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##### Just upstream from a hydraulic jump, water flows a...

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Just upstream from a hydraulic jump, water flows at a depth of 0.2 feet and average velocity V1 = Q/A1 = 10 ft/sec in a smooth horizontal rectangular channel in a laboratory. Assume that the logarithmic velocity profile is valid over the full depth of flow both just upstream and downstream from the hydraulic jump. What are the estimated bottom boundary shear stresses ?0 at the toe and just downstream of the jump? Let the jump length between these locations be 5y2 (not drawn to scale in the figure), where y2 is the downstream conjugate depth. Let the mean of the two calculated ?0 values approximate the average boundary shear on the bottom under the jump. The equation used to compute the flow depths upstream and downstream of a hydraulic jump is developed assuming that the boundary shear stress is negligible. The hydraulic jump equation (otherwise known as the conjugate depth equation) is ??yFry???221111812 Here Fr1 = Froude number of flow upstream from the jump = Vgy11 Comment on whether or not it really is justified to ignore bottom friction in deriving the conjugate depth equation.

Paper#12693 | Written in 18-Jul-2015

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