Electrohydrodynamic wall jets from surface dielectric barrier discharge in confined air and nitrogen flows
We examined the effects of gas composition on ionic wind generation by surface dielectric barrier discharge (SDBD) in a confined rectangular channel. Air and nitrogen cases were compared under 2 kHz sinusoidal excitation while varying the applied voltage using the same channel and bulk flow rate. To characterize the coupled discharge-flow response, electrical measurements, optical imaging, and particle image velocimetry (PIV) were performed in the same configuration. Electrical measurements show that nitrogen discharges produce greater charge transfer and higher input power than air, accompanied by stronger optical emission and longer streamer propagation under comparable voltage conditions. From the PIV measurements, air produces higher near-electrode wall-jet velocities, whereas nitrogen sustains near-wall momentum farther downstream. The zero-dimensional ZDPlasKin kinetic calculation indicates different charge-carrier evolution in the two gases, with oxygen-based negative-ion formation and post-field persistence being more pronounced in air. The kinetic result is used to support the gas-dependent charge-carrier interpretation, while the wall-jet response is interpreted together with the measured discharge footprint and the phase-dependent nature of electrohydrodynamic forcing. These findings show that the electrical/optical discharge response and the wall-jet response do not necessarily scale together in confined SDBD actuation.