Abstract
In this study, a start-up viscoelastic fluid flow in a reservoir upstream a circular pipe entry was visualized by the photochromic method. The photochromic flow visualization technique is based on a photo-chemical reaction where a chemical material, C_<19>H_<18>N_2O_3(SP-1), turns into purple-colored by shining ultra-violet laser light for a few minutes. Among many visualization techniques, the photochromic technique applied in this work has a dominant advantage in that it needs no contaminant such as die or tracer particles which may affect the velocity and stress field. It also allows very free arrangement of initial patterns by designing the fading screen and repetitive use of a same test fluid.
