Wake Instabilities behind an Axisymmetric Bluff Body at Low Reynolds Numbers
This paper aims at understanding the mechanisms that lead to the onset of chaos in the wake of blunt based axisymmetric bluff body. On the basis of direct numerical simulations, conducted for Reynolds numbers ranging from 100 to 800, we show that the flow undergoes multiple transitions, successively giving rise to the Steady State SS and to the Reflectional Symmetry Preserving RSP a , RSP b and RSP c wake states. In particular, the RSP c state is characterized by intermittent vortex stretching denoting the onset of chaos and the potential occurence of a third instability that superimposes to the first and second instability associated with state RSP a and RSP b respectively. Interestingly, the reflectional symmetry plane that characterizes the RSP states is still retained. Hence, chaos is triggered before the symmetry breaking and the occurence of the Reflectional Symmetry Breaking RSB state observed at higher Reynolds numbers.
KeywordsVortex Vorticity Pebble
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