Portland State University. Department of Mechanical and Materials Engineering
Date of Award
Master of Science (M.S.) in Mechanical Engineering
Mechanical and Materials Engineering
1 online resource (xi, 31 pages)
Fluid mechanics -- Research, Microfluidics, Drops, Hydrophobic surfaces
When confined within containers or conduits, drops and bubbles migrate to regions of minimum energy by the combined effects of surface tension, surface wetting, system geometry, and initial conditions. Such capillary phenomena are exploited for passive phase separation operations in micro-fluidic devices on earth and macro-fluidic devices aboard spacecraft. Our study focuses on the migration and ejection of large inertial-capillary drops confined between tilted planar hydrophobic substrates. In our experiments, the brief nearly weightless environment of a drop tower allows for the study of such capillary dominated behavior for up to 10 mL water drops with migration velocities up to 12 cm/s. We control ejection velocities as a function of drop volume, substrate tilt angle, initial confinement, and fluid properties. We then demonstrate how such geometries may be employed as passive no-moving-parts droplet generators for very large drop dynamics investigations. The method is ideal for hand-held non-oscillatory drop generation for fun, educational, and insightful astronaut demonstrations aboard the International Space Station.
Torres, Logan John, "Capillary Migration of Large Confined Drops in Non-wetting Wedges" (2019). Dissertations and Theses. Paper 4825.