Hydrodynamical simulation of the electric wind generated by successive streamers in a point-to-plane reactor

An electrical corona discharge at atmospheric pressure in positive point-to-plane configuration creates an electric wind from the point to the plane which, within a few seconds, generates an axisymmetrical vortex in a closed cylindrical vessel (ring vortex). A first model for the establishment of this vortex was recently published and our study is an evolution based on an improved physical model. It does not include any empirical time scaling parameter, and takes into account the successive ionizing fronts as a varying electrical force due to the propagation of a sharp electrical field maximum acting on the space charge distribution along the interelectrode gap. After the front propagation (50 ns), the remaining positive ions drift (during 100 μs) in the slowly restoring electric field. Numerical simulations show that the very first streamers and remaining positive ions rapidly push the gas along the very narrow discharge volume, creating a small ring vortex at the cathode around the discharge axis. The following ones have a cumulative effect leading to the enlargement of the vortex. In a few seconds, a quasi-stationary distribution is obtained, which is very close to the experimentally observed steady state. (author)