水力发电学报
          Home  |  About Journal  |  Editorial Board  |  Instruction  |  Download  |  Contact Us  |  Ethics policy  |  News  |  中文
  Office Online
  Included Databases

The journal is included in the following databases:
(i)Scopus,
(ii)The Chinese Science Citation Database Source Journals,
(iii)The Chinese Science Journal Abstract Database,
(iv)The Chinese Science and Technology Papers Statistics and Analysis Database,
(v)China Newspaper Subscription Guide Information Database,
(vi)Chinese Academic Journals (CD).

 
 
2019 Vol. 38, No. 4
Published: 2019-04-25

 
     
1 Review on application of UAV-based photogrammetry in urban flood modeling
CHENG Tao, XU Zongxue, HONG Siyang, WANG Zhonghua
DOI: 10.11660/slfdxb.20190401
In view of the severe situation of urban flooding in China and the development of previous flood simulation models, this paper points out that refining urban flood simulations is a focus in the future studies. Data acquisition methods based on the low-altitude UAV-based photogrammetry can provide high-resolution ground information such as flooded areas in a city, helping build complete databases. By summarizing typical technical indicators and application of this new technology, we demonstrate that it has the advantage of low cost in acquisition of easily updated large-scale data and hence is widely applied in numerous fields. And it also makes it easier to develop or refine flood simulation models through collecting data of landuse, topography, and flooded area, among others. In addition, technologies like three-dimensional modeling and monomer modeling can serve the purpose of better digitalization and refinement of flooding process simulations and result display. Although problems still remain in the application of photogrammetry technology to flooding simulation, it should have a good application prospect as it is improved and further developed in future.
2019 Vol. 38 (4): 1-10 [Abstract] ( 319 ) PDF (1210 KB)  ( 988 )
11 Critical hydraulic conditions of jet-rotary joint cascade inner energy dissipator
DENG Yuchen, NIU Zhengming, LI Qilong, NAN Junhu, WANG Tianshi
DOI: 10.11660/slfdxb.20190402
Scale model tests and theoretical analysis are used in this study to examine the pressure characteristics and critical hydraulic conditions of a new jet-rotary joint cascade inner energy disspator that combines a submerged jet with a horizontal rotary flow. The results show that when the submergence above the crown of the jet nozzle exit is no less than 20% of its diameter, a bi-stable flow regime is formed ? a stable submerged jet and a stable horizontal rotary flow. In this case, the wall pressure features with obviously staged variations along the tunnel in the jet section and horizontal rotary flow section, with the maximum relative pressure drops of 0.75 and 0.72 across the two sections respectively. Pressure at the jet exit is increased linearly with the increasing water depth in the shaft. Relative pressure at the rotation generator exit depends on the Froude numbers at this exit and the rotation blocking contractor exit and also on the water level drop from the vertical shaft to the tunnel tail water; it is decreased linearly with an increase in any one of these three factors. We give the critical hydraulic conditions for the dissipator to operate in the bi-stable regime: the Froude number at the jet exit as an upstream condition, and the pressure at the rotation generator exit as a downstream condition. The results would help the design and optimization of jet-rotary joint cascade inner energy dissipators and their engineering application.
2019 Vol. 38 (4): 11-20 [Abstract] ( 215 ) PDF (946 KB)  ( 415 )
21 Experimental study on characteristics of open channel flows with submerged rigid vegetation
SONG Yingting, JING Hefang, ZHANG Kai, HUANG Lingxiao, LI Chunguang
DOI: 10.11660/slfdxb.20190403
Submerged rigid aquatic vegetation can be found in a large number of water bodies, such as oceans, rivers, reservoirs, lakes, and canals. Vegetation could impose a great impact on flow structure, riverbed scour and silting, flood process, and navigation; and a systematic study of river flows with vegetation is fundamental to better understand the impact of aquatic vegetation on river flows. In this work, we model rigid aquatic vegetation with arrays of glass rods, and measure the open-channel flows on a laboratory flume using a three-dimensional laser Doppler velocimeter (LDV). Four vegetation arrangements are examined ? parallel arrangements with full-coverage and semi-coverage, staggered arrangements with full-coverage and semi-coverage ? with each being tested under four submergences. Systematic analysis of the measurements reveals that the density, arrangement and submergence of vegetation are closely related to water surface gradient, head loss, flow velocity, and turbulence intensity.
2019 Vol. 38 (4): 21-32 [Abstract] ( 286 ) PDF (3167 KB)  ( 564 )
33 Processes of bank collapse in lower Black River on Zoige Plateau based on the hydrograph
YANG Hanyuan, LI Zhiwei
DOI: 10.11660/slfdxb.20190404
Bank erosion and collapse play an important role on sediment transport in alluvial channels and lateral migration of meandering rivers. A combination method of field measurement, discharge frequency analysis, and numerical simulation (BSTEM), based on the prototype data of bank profiles, is used to study bank failure process and bank toe erosion and collapse in a Ω-shaped bend of the lower Black on the Zoige Plateau under constant and variable discharges. The results show that under constant discharges, bank erosion rate and retreat width are increased with discharge; while under variable discharges, both are nearly the same as those under the constant discharges with the same averages and are increased with the discharge average, indicating that the bank erosion rate and retreat width are independent of the shape, peak discharge, or dispersion of hydrographs. This means that bank erosion is affected by the magnitude of discharge and its frequency, and the erosion rate of bank toe and the bank retreat width are mainly controlled by average discharge, rather than the shape of hydrograph or peak discharge.
2019 Vol. 38 (4): 33-42 [Abstract] ( 214 ) PDF (1715 KB)  ( 432 )
43 Preliminary study on effect of characteristic flow rates on formation and development of channelized ditches
LEI Yunlong, HU Peng, CAO Zhixian, LIU Huaihan, LI Wei
DOI: 10.11660/slfdxb.20190405
Channelized ditches often occur on channel bars in a braided river, promoting the mobility of the bars and affecting the stability of river regime. Formation and development of these ditches is primarily a comprehensive response of the river to its volatile runoff. To explore the channeling sensitivity to river flow rates, a two-dimensional depth-integrated water-sediment-morphodynamic model is used in this work to study the erosion and deposition process of channel bars under different flow rates, and the formation and development of the ditches is reproduced numerically. Results show that the formation and development is closely related to the river’s characteristic flow rate. 1) When the river flow rate is small and the water cannot flow over the bar, the flow runs through the left and right branches and no ditch will be generated; 2) When the flow rate is in the medium range and the water just flows over the bar with a small depth on the bar, flow exchange between the two branches occurs through streams passing over the low-lying part of the bar bridge, and these streams will scour the bar and create channelized ditches; 3) When the flow rate is large and a major part of the channel bar is underwater, the flow exchange is weakened and no ditch can be generated. This study also shows that at different characteristic flow rates of the river, the location of ditch formation will swing. And the threshold of the characteristic flow rates for the ditch to form and develop depends, to some extent, on the planar shape of the channel bar. The results of this work would be useful for the study of the stability of channel bars in branched rivers.
2019 Vol. 38 (4): 43-52 [Abstract] ( 243 ) PDF (4315 KB)  ( 549 )
53 Variations and correlations of pollutants in water and sediment in sponge campus
HOU Jie, SUN Qiuhui, GUO Qizhong, KANG Hongzhi, WANG Huiqi, LIU Xun, ZHU Kaixuan, CHEN Liang
DOI: 10.11660/slfdxb.20190406
The Peiyang Park campus of Tianjin University is a pilot project of sponge campus construction. This paper focuses on the pollutants variation of the water and sediments in a artificial water system in the Peiyang Park campus, and the pollutants correlation between water and sediments are also analyzed by examining the correlation coefficients and multiple regression determination coefficients of the monitoring data. The results show that the water pollutants concentration are mainly determined by pollution sources and water mobility, with a low level observed in summer and a high level in winter. Most of the monitored water contaminants are nitrogen (total nitrogen from grade IV to worse than grade V and ammonia nitrogen from grade III to V) and chemical oxygen demand (COD from grade IV to worse than grade V). The sediment contaminants have no significant seasonal concentration fluctuation observed in this study, and their major components are nitrogen (total nitrogen content of 0.1-17.1 mg/kg and ammonia nitrogen content of 0.6-4.7 mg/kg) and chemical oxygen demand (COD content of 26.9-190.4 mg/kg). In addition, the sum of the determination coefficients of contaminant concentration in water and sediment is larger or smaller than the coefficient of the whole water system (i.e. contaminant concentration of water plus contaminant concentration of sediment). This indicates that the contaminants in the man-made water system are affected by the water and sediment together and significant correlations exist between the water contaminants and sediment contaminants.
2019 Vol. 38 (4): 53-62 [Abstract] ( 223 ) PDF (1467 KB)  ( 421 )
63 Characteristics and effects of different density flows in tributaries of Three Gorges reservoir in summer
HUANG Jiawei, JI Daobin, SONG Linxu, LIU Defu, HUANG Yanan, XU Hui, LIU Xinyuan, PING Mingming, ZHAO Chong
DOI: 10.11660/slfdxb.20190407
Flow velocity, water temperature, nutrients and chlorophyll-a were monitored in the three tributaries (Xiangxi Bay, Daning Bay and Xiaojiang Bay) of the Three Gorges reservoir (TGR) in July 2017 to study the characteristics of density flow and its influence on thermal stratification, nutrients distribution and algal blooms in this reservoir. The results show that bidirectional density currents could be a common flow pattern in these tributaries, and they are primarily caused by the difference in water temperature between the mainstream and tributaries in summer. And the water from the TGR mainstream intrudes into the three tributaries from middle layers, and the backward density currents feature with a depth and thickness mainly related to the water temperature distribution in the tributary estuaries. Under the influence of the mainstream backward flows, nutrients in the middle and lower streams of the three tributaries generally exhibit a vertical distribution structure of “middle layer > bottom layer > surface layer”. Since phosphate rock miners are located upstream of the Xiangxi Bay, its TP concentration presents a tendency of gradual decreasing from upstream to downstream, quite different from the other tributaries. Temperature difference between the mainstream and tributaries varies across the three tributaries, and it results in differences in the intensities of backward flows into the tributaries. The backward flow will play a crucial role in the thermal stratification and the species and intensity of algal blooms in the tributary bays, and then dominate the algal blooms.
2019 Vol. 38 (4): 63-74 [Abstract] ( 227 ) PDF (771 KB)  ( 595 )
75 Characteristic parameters of hydraulic boundary at embankment breaches based on cluster analysis
MA Hongfu, SUN Dongpo, LIU Mingxiao, DONG Mingjia
DOI: 10.11660/slfdxb.20190408
Hydraulic boundary conditions at an embankment breach must be specified to study the mechanism of embankment breaching or breach repair technologies, but accurate specification of these conditions is difficult due to incomplete measured data and the complexity and disparity of a real breach. In this work, we collect and analyze 100 groups of prototype data and experimental test data of embankment failure and earth dam failure, and establish the correlation between the parameters charactering the hydraulic boundaries at embankment breaches and supplement the missing values through data correlation and fitting based on a cluster analysis approach. For a generalized typical breach, we obtain its hydraulic boundary parameters and related equations using statistical analysis of the probability density of its dimensionless parameters. The analysis shows that most of the breaches feature with a width of 20-100 m, a water head of 4-12 m, and a mean flow velocity of 2-8 m/s, and that the distribution probabilities of these parameters’ values are all in the range of 64%-71%. The probability densities of both the width-to-depth ratio and flow Froude number of the breach follow the normal distribution; the probability is roughly 55% of the former in the range of 3-8 and 60% of the latter in the range of 0.4-0.8.
2019 Vol. 38 (4): 75-86 [Abstract] ( 160 ) PDF (1316 KB)  ( 453 )
87 Optimal adjustment of year-end stage of multi-year regulating reservoirs based on expert system
XIA Zhiyuan, ZHONG Ping’an, XU Bin, LIU Weifeng, WANG Jufen
DOI: 10.11660/slfdxb.20190409
The year-end stage of a multi-year regulating reservoir is a significant control variable for coordinating current and future benefits. To optimize this control stage in the case of potential uncertainty in future reservoir inflows, this paper constructs a general framework for an expert system. By analyzing its causes and mechanism, we develop a method for generating inference data sources and implementing a procedure of reservoir stage reasoning in an interface machine. Application in a case study of the Tankeng reservoir shows that the year-end stage solution of the expert system is close to the optimal solution with only a small difference, and that other indicators, such as power supply stability and water resource utilization rate, are also at high levels. Thus, our method and expert system are practical and useful in the planning of annual power generation of multi-year regulating reservoirs.
2019 Vol. 38 (4): 87-95 [Abstract] ( 178 ) PDF (469 KB)  ( 520 )
96 Comparison of parameter estimation methods for exponential Gamma distribution
LI Hang, SONG Songbai, SHI Jihai
DOI: 10.11660/slfdxb.20190410
In view of the superiority of the exponential Gamma distribution in hydrological frequency analysis, application of six common parameter estimation methods adopting this distribution is discussed. Annual maximum flood peak series with historical data taken into account are calculated for the flood series recorded at six hydrological stations: Ankang, Huazhu, Linjiang, Pengshui, Shanxi and Wusheng. And statistical performance and accuracy of the design values are analyzed using Monte Carlo simulations to compare six methods: optimized curve fitting method, moment method, mixed moment method, linear moment method, maximum likelihood method, and ordinary entropy method based on the maximum entropy theory. We discuss the fitting of the exponential Gamma distribution, and use the AIC criterion and RMSE calculations to evaluate the fitting effect. The results show that the optimal curve fitting method and linear moment method achieve a satisfactory fitting effect in flood frequency analysis, and that better results of the optimal curve fitting method can be obtained when the linear moment method is used as a reference method.
2019 Vol. 38 (4): 96-107 [Abstract] ( 317 ) PDF (1353 KB)  ( 932 )
108 Seepage parameter inversion based on Bayesian theory and entropy-blind numbers
LV Peng, WANG Xiaoling, WU Binping, CHENG Zhengfei
DOI: 10.11660/slfdxb.20190411
The existing parameter inversion methods based on Bayesian theory consider only the randomness in inversion process, neglecting the grey and unascertained uncertainties in seepage parameters. This paper presents an inversion method for estimating seepage parameters based on Bayesian theory and entropy-blind numbers. This new method introduces the entropy-blind number theory into the inversion model, taking the parameters to be inverted as blind numbers and fully considering the uncertainties in inversion process. We use a differential evolution adaptive metropolis (DREAM) algorithm to derive the posterior distribution of seepage parameters, and adopt a response surface model to replace the seepage simulation forward model, thereby avoiding a large number of forward model simulations in the traditional Bayesian seepage parameter inversion method. Our new method and its accuracy are validated through example analysis and a case study of permeability coefficient inversion for the foundation of a concrete gravity dam.
2019 Vol. 38 (4): 108-118 [Abstract] ( 211 ) PDF (762 KB)  ( 499 )
119 Fragmentation process and habitat quality assessment of wetland landscape in Gansu Section of Heihe River Basin
HU Xin, YANG Dong, SHI San’e, LI Xin
DOI: 10.11660/slfdxb.20190412
Wetlands in the Gansu section of the Heihe basin play a crucial strategic role in the national ecological construction. Under the stress of social and natural factors, it is extremely urgent to formulate a planning to protect the wetland resources in this area. Based on remote sensing images, this paper selects landscape fragmentation indexes to analyze the fragmentation process of wetland landscape in the study area, and adopts the Integrated Valuation of Environmental Services and Tradeoffs (InVEST) model to comprehensively evaluate the eco-environmental quality of wetland resources in the two periods of 2000-2008 and 2008-2016. Results show that in 2000-2008, the total area of the wetlands of different types in the study area decreased significantly with the largest decrease in shrub swamps. Since 2008, the total wetland area has been increasing. The degree of landscape fragmentation in the study area continued to be lowered in 2000-2008, but began to improve after that. The eco-environmental quality of the wetlands in the study area is generally good, and the area of extremely important habitat wetlands accounts for 86%-94% of the total wetland area.
2019 Vol. 38 (4): 119-135 [Abstract] ( 189 ) PDF (2669 KB)  ( 397 )
136 Study on methods for determining acceptable risk level of dams
WANG Liping, LI Ningning, MA Haoyu, ZHANG Yanke, JI Changming
DOI: 10.11660/slfdxb.20190413
A F-N curve is an intuitive curve for describing the relationship between risk frequency (F) and consequence (N), and it is often combined with the as low as reasonably practicable (ALARP) criterion in determination of the acceptable level of social risks. The previous F-N curve methods suffer from several drawbacks, such as lack of theoretical basis, strong subjectivity, and poor generality for different regions or different risk categories. This paper develops an improved F-N curve through combination with a risk matrix. We integrate the risk criteria into a risk matrix and develop a method of rating the matrix elements by qualitative and quantitative evaluation, and then the risk matrix can be transformed into a F-N curve by using this method. To demonstrate its use, acceptable risk levels of water dams are calculated and compared with those of the traditional method. The results show that the improved F-N curve is more standard and more reasonable and is easy to apply to other types of risks.
2019 Vol. 38 (4): 136-145 [Abstract] ( 237 ) PDF (1134 KB)  ( 708 )
146 Global sensitivity analysis of hydro power generator unit system
ZHANG Jiesheng, XU Beibei, CHEN Diyi, LI Huanhuan, ZHANG Jingjing
DOI: 10.11660/slfdxb.20190414
Sensitivity analysis of a hydroelectric generating system is of great significance to the application and improvement of the modeling technologies. To describe the unbalanced hydraulic forces acting on the turbine blades, this paper presents analytical expressions that play a key role in linking the models of the governing system and generator units. And based on this, we develop a unified model of the hydroelectric generating system and conduct a sensitivity analysis of its 27 parameters using the extended Fourier amplitude sensitivity test (EFAST), focusing on the parameters sensitive to the angular speed and rotor centroid of the generator. Results show that 1) the generator angular speed sensitive parameters include unit self-adjustment coefficient, the penstock diameters of the runner inlet and outlet, rated flow, and rated main servomotor displacement. 2) The sensitive parameters to the rotor centroid at horizontal deflection offset are the mass eccentricity of the rotor and runner, self-adjustment coefficient, the diameters of the runner outlet and outlet, and rated servomotor displacement. 3) An obvious difference exists between the interaction effects of the global sensitivity parameters and other parameters on the oscillation swings in X-direction and Y-direction. 4) The sensitivity to oscillation offset is stronger than that to the parameters of generator speed. Hence, when using the unified model to analyze the vibration evolution, the generator speed should be adjusted first, then the generator rotor parameters.
2019 Vol. 38 (4): 146-159 [Abstract] ( 214 ) PDF (1300 KB)  ( 682 )
160 Influence of combination of surge shaft and pressure reducing valve on transients in long distance diversion pipeline of hydropower station
ZHANG Xiaoying, ZHANG Jian, ZHOU Tianchi
DOI: 10.11660/slfdxb.20190415
Based on the one-dimensional transient flow theory and the method of characteristics, two mathematical models, one for simulating the surge tank and the other for the pressure reducing valve, are developed and applied to a hydropower station with a long distance diversion pipeline. We simulate and compare the combination scheme of a single surge shaft and a pressure reducing valve with the scheme of a single surge shaft, considering the working principle of the surge shaft and the pressure valve and the control requirements of limiting the unit speed increasing rate and volute end peak pressure during the load rejection of all the units. It reveals that the combination scheme can reduce these two controlled factors significantly and effectively. In addition, we analyze the operation safety of the station adopting different types of pressure reducing valves, and determine the opening and closing rules of the valve and the principle of valve diameter selection.
2019 Vol. 38 (4): 160-168 [Abstract] ( 143 ) PDF (583 KB)  ( 502 )
169 Staged startup and economic operation of pumped strorage units in pumping modes
XIAO Yang, YANG Kailin, SONG Shaoqun, WANG Guanhong, MA Shijun
DOI: 10.11660/slfdxb.20190416
During the pumping operation of pump-turbine units in the Fujiang pumped storage power plant, the motor power varies greatly because of a short vane opening period, causing severe fluctuations in the grid frequency. To stabilize the operation, this paper formulates a scheme of staged linear vane opening for this plant. We examine the stability of unit operation under different vane openings based on the experimental data of a high-lift model runner, and develop a method to find the maximum vane opening for efficient and economical pumping operation through analysis on the relationships of vane opening and working head versus pump flow, shaft power and efficiency.. Comparative analysis on the pressure pulsations in pumping and generating modes reveal that the pressure pulsations in generating mode are much stronger than those in pumping modes, and that the scheme of staged linear vane opening also improves pumping operation. An analysis of the pumping operation in zero flow condition shows that during pump startup, either slow vane opening operation or a smaller target vane opening helps eliminate large pressure pulsations at zero flow. Calculations of the hydraulic transients show that at each stage of the pump startup in the staged linear opening scheme, fluctuations in water pressure and shaft power are weak and decay more quickly, the units run more stably, and the risk of pressure pulsations stronger than those in generating modes is very low. The conclusions above are also useful for other high-lift pump storage stations with similar unit flow, torque and pressure pulsations of the runners.
2019 Vol. 38 (4): 169-178 [Abstract] ( 205 ) PDF (1673 KB)  ( 575 )
179 Fault diagnosis of hydroelectric generating sets based on multi-dimensional features and multiple classifiers
CHENG Xiaoyi, CHEN Qijuan, WANG Weiyu, ZHENG Yang, GUO Dingyu, LOU Qiang
DOI: 10.11660/slfdxb.20190417
A fault diagnosis method of hydroelectric generating sets based on multi-dimensional features and multiple classifiers is developed. Multi-dimensional features are constructed by extracting time domain characteristics, frequency domain characteristics, and sample entropy of ensemble empirical mode decomposition from the vibration signals of the generating units in different working conditions, and reduced by the genetic algorithm, so that this new method can achieve multidimensional information complementarity in the vibration features. With the multi-dimensional features as classifier inputs, faults are diagnosed using the support vector machine classifier, back propagation neural network classifier, and naive Bayes classifier. The preliminary diagnosis results of the three classifiers are fused to draw the final diagnosis conclusion, thus improving the accuracy of fault diagnosis of the generating sets. To verify the method, rotor unbalance, rotor misalignment and rotor rubbing are simulated experimentally on a rotor test bench, and the method is used to diagnose these faults. The results show that the diagnosis accuracy of multi-dimensional features and multiple classifiers is much higher than that of the single dimension feature and single classifier.
2019 Vol. 38 (4): 179-186 [Abstract] ( 239 ) PDF (393 KB)  ( 559 )
187 Research on slope stability based on hydrological modeling
XIAO Yaoting, ZHU Yuelu
DOI: 10.11660/slfdxb.20190418
In traditional methods for slope stability analysis, it is difficult to obtain continuous long time series of soil water content. Using the data series of precipitation, temperature and vegetation coverage in the study area, this paper develops a variable infiltration capacity (VIC) hydrological model for calculating the daily variations in soil water content that is used as a key factor in slope stability analysis. The results show that during 1970-2010, the spatial-temporal distribution of soil water content in the Wei River basin took an increasing trend, and that soil shear strength was decreased but approached a stable level at about 2‰ less. Calculations of the strength reduction method based on the M-C equal-area circle DP3 criterion show that during this period, the slope stability factor k was increased, and its value of larger than 1.2 covers more than 85% of the time period, with only 9% in the range of 1.0-1.2 and 5.5% below 1.0. A R/S analysis on the soil shear strength time series reveals that the Hurst coefficients of the τ-t curve and k-t curve are 0.5568 and 0.5888, respectively, falling in the range of no variation. Based on the calculations, we conclude that the sliding bodies are stable at present and in future, and our VIC method is effective in calculations of soil water content, soil shear strength, and slope stability.
2019 Vol. 38 (4): 187-198 [Abstract] ( 274 ) PDF (3336 KB)  ( 477 )
199 Simulations of underground cavern construction based on M5P-SVR failure prediction
ZHONG Denghua, LIN Hanwen, WU Binping, ZHAO Mengqi, YU Jia
DOI: 10.11660/slfdxb.20190419
Simulations of underground cavern group construction are important to analysis of the construction process. It is difficult to achieve high-accuracy simulation of slag transportation time by using traditional simulation models that suffer from problems such as large subjective errors in quantifying the influence of transportation machinery failure on construction progress. This study develops a new simulation model of underground cavern group construction to predict this failure using a M5P-SVR model. This model improves the accuracy in two aspects. Firstly, it improves the slag module adopted in the traditional CYCLONE model and uses a transportation simulation circuit to calculate slag transportation time with an improved accuracy. Secondly, it considers certain external factors more rationally, adopts the simple, effective training rules of the M5P model tree, and is equipped with the support vector machine regression (SVR) that can effectively solve those nonlinear prediction problems that are based on small sample dataset. Combining these two advantages, we develop the M5P-SVR model based on a prediction method of transportation machinery faults, and verify its significant improvement on prediction accuracy using a cross validation method. Finally, our new model is applied to the simulations of a real project and compared with the traditional method, verifying its accuracy and superiority and the effectiveness of M5P-SVR.
2019 Vol. 38 (4): 199-212 [Abstract] ( 162 ) PDF (2311 KB)  ( 641 )
213 Study and application of superficial thermal insulation of Xiluodu super high arch dam concrete
FAN Qixiang, WU Kun, CHEN Wenfu
DOI: 10.11660/slfdxb.20190420
Deep cracks and penetrated cracks may develop from surface cracks, which are forming a major type of cracking in dam concrete, and therefore thermal insulation is a key measure to prevent concrete cracking. In construction of the Xiluodu super high arch dam, a systemic study on the schemes of surface insulation was conducted, including determination of technical standards, simulation analysis, optimization of construction schemes, and standard process studies. Based on this work, this paper describes a specific, fine insulation process of dam concrete that can meet the cracking control needs of super high arch dams. Comprehensive real-time site monitoring and site quality inspection on this arch dam shows that our insulation process achieves significant insulation effects and it can control the risk of cracking on the concrete surface effectively.
2019 Vol. 38 (4): 213-223 [Abstract] ( 227 ) PDF (983 KB)  ( 468 )
224 Reliability analysis of anti-sliding stability of a gravity dam foundation based on PLS-ELM dynamic response surface method
WANG Xiaoling, LI Xiao, ZHU Xiaobin, LIU Minghui, WANG Jiajun
DOI: 10.11660/slfdxb.20190421
Reliability analysis of the anti-sliding stability of complex foundations of gravity dams is faced with a large number of random variables and a strong nonlinearity in implicit performance functions, causing a convergence difficulty with the traditional response surface method and its low accuracy and high computational cost. To solve the problems, we develop a dynamic response surface method of partial least squares coupled with extreme learning machine (PLS-ELM) to estimate the reliability index of foundation anti-sliding stability. A response surface of implicit performance functions is constructed using ELM that is suitable for solving nonlinear regression problems of high-dimensional small samples. This surface is combined with the Monte Carlo simulation method through optimizing the number and input weights of hidden layer neurons with the PLS technique, and its dynamic update and the solution of reliability index are realized by constructing a reasonable iterative algorithm. Using this new dynamic method, we calculate the reliability index of foundation anti-sliding stability for a real dam. The results show its advantages of low computational cost, high accuracy and efficiency in response surface fitting, easy convergence, wide applicability, and easy integration with various methods or software for structural calculation. Thus, the method is suitable for the reliability analysis in the design of real projects. A case study demonstrates that a reliability index of 5.10 meets the standard requirements and the material parameters of soft interlayers have the greatest influence on the reliability of dam foundation anti-slide stability.
2019 Vol. 38 (4): 224-233 [Abstract] ( 209 ) PDF (1033 KB)  ( 446 )
234 Dynamic update of diversion tunnel construction simulation parameters based on ACDE-SVM
XIAO Yao, ZHONG Denghua, WANG Dong, LIN Weiwei, WANG Jiajun, LIU Zhen
DOI: 10.11660/slfdxb.20190422
Update of construction simulation parameters has a great impact on the accuracy of simulation results. Most previous studies use Bayesian theory to update these parameters but have to introduce an assumption of their probability distributions. Such methods cannot generate the series of predicted parameters necessary for describing their dynamic variations. To avoid these shortages, this paper presents a schedule simulation parameter update method for diversion tunnel construction, based on an adaptive chaos differential evolution-support vector machine (ACDE-SVM). First, we develop an ACDE algorithm by adopting an adaptive scaling factor and the chaos theory to improve the differential evolution, so that it can not only reduce the searching time but overcome the shortcoming of the differential evolution that is easy to become premature. Then, we optimize the SVM parameters using ACDE and the time series of onsite parameters, and construct an ACDE-SVM algorithm for predicting the schedule simulation parameters that can overcome the inefficiency of parameter selection and the weakness in generalization capability. Last, we adopt certain error indexes to evaluate this parameter update method and compare it with the conventional simulation and Bayesian method to demonstrate its consistency and superiority. A case study shows that the method can fit well the time trends of parameters and improve simulation accuracy.
2019 Vol. 38 (4): 234-245 [Abstract] ( 241 ) PDF (1450 KB)  ( 515 )
246 Strain energy conversion behaviors of sandstone after freeze-thaw cycles under triaxial confining pressure unloading
NI Xiaohui, SHEN Xiaomei, HUA Xinruo, FANG Jian
DOI: 10.11660/slfdxb.20190423
Stress-strain properties and strain-energy conversion behaviors of sandstone are studied by conducting freeze-thaw cycling tests and triaxial tests under unloading conditions to understand the mechanical properties of sandstone surrounding an underground tunnel in a cold region. Results show that with the increasing number of freeze-thaw cycles, peak strength in the unloading yield process is significantly reduced and the strain varies gradually. Time variations in strain energy can be divided into four stages. During the pre-peak unloading, most of the strain energy due to axial pressure is converted into elastic strain energy, and the damage caused by freeze-thaw cycling intensifies this conversion. After the peak, the stored elastic strain energy is rapidly released, and the energy dissipated by plastic deformation and damage is rapidly increased. The strain energy consumed by circumferential deformation also increases rapidly. The failure mode of the specimens shows obvious characteristics of tensile failure. With the increasing freeze-thaw cycles, the number of tensile cracks increases and particle breakage becomes more pronounced. The results reveal the fundamental behaviors of strain-energy conversion and improve our understanding of the damage and failure of frozen rock in unloading.
2019 Vol. 38 (4): 246-255 [Abstract] ( 194 ) PDF (2906 KB)  ( 543 )
256 Hydrodynamic performance analysis of vertical axis helical triangular blades
ZHU Guojun, JING Xinxin, FENG Jianjun
DOI: 10.11660/slfdxb.20190424
This paper describes a new runner with helical triangular blades that enhances the stability of energy output of vertical axis hydraulic turbines and improves the traditional straight blade H-type runner. In this work, we design four helical triangular blades of different helical warp angles of 15°, 30°, 45° and 60° at mid-span, and examine the influence of warp angles on the hydraulic performance of these blades using computational fluid dynamics analysis. The results reveal that this type of blades increases the power coefficients of the runner and the improvement is most obvious in the condition of large tip speed ratios. And a greater helical warp angle leads to a more stable power output of the runner. A comprehensive comparison shows that a runner with the warp angle of 15° has the best performance, increasing its power coefficients by up to 13.4%; and its stability of energy output is also improved. We compare the vorticity fields between the traditional and modified runners and find out that the helical triangular blade effectively reduces the sizes of the blade wake vortices and the amplitudes of pressure fluctuations on blade surface. All our results indicate that the helical triangular blades help improve the operation stability of vertical axis hydraulic turbines, and that the modified runner, as a tidal energy device, could be adopted to replace the traditional one.
2019 Vol. 38 (4): 256-264 [Abstract] ( 203 ) PDF (1215 KB)  ( 595 )
265 Hydrodynamic performance of tidal current ducted turbines
SONG Ke, WANG Wenquan, YAN Yan
DOI: 10.11660/slfdxb.20190425
To improve the power output of a tidal energy conversion turbine system, a new type of horizontal axis ducted turbines is studied using a Reynolds Averaged Navier Stokes (RANS)-CFD method, focusing on modeling power output, load, cavitation, flow unsteadiness, and the effect of attached ducts. A towing tank experiment is carried out to validate the numerical simulations. The results show that a ducted turbine has higher power output and larger axial thrust than those of the bare turbine and can maintain high power output within ±30° of the yaw angle. And it is featured with non-cavitation and satisfactory flow unsteadiness under design conditions. For a multi-ducted turbine, large attached ducts can improve its power and thrust in the full range of tip-to-speed ratio and further improvement can be achieved if the angles of attack of the ducts are increased, while small duct sizes are not conducive to the power output. Thus, this study demonstrates the advantages of the ducted turbine and its broad prospect of engineering application.
2019 Vol. 38 (4): 265-272 [Abstract] ( 208 ) PDF (1099 KB)  ( 551 )
Copyright © Editorial Board of Journal of Hydroelectric Engineering
Supported by:Beijing Magtech