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You are here : eLibrary : IAHR World Congress Proceedings : 34th Congress - Brisbane (2011) : THEME 5: Environmental Hydraulics and Hydrology : Effect of reynolds number on the propagation of lock exchange gravity currents in a porous medium
Effect of reynolds number on the propagation of lock exchange gravity currents in a porous medium
Author : T. Tokyay1, Y. A. Mohamed1,2, and G. Constantinescu1
Large Eddy Simulation (LES) is used to investigate the evolution of gravity currents with a high volume of release propagating through an array of uniformly distributed cylindrical obstacles. The paper discusses the effect of the porosity and of the Reynolds number, Re, defined with the channel depth and the buoyancy velocity on the structure of the lock-exchange flow and front velocity. The porous medium consists of an array of staggered cylinders of same diameter that are distributed over the whole depth and length of the channel. Simulation results show that for sufficiently high porosities, the interface elevation varies linearly with the streamwise position until close to the head of the current, regardless of the value of the Reynolds number. Consistent with experiments, LES shows that low Reynolds number currents transition to a drag dominated regime in which the front velocity, Uf, is proportional with t-1/2, where t is the time measured starting at the release time. By contrast, high Reynolds number currents, for which the cylinder Reynolds number (ReD) is high enough such that the drag coefficient on the cylinders can be considered constant, transition first to a drag dominated regime in which Uf~t-0.25. However, after a sufficient long time, such that ReD becomes sufficiently low for the drag coefficient to become proportional to 1/ReD, the current transitions to a drag dominated regime in which Uf~t-1/2.
File Size : 594,762 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 34th Congress - Brisbane (2011)
Article : THEME 5: Environmental Hydraulics and Hydrology
Date Published : 01/07/2011
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