Structure of turbulent shear flows - A new look

Experimental evidence is reviewed which indicates that nonrandom structures play a major part in the development of such turbulent shear flows as mixing layers, boundary layers, and the early regions of jets and wakes, and that the organized structures have a form that is characteristic of a particular type of turbulent shear flow. The presence of organized structure in turbulent flow is illustrated by photographs of several mixing layers. The progress of the structures along the mixing layer is plotted against time on an x-t diagram. Means of describing organized structures are discussed, and their formation, lifetime, and influence on the flow are examined.