Plasma Chemistry and Plasma Processing, Vol.13, No.4, 601-612, 1993
Identification of the Laminar-Turbulent Transition Process in a Plasma Plume
This paper illustrates the complete dynamics of the laminar-turbulent transition process in a plasma plume using a simple measurement of the stagnation-point heatl flux correlated with acoustic, optical, and voltage drop fluctuations. In the laminar flow regime a steady jet is produced and the heal fluxes are accurately predicted by laminar correlations. The initial stage of transition is characterized by the formation of axisymmetric structures and velocity fluctuations which increase the heal flux over laminar correlations. This is followed by a rapid decrease in heal flux as the vortex structures become more intense and rapidly entrain external air into the plume. The plume oscillations (acoustical and voltage drop) become most intense and are identical in frequency at the point of minimum heat flux. The transition is complete which the transition to small-scale turbulence in the exiting boundary layer which results in decreased entrainment and increased heat flux.