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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water engineering : Influence of model drag coefficient on les prediction accuracy of vegetated
Influence of model drag coefficient on les prediction accuracy of vegetated
Author : SATOSHI YOKOJIMA(1) & YOSHIHISA KAWAHARA(2)
ABSTRACT
The influence of the model drag coefficient on prediction accuracy of turbulent open-channel flows past emergent
vegetation canopies by a classical drag-force model has been examined. Two types of numerical simulations, i.e.,
preliminary analysis based on a two-dimensional immersed boundary method (IBM) and main analysis employing a
three-dimensional large-eddy simulation (LES) together with the drag-force model are carried out. The preliminary
analysis focuses on an estimation of an appropriate drag coefficient distribution for the target problem by fully resolving
the fluid motions around each element of the canopies in a domain of a geometrical minimal unit. The estimated drag
coefficient is then introduced into the main analysis where a wider computational domain is covered. The prediction
accuracy of the main analysis is critically evaluated against the corresponding experimental data and another set of LES
results based on a uniform drag coefficient within the canopy. The present LES with the sophisticated drag coefficient
shows an improved prediction especially on stagnation phenomena at the leading edge of the vegetation patches. The
improvement, however, is found mainly at the time-averaged flow level only. This is because the drag coefficient is
obtained from the time-averaged flow field and does not reflect the instantaneous flow features directly.
File Size : 1,379,523 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water engineering
Date Published : 19/08/2015
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