Journal of Hydroelectric Engineering

水力发电学报

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2018 Vol. 37, No. 1 Published: 2018-01-25

	1	Research on design of dam-break risks control for cascade reservoirs
		ZHOU Jianping, ZHOU Xingbo, DU Xiaohu, WANG Fuqiang
		DOI: 10.11660/slfdxb.20180101
		The dam risk criteria, design methodology of risk control, and design safety index system of cascade reservoirs are essential to the safety management of a river basin. In this paper we systematically examine previous studies in China and overseas, and suggests an acceptable social risk criterion of 10-6/a and a tolerable social risk criterion of 10-5/a for cascade reservoirs. We also present a trinity design methodology of “safety factor - reliability index - annual failure probability” based on the current methods of project design, the theories of safety margin ratio, and the Bayesian network. According to its grading standard and risk control functions in the river basin, a hydropower project can be defined as a “special class project”, if it satisfies: dam height greater than 200 m and water storage capacity larger than 1 billion m3, or its dam break will cause the First Class dam break in the downstream. For this special class, we suggest a risk control standard: annual failure probability of (1.0-5.0) ×10-8 and reliability index of 4.45-4.70, and construct a system of risk design indexes including the design standards for flood control, seismic resistance, dam reserved free board, and flood discharging capacity. The results of this study would fill the gap in the standards for safety design of super-high dams over 200m high and help the research on risk control theories and design of cascade reservoirs.
		2018 Vol. 37 (1): 1-10 [Abstract] ( 272 ) PDF (620 KB) ( 756 )

	11	Comparison of mechanical characteristics of submerged plane steel gates with different layouts
		ZHAO Chunlong, WANG Zhengzhong, WANG Mingjiang, LI Gang, ZHAO Dahai, LIU Jiliang
		DOI: 10.11660/slfdxb.20180102
		Submerged plane steel gates in water resources and hydropower projects take the form of forward or reverse water retaining. To accurately analyze the difference of these two forms in the mechanical characteristics of the gate under high water head, a sub-modeling method is used to simulate the critical parts incorporating nonlinear contact interaction, and a comparison of the stress response using different section forms of main girder is provided. Results show that in the forward form, the gate panel is in contact with the grillage and the bearing capacity is not limited by the strength of the weld, while in the reverse case, water pressure makes the gate panel depart from the flange, especially for the case with a box girder and wide flange. This causes the deformation in the panel to double that of the forward form and a stress concentration to occur on the cross section of connection weld. In sum, an I-shaped or Π-shaped section of the main girder is better than the box section and this should be specified in the specification.
		2018 Vol. 37 (1): 11-20 [Abstract] ( 157 ) PDF (3322 KB) ( 359 )

	21	Improved social emotional optimization algorithm for optimal operation of cascade hydropower stations
		LIU Qiang, ZHONG Ping’an, CHEN Yuting, XU Bin1, ZHU Feilin
		DOI: 10.11660/slfdxb.20180103
		Exploring new solving methods has always been one of the hotspots for the study on optimal reservoir operation. The social emotional optimization algorithm (SEOA) is a new heuristic intelligent optimization algorithm, but it has not been applied to reservoir operation yet. In application of SEOA to the operation of cascade hydropower stations, this study formulates an initial population uniform design to overcome the low representativeness of initial population caused by stochastic generation, and develops a population elimination strategy aiming at the low activity of population and the tendency of local convergence caused by some individuals’ premature convergence. Thus an improved social emotional optimization algorithm (improved SEOA) is achieved. A case study shows that this algorithm is efficient and stable, and it has a great search capability in solving the optimal operation models of cascade hydropower stations.
		2018 Vol. 37 (1): 21-30 [Abstract] ( 182 ) PDF (493 KB) ( 344 )

	31	Joint effect of pollution source interception and ecological water replenishment in Qinhuai River Basin
		SONG Weiwei, PANG Yong
		DOI: 10.11660/slfdxb.20180104
		As China's urbanization accelerates, the population of large cities is growing rapidly. Urban waste water discharge is also increasing, resulting in surface water quality falling below the standards. This paper presents a prediction of surface water quality that is improved using combined measures ? a near-future measure of intercepting a small portion of the sewage for treatment and replenishing a certain amount of ecological water and a long-term measure of intercepting most of the sewage for treatment ? based on the requirements by the surface water quality standards. We examine different schemes in a case study of the Qinhuai River basin using the field survey data of water quality and a water quality mathematical model. The results show that in the near future (2017-2020), the surface water quality standards can be met through certain construction in this drainage area, intercepting 35% of the sewage for treatment, and replenishing ecological water of 30 m3/s to the new Qinhuai River branch. And in the long term (2020-2025), apart from continuing the construction, the sewage treatment should reach Class IV and 80% of the sewage should be treated. Our joint method of sewage interception and ecological replenishment to braided river channels provides a new measure for improving surface water quality in the river basins where large cities are located.
		2018 Vol. 37 (1): 31-39 [Abstract] ( 149 ) PDF (803 KB) ( 528 )

	40	Influence of vertical coordinate systems on temperature-stratified flow simulation
		HU Yu, ZHANG Wenjun, XIA Jianxin, REN Huatang
		DOI: 10.11660/slfdxb.20180105
		With the construction of high dam reservoirs and the appearance of high performance computers, increasingly more 3D models are used in the simulations of stratified flows in reservoirs. Influence of the vertical coordinate system on the accuracy in the simulations of small scale regions is essential to 3D modeling, but there are few previous studies on it. Based on the results of a stratified flow experiment, this study focuses on evaluation of the effects of the most commonly used Cartesian z coordinate system and the σ coordinate system on the accuracy in flow and temperature simulations. It is concluded that both systems are applicable but with different accuracy and the σ coordinate is better. Static instability and extra vortices caused by bottom step in the z coordinate exaggerate vertical diffusivity and lead to weaker velocity and vertical temperature stratification than those in the σ coordinate. Distribution of horizontal velocity shows small scale circulations near the bottom that are caused by a spurious water falling process produced numerically in the z coordinate modeling. The isothermals also show a stair-stepping trend in the z coordinate system.
		2018 Vol. 37 (1): 40-48 [Abstract] ( 111 ) PDF (765 KB) ( 362 )

	49	Statistics and classification of river patterns based on river resistance law
		SONG Xiaolong, BAI Yuchuan
		DOI: 10.11660/slfdxb.20180106
		We apply the friction loss equation to natural rivers in this paper. Using effective methods such as data analysis and data fitting, an analytical form of river resistance is obtained based on hydraulic geometries including slope, discharge, flow velocity, grain size, river shape parameter and so on. Through inversion of this river resistance law, the river shape parameter can be used as a discrimination criterion and two simple river pattern discrimination threshold curves with clear physical meanings can be constructed. The two curves divide the river systems into three main patterns: single-thread, stable multi-thread, and unstable multi-thread channels. Analysis reveals that in this method, a single-thread channel is sensitive to bank strength, but it is not true for a braided channel river, particularly those with an overlarge width-depth ratio. The pattern of a river can vary in a short period following an external disturbance as often does a meandering river with transient braided channels, but it could eventually return to the dynamic equilibrium state.
		2018 Vol. 37 (1): 49-61 [Abstract] ( 161 ) PDF (3593 KB) ( 292 )

	62	Hydraulic characteristics and optimization of Y-type pipes with large diameter difference
		GU Xinxin, WAN Wuyi, ZHANG Boran
		DOI: 10.11660/slfdxb.20180107
		Flow in a Y-type pipe with large diameter difference is complicated and often generates back flows and negative pressure around its branching section, thus becoming a threat to its safety and normal operation. This paper presents a three-dimensional CFD model and simulations of the velocity and pressure distributions in such pipes to improve the fluid patterns in the branching section. Corresponding model pipes are experimentally tested to verify the simulations, and the branching connection is optimized through comparison of its taper and prismatic transition designs. Results show that a taper transition at the branch inlet can efficiently reduce negative pressure zone and reduce back flows around the branching. It plays an important role in prevention of cavitation damage to the pipe and in improvement of the flows.
		2018 Vol. 37 (1): 62-69 [Abstract] ( 147 ) PDF (3763 KB) ( 318 )

	70	Influence of typhoon moving directions on storm surges at Dongtou fishing port
		SUN Zhilin, JI Hanqing, FANG Shibiao, YAO Zhongzhi, HAO Haoyu, ZHANG Dejun
		DOI: 10.11660/slfdxb.20180108
		This paper presents an analysis of four historical typhoons moving in different directions to demonstrate the effects of typhoon moving direction on the storm surge at the Dongtou fishing port. We use Delft3D to simulate the storm surges around Dongtou Island and compare the calculated tidal levels with the field data observed at six nearby gauge stations, showing an average error less than 15 cm in the calculations of astronomical tides. The results show that a typhoon that passes by east generates a storm surge characterized by a primary peak (in the middle) and two secondary peaks (on both sides), while a southern typhoon often causes a storm surge of single peak type that is thus the strongest. For a western typhoon, the storm surge manifests a fluctuating increase that is featured with a trend close to that of an astronomical tide and a peak occurring at the time about the typhoon arrives the nearest location. A northern typhoon develops a similar fluctuating trend in the storm surge. However, it has little influence on the fishing port, though it could have multiple peaks in water rising at each astronomical climax and generate water falling at astronomical low tide.
		2018 Vol. 37 (1): 70-78 [Abstract] ( 158 ) PDF (741 KB) ( 224 )

	79	Optimization tests of suspension beam array auxiliary energy dissipaters in low-head dam stilling basin
		LIANG Hongru, TAN Yanping, LIU Xing, WANG Shan, TAN Haiyan, JING Feng
		DOI: 10.11660/slfdxb.20180109
		A supplementary energy dissipater of suspension beam arrays in a low head stilling basin is examined in this study using an experiment of 40 orthogonal tests and a bundling method, focusing on its hydrodynamic characteristics under different beam arrangements including a new arrangement featured with a variable beam spacing and inclined beam installation between the upper and lower arrays. The results show that variation in beam spacing reduces water head or increases energy dissipation rate effectively, thereby leading to an increase of 12.15% in the in-basin water head variation relative to that of fixed spacing. And the inclined beam schemes generally help reduce water head in the cases of fixed and variable spacing, but forward inclination is better allowing the in-basin water head variation of possibly 48.76% and 10.71% larger in the two cases respectively. From the experiment, we obtained the optimal designs ? forward inclined beams of spacing 8, 8, 8, 12, 12 and 4 cm in six bundled tests respectively.
		2018 Vol. 37 (1): 79-86 [Abstract] ( 112 ) PDF (822 KB) ( 261 )

	87	Wavelet packet energy features of acoustic emission signals from hydraulic turbines under cavitation
		LIU Zhong, ZOU Shuyun, CHEN Ying, SONG Jiacheng, LI Zhipeng
		DOI: 10.11660/slfdxb.20180110
		To fully study the time and frequency characteristics of acoustic emission (AE) from hydraulic turbines in cavitation conditions, this paper conducts a series of cavitation tests on a model Francis turbine, collects AE signals and extracts their features in the form of wavelet packet energies in frequency bands, and analyzes their variation relations in different cavitation stages. The results show that with cavitation coefficient decreasing gradually, the operation condition of the turbine changes from no cavitation to incipient cavitation, then to fully developed cavitation stage. Accordingly, significant variations occur in each of the wavelet packet energies in the feature frequency bands of AE signals collected from the locations of the guide vane lever and the runner lower band. In this process, the energy increases quite slowly at initial stage, reaches a peak around incipient cavitation and decreases slightly, then increases violently at critical cavitation until a peak value much greater than the first one, and finally drops sharply.
		2018 Vol. 37 (1): 87-93 [Abstract] ( 131 ) PDF (398 KB) ( 319 )

	94	An analysis on stability domains of tubular turbine units
		NAN Haipeng, GUAN Xin, MEN Chuangshe
		DOI: 10.11660/slfdxb.20180111
		As more low-head hydro resource is developed, the proportion of tubular turbine units in China is gradually increasing. But for all these units, their inertia time constants and inertia ratios usually fall far beyond the required scope of control systems by the current national standard of hydro turbines due to the limits of their application conditions and structures, particularly their overlarge constants of water inertia time and too small constants of unit inertia time. This paper compares the application conditions of the hydro turbine control systems specified in the domestic and overseas standards, analyzes our survey data on the parameters and operation conditions of the existing typical power plants in China, and examines the stable domain and regulation quality using a mathematical model of hydro turbine control systems. The results show that all these existing low-head tubular turbine units still have large stability domains and can operate under safe and reliable conditions. We can demonstrate that better regulation quality can be obtained as long as the control parameters are adjusted properly, and that the required tuning of turbine unit parameters stays within the normal ranges recommended by IEC. Thus we suggest that the requirement of the unit inertia ratio in the standard be revised to be no more than 1.5 and the requirement of the unit inertia time constant no less than 1.5 sec.
		2018 Vol. 37 (1): 94-100 [Abstract] ( 130 ) PDF (517 KB) ( 409 )

	101	P-y curve methods of steel pipe pile foundations under combined loads
		YU Shizhang, LI Sa
		DOI: 10.11660/slfdxb.20180112
		The p-y curve method is often used to analyze the horizontal bearing capacity of steel pipe pile foundations. But in offshore engineering, it is inconclusive because most existing methods for determining p-y curves, based on a number of cases of laterally loaded piles, are highly empirical and the pile foundations are often subjected to complex multi-directional loading conditions. The present study develops a series of p-y curves for a single pile under H-V and H-M composite loading through three-dimensional FEM simulations and compares the results with the p-y curves in previous studies.
		2018 Vol. 37 (1): 101-109 [Abstract] ( 134 ) PDF (1112 KB) ( 542 )

	110	Compaction characteristics of embankment sandy soils under negative temperature conditions in cold regions
		SU Anshuang, LI Zhaoyu, YU Shu, ZHANG Shoujie, YAN Jun
		DOI: 10.11660/slfdxb.20180113
		This paper examines the influence of soil temperature, environment temperature, moisture content, and compaction energy on the compaction characteristics of sandy soil under winter conditions through laboratory tests at the environment temperatures of -10, -15 and -20 ?C. Field compaction tests on the same soils were also performed during winter construction of an embankment. Results indicate that for unfrozen sandy soil under negative temperature, there has a maximum dry density and optimum moisture content, and that the dry density exhibits a slight decline trend with the decrease in environment temperature. For a given rolling machine, good correlation exists between the times of its rolling compaction and the beat times of compaction. For frozen sandy soil, however, its dry density shows an obvious decrease with the increasing moisture content or decreasing soil and environment temperatures. Additionally, with the increase of moisture content, much more compaction energy is needed to reach the required dry density. For a given rolling machine, we can calculate the times of its rolling compaction needed to ensure compaction quality in winter construction by obtaining the compaction energy beforehand through compaction tests at different negative temperatures.
		2018 Vol. 37 (1): 110-120 [Abstract] ( 103 ) PDF (541 KB) ( 228 )