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

Event details
Date | 19.02.2025 |
Hour | 15:15 › 16:15 |
Speaker | Dr Artur Gesla |
Location | |
Category | Conferences - Seminars |
Event Language | English |
Abstract:
Rotor-stator flows are a popular prototype for instabilities in closed flows. They 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. In this talk I will explore numerically possible scenarios for the existence of circular rolls. Various branches of self-sustained solutions will be identified using harmonic balance method and self-consistent method (SCM). The SCM will prove to be an essential tool to identify an exceptionally steep branch emanating from a critical point. The subcritical chaotic regime will be shown to support the memoryless finite lifetime dynamics of a super-exponential mean lifetime scaling. The receptivity of the flow will be investigated using the resolvent analysis consisting of a singular value decomposition of the resolvent matrix and the direct numerical simulation. Various forcing protocols will be considered to best imitate the experimental conditions. I will show that the circular rolls observed experimentally do not origin from the instability of the base flow but are rather a response of the system to external forcing. Presented results suggest that the circular rolls are the combined effect of the high forcing gain and the roll-like form of the leading response of the linearised operator
Biography:
Artur Gesla received the Aerospace Engineering Bachelor's degree from Warsaw University of Technology, Poland, in 2019 followed by the Computational Mechanics Master's degree together with the Bavarian Graduate School of Computational Engineering honours degree from Technische Universität München, Germany, in 2021. His doctoral thesis "Numerical investigation of the dynamics of
an axisymmetric rotor-stator flow" prepared at Sorbonne Université and in LISN laboratory, France, has been defended in November 2024.
an axisymmetric rotor-stator flow" prepared at Sorbonne Université and in LISN laboratory, France, has been defended in November 2024.
Practical information
- General public
- Free
- This event is internal
Organizer
- HEAD unit
Contact
- Prof Eunok Yim