On turbulent spots.

In order to simplify the study of large eddies in turbulent boundary layers a laminar boundary layer was perturbed at a given point. This gave a moving turbulent 'spot' which was completely repeatable. The lifetime, and interactions of the spots were then easily studied using hot wire anemometers. The authors conclude that the turbulent spot (which can occur naturally at surface imperfections etc.) is a basic element of a turbulent boundary layer, that the eddies retain their relative locations as the spot grows and that a synthetic boundary layer produced by spots differs from the natural layer produced randomly and may have some engineering applications. Some discussion of the paper is included. Discussion of the paper is included. (K.R.)