Turbulent Structure in Unsteady Depth-Varying Open-Channel Flows
Publication: Journal of Hydraulic Engineering
Volume 123, Issue 9
Abstract
Turbulence measurements over a smooth wall in unsteady depth-varying open-channel flows were conducted by the simultaneous use of a two-component laser Doppler anemometer (LDA) and a water-wave gauge. In the present study, velocity measurements in the viscous sublayer of highly unsteady flow have been first conducted to evaluate the friction velocity independently of the log-law. The von Kármán constant κ was calculated using this friction velocity. It was proven then that the value of κ was really a constant of 0.41 even in unsteady open-channel flows. Next, statistical structures of mean velocity and turbulence characteristics were investigated across the whole flow from the near-wall region up to the free surface. In particular, turbulence measurements near the depth-varying water-surface zone of flood flow were conducted successfully for the first time with the LDA; such measurements have been impossible with conventional velocity instruments such as hot-film anemometers. Mean velocity profiles and turbulence characteristics were revealed in both the rising and the falling stages of the flood period.
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Information
Published In
Journal of Hydraulic Engineering
Volume 123 • Issue 9 • September 1997
Pages: 752 - 763
Copyright
Copyright © 1997 American Society of Civil Engineers.
History
Published online: Sep 1, 1997
Published in print: Sep 1997
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