Vortex Dynamics and Entrainment Mechanisms in Low Reynolds Orifice Jets

Article type: Research Article

Authors: Nastase, I. | Meslem, A.

Affiliations: LEPTAB, University of La Rochelle, av. Michel Crépeau, 17042, La Rochelle, France. E-mail: inastase@univ-lr.fr, and ameslem@univ-lr.fr

Abstract: Classical planar 2D-PIV measurements and time-resolved visualizations enriched by low-level processing are used for the reconstruction of the Kelvin-Helmholtz vortex passing in the near field of a circular and a 6-lobed orifice jet flow. In the circular jet, the entrainment is produced in the braid region, being interrupted in the presence of the Kelvin-Helmholtz ring. The latter compresses the streamwise vortices and alters their self-induction role. Conversely, the 6-lobed orifice geometry allows the cutting of the Kelvin-Helmholtz structures into discontinuous ring segments. Consequently, into these discontinuity regions streamwise large scale structures are developing. These streamwise structures are permanent thus controlling and enhancing the jet entrainment which is not altered by the Kelvin-Helmholtz structures passing.

Keywords: Jet flow, Kelvin-Helmholtz vortex, Streamwise vortex, Image processing

Journal: Journal of Visualization, vol. 11, no. 4, pp. 309-318, 2008