Why fluid flow becomes turbulent at high velocities??(velocity greater than critical velocity).Please explain descriptively.

Asked by Avi Wadhwa | 18th Dec, 2012, 12:52: PM

Expert Answer:

   R= Vc ρ D / η Reynold's number 'R' is a pure number and therefore, its numerical value is same in every set of units. The flow of viscous liquid is said to be steady when R lies between 0 and 2000. For values of R about 3000 floe is turbulent. For R lying between 2000 and 3000, the flow is unstable and may switch over from one type to another. We hope this clarifies your doubt.
Flow is usually considered to be laminar when a fluid flows through a tube and the
rate of flow is low.
As fluid flows through tubes there is resistance, between the fluid and vessel wall that
opposes the flow. For any given system, this resistance is constant .
Flow is affected by a number of other physical characteristics:
Tube diameter :If the diameter of the tube is halved the flow through it reduces to onesixteenth.
This means that flow is directly proportional to d4.

Length: If the length is doubled the flow is halved, therefore flow is inversely
proportional to the length of the tube.
 
Viscosity: This fluid is a measure of the frictional forces within the ‘layers’
described above. As the viscosity
increases the flow decreases proportionally,
 
There may be some more factors like: bending in the piupe, obstruction in the flow  etc, the flow speed increases abruptly...so becomes turbulent.

Answered by  | 19th Dec, 2012, 11:17: AM

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