Existence and analysis of anti-symmetric super-coherent states in a wake behind a body of revolution at Re_D=5000

In this talk, we investigate the existence of two super-coherent states in a wake behind a body of revolution with a blunt trailing edge, characterized by the opposite direction of a slow azimuthal rotation in the wake in a mean sense. The rotation originates in the recirculation region behind the blunt trailing edge, and manifests itself as a very-low-frequency (VLF) motion with a Strouhal number St~0.001, two orders of magnitude lower than the vortex shedding frequency. The flow also possesses a “cork-screw like” helical structure in the intermediate wake. A targeted perturbation of an instantaneous flow field resulted in a reversal of the orientation of the VLF motion in the near wake, as well as the helix orientation in the intermediate wake. In this talk, we examine the properties of both states using various modal analysis techniques, and present conditionally averaged properties of the flow given the state, as well as unconditionally averaged properties when the two states are combined together.