The Reynolds (Re) number is the ratio of inertial forces to viscous forces and is a convenient parameter for predicting if a flow condition will be laminar or turbulent.

If Re is less than 2000, the flow is called Laminar, and if Re is greater than 4000, the flow is called turbulent.

**Formula to calculate Reynolds number.**

ρ = Fluid density

V = Fluid velocity

μ = Fluid viscosity

L = Diameter of the fluid.

**Example:**

Calculate the Reynolds number if a liquid of viscosity 0.5 Ns/m² and relative density of 400 Kg/m³ through a 0.01m pipe flows with a Velocity of 2m/s.

Therefore, the Reynold number is 16. Here, we notice that the value of Reynolds number is less than 2000, thus the flow of liquid is laminar.