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Year 2006, Volume 18 / Issue 2

DOI: 10.1615/MultScienTechn.v18.i2

Pages: 92

DOI: 10.1615/MultScienTechn.v18.i2.30

Article price - $45.00

INTERACTION AND COALESCENCE OF BUBBLES IN STAGNANT LIQUID

T. Sanada
Dept. of Mechanical Engineering Science, Kyushu University, Fukuoka, Japan

M. Watanabe
Dept. of Mechanical Engineering Science, Kyushu University, Fukuoka, Japan

T. Fukano
Dept. of Environmental Symbiosis Engineering, Kurume Institute of Technology, Fukuoka, Japan

Interaction effects on the bubble motion and consequently induced coalescence were experimentally studied. A high accuracy bubble production control device enabled us to experiment various spatial configurations of a pair of bubbles. Among them, we focused on the cases where either bubbles rose in vertical line and side by side in silicone oil pool. Bubble diameter and liquid kinematic viscosity were taken as the experimental parameters. The motion of bubbles was recorded by a high-speed video camera. We observed that the Reynolds number Re significantly affected the motion of a pair of bubbles rising in both vertical line and side by side. When a pair of bubbles rose in vertical line, the trailing bubble was attracted by the wake of the leading bubble, and then it collided with leading bubble, in the case of low Re. On the other hand, in the case of intermediate Re, a pair of bubbles kept a mutual equilibrium distance due to the balance between the leading bubble wake attractive force and potential repulsive force. As Re further increased, the trailing bubble deformed and then escaped from the vertical line. When a pair of bubbles rose side by side, they separated from each other as they rose in the case of low Re. On the contrary, in the case of large Re, they attracted each other and then collided if the initial bubble horizontal distance was smaller than a critical value. At the moment of the collision of a pair of bubbles, we did not observe the significant deceleration of the bubble rising velocity. It should be noted that they collided with each other with asymmetric shape deformation. In addition, we investigate the criteria of either bouncing or coalescence of bubbles. Our experimental results show that the approach velocity is important parameter on coalescence of a pair of bubbles.

pages 155-174

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