Oscillating and star-shaped drops levitated by an airflow

Wilco Bouwhuis, Koen G. Winkels, Ivo R. Peters, Philippe Brunet, Devaraj van der Meer, Jacco H. Snoeijer

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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
Original languageEnglish
Article number023017
Number of pages11
JournalPhysical review E: Statistical, nonlinear, and soft matter physics
Volume88
Issue number2
DOIs
Publication statusPublished - 2013

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Star
stars
Flow Rate
flow velocity
Thermal Effects
temperature effects
critical flow
cushions
chimneys
Axisymmetry
Oscillation
drop size
oscillations
potential flow
lubrication
Lubrication
Potential Flow
floating
Rate Constant
Hydrodynamics

Keywords

  • METIS-297237
  • IR-89956

Cite this

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title = "Oscillating and star-shaped drops levitated by an airflow",
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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year = "2013",
doi = "10.1103/PhysRevE.88.023017",
language = "English",
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journal = "Physical review E: covering statistical, nonlinear, biological, and soft matter physics",
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Oscillating and star-shaped drops levitated by an airflow. / Bouwhuis, Wilco; Winkels, Koen G.; Peters, Ivo R.; Brunet, Philippe; van der Meer, Devaraj; Snoeijer, Jacco H.

In: Physical review E: Statistical, nonlinear, and soft matter physics, Vol. 88, No. 2, 023017, 2013.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Oscillating and star-shaped drops levitated by an airflow

AU - Bouwhuis, Wilco

AU - Winkels, Koen G.

AU - Peters, Ivo R.

AU - Brunet, Philippe

AU - van der Meer, Devaraj

AU - Snoeijer, Jacco H.

PY - 2013

Y1 - 2013

N2 - 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

AB - 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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KW - IR-89956

U2 - 10.1103/PhysRevE.88.023017

DO - 10.1103/PhysRevE.88.023017

M3 - Article

VL - 88

JO - Physical review E: covering statistical, nonlinear, biological, and soft matter physics

JF - Physical review E: covering statistical, nonlinear, biological, and soft matter physics

SN - 2470-0045

IS - 2

M1 - 023017

ER -