The impact of swirl on a starting vortex from an impulse jet identified in PIV data

In diffusion-limited laminar jet flows, momentum and heat transfer can be enhanced through the addition of swirl or toroidal vortices. This study utilizes Stereoscopic Particle Image Velocimetry (Stereo-PIV) to investigate the properties of a toroidal starting vortex generated by a pulsatile jet. A key focus is the modification of vortex topology via swirl, induced by 3D-printed nozzles with internal vanes. Vortex cores are identified and characterized using a Combinatorial Vortex Detection (CVD) algorithm. To ensure methodological robustness, the study analyzes how PIV data characteristics and processing schemes influence the accuracy of the CVD algorithm. The overall goal is to compare experimental results against theoretical predictions to identify the vortex models that best characterize the vortical structures in these flows.