A 2-FLUID MODEL OF TURBULENCE FOR A THERMAL PLASMA-JET

In this paper, a turbulent argon plasma jet issuing into a stagnant ar gon environment at 1 atm is studied by applying a two-fluid turbulence model, in order to advance our understanding of thermal plasma jets. The mathematical model has some similarities to the models of two-phas e flows, so that the turbulent plasma jet is treated as a two-phase mi xture. The governing equations include the transport equations for mas s, momentum, and energy for two different fluid parcels (in-moving par cels and out-moving parcels). Auxiliary relations that govern the phys ical phenomena of the interfluid mass, momentum, and energy exchange a re presented together with a description of the mechanisms that contro l the growth or diminution of the fragment size. The results are prese nted in conditional- and unconditional-averaged forms and compared wit h experimental results from enthalpy-probe measurements. A well-known nondimensional form (a Gaussian error function) can represent the radi al distributions of the measured- and predicted-unconditional mean axi al velocity and temperature in consecutive sections (20-45 mm from the nozzle exit). Further insight into the behavior of turbulent plasma j ets can be gained by looking at the conditional fluid properties. The results show that this model can predict phenomena that escape more co nventional models, e.g., the unmixing phenomenon.