Speaker 1 :  James Duncan  (University of Maryland)
    Date & Time : April 29 (Fri.), 2022 / 9:00-10:00AM (Tokyo (JST))
                  (--> April 28 (Thu.), 2022 / 8:00-9:00PM (Maryland (EDT)) )
    Title : An Experimental Study of Droplet Generation by Plunging Breaking Water Waves
    Abstract : 
         The production of droplets by strong, moderate, and weak plunging breakers is 
       studied experimentally in a laboratory. The water waves are generated mechanically 
       using a dispersively focused wave packet technique with an average wave packet 
       frequency of 1.15 Hz for all three waves. Surface profile histories of the breaking 
       wave crests are measured using a cinematic laser-induced fluorescence technique.  
       The temporal evolution of the phase averaged surface profile of the breaker, obtained 
       from 10 runs for each wave, are used to characterize the breakers. Droplets are 
       measured using a cinematic digital in-line holographic system positioned at 
       28 streamwise locations along a horizontal plane (herein called the measurement plane) 
       that is 1 cm above the maximum wave crest height. The droplet radii (≤ 100 μ), 
       positions and trajectories are determined from the holograms. Counting only 
       the droplets that are moving up across the measurement plane, the spatio-temporal 
       distribution of droplet generation by the breakers is obtained. Droplet statistics 
       including total number, mean diameter and speed are presented. The relative importance 
       of the various droplet generation mechanisms in the three waves are discussed and 
       correlated with the mean wave profile characteristics. Planned experiments exploring 
       the effect of wind and surfactants are discussed.
         Joint work with M. A. Erinin, S. D. Wang and X. Liu.

         The support of the Division of Ocean Sciences of the National Science Foundation 
       under grants OCE0751853 and OCE1925060 is gratefully acknowledged.