Vortex ripple is widely formed in the coastal region, and the dynamic ofvortex is quite important because it is responsible for sediment transport. The flow structurearound the vortex ripples can be modeled as 2D flow...Vortex ripple is widely formed in the coastal region, and the dynamic ofvortex is quite important because it is responsible for sediment transport. The flow structurearound the vortex ripples can be modeled as 2D flow due to the geometry of the flow boundaries. Inthis paper, 2D Large-Eddy-Simulation (LES) method was used to predict the flow structure and thedynamic of vortex in the bottom layers under the action of the wave, the numerical simulationresults show a completely process of vortex formation, evolvement and disappearance. Based on thestudy of flow structure, the suspended sediment transport was modeled in present paper. Thesimulated sediment concentrations were compared to measurements from the literature. The agreementbetween the time averaged simulated concentration profiles and measurements is satisfactory. For ahigh setting velocity, the suspended sediment is confined to the vicinity of the bed, and it isdominated by the local bottom shear stress. For a small setting velocity, the suspension is moredominated by the characteristic of vortex. There are two suspended sediment transport peaks observedin the cross-section at the trough and crest in the half period, the second peak is due to theseparation bubble taking the sediment.展开更多
As wave propagates into shallow water, the shoaling effect leads to increaseof wave height, and at a certain position, the wave will be breaking. The breaking wave is powerfulagents for generating turbulence, which pl...As wave propagates into shallow water, the shoaling effect leads to increaseof wave height, and at a certain position, the wave will be breaking. The breaking wave is powerfulagents for generating turbulence, which plays an important role in most of the fluid dynamicalprocesses in the surf zone, so a proper numerical model for describing the turbulent effect isneeded urgently. A numerical model is set up to simulate the wave breaking process, which consistsof a free surface model using the surface marker method and the vertical two-dimensional model thatsolves the flow equations. The turbulence is described by Large Eddy Simulation (LES) method wherethe larger turbulent features are simulated by solving the flow equations, and the small-scaleturbulence that is represented by a sub-grid model. A dynamic eddy viscosity sub-grid scale stressmodel has been used for the present simulation. The large eddy simulation model, which we presentedin this paper, can be used to study the propagation of a solitary wave in constant water depth andthe shoaling of a non-breaking solitary wave on a beach. To track free-surface movements, The TUMMACmethod is employed. By applying the model to wave breaking problem in the surf zone, we found thatthese model results compared very well with experimental data. In addition, this model is able toreproduce the complicated flow phenomena, especially the plunging breaker.展开更多
文摘Vortex ripple is widely formed in the coastal region, and the dynamic ofvortex is quite important because it is responsible for sediment transport. The flow structurearound the vortex ripples can be modeled as 2D flow due to the geometry of the flow boundaries. Inthis paper, 2D Large-Eddy-Simulation (LES) method was used to predict the flow structure and thedynamic of vortex in the bottom layers under the action of the wave, the numerical simulationresults show a completely process of vortex formation, evolvement and disappearance. Based on thestudy of flow structure, the suspended sediment transport was modeled in present paper. Thesimulated sediment concentrations were compared to measurements from the literature. The agreementbetween the time averaged simulated concentration profiles and measurements is satisfactory. For ahigh setting velocity, the suspended sediment is confined to the vicinity of the bed, and it isdominated by the local bottom shear stress. For a small setting velocity, the suspension is moredominated by the characteristic of vortex. There are two suspended sediment transport peaks observedin the cross-section at the trough and crest in the half period, the second peak is due to theseparation bubble taking the sediment.
文摘As wave propagates into shallow water, the shoaling effect leads to increaseof wave height, and at a certain position, the wave will be breaking. The breaking wave is powerfulagents for generating turbulence, which plays an important role in most of the fluid dynamicalprocesses in the surf zone, so a proper numerical model for describing the turbulent effect isneeded urgently. A numerical model is set up to simulate the wave breaking process, which consistsof a free surface model using the surface marker method and the vertical two-dimensional model thatsolves the flow equations. The turbulence is described by Large Eddy Simulation (LES) method wherethe larger turbulent features are simulated by solving the flow equations, and the small-scaleturbulence that is represented by a sub-grid model. A dynamic eddy viscosity sub-grid scale stressmodel has been used for the present simulation. The large eddy simulation model, which we presentedin this paper, can be used to study the propagation of a solitary wave in constant water depth andthe shoaling of a non-breaking solitary wave on a beach. To track free-surface movements, The TUMMACmethod is employed. By applying the model to wave breaking problem in the surf zone, we found thatthese model results compared very well with experimental data. In addition, this model is able toreproduce the complicated flow phenomena, especially the plunging breaker.
