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Progress in Plasma Processing of Materials, 2003

ISBN:
978-1-56700-192-1 (Print)
978-1-56700-447-2 (Online)

IDENTIFICATION OF DYNAMIC PATTERNS IN CCD CAMERA RECORDS OF THERMAL PLASMA JETS

V. Nenicka
Institute of Electrical Engineering, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 02 Praha 8, Czech Republic

J. Hlina
Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 00 Praha 8, Czech Republic

J. Sonsky
Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejskova 5, 182 00 Praha 8, Czech Republic

Abstract

A fast CCD camera was used to acquire series of pictures of argon plasma jet generated by an arc heater operating with various gas flow rates. Each picture series contained 8 pictures of the plasma jet taken with the interval 10 μs and exposure time 1 μs. The evaluation procedure was based on the correlation analysis of vectors the components of which were defined either as intensities of the same pixels in the succeeding pictures or the intensities recorded by the pixels in the neighbourhood of each point of the plasma jet image. The results show that the images of plasma jets include regions characterised by various correlation between the succeeding images of the plasma jet. It is possible to identify both the regions where the correlation is very high (the value of the correlation coefficient close to +1) and the regions related probably to turbulent structures characterised by the negative correlation coefficients close to −1. The evolution and advancement of these structures are strongly influenced by the gas flow rate and arc current.