Power numbers, Taylor numbers and Taylor vortices in viscous newtonian and non-newtonian fluids

Abstract

Power numbers ( Po) as a function of Taylor numbers ( Ta) have been investigated for the flow between concentric cylinders with the inner cylinder rotating and the outer cylinder stationary. Both Newtonian and non-Newtonian fluids were used and torque measurement was done by strain gauges. Flow visualization enabled Taylor vortices to be studied too. Three pairs of cylinders were used: two plain and one where the outer cylinder had vertical strip baffles. The nominal outer dimensions were 0.1 m diameter × 0.2 m high. The maximum values of Ta measured were 90 for width of gap ( d)/inner cylinder radius ( R i) ratio = 0.9 and approximately 400 for d/R i = 0.7. Experimental data for all the systems used agreed well with theory in the laminar region ( Ta< Ta c), giving Po ∝ Ta −1. For the laminar Taylor vortex region ( Ta> Ta c), ▪. In the latter case, the laminar shear rate was used to calculate the Taylor number for the non-Newtonian fluids. Critical Taylor number Ta c for non-Newtonian fluids was found to be greater than the Newtonian one. The results are useful for estimating the power consumption of potential industrial devices utilizing the advantages of laminar Taylor vortex flow.