Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 07, 2019 - November 08, 2019
Clustering of spherical bubbles rising along an inclined flat wall has been investigated experimentally to analyze the bubble-bubble interaction. To avoid bubble coalescence, electrolyte (MgSO4) solution and surfactant (Triton X-100) solution are utilized as a liquid phase. In MgSO4 solution, free-slip boundary condition of bubble surface is maintained, on the other hand, the boundary condition of the surface of rising bubbles in Triton X-100 solution becomes no-slip due to well-know Marangoni effect. The development of the bubble clusters and the bubble-bubble interaction of two, three or four bubbles are discussed through the quantitative evaluation of the bubble velocities and the distance between neighboring bubbles. The bubbles tend to be arranged horizontally as they rise, which induces bubble cluster formation. When two bubbles are arranged vertically, a trailing bubble is accelerated by the wake of a leading bubble. After this stage, these two bubbles take side-by-side arrangement. In the development of bubble clusters, the horizontally aligned bubbles tend to rise more stably in case of the no-slip condition. The drag coefficient increases with increasing number of horizontally aligned bubbles. The decrease in the rising velocity becomes less in the case of no-slip condition. The distance between neighboring bubbles also decreases with increase in the number of horizontally aligned bubbles, and this distance tends to be larger in case of no-slip condition.
