Anomalous Entry Flow Patterns in the Transition Regime to Global Flow Instability Generated after Vortex Enhancement

概要

論文の詳細を見る
This study is concerned with an origin of entry flow instability generated after vortex enhancement in elastic fluid flows. For this purpose flow visualization experiments of shear-thinning aqueous polymer solution were carried out by means of both tracer-particle method and dye-solution injection technique. Local instability in the salient corner vortex, which was observed as non-smooth particle paths, could evolve to globally unstable entry flow as the Weissenberg number increased. The visualization experiments using the dye-solution injection technique demonstrated that the main cause of the local instability was the occurrence and decay of a dip of the vortex boundary at the lip corner and the small amplitude oscillatory phenomenon of the detachment point had a secondary influence. It was, therefore, concluded that the occurrence of the dip at the lip corner was a trigger of the global entry flow instability after vortex enhancement. However, the mechanism of the occurrence of the dip at the lip corner remains to be an open question, thus it will be necessary to measure the transient velocity field near the lip corner using the LDV or PIV technique.
一般社団法人　日本レオロジー学会の論文