How can I calculate the critical Reynolds number knowing the diameter of a sphere?

Question

Is there a table for it?
If I need some kinda formula or more information, please tell me.
Thanks

Answer 1

If the sphere is not inside a relatively narrow pipe, the number is about 3.85 * 10^5. There is no formula for it, it is defined experimentally - see slide 23 in [1]. A short description of the phenomenon itself is, for example, in [2]:
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It is known that a sphere in a steady flow will exhibit differing drag coefficient values depending on whether the boundary layer on the sphere surface is laminar or turbulent. The free-stream velocity at which the transition from laminar to turbulent flow occurs depends on the diameter of the sphere and the turbulence level of the free-stream flow. It is also known that in an atmospheric free-stream the Reynolds number for transition is approximately 385,000. At this critical Reynolds number, the drag coefficient of a sphere drops from a value > 0.4 to a value < 0.2. By measuring the Reynolds number at which this drop occurs in a wind tunnel for different size spheres, one may determine the turbulence level at different velocities.
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This should be enough info for you to make a deeper search on the Internet if needed.

Answer 2

Reynolds Number Calculator

Answer 3

Re= ?d/v relies upon on the scale of the cylinder, oil has a intense viscosity so it could probably be laminar under 2000RE.till the different cylinder is shifting very speedy. could require all the tips to make a applicable judgement