This paper presents an experimental study of the overtopping breach of homogeneous non-cohesive levee or dike in a 180°bend rectangular flume. Detailed experimental and numerical results provide information on th...This paper presents an experimental study of the overtopping breach of homogeneous non-cohesive levee or dike in a 180°bend rectangular flume. Detailed experimental and numerical results provide information on the breach flow discharge and longitudi- nal and transversal breach profiles for this type of levee. It is indicated that the water level and the flow discharge in the river and the levee material properties are significant influencing factors for the breach evolution. The plane form of the breach is approximately an asymmetrical hyperbola. A formula with a non-constant flow factor is proposed to compute this kind of breach discharge.展开更多
The subject of present study is the application of mesh free Lagrangian two-dimensional non-cohesive sediment transport model applied to a two-phase flow over an initially trapezoidal-shaped sediment embankment. The g...The subject of present study is the application of mesh free Lagrangian two-dimensional non-cohesive sediment transport model applied to a two-phase flow over an initially trapezoidal-shaped sediment embankment. The governing equations of the present model are the Navier-Stocks equations solved using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. To simulate the movement of sediment particles, the model considers a powerful two-part technique; when the sediment phase has rigid behavior, only the force term due to shear stress in the Navier-Stokes equations is used for simulation of sediment particles' movement. Otherwise, all the Navier-Stokes force terms are used for transport simulation of sediment particles. In the present model, the interactions between different phases are calculated automatically, even with considerable difference between the density and viscosity of phases. Validation of the model is performed using simulation of available laboratory experiments, and the comparison between computational results and experimental data shows that the model generally predicts well the flow propagation over movable beds, the induced sediment transport and bed changes, and temporal evolution of embankment breaching.展开更多
Under the action of marine currents,non-cohesive sediments evolve by bed-load,by saltation or suspension depending on their granulometry.Several authors have considered that the movement of sediment is bidimensional a...Under the action of marine currents,non-cohesive sediments evolve by bed-load,by saltation or suspension depending on their granulometry.Several authors have considered that the movement of sediment is bidimensional and modelized the effects of swell by a constant velocitynear the seabed.Here we have studied the velocity profile of fluctuating currents near the seabed and studied the movement of sediment in 3D.The results show that in the areas of study(surf and swash)the movement of sediment occurs in a volume,and the evolution of sediment varies from an areato another.The obtained theoretical profiles of the position and velocity vectors confirm the observations of several authors.展开更多
Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including th...Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including the particle contact stiffness and the particle-particle friction. These parameters cannot easily be measured in the laboratory or directly related to measurable, physical material parameters. Therefore, a calibration process is typically used to determine the values for use in simulations of physical systems. This paper focuses on how to define the particle stiffness for the discrete element modelling in order to perform realistic simulations of granular materials in the case of linear contact model. For that, laboratory tests and numerical discrete element modelling of triaxial compression tests have been carried out on two different non-cohesive soils i.e. poorly graded fine sand and gap graded coarse sand. The results of experimental tests are used to calibrate the numerical model. It is found that the numerical results are qualitatively and quantitatively in good agreement with the laboratory tests results. Moreover, the results show that the stress dependent of soil behaviour can be reproduced well by assigning the particle stiffness as a function of the particle size particularly for gap graded soil.展开更多
基金Project supported by the National Basic Research and Development Program of China (973 Program, Grant No.2011CB403304)the National Natural Science Foundation of China (Grant No. 11272240)
文摘This paper presents an experimental study of the overtopping breach of homogeneous non-cohesive levee or dike in a 180°bend rectangular flume. Detailed experimental and numerical results provide information on the breach flow discharge and longitudi- nal and transversal breach profiles for this type of levee. It is indicated that the water level and the flow discharge in the river and the levee material properties are significant influencing factors for the breach evolution. The plane form of the breach is approximately an asymmetrical hyperbola. A formula with a non-constant flow factor is proposed to compute this kind of breach discharge.
文摘The subject of present study is the application of mesh free Lagrangian two-dimensional non-cohesive sediment transport model applied to a two-phase flow over an initially trapezoidal-shaped sediment embankment. The governing equations of the present model are the Navier-Stocks equations solved using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. To simulate the movement of sediment particles, the model considers a powerful two-part technique; when the sediment phase has rigid behavior, only the force term due to shear stress in the Navier-Stokes equations is used for simulation of sediment particles' movement. Otherwise, all the Navier-Stokes force terms are used for transport simulation of sediment particles. In the present model, the interactions between different phases are calculated automatically, even with considerable difference between the density and viscosity of phases. Validation of the model is performed using simulation of available laboratory experiments, and the comparison between computational results and experimental data shows that the model generally predicts well the flow propagation over movable beds, the induced sediment transport and bed changes, and temporal evolution of embankment breaching.
基金the "Ministère d’Etat Chargé de l’Enseignement Supérieure et de la Recherche Scientifque (MECESRS)" for their support during this work
文摘Under the action of marine currents,non-cohesive sediments evolve by bed-load,by saltation or suspension depending on their granulometry.Several authors have considered that the movement of sediment is bidimensional and modelized the effects of swell by a constant velocitynear the seabed.Here we have studied the velocity profile of fluctuating currents near the seabed and studied the movement of sediment in 3D.The results show that in the areas of study(surf and swash)the movement of sediment occurs in a volume,and the evolution of sediment varies from an areato another.The obtained theoretical profiles of the position and velocity vectors confirm the observations of several authors.
文摘Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including the particle contact stiffness and the particle-particle friction. These parameters cannot easily be measured in the laboratory or directly related to measurable, physical material parameters. Therefore, a calibration process is typically used to determine the values for use in simulations of physical systems. This paper focuses on how to define the particle stiffness for the discrete element modelling in order to perform realistic simulations of granular materials in the case of linear contact model. For that, laboratory tests and numerical discrete element modelling of triaxial compression tests have been carried out on two different non-cohesive soils i.e. poorly graded fine sand and gap graded coarse sand. The results of experimental tests are used to calibrate the numerical model. It is found that the numerical results are qualitatively and quantitatively in good agreement with the laboratory tests results. Moreover, the results show that the stress dependent of soil behaviour can be reproduced well by assigning the particle stiffness as a function of the particle size particularly for gap graded soil.