Effect of the pressure oscillation frequency on flow interaction among air bubbles by use of the two-dimensional high-speed polarization measurement

Abstract

Application of pressure oscillation enhances rising velocity of tiny bubbles especially for shear thinning viscoelastic fluids. By applying pressure oscillation from the bottom side to three bubbles arranged in a vertical line, we confirmed that the bubble approach others. The reasons of the approaching are investigated using the two-dimensional high-speed polarization camera. In the case of three vertically aligned bubbles, when pressure oscillation is applied from the bottom of the fluid, the lowest bubble may be stressed on the bubble surface than the upper one. It was found that the fluctuation in the bubbles becomes bigger as the surface offset of vibrating piston attached to the rubber sheet of the cell. It was also found that when the offset value increase more than a critical value, the three bubbles fluctuate bigger, and the retardation were observed to bubbles.