Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 12, 2016 - November 13, 2016
Effect of concentration on flow induced orientational changes of Xanthan gum solutions in a planar channel with an abrupt expansion were examined by measurement of the flow induced birefringence and velocity fields along the centerline. Five kinds of solutions with different concentrations (0.4, 0.45, 0.5, 0.7, 0.9 wt%) were tested in this experiments and relaxation times were evaluated from the G' and G'' curves respectively. Temporal decreases in birefringence were observed just after the abrupt expansion due to the elongational effect. Moreover, longer birefringence changes were observed as the concentration became higher in the downstream regions where the influence of shear was dominant. There was a good relationship between the birefringence changes and the Weissenberg numbers estimated with the relaxation times. From these results, it is clarified that flow induced alignment structure of the polymers after the abrupt expansion was strongly affected by the elongational flow field and the relaxation properties of the polymeric liquids.
