Bubble Dynamics and Interface Phenomena

Volume 23 of the series Fluid Mechanics and Its Applications pp 343-353

Response of bubbles to ultrasonic radiation pressure: Dynamics in low gravity and shape oscillations

  • Philip L. MarstonAffiliated withDepartment of Physics, Washington State University
  • , Eugene H. TrinhAffiliated withMS 183-401, Jet Propulsion Laboratory
  • , Jon DepewAffiliated withMS 183-401, Jet Propulsion Laboratory
  • , Thomas J. AsakiAffiliated withDepartment of Physics, Washington State University

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A dual-frequency acoustic levitator containing water was developed for studying bubble and drop dynamics in low gravity. It was flown on the Space Shuttle on USML-1 where it was used in NASA’s Glovebox facility. High frequency (21 or 63 kHz) ultrasonic waves were modulated by low frequencies to excite shape oscillations on bubbles and oil drops ultrasonically trapped in the water. Bubble diameters were typically close to 1 cm or larger. When such large bubbles are acoustically trapped on the earth, the acoustic radiation pressure needed to overcome buoyancy tends to shift the natural frequency for quadrupole (n = 2) oscillations above the prediction of Lamb’s equation. In low gravity, a much weaker trapping force was used and measurements of n = 2 and 3 mode frequencies were closer to the ideal case. Other video observations in low gravity include: (i) the transient reappearance of a bulge where a small bubble has coalesced with a large one, (ii) observations of the dynamics of bubbles coated by oil indicating that shape oscillations can shift a coated bubble away from the oil-water interface of the coating giving a centering of the core, and (iii) the agglomeration of bubbles induced by the sound field.

Key words

bubbles shape oscillations radiation pressure low gravity