Nonlinear Flow Behavior and Frequency Modulation in Corona-Driven Electrohydrodynamic Pumps: A PIV-Based Investigation

This study presents an in-depth experimental investigation of electrohydrodynamic (EHD) flow behavior induced by alternating current (AC) corona discharge in confined geometries, with a particular focus on the frequency-dependent fluid response of viscous dielectric oils. Leveraging high-speed imaging and Particle Image Velocimetry (PIV), we examine the unsteady dynamics of silicone oils (50 cSt and 100 cSt) subjected to high-voltage AC corona discharge. The analysis reveals complex nonlinear flow features, including frequency doubling, multi-harmonic responses, and sloshing-induced phase lags driven by asymmetric charge injection. At lower frequencies (10 mHz to ~2 Hz), fluid oscillations predominantly occur at twice the applied frequency, transitioning to a single-frequency regime beyond this threshold due to viscosity-driven damping. Peak oscillation amplitudes emerge at 2 Hz and 1 Hz for the lower and higher viscosity fluids, respectively, highlighting the critical role of fluid properties in modulating EHD flow behavior. Fourier and cross-correlation analyses provide further insight into spectral characteristics and energy distribution across frequencies. This work advances the understanding of AC-driven corona-induced EHD pumping mechanisms and offers practical guidance for optimizing frequency tuning in applications such as contactless micro-pumping, fluid mixing, and emulsion generation.