Successive bifurcations in a fully three-dimensional open cavity flow
Résumé
The transition to unsteadiness of a three-dimensional open cavity flow is investigated
using the joint application of direct numerical simulations and fully three-dimensional
linear stability analyses, providing a clear understanding of the first two bifurcations
occurring in the flow. The first bifurcation is characterized by the emergence of
Taylor–Görtler-like vortices resulting from a centrifugal instability of the primary
vortex core. Further increasing the Reynolds number eventually triggers self-sustained
periodic oscillations of the flow in the vicinity of the spanwise end walls of the
cavity. This secondary instability causes the emergence of a new set of Taylor–Görtler
vortices experiencing a spanwise drift directed toward the spanwise end walls of the
cavity. While a two-dimensional stability analysis would fail to capture this secondary
instability due to the neglect of the lateral walls, it is the first time to our knowledge
that this drifting of the vortices can be entirely characterized by a three-dimensional
linear stability analysis of the flow. Good agreements with experimental observations
and measurements strongly support our claim that the initial stages of the transition
to turbulence of three-dimensional open cavity flows are solely governed by modal
instabilities.
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