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Characteristics of snow cover distribution along railway subgrade and the protective effect of snow fences

Journal of Arid Land 2023年第8期15卷 901-919页

作者： LEI Jia CHENG Jianjun GAO Li MA Benteng AN Yuanfeng DONG Hongguang college of water conservancy&Architectural engineering Shihezi UniversityShihezi 832003China

Railways built in cold,snowy,and lightly populated areas are subjected to wind and snow *** this study,we selected a snow hazard prevention and control section of the Altay–Zhundong Railway in Xinjiang Uygur Autonomous Region of China as the research *** investigated the deposited snowfall variation characteristics on the two sides and in the embankment pavement area of snow fences with different porosities,fence heights,and arrangement distances using single-factor tests and orthogonal tests based on global atmospheric reanalysis climate data,field survey data,and a multi-phase flow analysis *** results showed significant differences in the characteristics of snow cover distribution and snow cover thickness between the embankment and the cutting in the absence of snow protection *** maximum snow cover thickness of the embankment pavement decreased by 12.6%relative to the cutting *** snow cover thickness of the embankment exhibited an increasing trend from windward shoulder to leeward shoulder,whereas the snow cover thickness of the cutting presented a declining trend from windward shoulder to leeward *** the collaborative prevention and control of snow fences and embankments,the three factors can be ranked in terms of their sensitivity to deposited snowfall within the influence scope of snow fences as follows:fence height>arrangement distance>*** the same time,fence height yielded a significant relationship for the influence scope of snow fences(Pfence height>arrangement *** the embankment protection of the Altay–Zhundong Railway against wind and snow,snow fence with a porosity of 75%,a fence height of 4.8 m,and an arrangement distance from the embankment of 60 m produced the best snow control *** revealing the characteristics of snow cover distribution along railway subg

关键词： snowdrift numerical simulation orthogonal test porosity fence height arrangement distance Altay-Zhundong Railway

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Numerical Study of Submerged Vertical Plane Jets Under Progressive water Surface Waves

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China Ocean engineering 2005年第3期19卷 433-442页

作者：戴会超王玲玲 college of water conservancy and Hydro-Power engineering Hohai University Nanjing 210098 China

When wastewater is discharged into a coastal area through an ouffall system, it will always be subjected to the action of waves. It is important to study and quantify the mixing of the discharge with the ambient water so that accurate environmental impact assessment can be made for such discharge conditions. The present work aims to study the phenomenon of a plane jet discharged into water environment with regular waves. A 3D numerical model based on the full Navier- Stokes equations （NSE） in the a-coordinate is developed to study the present problem. Turbulence effects are modeled by a subgrid-scale （SGS） model using the concept of large eddy simulation （LES）. The operator splitting method is used to solve the modified NSE. The model has been applied to the simulation of three different eases of submerged plane jets with surface waves： jet with strong waves, jet with weak waves and jet without waves. Numerical results show that the waves enhance the mixing of the jet with the ambient fluid, and cause a periodic deflection of the jet. The size of the recirculation is about 1.5- 2.4 h （water depth） . The velocity profile of the jet is serf-similar in the zone of established flow for both the pure jet and jet in wave circumstances. The spreading characteristic constant a is 0. 100 and 0. 105 for pure momentum jets with Re numbers 1025 and 2050. The value of a increases from 0. 130 to 0. 147 for a jet in weak and strong wave circumstances, showing that waves have an obvious effect on the mixing and dilution properties of jets. Numerical results are in good agreement with the experimental data for the cases of pure jets and jets with waves.

关键词： momentum jet large eddy simulation regular wave

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Flow choking characteristics of slit-type energy dissipaters

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Journal of Hydrodynamics 2015年第1期27卷 159-162页

作者：吴建华万彬马飞李同春 National engineering Research Center of water Resources Efficient Utilization and engineering Safety College of Water Conservancy and Hydropower Engineering Hohai University

In this paper, the behavior of the flow choking, including the critical and developing states, was experimentally investiga- ted by means of five slit-type outlets, characterized by the outlet width, the contraction angle and the opening of the working gate. The results showed that the approach flow Froude number of the critical choking decreases if the outlet width increases, or the con- traction angle decreases, or the opening increases. There is the hysteresis when the flow choking develops, i.e., the Froude numbers of the appearance and disappearance of the flow choking at the increasing discharge regime are all larger than those at the decreasing discharge regime. For various widths of the outlets, the differences between the critical Froude numbers at small opening are much larger than thoset at large opening. The change range from appearance to disappearance of the flow choking at small opening is smaller than that at large opening.

关键词： flow choking slit-type energy dissipater partial opening Froude number

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Numerical Modeling of Elastic Modulus for Cement Paste Using Homogenization Method

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Journal of Wuhan University of Technology(Materials Science) 2013年第4期28卷 751-760页

作者：田正宏 BIAN Ce State Key Laboratory of Hydrology-water Resources and Hydraulic engineering of Hohai University college of water conservancy and Hydropower engineering Hohai University

This paper focused on the evolution over time of elasticity of the cement paste during the hydration, e g, Young＇s modulus and Poisson＇s ration, by the proposed homogenization method combined the percolation algorithm with individual phase intrinsic elasticity. A cement paste development model, named CEMHYD3D, was used to establish an accurate microstructure. The modelling results are in good agreement with the experimental data and other numerical results available in the open literatm＇e. The suitable homogeneous scheme, applied to each level, should be carefully chosen to result in a realistic prediction. The percolation concept should aims to correctly predict the elasticity for cement paste at very early age, especially under low w/c ratios.

关键词： :ement paste elastic modulus numerical modeling percolation

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Analysis of dipole noise level characteristics of NACA0015 hydrofoil under different working conditions

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Journal of Hydrodynamics 2021年第1期33卷 63-73页

作者： An Yu Yi-fu Wang Qing-hong Tang Da-qing Zhou college of Energy and Electrical engineering Hohai UniversityNanjing 210098China college of water conservancy and Hydropower engineering Hohai UniversityNanjing 210098China

In this paper,the flow field around NACA0015 hydrofoil is calculated under the condition of two-phase cavitating flow to provide a theoretical guidance for reducing the cavitation noise.A modified turbulence model coupled with the Zwart cavitation model is used to calculate the flow *** to the computed sound source data,the dipole sound pressure distribution diagrams for the extremely short time and the complete time around the hydrofoil under different working conditions are *** sound pressure distribution and the sound pressure amplitude are analyzed in *** addition,the field points around the hydrofoil are selected to generate the corresponding frequency response function curves,which are analyzed from the aspects of the trend,the variation and the extreme *** results show that the dipole characteristics are gradually diminished and finally disappear with the increase of the *** the frequency of the vapor volume fraction fluctuation,the noise level at the field point will have an extreme value.

关键词： Cavitating flow dipole noise sound field distribution frequency response

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Effect of air bubble size on cavitation erosion reduction

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Science China(Technological Sciences) 2017年第4期60卷 523-528页

作者： WU JianHua SU KunPeng WANG Yu GOU WenJuan college of water conservancy and Hydropower engineering Hohai University State Key Laboratory of Hydraulic engineering Simulation and Safety Tianjin University

Over the past 60 years, the air concentration in water has been considered as a control index of cavitation erosion reduction and widely used in the designs of hydraulic structures. However, the mechanism of air entrainment against cavitation erosion has been paid good attention to. In the present work, the effect of air bubble size on cavitation erosion reduction was experimentally investigated. A device with micron-scale orifice diameters(10, 20 and 50 μm in size) was specially designed to introduce air bubbles into water. The experiments about the effect of air bubble size were conducted by means of a vibratory apparatus, including the behavior of formation and movement for single air bubble, the characteristics of cavitation erosion reduction at different air entrainment conditions. The findings demonstrate that high air concentration has significant effects on cavitation erosion ***, a notable problem was that the size of air bubbles is of outstanding effect on cavitation erosion reduction. Small air bubbles support to alleviate cavitation erosion, even at same air concentration.

关键词： air bubble size air entrainment cavitation erosion micron-scale

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On the correction of the boundary deficiency in SPH for the frictional contact simulation

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Science China(Technological Sciences) 2014年第1期57卷 86-100页

作者： WANG Jian HUA Hui GU ChongShi National engineering Research Center of water Resources Efficient Utilization and engineering Safety Hohai University college of water conservancy and Hydropower engineering Hohai University

Smoothed particle hydrodynamics(SPH)is a mesh-free method which is powerful for large deformation computation of ***,the algorithm for the simulation of frictional contact which is common in geotechnical engineering is still quite immature due to the boundary *** this study,the cause of boundary deficiency in the SPH simulation for frictional contact is ***,based on mathematical derivation,the method to correct boundary deficiency related to frictional contact is discussed theoretically,where the frictional contact algorithm is established by dividing the computational domain into several subdomains according to the existing contact boundaries and by using contact forces as bridges of these subdomains to fulfil problem solving,and the value of correction coefficient is obtained by comparing the SPH outcome of the contact particles with that calculated through Newton’s second law of *** the same time,from the perspective of numerical computation,an optimized value for the correction coefficient is proposed,and a thorough investigation is performed on the cubic spline kernel function and quintic spline kernel function,whose correction coefficients are found to be 2.0 and[2.0,2.16],***,numerical tests are carried out to verify the proposed *** outcome of the study is helpful to providing theoretical support for the research of frictional contact simulation within the framework of SPH.

关键词： smoothed particle hydrodynamics (SPH) frictional contact boundary deficiency correction

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Fatigue Property of Basalt Fiber-Modified Asphalt Mixture under Complicated Environment

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Journal of Wuhan University of Technology(Materials Science) 2014年第5期29卷 996-1004页

作者：郑元勋 CAI Yingchun ZHANG Guanghai FANG Hongyuan college of water conservancy and Environment Zhengzhou University The Faculty of Infrastructure engineering Dalian University of Technology

The fatigue property of asphalt mixtures under complicated environment （low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect） and the improvement effect for relevant property of basalt fiber-reinforcing asphalt mixture under complicated environment are studied. Two grading types of asphalt mixtures, AC-16I and AC-13I, are chosen, whose optimum asphalt-aggregate ratio and optimum dosage of basalt fiber are determined by the Marshall test. The standard specimens are made firstly, and then the low temperature bending tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under the coupling effect of the chloride erosion and freezing-thawing cycle have been carried out. Finally, the fatigue property tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under complex environment are performed on MTS material testing system. The results indicate that the tensile strength, the maximum curving tensile stress, the curving stiffness modulus, and fatigue properties of asphalt mixture are influenced by the coupling effect of the chloride erosion and freezing-thawing cycle. The low-temperature bending performance and fatigue property of asphalt mixtures under complicated environment can be greatly improved by adding moderate basalt fiber. The dense gradation asphalt mixture possesses stronger ability to resist adverse environmental effects under the same condition.

关键词： asphalt mixture basalt fiber the chloride erosion freezing-thawing cycle the coupling effect low-temperature performance fatigue property

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Large eddy simulation of vertical turbulent jets under JONSWAP waves

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Acta Mechanica Sinica 2011年第2期27卷 189-199页

作者： Jun Lu Ling-Ling Wang Hong-Wu Tang Hui-Chao Dai college of water conservancy and Hydro-power engineering Hohai University 210098 Nanjing China Binhu water Resource Bureaus 214011 Wuxi China

The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier–Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.

关键词： Large eddy simulation Dynamic coherent eddy model σ-coordinate Turbulent jet JONSWAP wave

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FORECAST OF water TEMPERATURE IN RESERVOIR BASED ON ANALYTICAL SOLUTION

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Journal of Hydrodynamics 2008年第4期20卷 507-513页

作者： JI Shun-wen ZHU Yue-ming QIANG Sheng ZENG Deng-feng college of water conservancy and Hydroelectric engineering Hohai University Nanjing 210098 China water Power Plant of Sanhe Shangyoujiang Ganzhou 341212 China

The water temperature in reservoirs is difficult to be predicted by numerical simulations. In this article, a statistical model of forecasting the water temperature was proposed. In this model, the 3-D thermal conduction-diffusion equations were converted into a system consisting of 2-D equations with the Fourier expansion and some hypotheses. Then the statistical model of forecasting the water temperature was developed based on the analytical solution to the 2-D thermal equations. The~ simplified statistical model can elucidate the main physical mechanism of the temperature variation much more clearly than the numerical simulation with the Navier-Stokes equations. Finally, with the presented statistical model, the distribution of water temperature in the Shangyoujiang reservoir was determined.

关键词： water temperature quasi 3-D statistical model thermal conduction-diffusion equation analytical solution regression analysis factor of radiation

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