Velocity Contour Weighting Method. I: Algorithm Development and Laboratory Testing
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Abstract
An algorithm is developed for real-time estimation of the cross-sectional average velocity of a channel flow by using an upward-looking pulsed wave acoustic Doppler velocity meters (ADVM). The Velocity Contour Weighting Method (VCWM) is applicable to gradually varied flows in prismatic channels and requires little to no calibration. VCWM estimates the average velocity as a weighted average of ADVM bin velocities. Weights are based on the velocity distribution sampled by the ADVM. Collectively, the VCWM is able to adapt to a wide range of channel geometry and roughness features. Expressions for the velocity weights are developed by first applying a validated 3D computation fluid dynamics (CFD) channel flow model to a wide range of flow scenarios including differing channel geometries, discharge rates, depths, and boundary roughness. CFD simulation data are then reduced empirically with the aid of dimensional analysis to obtain the velocity weight equation. Special attention is given to the first weight accounting for near-wall velocity where the ADVM does not measure. Application of the method to a large rectangular flume shows that the VCWM predicts the average velocity with an uncertainty less than and that this uncertainty can be reduced by minimizing the buffer distance between the channel bottom and the first velocity measurement. In a companion paper, the performance of the VCWM is examined in irrigation canals with trapezoidal cross sections.
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Acknowledgments
The writers would like to acknowledge Dr. Charles Burt, Chairman, Irrigation Training and Research Center at California Polytechnic State University, San Luis Obispo, for access to the Cal Poly ITRC flume and Mohamed Grissa for his participation in the laboratory experiments. This research was made possible by a grant from the University of California Prosser Trust (UNSPECIFIEDPR-020), whose support is gratefully acknowledged.
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Published In
Journal of Hydraulic Engineering
Volume 137 • Issue 11 • November 2011
Pages: 1359 - 1367
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Apr 20, 2010
Accepted: May 10, 2011
Published online: May 12, 2011
Published in print: Nov 1, 2011
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