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Circulation Generation and Vortex Ring Formation by Conic Nozzles

Rosenfeld, Moshe and Katjia, Kakani and Dabiri, John O. (2009) Circulation Generation and Vortex Ring Formation by Conic Nozzles. Journal of Fluids Engineering, 131 (9). Art. No. 091204. ISSN 0098-2202.

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Vortex rings are one of the fundamental flow structures in nature. In this paper, the generation of circulation and vortex rings by a vortex generator with a static converging conic nozzle exit is studied numerically. Conic nozzles can manipulate circulation and other flow invariants by accelerating the flow, increasing the Reynolds number, and by establishing a two-dimensional flow at the exit. The increase in the circulation efflux is accompanied by an increase in the vortex circulation. A novel normalization method is suggested to differentiate between two contributions to the circulation generation: a one-dimensional slug-type flow contribution and an inherently two-dimensional flow contribution. The one-dimensional contribution to the circulation increases with the square of the centerline exit velocity, while the two-dimensional contribution increases linearly with the decrease in the exit diameter. The two-dimensional flow contribution to the circulation production is not limited to the impulsive initiation of the flow only (as in straight tube vortex generators), but it persists during the entire ejection. The two-dimensional contribution can reach as much as 44% of the total circulation (in the case of an orifice). The present study offers evidences on the importance of the vortex generator geometry, and in particular, the exit configuration on the emerging flow, circulation generation, and vortex ring formation. It is shown that both total and vortex ring circulations can be controlled to some extent by the shape of the exit nozzle.

Item Type:Article
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Dabiri, John O.0000-0002-6722-9008
Additional Information:©2009 American Society of Mechanical Engineers. Received 14 April 2009; revised 8 July 2009; published 18 August 2009.
Subject Keywords:multiphase flow, nozzles, vortices; vortex ring, circulation, nozzle, laminar flow, CFD
Issue or Number:9
Classification Code:# 47.32.-y Vortex dynamics; rotating fluids # 47.55.-t Multiphase and stratified flows # 47.60.Kz Flows and jets through nozzles
Record Number:CaltechAUTHORS:20091012-123135148
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16244
Deposited By: George Porter
Deposited On:12 Oct 2009 21:11
Last Modified:09 Mar 2020 13:18

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