Dynamics of large-scale vortices in non-swirling and swirling turbulent jets. time-resolved tomographic PIV measurements

The paper reports on a parallel study of the dynamics of large-scale vortical structures in non-swirling, low-swirl and high-swirl turbulent jets by means of the time-resolved tomographic PIV technique. 3D realizations of the instantaneous velocity and velocity gradients, local strain and rotation rates, helicity and pressure fluctuations are analyzed. Deformation of the large-scale vortices is studied by evaluating the local stretching/compression rates and local values of the Lamb vector divergence. Linear stability analysis is also applied to the mean velocity profiles in order to identify the most unstable azimuthal modes.