Electrohydrodynamic characteristics of a needle-to-ring positive corona discharges: self-consistent modeling and turbulence effects
Résumé
Abstract We report on the voltage–current characteristics as well as the voltage–velocity characteristics of a needle-to-ring configuration by self-consistent, 2D-axisymmetric, multi-physics plasma-fluid simulations. Parametric studies are performed to investigate the effects of background ionization level on the plasma electrical characteristics as well as turbulence parameters on the resulting flow. Our results show that the discharge and the flow exhibit an annular structure around the needle (anode) tip, with a maximum positive ion density from 1.5 × 10 18 –2.7 × 10 18 m − 3 and a maximum flow velocity from 10–15 m s − 1 , for overvoltages between 4−12 kV and an anode–cathode distance of 20 mm . Good overall agreement with experimental findings is achieved, noting that background ionization level can be used as a tuning parameter to better match experimentally measured current values even with a simplified plasma-chemistry. A better agreement between simulation and experiments is achieved concerning the voltage–velocity curves. Therefore, the latter are likely to be better indicators for assessing and validating electrohydrodynamic effects of corona actuators through numerical modeling. The flow dynamics indicate that positive-corona-induced ionic winds are most likely laminar to turbulent transitional flows, with a ratio between eddy viscosity and air viscosity varying between 0 − 200 .