Journal of Hydroelectric Engineering

水力发电学报

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2021 Vol. 40, No. 11 Published: 2021-11-25

	1	Spatiotemporal water-sediment variations and geomorphological evolution in wide-floodplain transitional reach of lower Yellow River
		ZHANG Jinliang, LIU Junzheng, BAI Yuchuan, XU Haijue, LI Yan
		DOI: 10.11660/slfdxb.20211101
		The section from Gaocun (GC) to Taochengpu (TCP) of the lower Yellow River (LYR) is a typical wide-floodplain transitional reach, featured with a complex channel-floodplain system and severe development into a secondary perched channel. This study conducts a detailed investigation of the relationship between spatiotemporal water-sediment variations and geomorphological evolution observed in this reach, using its historical bathymetric data and the cross-section method. The results show that during the operation of Xiaolangdi reservoir, the main channel was continuously scoured, causing narrower and deeper main channels, a decrease in river cross-sectional geomorphic coefficient, and an increase in the bankfull area mostly by more than 200%. In recent years, however, these trends have been significantly weakened－the main channel was slightly widened horizontally and deepened vertically between GC and Sunkou (SK), while mainly deepened vertically between SK and TCP. In the GC-TCP reach, the channel-floodplain system has gradually switched from sedimentation to erosion patterns, with the resulted erosion rate of roughly 0.07 m/a of its main channel and 0.002 - 0.008 m/a of its floodplains; its cumulative erosion volume during 2000 - 2016 was around 2.251×108 m3. The lateral slope of floodplains increased in time, and its spatial distribution was concentrated between 0.5‰ and 2‰.
		2021 Vol. 40 (11): 1-12 [Abstract] ( 268 ) PDF (4402 KB) ( 752 )

	13	Experimental study on three-dimensional topography and flow structure around bridge piers under local scour
		CHEN Ming, PENG Guoping, WANG Hao, XU Dongze, LI Jian
		DOI: 10.11660/slfdxb.20211102
		In this study, a laboratory experiment was conducted to examine the behaviors of flow scour around one bridge pier and two bridge piers under different flow conditions. The SFM method was used to achieve three-dimensional reconstruction of the scour pit topography; A PIV system was adopted to measure the two-dimensional flow fields. We also present a quantitative analysis of the coupling relationship between the flow structure and scour topography. The results show (1) Three-dimensional reconstruction of scour topography can be well completed by the SFM method. The scour pit is an irregular inverted cone shape, with the largest depth in front and both sides of the model and a hump shaped sand dune behind it. (2) As flow intensity increases, the depth and diameter of the scour pit are increased linearly toward a parabolic shape, and its area and volume are also increased. The sand dune behind the pit grows in length and height, and its tail fin angle decreases. (3) The deep scour pit can be related to the downcutting by large flow shear. Large-scale streamwise vortices from both sides of the bridge pier extend to the downstream, promoting the formation of inclined grooves behind the pit. The shed vortices are weakened along the flow, and the sediment carrying capacity is reduced, resulting in sediment accumulation downstream of the pier.
		2021 Vol. 40 (11): 13-24 [Abstract] ( 143 ) PDF (7976 KB) ( 143 )

	25	Applicability of correlation coefficient information criterion to hydrological dependence models and its validation
		HUO Jingqun, XIE Ping, SANG Yanfang, WANG Gangsheng, LI Yaqing, NIU Jingyi
		DOI: 10.11660/slfdxb.20211103
		Dependence variation, an important feature of hydrological variation, can be described using autoregressive (AR(p)), moving average (MA(q)), and autoregressive moving average (ARMA(p, q)) models with p and q standing for the orders of autoregression and moving average, respectively. However, application and accuracy of these models depend on effective determination of their orders. Correlation coefficient information criterion (RIC) is adopted in previous studies to determine the order of an AR(p) model, where its fitting is assessed by the mean square error and its complexity is quantified based on information entropy. This study examines the applicability of RIC criterion to MA(q) and ARMA(p, q) and evaluate its performance. For the MA(q) models (q ≤ 3) and ARMA(p, q) models (p+q ≤ 3), our statistical experiments show its accuracy is much higher than those of the BIC and AIC criteria in determining the model orders. We demonstrate it is applicable to MA(q) and ARMA(p, q) in terms of multiple observed hydrological series.
		2021 Vol. 40 (11): 25-38 [Abstract] ( 123 ) PDF (716 KB) ( 396 )

	39	Simulation-based evaluation on layout of online water quality monitoring stations
		HSIAO Shihting, WANG Zhongjing
		DOI: 10.11660/slfdxb.20211104
		With the increasing demand for continuous water quality monitoring, the layout of online water quality monitoring stations becomes a more significant issue. This study uses the Hydrologic Simulation Program Fortran (HSPF) model to simulate the quantity and quality of water in the Tamsui River basin, Taiwan. Of the nine hydrological stations compared, most have a Nash-Sutcliffe efficiency coefficient greater than 0.7, and all have a correlation coefficient greater than 0.7. At most of the 27 water quality stations compared, the symmetric mean absolute percentage errors are below 25% for the simulations of biochemical oxygen demand, ammonia nitrogen, suspended solid, and dissolved oxygen. Based on the change rate and substandard rate of water quality, we suggest a concept of water quality-sensitive river section to determine a prior arrangement of the online water quality monitoring locations. We point out the shortage of the existing monitoring locations and recommend to add a new station separately at Sansia Bridge on the Sansia Tributary, Baoqiao Bridge on the Jingmei Tributary, and Jiangpei Bridge on the Keelung Tributary.
		2021 Vol. 40 (11): 39-51 [Abstract] ( 131 ) PDF (4959 KB) ( 385 )

	52	Stability evaluation and decision-making on cascade hydropower stations’ compensation benefit allocation schemes
		LI Yinghai, WANG Li, LI Qingqing, TU Yulyu, NIE Panpan
		DOI: 10.11660/slfdxb.20211105
		To optimize compensation benefit allocation schemes for cascade hydropower stations, we consider the stability of different schemes and the conditions of decision-makers affected by psychological factors, and suggest a propensity-to-disrupt (PTD) value for evaluating the stability. Then, we construct a decision-making index system that is based on the allocation proportion, power generation benefit, and PTD value of each hydropower station, and develop an improved ideal point decision-making based on the regret theory. This method along with the index system is verified through application to optimizing the compensation benefit allocation schemes for the cascade hydropower stations of Sanliping, Siping and Guoduwan in the Nanhe basin of the middle Hanjiang River.
		2021 Vol. 40 (11): 52-58 [Abstract] ( 153 ) PDF (418 KB) ( 339 )

	59	Investigation on flow and noise characteristics affected by cavitation in low specific speed centrifugal pump
		ZHANG Yongxue, JI Kaizhuo, HE Tao, YUAN Zhiyi, ZHANG Jinya
		DOI: 10.11660/slfdxb.20211106
		To understand the effect of cavitation on the flow acoustics of a low specific speed centrifugal pump, this study examines the characteristics of pressure fluctuation and flow noise under different cavitation numbers by combining numerical simulations with experimental measurements, focusing on analysis of the frequency domain characteristics of pressure fluctuations and the frequency responses of sound pressure at typical positions. The results show that as cavitation develops, low-frequency broadband fluctuations in the pump are intensifying. At critical cavitation, the 1/6 rotation frequency becomes dominant in pressure fluctuations at impeller inlet and in the volute region it becomes a significant secondary frequency while the blade passing frequency remains dominant. Pressure fluctuations caused by rotor-stator interaction is the major source of flow noise, and noises induced by cavitation are broadband concentrating on a high-frequency band of 1000-2000 Hz. As cavitation develops, the sound pressure level at the characteristic frequency drops under the action of impeller rotating dipole sound source while it rises under the action of volute dipole sound source, and the characteristic frequency at the high harmonics of blade passing is gradually submerged in a high-frequency broadband. This study lays a basis for further study of the flow and sound behaviors and for reduction of cavitation vibration and noise in low specific speed centrifugal pumps.
		2021 Vol. 40 (11): 59-71 [Abstract] ( 121 ) PDF (5008 KB) ( 493 )

	72	Study on optimization method of two-blade sewage pump impellers based on response surface model
		JIANG Denghui, ZHOU Peijian, WANG Lei, WU Denghao, MOU Jiegang
		DOI: 10.11660/slfdxb.20211107
		To improve the performance of sewage pump impellers, this study applies a response surface model to optimizing the three main design parameters of the impellers based on the orthogonal tests of three factors and three levels. Comparison of the external characteristic curves between the optimized model and the original model reveals that relative to the latter, the former has a wider head range, a higher efficiency, and a wider high efficiency range; it is featured with smaller low-pressure zones of smoother and more even internal flows. The energy loss of the pump under different working conditions is calculated using the entropy generation theory. The results show that entropy production in the impeller of the optimized model is significantly lower, while its distribution pattern in the volute is not much different from that of the original model. At low flows, the zones with a high entropy production rate are mainly concentrated on the pressure side of the blades and near the blade outlet; as the flow increases, the energy loss gradually decreases and the high entropy production zones shift to the volute outlet and the diaphragm. The dynamic and static dryness of the volute involves the impinging and return of high-speed water jets on the volute wall, causing the major part of energy loss in the pump. It is found that the entropy generation distribution of the original model follows a pattern similar to that of the optimized model, while the high entropy generation zones and the generation rate are both significantly larger.
		2021 Vol. 40 (11): 72-82 [Abstract] ( 128 ) PDF (4774 KB) ( 334 )

	83	Research and design of active temperature control system for hydraulic concrete in service period
		WU Zhengqiao, LU Xiaochun, CHEN Bofu, LV Congcong, DU Bin
		DOI: 10.11660/slfdxb.20211108
		Temperature of hydraulic concrete in service period is not controllable under the measures of early temperature control and later thermal insulation. To reduce the temperature gradient near a concrete surface and prevent temperature cracking, we develop a method for active control of hydraulic concrete in service period. We construct a temperature control system and examine the buried depth and spacing of its temperature control pipelines and its regulated temperature, considering temperature-humidity coupling in the regulation and applying a measure based on the principle of minimizing temperature-humidity strain. The results show active temperature control can effectively reduce the adverse strain caused by a sudden drop in ambient temperature. And the best temperature control effect and lowest temperature-humidity strain are achieved at a buried depth of 0.3 m, pipe spacing of 0.3 m, and a regulated temperature drop up to 36.5%.
		2021 Vol. 40 (11): 83-90 [Abstract] ( 82 ) PDF (2835 KB) ( 279 )

	91	Method for determining real strength of full-graded low-heat cement concrete
		GAO Xiaofeng, HU Yu, YANG Ning, WU Kun, ZHONG Yuehui, TAN Yaosheng, LI Qingbin
		DOI: 10.11660/slfdxb.20211109
		Real strength parameters of full-graded aggregate concrete are a basic condition for accurate analysis on the working behaviors of a dam structure. This paper describes a method for determining the real strength of full-graded low-heat cement concrete. In this method, we examine the strength test results of natural-cured cast-in-site dam concrete by the maturity method, and determine a strength conversion relationship between full-graded concrete and wet-sieved concrete. Then, an equation is obtained for predicting the strength of wet-sieved concrete through strength tests of the concrete cured in the environmental chamber under constant temperatures. Finally, we establish a real strength prediction equation using the conversion relationship already determined. Verification and application results show that the prediction equation meets the practical engineering needs of dam construction, and that relative to traditional methods, it provides calculations closer to the real strength parameters of full-graded low-heat cement concrete.
		2021 Vol. 40 (11): 91-104 [Abstract] ( 183 ) PDF (578 KB) ( 350 )

	105	Simulating multi-dimensional fracture parameters of rock mass slopes using ensemble generative adversarial networks
		ZHAO Wenchao, HAN Shuai, LI Mingchao, LI Mingze
		DOI: 10.11660/slfdxb.20211110
		Random characteristic rock fractures are vital to stability analysis of the rock mass on slope in hydraulic engineering, but previous methods are based on a univariate or bivariate statistical models and neglect the dependencies between different fracture parameters. This paper presents a new artificial neural network method for joint simulations of the multi-dimensional parameters of such rock fractures, namely ensemble wasserstein generative adversarial network (E-WGAN) that is based on the generative adversarial networks and ensemble learning. Compared with the traditional methods, this method improves the description of the multi-dimensional distribution characteristics of the fractures. Through examining a set of fracture data for the rock mass cases of three parameters (trace length, strike, and aperture), we show it can accurately model the three variates and their relationships that the traditional methods fail to express. A comparison of the discrete fracture networks generated from simulation samples shows that the trace maps simulated using E-WGAN samples are closer to the real trace maps. Besides, this algorithm is also applicable to higher dimension cases in geological analysis and has a broad prospect of application in rock mass analysis.
		2021 Vol. 40 (11): 105-114 [Abstract] ( 113 ) PDF (2343 KB) ( 413 )

	115	Mobile augmented reality visualization of high arch dam construction simulations based on simultaneous localization and mapping optimization
		REN Bingyu, LU Xun, WANG Xiaoling, WANG Dong, WANG Jiajun, YU Jia
		DOI: 10.11660/slfdxb.20211111
		At present, simulation visualization methods based on the augmented reality (AR) of high arch dam construction have drawbacks in limited visualization angles and poor system integration. Mobile AR has the advantage of diversified interaction modes but suffers relatively large errors in camera registration. This paper presents a new mobile AR method for visualizing high arch dam construction simulations based on optimization via simultaneous localization and mapping (SLAM). This new visualization system calculates accurately the initial camera registration parameters based on SLAM and the 3D and 2D imaging relationship of the target, and realizes real-time camera registration through ARCore motion tracking. Application to high dam construction shows that it improves the overall accuracy in initial camera registration by 97.6% against the traditional sensor method, and its average error in mobile camera registration is only 0.275 m, thus enabling its success in multi-directional spatial decision analysis.
		2021 Vol. 40 (11): 115-128 [Abstract] ( 196 ) PDF (7495 KB) ( 134 )