Microscopic determination of boundary shear and sublayer turbulence characteristics in an open channel

Wenzel, Harry G.; Mathews, Michael J.

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https://hdl.handle.net/2142/90173 Copy

Description

Title

Microscopic determination of boundary shear and sublayer turbulence characteristics in an open channel

Author(s)

• Wenzel, Harry G.
• Mathews, Michael J.

Contributor(s)

University of Illinois at Urbana-Champaign

Issue Date

1968-01

Keyword(s)

• Water resources center
• Water resources center--Illinois
• Hydrology and hydraulics
• Boundary shear
• Sublayer turbulence
• Channels

Geographic Coverage

Illinois (state)

Abstract

The application of a method of velocity determination in an open channel using a microscope and camera to record the motion of small particles suspended in water is described. Velocity measurements were made in a series of thin planes orientated parallel to the channel bottom for the case of two-dimensional laminar and turbulent open channel flow. Velocity profiles near the boundary were plotted and boundary shear computed from the rate of shear thus determined. Turbulence intensity was computed and the distribution of particle velocities examined. It was concluded that the method yields boundary shear values + to within - 15 percent and that this uncertainty can be reduced significantly. The maximum error is caused by uncertainty in the location of: the focal plane and in the location of a particle within the focal plane. This difficulty causes an even greater error in computation of turbulence intensity. This error increases as the distance from the boundary decreases, creating a serious disadvantage of the method. Particle velocity distributions exhibit a positive third moment which is in qualitative agreement with previous measurements. The results indicate that further investigation of the application of the method to open channel turbulent flow is justified. It is planned to modify the method so that particle motion can be viewed in a plane orientated normal to the boundary. This will considerably reduce the primary errors described in this report and permit more accurate turbulence measurements very near the boundary.

Publisher

University of Illinois at Urbana-Champaign. Water Resources Center

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/90173

Sponsor(s)/Grant Number(s)

• U.S. Department of the Interior
• U.S. Geological Survey

Copyright and License Information

Copyright 1968 held by Harry G. Wenzel, Michael J. Mathews

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