Coherent Structures in Flat-Bed Abutment Flow: Computational Fluid Dynamics Simulations and Experiments |
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Authors: | Antonis Chrisohoides Fotis Sotiropoulos Terry W Sturm |
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Affiliation: | 1Graduate Research Assistant, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA?30332-0355. 2Associate Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA?30332-0355. 3Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA?30332-0355.
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Abstract: | Numerical computations and laboratory experiments are carried out to investigate the three-dimensional structure of large-scale (coherent) vortices induced by bridge abutments on a flat bed. A finite-volume numerical method is developed for solving the unsteady, three-dimensional Reynolds-averaged Navier–Stokes equations, closed with the k–ω turbulence model, in generalized curvilinear coordinates and applied to study the flow in the vicinity of a typical abutment geometry with a fixed, flat bed. The computed flowfields reveal the presence of multiple, large-scale, unsteady vortices both in the upstream, “quiescent,” region of recirculating fluid and the shear-layer emanating from the edge of the foundation. These computational findings motivated the development of a novel experimental technique for visualizing the footprints of large-scale coherent structures at the free surface. The technique relies on digital photography and employs averaging of instantaneous images over finite-size windows to extract coherent eddies from the chaotic turbulent flow. Application of this technique to several abutment configurations yielded results that support the numerical findings. |
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Keywords: | Scour Bridge abutments Turbulence Models River beds |
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