Large eddy simulation of flow in a channel with multiple lateral groyne fields

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Large Eddy Simulation (LES) is used to study the flow in a straight open channel containing a multiple-embayment groyne field with fully emerged groynes. The model is validated using data collected at the free surface in a previous experimental study. It is found that the flow inside the mixing layer region between the embayments and the channel is strongly non-uniform over the depth. The large-scale eddies that populate the mixing layer can penetrate the embayment region over lateral distances of the order of the channel depth and advect with them channel fluid inside the embayment where it is mixed with the embayment fluid by the small scales. The other main mixing mechanism is due to the injection of patches of high-vorticity mixing-layer fluid near the tip of the downstream groyne. It is shown that in average most of the fluid leaves the embayment region via the top layer of the embayment-channel interface and enters the embayment region at levels situated around the mid-depth of the interface surface. This explains why the mass exchange coefficients are overestimated when predicted using methods that employ floating particles as a tracer