Growth rates of viscoelastic vortex rings

Abstract

In this research, experimental studies were performed to investigate the mechanisms of vortex ring formation in a viscoelastic solution of CPyCl/NaSal [100:60] mM in distilled water. We used 2-dimensional particle image velocimetry (PIV) to characterize the transition from laminar to unstable regimes in a cylindrical oscillatory pipe ow, for a constant frequency of 5 Hz. Mea- surements reveal that the activation time of the vortex rings shows a dramatic dependence with the forcing amplitude, in contrast with the development time of the vortex rings, which seems to be independent of the forcing amplitude and remains constant with a value of 1.9 0.5 s.