Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens
Publication: Journal of Hydraulic Engineering
Volume 147, Issue 8
Abstract
Coanda-effect screens exclude coarse and fine debris from a variety of water intakes. Water overflows an inclined wedge-wire screen with tilted wires that shear high velocity flow from the bottom of the water column. The screens hydraulically self-clean, making them ideal for remote, nonpowered sites. Flow conditions vary widely over the length of most screens. Previous testing related flow capacity to gravitational, surface tension, and viscous forces, but the range of flow conditions was limited versus potential applications. This study tested small sections of prototype-scale screens at varying slopes, and discharge coefficients were related to Froude and Weber numbers. Tests with variable water temperatures proved that screen performance is independent of Reynolds number and viscosity, but depends strongly on surface tension. Several screen geometries (i.e., wire size, shape, and slot size) were tested, and the performance of all screens could be modeled with power curve functions of the Weber number modified by the Froude number. Individual screens exhibited some unique performance characteristics, but 10 of the 13 screens could be modeled effectively as a group.
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Data Availability Statement
All data, models, and code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This work was funded by the Bureau of Reclamation Research Office, Science & Technology Program. Student intern Dallas McKeough assisted with the collection of experimental data during 2016. Bryan Heiner provided internal peer review of this paper and was instrumental with model maker Marty Poos in configuring the flow chiller that enabled the cold-water testing. Machinist Dane Cheek constructed many of the unique test facility components. The screen test facility originally was constructed for work funded by Coanda Water Intakes, Ltd., Kamloops, BC, Canada.
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Journal of Hydraulic Engineering
Volume 147 • Issue 8 • August 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Jul 17, 2020
Accepted: Mar 15, 2021
Published online: Jun 10, 2021
Published in print: Aug 1, 2021
Discussion open until: Nov 10, 2021
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