Spatial Dynamics of Coherent Structures in a Thermal Plasma Jet

A charge-coupled-device camera was used to record optical radiation of a thermal plasma jet from two perpendicular directions. The reconstruction procedure based on the inverse Radon transform yielded the complete 3-D distribution of the optical emission in the plasma jet. The differences between the resulting 3-D matrices representing the optical intensities derived from adjacent pictures in the recorded series were used for the identification of coherent structures as regions characterized by the temporal increase or decrease of the optical emission. The occurrence and the evolution of coherent structures indicate turbulent phenomena in the plasma jet and depend on the flow conditions.