Question

Due to aging of a pipeline, its carrying capacity has decreased by 25%. The corresponding increase in the Darcy Weisbach friction factor, f is %

• A. 77

Answer 1

The correct option is A 77
As we know,

$h_f=\frac{fL{Q}^2}{12.1d^5}$

$\therefore f=\frac{12.1h_f{d}^5}{L{Q}^2}$

$\Rightarrow f\propto \frac{1}{Q^2}$

If Q is decreased by 25%, then

$f^{\prime }=\frac{k}{(0.75Q{)}^2}=1.77f$

$\therefore$ Value of Darcy's Weisbach friction factor is increased by 77%.