Journal of Hydroelectric Engineering

水力发电学报

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2019 Vol. 38, No. 11 Published: 2019-11-25

	1	New system for rapid measurement of indoor surface velocity fields based on feature matching velocimetry
		CAO Liekai, Detert Martin, LI Danxun
		DOI: 10.11660/slfdxb.20191101
		To enhance spatial resolution and measurement efficiency, we present a novel system for measuring surface velocity fields of flows on large-scale hydraulic laboratory scale models. The basic idea is to match characteristic image features. To this end, flow is seeded with tracer and a camera is recording the scenery in plumb vertical top view in a height of 5 m. A matching algorithm correlates characteristic image feature points, and instantaneous and time-averaged velocity fields are provided automatically. Applications of the system to both weir flow and jet flow experiments yield reasonable velocity fields with high spatial resolution. This velocimetry system shows to be effective, efficient, and flexible. The output velocity field has high temporal-spatial resolution and keeps considerable accuracy with PIV, which can truly reflect characteristics of indoor surface flow.
		2019 Vol. 38 (11): 1-8 [Abstract] ( 243 ) PDF (9917 KB) ( 140 )

	9	Study on harnessing schemes of flood discharge atomization
		LIAN Jijian, HE Junling, GOU Wenjuan, RAN Danjie, WANG Chang
		DOI: 10.11660/slfdxb.20191102
		Heavy rainfall and fog disasters caused by flood discharge have a great impact on the safety of surrounding buildings and ecological environment. The buildings located within such rainfall areas (of rainfall intensity S ≥ 10 mm/h) should be avoided as much as possible. Aiming at the situation of the powerhouse at the Nazixia hydropower station located in the rainfall area of its flood discharge, this study conducts hydraulic scale-model tests to optimize the bucket types of spillway. Various parameters of different bucket types are compared: trajectory height, trajectory distance, impinging edge width of the jet nappe, downstream riverbed erosion pattern, nappe wind, weight of splashed water. Through optimization, we suggest a flip bucket of curved surface attached to the spillway left wall, and compare it with the original design in terms of various atomization characteristics under different discharges. For this bucket, its trajectory nappe is deflected rightward away from the spillway axis and far away from the powerhouse, thereby significantly reducing its weight of splashed water and nappe wind speed near the powerhouse under different working conditions. Thus the suggested bucket is obviously superior to the original design.
		2019 Vol. 38 (11): 9-19 [Abstract] ( 176 ) PDF (3613 KB) ( 733 )

	20	Formula of bedload sediment transport based on nonlinear theory
		XU Xiaoyang, ZHANG Genguang, ZHOU Shuang, WANG Yule, CHEN Xuebiao, LIU Yu
		DOI: 10.11660/slfdxb.20191103
		Based on the cusp-catastrophe model of nonlinear theory, this paper examines the influence of water flow conditions and the relative position of sediment particles on riverbed on the nonlinear dynamic characteristics of sediment transport, formulates the state variables and control variables of this model, and constructs a new cusp-catastrophe model for qualitative description of bedload transport. Through coordinate transformation and topological transformation, a nonlinear bedload transport rate formula is derived. This formula is verified against previous measurements and compared with other formulas of the same theory and the classical formulas. We explain the difference in calculations of low-intensity sediment transport using different formulas, and present an analysis on the cause of sudden changes in the calculation accuracy of high-intensity sediment transport. And the influence of incipient shear stress of bedload motions on the formula of sediment transport rate is discussed. It is verified that our nonlinear formula is reasonable with good applicability.
		2019 Vol. 38 (11): 20-28 [Abstract] ( 142 ) PDF (488 KB) ( 639 )

	29	Investigation into resistance characteristics of building distributions in overbank floods
		GUO Peng, XIA Junqiang, ZHANG Xiaolei
		DOI: 10.11660/slfdxb.20191104
		Dike-break flooding is a main natural disaster that could cause losses in life and property on river floodplain, and studying its routing characteristics is crucial to protection of such areas. However, complex types of the underlying surface of a river floodplain produce different flow resistances. In this study, a generalized physical model and numerical simulations are used to examine the influence of buildings distributions on flood routing over the Lankao-Dongming floodplain area of the lower Yellow, focusing on the flows over an area of buildings arranged in four different patterns under four main channel discharges and four incoming flow angles. The experimental results show that flow depth over this area is increased with the increase in the inflow discharge of the main channel and its flow resistance varies with different building arrangements. Then, we use a two dimensional hydrodynamic model to calculate the flood inundating process, and obtain calculated flow depths in good agreement with the measurements. For the building area, different Manning coefficients are calculated for the simulations to improve its resistance modeling by comparing to the corresponding measured depths. Results show that at Manning coefficients of 0.05, 0.08, 0.12 and 0.16, the calculated depths are in good agreement with the measured values under building patterns of 3×3, 4×4 and 5×5 arrays and a staggered array respectively; and that the location of the simulated hydraulic jump are nearly the same as experimentally measured. This study helps the planning of building arrangement on river floodplain to reduce dike-break flooding, and it is also useful for verifying the accuracy of hydrodynamic models.
		2019 Vol. 38 (11): 29-39 [Abstract] ( 120 ) PDF (5042 KB) ( 370 )

	40	Benefit compensation mechanism of leading hydropower station based on combination of electricity price and output
		HE Yong, WANG Jing, LIU Xingju, LI Gang, XIANG Huawei
		DOI: 10.11660/slfdxb.20191105
		This paper constructs a benefit compensation model for maximizing the total power output of cascade hydropower stations using an improved progress optimality algorithm (POA) coupled with discrete differential dynamic programming (DDDP) and considering loss in diversion flow. The algorithm uses water stage combination of the cascade reservoirs as a basic calculation unit in solving for compensation benefit on the basis of quantifying the impact of water diversion on the power output. We calculate the electricity price of the leading hydropower station under different power returns of the benefited stations using the feed-in tariff of operation period, and develop a power generation benefit compensation method of combining electricity price and output. The mechanism of corresponding benefit compensation for the leading station is demonstrated. Application to the cascade stations in the Wu River basin shows that our method is effective in quantitative analysis of the diversion flow and its impact on the power output of the cascade stations and in calculations of the compensation benefit of the leading station. The method can also be used to resolve conflicts over the benefits of upper and lower stages of the cascade.
		2019 Vol. 38 (11): 40-48 [Abstract] ( 122 ) PDF (359 KB) ( 466 )

	49	Influence of distributed rainfall input and routing simulation on flood peak flow calculation
		HUANG Pengnian, LI Zhijia
		DOI: 10.11660/slfdxb.20191106
		Flood forecasting for small and medium-sized catchments with an area smaller than 3000 km2 is a weak spot in the national flood forecasting system. For such catchments, it is imperative to improve accuracy and reduce uncertainty in flood peak forecasting. This paper examines the effects of distributed rainfall input and distributed routing simulation on accuracy and uncertainty in peak flow estimation through a case study of the Dongwan catchment of the upper Yiluo River. Based on the Xinanjiang model and Monte Carlo sampling method, we adopt four methods: lumped simulation, lumped rainfall-distributed routing simulation, distributed rainfall-lumped routing simulation, and distributed rainfall-distributed routing simulation. The results show that a distributed rainfall input improves overall accuracy in peak flow estimation, but it increases estimation errors greatly for rainfall events with extremely uneven spatial distribution is inputted. A distributed rainfall input contains parameters independent of each other and will raise uncertainty in flood peak flow calculations. Distributed routing simulations reduce overall uncertainty in flood peak calculation. The results are useful to flood forecasting for small and medium-sized catchments.
		2019 Vol. 38 (11): 49-57 [Abstract] ( 121 ) PDF (1131 KB) ( 599 )

	58	Investigation of annual runoff frequency calculation based on polynomial normal transformation
		CHEN Defang, SONG Songbai
		DOI: 10.11660/slfdxb.20191107
		The accuracy of hydrological design values directly affects the engineering scale to be determined. A polynomial normal transformation (PNT) method is used in this study to estimate the design values (in quantile) of annual runoff at given frequencies to improve the accuracy of hydrological frequency calculations. We use a Monte Carlo method in numerical simulations and compare four calculation methods of third-order polynomial coefficients: product-moment (PM) method, L-moments (LM), least-square (LS) method, and Fisher-Cornish (FC) asymptotic expansion method . And a third-order polynomial normal transformation method is used to calculate the frequencies of the natural annual runoff at five stations in the Yellow River Basin. The results show that the polynomial coefficients obtained using the four methods give good estimates of the annual runoff design values at given frequencies, and the design value sequences fit well with the measured sequences. In the accuracy of normality conversion and data fitting, a list from high to low is LS method, LM method, FC method and PM method.
		2019 Vol. 38 (11): 58-69 [Abstract] ( 157 ) PDF (878 KB) ( 454 )

	70	Spatiotemporal distributions of vegetation index and climatic productivity in Ningxia in recent years
		HUANG Yueyue, YANG Dong, FENG Lei
		DOI: 10.11660/slfdxb.20191108
		This paper examines the spatiotemporal variation characteristics and relationship of normalized difference vegetation index (NDVI) of Ningxia versus its climate productivity based on remote sensing images of 2000-2017, using methods of univariate linear regression analysis, a Thornthwaite memorial model, correlation analysis, etc. The results show that the NDVI of the southern Ningxia forest area and the irrigation districts with irrigation water diverted from the Yellow River is higher than that of the central arid zone, and in recent years it is increasing significantly at a rate of 0.041 (10 a)-1. During the 18 years, vegetation index in Ningxia increased slightly, accounting for 64.12%. The climatic productivity is decreasing gradually across Ningxia from southeast to northwest, and the time trend in annual precipitation is similar to that in climatic productivity. In most areas, NDVI is positively correlated with climatic productivity in pixel scale, with negative correlation covering only 4.92% of the total area. Linear fitting degree of these two parameters is 0.731.
		2019 Vol. 38 (11): 70-81 [Abstract] ( 183 ) PDF (1929 KB) ( 411 )

	82	Investigation of flow characteristics in a bidirectional tubular turbine during switch working modes
		FENG Jianjun, LI Wenfeng, ZHU Guojun, WU Guangkuan, LUO Xingqi
		DOI: 10.11660/slfdxb.20191109
		A tidal hydroelectric unit switches working modes frequently creating a transition condition that is easy to become the cause of operational faults. To explore the transient flow characteristics of a bidirectional tubular turbine, numerical simulations of the flows were conducted using a lattice Boltzmann method (LBM) focusing on the transients created by two types of switching: turbine mode switched to discharge mode, and discharge mode switched to pump mode. The simulations used self-defined functions to control the movement of guide vanes and blades, as well as variations in the working parameters of the turbine. Further, the internal flow characteristics were also obtained for the two transient conditions. During the flow transition from turbine to discharge mode, the flow rate was found to increases gradually with time and the calculated unit flow rate was found to be 2.88 times the initial flow on completion of the transition agreeing well with the measured values. It shows the accuracy and reliablility of the applied methodology in this research. During flow transition, apparent low pressure occurred in certain areas on the suction surface of runner blades due to flow pattern changes, which may cause cavitation erosion of the blades. The radial force on the runner was fluctuating periodically, being a potential excitation to vibrations in the shafting. Several turbulent vortices in the draft tube were observed and a spiral cavity vortex was formed due to the decrease in internal pressure.
		2019 Vol. 38 (11): 82-89 [Abstract] ( 103 ) PDF (2454 KB) ( 494 )

	90	Correlation between radial forces and flow patterns in rotodynamic multiphase pump
		XIAO Wenyang, TAN Lei
		DOI: 10.11660/slfdxb.20191110
		Oil-gas mixture transport is a crucial technology in the crude petroleum and natural gas industry. A rotodynamic multiphase pump has the advantages of compact structure, wide operation range, and good abrasion resistance. In a single-stage rotodynamic multiphase pump, the relationship of the radial forces on the impeller and guide vaneswith its gas-phase flow patterns were investigated numerical simulations under inflow gas volume fractions (IGVFs) of 0%, 5%, 10% and 15%. The centers of the radial forces were found to be located at the coordinate origin under the single liquid phase inlet condition, and their eccentricity increased with the increasing IGVF values. Dominant frequencies of these forces were related to impeller rotational frequency and blade number, and the amplitudes were found to increase with the increasing IGVF values. Distribution of fluid fraction over each impeller passage was non-uniform, and most of the gas was accumulated around the hub. Strip-shaped gas zones generated at the trailing edges of the impeller blades entered guide vane channels and developed into gas pockets, and the developing time was related to the dominant frequencies of radial forces. Phase differences in gas volume flow rates occured among different impeller passages, resulting in unequal gas volumes over these passages. This led to uneven forces on each blade and a radial force on the impeller. With the value of IGVF increasing, the developing period of the gas pockets became shorter and the dominant frequencies increased.
		2019 Vol. 38 (11): 90-101 [Abstract] ( 170 ) PDF (5270 KB) ( 503 )

	102	Approximate analytical solution of grouted bolt stress in homogeneous rock mass
		BAO Qichang, PENG Shouzhuo, ZHONG Jianwen, LIN Lv
		DOI: 10.11660/slfdxb.20191111
		Grout bolting is widely used as an economical reinforcement of surrounding rocks in underground engineering. However, the mechanism of bolt and rock interaction is not yet fully understood, and analytical evaluation of the reinforcement effect is still underway. This paper derives analytical expressions for the stress, displacement and yield depth at the medium interface for elastic bolts fully embedded into a plastic zone of homogeneous surrounding rock, using the elastic-brittle-plastic model and Mohr-Coulomb yield criterion. This analytical model takes into account the inhibition effects of bolt shear stress ?b on rock. The simulation results of the Kielder test tunnel are in good agreement with measurements. Comparison analyses using different bolt lengths for this tunnel indicate that an anchor length of 1.8 m is appropriate and the benefit of longer bolts is insignificant. Our analytical model is applicable to non-axisymmetric underground caverns and its solutions are simple and clear, helping identify parameters and evaluate support load and support effect in preliminary design phase.
		2019 Vol. 38 (11): 102-111 [Abstract] ( 104 ) PDF (517 KB) ( 516 )

	112	Development and application of multi-parameter adjustable laboratory device for simulating roller-compacted concrete compaction
		LIU Donghai, SUN Longfei, XIA Xietian
		DOI: 10.11660/slfdxb.20191112
		To find optimal combination of compaction parameters through compaction tests is the key to ensure compaction quality of a roller-compacted concrete (RCC) dam. The conventional tests conducted before dam construction are costly and time consuming. This paper describes a similarity principle for RCC compaction simulations based on compaction capability, and presents a multi-parameter adjustable laboratory device for the simulations. The device can not only overcome the scale effect of small test rollers, and the shortcoming in the plate vibration used in vibration compaction forming tests that is greatly different from on-site roller vibration compaction, but make the parameters adjustable in multiple stages, such as roller static load, excitation force (vibration frequency and amplitude), roller velocity, and compaction passes. Simulation experiments show that the device can equivalently simulate the working conditions of a roller compactor on site; compacted samples reach the same density and strength as those of standard specimens, and the interface shear strength of the samples meet the requirements of on-site construction. It provides an economical, convenient, accurate, and effective technology to study the influence of compaction parameters on the compaction quality of RCC dam materials and then to optimize the parameters.
		2019 Vol. 38 (11): 112-120 [Abstract] ( 177 ) PDF (2512 KB) ( 404 )