The Capillary Flow Experiments Aboard ISS: Moving Contact Line Experiments and Numerical Analysis

This paper serves as a first presentation of quantitative data reduced from the Capillary Flow Contact Line Experiments recently completed aboard the International Space Station during Expeditions 9-16, 8/2004-11/2007. The simple fluid interface experiments probe the uncertain impact of the boundary condition at the contact line—the region where liquid, gas, and solid meet. This region controls perhaps the most significant static and dynamic characteristics of the large length scale capillary phenomena critical to most multiphase fluids management systems aboard spacecraft. Differences in fluid behavior of nearly identical static interfaces to nearly identical perturbations are attributed primarily to differences in fluid physics in the vicinity of the contact line. Free and pinned contact lines, large and small contact angles, and linear and nonlinear perturbations are tested for a variety of perturbation types (i.e. axial, slosh, and other modes) to right circular cylinders. The video and digitized datasets are to be made publicly available for model benchmarking. In parallel with the experimental effort, blind numerical predictions of the dynamic interface response to the experimentally applied input perturbations are offered as a demonstration of current capabilities to predict such phenomena. The agreement and lack of agreement between the experiments and numerics is our best guide to improve and/or verify current analytical methods to predict such phenomena critical to spacecraft fluid systems design.