Eunok Yim

Séminaire exceptionnel
EPFL

Open flows such as jets, separation bubbles and mixing layers, can be encountered in a wide variety of situations from small scale laminar to large scale turbulent flows. Generally, such flows are characterized by instabilities resulting in the observable unsteady dynamics. To describe their dynamics and nature, various linear and non-linear approaches have been explored. The linear stability theory tells us mathematical description of the characterizing phenomena but it fails quickly as soon as the perturbation becomes big enough to have nonlinear effect. While non-linear approach such as DNS is accurate but sometimes it can be too costly and difficult to analyse. Therefore, a simple quasi-linear model taking the mean flow and fluctuation interaction into account has been proposed by Mantic-Lugo, Arratia, Gallaire (2012). This model so-called self-consistent model successfully described the non-linear saturation dynamics via modification of the mean flow through the Reynolds stress of the fluctuation. In this talk, the further extension of the model into turbulent flow will be first presented. In the second part, the transition to turbulence in rotor boundary layer in rotor-stator cavity will be discussed. This classical subject has been extensively studied since it's similarity to the air craft swept wing crossflow. However, the precise measurement and thorough DNS shows the discrepancies. We will show the importance of the mode interactions.