3D Numerical Simulation of Flow and Local Scour around a Spur Dike

The present paper uses FLOW-3D software to simulate the three-dimensional flow and local scour around a non-submerged spur dike. The Navier-Stokes equations are solved with Finite Volume Method. Selected turbulence model is RNG kappa-epsilon model and the bed-load transport model is based on Shields number. The volume of fluid (VOF) method is employed in FLOW-3D tracking fluid-air or fluid-fluid interfaces. Simulated results of mean flow and turbulence for fixed bed case include backflow length, the distribution of velocity, turbulent energy and dissipation. This provides a theoretical foundation for explaining erosion mechanism. For movable bed, the results verify that all of the scour process can be divided into three stages: initial stage, main scour stages and balance stage, most of the scour is completed in the first two stages. Obtained depth and scope of scoured pit around spur dike coincide well with experiment. The analysis of flow field distribution shows that the formation of the scoured surface is mainly influenced by submerged flow and horseshoe vortex. In main scour stage, the intensity of submerged flow and horseshoe vortex increased rapidly, so the scour pit depth increased accordingly. With the increasing of the depth of scour pit, the flow velocity decreases, submerged flow and horseshoe vortex strength decreased until water flow velocity reduced to cannot take away the sediment.