Atmospheric Pressure Plasma Acoustic Moment Analysis
Victor J. Law
Dublin City University
National Centre for Plasma Science and Technology
Collins Avenue, Glasnevin, Dublin 9, Dublin, Ireland
Feidhlim T. O'Neill
Denis P. Dowling
School of Electrical, Electronic, and Mechanical Engineering
University College Dublin
Belfield, Dublin 4, Ireland
Abstract
Low-order moment around the mean (mean, standard deviation, and skewness) analysis of the time evolution of specific acoustic intensities of an air atmospheric pressure plasma jet is performed as a function of nozzle-to-surface gap (0.5 to 7 cm), drive frequency (19, 22, and 25 kHz), and air flow rate (35.7 to 76.6 l/m). The probability distribution of each time-series dataset exhibits deterministic correlations with contrasting entropy process regions in the afterglow (blown arc process (gap = 0.5 cm and 1740 ±100 K); and gap = 1 to 7 cm and 300 to 400 K)). The results indicate that the heated air is channeled along the surface and has a preferred backscatter angular. In addition, the blown arc process exhibits a skewness of +0.055 and the afterglow has skewness values from -0.05 to -0.4. These results illustrate how acoustic information can be used to differentiate plasma-surface entropy states.
