Measuring the Dispersion Coefficient with Acoustic Doppler Current Profilers
Publication: Journal of Hydraulic Engineering
Volume 133, Issue 8
Abstract
A method is evaluated for estimating the longitudinal dispersion coefficient from velocities and bathymetry measured with an acoustic Doppler current profiler (ADCP). If shear dispersion controls the mixing, the dispersion coefficient can be estimated from measurements of velocity and depth in a cross section. The dispersion coefficient has typically been measured by costly and time-consuming tracer studies because the velocity field could not be resolved sufficiently before the flow changed. However, ADCP transects, which now are routinely used to measure discharge, provide detailed velocity and bathymetry data quickly. The dispersion coefficient is estimated from ADCP measurements from the United States Geological Survey and compared with estimates from dye studies. Half of the estimates of fall within 50% of the values from tracer studies, and 85% are within a factor of 3. The ADCP method is at least as accurate as the best empirical formula considered. Both the comparison of field data and an analysis with theoretical velocity profiles suggest that the error in will be largest when the velocity profile is nearly uniform.
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Acknowledgments
The writers thank Kevin Oberg and David Mueller of the USGS Hydroacoustics Work Group for their advice and suggestions and the following people at USGS District Offices for their assistance in obtaining data: Rick Crowfoot, Bob Boulger, and Paul Diaz Jr. (Colorado); Von Miller (Iowa); Kevin Johnson (Illinois); Brian Loving (Kansas); Michael J. Anderson (Nebraska); John Nantz (Pennsylvania); and Fred Brogan (West Virginia).
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 133 • Issue 8 • August 2007
Pages: 977 - 982
Copyright
© 2007 ASCE.
History
Received: Jul 18, 2005
Accepted: Dec 28, 2006
Published online: Aug 1, 2007
Published in print: Aug 2007
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