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Open Channel Flow Past a Rectangular Patch of Submerged Vegetation

Author(s): Mete Koken; George Constantinescu

Linked Author(s): George Constantinescu

Keywords: No Keywords

Abstract: Flow past a rectangular patch of submerged vegetation placed at one side of a straight open channel is investigated using Detached Eddy Simulation. The plant stems are modeled as straight solid circular cylinders. The patch width is one third of the channel width and the heights of the plant stems are half of the channel depth, D. The cylinders are distributed fairly uniformly within the patch and the solid volume fraction is SVF=10%. The diameter of the cylinders in the array is d=0.1D. The channel Reynolds number is close to 20,000. The flow around the patch is characterized by the formation of two mixing layers, a horizontal one and a vertical one at the interface between the bleeding flow inside the patch and the flow advected on top of the submerged patch. It is shown that the eddies generated by the wakes of the cylinders situated close to the upstream and lateral faces of the vegetation patch are the main contributors to the turbulent kinetic energy (TKE) inside the patch and the horizontal mixing layer. For the SVF and d/D considered in the present study, only the first four rows of cylinders are subject to relatively important drag forces, of the same order of magnitude as the one observed for isolated cylinders of same diameter. Finally, a strong downflow component is observed in front of the patch and in the horizontal mixing layer close to the interface with the patch and an upflow region is present on the outer side of the horizontal shear layer. These motions are relevant for understanding nutrient and fine sediment transport processes.

DOI:

Year: 2018

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