Experimental analysis of time resolved three-dimensional velocity and vorticity fields behind single rising bubbles using Lagrangian particle tracking velocimetry

The present study utilizes highly resolved Lagrange particle tracking measurements to analyze the time-dependent three-dimensional fluid dynamics in the wake of air bubbles rising in quiescent bidistilled water. Two bubble sizes are studied with regard to the velocity fields and the temporal evolution of the generated vorticity in their wakes. The range of bubble sizes is of particular interest, as it corresponds to other recent studies. The bubbles are reconstructed in three dimensions to determine the bubble rise trajectory and the bubble shape. The analysis of the aforementioned measurements, particularly the calculation of the Q-criterion, supports prior numerical findings of a wake mode exhibiting secondary vortex loops. Additionally, the energy spectra of the velocity fields and their temporal evolution are analyzed, providing a unique experimental dataset for the validation of numerical simulations and the further study of bubbly flows.