Journal of Hydroelectric Engineering

水力发电学报

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The journal is included in the following databases:
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2019 Vol. 38, No. 6 Published: 2019-06-25

	1	Analysis on applicability and influence factors of real-time monitoring compaction indexes for rockfill dam materials ^Hot!
		LIU Donghai, LIU Zhilei, FENG Youwen
		DOI: 10.11660/slfdxb.20190601
		Real-time compaction monitoring has become a technology for effective control on the compaction quality of rockfill dams. However, various types of materials are used in construction of concrete face rockfill dams (CFRD) and they are significantly different in composition and construction technology. Therefore, comprehensive studies are needed of the impact of different construction technologies on compaction monitoring indicators and their applicability to different dam zones. Combining with field rolling tests, we analyzes the influence of rolling direction, roller vibration mode and dam material type on compaction indexes. The result shows that the rolling vibration frequency is the major factor, and that compaction control value (CCV), an index that describes the effect of more harmonic components of roller acceleration, is better adaptable to different CFRD materials. Based on the above analysis, we recommend the method of CCV coupled with its frequency for evaluation and real-time control of the compaction quality of different CFRD materials.
		2019 Vol. 38 (6): 1-10 [Abstract] ( 233 ) PDF (1621 KB) ( 812 )

	11	Earthwork allocation model based on Q-learning algorithm and its application
		WANG Renchao, LI Zongwei
		DOI: 10.11660/slfdxb.20190602
		Earthwork allocation is an important issue in the design and construction of water conservancy and hydropower projects, and traditional methods, such as linear programming, large-scale system decomposition and coordination, and dynamic programming, have some limitations in practice. This paper explores a new method of using discrete Q-learning in reinforcement learning to solve the problems of earthwork allocation. We discuss the construction and solution of a Q-learning model for earthwork allocation problems and verify its feasibility through the analysis of an engineering example. This work would lay a basis for further studies on the balance of dynamic earthwork allocation using reinforcement learning.
		2019 Vol. 38 (6): 11-18 [Abstract] ( 236 ) PDF (542 KB) ( 484 )

	19	Fracture strength of dam concrete and its determination method
		MI Zhengxiang, HU Yu, LI Qingbin
		DOI: 10.11660/slfdxb.20190603
		Prevention of concrete cracking is a core issue in the construction of momentous hydraulic concrete structures, and establishing an accurate fracture criteria and determining the mechanical parameters of concrete are key to cracking risk evaluation and crack stability analysis of such structures. This paper formulates a new concept of concrete fracture strength, and develops a calculation method based on fracture toughness by combining the traditional strength theory with the fracture mechanics. This method can characterize the effect of initial defects in concrete on its macroscopic crack resistance, and it is verified against the measurements in previous studies. The results show that concrete fracture strength can be used as an intrinsic material property in cracking analysis and thus an innovative method for concrete structure design is provided.
		2019 Vol. 38 (6): 19-28 [Abstract] ( 274 ) PDF (408 KB) ( 548 )

	29	5D visual feedback and control of compaction quality of working units of RCC dam
		XING Yue, TIAN Zhenghong, DU Hui
		DOI: 10.11660/slfdxb.20190604
		A five-dimensional (5D, i.e. 3D space plus time and quality parameters) dynamic visual feedback-control system is developed for the compaction quality of roller compacted concrete (RCC) dam working units to meet the requirement for accurate control. First, we develop an accelerated, AutoCAD/OpenGL-based 3D modeling method of dam construction stage for frontline technicians to build 3D information models of dam working units. This method can accurately visualize the dam shape evolved as the construction of a working unit progresses, and display effectively the information of dam body under construction. Then, using real-time compaction parameters collected from concrete placing layers, we construct a compaction degree calculation model of rolling-compaction hot layers based on a back propagation-artificial neural network (BP-ANN), and formulate an intelligent method for evaluating the compaction quality of the entire working area. Thus, digital visualization cloud maps of compaction quality can be displayed in real time on a remote 3D model of compaction layers, and a Web-based online compaction quality report can be generated, guiding the construction workers to remedy those areas insufficiently compacted or conduct a real-time re-evaluation and thereby achieving smart construction. Finally, the applicability and reliability of our system are verified through a construction project.
		2019 Vol. 38 (6): 29-40 [Abstract] ( 218 ) PDF (1983 KB) ( 552 )

	41	Thermal expansion coefficient of ultra high content fly ash mass concrete at early age
		ZHAO Zhifang, ZHANG Guangbo, SHI Tao
		DOI: 10.11660/slfdxb.20190605
		Conventional ultra high volume fly ash (UHVFA) dam concrete is a kind of promising ecological and energy-saving mass concrete, but its thermal expansion coefficient (TEC) at early age is difficult to measure by a standard testing method. In this work, we test the specimens on a temperature-stress testing machine (TSTM) for the benchmark fly ash (FA) concrete and the UHVFA concrete and separate thermal deformation and autogenous deformation under two curing temperature histories: adiabatic mode and temperature matching curing (TMC) mode. The TECs of the two mass concretes at early age are determined by the strain difference and temperature difference at different ages under the two temperature histories, and a time-varying TEC model is constructed. It is shown that at early age, the TECs of the two concretes are time-varying, first growing up to the maximum at the initial setting time, then rapidly decreasing to the minimum and growing again, and finally tending to be stable. In the heating stage the TEC average of UHVFA is greater than that of FA, while it is smaller during cooling. And in the heating stage, the TEC is smaller at both the initial and final setting times. In general, with the increasing volume of fly ash, the TEC shows a decreasing tendency.
		2019 Vol. 38 (6): 41-48 [Abstract] ( 252 ) PDF (999 KB) ( 571 )

	49	Bed roughness calculation method based on resistance characteristics
		CHEN Xuebiao, ZHANG Genguang, WANG Yule, ZHOU Shuang, LIU Yu, XU Xiaoyang
		DOI: 10.11660/slfdxb.20190606
		Bed roughness (Ks) is a leading factor in calculations of sand grant resistance, and its accuracy is crucial to the determination of velocity distribution, bed-load movement, and sediment transport rate. Based on the resistance characteristics and a comprehensive consideration of water and sediment conditions, this paper develops a calculation formula of bed roughness using the variables of sediment median grain size, sediment non-uniformity coefficient, hydraulic radius, and bed slope, including more hydraulic factors than those in previous studies. This formula is verified against measured data and its mean square errors are compared with those of the previous methods. The verification reveals that it is applicable to the uniform and non-uniform sediment cases, and the bed roughness calculations based on non-uniform sediment achieve much higher accuracy than those on uniform sediment. The effect of sand waves on its accuracy is smaller than that of sediment transport.
		2019 Vol. 38 (6): 49-55 [Abstract] ( 266 ) PDF (446 KB) ( 580 )

	56	Eulerian-Lagrangian modeling of riverine fish eggs drifting and improved estimation of spawning scale of fish with pelagic eggs
		YU Kang, CHEN Yongcan, LIN Junqiang, ZHU Dejun, DUAN Xinbin
		DOI: 10.11660/slfdxb.20190607
		To examine the fish resources in rivers and its protection, this paper develops a fluvial egg drift model in the Eulerian-Langrangian approach coupling a traditional 2D shallow water model to a 3D particle tracking model. This egg drift model is capable of simulating river hydrodynamics, 3D movement of fish eggs and their dispersive patterns in natural rivers under advection and turbulent diffusion. Its performance is verified by comparing our simulations with the previously published measurements on laboratory flumes using particle tracking velocimetry (PTV), and a good agreement is achieved. Then, the model is used to simulate a field experiment of egg release and capture in the Ouchi tributary of the middle Yangtze, focusing on analysis of egg transport dynamics, vertical egg mixing, transverse distribution of egg concentration, and the influence of river geography and hydrodynamics. The inaccuracy of traditional methods using cross-sectional averages in estimating the drifting egg resources due to the non-uniformity of transverse distribution is addressed and improved through certain correction in numerical simulations. The improvement is verified against field egg capture data, showing that after correction the simulation errors are reduced significantly. Moreover, the simulations reveal that average egg drift velocities are considerably lower than those of the mean flows, which must be considered in predicting the locations of fish spawning grounds.
		2019 Vol. 38 (6): 56-68 [Abstract] ( 318 ) PDF (2662 KB) ( 866 )

	69	Relationship between U-shaped open channel discharge and deflection angle of draping thin plate
		ZHANG Weile, WANG Wen’e, HU Xiaotao
		DOI: 10.11660/slfdxb.20190608
		To explore the dynamic characteristics of a thin plate draping in open channel flow and its deflection to the flow, a relationship between the flow discharge and plate angle is determined, and flow forces acting on the plate and the moments about its axis are analyzed. With the vertical pressure on the plate assumed to be hydrostatic, an analytical relationship of its deflection angle α versus the channel discharge Q is derived by the momentum theorem and its moment equilibrium. A prototype plate is tested in a U-shaped channel to verify the analytical formula derived. It shows that relative to the measurements, the error in Q calculations is less than 10% at Q > 10 L/s and less than 5% at Q > 17 L/s. Thus, the range of Q for effective measurement is 10-44 L/s. When the shape and size of the plate nearly matches the channel cross-section, a well-defined relationship exists between Q and α. As α increases, the water level drop Δh across the plate decreases gradually and approaches a fixed value (about 3 cm), and the flow under the plate changes from supercritical to subcritical flow regime. With the Reynolds number increasing, the flow resistance R of the plate increases while its resistance coefficient Cd decreases. The plate angle α is related to the drop Δh and coefficient Cd .
		2019 Vol. 38 (6): 69-76 [Abstract] ( 199 ) PDF (487 KB) ( 450 )

	77	Large eddy simulations of hydrodynamic structure in channel bends with large width-depth ratios and variable curvatures
		ZHANG Bingchang, XU Dong, JI Chunning, BAI Yuchuan
		DOI: 10.11660/slfdxb.20190609
		The meandering river, one of the most common types in nature, features various bends where the secondary flow is induced by curvature and interacts with turbulences, and usually develops into a complicated flow structure. Secondary flows are crucial to river evolution and nutrition material transport. Most previous numerical simulations and experiments focus on the small width-depth ratios and constant curvature of channel bends, but natural rivers tend to develop into a large width-depth ratio and variable curvature. This study conducts large eddy simulations (LES) of the flows in continuous sine-generated bends, and examines the hydrodynamic structure of large width-depth ratio bends under large Reynolds number conditions. The results show that at the cross-sections of zero curvature in the transition of two bends, the recirculation zone is the largest, and over the core region of these cross sections the secondary flow is transversely distributed most uniform. In the case of large width-depth ratio bends, this region can expand up to 15.5% of the cross-sectional area. The mainstream in this core region, relative to the small width-depth ratio case, is less effected by the curved boundaries, and the cross-sectional distributions of its time-averaged streamwise velocity component is closer to that in a straight, rectangular open channel, with the velocity peak located vertically very close to free surface and transversely within a range of 0.5-1.0 times the flow depth around the channel centerline. With an increasing width-depth ratio, Z-vorticity near the bend apex is increased, and the influence of bend curvature is extended further downstream. The secondary flow also changes the characteristics of flow turbulences in a meandering river. A larger width-depth ratio leads to less turbulent energy, and turbulent kinetic energy is the lowest in the core of the mainstream while the highest in shear layers.
		2019 Vol. 38 (6): 77-91 [Abstract] ( 224 ) PDF (6691 KB) ( 598 )

	92	Static stability of pump-turbine units in turbine mode
		ZHANG Fei, ZHU Baoshan, ZHONG Dalin, LI Dongkuo
		DOI: 10.11660/slfdxb.20190610
		The S-shape region of pump-turbine units, as the major difference from common turbines, is one of the key factors that cause the instability of unit operation. Previous studies derive the derivatives of unit discharge Q11 and unit torque T11 to unit speed n11 separately. This paper derives stability requirements for pump-turbine units running in turbine mode and reverse pump mode, considering the features of these two derivatives and combining them with the relationship of flow rate Q versus working head H in the two modes for a given guide vane opening. We use the static stability theory to build a relationship of Q versus H that must be satisfied by the working head disturbance factor for stable running in the two modes, and then define a stable turbine-mode working point and a S-shape region.
		2019 Vol. 38 (6): 92-100 [Abstract] ( 218 ) PDF (743 KB) ( 495 )

	101	Pressure fluctuation characteristics of bidirectional pumping system under super-low head operation
		JIAO Weixuan, CHENG Li, YAN Hongqin, JIANG Hongying
		DOI: 10.11660/slfdxb.20190611
		The pumping stations along the Yangtze River have been used for the bidirectional tasks of water diversion and drainage such as irrigation, storm drainage, and water environment control. Influenced by the tidal level in the river, these bidirectional pumping stations often operate near zero head, while the actual flow rates exceed the design value by up to 30%. This leads to an increase in the hydraulic loss of flow passages, a disorder in flow patterns, and a potential of hydraulic vibrations, thereby affecting the operation safety of the pump systems. This study examines the flow behaviors and pressure fluctuations for a low-head pumping station through CFD simulations, and verifies the calculations using scale model tests. The results show that under the super-low head condition, large-scale backflows occur in the blind end of its inlet and outlet passages, and the one at the outlet has a great intensity and causes a significant increase in hydraulic loss. At all the measuring points in the inlet passage, the dominant and secondary frequencies of fluctuations are 6 and 1/8 times the pump rotating frequency respectively. in the outlet, the dominant frequencies are irregular, but the amplitudes at different locations are similar and low-frequency fluctuations are dominant.
		2019 Vol. 38 (6): 101-112 [Abstract] ( 297 ) PDF (2374 KB) ( 535 )

	113	Hydrodynamic performance of new type of combined ducted turbine
		SONG Ke, WANG Wenquan, YAN Yan
		DOI: 10.11660/slfdxb.20190612
		To reduce the flow separation with the ducted turbine and reduce its axial force, this paper presents a new type of combined ducted horizontal axis turbine with ducted flow paths and an analysis on its hydrodynamic performance using computational fluid dynamics (CFD) and towing tank experiments. The influence of the number, width and shape of the ducted flow paths is examined. Results show that compared with the original ducted turbine, the combined ducted turbine can significantly reduce the axial force on the duct and improve the wake flow condition and stability of a turbine system at low tip speed ratios while keeping a nearly fixed power output. And within a certain range, such an effect will become more obvious with the increase in the number or width of flow paths. Of the flow paths in different shapes, a straight passage produces the best effect. The study provides a new ducted turbine design helping reduce flow separation and optimize the turbine and its supporting devices.
		2019 Vol. 38 (6): 113-120 [Abstract] ( 160 ) PDF (2193 KB) ( 460 )