Dimensional Analysis for Laminar Flow Equation 2

[KimWonGun]

Using the Hagen-Poiseuille equation for laminar pipe flow: Q = [deltaP/L]*[(pi*Dsquared)/(128*mu)], where Q = flow rate (cubic inch/sec), L = pipe length (inch), mu = dynamic viscosity (lbf*sec/sq. inch), and D = pipe diameter (inch), I get inch/sec from dimensional analysis when expecting cubic inch/sec. What did I miss?

 

[ione]

You've entered a wrong exponent for the diameter.

The right formula is:

Q = deltaP*pi*D^4/(128*mu*L)

 

[vpl]

I believe your equation is wrong. Isn't it D⁴ instead of D²?

See Wikipedia re Hagen-Poiseuille.

Patricia Lougheed

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