moody f(reynolds#,e/D)

[catpidgeon]

Has anyone curve fitted subject Moody reference - friction factor as a function of NRe and relative roughness?

 

[jproj]

There are several equations that have been developed to describe the friction factor as a function of both the relative roughness and the reynolds number. The equations are dependant on the reynolds number, though. For laminar flow, the equation is simple (f = 16/Re), but turbulent flow, it is much more complex (Colebrook equation, Wood's approximation).

Colebrook Eq: (1/f^0.5)=-4*log[((e/D)/3.7)+(1.255/(Re*f^0.5))]

Wood's Approximation: f = a + b*Re^(-c)
a = 0.0235*(e/D)^(0.225)+ 0.1325*(e/D)
b = 22*(e/D)^(0.44)
c = 1.62*(e/D)^(0.134)

Hope this helps!

jproj

 

[TD2K]

I've got a paper that discusses several correlations for friction factor, drop me a line at testdog2000@yahoo.com and I'll forward you a copy.

 

[quark]

Catpidgeon!

http://me.queensu.ca/courses/mech441/spr/moody.xls

This is for Colebrook equation and don't forget to grab that paper from TD2K. (If you don't get the link, mail me at builblock1@yahoo.com. I will send you the excel file).

TD2K!

I don't think you will be asking me for royalty. I forwarded that paper[free of cost:-(] to atleast 20 members of this forum and got good responses from all. That is a very good paper and thanks for it.

By the way an iteration method was mentioned in that paper to derive the explicit functions of colebrook equation. Do you have that paper too?

Best Regards,