# surface tension and dropping (NEED HELP İN PROBLEM)

#### koytos

Hello friends;

i want to solve the problem about surface tension and dropping. i find a equation on http://planetcalc.com/2296/
and i enter this formulato excel. But i dont sure this formula is true.

for water :
if pipe outlet diameter is 9,45mm (or less) no dropping occuring cause of surface tension force.

for oil :
if pipe outlet diameter is 7,43mm (or less) no dropping occuring cause of surface tension force.

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#### ChipB

PHF Helper
Hello friends;

i want to solve the problem about surface tension and dropping. i find a equation on http://planetcalc.com/2296/
and i enter this formulato excel. But i dont sure this formula is true.

for water :
if pipe outlet diameter is 9,45mm (or less) no dropping occuring cause of surface tension force.

for oil :
if pipe outlet diameter is 7,43mm (or less) no dropping occuring cause of surface tension force.

I get different results: R = 3.34 mm for water and 2.63mm for oil. I think in your Excel calculation you forgot the 2 in the denominator of the equation.

And the interpretation of R is it is the maximum size of pipe that will allow dripping, as opposed to continuous flow. For pipes of smaller radius you get drops, for pipes of larger radius you get continuous flow (according to the author).

#### koytos

how can i calculate this system if the outlets are like in the picture?

5 different outlets
1- elips
2- square
4-circle
5- circle (but it has a filter)

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#### koytos

if you dont understand clearly, please write.

#### ChipB

PHF Helper
Given that the formulas for this type of thing are empirical, I think you would have to try some experiments with these shapes and see what you get. But a reasonable estimate might be to use the distance from the centroid of each shape to the furthest part of the perimeter as the equivalent of radius in the formula.

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#### koytos

Given that the formulas for this type of thing are empirical, I think you would have to try some experiments with these shapes and see what you get. But a reasonable estimate might be to use the distance from the centroid of each shape to the furthest part of the perimeter as the equivalent of radius in the formula.
thank you.