The sand dunes are typical bed forms of natural alluvial rivers. In this article, a vertical 2-D Reynolds stress model is established for the simulation of turbulent flows around sand dunes, and water-sand boundary co...The sand dunes are typical bed forms of natural alluvial rivers. In this article, a vertical 2-D Reynolds stress model is established for the simulation of turbulent flows around sand dunes, and water-sand boundary conditions are set with particular attention. By numerical simulations, the following conclusions can be drawn. （1） The flow resistance in rivers with sand dunes could be divided into the sand-grain resistance and the sand dune resistance, and the sand-grain resistance coefficient mainly depends on Reynolds number, relative sand grain roughness and sand dune steepness. This coefficient in rivers with sand dunes would be larger than that calculated in a flat riverbed, and the steeper the sand dunes, the larger the sand-grain resistance coefficient. （2） The sand dune resistance coefficient mainly depends on the relative sand dune height and sand dune steepness, the steeper the sand dunes, the larger the sand dune resistance coefficient. （3） For the flat riverbed, the turbulent eddy viscosity coefficient and the sediment diffusion coefficient are approximately identical, but for the sand dune riverbed, in the vertical position, where the sediment diffusion coefficient reaches its maximum, it would be higher than the turbulent eddy viscosity coefficient.展开更多
Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing sheafing motion and up...Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing sheafing motion and upstream anisotropy of the turbulence flow would have significant effect on the turbulent structures, and hence the memory effect should be taken into consideration. Furthermore, the 2-D mathematical model was employed to simulate the unsteady flow around the Taiping Sand Bar in the lower reach of the Yangtze River and the time step effect on the unsteady flow simulation with the implicit scheme was discussed at the same time. The results show that the implicit scheme keeps effective until the time step reaches a certain number, and the calculated water levels and velocities are in agreement with the observed data.展开更多
Atomized flow is an unnatural two-phase flow produced while water discharges in water release structures. This flow might threaten the normal operation of hydraulic and hydroelectric installations owing to the unnatur...Atomized flow is an unnatural two-phase flow produced while water discharges in water release structures. This flow might threaten the normal operation of hydraulic and hydroelectric installations owing to the unnatural and high-density rain as well as the unnatural and dirty mist. The splash region, the region with the highest rain intensity, hence should receive much attention during the design and operation of the hydraulic and hydroelectric installations. In this paper rain intensity distribution in the splash region of the atomized flow is investigated experimentally, and the method of random simulation is used to predict the rain intensity distribution in the splash region.展开更多
The near field stahility and mixing characteristics of buoyant jets produced by thermal diffuse in quiescent shallow water are inw.stigated numerically to predict under what combinations of discharge and ambient chara...The near field stahility and mixing characteristics of buoyant jets produced by thermal diffuse in quiescent shallow water are inw.stigated numerically to predict under what combinations of discharge and ambient characteristics the near field will be stable or unstable, Analyses for different discharging types show that the discharge stability is purely dependent on the near-field hehavior of the jets, or the dynam ic interaction of the buoyant jet region, the surface impinge ment region and the internal hydraulic jump region, and is independent of the far-field geometry of the receiving water. The stability criterion is a function of the relative submerged depth, and source densimetrie Froude number.展开更多
This article studies the atomization rainfall and the generated flow on a slope by numerical simulations.The atomization rainfall is simulated by a unified model for splash droplets and a suspended mist,and the distri...This article studies the atomization rainfall and the generated flow on a slope by numerical simulations.The atomization rainfall is simulated by a unified model for splash droplets and a suspended mist,and the distribution of the diameter of splash rain drops is analyzed.The slope runoff generated by the atomization rainfall is simulated by a depth-averaged 2-D model,and the localization of the rainfall intensity in space is specially considered.The simulation results show that：（1） the median rain size of the atomization rainfall increases in the longitudinal direction at first,then monotonously decreases,and the maximum value is taken at the longitudinal position not in consistent with the position where the maximum rain intensity is taken.In the lateral direction the median rain size monotonously decreases,（2） since the atomization rainfall is distributed in a strongly localized area,it takes a longer time for its runoff yield to reach a steady state than that in the natural rainfall,the variation ranges of the water depth and the velocity in the longitudinal and lateral directions are larger than those in the natural rainfall.展开更多
Slit type bucket is one kind of flip bucket for energy dissipation generally used in the hydraulic project. In this paper the atomized flow produced behind this energy dis sipator is analyzed, a numerical model for th...Slit type bucket is one kind of flip bucket for energy dissipation generally used in the hydraulic project. In this paper the atomized flow produced behind this energy dis sipator is analyzed, a numerical model for the aerated jet con sidering air entrainment and air resistance force is suggested, and simulation of the rain resulted by the atomized flow is also discussed. Furthermore, the prototype observation data for the atomized flow of Dongjiang Hydropower Station is used to verify the model suggested.展开更多
基金support by the National Natural Science Foundation of China (Grant No.50539060)
文摘The sand dunes are typical bed forms of natural alluvial rivers. In this article, a vertical 2-D Reynolds stress model is established for the simulation of turbulent flows around sand dunes, and water-sand boundary conditions are set with particular attention. By numerical simulations, the following conclusions can be drawn. （1） The flow resistance in rivers with sand dunes could be divided into the sand-grain resistance and the sand dune resistance, and the sand-grain resistance coefficient mainly depends on Reynolds number, relative sand grain roughness and sand dune steepness. This coefficient in rivers with sand dunes would be larger than that calculated in a flat riverbed, and the steeper the sand dunes, the larger the sand-grain resistance coefficient. （2） The sand dune resistance coefficient mainly depends on the relative sand dune height and sand dune steepness, the steeper the sand dunes, the larger the sand dune resistance coefficient. （3） For the flat riverbed, the turbulent eddy viscosity coefficient and the sediment diffusion coefficient are approximately identical, but for the sand dune riverbed, in the vertical position, where the sediment diffusion coefficient reaches its maximum, it would be higher than the turbulent eddy viscosity coefficient.
基金Project supported by the National Natural Science Foundation of China(Grant No.50539060).
文摘Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing sheafing motion and upstream anisotropy of the turbulence flow would have significant effect on the turbulent structures, and hence the memory effect should be taken into consideration. Furthermore, the 2-D mathematical model was employed to simulate the unsteady flow around the Taiping Sand Bar in the lower reach of the Yangtze River and the time step effect on the unsteady flow simulation with the implicit scheme was discussed at the same time. The results show that the implicit scheme keeps effective until the time step reaches a certain number, and the calculated water levels and velocities are in agreement with the observed data.
基金Project Supported by the National Nature Science Foundation of China (Grant Nos: 50279033, 50539060)
文摘Atomized flow is an unnatural two-phase flow produced while water discharges in water release structures. This flow might threaten the normal operation of hydraulic and hydroelectric installations owing to the unnatural and high-density rain as well as the unnatural and dirty mist. The splash region, the region with the highest rain intensity, hence should receive much attention during the design and operation of the hydraulic and hydroelectric installations. In this paper rain intensity distribution in the splash region of the atomized flow is investigated experimentally, and the method of random simulation is used to predict the rain intensity distribution in the splash region.
文摘The near field stahility and mixing characteristics of buoyant jets produced by thermal diffuse in quiescent shallow water are inw.stigated numerically to predict under what combinations of discharge and ambient characteristics the near field will be stable or unstable, Analyses for different discharging types show that the discharge stability is purely dependent on the near-field hehavior of the jets, or the dynam ic interaction of the buoyant jet region, the surface impinge ment region and the internal hydraulic jump region, and is independent of the far-field geometry of the receiving water. The stability criterion is a function of the relative submerged depth, and source densimetrie Froude number.
基金Project supported by the Ministry of Water Resources special funds for Scientific Research on Public Causes (Grant No.201101005)
文摘This article studies the atomization rainfall and the generated flow on a slope by numerical simulations.The atomization rainfall is simulated by a unified model for splash droplets and a suspended mist,and the distribution of the diameter of splash rain drops is analyzed.The slope runoff generated by the atomization rainfall is simulated by a depth-averaged 2-D model,and the localization of the rainfall intensity in space is specially considered.The simulation results show that：（1） the median rain size of the atomization rainfall increases in the longitudinal direction at first,then monotonously decreases,and the maximum value is taken at the longitudinal position not in consistent with the position where the maximum rain intensity is taken.In the lateral direction the median rain size monotonously decreases,（2） since the atomization rainfall is distributed in a strongly localized area,it takes a longer time for its runoff yield to reach a steady state than that in the natural rainfall,the variation ranges of the water depth and the velocity in the longitudinal and lateral directions are larger than those in the natural rainfall.
文摘Slit type bucket is one kind of flip bucket for energy dissipation generally used in the hydraulic project. In this paper the atomized flow produced behind this energy dis sipator is analyzed, a numerical model for the aerated jet con sidering air entrainment and air resistance force is suggested, and simulation of the rain resulted by the atomized flow is also discussed. Furthermore, the prototype observation data for the atomized flow of Dongjiang Hydropower Station is used to verify the model suggested.
