Question

Explain how the formula forvcritical velocity is derived

Answer 1

Originally Answered: What is critical velocity?

Critical velocity is the velocity (speed and direction) at which the flow of a liquid through a tube changes from laminar (smooth) to turbulent.

Calculating critical velocity depends on several variables. Reynold’s number (Re) characterizes the flow of the liquid through a tube as either laminar or turbulent. Reynold’s number is a dimensionless variable, which means it has no units attached to it.

Reynold’s number formula:

where ρ = density of the fluid, V = velocity of the fluid, L = length or diameter of the fluid, and μ = viscosity of fluid.

The kind of flow is based on the value of Re.

If Re < 2000, the flow is called laminar

If Re > 4000, the flow is called turbulent

If 2000 < Re < 4000, the flow is called transition

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