Table of Content

25 April 2017, Volume 45 Issue 4

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Power & Electrical Engineering

Influence of Reactive Power Dynamics of HVDC System on Short-Term Voltage Stability

CAI Ze-xiang FENG Lei YANG Huan-huan ZHU Lin ZHANG Dong-hui ZHOU Bao-rong

2017, 45(4):  1-7.  doi:10.3969/j.issn.1000-565X.2017.04.001

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In this paper,first,the post-fault HVDC ( High-Voltage Direct Current Transmission) reactive power change laws in time domain are analyzed by using the quasi-steady model of HVDC system.Next,the amplitude and time features of reactive power change are explored through simulation.Then,by comparatively analyzing the reactive power change with or without HVDC,the reactive power recovery delaying effect that HVDC reactive power dynamics exert on the induction motor is illustrated,and the mechanism and pathway by which HVDC reactive power dynamics influence the short-term voltage stability are explored.Finally,an index,namely the change rate of critical slip of induction motor,is proposed to evaluate the influence of HVDC reactive power dynamics on the short-term voltage stability,and the effectiveness of the proposed method is verified by an application example on China Southern Power Grid.

Fast Proximate Calculation of Dynamic Reactive Power Peak Demand in Inverter of HVDC

XIA Cheng-jun LAN Hai-wen DU Zhao-bin ZHOU Bao-rong HONG Chao

2017, 45(4):  8-14,29.  doi:10.3969/j.issn.1000-565X.2017.04.002

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Dynamic reactive power compensation devices are effective in improving the voltage stability of the receiving end.In this paper,a fast proximate calculation method of dynamic reactive power peak demand in inverter after large disturbances is proposed to determine the capacity of dynamic reactive power compensation devices.In the investigation,first,the direct-current control mode is determined and the control links that play a major role in HVDC ( High-Voltage Direct Current Transmission) during the failure recovery are retained after a detailed analysis of HVDC control system.Next,the elements that determine the dynamic reactive power characteristics of the inverter are defined and the impact of disturbance severity on the elements is analyzed,which helps to clarify the mechanism by which the peak value of dynamic reactive power consumption of the inverter is relatively fixed.Then,some system parameters are properly processed without considering the impact of disturbance severity to estimate the dynamic reactive power characteristics after different AC voltage drops with a unique peak curve.Moreover,the differential equitation describing the simplified HVDC system is presented and the dynamic reactive power peak demand is obtained.Finally,the estimated demand value is used to determine the capacity of the dynamic reactive power compensation device installed in the receiving power network.Simulated results on Chu-Sui HVDC PSCAD/ EMTDC model show that the estimated dynamic reactive power peak is correct,and that the proposed design method of dynamic reactive poser compensation devices is feasible.

Denoising of Infrared Images of Porcelain Sleeve Cable Terminal Considering Inter-Scale Correlation

NIU Hai-qing WU Ju-zhuo XU Jia WU Qian GAO Zi-jian ZHENG Wen-jian

2017, 45(4):  15-21.  doi:10.3969/j.issn.1000-565X.2017.04.003

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In order to effectively suppress the noise of images and improve the accuracy of infrared diagnosis of electrical equipment,a denoising method based on both the wavelet coefficients’inter-scale correlation and the bivariate shrinkage function is proposed to denoise the infrared images of porcelain sleeve cable terminals.In this method,first,the wavelet transform coefficients are separated into two sorts by means of fuzzy c-means clustering according to the calculated inter-scale correlation coefficients of wavelet coefficients,namely,the efficient coefficients and the invalid coefficients.Then,the invalid wavelet coefficients are directly set to zero,while the efficient wavelet coefficients are processed with the bivariate shrinkage function.Thus,the estimated values of image's wavelet coefficients are obtained.Finally,the estimated wavelet coefficients are used to reconstruct a denoised image.The denoising results of infrared images with noise show that,as compared with the traditional soft thresholding method,the proposed method is more effective because it improves both the signal-to-noise ratio and the mean square error.

Determination Method of Current-Carrying Capacity of HVAC Cable Joint Based on ANSYS

LIU Gang WANG Peng-yu WANG Zhen-hua XU Tao LIU Yi-gang HAN Zhuo-zhan

2017, 45(4):  22-29.  doi:10.3969/j.issn.1000-565X.2017.04.004

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In order to accurately calculate the current-carrying capacity of HVAC ( High-Voltage AC) cable joints,a method based on ANSYS,which employs the two-dimension finite element simulation model of the joint in axial direction and takes the insulation's long-term tolerating temperature as the constraint condition,is presented,and,a simulation is performed,finding that,under the same natural convection and load conditions,the temperature of the joint conductor is higher than that of the cable conductor with equal sectional area,while the current-carrying capacity of the cable is better than that of the joint.Then,in order to verify the precision of the simulation model,an experimental platform to measure the joint's current-carrying capacity is established,and the practical steadystate temperature distribution of the 110 kV cable joint under different loads is measured.Moreover,a comparative analysis is carried out between the simulated and the experimental results,finding a 1. 0% error of the cable joint conductor's temperature calculated with the finite element simulation model when the temperature exceeds the insulation's long-term tolerating temperature,which means that the accuracy of the calculation results may satisfy the demand of engineering application.Finally,a current-carrying capacity of 1220A is obtained for the 10 kV 630 mm2 cable joint by using the dichotomy,which is 17. 79% less than that of the cable body with the same conductor cross section under the same environmental conditions.Thus,it is concluded that the proposed two-dimension finite element simulation model of the joint in axial direction is feasible in calculating the current-carrying capacity.

Coordinated Optimal Allocation of Distributed Wind Generator and Battery Energy Storage in Distribution Network

OUYANG Sen CHEN Xin-hui YANG Jia-hao

2017, 45(4):  30-36,43.  doi:10.3969/j.issn.1000-565X.2017.04.005

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The location and capacity of distributed wind generator ( DWG) and the battery energy storage ( BES) both affect the operating state of the distribution system.In order to improve the wind power accommodation capacity of the distribution system and weaken the effect of wind power output uncertainty,a coordinated optimal allocation for the locating and sizing of DWG and BES is performed in the planning stage.Then,a chance-constrained programming model,of which the objective function is to maximize the annual comprehensive income,is established by taking into consideration the stochastic power flow of the wind-storage system to reflect the operating state and the uncertainty of the distribution system containing DWG and BES.Moreover,an improved multi-population genetic algorithm is proposed,and an effective searching optimal mechanism is introduced to enhance the performance of the algorithm.Simulated results on the IEEE 33-bus distribution system show that the proposed optimization model is rational and that the proposed algorithm is effective.

Compensation Capacitor Optimization for Low-Frequency Magnetically-Resonant Coupling Wireless Power Transfer System

YANG Jin-ming XIE Xing-lang XIANG Ru-yi CHEN Yuan-rui

2017, 45(4):  37-43.  doi:10.3969/j.issn.1000-565X.2017.04.006

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In this paper,by analyzing the effects of coupling coefficient,resonant frequency and coil resistance on the transfer efficiency and output power of magnetically-resonant coupling system in low-frequency state,the relationship between the compensation capacitor of drive coil /load coil in non-resonant state and the output power as well as the transfer efficiency is established.In addition,a simplified calculation method of the optimized compensation capacitor is proposed.Experimental results show that the proposed method is adaptable and effective in power and efficiency optimization.

Improved Probabilistic Load Flow Calculation of Distribution Grids with Distributed Generation

HUANG Yu XU Qing-shan LIU Jian-kun WEI Peng

2017, 45(4):  44-50,58.  doi:10.3969/j.issn.1000-565X.2017.04.007

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With the continuous increase of the proportion of distributed generations ( DG) in distribution grids,power systems face more and more challenges,such as the increase of uncertainty and the change of grid structure.The conventional load flow calculation method is unable to deal with such a great number of uncertainties in grids.In order to solve this problem,a probabilistic load flow calculation method based on the imperialist competitive algorithm ( ICA) is proposed,which can easily take into account all kinds of topology structures,different DG penetration levels and multiple constraint conditions of complicated networks,with good convergence as well.Moreover,for the purpose of improving the searching ability and convergence rate of the algorithm,a clone evolution operator is introduced in ICA.The modified IEEE-33 distribution system is used for simulation and the results are compared with those obtained via Monte Carlo simulation ( MCS) .It is found that the proposed method is of high precision and great practical value.

Power Supply System for LLC Resonant Charging of Electric Vehicles

WU Kai-yuan WANG Jia-jia YIN Tong ZHANG Tao

2017, 45(4):  51-58.  doi:10.3969/j.issn.1000-565X.2017.04.008

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Proposed in this paper is a STM32-based LLC resonant charging power supply system for electric vehicles,which employs digital PFM ( Pulse Frequency Modulation) for the system control and adopts an LLC resonant topology as well as a four stages + positive and negative pulse charging scheme that meets the charging requirements of lead-acid battery.Test results demonstrate that ( 1) the proposed power supply system helps to implement the whole-course soft switching state of the main circuit of LLC resonant converters; ( 2) the main circuit of LLC resonant converters always operates in the primary-side MOSFET ZVS and the secondary-side rectifier diode ZCS softswitching state,which improves the power conversion efficiency; and ( 3) the combination of battery charging curves and four stages + positive and negative pulse charging scheme can reduce the overcharging as well as gassing polarization,protect the battery and increase the charging speed.

Insertion-Extraction and Temperature Rise Properties of Electrical Connector

HE Zhan-shu ZHANG Yuan-xi WANG Pei-zhuo TANG Yong SHAO Li-na

2017, 45(4):  59-65,80.  doi:10.3969/j.issn.1000-565X.2017.04.009

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Excessive or inadequate contact force of electrical connector may result in unsmooth insertion-extraction and excessive contact resistance and further cause contact failure.In order to improve the contact reliability of electrical connectors,the insertion-extraction and temperature rise properties of an electrical connector were discussed.In the investigation,first,the insertion-extraction force and temperature rise of the contactor were simulated by using ABAQUS.Then,the effect of clearance between spring and support frame δ and angle of spring tongue α on the insertion-extraction force,as well as the influence of wire's cross-sectional area S and current on the temperature rise were revealed.Finally,the variations of insertion-extraction force and temperature rise were measured by experiments.The results show that ( 1) when δ = 0. 12mm,the insertion-extraction force increases with the increase of α; while when δ = 0. 18mm,the insertion-extraction force first increases and then decreases with the increase of α; ( 2) when α is constant,the insertion-extraction force decreases with the increase of δ; ( 3) the temperature rise of the contactor increases with the increase of current,but decreases with the increase of wire's cross-sectional area; and ( 4) the insertion-extraction force and temperature rise obtained by experiments are consistent with those obtained by simulation.Comprehensively considering the insertion-extraction force and temperature rise,the optimal parameters for the connector are suggested as δ = 0. 12mm and α = 15°.

Traffic & Transportation Engineering

Dynamic Performance Analysis of Asphalt Pavement Under Moving Vehicle Load and Seasonal Temperature Variation

2017, 45(4):  66-73.  doi:10.3969/j.issn.1000-565X.2017.04.010

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In order to reveal the effect of seasonal temperature variation in the areas with large temperature difference on the performance of asphalt pavement,this paper takes into consideration the time-temperature viscoelasticity of asphalt concrete,and performs numerical simulations to analyze the dynamic behavior and performance under moving vehicle load and seasonal temperature variation for two kinds of typical asphalt pavement structures.One is the structure with a semi-rigid base layer containing cement-stabilized macadam ( structure S1) and the other with a flexible base layer containing graded aggregate materials ( structure S2) .The results show that ( 1) with the increase of axle load,the decrease of dynamic load frequency,the change of horizontal thrust direction from the opposite to the same direction of the moving vehicle,or with the deterioration of interlayer conditions,the stress at the bottom of the asphalt layer generally increases，while the fatigue life gradually decreases; ( 2) the variation of pavement temperature distribution significantly influences the tensile stress of each structural layer in summer but slightly influences the stress in winter; ( 3) at the bottom of the surface layer,the tensile stress in summer or at high temperature is less than that in winter or at low temperature,while the base layer shows an opposite trend in this regard; and ( 4) although the fatigue lifetime of the asphalt layer of structure S1 under various age and temperature conditions is longer than that of structure S2,it has a deficiency of drastic fluctuation,while S2 has a relative stable fatigue behavior and a superior environmental adaptability.

Reinforcement Design of BFRP-Reinforced Continuously-Reinforced Concrete Pavement

ZHANG Li-juan XU Zhong-zheng ZHONG Qing-wen

2017, 45(4):  74-80.  doi:10.3969/j.issn.1000-565X.2017.04.011

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In this paper,first,a model to describe the uniform temperature drop of BFRP ( Basalt Fiber-Reinforced Plastics) bar-reinforced CRCP ( Continuously Reinforced Concrete Pavement) is proposed.Next,by taking into consideration the dry shrinkage of concrete and the constraint by base,the formulas for the analytical solution of such crack control indicators as crack spacing,crack width and reinforcement stress are derived and verified through finite element simulation.Then,the effects of BFRP bar design and the corresponding material properties on crack control indicators are analyzed,and the indicators for the reinforcement design of BFRP-reinforced CRCP are recommended.The results show that ( 1) the crack spacing,crack width and reinforcement stress of BFRP bar all decrease with the increase of the percentage of longitudinal reinforcement,and smaller diameter and spacing of BFRP bar is better for the control of cracks at the same percentage of longitudinal reinforcement; ( 2) with the increase of the elastic modulus of BFRP bar and with the bond stiffness between BFRP bar and concrete,both the crack spacing and the crack width decrease,while the reinforcement stress of BFRP bar almost remains unchanged; and some engineering countermeasures should be adopted to improve the elastic modulus of BFRP bar and the bond stiffness coefficient between BFRP bar and concrete.Moreover,for the reinforcement design of BFRP-reinforced CRCP,three crack control indicators are recommended,namely an average crack spacing limit of 2. 0 m,a crack width limit of 1. 0mm and a percentage of longitudinal reinforcement of not less than 0. 6%.

Effect of Multi-Point Laser-Based Configurations on Calculation Error of Rut Depth Measurement

HUI Bing XIE Yi-qiong GUO Mu

2017, 45(4):  81-86,123.  doi:10.3969/j.issn.1000-565X.2017.04.012

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In order to evaluate the accuracy of the multi-point laser-based rut depth measurement,first,an indoor rut pattern simulator was developed,and the point cloud data in the transverse section were measured by means of 3D laser technology.Next,by virtue of Matlab programming and fifth-order Butterworth low-pass filter,the rut transverse-section curves acquired by the uniform 9-point,13-point,21-point and the non-uniform 13-point lasers were simulated,respectively.Then,the wire line method was employed to calculate the maximum rut depth of 3D laser and multi-point laser.Finally,the influences of the laser point number and the layout scheme on the calculation error of U-shape and W-shape ruts with low and high severity were analyzed by taking absolute error and relative error as the evaluation indexes.The results show that ( 1) the depth calculation error of the two above-mentioned rut transverse sections gradually decrease with the increase of the laser point number; ( 2) the maximum relative errors of the uniform 9-point,13-point,21-point and the non-uniform 13-point lasers are 22. 9%,12. 8%,8. 3% and 16. 4%,respectively; ( 3) with the augment of rut severity,the absolute error increases gradually while the relative error declines; ( 4) the relative errors of the U-shape and W-shape rut depth calculation by using the non-uniform 13-point lasers are respectively 4. 8% and 2. 2% larger than those of the uniform 13-point laser; and ( 5) the absolute error of rut depth calculation via multi-point laser may cause the underestimation of rut severity level,which may result in the loss of perfect time for maintenance.

Frost Resistance of PE/HPP Hybrid Fiber-Reinforced Concrete

HE Ｒui LI Dan WANG Shuai CHEN Hua-xin

2017, 45(4):  87-94.  doi:10.3969/j.issn.1000-565X.2017.04.013

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In this paper,first,hybrid fiber-reinforced concrete was prepared by using the hybrid fiber of polyethylene fiber ( PE) and polypropylene plastic fiber ( HPP) .Then,the frost resistance of the reinforced concrete before and after the freeze-thaw process was investigated in terms of quality variation,dynamic elasticity modulus,compressive strength and flexural performance.Finally,the damage mechanism of the concrete was analyzed by using SEM analysis technique.The results show that ( 1) freeze-thaw cycles may cause obvious damage to plain concrete,and hybrid fiber can improve the integrity of concrete and decrease the surface damage; ( 2) the quality of plain concrete first increases and then decreases in the freeze-thaw cycle,while that of the hybrid fiber-reinforced concrete continuously increases; ( 3) the dynamic elastic modulus of the concrete with different proportions almost remains unchanged at first and then decreases; ( 4) after 300 freeze-thaw cycles,the relative dynamic elastic modulus of the concrete with a fiber content of 0. 8% + 1. 2% still keeps at 83. 63%; ( 5) the variation rule of compressive strength is similar to that of the dynamic elastic modulus; ( 6) the synergistic effect of fine-PE and coarse HPP fibers significantly improves the brittleness of concrete; ( 7) both the toughness index and the residual strength of hybrid fiber-reinforced concrete vary with the fiber content; ( 8) the prepared reinforced concrete is superior to the ideal elastic-plastic material when the hybrid fiber content is 0. 8% + 1. 2%; and ( 9) freeze-thaw cycles may result in certain damage to the flexural toughness,but still no brittle fracture appears,and the concrete still possesses good ductility.

Experimental Research on Dynamic Properties of CRTSⅡ Ballastless Track on Simply-Supported Beam

DAI Gong-lian LIU Xiang-yu LIU Wen-shuo

2017, 45(4):  95-102.  doi:10.3969/j.issn.1000-565X.2017.04.014

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In order to explore the dynamic performances of continuous CRTSⅡ ballastless track slab-bridge system,a multi-point measuring system was established.With the help of this system,the dynamic response of each component of the system was observed in detail,and the lateral acceleration,vertical acceleration and vertical displacement of the CRTSⅡ track slab system,as well as the natural vibration frequency,damping ratio and impact coefficient of the beam,were analyzed statistically.The results show that ( 1) CRTSⅡ track slab system has a good capability of buffering train-induced vibrations,with a total vibration reduction rate of more than 90%,a maximum vertical acceleration of bridge deck of 3. 93m/s2 and a maximum vertical displacement of 0. 131 4 mm after the vibration has been transferred to the bridge deck,which meets the requirements of the related standards; ( 2) the train load-induced vibration has a slight effect on the adjacent railway,which focuses on the fixed support side; ( 3) the train load-induced vibration is primarily positively related to the train speed,and parts of the structure may vibrate differently from the track slab-bridge system at a special train speed,which may lead to cracks or damage; and ( 4) the measured one-order natural vibration frequency of simply-supported beam in the CRTSⅡ track slab-bridge system is about 7. 27Hz,which is slightly greater than the theoretical one of the simply-supported beam without track slab.

Speed Planning Method of Vehicles in Economical Cruise State

ZHANG Li-bin LIU Huan-feng SHAN Hong-ying YANG Yu-lin

2017, 45(4):  103-111.  doi:10.3969/j.issn.1000-565X.2017.04.015

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In order to improve the fuel economy of expressway running vehicles in adaptive cruise state,a speed planning model of vehicles in economical cruise is established.The model plans vehicle's economical cruising speed according to road conditions and climate environment parameters,First of all a test environment is constructed to perform a traverse test,and a database of fuel consumption per hundred kilometers is established.Then,in order to predict the economical speed under different driving resistances,the mapping relationship between running speed as well as running resistance and fuel consumption is revealed based on the related theory of cloud model.Finally,the speed change trajectory in economical cruise state is planned according to the economical vehicle speed.Test results show that the fuel consumption of the vehicle along the economical cruising speed change trajectory reduces significantly and fuel economy is effectively improved.

Active Torque Control of Tractor-Trailer Combination Based on Genetic Algorithm Optimization

ZHANG Yi-hua XU Hong-guo LIU Hong-fei

2017, 45(4):  112-117.  doi:10.3969/j.issn.1000-565X.2017.04.016

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In order to improve the lateral stability and driving safety of tractor-trailer combination,a tractor-trailer combination model considering active torque control was built,and the minimum of the sum of rear amplification factor ( RWA) and sideslip angle was used as a fitness function for the genetic algorithm to design an linear quadratic ( LQR) controller,by which the optimal active torque was obtained and then feed back to the vehicle model.As compared with the vehicle model without LQR controllers,the proposed model with active torque control can avoid the snaking of the dolly and the second semitrailer,reduce the RWA by 7. 9%,and help each unit of the vehicle combination to quickly reach a steady state.However,the proposed strategy for sideslip angle control in each vehicle unit is not as precise as for yaw rate control.

Location Model for Public Electric Bicycle Rent Based on Bi-Level Programming

HU Yu-cong CHEN Zhi-wei HUANG Jing-xiang

2017, 45(4):  118-123.  doi:10.3969/j.issn.1000-565X.2017.04.017

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Developing public electric bicycle systems is a feasible way to making full use of resources and meeting people's increasing demand for low-carbon trips.This paper first proposes a public electric bicycle network system based on trip chain analysis,and then establishes a bi-level programming model to solve the station location problem of such systems.In this model,the upper part considers the government's goal for system optimization,while the lower part shows respect for system users'interests and user equilibrium.The upper model is solved by using the hybrid particle swarm optimization algorithm and the lower one is solved by using Frank-Wolfe algorithm.Numerical results show that the proposed programming model can determine both the optimal location and the size of stations in the public electric bicycle network system with good convergence.

Optimization Model to Locate Exclusive Urban Bus Lanes Considering Time Dimensionality

LU Xiao-lin PAN Shu-liang ZOU Nan

2017, 45(4):  124-131,144.  doi:10.3969/j.issn.1000-565X.2017.04.018

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Aiming at the location and construction sequence approach of exclusive urban bus lanes in a certain planning period,this paper analyzes the location and construction practice as well as the dynamic change of realistic demands,and establishes a time-dependent bi-level optimization model to locate exclusive bus lanes.The upper level of the proposed model is a locating model to maximize the total consumer surplus in the whole road network,and the lower level is an allocation model of cars and buses to minimize the generalized travel cost.Then,with the help of genetic algorithm,the mentioned problem is solved.Moreover,a case study is performed to verify the effectiveness and practicability of the established bi-level model and to reveal the superiority of the proposed approach considering time dimensionality to the simply-phased sequential approach.The results show that the established model can simultaneously optimize the location and construction sequence of exclusive bus lanes.

Development and Test Verification of Underwater Photogrammetry Measurement System

CHEN Yuan-ming YE Jia-wei WU Jia-ming

2017, 45(4):  132-137.  doi:10.3969/j.issn.1000-565X.2017.04.019

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Proposed in this paper is an underwater photogrammetry system for towing test,which is based on the principle of close-range photogrammetry.In this system,two underwater cameras are installed on the towing carriage to take photo synchronously in a certain frequency,and the obtained photos are processed in terms of image recognition and coordinate calculation.Thus,the movement trajectory and the attitude of the towed object is obtained.The system is a non-contact measuring method with simplicity and feasibility,which does not damage the measurement target and destroy the natural state of measured objects.Test and error analysis results show that the developed system is of high measurement accuracy,and that it is a reliable and convenient measuring method.

Impact of Lingding Navigation Channel on Fresh Salt-Water Mixing in Dry Season

HE Wei ZHU Liang-sheng HU Jin-peng

2017, 45(4):  138-144.  doi:10.3969/j.issn.1000-565X.2017.04.020

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Lindingyang bay is a typical complex tide-dominated estuary.In dry season,fresh salt-water mixing presents obvious temporal and spatial variations and cannot be regarded as a single partial mixing type.In addition,the dredged channel may affect hydrodynamics and material transportation.In order to reveal the dynamic change and fresh-salt-water mixing characteristics of Linding navigation channel before and after the third-stage engineering,a dynamical geomorphology analysis is conducted,and the mechanism decomposition method as well as the three-dimension mathematical model is adopted.The results shows that ( 1) Lingding channel can be divided into three parts,namely upper,middle and lower sectors,and the dynamic characteristics as well as the fresh salt-water mixing mechanism varies in different sectors; ( 2) after engineering,the shelf water intrusion from the bottom into Lingdingyang bay becomes obvious; ( 3) with the increase of the velocity caused by flood tide and ebb tide,the vertical circulation of the channel becomes strong.The surface velocity increases more significantly than that of the bottom; and ( 4) after engineering,the stratification and circulation coefficients both increase,and the fresh saltwater mixing effect is enhanced.