Mixing characteristics of a film-exciting flapping jet

Wu, M. and Xu, M. and Mi, J. and Deo, R. C. ORCID: https://orcid.org/0000-0002-2290-6749 (2020) Mixing characteristics of a film-exciting flapping jet. International Journal of Heat and Fluid Flow, 82 (Article 108532). pp. 1-9. ISSN 0142-727X


Abstract

We have recently discovered a new type of self-excited flapping jets due to a flexible film whose leading edge is fixed at the nozzle exit [Exp Ther Fluid Sci, 106, 226-233]. This paper is to report the experimental investigation on mixing characteristics of the jet induced by a rectangular FEP film. Hot wire anemometry and flow visualization are used to examine the flapping jet flow versus the non-flapping counterpart. Experiments are conducted under the following conditions: i.e., L/D = 1.0 (fixed), W/D = 0.03 ~ 1.0 (varying) and Re = 10000 ~ 45000 (varying); where W and L are the film's width and length, D is the nozzle-exit diameter, and Re is the Reynolds number defined by Re UoD/ν with Uo and ν being the jet-exit velocity and fluid viscosity.

It is found that the jet-flapping frequency fF varies with W in a complex fashion while it grows roughly linearly with increasing Uo for W/D ≥ 0.5. The flapping Strouhal number StF fFD/Uo ranges in 0.13 ≤ StF ≤ 0.23 for Re = 15,000 ~ 45,000. These Strouhal numbers are substantially lower than that (≈ 0.45 ~ 0.7) for the primary vortex generation in the free jet, but one to two orders of magnitude higher than those from the conventional self-exciting fluidic devices. In general, the flapping jet decays and spreads more rapidly than does the free jet. As W increases, the decaying and spreading rates both grow. Of significance, the centerline evolutions of Taylor and Kolmogorov scales versus the integral scale are examined to characterize the small scales of turbulence against the large-scale motion.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Sciences (6 Sept 2019 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Sciences (6 Sept 2019 -)
Date Deposited: 30 Jan 2020 23:33
Last Modified: 08 May 2020 01:47
Uncontrolled Keywords: Film flutter; Flapping jet; Self-excited nozzle; Turbulent mixing
Fields of Research (2008): 09 Engineering > 0915 Interdisciplinary Engineering > 091504 Fluidisation and Fluid Mechanics
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
Identification Number or DOI: 10.1016/j.ijheatfluidflow.2019.108532
URI: http://eprints.usq.edu.au/id/eprint/37645

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