Effects of fluid flow on the characteristics of an atmospheric pressure low temperature plasma jet

Summary form only given. Recently interest in low temperature atmospheric pressure plasma jets has increased due to their unique capabilities and novel applications, such as biomedicine. Prior experimental results showed that low temperature plasma jets are in fact trains of plasma bullets/packets traveling at supersonic velocities. This is especially interesting because the plasma bullets travel in a region free of any external electric field. Although Lu and Laroussi explained this phenomenon by photoionization, how the bullets form and how they reach such high velocities are still not well-understood issues. Additionally, some properties of the plasma jets, such as the plasma plume length, homogeneity, bullet´s shape etc., are directly affected by the fluid flow, the geometry of the electrodes, and the characteristics of the applied high voltage pulse. In this paper, the fluid dynamics and electrostatic simulations of the plasma pencil are performed by a commercially available, partial differential equation solver based on finite element method. We found that if the fluid velocity value is more than 10 m/s, the plasma plume starts to fluctuate and becomes unstable. In addition, the length and homogeneity of the plasma plume are directly related to the applied high voltage (magnitude and pulse width) and the fluid velocity values. These numerical simulations contribute some insights for future theoretical explanations and allow us to determine the optimum operation conditions of the plasma pencil.