Mechanical Engineering - Hydraulics and Fluid Mechanics - Discussion

If the value of the friction factor is 0.064, then the Darcy friction factor is plotted in the Moody diagram. Note that the nonzero digits in 0.064 are the numerator in the formula for the laminar.

Darcy friction factor: fD = 64/Re.

If the value of the friction factor is 0.016, then the Fanning friction factor is plotted in the Moody diagram. Note that the nonzero digits in 0.016 are the numerator in the formula for the laminar.

Fanning friction factor: f = 16/Re.

Fanning friction factor for tube flow:.

This friction factor is one-fourth of the Darcy friction factor, so attention must be paid to note which one of these is meant in the "friction factor" chart or equation consulted of the two, the Fanning friction factor is the more commonly used by chemical engineers and those following the British convention.

1st the question should be coefficient of friction instead of loss of head.

W.k.t Darcy's Weinberg equation (i.e).

(4flv^2)/2gd,
Where, F=4f ; f- coefficient of friction.
(i.e)The friction factor is F = 64/Re,

Then coeff of friction 4f= 64/Re.
we get f=16/R6.

f is coefficient of friction while F is friction factor.
4f = F.

So, it can be both but first f must be specified in many books both friction factor and frictional coefficient are denoted same as 'f'.

If F= friction factor then F=64/Re.
but friction factor = 4* coefficient of friction,
So, if f= coe. of friction then f=16\Re,
Above is for laminar flow.

The Darcy friction factor f for laminar flow in a circular pipe (Reynolds number less than 2320) is given by the formula.

f = 64/Re.

Its depend on the "f" value, if it is nearly equal to 0.01, it would be f.

Or if it is nearly 0.0001, it would be "4f".

There is a mistake here, its not loss of head, its expression for coefficient of friction.

If friction factor is asked then 64/Re.

If coefficient of friction is asked then 16/Re.

16/Re is the Reynolds number.

Ref. R.K.Bansal, Som-Biswas-Chakraborty, F.M. White.