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From free jets to clinging wall jets: The influence of a horizontal boundary on a horizontally forced buoyant jet

Burridge, HC and Hunt, GR (2016) From free jets to clinging wall jets: The influence of a horizontal boundary on a horizontally forced buoyant jet. Physical Review Fluids, 2. ISSN 2469-990X

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© 2017 American Physical Society. We investigate the incompressible turbulent jet formed when buoyant fluid is steadily ejected horizontally from a circular source into an otherwise quiescent uniform environment. As our primary focus, we introduce a horizontal boundary beneath the source. For sufficiently small separations, the jet attaches and clings to the boundary, herein the "clinging jet," before, farther downstream, the jet is pulled away from the boundary by the buoyancy force. For larger source-boundary separations, the buoyant jet is free to rise under the action of the buoyancy force, herein the "free jet." Based on measurements of saline jets in freshwater surroundings we deduce the conditions required for a jet to cling. We present a data set that spans a broad range of source conditions for the variation in volume flux (indicative of entrainment), jet perimeter, and jet centerline for both "clinging" and "free" jets. For source Froude numbers Fr0≥12 the data collapse when scaled, displaying universal behaviors for both clinging and free jets. Our results for the variation in the volume flux across horizontal planes, πQjet, show that within a few jet lengths of the source, πQjet for the clinging jet exceeds that of a free jet with identical source conditions. However, when examined in a coordinate following the jet centerline πQjet for free jets is greater. Finally, we propose a new parametrization for an existing integral model which agrees well with our experimental data as well as with data from other studies. Our findings offer the potential to tailor the dilution of horizontal buoyant jets by altering the distance at which they are released from a boundary.

Item Type: Article
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 12 Sep 2017 01:18
Last Modified: 22 Mar 2018 01:57