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Drag coefficient of unsubmerged rigid vegetation stems in open channel flows

Author(s): Umesh C. Kothyari; Kenjirou Hayashi; Haruyuki Hashimoto

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Keywords: Bed particle resistance; Channel flow; Drag coefficient; Drag force; Load cell; Stem resistance; Vegetation

Abstract: Results of an experimental study on the drag force measurement involving a single stem kept in a channel flow stem array are presented. The data collected herein and those from literature indicate that the stem drag coefficient logarithmically increases with the areal stem density. The stem Reynolds number is noticed to have only a small effect on the stem drag coefficient which was however found to depend on the stem staggering pattern. The drag coefficient is less influenced by the Froude number in subcritical flows but it decreases with the Froude number in supercritical flows. New relationships are proposed for the stem drag coefficient which appear useful in partitioning the total flow resistance of vegetated bed streams into the stem and the bed particle resistances. The bed particle resistance applies to sediment transport through such vegetated flows for which the average flow velocity is available.


Year: 2009

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