摘要： This study presents a unique data set that combines measurements of velocities and void fraction under an unsteady deep water plunging breaker in a laboratory. Flow properties in the aerated crest region of the breaking wave were measured using modified particle image velocimetry (PIV) and bubble image velocimetry (BIV). Results show that the maximum velocity in the plunging breaker reached 1.68C at the first impingement of the overturning water jet with C being the phase speed of the primary breaking wave, while the maximum velocity reached 2.14C at the beginning of the first splash‐up. A similarity profile of void fraction was found in the successive impinging and splash‐up rollers. In the highly foamy splashing roller, the increase of turbulent level and vorticity level were strongly correlated with the increase of void fraction when the range of void fraction was between 0 and 0.4 (from the trough level to approximately the center of the roller). The levels became constant when void fraction was greater than 0.5. The mass flux, momentum flux, kinetic energy, potential energy, and total energy were computed and compared with and without the void fraction being accounted for. The results show that all the mean and turbulence properties related to the air‐water mixture are considerably overestimated unless void fraction is considered. When including the density variation due to the air bubbles, the wave energy dissipated exponentially a short distance after breaking; about 54% and 85% of the total energy dissipated within one and two wavelengths beyond the breaking wave impingement point, respectively. Key Points: First time observing velocity structure experimentally in a plunging breaker First time measuring velocity field and void fraction and showing their relation Estimating mean and turbulence properties with consideration of void fraction 其他題名： J. Geophys. Res. Oceans 出版者： Washington: Blackwell Publishing Ltd 出版日期： 2015-03 出處： Journal of geophysical research. Oceans, 2015-03, Vol.120 (3), p.2007-2049 資源來源： Wiley Online Library Journals 版權： 2015. American Geophysical Union. All Rights Reserved. 識別號： ISSN: 2169-9275 識別號： EISSN: 2169-9291 識別號： DOI: 10.1002/2014JC010269
