Hysteresis of two-dimensional flows around a NACA0012 airfoil at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si47.svg"><mml:mrow><mml:mi mathvariant="italic">Re</mml:mi><mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo><mml:mn>5000</mml:mn></mml:mrow></mml:math> and linear analyses of their mean flow.

Two-dimensional numerical simulations of the flow around a NACA0012 profile at Reynolds number Re=5000 show that unsteady periodic flows reach different saturated states when increasing or decreasing angle attack between 7∘ and 8∘. Within this range, lift signal shows co-existing period-doubling, as wake undergoes substantial change in character from standard von-Kármán vortex street. Results experiments water channel also indicate topology but slightly lower angles α=6°. A discussion discrepancy experimental results is proposed light about three-dimensional transition behind bluff bodies airfoils. Finally, eigenvalue resolvent analyses time-averaged are used to investigate two-dimensional transitions further. While peak energetic amplification obtained frequency single state, double observed for states, second one being state not compute flow. This behaviour characterizes analysis period-doubled although less pronounced.