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NUMERICAL MODELING OF COMPOUND CHANNEL FLOWS

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Journal of Hydrodynamics 2002年第4期14卷 106-109页

作者： Wang De-guan, Cheng Li college of Water Resources and environmental engineering, hohai university, nanjing 210098, china college of Water Resources and environmental engineering Hohai University Nanjing 210098 China

A numerical model capable of predicting flow characteristics in a compound channel was established with the 3-D steady continuity and momentum equations along with the transport equations for turbulence kinetic energy and dissipation rate. Closure was achieved with the aid of algebraic relations for turbulent shear stresses. The above equations were discretized with implicit difference approach and solved with a step method along the flow direction. The computational results showing the lateral distribution of vertical average velocities and the latio of total flow in the compound channel agree well with the available experimental data.

关键词： compound channel flow discharge ratio of channel and floodplain turbulence

Application analysis of empirical mode decomposition and phase space reconstruction in dam time-varying characteristic

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Science china(Technological Sciences) 2010年第6期53卷 1711-1716页

作者： ZHANG ZhiJun1,2,3,GU ChongShi1,2,BAO TengFei1,2,ZHANG Lan1,2 & YU Hong1,2 1 State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering,hohai university,nanjing 210098,china 2 National engineering Research Center of Water Resources Efficient Utilization and engineering Safety,hohai university,nanjing 210098,china 3 Department of Civil,environmental and Geomatic engineering,Swiss Federal Institute of Technology,Zurich 8093,Switzerland 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Nanjing 210098 China3. Department of Civil Environmental and Geomatic Engineering Swiss Federal Institute of Technology Zurich 8093 Switzerland

In view of some courses of the time-varying characteristics processing in the analysis of dam deformation,the paper proposes a new method to analyze the dam time-varying characteristic based on the empirical mode decomposition and phase space reconstruction *** of all,to reduce the influences on the traditional statistical model from human factors and assure the analysis accuracy,response variables of the time-varying characteristic are obtained by the way of the empirical mode decomposition;and then,a phase plane of those variables is reconstructed to investigate their processing *** methods have already been applied to an actual project and the results showed that data interpretation with the assists of empirical mode decomposition and phase space reconstruction is effective in analyzing the perturbations of response variables,explicit in reflecting the entire development process,and valid for obtaining the evolution rules of the time-varying *** methodology is a powerful technical support for people to further master the rules of dam operation.

关键词： dam safety monitoring dam time-varying characteristic empirical mode decomposition phase space reconstruction

FINE SILT PARTICLE PATHLINE OF DREDGING SEDIMENT IN THE YANGTZE RIVER DEEPWATER NAVIGATION CHANNEL BASED ON EFDC MODEL

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Journal of Hydrodynamics 2010年第6期22卷 760-772页

作者： XIE Rui WU De-an YAN Yi-xin ZHOU Hai college of Harbor Coastal and Offshore Engineering Hohai University Nanjing 210098 China Shanghai Institute of Waterways Shanghai 200120 China

Based on the environmental Fluid Dynamics Code （EFDC）, a three-dimensional baroclinic model for lower reaches of the Yangtze River, Yangtze River Estuary, Hangzhou Bay and the adjacent sea areas was established with the sigma-coordinate in the vertical direction and the orthogonal curvilinear coordinates in the horizontal direction. The fine silt particle tracers were injected during different tides with the calibrated three-dimensional numerical model in the Yangtze River Estuary to simulate the migration tracks of the tracers in the following three days, and thereby study the migration behavior of the fine silt particles of dredged sediment after dumping at different locations in the navigation channel in the Yangtze River Estuary. The study shows that the particle paths of the tracer particles basically migrate to the open sea along the middle axis of river course in the form of reciprocating oscillation, the migration and diffusion directions of tracer particles are basically parallel to the navigation channel in guide levee, similar to long belt distribution, and the tracer particles migrate to the southeast out of the guide levee. The particle which is on the southern and northern sides enter groin and cross the navigation channel in the process of movement, and is easy to deposit in the navigation channel. The migration tracks of the particles released at different layers are basically similar at the same release station, but specifically different, varying at different cross sections. The result can be used for the choice and evaluation of dredging schemes in the Yangtze River Deepwater Navigation Channel.

关键词： deepwater channel EFDC model tracer fine silt particles

EXPERIMENTS OF THREE-DIMENSIONAL FLOW STRUCTURE IN BRAIDED RIVERS

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Journal of Hydrodynamics 2009年第2期21卷 228-237页

作者： HUA Zu-lin GU Li CHU Ke-jian Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education College of Environmental Science and Engineering Hohai University Nanjing 210098 China State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing210098 China

The braided river is a typical river pattern in nature, but there is a paucity of comprehensive data set describing the three-dimensional flow field in the braided river. A physical model experiment was used to study the flow characteristics in the typical braided river with a mid-bar between two anabranches. In the experiment, two kinds of mid-bar with the ratios of its length to maximal width of 3 and 5 were considered. Moreover, the mid-bar could be moved to adjust the width of two anabranches. The detailed measurements of velocity were conducted using an acoustic Doppler velocimeter over a grid defined throughout the whole braided river region, including the bifurcation, two anabranches and the confluence. In two kinds of mid-bar braided models, a separation zone was observed in the anabranch of the model in which the ratio of length to maximal width of mid-bar is 3, however the separation zone was not found in another model in which the ratio is 5. In addition, the opposite secondary cells were observed at the bend apex of anabranch in two models, and different longitudinal velocity distributions in the entrance region of anabranch account for this opposite flow structure. Finally, turbulent kinetic energy were shown and compared in different situations. The high turbulence occurs at the place with strong shear, especially at the boundary of the separation zone and the high velocity passing flow.

关键词： braided river three-dimensional flow structure secondary flow turbulent kinetic energy

FINITE ELEMENT NUMERICAL SIMULATION OF LAND SUBSIDENCE AND GROUNDWATER EXPLOITATION BASED ON VISCO-ELASTICPLASTIC BIOT'S CONSOLIDATION THEORY

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Journal of Hydrodynamics 2011年第5期23卷 615-624页

作者： LUO Zu-jiang ZENG Feng college of Earth Science and engineering Hohai University Nanjing 210098 China

The land subsidence due to groundwater exploitation has an obvious hysteretic nature with respect to the decrease of the under groundwater level, and the uneven settlement often causes ground fissures. To study these important features, a visco-elasticplastic constitutive relationship with consideration of the coupling of seepage and soil deformation is proposed, and a finite element model with variable coefficients based on the Biot＇s consolidation theory is built. With the groundwater exploitation and the land subsidence control in Cangzhou City, Hebei Province as an example, the variations of the under groundwater level and the deve- lopment of the land subsidence due to the groundwater exploitation are simulated and ground fissures are predicted by the horizontal displacement calculation. The results show that the lag time between the land subsidence and the under groundwater level descent is about a month, and the simulated results of fissures agree well with the observed data. The model can well reveal the characterization of the interaction between the land subsidence and the groundwater exploitation.

关键词： hysteretic property land subsidence visco-elastic-plastic constitutive relationship finite element model

EXPERIMENT OF IMPACT OF RIVER HYDRAULIC CHARACTERISTICS ON NUTRIENTS PURIFICATION COEFFICIENT

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Journal of Hydrodynamics 2007年第3期19卷 387-393页

作者： WANG Pei-fang WANG Xiao-rong WANG Chao State Key Laboratory of Pollution Control and Resource Reuse School of Environment Nanjing University Nanjing 210093 China State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing 210098 China Key Laboratory of Intergrated Regulation and Resource Development on Shallow Lakes College of Environmental Science and Engineering Hohai University Nanjing 210098 China

Hydraulic characteristics of a river are the key factors for river water quality improvement and river restoration. A simulated river was exploited to study the interactions between water contaminant purification coefficients and the characteristics of the river, such as the cross-section velocity, water depth, Reynolds number, and Froude number. To enhance the purification capacity of the river, detritus with 5 mm to 10 mm in diameter and contact surface area per volume of 87.6 m^2/m^3 were constructed naturally at the bed and along one side of the bank to form half shape of the river cross-section. During the one-month experiment （including 3 periods） from the third of November to the fourth of December, 2005, three categories of hydraulic conditions were investigated. Results show that the purification coefficient （K） of Total Nitrogen （TN） is closely coherent with the hydraulic retention time （T）, river length （L）, Reynolds number （Re） and Froude number （Fr）. The relationship of K and T generally agrees with the power law under the three experimental water hydraulic conditions. Based on these results, the optimal Re and Fr ranges can be obtain to serve as a guideline for ecological re-engineering design to improve river water quality and restore river ecosystem.

关键词： Hydraulic characteristics total nitrogen,purification coefficient interaction simulated river

Coupling analysis of unsteady seepage and stress fields in discrete fractures network of rock mass in dam foundation

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Science china(Technological Sciences) 2011年第S1期54卷 133-139页

作者： CHAI JunRui 1,2 & XU WeiSheng 2 1 college of Hydraulic and environmental engineering,china Three Gorges university,Yichang 443002,china 2.college of Hydropower engineering,Xi’an university of Technology,Xi’an 710048,china 1. college of Hydraulic and environmental engineering China Three Gorges University Yichang 443002 China2. College of Hydropower Engineering Xi’an University of Technology Xi’an 710048 China

The drag force of water flow through single fracture and the coupling characteristics of seepage and stress in single fracture surface are analyzed,and a three dimensional model of coupled unsteady seepage and stress fields is *** model is used to the analysis of foundation rock mass of a high *** the coupling effects are considered,the changes of boundary heads have less influence on the inner head of rock mass,and the strong permeability of main fractures *** the coupling effects are not considered,the fractures distribution affects the inner head more *** the upstream water head declines,the inner head of dam foundation slightly declines and the hydraulic gradient distribution becomes smoother.A bigger upstream water level declining velocity has a stronger lag effect,meanwhile the values of stress components change more *** the upstream water level declining velocity directly affects the stability of rock mass in dam foundation and we should take into account the above factors to make sure the safety of the dam during reservoir level fluctuation period.

关键词： hydraulic engineering unsteady seepage stress coupling fractures network rock mass

ANALYSIS OF WATER QUALITY IN SHALLOW LAKES WITH A TWO-DIMENSIONAL FLOW-SEDIMENT MODEL

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Journal of Hydrodynamics 2007年第4期19卷 501-508页

作者： JI Yong ZhANG Jie YAO ei ZHAO Di-hua Nanchang Institute of Technology Nanchang 330099 China college of environmental Science and engineering Hohai University Nanjing 210098 China nanjing Hydraulic Research Institute Nanjing 210098 China

The governing equation for sediment pollutions was derived based on the turbulent diffusion of pollutants in shallow lakes. Coupled with shallow water equations, a depth-averaged 2-D flow and water quality model was developed. By means of the conservation law, a proposed differential equation for the change of sediment pollutants was linked to the 2-D equations. Under the framework of the finite volume method, the Osher approximate Riemann solver was employed to solve the equations. An analytical resolution was used to examine the model capabilities. Simulated results matched the exact solutions especially well. As an example, the simulation of CODMn in the Wuli Lake, a part of the Taihu lake, was conducted, which led to reasonable results. This study provides a new approach and a practical tool for the simulation of flow and water quality in shallow lakes.

关键词： sediment falling velocity turbulence flow and water quality model finite volume method approximate Riemann solver shallow water equation advection-dispersion equation

EFFECTS OF ENTRAINED AIR MANNER ON CAVITATION DAMAGE

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Journal of Hydrodynamics 2011年第3期23卷 333-338页

作者： WU Jian-hua LUO Chao college of Water Conservancy and Hydropwer engineering Hohai University Nanjing 210098 China

Early in 1953 the experiments by Peterka proved that air entrainment has effects on decreasing cavitation damage. This technology has been widely used in the release works of high dams since the inception of air entrainment in the Grand Goulee Dam in 1960. Behavior, mechanism and application of air entrainment for cavitation damage control have been investigated for over half century. However, severe cavitation damage happened due to complex mechanism of air entrainment. The effects of air entrainment are related to many factors, including geometric parameters, hydraulic parameters and entrained air manners. In the present work an experimental set-up for air entrainment was specially designed, the behavior of reducing cavitation damage was experimentally investigated in the three aspects of entrained air pressure, air tube aera and air tube number. The results show that magnitude of reduction of cavitation damage is closely related to the entrained air tube number as well as entrained air pressure, air tube aera, and that the effect through three air tubes is larger than that through single air tube although the entrained air tubes have the same sum of tube aera, that is, 1 ＋ 1 ＋ 1 〉 3. Therefore, it is important to design an effective manner of air entrainment.

关键词： air entrainment air pressure air tube area cavitation damage entrained air manner