Ideas about eddy size
- For a moderate velocity ( ~ 100 m/s), smallest eddy will be of the order of 0.5 mm
- In gases under atmospheric conditions, mean free path is the range of 10 -4 mm
- Turbulent frequencies vary between a few Hz and 10 kHz
- Molecular collision frequency ~ 5 × 10 9 Hz (air)
Therefore turbulence is within continuum!
Large eddies: 
Small eddies: 
ν : dimension L2 / T ;  dimension ( L2 / T 3 )
Dissipation 
Velocity scale 
Intensity of Turbulence or Degree of Turbulence
For isotropic turbulence, 
 (used in practice, even if the turbulence is not isotropic!)
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