Question

Which dimensionless number represents the ratio of inertial to viscous forces in forced convection?

• A. Nusselt number
• B. Reynolds number
• C. Grashof number
• D. Rayleigh number

Hint:

Reynolds number = \( \frac{\text{Inertial forces}}{\text{Viscous forces}} \) — key for predicting laminar vs. turbulent flow in forced convection.

Answer 1

The Correct Option is B

The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in different fluid flow situations.
It is defined as: \[ \text{Re} = \frac{\rho u L}{\mu} \] Where:
- \( \rho \) is the fluid density,
- \( u \) is the velocity,
- \( L \) is the characteristic length,
- \( \mu \) is the dynamic viscosity.
It represents the ratio of inertial forces to viscous forces in a fluid flow.
- High Re → Inertial forces dominate (turbulent flow).
- Low Re → Viscous forces dominate (laminar flow).
Other options:
- Nusselt number relates convective to conductive heat transfer.
- Grashof number is for natural convection (buoyancy vs. viscosity).
- Rayleigh number is the product of Grashof and Prandtl numbers.