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research-article

New understanding of mode switching in the fluidic precessing jet flow

[+] Author and Article Information
Xiao Chen

School of Mechanical Engineering Centre for Energy Technology (CET) The University of Adelaide Adelaide, South Australia, 5005 Australia
xiao.chen01@adelaide.edu.au

Zhao F. Tian

School of Mechanical Engineering Centre for Energy Technology (CET) The University of Adelaide Adelaide, South Australia, 5005 Australia
zhao.tian@adelaide.edu.au

Richard M. Kelso

School of Mechanical Engineering Centre for Energy Technology (CET) The University of Adelaide Adelaide, South Australia, 5005 Australia
richard.kelso@adelaide.edu.au

Graham J. Nathan

School of Mechanical Engineering Centre for Energy Technology (CET) The University of Adelaide Adelaide, South Australia, 5005 Australia
graham.nathan@adelaide.edu.au

1Corresponding author.

ASME doi:10.1115/1.4036151 History: Received August 15, 2016; Revised February 01, 2017

Abstract

We report the first systematic investigation of the phenomenon of “switching” between the two bi-stable Axial Jet (AJ) and Precessing Jet (PJ) flow modes in the fluidic precessing jet nozzle. While geometric configurations have been identified where the fractional time spent in the AJ mode is much less than that in the PJ mode, nevertheless the phenomenon is undesirable and also remains of fundamental interest. This work was undertaken numerically using unsteady Shear Stress Transport model, the validation of which showed good agreement with the experimental results. Three methods were employed in the current work to trigger the flow to switch from the AJ to the PJ modes. It is found that some asymmetry in either the inlet flow or the initial flow field is necessary to trigger the mode switching, with the time required to switch being dependent on the extent of the asymmetry. The direction and frequency of the precession was found to depend on the direction and intensity of the imposed inlet swirling, which will be conducive to the control of the FPJ flow for related industrial applications and academic research. The process with which the vortex skeleton changes within the chamber is also reported. Furthermore, both the rate of spreading and the maximum axial velocity decay of the jet within the nozzle are found to increase gradually during the switching process from the AJ to the PJ modes, consistent with the increased curvature within the local jet.

Copyright (c) 2017 by ASME
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