A systematic investigation of the flow characteristics of atmospheric-pressure air plasma free jet is presented in this study, based on a two-dimensional axisymmetric model developed using magneto-hydrodynamics (MHD). The model fully couples the electromagnetic, thermal, and flow fields, enabling detailed resolution of the multi-physics interactions involved in plasma discharge processes. By incorporating electromagnetic source terms and solving the magnetic vector potential equations, the model provides enhanced accuracy in simulating plasma-induced flow behavior. Vortex structures are identified using a combined analysis of the λ₂ criterion and vorticity, revealing that shear layer instabilities at the nozzle exit initiate the formation and evolution of primary vortices. Spatial distributions of Reynolds stress are shown to correlate strongly with vortex development, indicating a tight coupling between coherent structures and turbulence generation. Furthermore, Dynamic Mode Decomposition (DMD) is employed to extract dominant flow modes and assess their energy contributions. The results demonstrate that low-order modes govern the unsteady jet dynamics, with Mode 1 representing the mean flow structure and Modes 2–4 associated with vortex growth and shear-layer disturbances. These findings provide a theoretical basis for jet control, turbulence modulation, and plasma-assisted engineering applications.
 

Atmospheric-pressure air plasma free jet, flow characteristics, vortex structure, magnetohydrodynamics, dynamic mode decomposition