抄録
It is necessary to consider both relaxation time and viscosity for investigating viscoelastic flow. Polyethylene flow from a reservoir into a slit at low Reynolds numbers has been visually observed to investigate the flow patterns.
The results of this study are as follows:
When Reynolds number is smaller than 1, circulating secondary flow appears or disappears depending upon the conditions of the main flow and of the characteristics of melted polymers.
The liquid having longer rexation time has a lower critical deformation velocity at which the circulating secondary flow occurs in the reservoir. The region of circulating secondary flow spreads out as the deformation velocity becomes higher. Although the slit entry angle changes, the patterns of main flow into the slit hardly change. In regard to the liquid having shorter relaxation time, irregular and unstable flow occurs at the inlet region of the slit before the circulating secondary flow appears.
