A Two-phase Turbulent Flow Model for Suspended Sediment Transport under Waves
|Keywords||two-phase flow suspended sediment transport unidirectional flow oscillatory flow water wave|
Development of advanced numerical models for sediment-laden flows is of current significance because improvement of our understanding on sediment transport phenomena in coastal environment has been pushed for decades to meet the requirement from engineers who are in charge of planning, design, or construction of coastal and harbor facilities. With the enhancement of two-phase flow models and advances in numerical methods, it is now possible to apply numerical models to study sediment transport problems with low concentration. This thesis is based on newly derived governing equations of sediment-laden flows. Relevant numerical method is also proposed. The numerical model is extensively verified.Suspended sediment transport under unidirectional flow condition is investigated. Vertical distributions of the sediment concentration and the diffusion coefficient are carefully discussed. The effectiveness of two turbulence models, i.e., Ap model and k p model, is also studied. Suspended sediment motion in the boundary layer under oscillatory flow condition is also studied. The characteristics of the turbulent flow and its resulted sediment transport in the boundary layer are demonstrated. Variation of the various inter-phase forces in the time and space are examined.To consider sediment transport under wave motion, numerical methods are established so as to represent wave-making and wave absorbing, and to trace the free surface, under two-phase flow conditions. The numerical model is then used to compute the vertical distribution of the averaged sediment concentration within a wave period. Variation of the various inter-phase forces in the time and space are shown. Sediment transport rate under waves is also briefly discussed.