Observations of the effects of oxide skins on the oscillations of electromagnetically levitated metal droplets
Metals manufacturing and fabrication industries are increasingly using computer-based mathematical models to obtain a better understanding or control of their processes or to predict defects in the final product. The surface tensions of liquid metals can be derived from measurements of the natural oscillation frequencies of levitated drops through the Rayleigh relation, {gamma}=3/8{pi}m{omega}{sup 2}. In general, during terrestrial measurements, a spectrum consisting of three to five dominant oscillation frequencies (in 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. Observation of the frequency spectra and high speed video images of the levitated drops are discussed.
- Research Organization:
- National Physical Lab., Teddington (GB)
- OSTI ID:
- 20005508
- Journal Information:
- International Journal of Thermophysics, Vol. 20, Issue 4; Conference: Fifth International Workshop on Subsecond Thermophysics, Aix-en-Provence (FR), 06/16/1998--06/19/1998; Other Information: PBD: Jul 1999; ISSN 0195-928X
- Country of Publication:
- United States
- Language:
- English
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