Experimental study on vortex rings dynamics in a pulsed jet using Particle Image Velocimetry

In this work, an experimental study on vortex rings dynamics has been performed using digital particle image velocimetry (PIV); in particular, vortex rings at the exit of a circular orifice in a pulsed jet configuration are investigated. The relevance of such a study is related both to the fundamental fluid-mechanics involved in the generation, growing and evolution of vortex rings and simultaneously to the practical applications of the pulsed jet configuration; in particular attention is given to the pulsed jet condition which appears at the outlet of prosthetic heart valves. Different input signals and different stroke volumes have been studied obtaining great differences in the fluid dynamic fields, in particular in the number and in the dynamics of the generated vortices; Reynolds and viscous stresses calculations have been performed. For this particular experimental set-up, results show a great dependency from the input signal imposed at the piston by the linear motor used, both in the waveform, and in stroke volume.