Structural characteristics of supersonic mixing enhanced by introducing streamwise vortices

The characteristics of structural evolution and mixing process of supersonic flow downstream a lobed mixer are experimentally investigated using nanoparticle-based planar laser scattering technique. The development and evolution of Kelvin-Helmholtz vortices, large-scale streamwise vortices, and transverse structures are clearly exhibited. The interaction of Kelvin-Helmholtz vortices and streamwise structures accelerates the momentum transport of upper and lower streams in the flow transition region. The streamwise vorticity engulfs transverse structures, causing them to deform so that they are bulged at the lobe trough, which can favor molecular mixing. The emergence of small-scale streamwise structures and horseshoe vortex in the interfacial area of the two streams plays an important role in entraining the surrounding fluid from both sides of the interface into mixing region.