Revisit of the Breakdown Characteristics of the Leading-Edge Separation Vortices over a Delta Wing

The present study revisited the phenomena of the leading-edge separation vortices over a high angle-of-attack delta wing and investigated the transition process between the bubble-type and the spiral-type vortex breakdown by numerical simulations. The proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) were also performed to understand the phenomena further. The results indicated that the interactions of the leadingedge separation vortex and the wing’s upper surface near the initiation point of the vortex breakdown caused the vortex breakdown type transition at the angle of attack (α) of 37 degrees. On the other hand, such interference seen at α = 37 degrees was not observed in the flow at α = 30 degrees.