The influence of nozzle aspect ratio on plane jets

Deo, R. C., Mia, J. and Nathana, G. J. (2007) The influence of nozzle aspect ratio on plane jets. Experimental thermal and fluid science, 31 8: 825-838. doi:10.1016/j.expthermflusci.2006.08.009


Author Deo, R. C.
Mia, J.
Nathana, G. J.
Title The influence of nozzle aspect ratio on plane jets
Journal name Experimental thermal and fluid science   Check publisher's open access policy
ISSN 0894-1777
Publication date 2007-08
Year available 2006
Sub-type Article (original research)
DOI 10.1016/j.expthermflusci.2006.08.009
Volume 31
Issue 8
Start page 825
End page 838
Total pages 14
Place of publication New York NY
Publisher Elsevier
Language eng
Subject 020303 Fluid Physics
Abstract This paper reports a systematic investigation of the effect of nozzle aspect ratio (AR) on plane jets. The aspect ratio AR (≡ w/h, where h and w are the nozzle height and width) was varied from 15 to 72. The present velocity measurements were performed using single hot-wire anemometry, over a downstream distance of up to 85h and at a nozzle-height-based Reynolds number of Reh = 1.80 × 104. Results obtained reveal that both the extent and character of statistical two-dimensionality of a plane jet depend significantly on AR. Most aspects of the near field flow exhibit an asymptotic-like dependence on AR, but do not become independent of AR within the range of AR investigated. A region of statistically two-dimensional (2-D) mean velocity field is achieved only for AR greater-or-equal, slanted 20, and its axial extent increases with AR. However, the centerline turbulence intensity in the far field displays an asymptotic-like convergence only for AR greater-or-equal, slanted 30. In the self-similar region, both the mean decay and spreading rates of the jet increase as AR increases and do not reach an asymptotic value, even at AR = 72. The aspect ratio of the local jet (w/local velocity half-width) at the end of the 2-D region becomes asymptotically independent of nozzle aspect ratio, for approximately AR greater-or-equal, slanted 30. That is, the plane jet ceases to be statistically 2-D at a fixed value of local jet aspect ratio for nozzle aspect ratios greater than 30. The skewness and flatness factors also depend on AR. These results imply that independence of AR, even in the near field, will require very much larger aspect ratios than have been investigated previously.
Keyword Plane jet
Turbulent mixing
Effect of nozzle aspect ratio
Hot-wire measurement
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Document type: Journal Article
Sub-type: Article (original research)
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Created: Wed, 28 Jan 2009, 10:40:09 EST by Marianne Steentsma on behalf of Faculty of Science