Question

Which of the factors primarily decide whether the flow in a circular pipe is laminar or turbulent?

(a) The Prandtl Number

(b) The Pressure gradient along the length of the pipe

(c) The dynamic viscosity coefficient

(d) The Reynolds Number

I have been asked this question in an interview for internship.

Asked question is from Flow of Viscous Fluid Through Circular Pipes topic in division Viscous Flow & Turbulent Flow of Fluid Mechanics

Answer 1

The correct choice is (d) The Reynolds Number

For explanation I would say: High Reynolds number flows (> 4000) are turbulent flows, whereas low Reynolds number flows (< 2100) are laminar flows. The viscosity coefficient is a part of the Reynolds number, but isn’t the only criteria for decision.