Validating LES predictions of the flow in a swirl-stabilized plasma torch geometry*

Inductively coupled plasma torches have a variety of industrial and

academic uses, including as a plasma source for testing materials for

ablative thermal protective systems.  However, the performance of

these devices can be sensitive to the driving flow.  In this work, we

report on an effort to characterize the flow in a swirl-stabilized

plasma torch geometry with large eddy simulation and to validate the

simulations against experiments.  The flow is fed by small,

compressible jets that induce a strongly swirling flow.  This flow is

highly turbulent, but shortly above these entrance jets, the flow

becomes essentially incompressible and the initial jet turbulence

decays rapidly.  Because of the large range of both length and

time scales induced by the geometry, the problem is split into two

subproblems to enable efficient simulation and thus, two sets of large

eddy simulations are conducted.  The first simulations characterize

the compressible entrance jets and generate boundary condition data

for the second, which simulate the flow from just above the entrance

jets through the exit of the torch.  Uncertainty in the inlet

conditions for the second simulations are propagated, and validation

comparisons against PIV measurements are shown.