Spatio-temporal stability analysis of the separated flow past a NACA 0015 airfoil with ZNMF jet control

摘要

The current paper presents the spatio-temporal stability analysis of an instance of laminar separation, with the intention of determining the most appropriate forcing frequency to initiate flow reattachment. The flow configuration is a NACA 0015 airfoil at an angle of attack (a) where laminar separation occurs immediately downstream of the leading edge. A zero-net-mass-flux (ZNMF) jet, normal to the surface and spanning the entire leading edge is used to achieve reattachment. The uncontrolled flow field was generated numerically in [5] using a three-dimensional (3-D) Large Eddy Simulation (LES) and compared to the complementary water tunnel experiments of [22]. Initial simulations of the uncontrolled case agree well with the PIV and force measurements. The stability analysis presented herein is undertaken on the mean velocity field of the LES. The frequency determined by the stability analysis to maximise spatial growth of the disturbance is finally compared to the forcing frequency that maximised lift enhancement in the experimental study.