Figure 1.

Diagram of a wire-to-cylinder EHD flow. In positive corona, the negative species produced in the ionization zone recombine with positive species or the emitter (anode). The super-equilibrium positive ions drift to the collector electrode (cathode), accelerating the bulk flow. Thrust force is the resultant of the Coulombic force induced by the ions and drag force on the cathode. The conceptual representation of the EHD system includes (i) ionization region, (ii) flow acceleration region where unipolar ion motion in the gas medium acts as a body force accelerating the flow and (iii) momentum conservation region where the electric force is balanced or overcome by viscous effects. (Online version in colour.)