Void fraction estimation using a simple combined wave gauge system under breaking waves

Byoungjoon Na, Sangyoung Son

Research output: Contribution to journalArticlepeer-review


In this study, a unique experimental technique that is capable of quantifying void fraction under two-phase air-water flows based on simple combined resistance and capacitance wave gauge system is described and the subsequent applications are discussed. The technique is validated under various surf-zone breaking waves of different wave periods and wave heights in the 2-dimensional wave flume. The difference in the measured surface elevations by capacitance and resistance wave gauges is positively linked to the depth of aeration and depth-averaged void fraction, that is validated by the corresponding images. The measured depth-averaged void fraction at the passage of the air cavity formed by the overturning jet after breaking showed a distinct pattern in regular and cnoidal waves which is attributed to different amount of droplets generated during the jet-curling process. Based on wavelet analysis, the peak frequency-wave continuously spreads its energy to its super-harmonic components due to shoaling while instantaneous spreads of wave energy to the higher harmonics are superposed due to breaking and subsequent jet-overturning. Considering void fraction, a sharper decay of wave energy within the intensely aerated region immediately after breaking is observed and the dissipated energy is reduced as the wave steepness increases following an exponential decay.

Original languageEnglish
Article number110059
JournalOcean Engineering
Publication statusPublished - 2021 Dec 1


  • Breaking wave
  • Capacitance-type wave gauge
  • Energy dissipation
  • Resistance-type wave gauge
  • Void fraction

ASJC Scopus subject areas

  • Environmental Engineering
  • Ocean Engineering


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