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

在海面上的气体传输强烈地受到靠近海面的扰动的支配。白色气帽是风浪破碎时海洋表面出现的一种重要的气体输送过程。在白色的海帽中，许多气泡被带入海水中，其中一些气泡被提升到水面。海面上的气泡最终破裂并产生许多小水滴。同样地，一些水滴再次落到海面上。本研究对气泡-液滴链过程进行了实验研究。近畿大学于2001年开发了帧速率为1，000，000 fps的高速摄像机。高速摄像机是研究海面气体输送的有力工具。在这项研究中，这种高速摄像机被应用于可视化的气泡-液滴链过程的基本过程。以下过程被选为基本过程。（1）撞击液滴下的空气滞留（2）两液滴的聚结速度（3）两气泡的聚结速度（4）Marangoni孔的形成导致的冠状破裂（Crown-breakdown）利用近畿大学开发的粒子跟踪测速仪（Particle Tracking Velocimetry），开发了风浪界面附近空气和水流的同时平面测量技术。

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.