Attributes of the large-scale coherent motions in a shear layer

PIV observations in a shear layer have been used to identify and characterize the discrete large-scale coherent motions (LSCMs) in the nominally self-preserving region: x/θ_o ≈ 450–610, of a shear layer. The LSCMs are given an objective definition wherein their centers are the (swirling flow pattern) nodes of the velocity-vector field as seen by an observer in the Galilean reference frame translating at an appropriately defined reference velocity. The statistical attributes of size, lateral location, and separation between these coherent motions (that exist in a single image) as well as their characteristic vorticity magnitude 〈ω_max〉 are reported.