Investigation of coherent structures and dynamics using POD and DMD of a separated airfoil subjected to ZNMF jet forcing N. A. Buchmann, V. Kitsios, C. Atkinson and J. Soria Abstract Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) analysis are undertaken on the unsteady separated flow field on a NACA-0015 airfoil with periodic zero-net-mass-flux (ZNMF) jet forcing at the leading edge. The flow configuration is a NACA-0015 air- foil at an angle of attack α = 18 o and a chord based Reynolds number of Re= 3 · 10 4 . This study presents experimental data for the forced flow case and recovers the dominant coherent structures and temporal characteristics that describe the evolution of the velocity perturbation. The dominant fre- quencies are identified by the DMD eigenvalues and the corresponding spatial modes are compared to the dominant POD modes. 1 Introduction One of the primary aims of flow control is to prevent boundary layer separa- tion and as such extend the effective operational range of engineering devices such as diffusers, compressors, turbines and airfoils. In the case of airfoils, period excitation has been shown to delay separation and hence increase lift over a range of Reynolds numbers and angles of attack (AoA) [2, 6]. The present experimental flow configuration is a NACA-0015 with zero-net-mass flux (ZNMF) jet forcing at the leading edge with a chord based Reynolds Re ≡ U ∞ c/ν =3 · 10 4 , c = 100mm and 18 o AoA. The experiments are conducted in a horizontal water tunnel using high repetition Particle Image N. A. Buchmann, V. Kitsios, C. Atkinson and J. Soria Laboratory of Turbulence Research in Aerospace and Combustion, Department of Me- chanical and Aerospace Engineering, Monash University, VIC 3141, AUSTRALIAN, e-mail: nicolas.buchmann@monash.edu J. Soria Department of Aeronautical Engineering, King Abdulaziz Universitym Kingdom of Saudi Arabia 1