Mean Flow in a Submerged Hydraulic Jump with Baffle Blocks
Publication: Journal of Engineering Mechanics
Volume 140, Issue 5
Abstract
The flow in a submerged hydraulic jump with three-dimensional (3D) baffle blocks was experimentally studied. An incoming jet with varying supercritical Froude numbers was deflected with one or two rows of 3D baffle blocks for different downstream water depths. Depending on the submergence factor, two flow regimes were observed for which the time-averaged 3D velocity field was measured with an acoustic Doppler velocimeter (ADV). Measurements were conducted at different stations located both upstream and downstream of the blocks and above the crest of the blocks. Velocity measurements were made in a plane located at the center of the middle block (i.e., the centerplane of the flume) and, also, in a plane located at the midpoint between the blocks (off-centerplane). The mean flow pattern was found to be significantly different for the two flow regimes. In the deflected surface jet (DSJ) regime, which occurred at low submergence factors, the major flow features were a small surface roller upstream of the blocks and a larger recirculating flow region located downstream of the blocks. The reattaching wall jet (RWJ) regime, which was formed at large submergence factors, could be characterized by a large surface roller and a small standing eddy just behind the blocks in the centerplane. In both flow regimes, the maximum longitudinal velocity component was observed to decrease rapidly at the blocks and the jet half-width was found to increase quickly. The DSJ regime was found to have a smaller streamwise dimension and to be more effective in reducing the streamwise velocity and increasing the jet half-width. These features can be considered an advantage of the DSJ regime over the RWJ regime; that is, hydraulic structures should be designed such that the DSJ regime occurs over the entire range of tailwater depths that are likely to occur.
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Published In
Journal of Engineering Mechanics
Volume 140 • Issue 5 • May 2014
Copyright
© 2014 American Society of Civil Engineers.
History
Received: Jan 7, 2013
Accepted: Sep 24, 2013
Published online: Jan 15, 2014
Published in print: May 1, 2014
Discussion open until: Jun 15, 2014
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