# International Association for Hydro-Environment Engineering and Research

IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
 You are here : eLibrary : IAHR World Congress Proceedings : 33rd Congress - Vancouver (2009) : Topic A: Advances in the Fundamentals of Water Science and Engineering : Lateral dispersion in vegetated flows: reynolds-number dependence at transitional reynolds numbers
 Lateral dispersion in vegetated flows: reynolds-number dependence at transitional reynolds numbers Author : Yukie Tanino, Heidi M. Nepf Lateral dispersion in an array of randomly distributed cylinders, a model for emergent aquatic plants, at Reynolds numbers lower than in fully turbulent flow is considered. Theory developed by Tanino and Nepf (2008) implies that, for cylinder volume fractions  > 0.19, the asymptotic dispersion coefficient normalized by the mean pore velocity and cylinder diameter, Kyy/ (ud), does not depend strongly on the Reynolds number, Red. In contrast, for  < 0.19, the theory implies that Kyy/ (ud) decreases with decreasing Red in transitionally turbulent flows. At lower Red, cylinder wakes may exhibit an unsteady laminar regime, in which the Red dependence of Kyy/ (ud) is expected to be complex. To evaluate these conjectures, laboratory measurements of lateral dispersion at  = 0.060 and  = 0.35 at Red = 38−170 and Red = 48−390, respectively, are examined in this paper. Kyy/ (ud) at (,Red) = (0.35, 300−390), which is prior to the onset of full turbulence, was indeed the same as that predicted for fully turbulent flows. In contrast, at  = 0.060, Kyy/ (ud) was 16% smaller than that predicted for fully turbulent flow at Red = 160 − 170. As Red was reduced, Kyy/ (ud) increased by 60% between Red = 160 − 170 and Red = 97 − 99, then remained constant between Red = 97 − 99 and Red = 59 − 61. File Size : 249,929 bytes File Type : Adobe Acrobat Document Chapter : IAHR World Congress Proceedings Category : 33rd Congress - Vancouver (2009) Article : Topic A: Advances in the Fundamentals of Water Science and Engineering Date Published : 09/08/2009 Download Now