Journal of Hydroelectric Engineering

水力发电学报

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2016 Vol. 35, No. 10 Published: 2016-10-25

	1	Changes in runoff and sediment loads of the Yellow River and its management strategies
		HU Chunhong
		DOI: 10.11660/slfdxb.20161001
		The key problem in the management of the Yellow River stems from its distinct characteristic, namely the insufficient runoff and excessive sediment loads lacking sufficient coordination, which causes complexity and difficulty in management. This paper examines the changes in runoff and sediment loads of this river and its characteristics of fluvial process in recent decades, based on a review of its management history. Then, we describe a strategic thinking of river management that would be effective in the existing water and sediment condition of the river to cope with its various new features, such as sharp decline in runoff and sediment loads, river channel shrinkage, intensified ‘secondary suspended river’, and increasingly prominent contradiction between floodplain reclamation and river harnessing. Our strategy in managing the Yellow River is to regulate its relation between water and sediment and improve the lower channel, under which several engineering measures should be adopted: construct a river regulation system for water and sediment control, reconstruct and maintain the primary channel with sufficient water and sediment transport capacity, lower the Tongguan elevation in the middle reach, improve the river channel in the lower reach, and stabilize the flow paths in the river mouth. The strategy and measures would provide a useful support for comprehensive management of the Yellow River.
		2016 Vol. 35 (10): 1-11 [Abstract] ( 297 ) PDF (1531 KB) ( 1289 )

	12	Three-dimensional numerical simulations of flows over spillway dam using accurate river terrain
		QI Lan, CHEN Hui, FEI Wencai, LIU Donghai
		DOI: 10.11660/slfdxb.20161002
		This study has developed a three-dimensional CFD numerical method for simulation of the flows over a spillway dam using accurate river terrain. We used the CATIA design platform to construct a 3-D reservoir model for the Yujiahe project of Hubei, which combined the detailed geometry of buildings and structures with river terrain and captured the geometric details of spatial arrangement of a real hydraulic project. An RNG k-epsilon turbulence model and VOF method for tracking free surface were adopted. Flow velocity, water flow regime, and pressure on dam surface in the conditions of flow rates of 1669, 1199 and 728 m3/s were simulated. Comparison and analysis showed a good agreement of modeling results with the measurements of our scale model tests and verified the model. This study demonstrates the advantages of the new method in simulation of 3-D flows over complicated river terrain.
		2016 Vol. 35 (10): 12-20 [Abstract] ( 331 ) PDF (1951 KB) ( 669 )

	21	Spatio-temporal water quality variations and identification of surface water pollutant sources in Bohai Bay
		ZHAO Haiping, LI Qingxue, TAO Jianhua
		DOI: 10.11660/slfdxb.20161003
		This study examined spatial-temporal variations of water quality and potential pollutant sources in the surface water layer in the offshore areas of Bohai Bay, China, based on 7,488 sets of experimental data collected for 13 water quality indicators at 12 sites three times yearly from 1995 to 2010. A multivariate statistical approach was comprehensively applied, including cluster analysis, discriminant analysis, principal component analysis, and factor analysis. The data series of 16 years were grouped into three clusters: cluster A at early stage of nutrient pollution dominant (1995-2001 with 1998-1999 excluded), cluster B at middle stage of organic contamination dominant (2007-2008), and cluster C at late stage of land-based pollution and human activities dominant (1998-1999, 2002-2006 and 2009-2010). In spatial variation, human activities had more serious impact on the nearshore stations; oil and nutrients pollution was more serious in the marine culture areas. This study shows that the comprehensive approach of multivariate statistical methods is effective and useful in water quality investigation of the Bohai Bay offshore areas and our findings would help further study of water ecological environment in this area.
		2016 Vol. 35 (10): 21-30 [Abstract] ( 220 ) PDF (1124 KB) ( 564 )

	31	Water temperature and ice conditions of high-dam reservoirs in northwestern cold and arid regions
		ZHOU Chenyang, LIANG Ruifeng, XIAO Yao, LI Kefeng
		DOI: 10.11660/slfdxb.20161004
		A vertical one-dimensional water temperature and ice condition model and a longitudinal one-dimensional water temperature model have been developed in this study to explore the influence of reservoir construction on water temperature and ice conditions in the northwestern cold regions. These models were applied to a case study of the Huangcangsi reservoir and its downstream river channel, and different cases of reservoir operation were examined and compared with the natural condition. The results show that this reservoir is the type of thermal stratification with inversion profiles of its water temperature behind the dam in winter, and hence it produced certain effects of weakening ice formation. In comparison with the natural river, the start time of frazil ice was delayed by about one month; the lasting period of ice condition was cut down by roughly 20 days; the maximum ice thickness was reduced to 0.49 m from the corresponding value of 0.76 m in the natural condition. As a result, no ice condition was detected in a certain reach downstream of the dam, and in the sluicing occurred a phenomenon of lower water temperature in spring and summer and higher temperature in autumn and winter than those in the natural condition. And under the dam, monthly mean water temperature was recovering along the stretch to normal in different degrees.
		2016 Vol. 35 (10): 31-39 [Abstract] ( 292 ) PDF (728 KB) ( 495 )

	40	Hydraulic characteristics of nature-like fishways of rock-ramp type
		HE Yumeng, AN Ruidong, LI Jia, YI Wenmin, ZENG Zeng
		DOI: 10.11660/slfdxb.20161005
		Fishways of rock-ramp type are a common form of nature-like fishways. This paper demonstrates two new fishway structures, i.e. aligned slot arrangement and staggered slot arrangement, and presents three-dimensional flow simulations of the two designs to examine their hydraulic characteristics. Scale model tests were conducted to verify the simulations and the numerical model. The results show that in comparison of the flows in the same depth of water, the aligned design is featured with a lower maximum velocity, and the staggered design has a higher growth rate of flow velocity in the adjacent pool downstream. The simulated vertical profiles and test data reveal that the former is more rational in the distributions of turbulent kinetic energy than the latter. Thus, the aligned slot design with better overall hydraulic performance is recommended in this study.
		2016 Vol. 35 (10): 40-47 [Abstract] ( 326 ) PDF (2307 KB) ( 665 )

	48	Impacts of mesh scale and village region roughness on predictions of flood inundation over complex floodplains
		ZHANG Xiaolei, XIA Junqiang, LI Na
		DOI: 10.11660/slfdxb.20161006
		A two-dimensional hydrodynamic model using a TVD finite volume method and unstructured triangular mesh is presented for prediction of the routing of overbank floods over complex floodplain topography. This model has been verified against the previously reported experimental data of dam-break flows in a laboratory flume, and a favourable agreement was achieved between the model predictions and measurements. We applied the verified model to an overbank flood event on a typical floodplain of the Lower Yellow River, and examined in detail the effects of mesh scale and village region roughness on the predictions. The results show that these two factors have influences of different degrees. Smaller mesh scales cannot achieve better results, but reasonable scales should be those that conform to the density of bed elevation points measured. Predictions of flood inundation by using center-hollowed village regions and different village roughness values were significantly different. In the center-hollowed case, an increase of up to 0.57 m in the maximum water depth was calculated, relative to the roughness modelling. An increase in village roughness from 0.06 to 0.12 caused an increase of 0.25 m in the maximum water depth and a reduction of 0.24 m/s in the flow velocity. Thus, in practical engineering applications, conceptualization and modelling of village regions and their roughness values should be determined according to real conditions.
		2016 Vol. 35 (10): 48-57 [Abstract] ( 290 ) PDF (3277 KB) ( 465 )

	58	Longitudinal variations in Cyanobacteria abundance and richness along Tanglang River
		YU Qian, CHEN Yongcan, LIU Zhaowei
		DOI: 10.11660/slfdxb.20161007
		Composition of algae and longitudinal variation in Cyanobacteria abundance and richness are distinct in the river downstream of a eutrophic lake, since the river receives a large amount of lacustrine phytoplankton from the lake. This paper examines the compositions of Cyanobacteria in the Tanglang River located downstream of the Dianchi Lake, and analyzes the driving factors of spatial variations in the abundance and richness of Cyanobacteria using the taxonomical method and statistical methods. The results show that the dominant algae in this river is Microcystis, a component that contributes 79.77% - 97.09 % of the abundance. And the abundance follows a law of exponential decay down the river stream and is featured with a significant inverse correlation with the length of river reach and hydraulic retention time (HRT) and no obvious correlations with water temperature (T), velocity, TP or TN. However, the richness is highly correlated with T (P < 0.01, R = 0.78*) and inversely with velocity (P < 0.05, R = -0.70). Correlation analysis also indicates that the turbulent hydraulic condition is responsible for the longitudinal variation in Cyanobacteria abundance along the river while T and velocity have significant impacts on Cyanobacteria richness.
		2016 Vol. 35 (10): 58-66 [Abstract] ( 283 ) PDF (508 KB) ( 462 )

	67	Load allocation of hydropower stations considering risks of abandoning water and unit commitment
		XU Gang, WU Yunchen
		DOI: 10.11660/slfdxb.20161008
		Economic operation is an essential approach to improve economic benefits of a hydropower station. However, previous studies in China and abroad tended to focus on theoretical optimal solutions that had insufficient consideration of the risks of abandoning water and hence suffered certain deviation from reality. Aiming at this issue, this paper presents an economic operation model that takes constraints of controlling the water level amplitudes in different water level inter-regions and achieves an optimal load allocation by considering risks and unit commitment and coordinating the operations of the upper and lower hydropower stations. Application to the Wuxi cascade hydropower stations shows that this new model can achieve an optimal combination of generator units that effectively reduces the volume of surplus water and controls the risks, and thus it would provide a rather satisfactory guide for optimal unit commitment of the cascade stations.
		2016 Vol. 35 (10): 67-76 [Abstract] ( 183 ) PDF (399 KB) ( 446 )

	77	Application analysis on vibration monitoring system of Three Gorges hydropower plant
		DU Xiaokang, LI Zhixiang, CHEN Gang, HU Jun, HU Dechang
		DOI: 10.11660/slfdxb.20161009
		As technologies of state monitoring and fault diagnosis are developing rapidly, vibration monitoring as a key stability condition monitoring device, is widely used in the hydropower industry. How to extract valuable information from complex signals for decision making of maintenance, needs long-term accumulation of practical experiences. This paper describes the structure and functions of a runout monitoring system adopted for the Three Gorges power plant, together with the arrangement of measuring points and the types of sensors considered, and presents a summary on the cases of vibration diagnosis and analysis, focusing on four aspects of the system: its mechanical, electrical and hydraulic features and its basic structure. Test results and main achievements of the system are briefly discussed for better understanding of such systems and their benefits for improving signal analysis and fault diagnosis.
		2016 Vol. 35 (10): 77-92 [Abstract] ( 237 ) PDF (3958 KB) ( 591 )

	93	Simulations of 3-D fracture networks in rock mass of dam foundation using Latin hypercube sampling
		YUE Pan, ZHONG Denghua, WU Han, ZHANG Yichi
		DOI: 10.11660/slfdxb.20161010
		Rock mass fractures in dam foundation directly affect structure safety and seepage stability of hydropower projects. Accurate 3-D models of rock mass fracture networks provide a solid basis for analysis of dam safety. In construction of such network models, random simulation methods are convenient in obtaining sample data of fracture parameters from the large quantity and complicated distribution of rock mass fractures, and recent research is focusing on the Monte Carlo method for random sampling. However, such an approach ignores the importance of those fractures lying below the exposed surface layer, and suffers from poor numerical stability, low accuracy, and the problem of sample collapsing. This paper presents a new simulation method of 3-D fracture networks in dam foundation using Latin hypercube sampling (LHS). This method derives fracture data from the photographs of both exposed surface layer and boreholes using camera technologies, then applies LHS to stochastic simulation of fracture parameters including their location, size, quantity, and attitude, and finally constructs a 3-D fracture network model in the frame of VisualGeo. It was applied to a hydropower project in China, along with the Monte Carlo method for comparison. The results show its advantages of lower computational cost and more accurate predictions of the field test values for dam foundation stability analysis.
		2016 Vol. 35 (10): 93-102 [Abstract] ( 269 ) PDF (2229 KB) ( 512 )

	103	Effects of cover-weight lift on concrete stress during consolidation grouting
		XU Jiangyu, CHANG Xiaolin, ZHOU Wei, ZHANG Chao, GUO Huawei
		DOI: 10.11660/slfdxb.20161011
		To study cracking in concrete during consolidation grouting, this paper reports three-dimensional finite element simulations of the cover weight lift in the process of consolidation grouting for the cases of applying different grouting pressures or different lifting displacements of the cover weight, along with a case study of the dam section No.11 of the Huangdeng hydropower station. Focusing on concrete surface cracks, we have examined pouring process and stress field in 12 cases of different grouting pressures, lifting displacements and temperature loads, using practical conditions of concrete grouting, temperature control, and data collection practically implemented in the construction of this dam section. The simulation results show that a limited grouting pressure generally causes no significant increase in the tensile stress of concrete, but its tensile safety factor could become quite low if the grouting pressure applied is low enough in the condition of considerable temperature stress. A certain amount of cover weight displacement will cause large tensile stress near concrete surface, and the superposition of temperature loads on the displacement effect often results in higher risks of concrete cracking.
		2016 Vol. 35 (10): 103-111 [Abstract] ( 245 ) PDF (1390 KB) ( 619 )

	112	Flow behaviors of self-compacting concrete in rockfill gaps
		ZHANG Chuanhu, JIN Feng, CHEN Songgui, XU Xiaomin
		DOI: 10.11660/slfdxb.20161012
		Filling effect of self-compacting concrete (SCC) in rockfill gaps is a crucial factor of rock-filled concrete (RFC) strength and engineeing safety. The flow of fresh SCC in rockfill gaps can be regarded as a particle-Bingham fluid two-phase flow that is particularly complicated due to its non-Newtonian rheological characteristics and the complexity of its passage. In this work, SCC flows in the pores of rockfill material was studied by coupling the lattice Boltzmann method and particle discrete element method. We found out that these flows can fall into three regimes: dilute flow, dense flow and jamming. Aperture ratio, or the ratio of pore outlet size to particle diameter, is the most important factor of the flow and its jamming effect. It is much easier for SCC to form dense flow or jamming flow if its volume fraction of particles is higher. For dense flows, a relationship of outlet flow rate versus aperture ratio was established, which could be used to improve fresh concrete pouring technique.
		2016 Vol. 35 (10): 112-120 [Abstract] ( 237 ) PDF (1978 KB) ( 563 )