Sensitivity analysis and control of the wake behind a cylinder
Event details
| Date | 15.06.2011 |
| Hour | 11:30 |
| Speaker | Dr Simone Camarri |
| Location |
GR C0 01
|
| Category | Conferences - Seminars |
Many studies have been dedicated to understand the behavior of the wake behind a circular cylinder, considered as a paradigmatic bluff body flow, and many of them focus on the primary and secondary instabilities. In this respect, sensitivity analyses based on adjoint methods have been widely applied to investigate the primary instability of the wake. In particular, the structural sensitivity analysis of the linear stability problem has shed light on the process which gives rise to a self-sustained global mode in the wake,localizing the instability mechanism in two lobes symmetrically placed on the boundaries of the recirculation bubble behind the cylinder [Giannetti & Luchini, JFM 581 (2007)]. More recently [Maquet et al., JFM 615 (2008)], additional information has been added by the sensitivity analysis of the primary instability with respect to modifications of the base flow, caused by the introduction of a localized steady force. This analysis suggests also passive control strategies of the instability itself. In this seminar, a work will be concisely presented which generalizes the previously mentioned analysis to the secondary instability of the cylinder wake (three-dimensional instability of the wake), i.e. to the case of a globally unstable base flow which is also periodic in time. It will be shown that the structural sensitivity analysis of the associated linear problem allows, in this case too, the localization of the core of the 3D instability, which is even more concentrated in the near wake with respect to the case of the primary instability. The sensitivity of the 3D instability to a base flow modification, obtained by the application of a localized steady force,is also investigated and results will be shown.If allowed by the remaining time, a strategy to design a feedback control of the vortex shedding instability based on the sensitivity analysis of the instability itself will be also presented. The proposed control design strategy assumes that realistic sensors and actuators are available for the controller; results of its application to the flow behind a confined square cylinder will be shown.
Practical information
- General public
- Free
Contact
- Dr. Valerio Iungo