Author(s): Cristian Escauriaza; Fotis Sotiropoulos
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Abstract: In this investigation we develop a CFD model to simulate the localized erosion and pattern formation produced by the turbulent horseshoe vortex system (HSV) around a cylindrical pier. We carry out detached eddy simulations (DES) of the 3D flow past the cylinder in clear-water scour conditions, and implement a novel unsteady bed-load transport and erosion model to determine the sediment flux in non-equilibrium conditions to compute the instantaneous bed elevation. A remarkable process captured by our model is the development of bed-forms along the legs of the HSV system. The interaction of the vortical structures with the wall produces a bed instability that grows and propagates, generating ripples that travel and merge in the downstream direction showing the same dynamic features observed in experiments. This is the first 3D computational model to fully capture the formation and development of bed-forms, coupling the bed dynamics with the flow. The results also suggest that the model will constitute a powerful tool to understand the dynamics of bed-forms and its relation to the coherent structures in turbulent flows.
Year: 2009