Correct Answer - Option 3 : 2000
Explanation:
Reynolds Number
Reynold number is a dimensionless number that helps to predict flow patterns in different fluid flow situations.
\({\rm{Re}} = \frac{{{\rm{Inertia\;force}}}}{{{\rm{Viscous\;force}}}} = {\rm{\;}}\frac{{{\rm{\rho V}}{{\rm{L}}_{\rm{c}}}}}{{\rm{\mu }}} = \frac{{{\rm{V}}{{\rm{L}}_{\rm{c}}}}}{{\rm{\nu }}}\)
Where,
Re = Reynolds number, ρ = density, V = velocity of flow
μ = dynamic viscosity ν = kinematic viscosity, LC = characteristic linear dimension
For pipe flow:
LC = diameter of pipe = D
Reynold number = \(Re = \frac{{{\rm{\rho VD}}}}{\mu } = \frac{{{\rm{VD}}}}{\nu }\)
- Laminar flow Re ≤ 2000
- Transition flow 2000 ≤ Re ≤ 4000
- Turbulent flow Re ≥ 4000
The Reynolds number value below which flow can be definitely considered to be Laminar flow is called Critical Reynolds number Rc.
The values of the critical Reynolds number are listed below:
- For Pipe flow Rc = 2300
- For Flow between plate Rc = 1000
- For open channel flow Rc = 500
- For flow over plate Rc = 5 × 105
- For flow over sphere Rc = 1
