Journal of Hydroelectric Engineering

水力发电学报

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2017 Vol. 36, No. 2 Published: 2017-02-25

	1	Rational check of design floods for Danjiangkou Reservoir
		GUO Shenglian, YIN Jiabo, LI Dan, LIU Zhangjun
		DOI: 10.11660/slfdxb.20170201
		The dam site flood series of the Danjiangkou reservoir was extended up to 2014 and its greatest historical flood was verified in this study. We checked the design floods using a P3/CF model and P3/LM model separately and obtained a flood limiting water level (FLWL) through reservoir flood routing based on the design flood hydrograph calculated by the P3/CF model. The probable maximum floods were estimated using the envelop curves of the world greatest flood records and the paleofloods in the Hanjiang basin. This rational analysis shows that the historical textual period of the greatest flood occurring in the year 1583 could be extended to a period of 625 years. And by averaging the calculations of these two models, the 1000-year design flood peak and 7-day flood volume should be decreased by 10.4% and 13.3% respectively. Thus we recommend a design flood of 58000 m3/s, a check flood of 80500 m3/s, and an increase in FLWL by 2.0 m for this reservoir. This would significantly increase the comprehensive benefits while ensuring flood control safety of the reservoir.
		2017 Vol. 36 (2): 1-8 [Abstract] ( 120 ) PDF (470 KB) ( 379 )

	9	Frequency analysis of incomplete precipitation data series using Copula functions
		MA Xiaoxiao, SONG Songbai
		DOI: 10.11660/slfdxb.20170202
		In this study we have developed a frequency analysis method of incomplete precipitation data series using Copula functions and examined its statistical properties by conducting Monte Carlo simulation tests. Using this method, we have built bivariate Frank Copula functions for six annual precipitation series observed in Shaanxi province and obtained a solution of the new parameters by applying a multivariable-constrained Rosenbrock optimization algorithm. To verify the method, Copula function-based simulations were conducted and evaluated using the criterion of minimum standard error of fit (SEF). The results show that the frequency of incomplete precipitation series calculated using the Copula functions has good statistical properties with all the statistics of simulation tests lower than critical values of the Anderson-Darling test at a significance level of 5%. The SEF of bivariate joint distribution is less than that of univariate distribution and the former’s estimation of design values is also superior. Frank Copula functions are generally effective and acceptable in analysis of precipitation frequency, and they are able to describe precipitation series better than the univariate methods, particularly for those design stations of incomplete series with difficult data extension.
		2017 Vol. 36 (2): 9-17 [Abstract] ( 207 ) PDF (547 KB) ( 480 )

	18	Effect of artificial island layout on hydrodynamics and water exchange in the coastal waters
		ZHAO Guixia, ZHANG Chen, ZHANG He, JIANG Wei, GAO Xueping
		DOI: 10.11660/slfdxb.20170203
		A three-dimensional hydrodynamic model of the Liaodong Bay was developed in the frame of Environmental Fluid Dynamics Code (EFDC) to study the effects of the artificial island layout on hydrodynamics and water exchange in the coastal waters. The results show that the island blocks water flow and the width of its upstream face is the most significant factor of the blocking effect. An island with a larger width has a greater blocking effect and forms a larger area of low-velocity flow, thereby resulting in a lower capacity of water exchange in the study area. Complexity of island shoreline is also a considerable factor of the flow hydrodynamics: A zigzag shoreline is easier to form a semi-enclosed area of very low flow and poor conditions of water exchange. We compared the blocking effects and flow velocities in the water region near the island in tidal flows of different intensities and found out that the impact of the island much depended on tidal intensity. The capacity of water exchange is described and compared using two parameters: half-life time and volume-exchange rate. The latter is found better describing the differences in water exchange produced by different island layouts.
		2017 Vol. 36 (2): 18-28 [Abstract] ( 260 ) PDF (2623 KB) ( 360 )

	29	Effect of vegetation coverage on relative hydrodynamics of overland flows
		YANG Fan, ZHANG Kuandi, MA Xiaoling, YANG Mingyi, YANG Jie
		DOI: 10.11660/slfdxb.20170204
		To obtain an in-depth understanding of vegetation benefit in basin soil and water conservation, we have conducted laboratory tests on various relative hydrodynamics of overland flows ? relative flow velocity, relative flow depth, relative Froude number, and relative resistance coefficient ? using combinations of six slopes, seven flow discharges, and five types of vegetation coverage. The results show that as vegetation coverage or flow rate increases, both relative flow velocity and relative flow depth are increased and the vegetation effect in reducing flow velocity is enhanced. And the variation trends in both manifest a cut-off coverage of 4.7%. The vegetation effect on relative flow velocity depends much on flow rate but little on land slope, and flow rate are also independent of land slope. An increase in vegetation coverage or flow rate causes a higher relative Froude number and a greater capability of vegetation to weaken overland flow erosion. Relative resistance coefficient grows linearly with an increasing relative flow depth. This study would help the choice of vegetation measures and assessment of vegetation benefits in water conservation and sediment reduction.
		2017 Vol. 36 (2): 29-39 [Abstract] ( 249 ) PDF (730 KB) ( 473 )

	40	Ice regime in river reach upstream of Wanjiazhai Reservoir since its completion in 1998
		JI Honglan, WANG Xiaoyan, TUO Youcai, MOU Xianyou, ZHANG Baosen
		DOI: 10.11660/slfdxb.20170205
		This study aims at the characteristics of ice regime and its influencing factors in the river reach upstream of the Wanjiazhai reservoir to provide a basis for ice control and scheduling. We have examined and compared the ice regime in natural river condition and the new ice regime under operation of the reservoir, using the field measurements during 1987-2015, and analyzed ice regime factors: river morphology, meteorological condition, reservoir operation, and hydraulic factors. The results show that in the reach upstream of the reservoir, the ice regime was featured with a freeze-up process advancing downstream to upstream and a freeze-up type either juxtaposed, packed, or mixed in different section along the river. Ice break-up occurred in the packed freeze-up section and its upstream later than in its upstream; in the upstream section it started at the downstream and was advancing upstream. The whole reach took forms of thermal, mechanical, and semi-violent break-up. Since 1998 when the reservoir started to operate, the ice regime in its upstream river has changed greatly due to changes in riverbed form, air temperature, reservoir control, and hydraulic factors. Major changes were observed in three aspects: ice-run date and freeze-up date were delayed while break-up date was shifted earlier; seldom-freeze-up reaches were turned to stable freeze-up with longer freeze-up river sections; in freezing period, water level was rising and the occurrences of ice jam and ice dam were increased. The comprehensive analysis of ice regime in this study would help ice control decision for the Yellow reach upstream of the Wanjiazhai reservoir.
		2017 Vol. 36 (2): 40-49 [Abstract] ( 142 ) PDF (594 KB) ( 372 )

	50	Evaluation of turbulence models in numerical simulation of flows around a circular cylinder
		WU Yutao, REN Huatang, XIA Jianxin
		DOI: 10.11660/slfdxb.20170206
		Turbulence models have a great impact on numerical simulations of the flows around a cylinder. In this study, six turbulence models have been selected to simulate flows around a single circular cylinder with a Reynolds number of Re = 3900 on a CFD software platform. Simulated hydrodynamic forces (lift and drag coefficients and St, etc.) and flow structures were examined and compared with previous measurements in the literature. The surface pressure distributions calculated using a the k-ε turbulence model and Reynolds stress turbulence model are more accurate and agree well with the measurements. The k-ε model is better in its overall flow simulations while the Reynolds stress model and SST k-ω turbulence model are more accurate in calculations of backflow zones and no-backflow cases respectively. The results would help the selection of turbulence models for simulation of flows around a circular cylinder.
		2017 Vol. 36 (2): 50-58 [Abstract] ( 194 ) PDF (864 KB) ( 402 )

	59	Theoretical study on transport of pathogens during resuspension and settling of bottom sediments
		JIANG Lei, ZHU Deju2, CHEN Yongcan
		DOI: 10.11660/slfdxb.20170207
		Pathogen contamination in surface waters could cause outbreak of epidemics and threaten public health and it is usually indicated by Faecal coliforms (FC), a widely used measure of Faecal indicator bacteria (FIB). Bottom sediments harbor much high number of FC and are generally regarded as an internal pollution source. Their resuspension and settling often causes a change in concentration of suspended sediments (SS) and hence a change in the corresponding characteristics of FC partition to SS. However, the relationship of SS versus FC partition fraction remains yet unclear, and this has hindered a deep understanding of partition mechanisms and lowered the accuracy of microbial water quality models. In this work, experimental study and theoretical analysis were employed. Using experimental measurements we examined the impacts of sediment concentration on FC partition and developed a numerical model for the fate and transport of FC in sediment-laden flows, and then derived theoretical solutions for certain simplified cases. Lastly, we present a comprehensive analysis of the impacts on FC transport in overlying waters by FC partition, FC storage in bottom sediments, and intensity of FC movement near bottom water-sediment interface. The results show that a linear partition model can be used for describing the attachment of FC to suspended sediments. And the variation in FC partition fraction caused by different sediment concentration has a significant influence on the fate and transport of FC during resuspension and settling of bottom sediments. An increase in FC storage in bottom sediments or intensity of FC movement near bottom water-sediment interface will increase FC concentration in overlying water, and the former has a relatively greater influence on FC transport.
		2017 Vol. 36 (2): 59-65 [Abstract] ( 159 ) PDF (1100 KB) ( 322 )

	66	Startup control of hydraulic generator units with given frequencies of hyperbolic tangent type
		LIN Guopeng, ZHENG Yuan
		DOI: 10.11660/slfdxb.201070208
		Compared to open-loop control, closed-loop startup control is more adaptive to different generating units, simpler in operation, and easier to implement. Thus it has been extensively developed in recent years. This paper presents a new type of given frequency, namely hyperbolic tangent type that was worked out through our studies on the behaviors of its mathematical functions to meet the dynamic requirements at the startup stage of hydroelectric generating units. We have developed a mathematical model of hydraulic turbine governor system and used it to simulate the startup stage in the Simulink platform. And the scheme of hyperbolic tangent frequencies was compared with the given frequencies of index type and linear type to verify its superiority. Results show that in the condition of limited relay opening time, it can shorten the startup time and reduce the amplitudes of variations in guide vane opening, water hammer pressure, and other hydraulic parameters. In addition, the given frequencies of hyperbolic tangent type can effectively reduce the chance of overspeed, thus ensuring good dynamic characteristics of the startup control.
		2017 Vol. 36 (2): 66-74 [Abstract] ( 151 ) PDF (1471 KB) ( 265 )

	75	Application of empirical mode decomposition based on complex data to fault diagnosis of hydraulic turbines
		MA Fuqi, JIA Rong, WU Hua, DONG Kaisong, DANG Jian
		DOI: 10.11660/slfdxb.20170209
		A hydraulic turbine unit is a complicated nonlinear dynamic system and its vibration signals are usually non-stationary and nonlinear. Empirical mode decomposition (EMD) is a new method for analysis of time domain signals; it has good adaptability and is more suitable for non-stationary signals, but it has serious problems with end effect, mode-mixing stack, and other adverse effects. The ensemble EMD (EEMD) reduces mode-mixing stack to a certain extent, but it improves little on new mode mixing and suffers from spectrum losing and higher computational cost. In this study, we have developed a complex data-based EMD (CEMD) and applied it to fault diagnosis of a turbine water guide bearing, adding white noise as the imaginary part to construct complex signals. This method adjusts the extremum points of a signal by projecting the white noise in all the directions, and it can reduce mode-mixing stack problem through eliminating the effect of noise projection in calculation of the envelope barycenter. Its application to the signals measured at a hydropower station verifies its validity and reliability.
		2017 Vol. 36 (2): 75-82 [Abstract] ( 184 ) PDF (458 KB) ( 396 )

	83	Industry Foundation Classes-based hydroelectric engineering information model
		ZHANG Zhiwei, HE Tianfeng, FENG Yi, ZHANG Jianping
		DOI: 10.11660/slfdxb.20170210
		Hydroelectric engineering information models provide a basis for data support to information management of hydroelectric projects. This paper discusses the Industry Foundation Classes (IFC) data model, a widely used data standard for building information models (BIM), and presents an IFC-based hydroelectric engineering information model. In this IFC-based model, definitions of the new entities characterizing hydroelectric projects were added to its layers of domain schema, shared schema, core schema and resource schema, and we tested it and examined its applicability to a real hydroelectric project. The results indicate that in comparison to the IFC standard, the new model enables a satisfactory description of the new entities and their relationships and improves accuracy and standardization in representation of project attributes. Thus it is a better data support to storage and exchange of the information for the full life-cycle of hydroelectric projects.
		2017 Vol. 36 (2): 83-91 [Abstract] ( 180 ) PDF (600 KB) ( 354 )

	92	Determining bearing capacity and deformation modulus of slope foundation soils using analogy method
		JIE Yuxin, LIU Zhankui
		DOI: 10.11660/slfdxb.20170211
		Foundation treatment is a necessary measure in construction of high slopes on soft foundation, but at present it has few commonly acceptable guidelines on how to determine the properties of foundation soils. This paper describes a method for determining bearing capacity and deformation modulus of foundation soils using the method of analogy. Results show that such foundation is easy to meet the requirement on bearing capacity. We can demonstrate the critical slip surface will cut into the slope foundation if its soil strength is below the strength index of the slope fill. To have the same bearing capacity, foundation soils are allowed to take different combinations of strength indexes; with a fixed bearing capacity, a bigger friction angle of the soil will acquire a greater safety factor and accordingly a smaller depth of the slip surface cutting into the foundation soil. A homogeneous foundation has a value range of d/L less than 1/3 in various circumstances.
		2017 Vol. 36 (2): 92-101 [Abstract] ( 150 ) PDF (682 KB) ( 469 )

	102	Comparison of seismic responses of concrete faced rockfill dam under excitation from design response spectra in new and old codes
		ZHANG Yu, KONG Xianjing, ZOU Degao
		DOI: 10.11660/slfdxb.20170212
		In 2015 the old code Specification for seismic design of hydraulic structures was revised into a new code, Code for seismic design of hydraulic structures of hydropower projects. In this study, we have investigated dynamic responses and anti-seismic stability of a typical concrete faced rockfill dam (CFRD) of 250 m high under two types of seismic excitation formulated according to the new and old codes separately, to examine the differences caused by the two excitations. Our FEM results indicate that relative to the old code, the dynamic responses to the seismic waves designed by the new code are increased considerably and the local stability of dam slope is lowered accordingly. Thus we suggest more attention to these differences and a safety re-check on the built dams when it is possible.
		2017 Vol. 36 (2): 102-111 [Abstract] ( 165 ) PDF (914 KB) ( 442 )

	112	Intelligent management of large-scale construction projects
		FAN Qixiang, QIANG Maoshan, JIN Heping, LI Guo, HE Wen
		DOI: 10.11660/slfdxb.20170213
		Current hydropower development in the lower Jinsha River encounters great technical and management challenges, including complicated and harsh natural conditions, rapid changes in social environments, diversified interests, and trans-regional multi sub-projects. This requires further improvement on the existing capability of large-scale project construction for forecast, analysis and control of the projects to minimize their uncertainties brought about by human factors, changing environments and construction conditions, so that the target of six managements of construction projects can be better achieved. To this end, a concept of intelligent dam was formulated and introduced into the construction management of Xiluodu ultra-high arch dam, and intelligent construction technologies were developed and applied to typical dam construction procedures. Based on these applications, this paper describes a theory of intelligent management of large-scale construction projects that was formulated by combining current project management trends with extensive applications of information technology. We also present a technical framework of this new type of management that applies a closed-loop intelligent control principle developed in this study and featured with comprehensive sense, accurate analysis, and real-time control. This framework have five key components: starting from a 3D GIS/DIM structure and multi-source data, targeting at the capability of creating life-long asset value, dynamic simulation and real-time control of actual working states as its core technology, a TGPMS/iDam system as a platform for comprehensive task integration, and N-dimensional enhanced collaborative management as its guideline. The new management framework and theory presented in this paper would be helpful in shaping and upgrading traditional construction project management to a new level characterized by informatization, digitalization, and intellectualization to achieve better project construction in quality, safety and efficiency.
		2017 Vol. 36 (2): 112-120 [Abstract] ( 300 ) PDF (1156 KB) ( 748 )