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An extension to the universal time scale for vortex ring formation

Published online by Cambridge University Press:  12 March 2021

Raphaël Limbourg
Affiliation:
Department of Mechanical Engineering, McGill University, Montréal, QCH3A 0C3, Canada
Jovan Nedić*
Affiliation:
Department of Mechanical Engineering, McGill University, Montréal, QCH3A 0C3, Canada
*
Email address for correspondence: [email protected]

Abstract

The formation of vortex rings emanating from orifices with different orifice-to-tube diameter ratios $D_0/D_p$ is studied using time-resolved particle image velocimetry. The invariants of the motion in their non-dimensional form are computed and presented in the non-dimensional time space $t^*=U_0 t/D_0$, where the subscript 0 refers to the exhaust quantities. The classic slug-flow model is revisited and extended to account for the contraction of the flow when fluid is being pushed out through the orifice. Accordingly, a new time scale in terms of the contracted quantities (subscript $\star$) is defined as $T^*=U_\star t/D_\star$. Results show that the modified slug-flow model unifies the formation number of orifices and straight nozzles with a value of approximately 4.

Type
JFM Papers
Copyright
© The Author(s), 2021. Published by Cambridge University Press

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