text: The onset of Görtler vortices can be predicted using the dimensionless number called Görtler number (G). It is the ratio of centrifugal effects to the viscous effects in the boundary layer and is defined as
  where
  :  = external velocity
  :  = momentum thickness
  :  = kinematic viscosity
  :  = radius of curvature of the wall
  Görtler instability occurs when G exceeds about 0.3.