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A SPLIT-CHARACTERISTIC FINITE ELEMENT MODEL FOR 1-D UNSTEADY FLOWS

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Journal of Hydrodynamics 2007年第1期19卷 54-61页

作者： ZHOU Yi-lin TANG Hong-wu LIU Xiao-hua State Key Laboratory of Hydrology-water Resources and Hydraulic engineering College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China.

An efficient and accurate solution algorithm was proposed for 1-D unsteady flow problems widely existing in hydraulic engineering. Based on the split-characteristic finite element method, the numerical model with the Saint-Venant equations of 1-D unsteady flows was established. The assembled f＇mite element equations were solved with the tri-diagonal matrix algorithm. In the semi-implicit and explicit scheme, the critical time step of the method was dependent on the space step and flow velocity, not on the wave celerity. The method was used to eliminate the restriction due to the wave celerity for the computational analysis of unsteady open-channel flows. The model was verified by the experimental data and theoretical solution and also applied to the simulation of the flow in practical river networks. It shows that the numerical method has high efficiency and accuracy and can be used to simulate 1-D steady flows, and unsteady flows with shock waves or flood waves. Compared with other numerical methods, the algorithm of this method is simpler with higher accuracy, less dissipation, higher computation efficiency and less computer storage.

关键词： split characteristic finite element method,tri-diagonal matrix algorithm 1-D unsteady flow flood wave,river networks

Fluid-structure interaction in Z-shaped pipe with different supports

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Acta Mechanica Sinica 2020年第2期36卷 513-523页

作者： Q.Guo J.X.Zhou X.L.Guan college of water conservancy and Hydropower engineering Hohai UniversityNanjing 210098China Highway Science and Technology Research Institute Xinjiang Production and Construction Corpsürümqi 830002China

Fluid-structure interaction(FSI)has a strong relation with layout of fluid delivery *** is liable to cause local ***,FSI analysis is necessary in many cases,especially for flexible pipe *** modeling consists of eight governing equations and then completely solved via the finite volume method(FVM).Friction,Poisson and joint couplings were discussed in detail to reveal the influence of a Z-shaped pipe with different supports and elbows on *** the feasibility of solving FSI by FVM was verified,the different effects of free,fixed and elastic supports on FSI in the commonly used and simplified Z-shaped pipe were further *** indicated that different support stiffness lead to various FSI *** coupling occurs at the elbow and less support is considered,then the pipe has a relatively large amplitude and complex pressure fluctuation.

关键词： Fluid-structure interaction Finite volume method Z-shaped pipe Support stiffness

Transformation among precipitation,surface water,groundwater,and mine water in the Hailiutu River Basin under mining activity

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维普期刊数据库

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Journal of Arid Land 2022年第6期14卷 620-636页

作者： LI Qian MA Long LIU Tingxi college of water conservancy and Civil engineering college Inner Mongolia Agricultural UniversityHohhot 010018China

Coal mining has changed the hydrogeological conditions of river basins,and studying how the relationship among different types of water body has changed under the influence of coal mining is of great significance for understanding the regional hydrological *** analyzed the temporal and spatial distribution of hydrochemical properties and environmental isotopes in the Hailiutu River Basin(HRB),China with a mixed *** results showed that:(1)human activity(e.g.,coal mining and agricultural production)causes considerable changes in the hydrochemical properties of surface water in and around the mining areas,and leads to significant increases in the concentrations of Na^(+)and SO_(4)^(2-);(2)precipitation is the main source of water vapour in the *** transformation between surface water and groundwater in the natural watershed is mainly affected by precipitation;and(3)in the mining areas,the average contribution rates of precipitation to the recharge of surface water and groundwater increased by 2.6%-7.9%and 2.7%-9.9%,*** in the Salawusu Formation constitutes up to 61.3%-72.4%of mine ***,this study is beneficial for quantifying the effects of coal mining on local hydrological *** research results can provide a reference for local water resources management and ecological environment improvement.

关键词： precipitation mine water groundwater surface water transformation mode

Analysis of seismic disaster failure mechanism and dam-break simulation of high arch dam

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Earthquake engineering and engineering Vibration 2014年第2期13卷 327-335页

作者： Zhang Jingkui Zhang Liaojun Anhui and Huaihe River Institute of Hydraulic Research college of water conservancy and Hydropower engineering Hohai University

Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code(3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, infl uence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far fi eld energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice.

关键词： high arch dam complex foundation 3DEC disaster mechanism dam-break process simulation seismic safety evaluation

TIDAL EFFECTS ON GROUNDwater DYNAMICS IN COASTAL AQUI-FER UNDER DIFFERENT BEACH SLOPES

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Journal of Hydrodynamics 2012年第1期24卷 97-106页

作者： LIU Yi SHANG Song-hao MAO Xiao-min college of water conservancy and Civil EngineeringChina Agricultural UniversityBeijing 100083China State Key Laboratory of Hydroscicncc and engineering Department of Hydraulic EngineeringTsinghuaUniversityBeijing 100084China college of water conservancy and Civil engineering China Agricultural UniversityBeijing 100083China

The tide induced groundwater fluctuation and the seawater intrusion have important effects on hydrogeology and ecology of coastal *** previous studies,there were few quantitative evaluations of the joint effects of the beach slope and the tide fluctuation on the groundwater *** this article,a numerical model is built by using the software FEFLOW with consideration of seawater intrusion,tide effects,density dependent flow and beach sloping *** simulation results are validated by laboratory experimental data in *** numerical scenarios are designed in a practical scale with different beach *** show that the groundwater fluctuation decays exponentially with the distance to the beach,i.e.,,and our simulation further shows that the beach slope influence can be expressed in the form of a logarithm *** for the same location,the amplitude increases logarithmically with the beach angle in the form,where and are related with the horizontal distance（）in the form of a logarithm *** beach slope has no influence on the phase lag,although the latter increases regularly with the distance from the *** beach slope effect on the seawater intrusion is investigated through the quantitative relationship among the relative intrusion length（）,the relative enhancement of the tide induced seawater intrusion（）and the beach angle（）.It is shown that the tide effects on a milder beach is much greater than on a vertical one,and both λ and κ can be expressed in logarithm functions *** tidal effect on the flow field in the transition zone for a particular mild beach is also studied,with results showing that the tide induced fluctuation of is similar to the groundwater table fluctuation while shows a distinct variation along both directions.

关键词： tidal effects salt wedges saline intrusion beach slope finite element method

Hydraulics of a multiple slit-type energy dissipater

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Journal of Hydrodynamics 2014年第1期26卷 86-93页

作者：吴建华姚莉马飞吴伟伟 college of water conservancy and Hydropower engineering Hohai University Hydraulic Structures Design Division Hydrochina Huadong Engineering Corporation

With the constructions of high dam projects in China, the energy dissipation downstream of a dam becomes a serious concern. In this study, a multiple slit-type energy dissipater, with different reduction size slits in the outlet, is developed on the basis of conventional slit-type energy dissipaters, aiming to enhance the energy dissipation through the turbulence and the friction between the different layers of the jet flow and the air entrainment due to the increased surface of the flow to the air. The hydraulic characteristics of the energy dissipater are experimentally investigated by means of three sets of physical models in nine cases, to characterize the geometric parameters with suitable performance. The main concerns are the flow regime, the jet flow trajectory, the energy dissipation, the cavitation characteristics, and the flow choking. The results indicate that the dissipater enjoys a high energy dissipation ratio with suitable hydraulic performance comparing with the conventional slit-type energy dissipaters.

关键词： aerator cavity length fin lateral deflector

Decisive influence of the ionization strength of cosmic rays on the cavitation characteristics of pure water

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Science China(Technological Sciences) 2009年第6期52卷 1804-1808页

作者： CHANG JinShi college of water conservancy & Civil engineering,China Agricultural University,Beijing 100083,China college of water conservancy & Civil engineering China Agricultural University Beijing China

The experiment result in this article shows that the initial and critical cavitation pressure of pure water are both increasing along with the increase of height above sea level,and the ionization strength of cosmic rays in the lower aerosphere is the crucial factor which influences the cavitation pressure of pure *** author concludes the relationship between the cavitaion pressure of pure water and the height above sea ***,air particles in water caused by the radiation of cosmic rays can exist in the water for a long time and will not escape.

关键词： initial cavitaiton pressure critical cavitation pressure ionization strength of cosmic rays height above sea level

Improved conservative level set method for free surface flow simulation

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Journal of Hydrodynamics 2014年第2期26卷 316-325页

作者：赵兰浩毛佳刘晓青 BAI Xin WILLIAMS J. J. R. college of water conservancy and Hydropower engineering Hohai University School of engineering and Materials Science Queen Mary University of London

By coupling the standard and the conservative level set methods, an improved conservative level set method is proposed to capture the free surface smoothly with excellent mass conservation properties. The improvement lies in the fact that the surface normal is computed from a signed distance function instead of the Heaviside function. Comparing with the conservative level set method, the inevitable numerical discretization errors to point the surface normal in arbitrary directions could be eliminated, and the instability of the numerical solution could be improved efficiently. The advantage is clear in the straightforward combination of the standard level set and the conservative level set and a little effort is taken in coding compared with other coupled methods. The present method is validated with several well-known benchmark problems, including the 2-D Zalesak＇s disk rotating, the 3-D sphere stretching in deformation vortex and the dam break flow simulation. The results are shown to be in good agreement with the published experimental data and numerical results.

关键词： flee surface flow improved conservative level set mass conservation

Standing wave at dropshaft inlets

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Journal of Hydrodynamics 2017年第3期29卷 524-527页

作者：吴建华任炜辰马飞 college of water conservancy and Hydropower engineering Hohai UniversityNanjing 210098China

Standing waves occur frequently at the inlet due to the change of the flow direction from an approach channel to the *** performance of the standing wave,characterized by the relative height,the location and the extent,is theoretically and experimentally investigated in the present *** is shown that the height of the standing wave decreases with the increases of the approach flow Froude number and the sub-channel number in the inlet,but increases with the increase of the curvature of the *** errors of the expressions for the relative height,the location and the extent of the standing wave,are 9.7%,7.8%and 13.1%,respectively,as compared with the experimental data.

关键词： Dropshaft height location extent standing wave