Experimental study on flow characteristics of electrohydrodynamic plumes in a needle-plate configuration with viscoelastic dielectric liquids

An experimental investigation is conducted on the electrohydrodynamic (EHD) plume of viscoelastic dielectric liquids induced by an electric field in a needle-plane configuration. A novel viscoelastic liquid with low conductivity is prepared using 25# transformer oil as the base fluid and polyisobutylene (PIB) as the additive. A particle image velocimetry (PIV) system is employed to measure the flow velocity field, and the voltage–current characteristics are also recorded. The motion of SiO₂ seeding particles under a strong electric field is evaluated to ensure the accuracy of the velocity field measurements. The effects of applied voltage and polymer concentration on the plume flow morphology, plume width and velocity are discussed, with special emphasis on the role of elastic stress on the flow characteristics. The experimental results indicate that the greater the viscoelasticity of the fluid, the closer the position at which the velocity is fully developed to the needle tip. And the velocity and plume width are significantly affected by viscosity.