Validation of Sessile Drop Interface Shape Reconstruction using Steroscopic Speckle Imaging

The complete interface shape of sessile liquid drops is measured using a stereoscopic imaging technique. The approach records surface speckle patterns that refract across the liquid/gas interface and compares these patterns to control images with no drop present. Various interface shape candidates options are evaluated using a nonlinear optimization technique in order to reconstruct the drop shape that produced the particular surface speckle pattern. Earlier work (DFD Z04.00003, 2020) provided a proof-of-concept of the stereoscopic approach. The present effort refines the technique and provides extensive validation for drops on horizontal and inclined surfaces. Validation is provided by comparing reconstructed drop shapes to side-view drop profiles and applied drop volumes as well as by comparing estimated contact-line pinning force to downhill gravity forcing of the pinned drops.