The Reynolds number is used to identify the type of fluid flow in a pipe as either laminar or turbulent. It is a dimensionless quantity that represents the ratio of inertial forces to viscous forces. A Reynolds number below 2100 indicates laminar flow, above 4000 indicates turbulent flow, and between 2100-4000 is the critical transition region. It was first introduced by George Stokes and developed by Osborne Reynolds to characterize fluid flow and the transition between flow patterns.

1. Reynolds Number

2. Content
• Why Reynolds Number
• Important terms
• Introduction
• How dimensionless?
• Reynolds Number conditions

3. Why Reynolds number?
• To identify the flow type of liquid in a pipe
(laminar or turbulent)
• Life of a pipe

4. Definition
• Inertial force: a force opposite in direction to an accelerating force
acting on a body
• Laminar flow: the flow of a fluid when each particle of the fluid
follows a smooth path, paths which never interfere with one another. One
result of laminar flow is that the velocity of the fluid is constant at any
point in the fluid.
• Turbulent flow: irregular flow that is characterized by tiny
whirlpool regions. The velocity of this fluid is definitely not constant at
every point.

5. Definitions
• Viscous forces in a fluid are proportional to the rate at which the fluid
velocity is changing in space or a measure of a fluid’s resistance to flow.

6. Introduction
• Reynolds Number?
• First introduced by Sir George Stokes and later on globalized by Osborne
Reynolds
• The fluid moving force and fluid resisting force
• The ratio of inertial force to viscous force is called reynolds number.
• Denoted as “ ”

7. Mathematical representation
• To gain high reynolds number we should have high velocity
• Different fluid have different Reynolds number
• It is a dimensionless quantity

8. How dimensionless

9. Reynolds number condition
• If Reynolds number is less than 2100 then the
flow in pipe is laminar.
• If Reynolds number is greater than 4000 then
the flow in pipe is turbulent
• If Reynolds number is between 2100 to 4000
then flow is under transition region and under
this region it is called as critical Reynolds
number

10. Numerical appraoch
• An oil viscosity of 0.006 poise is flowing
through a pipe of dia 0.2 m with a velocities of
1.91 m/sec and 0.05 m/sec and density of
fluid is as 900 kg/cubic m. Find the Reynolds
number

11. Laminar flow

12. Thank you?