Author(s): Yafei Jia; Mustafa Altinakar; M. Sukru Guney; Gokcen Bombar
Linked Author(s): Gökçen Bombar, Mustafa Altinakar
Keywords: Numerical simulation; Physical model; Local scour; Unsteady flow; Sediment transport
Abstract: Local scouring caused by the dynamic interaction between flow, bridge piers and the sediment bed is an important threat to engineering structures constructed in alluvial rivers. Studies using laboratory experiments, field measurements, and numerical simulations have contributed to the understanding of the complex three-dimensional nature of the flow field around bridge piers and the associated turbulence characteristics. The numerical modeling of the scouring process and the prediction of the depth of local scouring under a variety of conditions, however, still remains a challenging problem. This paper presents a numerical model of the local scouring around cylindrical bridge piers by implementing a novel erosion and sediment transport approach in a finite element based three-dimensional free-surface turbulent flow model, CCHE3D, developed at the National Center for Computational Hydroscience and Engineering of the University of Mississippi, USA. In this approach, the turbulence kinetic energy of the approach flow and that generated around the cylindrical bridge pier are approximated and assumed to be dominant factors in scouring the bed. The turbulence energy penetrating into the bed sediment due to the vertical flow is formulated and used as forcing to entrain the sediment from the bed in addition to the bed shear stress. A non-equilibrium bed load transport approach is used to model the erosion and sediment transport processes. Numerical simulations are conducted using experiment data of clear water scour and live-bed scour cases. The former is of steady flow and uniform sediment, the latter is of unsteady flow and non-uniform sediments. Good agreements of the simulation results and the measured data have been obtained.
Year: 2013