Impact and lifecycle of superfluid helium drops on a solid surface

Matthew L. Wallace, David Mallin, Michael Milgie, Andres A. Aguirre-Pablo, Kenneth R. Langley, Sigurdur T. Thoroddsen, and Peter Taborek
Phys. Rev. Fluids 5, 093602 – Published 10 September 2020

Abstract

We have used high-speed video and interferometry to investigate the impact, spreading, and eventual contraction of superfluid He4 drops on a sapphire substrate in a saturated atmosphere of helium vapor. We find that the short-term kinetic spreading of superfluid drops (time t<10 ms) is qualitatively similar to both normal helium and conventional fluids at room temperature. In contrast, the contraction phase of the superfluid drops is highly unusual. Superfluid drops survive for only a few seconds on the substrate due to superflow out of the drop into the surrounding helium film. The drop lifetime is strongly dependent on temperature and diverges at the superfluid transition temperature Tλ2.17 K. The contracting drops undergo a geometry-dependent two-phase contraction, which includes a toroidal phase where the radius decreases linearly in time and subsequently a spherical cap phase where the radius decreases with the square root of time. The receding contact angle is temperature dependent and becomes small near Tλ. We also observe that the superfluid outflow causes surprising edge effects, including the emergence of satellite droplets on the perimeter of the expanding drop, as well as ragged and frayed drop edges at lower temperatures.

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  • Received 27 April 2020
  • Accepted 24 July 2020

DOI:https://doi.org/10.1103/PhysRevFluids.5.093602

©2020 American Physical Society

Physics Subject Headings (PhySH)

  1. Physical Systems
Fluid Dynamics

Authors & Affiliations

Matthew L. Wallace1, David Mallin1, Michael Milgie1, Andres A. Aguirre-Pablo2, Kenneth R. Langley2, Sigurdur T. Thoroddsen2, and Peter Taborek1

  • 1Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697, USA
  • 2Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia

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Vol. 5, Iss. 9 — September 2020

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