IAHR, founded in 1935, is a worldwide independent memberbased organisation of engineers and water specialists working in fields related to the hydroenvironmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and ecohydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.





Lateral dispersion in vegetated flows: reynoldsnumber 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/ (ud), does not depend strongly on the Reynolds number, Red. In contrast, for < 0.19, the theory implies that Kyy/ (ud) 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/ (ud) 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/ (ud) 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/ (ud) was 16% smaller than that predicted for fully turbulent flow at Red = 160 − 170. As Red was reduced, Kyy/ (ud) 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 







