Transitions to chaos in the wake of an axisymmetric bluff body

This Letter aims at understanding the dynamical process that leads to the onset of chaos in the flow past a blunt-based axisymmetric bluff body. On the basis of direct numerical simulations, conducted for Reynolds numbers ranging from 100 to 900, we show that the flow undergoes multiple transitions, successively giving rise to the SS, RSPa, RSPb, RSPc and RSB wake states. In particular, the RSPc state, revealed in this work via long-term computations, is characterized by intermittent vortex stretching denoting the onset of chaos before the symmetry breaking and the occurrence of the RSB state. -- Highlights: ► We performed long-term Direct Numerical Simulations of the flow past an axisymmetric bluff body. ► We reveal the existence of a new wake mode. ► We show that this mode triggers chaos before the loss of planar symmetry in the wake. ► We decipher the transitions leading to this mode through the description of the wake structures.