Capillary Flow Experiments Conducted Aboard the International Space Station: Experiments and Simulations

The multi-phase solver interFoam within the open-source CFD software OpenFOAM is newly applied to rare experiments conducted beginning over 10 years ago aboard the International Space Station (ISS). The fluid physics of interest concern large length scale passive capillary flows in a microgravity environment driven largely by surface tension, wetting conditions, and container or conduit geometry. Such flows are critical to orbiting and coast spacecraft liquid fuels, propellants, cryogens, thermal fluids, and aqueous streams for water management, recycling, and life support. The value of the simulations is assessed via quantitative comparisons to the ISS Capillary Flow Experiments (CFE) for a series of centimetric handheld test cells. Three representative flows are simulated as functions of geometric complexity: 1) bubble coalescence, 2) ullage migration, and 3) draining flow. The experimental data is newly digitized for the bench-marking effort. The favorable agreement between the simulations and experiments adds confidence for advanced applications of the native interFoam multi-phase solver of the OpenFOAM suite, where experimental data is scarce.