Abstract
When strong pressure-oscillation was applied to the two vertically aligned air bubbles in viscoelastic fluids from the bottom side, the lower-bubble rose faster than the upper-bubble. It is thought that a hydrodynamic interaction may be occurred in the fluid between air bubbles. To clarify the stress contribution on the interaction, we tried measuring the retardation profile near and between the vertically aligned small air bubbles under pressure-oscillating fields, by using the flow birefringence technique with CTAB / NaSal solution. In the case of near the bubbles (2μL for each), it was found that the strong retardations by the uniaxial strain between small air bubbles was observed at the time of the air bubbles shrinkage. The biaxial tensile flow was seen in vicinity of small air bubbles when the bubbles expanded.
