The Determination of Surface Tension by Video Image Processing of Fluid Drops (Suitable Range of Bond Number for Measurements with Sessile Drop)

Abstract

In this study, we discuss the reliability of surface tension which is determined by digital video im­age processing of a sessile drop with using computer. The image of a sessile drop of pure water formed on a teflon plate was recorded on a digital video tape and converted into digital data of profile by using the technique of digital image acquisition and processing. The segmented drop image is fit­ted with numerical solution of theoretical equations by performing a least-squares comparison to determine a surface tension. The measurements was repeated many times for various size (diameter of 3 mm-35 mm) of drops. At the drop range from 12 to 17 mm, most results were agreed well with the international standard value (IAPS) of surface tension of water. We found the water drop of 12-17 mm is suitable for surface tension measurement and this range corresponds to Bond number of 20- 150.