# In smooth pipes, if R represents Reynold's number, Friction factor for turbulent flow is given by:

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In smooth pipes, if R represents Reynold's number, Friction factor for turbulent flow is given by:
1. 0.64/R
2. 64/R
3. 0.316/R1/4
4. 0.316/R4/5

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Correct Answer - Option 3 : 0.316/R1/4

Concept:

Friction factor:

• The friction factor is not constant. It depends on such things as the characteristics of the pipe (diameter and roughness height ), the characteristics of the fluid (such as kinematic viscosity), and the velocity of the fluid flow.

Friction factor for laminar flow:

${\rm{f}} = \frac{{64}}{{\rm{R}}}$

Friction factor for turbulent flow:

${\rm{f}} = \frac{{0.316}}{{{{\rm{R}}^{\frac{1}{4}}}}}$, When 4000 < R < 105

${\rm{f}} = 0.0032 + \frac{{0.221}}{{{{\rm{R}}^{0.237}}}}$, When 105 < R < (4 × 107)