Vortex ring evolution in an impulsively started jet using digital particle image velocimetry and continuous wavelet analysis

Digital particle image velocimetry and wavelet analysis are combined in this work in order to study the characteristics of the leading vortex ring generated in an impulsively starting jet flow. The wavelet analysis allows one, by virtue of its properties of selectivity in space and scale, to detect coherent structures and to compute their position and size and, through further processing, their convection velocity and circulation. It has been observed that the energy of the leading vortex ring continuously increases even after it has pinched off from the jet shear layer generating it.