Question

Calculate Reynold's number if a fluid having a viscosity of $0.25{\text{N.s/m}}^2$ and density of $800{\text{kg/m}}^3$ flows through a pipe of radius $10\text{mm}$ with a velocity of $2\text{m/s}$.

• A. $120$
• B. $128$
• C. $132$
• D. $114$

Answer 1

The correct option is B $128$


Reynolds number, $N_{Re}=\frac{\rho VD}{\mu }$
where, viscosity of liquid is $\mu =0.25{\text{N.s/m}}^2$
Diameter of pipe,$D=20\times {10}^{-3}\text{m}$
$N_{Re}=\frac{800\times 2\times 20\times {10}^{-3}}{0.25}$
$\therefore N_{Re}=\frac{32}{0.25}=128$