Influence of Polymer Additives on Transitional Plane Poiseuille Flow

Abstract

Transition in dilute polymer solutions was investigated in the same manner as outlined in the previous report for Newtonian fluids. First, we investigated the natural transition arising from a minimum critical Reynolds number. The results suggested that the structural alteration of a turbulent spot resulted in polymer drag reduction. Next, we maintained laminar flow above the minimum critical Reynolds number and visualized the growth of spots artificially created in the laminar flow. The results showed that polymer additives reduce the spreading angle of a spot. Striped streak patterns of ink were observed around the spots. This phenomenon is supposedly caused by the instability of polymer solutions and instability in the background flow.