# Fluid droplets in a vacuum

1. Aug 12, 2014

### Mhorton91

Hello everyone, I have a question regarding the pattern resulting from droplets of fluid onto a hard surface.

Set-up
In addition to being a full time student I also work full time in the fuel bay of a local trucking company terminal. Not the most glamorous job, but regardless. This question comes from as follows, one of our pumps leaks a steady stream of small drops. When the floor is dry, and I watch them, the main drop seems to bounce then break into smaller drops which scatter randomly across the floor. (I'm sure there is a scientific name for this, I just don't know it)

Question
Despite efforts to hold the nozzle exactly still, the smaller drops (after the main drop has "bounced") always appear to spread out randomly. Now, I know that in spite of my efforts to keep everything perfectly still, there are always many small changes to wind speed, temp, volume of initial drop etc... However, it made me curious, if you set up a similar "dropper" in a fully isolated vacuum, and dropped identical drops one after another, would the resultant smaller droplets land in exactly the same position each time?

As I reread that, it doesn't sound like a very intelligent question to be asking, but my curiosity has become overwhelming; and I just have to ask.

Thanks for any input!
Requ

2. Aug 12, 2014

### davenn

hi there

I suspect you will find that the water droplets will boil and vaporise in the vacuum chamber

Dave

3. Aug 12, 2014

### Lok

A few things that influence the dripping:

There are also flow fluctuations which do not depend on air pressure or air in general. Like small vertices at the nozzle which fluctuate with time. And let's not forget Surface tension effects which coupled with the flow fluctuations will enhance the dispersion.
If you have a near perfect nozzle with a smooth flow the drops will be very consistent. But at small dimensions it is hard to get.

Doing the experiment in a vacuum at low temperature (to avoid some of the boil off) will be slightly better than in air, IMO.