friction losses in smooth walled pipes

Question

friction losses in smooth walled pipes

guest0821 (visitor)

(OP)

17 Mar 00 06:16

Osborne Reynolds conducted experiments in Manchester in the early 1880's to determine the nature of flow in pipes (laminar to turbulent)and demonstrated the onset of transition at reynolds number above 2100. Why did resent experiments in Manchester(using his original equipment)discover the onset of of transition to turbulence at significantly lower Reynolds number?

butelja (Mechanical) · Answer 1 · 2000-03-17 23:55:20

The onset of turbulence is VERY sensitive to the velocity profile of the fluid entering the pipe in question. Various references list the onset of turbulence at Reynolds numbers varying from 2000-4000+. Depending upon the steadiness of the flow rate and what type of upstream flow conditioning is used, the results can vary widely.

Also, modern instrumentation is very likely to be orders of magnitude more sensitive than anything dreamed of in the 19th century.

Another possible reason for the difference observed may have to due with deterioration of the original equipment. Is it possible that the equipment may have corroded (increasing its relative roughness) over a span of 120 years? I think so.

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friction losses in smooth walled pipes