140 円管内における高粘度気泡流のレオロジー(S34-4 複雑流体の流れとその応用(4),S34 複雑流体の流れとその応用)  [in Japanese] 140 Rheology of Highly Viscous Bubbly Flow in a Pipe  [in Japanese]

Deformation of a gas bubble in a highly viscous pipe flow was investigated experimentally. The pipe flow is generated in a vertical transparent tube by the pressure difference between both ends of the tube. The deformation was recorded by high-speed photography. The velocity field of liquid flow was measured by Particle Image Velocimetry-Laser Induced Fluorescence (PIV-LIF). Two materials, polysaccharide (Hayashibara Pullulan) water mixture and silicone oil (Shin-etsu KF96H) were used as the test liquids. The steady bubble shapes and orientations were correlated with the capillary number Ca. The experimental data were compared with a theoretical prediction in a simple shear flow. The small deformation is predicted well with the theory for the simple shear. At higher capillary number, the deformation is different from that in a simple shear flow, because the nonuniformity of shear rate in the pipe is a substantial effect on the bubble shape.