The jet-stream channels of gas and plasma in atmospheric-pressure plasma jets

• Published in: Journal of the Korean Physical Society Vol. 69; no. 4; pp. 525 - 535
• Main Authors: Cho, Guangsup, Kim, Yunjung, Uhm, Han Sup
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01-08-2016; Springer Nature B.V; 한국물리학회
• Subjects: Equilibrium flow; Fluid dynamics; Fluid flow; Gas flow; Gas streams; Gases; Incompressible flow; Jet nozzles; Mathematical and Computational Physics; Neutral gases; Particle and Nuclear Physics; Physics; Physics and Astronomy; Plasma; Plasma jets; Reynolds number; Shear stress; Theoretical; 물리학; Plasma; Plasma jet; Reynolds number; Stream channel; Discharge
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.69.525

A solution to the fluid momentum equation for incompressible steady-state flow is obtained for the streams of gas and plasma inside a jet nozzle and in the open-air space. Three pressure forces are considered in the equation. The first is the pressure force of the shear stress resulting from the flow viscosity and is balanced against the second pressure force of the gas stream that is ejected into the air. The third pressure force is due to the radial expansion of the fluid channel, reducing the velocity of the fluid to zero so that we obtain the reaching distance of the fluid after ejection from the nozzle. From the solution for the fluid channel, the regional profile and the density profile of the plasma flow are also determined. The maximum distance of the gas flow with a critical Reynolds number of
R
nc
≈ 2000 is calculated to be 100 times that of the nozzle diameter for Ar, Ne, and He. Because the radial expansion of the plasma is ten times larger than that of neutral gases, the length of the plasma flume is a few tens of the nozzle diameter, which is significantly shorter than the gas flow distance. In the experiments, the maximum length of the plasma plume increases and then saturates as the operation voltage increases.