MAE Assistant Professor Luc Deike's Research Highlighted

Luc Deike

So much depends on the velocity of tiny droplets cast upward

A day at the beach beset by heavy clouds or the sticky heat of a salty haze can seem like the work of large, unpredictable forces. But behind such atmospheric phenomena are billions of tiny interactions between the air and microscopic drops of saltwater cast upward as bubbles on the ocean’s surface burst.

Research recently published in the journal Physical Review Fluids now describes the “jet velocity” of these droplets, or aerosols, as they occur in liquids such as seawater and sparkling wine. The researchers created a model for predicting the velocity and height of jet aerosols produced by bubbles from 20 microns to several millimeters in size, and in liquids as viscous as water or up to 10 times more viscous.

The “jet” refers to the liquid that spurts up after a bubble has burst. Once the dome-like film of the bubble is gone, the small cavity the bubble created beneath the surface rushes to close. The bottom of the pocket rises rapidly as the sides of it collapse downward. When these forces meet, they launch a jet of water into the air that contains droplets ranging in size from 1 to 100 microns (a micron is one-millionth of a meter; the diameter of a human hair is roughly 100 microns).

Droplets from bursting bubbles are the principle means by which aerosols are produced above the open ocean, said first author Luc Deike, a Princeton University assistant professor of mechanical and aerospace engineering and the Princeton Environmental Institute (PEI). Knowing the speed and height at which aerosols are being thrown into the air can be used for more accurate climate modeling or creating a perfect glass of champagne.