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Jun 17 – 18, 2024
Europe/Paris timezone
Journées Écoulements & Fluides - Saclay

Noise sustained versus self-sustained structures in rotor-stator flow

Jun 17, 2024, 12:20 PM
Présentation orale Présentations


Artur Gesla (Sorbonne Université, LISN-CNRS)


Rotor-stator flows are known to exhibit instabilities in the form of circular and spiral rolls. While the spirals are known to emanate from a supercritical Hopf bifurcation, the origin of the circular rolls is still unclear. A quantitative scenario for the circular rolls as a response of the system to external forcing is suggested. Two types of axisymmetric forcing are considered: bulk forcing (based on the resolvent analysis) and boundary forcing using direct numerical simulation. The linear gain curve shows strong amplification at non-zero frequencies following a pseudo-resonance mechanism. The optimal energy gain is found to grow rapidly with the Reynolds number (based on the rotation rate and interdisc spacing $H$) in connection with huge levels of non-normality. Presented results suggest that the circular rolls observed experimentally are the combined effect of the high forcing gain and the roll-like form of the leading response of the linearised operator. For sufficiently strong forcing amplitudes, the nonlinear response is consistent with the self-sustained
states found recently for the unforced problem.

Primary authors

Artur Gesla (Sorbonne Université, LISN-CNRS) Yohann Duguet (LISN-CNRS) Patrick Le Quéré (LISN-CNRS) Laurent Martin Witkowski (Université Lyon 1)

Presentation materials

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