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K. Warren Frizell. 2008. "Laboratory Studies of High Velocity Flows Over Open Offset Joints". Bureau of Reclamation, Report Number PAP-979.

Abstract: Laboratory tests were completed in Reclamation’s Water Resources Research Laboratory to extend the available data on uplift pressures generated by high velocity flows over offset joints. In addition, magnitudes of flows into the joints or cracks were measured for various configurations. Three joint geometries were tested: sharp edges (90-degree), 1/8- inch chamfered edges (45-degree), and edges with a 1/8-inch-radius in combinations of joint/crack gaps ranging from 1/8-inch to 1/2-inch and offsets into the flow ranging from 1/8-inch to 3/4-inch. Only sharp-edged joints will be reported in this paper. Velocities ranging from about 10 ft/s up to 55 ft/s were tested. Mean uplift pressures downstream from the offset were measured for all cases. The cavity beneath the test section could be closed, generating the maximum uplift, or opened to allow flow to enter the cavity through the joint/crack. This test facility feature allowed for measurement of a slightly reduced uplift pressure and flow rates through the open joint/crack area. Uplift pressure and flow rate data from this study will be used to reduce the uncertainty in analyses used during risk assessments to provide improved estimates of the level of effort required to bring a spillway or outlet works into a safe operating condition for a variety of geometries.

Web Link: http://www.usbr.gov/pmts/hydraulics_lab/pubs/PAP/PAP-0979.pdf

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