Non-Newtonian Flow Stability in a Heated Pipe at Low Reynolds Numbers

Abstract

The stability of non-Newtonian flow with respect to small disturbances was studied at low Reynolds numbers from 3 to 1 00 for two low viscosity pseudoplastic aqueous Polyox solutions flowing upward in a vertical pipe having a constant flux heat transfer section 251 diameters long. The flow fields were distorted from their isothermal shape because of variations in fluid density and viscosity over the cross section of the pipe. For experimental conditions where the distorted flows approached a fully developed state, transition was observed when the ratio of Grashof to Reynolds number exceeded a critical value, indicating a relationship between transition and velocity profile distortion which is consistent with theoretical stability predictions.