Classification of flow modes of viscoelastic fluids at a junction of two stratified laminar flow layers

Experiments were conducted in order to obtain flow states occurring at a ju nction of two laminar flow layers. In the present study, various combinatio ns of Newtonian and non-Newtonian fluids for two laminar layers were tested in a relatively high-speed stratification process where the inertia of flo w has to be taken into account. From experimental results, flow states at a junction with two different junction angles were classified into 10 flow m odes and these modes were arranged to establish a three-dimensional mode ma p using a generalized Reynolds number and a Deborah number. It was revealed that a mutual relationship among inertial, viscous, and elastic effects is essential for interfacial deformation and instability in the stratified fl ow. It was also shown that the junction angles are important factors in the determination of flow modes appearing in the region of the junction. (C) 1 999 The Society of Rheology. [S0148-6055(99)00306-5].