Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

I've been using this online calculator to work out the difference in pressure and flow between two ends of a pipe:

Pipe Friction Calculation for Fluid Flow in a Pipe

So far most of it makes sense, and I've managed to figure out the worst of it (pipe relative roughness >_<). The main problem is that we don't have the "Average fluid velocity in pipe $\mathrm{V}$", only the Flow at A in $\mathrm{l}/\mathrm{s}$.

Before you mock the next part I should explain that I'm a software developer, which apparently still qualifies me more for this sort of work than my water engineer brother-in-law...

Anyway, to convert from Flow to Velocity, I made up the following:

L: litres per second at A
D: diameter of pipe (m)
V: fluid velocity (in m/s)

$$V = \frac{ 1000L }{ \pi(D/2)^2 } $$

Is this the correct conversion, or have I missed something?

share|improve this question
add comment

1 Answer

up vote 1 down vote accepted

Volumetric flow $\Phi = A V$. Therefore the right expression would be

$$V = \frac{ L/1000 }{ \pi(D/2)^2 }.$$

To get volumetric flow in SI units $\mathrm{m}^3/\mathrm{s}$ you should DIVIDE $\mathrm{l}/\mathrm{s}$ by 1000.

share|improve this answer
    
I had a feeling I'd missed something vital. Thanks. –  Stuart Pegg Apr 9 '12 at 21:17
    
Marko: We have MathJax active on the site so you can typeset you mathematics using LaTeX alike notation. I'll do this one for you. –  dmckee Apr 9 '12 at 21:20
    
@dmckee: Fancy. I've fixed my question using your edits as a template. –  Stuart Pegg Apr 9 '12 at 21:37
    
@dmckee cool. and some characters to obtain 15 –  Pygmalion Apr 9 '12 at 22:07
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.