LES of turbulent jet in cross flow: Part 2 - POD analysis and identification of coherent structures

The LES based POD analysis was also conducted in 3D. The 3D POD analysis results based on the first two POD modes show a full ability to directly visualize details of the relationship between the counter-rotating vortex pair (CVP), the hanging vortex and the wake vortices. POD reconstruction shows that the CVP originates from the hanging vortex formed at the lateral sides of the jet. It also shows that the shedding process involving oscillation of the jet core is responsible for the creation of wake vortices and that the wake vortex originates from the hanging vortex, but grows quickly by “sucking up” the wall boundary layer fluid and vorticity.