What is dynamic stall and how is it analyzed for helicopter and wind turbine applications?

Dynamic stall occurs when airfoils undergo rapid pitching, causing delayed stall, formation of a leading edge vortex (LEV), and momentary lift increase followed by dramatic lift loss and negative pitching moment when the LEV convects. Analysis methods include: Leishman-Beddoes type semi-empirical models tracking LEV formation and convection; CFD with transition modeling for accurate separation prediction; and specialized wind tunnel testing with oscillating rigs. Critical for helicopter rotor blade fatigue (cyclic loads) and wind turbine performance. Key parameters are reduced pitch rate and amplitude. Active flow control and blade design modifications can mitigate severity.