Modeling the plasma jet in the Plasmatron X ICP facility

The objective of this work is to model the plasma jet in the plasmatron X ICP facility, located at the University of Illinois Urbana-Champaign (UIUC) using high-fidelity numerical schemes. The governing equations are solved using a finite volume based fluid solver called hegel, developed at the Center for Hypersonics and Entry Systems Studies (CHESS). The plasma is assumed to be in the state of local thermodynamic equilibrium (LTE). The convective terms are discretized using a combination of non-dissipative central skew-symmetric scheme and a dissipative upwind scheme. This combination is used to achieve appropriate amount of filtering of high frequency scales and dissipation due to the sub-grid scales, hence performing an implicit large eddy simulation (ILES). The validity of the scheme is studied by applying it to Taylor-Green vortex testcase. To replicate no-reflection boundary conditions, sponge regions are added near each boundary by adding source terms to force the flowfield to a target state. The ILES method and sponge boundary zones are applied to simulate a subsonic turbulent jet of Reynolds number 3600 and Mach number 0.9. The sponge zones can be seen to avoid reflections back into the physical domain. Using the same numerical schemes, the plasma jet in plasmatron X ICP facility is simulated. Due to very high translational temperatures in the core compared to the ambient flow (ΔT ≈ 10000 K), a sharp gradient is seen in the density field across the jet shear layer. The high temperatures also cause the transport properties to vary by an order of magnitude within the physical domain. It is seen that the plasma jet dynamics were affected by these significant differences in density and viscosity between the plasma core and the ambient fluid. The cold dense ambient fluid is seen to be periodically entrained into the plasma core.