PIV of air flow over a step and discussion of fluctuation decompositions

The experimental method of PIV (Particle image velocimetry) is used to study the air flow over a forward facing step creating shear layer between the outer flow and the recirculation bubble. This layer decays into vortices, which are highlighted by using Reynolds (temporal) decomposition or Agrawal (spatial) decomposition. The later can be tuned to different-sized structures, and, additionally, their energies roughly follow the Kolmogorov -5/3 law