Effect of gravity and electric field on shape and surface tension of drops

Experimental work was performed in reduced gravity conditions using a novel methodology to investigate the effect of external forces, i.e., gravity and electric field, on shape and surface tension of drops. The new methodology, called axisymmetric drop-shape analysis - electric fields (ADSA-EF), can generate numerical drop profiles as a function of surface tension, at any given gravity and/or electric field. When an image of an experimental drop is available, ADSA-EF can calculate the true value of the surface tension by matching the numerical profiles with the shape of the experimental drop, taking the surface tension as an adjustable parameter. ADSA-EF is a novel technique, which can be employed to predict and simulate drop shapes in the electric field, determine the effect of external fields on surface tensions, or measure surface tensions in reduced gravity conditions, where other drop-shape techniques are not applicable. The results of the reduced gravity experiment suggested that the electric field significantly increases the surface tension of water. No significant effect of gravity on surface tension was detected.