2315 Shear thinning性流体からの脱泡における気泡表面での剪断速度評価(S42-4 複雑流体の流動現象(4),S42 複雑流体の流動現象)  [in Japanese] 2315 Evaluation of shear rate along surface of bubbles in removing bubbles from shear-thinning fluids  [in Japanese]

A local shear rate due to a local flow occurred surrounding a small bubble under a periodical oscillating pressure field was derived theoretically, which is able to estimate an enhancement in removing speed of the bubble from shear-thinning fluids. This estimation requires experimental data of changing bubble size over a cyclic period. Because the oscillation frequency was too high to record by video camera, we use a special technique. The pressure inside a closed test cell was controlled by vibrating a thin-film set on the cell. We compared the observed rising velocities under pressure oscillating condition with a velocity that was estimated from the shear viscosity and mean bubble size, which is measured by the special technique. We concluded that the shear-thinning behaviour of the fluid due to the local shear flow in the vicinity of the bubble under periodical oscillating pressure enhances rising velocity itself.