Experimental study on the bubble-droplet chain process by using the world fastest high-speed video camera

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Gas transfer at sea surfaces is strongly dominated by disturbances close to the surface. White cap, which appear on the ocean surfaces when wind waves are breaking, is one of the most important processes in the gas transfer mechanisms. In the white caps, many bubbles are entrained into sea water and some of them are lifted up to surface. The bubbles at sea surfaces eventually burst and generate many small droplets. Similarly, some of the droplet fall down to sea surface again. This bubble-droplet chain process was experimentally investigated in this research.A high-speed video camera, of which frame rate is 1,000,000 fps, was developed at Kinki University in 2001. The high-speed video camera is a powerful tool for investigation of the gas transfer at sea surface. In this research, this high-speed video camera was applied to visualization of the fundamental processes of the bubble-droplets chain process. The following processes are picked up as the fundamental processes.(1)Air entrapment under an impacting drop(2)Coalescence speed of two drops(3)Coalescence speed of two bubbles(4)Crown-breakup by the formation of Marangoni holesAnd also the simultaneous plane measurement techniques of air and water flows close to wind wave interfaces was developed by using a Particle Tracking Velocimetry, which was developed at Kinki University.