The present study investigates physical aspects of sediment transport in an open channel flow. Direct numerical simulationswere carried out using an improved immersed boundary method for the solid phase, thus resolving the geometry of each individual particle. For the proper modeling of particle-particle interactions, a newly developed collision model, the Adaptive Collision Model (ACM) was employed. TheACMaccounts for both normal and tangential forces as well as for lubrication forces and results in an efficient model to represent four-way coupling of continuous fluid phase and the dispersed solid phase. It provides a more realistic model for the inter-particle forces than previously available, which significantly improves the modeling of bed load transport.The simulations carried out for this study are turbulent channel flows with a box size of 12H ×H ×6H where H is the water depth. The solid phase consists of mono-disperse spheres with a diameter of H/9 that form a fixed sediment bed of one hexagonal packed layer and 2000 mobile particles of the same size on top. Two values of the Shields parameter Owere considered, O=7.52 · 10 -2 and O=2.51 · 10 -2, one above and one below the threshold of incipient motion Ocrit =3.4 · 10 -2. The study analyzes in detail the resulting bed load transport as well as the evolution of bed forms as a function of the Shields parameter. For high Shields parameter, characteristic clusters appear with particles traveling in a highly correlated manner. A low Shields parameter in contrast yields ribbons of resting particles that form in the streamwise direction.
|Title of host publication
|River Flow 2012 - Proceedings of the International Conference on Fluvial Hydraulics
|Number of pages
|Published - 1 Nov 2012
|International Conference on Fluvial Hydraulics, River Flow 2012 - San Jose, Costa Rica
Duration: 5 Sept 2012 → 7 Sept 2012
http://sdg.iisd.org/events/river-flow-2012-international-conference-on-fluvial-hydraulics/ (Link to conference website)
|International Conference on Fluvial Hydraulics, River Flow 2012
|5/09/12 → 7/09/12
|This conference is co-organized by the International Association for Hydro-Environment Engineering and Research, and the Association of Civil Ingineers of Costa Rica. It brings together participants to discuss themes including river hydrodynamics, river morphology and sediment transport and river engineering. Sub-topics to be addressed are: transport of sediment; sedimentation in reservoirs; transport and fate of pollutants in rivers; flow management and flood control; river habitat management and river restoration; and navigation waterways and dredging. River Flow 2012 will be held together for the first time with the XXV IAHR Latin-American Congress on Hydraulics, an event that is taking place from 9-12 September 2012, at the same venue.