[AHW33-07] Sediment Transport Modeling Beyond Normality: Estimation of Sediment Concentrations Accounting for Spatial Influence of Turbulence Coherent Structures
★Invited Papers
キーワード：Turbulent Coherent Structures, Sediment Transport, Memory Effect, Spatial distribution of turbulent structures
Recent experiments have established that the sediment particle motion, especially for particles near the bed, may not follow the normal (Fickian) diffusion behavior. To modify the diffusion equation where the fluctuation velocity is based on the normal distribution, this study attempts to acquire some physical insight into the particle diffusion behavior by considering more details on turbulent coherent structures including the asymmetry of velocity fluctuations and spatial distributions of turbulent coherent structures. The uniform momentum zones (UMZ) are further identified and consequently the spatial locations of the edges that demarcate UMZs can be estimated. Once UMZs in the turbulent boundary layers can be characterized, the streamwise momentum deficit, and occurrences of ejection events and sweep events in the vicinity of UMZ edges under different Reynolds numbers can be simulated. The simulation results identify the contributions of these structures to suspended sediment transport, and show the time coherence of flow velocity may be essential for flow to carry sediment particles in suspension. The spatial influence of turbulent coherent structures on sediment particle trajectory can also be demonstrated.