The Origin of Turbulence

• Turbulence has its origins in the inherent instabilities of laminar flow
  
• Pufs and Slugs are turbulent structures and are obtainable in transitional pipe flows (Boundary Layer Theory by H. Schlichting)
  
  
• Turbulence dies out due to viscous damping unless some mechanisms keep on pumping energy into the velocity fluctuations
  
  
• The most important mechanism for generating and maintaining turbulence is shear in the mean flow
  
  
• Other mechanisms are : Stirring and Buoyancy