Extreme Floating with Superhydrophobic Coatings
Water repellant (hydrophobic) coatings can make objects that are much heavier than water float. I discuss some of the unusual fluid mechanics for floating for objects with hydrophobic surfaces. I also discuss how the surface tension and hydrostatic pressure forces can be unified into a more generalized version of Archimedes’ principle. These concepts are not in current undergraduate fluid mechanics textbooks!
The coating used in this video is a two-step superhydrophobic commercial coating: Rustoleum Neverwet.
The mathematical proof that the weight of the fluid displaced by the meniscus is equal to the vertical component of the surface tension force can be found in this 1998 journal paper:
Keller, J.B., "Surface tension on partly submerged body", Physics of Fluids, vol. 10, no. 11, 1998.
https://aip.scitation.org/doi/10.1063...
Video for the hydrophobic and uncoated wood disks: • Effect of Surface Tension on Floating...
This document provides more information on a simple (undergraduate-level) solution for the wood disks and more information on the demonstration setup:
https://www.drdavidnaylor.net/uploads...
#fluidmechanics #fluiddynamics