Bubble Distortion due to EHD Stress
S. Siedel1, 2, S. Cioulachtjian1, A. J. Robinson2, and J. Bonjour1
1Universite de Lyon, CNRS
INSA-Lyon, CETHIL UMR5008, F-69621, Villeurbanne, France
2Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland
Abstract- The effects of DC electric fields on bubble shape has been investigated for the case of boiling at the scale of a single bubble. The electric stress on the interface induced by the presence of electric fields has been analytically described. Its effects have been studied theoretically by numerical simulation of a single in a direct current electric field. Controlled experiments have been performed in order to complete the analysis. It has been shown that an initially uniform electric field is distorted by the presence of a bubble, creating lower electric field intensities on the top and bottom sections of the bubble and higher electric field intensities on the sides. For non-polar and non-charged fluids, the electric stress is normal to the interface, directed towards the vapor when the electric field is tangent to the interface and towards the liquid when the electric field is normal to the interface. This electric stress adds a new force component in the force equilibrium that governs the bubble shape, together with surface tension and buoyancy, that leads to a elongation of the bubble in the electric field direction.
Keywords- Electrohydrodynamics, electric fields, bubble, elongation