Question

A dimensionless number which represents the ratio of inertia to viscous force is:

• A. Reynold’s number
• B. Froud’s number
• C. Prandtl number
• D. Stanton number

Hint:

To remember: Reynolds = Ratio of Inertia over Viscosity. Think of it as the struggle between the fluid's speed and its "stickiness."

Answer 1

The Correct Option is A

Fluid flow behaviour is often summarised using dimensionless numbers built from ratios of different forces. The Reynolds number is defined as \( Re = \dfrac{\rho v D}{\mu} \), where the numerator represents the inertial force pushing the fluid forward and the denominator, involving viscosity, represents the internal resistance opposing that motion. Whether a flow stays smooth or turns chaotic depends on which of these two forces wins out, and that comparison is exactly what the Reynolds number captures.