International Journal of Thermophysics

, Volume 20, Issue 4, pp 1041–1050

Observations of the Effects of Oxide Skins on the Oscillations of Electromagnetically Levitated Metal Droplets

  • R. F. Brooks
  • A. P. Day

DOI: 10.1023/A:1022642501415

Cite this article as:
Brooks, R.F. & Day, A.P. International Journal of Thermophysics (1999) 20: 1041. doi:10.1023/A:1022642501415


The surface tensions of liquid metals can be derived from measurements of the natural oscillation frequencies of levitated drops through the Rayleigh relation, \(y = \frac{3}{8}\pi m\omega ^2 \) In general, during terrestrial measurements, a spectrum consisting of three to five dominant oscillation frequencies (in the range of 30 to 60 Hz) are found, rather than the single one predicted by Rayleigh, due to deformation of the drop shape by gravity and the supporting magnetic field. Cummings and Blackburn have derived a correction factor to align the measured frequencies with the Rayleigh frequency, which has been shown to hold through micro-gravity experiments by Egry et al., for the majority of metals that have a liquid surface. Work at the NPL on more complex, commercial alloys has found that, in some cases, oscillation frequencies may be split into more complex spectra exhibiting seven to nine oscillation frequencies. This has been attributed to formations of oxide from the metal collecting on the surface of the droplet. Observations of the frequency spectra and high speed video images of the levitated drops are discussed.

high temperature image analysis levitation liquid metal steel surface tension 

Copyright information

© Plenum Publishing Corporation 1999

Authors and Affiliations

  • R. F. Brooks
    • 1
  • A. P. Day
    • 1
  1. 1.Center for Materials Measurement and TechnologyNational Physical LaboratoryTeddington, MiddlesexUnited Kingdom

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