Question

What is the maximum flow speed of water for laminar flow in a pipe having a diameter $5cm$ given that coeficient of visocity of water is ${10}^{-3}Pa$ $sec$ .

Answer 1

For laminar flow, the Reynolds number is,

$R_e\le 2000$

The Reynolds number is given as,

$R_e=\frac{\rho v_{av}D}{\mu }$

$v_{av}=\frac{R_e\mu }{\rho D}$

$=\frac{2000\times {10}^{-3}}{1000\times \left(0.05\right)}$

$=4cm/s$

The maximum velocity will be twice the average velocity. Therefore,

$v_{max}=2\times 4$

$=8cm/s$