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Air Bubble Measurements using Imaging Technique

Introduction

Despite the fruitful knowledge of air entrainment for wind-wave breaking, a few studies of air entrainment and of surf zone wave breaking exist. The compressibility owing to air-water mixture decreases the velocity of sound and is being used to estimate large-scale prototype impacts, since the usual Froude scaling is unlikely to be corrected for engineering problems. Therefore, the connection between the air-mixture, the bubble distribution and the wave breaking induced turbulence is essential to understand the gas-liquid interaction in the surf zone. Cox and Shin (2001) investigated the dependence of void fraction on the turbulent intensity in the bore region of surf zone waves. The wave breaking induced bubbles in the surf zone are split by the strong local turbulent shear induced by breaking waves at the bubble scale. The authors demonstrated on the dependence of void fraction on wave scale using different scales of wave flume following the Froude similarity law. However, the bubble characteristics and connections between bubble characteristics and wave breaking are not well known owing to the lack of understanding of phenomena in the surf zone. The detail information of the two-phase flow characteristics is required for mathematical modeling.

The purpose of this study is to investigate the characteristics of void fractions, bubble distributions and turbulent properties in the surf zone waves using visualization technique.

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Results

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References

Journal Papers

  1. Watanabe, Y. and N. Mori, Sub-surface vortex measurements in breaking water waves using an infrared imaging technique, Journal of Geophysical Research, Ocean, American Geophysical Union, (10.1029/2006JC003950).
  2. Mori, N. and S. Kakuno (2008) Aeration and bubble measurements of coastal breaking waves, Fluid Dynamics Research, Volume 40, Issues 7-8, pp.616-626. (doi:10.1016/j.fluiddyn.2007.12.013)
  3. Mori, N., T. Suzuki and S. Kakuno (2007) Experimental study of air bubbles and turbulence characteristics in the surf zone, Journal of Geophysical Research, Ocean, American Geophysical Union, Vol.112, C05014, doi:10.1029/2006JC003647

Proceedings

  • Mori, N. and S. Kakuno (2007) Intrusive and Imaging Bubble Measurements of Coastal Breaking Wave, Proceedings of the 1st International Colloquium on Dynamics, Physics and Chemistry of Bubbles and Gas-Liquid Boundaries, Niseko, Japan, CD-ROM, 10p.
  • Kashima, H., N. Mori and S. Kakuno (2006) Air bubble measurements of the surf zone breaking waves by bubble tracking velocimetry, Proceedings of the 30th International Conference on Coastal Engineering, ASCE.