Pipe Flow Calculations Forum

hi all, newbie here!!
i'm writing a report for college in which im investigating the effect of roughness on air flow through a pipe. so far i have used 2 pipes in a wind tunnel, 1 rough and 1 smooth bore, 800mm long with a 36mm inner diameter. using an anemometer i measured the wind speed entering the pipe and exiting the pipe, this gave me the change in speed. my calculations on the other hand have given me a change in pressure (D'Arcy Weisbach eqn) is there any way i can convert between the change in pressure and the change in air speed?? thanks for any help

How is you system looking? Do you have one point where two pipes start and air exits to atmosphere?
If so than you have two parallel lines with same pressure drop (pressure change) from the start to the finish and for that equal pressure difference two flow rates are established - which you can use to calculate velocity from Darcy equation.

i'v done the practical side of things with the pipe in the wind tunnel with air speeds of approx 4m/s, 6m/s and 10m/s entering the pipe, the end of the pipe is going to atmosphere, the exiting speeds are approx 2m/s, 2.5m/s and 4m/s. from my calculations i seem to be getting pressure drops using this formula=> ΔP=f(L/D)((ρv^2)/2)
correct formula?? thanks for the reply

dan-g wrote: ΔP=f(L/D)((ρv^2)/2)

+ ((ρv^2)/2) due to pipe exit. Correct formula it is!

what way can i use the formula to give me a comparable value to the practical results though?? cheers