Turbulent spots, wave packets, and growth

The smoke wire technique was used to initial formation and growth of turbulent spots in a laminar boundary layer. The spots were observed to result not from the breakdown of wave packets arising at the spot generator but from longitudinal structures which preceded the wave packets. The original wave packet in turn was observed to ultimately take the form of oblique waves trailing the spot. These waves had little apparent involvement in the growth of the spot and did not appear to be associated with the formation of new spots within the region visualized.