Welcome to DU!
The truly grassroots left-of-center political community where regular people, not algorithms, drive the discussions and set the standards.
Join the community:
Create a free account
Support DU (and get rid of ads!):
Become a Star Member
Latest Breaking News
General Discussion
The DU Lounge
All Forums
Issue Forums
Culture Forums
Alliance Forums
Region Forums
Support Forums
Help & Search
Do you take cream on your coffee?
How to levitate a droplet on a liquid surface
Michela Geri
Published on Nov 14, 2017
When a drop is released close to a bath of liquid (e.g. water or oil), our common sense tells us that the two should coalesce almost immediately. However when we pour drops of cold cream on our hot coffee or we observe raindrops over a puddle, we can often see the droplets floating on the surface for much longer than expected...so what happens? In this video we show that a temperature difference between a droplet and a bath can help levitate droplets without any direct contact!
For more details, see our paper @JFluidMech "Thermal delay of drop coalescence", by M. Geri, B. Keshavarz, G. McKinley and J. Bush.
Fluids in the video:
- cream on coffee
- silicone oils (1cSt...similar to water!)
Michela Geri
Published on Nov 14, 2017
When a drop is released close to a bath of liquid (e.g. water or oil), our common sense tells us that the two should coalesce almost immediately. However when we pour drops of cold cream on our hot coffee or we observe raindrops over a puddle, we can often see the droplets floating on the surface for much longer than expected...so what happens? In this video we show that a temperature difference between a droplet and a bath can help levitate droplets without any direct contact!
For more details, see our paper @JFluidMech "Thermal delay of drop coalescence", by M. Geri, B. Keshavarz, G. McKinley and J. Bush.
Fluids in the video:
- cream on coffee
- silicone oils (1cSt...similar to water!)
From http://news.mit.edu/2017/droplets-levitate-liquid-surfaces-1115 :
How to float your coffee creamer
Study explains how droplets can “levitate” on liquid surfaces.
Jennifer Chu | MIT News Office
November 14, 2017
A drop or two of cold cream in hot coffee can go a long way toward improving one’s morning. But what if the two liquids didn’t mix?
MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below. If the droplet is very cold, and the bath sufficiently hot, then the droplet should “levitate” on the bath’s surface, as a result of the flows induced by the temperature difference.
The team’s results, published in the Journal of Fluid Mechanics, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.
...
Study explains how droplets can “levitate” on liquid surfaces.
Jennifer Chu | MIT News Office
November 14, 2017
A drop or two of cold cream in hot coffee can go a long way toward improving one’s morning. But what if the two liquids didn’t mix?
MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below. If the droplet is very cold, and the bath sufficiently hot, then the droplet should “levitate” on the bath’s surface, as a result of the flows induced by the temperature difference.
The team’s results, published in the Journal of Fluid Mechanics, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.
...
More at link.
5 replies
= new reply since forum marked as read
= new reply since forum marked as read
In my lap making me scream. 
Some things are just too horrid to contemplate. 
IN my coffee.
