Generation of Reverse Flow of Viscoelastic Fluid Upstream of Re-Entrant Corner in Two-Dimensional L-Shaped Channel

Abstract

Viscoelastic flows are experimentally studied using two-dimensional L-shaped channels. Velocity and pressure distributions have been measured for various Reynolds numbers and for various channel widths on the downstream side in order to clarify the cause and the conditions under which the reverse flow is generated upstream of the re-entrant corner. The present experiment shows that the reverse flow is largest in size when the Reynolds number is nearly equal to unity and the channel width downstream of the re-entrant corner is a quarter of that upstream of it. Pressure distributions on the channel wall rise in the flow direction in the upstream vicinity of the re-entrant corner. This pressure rise takes the maximum in value and in extent under the same conditions as the reverse flow. It is considered that the normal stress effect, peculiar to viscoelastic fluids, causes the generation of the reverse flow and the pressure rise upstream of the re-entrant corner.