Project which involve a falling water droplet

[blue_moon]

I am working on this project which involve a falling water droplet on both dry and wet surfaces to figure out how is the splash is going to affect the water separation however, I have to find out the droplet size providing this info

1) Needle diameter
2) Water tension

please help , if there is any derivation or formula that includes the tension and the needle diameter or whatever would help solving this problem?

thanks in advance,
Blue

 

[Astronuc]

There are formulas for drop size, surface tension and capillary diameter. I'll see if I can dig one up.

Meanwhile I found a really site - Microdrop - http://microdrop.de/index.html

http://microdrop.de/html/surface_tension.html

Hey, physics is


OK - found this - http://www.cheque.uq.edu.au/ugrad/theses/2000/iitheses/N_Cowper.pdf

Look at equations 9 and 10.

 

[blue_moon]

I founf this I am stuck I have no Idea how to get the droplet size or diameter from the relation below :

for the droplet to detach from the needle tip, gravity has to overcome the surface
tension. so when mg exceeds the interfacial tension at the release point the drop will
fall.
the interfacial tension is: surface tension x 2*pi*r where r is the needle radius.
Water at 20°C has a surface tension of 72.8 dynes/cm...