Comparing pressure loss to Blasius

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The discussion centers on comparing pressure loss in a turbulent pipe flow simulation to the Blasius and Darcy-Weisbach equations. The user has conducted a CFD simulation and obtained a straight negative gradient for static pressure versus distance. It is noted that the Blasius equation is not suitable for turbulent pipe flow, while the Darcy-Weisbach equation is appropriate for this scenario. The conversation emphasizes calculating the friction factor from the pressure drop and using it alongside the Darcy-Weisbach equation to estimate theoretical pressure loss for comparison. Overall, the focus is on applying the correct equations for accurate analysis of pressure loss in turbulent flow.
Isabella F
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Hi everyone. i have done a CFD smulation in fluent for a turbulent pipe flow and have plotted static pressure against distance x. from the graph i get a straight negtive gradient. i have been told that you should compare the pressure loss to Blasius equation and Darcy equation. How do i compare the pressure loss to this. thank you. the fluid is water, diameter is 50mm, inlet velocity is 1m/s and reynolds number 49760.
heres is the xy plot i get.

s63xox.jpg
 
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Well that seems awfully silly to compare to Blasius because (A) it is pipe flow, so Blasius is not representative, and (B) it is turbulent, so Blasius doesn't apply.

Comparing to Darcy-Weisbach should be straightforward though.
 
The Blasius friction factor f=0.079/(Re^0.25).
Is there a way to calculate friction factor from the presure drop? that is what i think i need to do and then compare to blasius friction.
 
Ah, I thought you were referring to the Blasius boundary layer. My mistake.
 
How do i do this then. I am a bit confused.
 
Just look up the Darcy-Weisbach equation. It is very straightforward. Use it and the Blasius correlations to approximate the theoretical pressure loss (head loss) and compare to your results.
 
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