Intermittency Measurements in a Turbulent Plasma Jet.

Abstract : Measurements of the distribution of the intermittency factor and the front crossing frequencies have been performed on a turbulent argon plasma jet. The work had the dual objective of checking turbulent front statistics under conditions of extreme compressibility and of comparing these statistics as obtained by probes sensitive to gas temperature on one hand, and to electron density on the other. The mean front position and its standard deviation were found to grow linearly with distance; in the context of the former, the jet was wider, as expected, than jets with little or no enthalpy excess. The front position probability was normally distributed about its mean. The front wavelength computed from the zero-frequency measurements was found to tend asymptotically to about 9 times the transverse jet scale. Within the experimental error these statistics as measured for the gas temperature were found identical to those measured with an electron sensor. Since the jet appeared to be self-preserving dynamically, these results can be generalized. (Author)