower than 1 m. The maximum head gradually lowers as its pivot moves towards the trailing edge to meet the requirement of ultra-low head conditions.
		2023 Vol. 42 (1): 128-138 [Abstract] ( 88 ) PDF (1580 KB) ( 233 )

	139	Analysis of hydrodynamic and wake characteristics of drag-type horizontal axis hydraulic turbines
		SONG Ke, KANG Yuchi
		DOI: 10.11660/slfdxb.20230114
		Hydraulic turbine is the core equipment for hydropower utilization. The traditional lift-type horizontal axis hydraulic turbine needs a certain flow velocity to obtain an established efficiency, and thus is not suitable in the cases of low flow rates. To expand the application scope, we design two new drag-type horizontal axis turbines with different propeller blade angles based on the Archimedes spiral principle, and investigate their hydrodynamic performance and wake characteristics using the computational fluid dynamics method. The results show that these variable angle designs have larger power coefficients in the tip speed ratio range of 0.5 to 2.0, and their peak value is up to 16% larger than that of the fixed angle. And the power coefficients are also larger than those of lift-type horizontal axis turbines reported previously in the literature; the coefficient is increased by at least 60% at the tip speed ratio of 1.5, for instance. Meanwhile, the variable angle turbine has a smaller thrust coefficient in the whole tip speed ratio range, while its performance fluctuation is more obvious than that of the fixed angle. Flow field analysis reveals that annular spiral tip vortices and strip-shaped hub vortices develop behind the two drag-type horizontal axis turbines, and the variable angle designs make the tracks of tip vortices and hub vortices more continuous and extend longer into the downstream. In addition, the wake recovery of the variable angle turbines are much faster than that of the fixed angle. The results reveal the hydrodynamic and wake characteristics of our drag-type horizontal axis hydraulic turbines, which can be referred to in their optimal design and application promotion.
		2023 Vol. 42 (1): 139-147 [Abstract] ( 135 ) PDF (1465 KB) ( 316 )

	148	Study of numerical prediction method for environmental loads of floating photovoltaic power stations
		XI Kai, HUANG Guozhen, FENG Yukun, CHEN Xi, CHEN Changfu, CHEN Zuogang
		DOI: 10.11660/slfdxb.20230115
		In design of a floating PV power station, the accuracy of its environmental loads assessment is directly related to the safety and cost of its anchorage system. The industrial regulations available cannot give a convincing estimation of such loads due to the large number of floating PV array modules, different supporting structures, different layout modes, and the increasing number of the arrays. This paper develops a numerical method based on multi-scale analysis to predict wind loads, current loads, and wave loads. The geometric model of the array is partly simplified to limit the number of grid elements to 250 million on the basis of numerical investigation and verification to make large-scale numerical calculations possible. Sub-areas with different row and column numbers are selected from the floating array for mutual comparison and confirmation; variations in the loads on each component with the rows and columns of the array are analyzed. The prediction of the loads on the whole array is given based on analysis. The results show that the upstream components produce a shielding effect on the downstream ones, and a wind load secondary peak is formed in the fifth row windward. The loads over the central area of an array basically tend to be stable; evident differences occur in the distributions of wind and current loads over a column. This study solves the problem of how to calculate floating PV power stations with multi-scale, large-scale and direct modeling, and helps improve their anchorage design.
		2023 Vol. 42 (1): 148-158 [Abstract] ( 127 ) PDF (2080 KB) ( 265 )

	159	Analysis of flows and axial forces in gas-liquid mixed pump with balance hole
		GENG Chen, HAN Jiawei, LU Jinling, LUO Xingqi, YAN Sina
		DOI: 10.11660/slfdxb.20230116
		This paper presented the numerical simulation of the two-phase flow in a gas-liquid mixed pump by applying a mixing model. The influence of setting balance holes on the internal flow, performance and axial force under different inlet gas holdups was examined. This study found that the runner axial force reduced significantly under various operating conditions after setting balance holes; high-pressure fluid flowing back from the balance system disturbed the internal flow state, and could destroy and entrain bubbles accumulated in the flow channels. Taking the influence on the performance and axial force into consideration, we found it feasible to balance the axial force by using the balance hole in case of low air content at inlet. The inlet and outlet pressure coefficients of the balance system decreased nonlinearly with the increase of specific area coefficient; an excessive hole diameter will lead to a loss of the pump’s effective volume. Therefore, the optimal diameter should be adopted in design. We further found the amplitude and pulsation of the axial force were relatively small when the balance holes were located on the suction surfaces of the runner blades. This study sheds light on the understanding of the multistage gas-liquid mixed pump modified with the balance hole and provides reference for the design and optimization of its axial force system.
		2023 Vol. 42 (1): 159-168 [Abstract] ( 96 ) PDF (3441 KB) ( 253 )