乱流境界層中に噴出した気流からの気泡分離機構に関する研究 : 連続気柱からの気泡分離(流体工学,流体機械)

概要

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A theoretical and experimental consideration is conducted to investigate the bubble separation from an air injected into a liquid turbulent boundary layer. There exist three patterns of bubble separation dependent on the jet velocity, i.e., (a) single bubble, (b) ccalescent bubble, and (c) continuous jet. First, the critical jet velocity from (a) to (b) is theoretically estimated from the condition that the jet from the nozzle overtakes the rear end of the separated bubble which shrinks due to the action of surface tension. The calculated results roughly reproduce the experimental results observed by the high-speed video camera. The process of bubble separation from the continuous jet (c) can be classified into two patterns, i.e., (i) the bubble separates from the swell at the front end of jet, (ii) the jet breaks due to the instability on the liquid-gas interface. The separated bubble diameter of pattern (i) is theoretically determined by considering the force balance at the front end of jet between surface tension, drag from the frees stream and virtual mass force. Also the bubble diameter of pattern (ii) is calculated from the most unstable wavelength of Rayleigh instability. Both theoretical results agree well with those obtained experimentally.
社団法人日本機械学会の論文
2009-08-25