Bifurcations and chaos transition of the flow over an airfoil at low Reynolds number varying the angle of attack

The study of an airfoil at low Reynolds number regime was found to be a typical problemwhere the inception of bifurcations leads the flow evolution from a stationary or periodicbehaviour to a purely chaotic one. The present work extends the present literature wherenumerical investigations of the flow field past two-dimensional symmetric airfoils wereperformed by fixing the incidence and changing the Reynolds number (Re). Conversely,here the Reynolds number was fixed at Re = 10 0 0 and the angle of attack (AoA) variedfrom 0 o to 90 o . Different flow Modes and bifurcation phenomena are detected and, in ad-dition, new non-linear phenomena are also identified. The latter consists of tripling periodregimes and its bifurcations up to chaotic conditions. Moreover, for increasing AoA, an in-verse transition from chaotic to periodic regimes is also observed. An in-depth study ofthese different flows is provided and new links with the time evolution of the forces act-ing on the airfoil, as well as with the wake structures observed, are offered. Phase portraitdiagrams are evaluated through the time records of the lift force in order to highlight theeventual presence of limit cycles in the solutions. Accurate numerical simulations are per-formed with a Vortex Particle Method in a two-dimensional framework, using high spatialresolutions to solve in detail both the near-field and the far-field regions.