Key relationship
Re=ρvD/η; vcritical≈2300η/(ρD).
Physics · Class 11
Find the pipe-flow transition
Mechanical Properties of Fluids
Reynolds number compares inertia with viscous effects. A larger speed or diameter promotes transition, while higher viscosity favours laminar flow. The threshold is approximate rather than a universal switch.
Open the interactive experiment →Find the pipe-flow transition
ரெனால்ட்ஸ் எண் நிலைம விசை மற்றும் பாகுநிலை விசையை ஒப்பிடுகிறது. வேகம் அதிகரித்தால் கொந்தளிப்பு ஓட்டம் ஏற்படும் வாய்ப்பு அதிகரிக்கும்.
Key notes, relationships and model limits
Remember
Reynolds number compares inertia with viscous effects. A larger speed or diameter promotes transition, while higher viscosity favours laminar flow. The threshold is approximate rather than a universal switch.
Common trap
A single Reynolds number does not fully specify a turbulent velocity field.
Model limits
Steady internal flow in a round pipe. Re≈2300 is a guide for onset; real transition depends on disturbances. No direct turbulence solver is used.
What you will learn
Assess the relative importance of viscous and inertial effects.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
The approximate transition speed in that pipe is 2300×0.001/(1000×0.01)=0.23 m/s.
Why this matters
The model connects find the pipe-flow transition with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
For water in a 10 mm pipe at 0.1 m/s, what is Re?
- 100
- 1000
- 10000
Read the explanation
Re=1000×0.1×0.01/0.001=1000.
Course connection: Class XI Chapter 9. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.