NUMERICAL AND EXPERIMENTAL-DETERMINATION OF IONIZING FRONT VELOCITY IN A DC POINT-TO-PLANE CORONA DISCHARGE

The present work is devoted to the comparison between numerical and ex perimental determination of the velocity profile of an ionizing front (primary streamer) in a DC positive point-to-plane corona discharge in dry air at atmospheric pressure. The inception and propagation of the ionizing front is simulated by a one-dimensional model, using finite differences in a flux-corrected transport numerical scheme, including gamma-effects, and using experimental results concerning the swarm par ameters. This model provides the spatio-temporal local field and charg e density variations as well as the ionization front velocity. An opti cal measurement of the velocity is performed with the same discharge p arameters, using a photomultiplier and a single-slit device. The techn ique is based on the experimental fact that, for a 1 cm gap in the 7-9 kV voltage range, the successive primary streamers corresponding to a given gap voltage display identical velocity profiles. As a result of the comparison, it appears that a precise coupling between simulation and experiment is possible. There is a voltage range (8-9 kV) within which good agreement is observed. The front velocity in most of the ga p is about 2 x 10(7) cm s(-1) and the profile presents an increase whe n the streamer leaves the point electrode and when it reaches the cath ode. The possible mechanisms of these accelerations are discussed. The model may be applied to a large variation range for various parameter s such as the nature of the gas, pressure, inter-electrode gap and cur vature radius of the active electrode.