Print Email Facebook Twitter Boundary Layer Separation Title Boundary Layer Separation: Diagnostics and Control Author Michelis, Theodorus (TU Delft Aerodynamics) Contributor Scarano, F. (promotor) Yarusevych, S. (promotor) Kotsonis, M. (copromotor) Degree granting institution Delft University of Technology Date 2017-09-25 Abstract The research presented in this thesis focuses on boundary layer separation and, more specifically, on the related physical mechanisms, such as laminar to turbulent transition, with a vision towards effective separation control. The work is divided in three parts, each corresponding to a different separation scenario. The supporting data is experimental, obtained by means of particle image velocimetry. The first and major part regards the phenomenon of laminar separation bubbles. The spatial and temporal response characteristics of a flat plate laminar separation bubble to impulsive forcing are first investigated in order to shed light on the processes of flapping and bursting. The impulsive disturbance is introduced twodimensionally with a dielectric barrier discharge plasma actuator. The disturbance develops into a wave packet that causes rapid shrinkage of the bubble in both upstream and downstream directions. This is followed by bubble bursting, during which the bubble elongates significantly, while vortex shedding strength in the aft portion of the bubble is reduced. Duration of the recovery of the bubble to its unperturbed state is independent of the forcing amplitude. At the same time, linear stability analysis shows that the growth rate and the frequency of the most unstable mode decreases for increasing forcing amplitude. Throughout recovery, growth rates are directly proportional to the shape factor, indicating that bursting and flapping mechanisms are driven by altered stability characteristics due to variations in incoming disturbances. It is found that the stability of the flow changes only when disturbances interact with the shear layer breakdown and reattachment processes, supporting the notion of a closed feedback loop. Subject Boundary layer separationDBD plasma actuators To reference this document use: https://doi.org/10.4233/uuid:f5ecca35-71f6-4c99-92e8-a3004113fa53 ISBN 978-94-92516-82-4 Part of collection Institutional Repository Document type doctoral thesis Rights © 2017 Theodorus Michelis Files PDF Michelis_2017.pdf 25.54 MB Close viewer /islandora/object/uuid:f5ecca35-71f6-4c99-92e8-a3004113fa53/datastream/OBJ/view