Question

The Reynolds number of a flow is the ratio of

• A. Gravity to viscous force
• B. Gravity force to pressure force
• C. Inertia force to viscous force
• D. Viscous forces to pressure forces

Answer 1

The correct option is C Inertia force to viscous force

The Reynolds number is defined as the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions.
$\therefore$ Reynold's number $=\frac{\text{Inertia force}}{\text{Viscous force}}=\frac{\rho VD}{\mu }$