Author(s): Pedro Ramos; Joao Pedro Pego; Rodrigo Maia
Linked Author(s): Pedro Xavier Ramos
Keywords: Scour; OpenF OAM; Large Eddy Simulation; CFD
Abstract: Scour is a major source of damages to bridge foundations in riverbeds, which increases the risk of stability failure of the complete bridge structure. In Portugal, the tragic accident of Entre-osRios in the Douro river was partly due to scouring in one of the bridge piers. Local scour around bridge piers has been investigated extensively. There are many studies about it, most of it based on experimental work, focusing on the prediction of maximum equilibrium depth. Nevertheless, there is still a lack of knowledge on the driving mechanisms that trigger and maintain the scouring process. The paper is intended to add knowledge to this field by means of numerical simulations. The main goal of this study is the numerical simulation of the flow around an isolated circular pier, using the Open FOAM toolbox, in two fixed bed configurations: one with a flat fixed bed, correspondent to the beginning of the scour process; the other representing the geometry of the bed after the equilibrium scour depth has been reached, that geometry being obtained experimentally. The velocity and vorticity field, the bed shear stress and the drag coefficient on the pier will be characterized for the two different configurations, applying the Large Eddy Simulation turbulence model. The Open FOAM results will be validated against data obtained with Fluent by Ramos (2012). Fluent and Open FOAM are two CFD tools largely used in the industry and research on fluid mechanics, the first a proprietary software and the second a free and open source one. The two three-dimensional numerical models used allow to study flow structures like the horseshoe vortex, which has a crucial role in the scour process. The performance of both CFD tools will be analyzed and compared. The numerical results will be discussed and validated against data obtained from bibliography accepted as reference.
Year: 2014