On the phenomenon of ionic wind induced by corona discharges

This article reviews the latest knowledge on ionic wind generated by two-electrode volume corona discharges in atmospheric air. We aim to accurately describe the ionic wind topology and explain its properties based on experimental measurements and numerical simulations. The two geometric configurations most commonly discussed in this article are the point-plate and point-ring. After an introduction and brief theoretical overview of the physical phenomenon, we describe the different regimes of DC and AC corona discharges, as they play a key role in the properties of the induced ionic wind. Then, in the third part, we discuss the time-averaged characteristics of the ionic wind. We show that positive corona discharges produce a sharp, pointed, and fast ionic wind jet, especially when breakdown streamers are present. On the contrary, the negative corona discharges usually produce a wider and slower air jet. In the fourth part, we describe the air movement from the tip when the high voltage is switched on. Moreover, we highlight that the Trichel pulses and the breakdown streamers play a fundamental role in the ionic wind dynamics. Finally, in the last part of this article, we focus on numerical simulations of ionic wind to explain all the experimental results presented earlier. Indeed, the origin of the ionic wind is the electrohydrodynamic force produced by the discharge. To determine this force, we need to know the electric field distribution and the density of electrons and ions everywhere in space at all times, which is achievable only through numerical simulations. To conclude, it can be said that research over the past ten years has led to a much better understanding of the ionic wind phenomenon, particularly regarding the role of unsteady and very fast phenomena such as Trichel pulses and breakdown streamers. However, there is still a lot of experimental and numerical simulation work to be done to optimize all the input parameters of the discharge according to the targeted application. And since the applications of ionic wind will most likely be at small scales, down to the sub-millimeter scale, it will also be necessary to study the behavior of corona discharges and the ionic wind they can generate at this scale.