Bouncing Water Droplets and the ‘Reverse Crown’

When a hydrogel bead is dropped onto a water droplet the fluid is lifted up from the surface creating some incredible structures such as the ‘reverse crown’ and the ‘dancing ballerina’.

As the hydrogel bead impacts with the surface it flattens, increasing the contact area. If the width of the contact area is greater than the diameter of the water droplet, the droplet is lifted up by the rebounding bead and thrown into the air. The resultant splash patterns that form are determined by the drop-height and the droplet size. Repeating the same experiment with a solid sphere does not cause ‘lift-off’, with instead a bridge or ligament of fluid forming between the sphere and the droplet which remains the surface.

Research by Rafsan Rabbi and Tadd Truscott at Utah State University. Interview with University of Oxford Mathematician Dr Tom Crawford.

This video is part of a collaboration with the Journal of Fluid Mechanics and the UK Fluids Network featuring a series of interviews with researchers from the APS DFD 2019 conference.

Sponsored by the Journal of Fluid Mechanics and the UK Fluids Network. Produced by Tom Crawford.

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