Time-dependent 3D simulation of an argon RF inductively coupled thermal plasma

A time-dependent 3D numerical simulation using a large eddy simulation approach is conducted to meet the first challenge in revealing the coherent vortex structure and dynamic behaviours of the thermofluid field in a radio-frequency inductively coupled thermal plasma torch. The high-temperature plasma region exhibits unsteady behaviour near the coil. At the same time, the high- and low-temperature flows form undulating interfaces. The flow field has a complicated 3D structure with a recirculating zone due to Lorentz forces. Because of the recirculating flow, the injected cold gas tends to avoid the high-temperature plasma region. The largest vortex structure, at approximately 10 000 K, remains in the plasma region, whereas small cold eddies are generated near the top wall of the torch and transported downstream, avoiding the plasma region. In the intermediate-temperature regions around the plasma, relatively large vortices are repeatedly born and dissolve, connecting with and separating from each other. Most of them have non-uniform temperatures because they are easily generated in the interfacial regions with temperature gradients around a thermal plasma flow. The time scale of the transport of cold eddies is much smaller than that of the dynamic motion of the high-temperature plasma region.