Question

Calculate Reynold’s number, if a fluid having a viscosity of $0.4{\text{Ns/m}}^2$ and density of $900{\text{kg/m}}^3$ flows through a pipe of length $20\text{mm}$ with a velocity of $2.5\text{m/s}$.

• A. $112.5$
• B. $130$
• C. $121.5$
• D. $100$

Answer 1

The correct option is A $112.5$

As we know, $R_e=\frac{\text{Inertia force}}{\text{Viscous force}}$
$R_e=\frac{\rho vL}{\eta }=\frac{900\times 2.5\times .02}{0.4}$
$R_e=112.5$