Diagnosing unsteady separated flows
Event details
| Date | 25.03.2014 |
| Hour | 14:00 › 15:00 |
| Speaker |
Prof. Karen Mulleners, Institute of Turbomachinery and Fluid Dynamics, Leibniz University of Hannover, Germ Bio: Karen Mulleners was born in Tongeren, Belgium, in 1983. She started her university education in Belgium at the University of Hasselt, then transferred to Eindhoven University of Technology in the Netherlands to complete her bachelor's and master's degrees in applied physics with specialisation in physics of transport in fluids. She received a PhD degree in mechanical engineering from the university of Hannover in Germany in 2010. Her doctoral thesis was completed under the supervision of Prof. Markus Raffel at the German Aerospace Center in Göttingen in the field of helicopter aerodynamics. From 2010 to 2012, she held postdoctoral positions at the German Aerospace Center in Göttingen and at the University of Hannover. Since 2012, she is an assistant professor at the department of mechanical engineering at the University of Hannover. Her research interests include modern methods of coherent structure based flow diagnosis that serve to bridge the gap between the generation and interaction of vortices and technically relevant quantities, such as aerodynamic forces and power output, by reference to insect flight and wind turbine rotor blade aerodynamics. |
| Location | |
| Category | Conferences - Seminars |
Abstract : Flow separation on lifting surfaces is a commonly encountered, mostly undesired, unsteady flow condition that occurs when a critical angle of attack is exceeded. The unsteady separation process comprises a series of complex aerodynamical phenomena, including transition to turbulence, shear layer instability, and large-scale vortex formation. A detailed understanding of the chronology and causality of events during the development of unsteady flow separation is desirable to develop effective flow control measures and effcient analytical and computational flow models. In this regard, time-resolved flow field measurements were combined with flow diagnostic methods - including Eulerian vortex detection methods, Lagrangian coherent structure analysis and proper orthogonal flow field decomposition - to analyse the spatiotemporal evolution of coherent structures during static and dynamic stall on a two-dimensional airfoil. With this coherent structure based diagnostics, the physical mechanisms and parameters controlling initiation, growth, and subsequent detachment of large-scale stall vortices were identified and characterised. Fundamental importance was attributed to the behaviour of the shear layer and the associated time scales were determined directly from the time-resolved velocity field measurements. Following up on this work, modern methods of coherent structure based flow diagnosis are being refined to bridge the gap between the generation and interaction of vortices and technically relevant quantities, such as aerodynamic forces and power output, by reference to insect flight and wind turbine rotor blade aerodynamics. Future challenges lie in the development of scalable and efficient means of data reduction to handle vast amounts of high resolved experimental and computational data of unsteady flow phenomena with regard to wind and water energy conversion systems and flow control.
Practical information
- General public
- Free
Organizer
- IGM-GE
Contact
- Géraldine Palaj