Evolution of Large Eddies in Compressible Shear Layers

Planar Laser-Induced Fluorescence (PLIF), in a double/offset-exposure arrangement, is applied in a supersonic shear-layer
facility to examine the role of large-scale structures in shear layer mixing at high Mach numbers. The research is
motivated by the advent of scramjets (supersonic combustion ramjets) and is very relevant to supersonic jet noise.
Structure geometry, propagation, and evolution are examined. The convective velocity Uc of the structures is measured by
applying 2D cross-correlation schemes to the digital images. The experiments reveal the existence of fast and slow modes of Uc.
This directly impacts supersonic jet noise and may have profound influence on mixing and combustion at high Mach numbers.

Shown below is an image showing the evolution of a supersonic eddy