# For fully developed turbulent flow though rough pipe at very large Reynolds numbers, friction factor is

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For fully developed turbulent flow though rough pipe at very large Reynolds numbers, friction factor is
1. Dependent on Reynolds numbers only
2. Dependent on relative roughness of pipe only
3. Independent of both Reynolds numbers and relative roughness of pipe
4. Dependent on density of fluid only

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Correct Answer - Option 2 : Dependent on relative roughness of pipe only

Friction factor (f) for turbulent flow rough pipe is a function of relative roughness only.

$\frac{1}{{\sqrt f }} = 2\log \left( {\frac{R}{K}} \right) + 1.74$

for laminar flow Friction factor ⇒ $f = \frac{{64}}{{Re}}$

For laminar flow friction factor depends only upon the Reynolds number of the flow and is independent of the contact surface.