Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4995600 | Journal of Non-Newtonian Fluid Mechanics | 2017 | 25 Pages |
Abstract
When a polymer solution is sheared between concentric cylinders, with the inner rotating and the outer fixed, the torque on the inner cylinder is modified compared to a Newtonian fluid of the same viscosity revealing the different flow patterns that emerge above the linear stability threshold for circular Couette flow. Here, mixtures of relatively short and long linear polymers in dilute and semi-dilute concentrations were considered. Their shear viscosity and extensional relaxation time are quantified. The stability of the flow is monitored through torque measurements and flow visualisations for a constant rate of acceleration and deceleration of the inner cylinder in a wide range of polymer concentrations. The torque exhibits an hysteretic behaviour, typical of subcritical transition. For large concentrations, six different numbers of steady solitary pairs of vortices, called diwhirls, were observed depending on the deceleration rate and their torque contribution is reported.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
Borja MartÃnez-Arias, Jorge Peixinho,