Recently,i came to know that it is possible to have turbulent flow for Re less than 2300 in a circular pipe..but the flow will become laminar again as the disturbances vanish!!.
Same way is it possible to have laminar flow(for a small time period) for Re =9000~10000..???
The Reynolds number is a critical number at which the onset of turbulence is expected. That means that the ratio of momentum and viscous forces is such that the flow characteristics can be chaotic if a sufficient disturbance is provided. Below this threshold, the viscous forces can dissipate the turbulent production and return the flow to laminar.
There have been experiments devised to minimize the potential for disturbances and allow very high Reynolds numbers while maintaining a laminar flow, see the provided link.
Think of the Reynolds number as a critical threshold, really. Something analogous to balancing a pin ball on a hill. The higher the Reynolds number, the steeper and sharper the hill, and the more likely that pin ball will fall off the hill (where falling off the hill is the onset of turbulence). If the Reynolds number is less than the critical number, the hill is a ditch and the ball will always return to the point it started at (ie, become laminar).
http://www.off-ladhyx.polytechnique.fr/people/willis/papers/rsta2008.pdf
Dear Vipin Nair,
(1) It is true that it is possible to have turbulent nature in a theoretically laminar flow because of unexpected factors even if there is no special treatment.
(2) In my personal view, it is difficult to see laminar nature in a theoretically turbulent flow in a large pipe without special treatment.
(3) But please note that the laminar flow always exists near the origin of any flow.
(4) Then, in a very tiny gap between two plates, even if you increase the velocity until you get a theoretically turbulent flow, you could find laminar flow between the plates.
(5) Also, wait for discussion from other experienced researchers.
Yes, it is possible. Very special treatement is necessary, but for short period of time it is possible.
The Reynolds number is a critical number at which the onset of turbulence is expected. That means that the ratio of momentum and viscous forces is such that the flow characteristics can be chaotic if a sufficient disturbance is provided. Below this threshold, the viscous forces can dissipate the turbulent production and return the flow to laminar.
There have been experiments devised to minimize the potential for disturbances and allow very high Reynolds numbers while maintaining a laminar flow, see the provided link.
Think of the Reynolds number as a critical threshold, really. Something analogous to balancing a pin ball on a hill. The higher the Reynolds number, the steeper and sharper the hill, and the more likely that pin ball will fall off the hill (where falling off the hill is the onset of turbulence). If the Reynolds number is less than the critical number, the hill is a ditch and the ball will always return to the point it started at (ie, become laminar).
http://www.off-ladhyx.polytechnique.fr/people/willis/papers/rsta2008.pdf
Thank you everyone...your answers have cleared my doubt.
So we can conclude by saying that laminar flow is possible (theoretically) for high reynolds number flow but will always tend towards turbulence.
and Mr. Jesse M Johns
Thank you very much for that link which you shared.It made everything crystal clear.
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