Computational evaluation of axisymmetric drop shape analysis-profile (ADSA-P)

Abstract

Axisymmetric drop shape analysis-profile (ADSA-P) was developed to determine liquid—fluid interfacial tensions and contact angles by fitting the Laplace equation of capillarity to an arbitrary array of coordinate points selected from the drop profile. The present study addresses the question of the accuracy of the actual ADSA-P algorithm itself as well as questions of the effect of the number of experimental points and their accuracy. This paper presents a summary of such an investigation by using drop profile coordinates obtained from an independent numerical integration. Three factors were studied: (i) the required number of profile data points, (ii) the number of significant figures of profile data points, and (iii) the randomness of choice of data points. It was found that the accuracy of the results is not limited by ADSA-P, but only by experimental and/or procedural matters. Specifically, the use of a small number of accurate points is more effective than the use of a large number of less accurate points. For a given level of accuracy of the coordinate points representing the drop profile, performing the ADSA-P calculations several times with a relatively small number of points is more efficient than a single ADSA-P run with a very large number of points. Also, the data points near the neck of a pendant drop or near the solid—liquid interface for a sessile drop are critical, if accuracy of the drop profile coordinate points is limited.