FUNDAMENTAL PROPERTIES OF FLOWS IN OPEN CHANNELS WITH DEAD ZONE

Authors
Citation
I. Kimura et T. Hosoda, FUNDAMENTAL PROPERTIES OF FLOWS IN OPEN CHANNELS WITH DEAD ZONE, Journal of hydraulic engineering, 123(2), 1997, pp. 98-107
Citations number
26
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Engineering, Mechanical","Engineering, Civil","Water Resources
ISSN journal
0733-9429
Volume
123
Issue
2
Year of publication
1997
Pages
98 - 107
Database
ISI
SICI code
0733-9429(1997)123:2<98:FPOFIO>2.0.ZU;2-R
Abstract
The fundamental behavior of unsteady hows in an open channel with a re ctangular dead zone is investigated experimentally and numerically to clarify the mass-exchange mechanism near an embayment along a river ba nk. Typical how features such as generation of a coherent vortex due t o shear instability in the mixing layer between two flow regions (main -channel flow and dead zone) and water-surface oscillation (seiche) in the dead zone are shown by the findings of laboratory tests. These ho w features can be reproduced numerically by plane two-dimensional (2D) open-channel flow equations in the variable grid system. Model perfor mance was examined in detail by changing the grid size and constants. The calculated values for temporal and spatial variations in velocity and depth are compared with observed values. Examination of the calcul ated results shows that temporal velocity variations at the interface can be decomposed into two components due to seiche and shear instabil ity; during one seiche, cycle-velocity variations caused by instabilit y are amplified to the large-scale vortex selectively by the interacti on between seiche and instability components. This selective amplifica tion process can be detected in a series of photographs of the surface flow pattern as well.