Dimensional Analysis and Similitude MCQ with answer and solution

Concept

Reynolds Number

Formula

Re = (ρ × V × L) / μ

Step-by-step solution

1. Identify the given parameters: fluid density (ρ), flow velocity (V), characteristic length (L), and dynamic viscosity (μ). 2. Multiply density, velocity, and length together (ρ × V × L). 3. Divide the product by the dynamic viscosity (μ) to calculate the Reynolds number (Re).

Explanation

The Reynolds number is a dimensionless quantity defined as the ratio of inertial forces to viscous forces in a fluid flow, making it the key parameter to determine which force dominates.

Shortcut

Remember "Re = Inertia / Viscous": Reynolds number is the ratio of Inertial forces to Viscous forces.

Common mistake

Many students confuse the Reynolds number with the Froude number, which represents the ratio of inertial forces to gravitational forces rather than viscous forces.