Large-Eddy Structures in a Turbulent Mixing Layer

Structures of turbulent mixing layers, especially of large-eddies, are investigated by visual observation by means of a smoke-wire method. Mixing layers are produced by a screen set perpendicular to freestream in a test section. Flow features of the mixing layers are observed by means of motion pictures taken with a 16 mm high-speed camera. Results show that 1) large-eddies form from the amplification of unstable small-amplitude waves, 2) vortex pairing process as well as the growth of large-eddies without vortex pairing, found by Hernan & Jimenez, play an important role in the growth of the turbulent mixing layer, and 3) the mixing layers are fundamentally two-dimensional.