Question

I wanna know the theoretical values of Reynolds number for larminar and turvulent flow in smooth round pipe. For example, when Re is less than 2100, it is a laminar flow.

Answer 1

The Reynolds Number at which the flow of a Newtonian fluid becomes turbulent is called as the Critical Reynolds Number, Re_cir. The value of the Critical Reynolds Number is different for various geometries and different flow conditions. For internal flow in a Circular Smooth Pipe, the generally accepted value of the Critical Reynolds Number is Re_cir = 2300.

It is often required in Engineering to have precise values of Reynolds Numbers for laminar, transitional and turbulent flows, but, in practice, it turns out that the transition from laminar flow to turbulent flow also depends on the degree of disturbance of the flow by surface roughness, pipe vibrations and fluctuations in the flow. Under most practical conditions, the flow in a circular pipe is laminar for Re <= 2300 ; turbulent for Re >= 4000 and transitional in between them.

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