Coherent motions in a turbulent wake of an axisymmetric bluff body

The wake flow past an axisymmetric body of revolution at a diameter-based Reynolds number $Re=u_{\infty }D/\nu =5000$ is investigated via direct numerical simulation. study focused on identification coherent vortical motions and the dominant frequencies in this flow. Three are identified wake: vortex shedding motion with frequency $St=fD/u_{\infty }=0.27$ , bubble pumping $St=0.02$ very-low-frequency (VLF) originated very near $St=0.002$ – $0.005$ . pattern demonstrated to follow reflectional symmetry breaking mode, whereas loops shed alternatingly from each side plane, but subsequently twisted tangled, giving resulting structure helical spiraling pattern. confined recirculation region result Görtler instability. VLF related stochastic destabilisation steady symmetric mode manifests itself as slow, precessional barycentre. $St=0.005$ also detectable intermediate may be associated low-frequency radial flapping shear layer.