72th Annual Meeting of the APS Division of Fluid Dynamics (November 23, 2019 — November 26, 2019)

V0029: Heavy Metal Rain

Authors

• Ryan McGuan, University of California Los Angeles
• Rob Candler, University of California Los Angeles
• Pirouz Kavehpour, University of California Los Angeles

DOI: https://doi.org/10.1103/APS.DFD.2019.GFM.V0029

Every day events such as the splash of a raindrop, the breaking of a wave, the mixing of milk into coffee, appear so simple to our eyes, yet there is a wealth of complex phenomena that occur faster than the blink of an eye. Here we present a study of coalescence featuring liquid metal which boasts one of the highest surface tensions of any liquid on Earth. Liquid metal can be found in nature including the interior of planets, the formation of celestial bodies and even on the surface of the hottest planets where molten metal falls as rain.  Applications include forging, casting, and molten metal additive manufacturing techniques. We utilize a gallium-indium-tin alloy, coalescing in a pool of the same metal. While the surface  tension is exceptionally high (σ = 0.718 N/m in air) the surface oxidizes, producing an elastic skin that resists normal capillary behavior. We then go on to remove this skin using sodium hydroxide (NaOH) and observe a cascade of droplet coalescence events.