Bubble oscillations and dynamics under periodic electric fields

Understanding bubble dynamics under time-dependent electric fields is essential for applications in electrohydrodynamic(EHD) control, microfluidics, and phase-change heat transfer, but the interplay of polarization and Coulomb forces in leaky dielectric fluids is poorly understood. In this study, we experimentally investigated the growth and detachment of air bubbles injected into the leaky dielectric liquid HFE-7100 under periodic electric fields with square and sine waveforms at 50 and 100 Hz. High-speed imaging and image analysis revealed that EHD forces induced significant shape oscillations and strongly influenced bubble growth rates and detachment timing. Quantitatively, Fast Fourier Transform (FFT) analysis of the 100 Hz square wave data revealed dominant oscillation frequencies clustered between 135 Hz and 211 Hz. The response was highly dependent on the phase of bubble initiation, with polarity reversal often triggering detachment. Notably, under sine wave excitation, successive bubbles spontaneously organized into two alternating modes characterized by highly consistent aspect ratio evolution and volumetric growth. The bifurcation effect disappeared when a DC bias was added to the signal. These results demonstrate the critical role of waveform shape, frequency, and polarity in modulating bubble behavior in periodic fields, and provide new experimental insight into transient EHD effects in leaky dielectric fluids. • Periodic electric fields induce bubble oscillations in HFE-7100. • Bubble growth and detachment are dependent on the initiation phase of the bubble. • Polarity reversal could trigger bubble detachment. • Sine wave- driven electric fields could regulate the bubble into alternating modes.