BUBBLE DYNAMICS IN VISCOUS SHEAR FLOWS

摘要

The growth of a gas bubble in a viscous liquid in shear and extensional flows has been studied toward understanding polymer devolatilization. The experimental work was carried out in a Couette apparatus, which operates under vacuum. Air bubbles, which were formed, deformed and grown in a low molecular weight polyisobutylene, were photographed under shear. The experimental growth results indicate that the growth rate of a slender bubble increases as the shear rate increases and as the pressure decreases. These results confirm the existing theory, however they show that simple shear flow is much less efficient than simple extensional flow.