Author(s): H. Ahmari; A. M. Ferreira Da Silva
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Keywords: No Keywords
Abstract: In this paper, a quadrant analysis is used to gain insight into the length-scale and life-cycle of the largest horizontal coherent structures (HCS's) of an openchannel turbulent flow. The analysis rests on a series of velocity measurements of a uniform, turbulent and sub-critical flow, carried out in a 21m-long and 1m-wide laboratory channel. The conditions were such that the bed shear stress acting on the sand bed was substantially below the threshold for initiation of motion. The analysis supports earlier and independent findings by the writers indicating the presence in the flow of HCS's having an average burst-length varying from four to seven times the flow width. It also indicates that the HCS's originate at the banks, with the location of ejections and sweeps being anti-symmetrically arranged with regard to the channel centreline.
Year: 2009