Saturday, June 22, 2019

fluid dynamics - Does steady flow imply laminar?


Most secondary school textbooks, in their chapter about fluid dynamics, seem to suggest that "steady flow" and "laminar flow" are synonyms.


Though I never received any fluid mechanics course when I was at the university, it's pretty obvious to me that flows can be laminar but non-steady. But what about the converse? Can a steady flow be non-laminar?


If I skim through more advanced textbooks and lecture notes, I can't find any direct reference of a strict relation between the two concepts, neither positive nor negative. Yet "between the lines" most of the texts seem to take as a fact that steady implies laminar.


Is that true? Is a steady non-laminar flow something theoretically possible in some context (eg. inviscid flow in a purely continuum-mechanical model of a fluid) but physically unobtainable in any actual fluid? Is the implication blatantly false?


My imagination has apparently no problem at visualizing some sort of weird self-intersecting (and consequently non-laminar?) flow which doesn't vary over time. Am I missing something? I definitely guess that I am.




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