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LES of Lock-Exchange Gravity Currents Propagating into a Fully-Vegetated Channel

Author(s): A. Yuksel Ozan; George Constantinescu

Linked Author(s): George Constantinescu

Keywords: Vegetated flows; Gravity currents; Large eddy simulation; Coherent Structures

Abstract: Gravity currents in natural environments often propagate through regions containing flow obstructions. Large Eddy Simulation (LES) is used to investigate the evolution of high Reynolds number lock-exchange gravity currents with a high volume of release propagating in a channel of uniform porosity. The porous environment corresponds to a vegetated canopy. The porous region contains arrays of uniformly-distributed small rigid cylinders of constant diameter, D. The focus is on the case of a porous channel with a solid volume fraction of 12% and a Reynolds number defined with the channel depth H and the buoyancy velocity of 15, 000. LES is used to analyze the temporal variation of the front velocity during the drag-dominated regime. The results are compared to those obtained based on shallow water theory. The effect of the relative size of the cylinders, D/H, on the flow structure and mixing is then analyzed. Results show that mixing increases monotonically with D/H. The increased in the mixing with D/H is related to the differences in the eddy content within the body of the gravity current among the different cases.


Year: 2013

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