Influence of convective flow on filaments in DBD with varying gap lengths*

The gas flow convection in the discharge gap plays a role in determining the spatial distribution of charged particles, which in turn contributes to the pre-ionization process in the MD[1,2]. This pre-ionization in the discharge gap is a crucial element influencing the subsequent development of individual microdischarges and the formation of collective phenomena, such as self-organized patterns. The velocity of the MD rises, following the convective flow velocity due to the elevated thermal gradient.  During the self-heating of the barrier electrodes, the number of the MD increases, and the distance between the MD decreases which leads to more surface density of filaments on the dielectrics. The gas heating in the gap enhances the reduced electric field of the discharge due to a reduction in the density of gas molecules after heat expansion, which in turn results in the growth of the number of currents, amplitude, and reduction in the discharge sustaining voltage.

In this work, we are interested in investigating the effect of the balance between the forces driving the convective flow and the viscous forces at the wall in the boundary region when the discharge gap is significantly narrowed. Discharge parameters such as microdischarge and gas flow average velocities, and discharge and dielectric layer temperatures were measured. From high-speed imaging of the discharge and PIV analysis, the movement of the filaments is obtained, and the average velocity is measured at a certain temperature of the dielectric layer.