部分回転円板による高分子水溶液の容器内旋回流れにおけるリング渦のPIV計測(流体工学,流体機械)

Abstract

Confined swirling flows of aqueous polymer solutions due to a partially rotating disc in a cylindrical casing have been investigated using a PIV measurement. The ratio of rotating disc radius R_d to container radius R_c, σ=R_d/R_c, was 0.4, 0.6 and 1.0. As the aqueous polymer solution, 0.5wt% polyacrylamide (PAA) solution was used. The fluid within the ring vortex formed near the rotating disc rotates with semi-rigid rotation, where the angular velocity of the ring vortex was about 0.9 times that of the rotating disc. A high shear layer existed at the boundary between the ring vortex and the outer large-scale secondary flow, where the radial and axial distributions of both mean azimuthal and radial velocities were varied significantly. Outside of the high shear layer, both mean azimuthal and radial velocities were very small. In the region outside the ring vortex near the rotating axis, the fluid was slightly flowing in the direction opposite to the rotating disc. These characteristic flow behavior on the ring vortex was independent of σ. It was noted that at σ=0.4 and 0.6, the mean azimuthal velocity at the axial location of the radial-azimuthal section including the ring vortex approached almost zero in the radial direction in the region outside the ring vortex, while at σ=1.0, it has almost the half of the angular velocity of the rotating disc.