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Oscillating and star-shaped drops levitated by an air-flow

Oscillating and star-shaped drops levitated by an air-flow
Oscillating and star-shaped drops levitated by an air-flow
We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking of axisymmetry and the appearance of “star drops”. This is strongly reminiscent of the Leidenfrost stars that are observed for drops floating above a hot substrate. The key advantage of this work is that we inject the airflow at a constant rate below the drop, thus eliminating thermal effects and allowing for a better control of the flow rate. We perform experiments with drops of different viscosities and observe stable states, oscillations, and chimney instabilities. We find that for a given drop size the instability appears above a critical flow rate, where the latter is largest for small drops. All these observations are reproduced by numerical simulations, where we treat the drop using potential flow and the gas as a viscous lubrication layer. Qualitatively, the onset of instability agrees with the experimental results, although the typical flow rates are too large by a factor 10. Our results demonstrate that thermal effects are not important for the formation of star drops and strongly suggest a purely hydrodynamic mechanism for the formation of Leidenfrost stars.
0899-8213
1-11
Bouwhuis, Wilco
43b6aadf-38c9-4be4-9720-568002883392
Winkels, Koen G.
f52651df-1bfd-491b-9bc1-958bb08163c8
Peters, Ivo
222d846e-e620-4017-84cb-099b14ff2d75
Brunet, Phillipe
e7ce6bd2-b886-43f3-9f8e-d7ff031c26a1
van der Meer, Devaraj
54e00557-0050-43f5-9efb-a28ea962591c
Snoeiker, Jaco H.
5049c80b-6ea0-4e4d-aa3d-2d6523cfc5cb
Bouwhuis, Wilco
43b6aadf-38c9-4be4-9720-568002883392
Winkels, Koen G.
f52651df-1bfd-491b-9bc1-958bb08163c8
Peters, Ivo
222d846e-e620-4017-84cb-099b14ff2d75
Brunet, Phillipe
e7ce6bd2-b886-43f3-9f8e-d7ff031c26a1
van der Meer, Devaraj
54e00557-0050-43f5-9efb-a28ea962591c
Snoeiker, Jaco H.
5049c80b-6ea0-4e4d-aa3d-2d6523cfc5cb

Bouwhuis, Wilco, Winkels, Koen G., Peters, Ivo, Brunet, Phillipe, van der Meer, Devaraj and Snoeiker, Jaco H. (2013) Oscillating and star-shaped drops levitated by an air-flow. Physics of Fluids A: Fluid Dynamics, 88 (23017), 1-11. (doi:10.1103/physreve.88.023017).

Record type: Article

Abstract

We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking of axisymmetry and the appearance of “star drops”. This is strongly reminiscent of the Leidenfrost stars that are observed for drops floating above a hot substrate. The key advantage of this work is that we inject the airflow at a constant rate below the drop, thus eliminating thermal effects and allowing for a better control of the flow rate. We perform experiments with drops of different viscosities and observe stable states, oscillations, and chimney instabilities. We find that for a given drop size the instability appears above a critical flow rate, where the latter is largest for small drops. All these observations are reproduced by numerical simulations, where we treat the drop using potential flow and the gas as a viscous lubrication layer. Qualitatively, the onset of instability agrees with the experimental results, although the typical flow rates are too large by a factor 10. Our results demonstrate that thermal effects are not important for the formation of star drops and strongly suggest a purely hydrodynamic mechanism for the formation of Leidenfrost stars.

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More information

Accepted/In Press date: 27 May 2013
Published date: 19 August 2013
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 399962
URI: http://eprints.soton.ac.uk/id/eprint/399962
ISSN: 0899-8213
PURE UUID: 83f7cb6e-0216-4ad5-a24a-4a5ead06e898
ORCID for Ivo Peters: ORCID iD orcid.org/0000-0002-3549-3322

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Date deposited: 08 Sep 2016 15:39
Last modified: 22 Nov 2021 03:08

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Contributors

Author: Wilco Bouwhuis
Author: Koen G. Winkels
Author: Ivo Peters ORCID iD
Author: Phillipe Brunet
Author: Devaraj van der Meer
Author: Jaco H. Snoeiker

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