Correct Answer - Option 1 :

One-half of the maximum velocity
__Concept:__

In a fully developed laminar flow through circular pipes velocity distribution according to Hagen-Poiseuille’s equation is

\(V = \; - \frac{1}{{4\mu }}\frac{{\partial P}}{{\partial x}}\left( {{R^2} - {r^2}} \right)\)

V is maximum at r = 0,

\({V_{max}} = - \frac{1}{{4\mu }}\frac{{\partial P}}{{\partial x}}{R^2}\)

Average velocity is given by

\({V_{avg}} = - \frac{1}{{8\mu }}\frac{{\partial P}}{{\partial x}}{R^2}\)

⇒ V

_{avg} = V

_{max}/2