Absolute instability in plasma jet

Stability features of a plasma jet are investigated by means of Linear StabilityTheory. The convective/absolute nature of the instabilities is determined by local spatio-temporal analyses of the impulse response of the flow for different stream-wise positionsand different operative conditions. Frequencies, shapes and growth rate of the leadingstability mode are compared to available experimental high speed camera recordings of thejet unsteadiness. The frequency range and mode shapes retrieved theoretically are in goodagreement with the experimental results. However, the growth-rates of these modes indicatea fast transition to the turbulent regime which is not observed in the facility, which couldbe explained by non-parallel base flow or non-linear modal growth of the mode effects.