Laminar and Transitional Flow in open channels for non- Newtonian fluids

Abstract

The laminar-turbulent transition for pipelines has been studied intensively and several models are available to predict transition with various degrees of success. Generally the Reynolds number of 2100 is used to describe transition in pipelines. Three smooth rectangular tilting flumes with flow widths of 75, 150 and 300 mm were used to test various concentrations of Kaolin and Bentonite suspensions as well as Carboxymethylcellulose (CMC) solutions. By using the appropriate Reynolds number, all the laminar data could be collapsed onto a standard Moody diagram for water. In laminar flow the friction factor can be predicted for all the materials tested. Transitional behaviour was observed not at one Reynolds number, but over a range. For the higher concentration fluids, transition occurred at lower Reynolds numbers and vice versa. This makes it very difficult to accurately predict the transition of non-Newtonian fluids in open channels.