Effect of Lateral Confinement on Initial Dilution of Vertical Round Buoyant Jet
Publication: Journal of Hydraulic Engineering
Volume 124, Issue 3
Abstract
In relatively shallow coastal waters, a submarine outfall pipeline is often laid in a dredged trench and the wastewater jet discharges inside a concentric enclosure (a protective riser tube) before release at the seabed. The effect of such lateral confinement over a finite vertical length on the mixing of a buoyant jet is studied experimentally for a wide range of geometries. A confinement index β=Hr/(Dr−D) is proposed to categorize the confined buoyant jet, where Hr and Dr are the height and diameter of the confinement, respectively, and D is the jet diameter. Compared to the dilution of the corresponding free buoyant jet, it is found that mixing is impaired for β≥ 3. For β>> 1, the jet is highly confined and there is virtually no dilution within the riser. For β≤ 1.5, the confinement has no effect. For 1.5 ≤β≤ 3, a wall-attached swirling plume with enhanced dilution is observed, and the mixing behavior is complex. Simple relations for predicting the initial dilution of a laterally confined plume are presented.
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Information & Authors
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Published In
Journal of Hydraulic Engineering
Volume 124 • Issue 3 • March 1998
Pages: 263 - 279
Copyright
Copyright © 1998 American Society of Civil Engineers.
History
Published online: Mar 1, 1998
Published in print: Mar 1998
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