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Influence of the inlet velocity profile on the flow stability in a symmetric channel expansion

par Debuysschère, Robin ;Siconolfi, Lorenzo;Rimez, Bart ;Gallaire, François;Scheid, Benoît
Référence Journal of fluid mechanics, 909, A13
Publication Publié, 2021-01-01

Article révisé par les pairs

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Résumé :

In a channel flow with a sudden expansion, whether for three-dimensional (3-D) pipe and channel flows, or for two-dimensional (2-D) channel flow, it is known that increasing the Reynolds number beyond a critical value induces a symmetry breaking Pitchfork bifurcation. The linear stability analysis of the symmetric steady solution enables the to be determined efficiently and thus the influence of the expansion ratio , defined as the ratio between upstream and downstream diameter regarding the expansion, to be explored. In this study, we investigate the behaviour of the flow after 2-D sudden expansions while varying the and the inlet flow profile, e.g. corresponding to a transition profile between a plug and a Poiseuille flow that could be reached for a flow after a sudden constriction upstream. Results demonstrate that imposing a plug flow at the inlet gives a higher than any other profile and that the concomitant recirculation zones are shorter. We show that these results can be rationalized using basic convection-diffusion arguments.