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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
Subject(s):Water resources center
Water resources center--Illinois
Hydrology and hydraulics
Boundary shear
Sublayer turbulence
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.
Issue Date:1968-01
Publisher:University of Illinois at Urbana-Champaign. Water Resources Center
Genre:Report (Grant or Annual)
Sponsor:U.S. Department of the Interior
U.S. Geological Survey
Rights Information:Copyright 1968 held by Harry G. Wenzel, Michael J. Mathews
Date Available in IDEALS:2016-05-25

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