The effect of charge mode transition on electrohydrodynamic flow in a multistage negative air corona discharge

We study the electrohydrodynamic (EHD) flow induced by a multistage negative air corona discharge with two main subjects: unipolar-to-bipolar charge mode transition, mechanism of EHD flow. Charge mode transition is identified through the maximum-current-based numerical analysis of a six-stage cylindrical ionic wind generator, and confirmed by the experimental data. After formulating the degree of charge mode transition beta, we discuss how beta affects the electric-to-kinetic energy conversion efficiency and the thrust performance of the EHD flow. We suggest 35 Td of reduced electric field on the collector surface as the occurrence criterion of charge mode transition. As an essential feature of the multistage EHD flow, the highest negative pressure is created in the intake. Accordingly, air is drawn into the intake and subsequent flow climbs up a positive static pressure slope, and exhausted into the atmosphere with a high linearity. We explain the physical mechanism of this interesting flow pattern using the first-principle based analysis.