High Amplitude Stall Flutter Simulations of a NACA 63(3)418 Aerofoil

Large eddy simulations are conducted for a pitching NACA 63(3)418 airfoil section at a reduced frequency of K=0.4 and a moderate chord-based Reynolds number, Rec=100,000. Perturbation starting times are varied parametrically to investigate both the qualitative and quantitative differences in the dynamic stalling processes over a single pitching cycle. It is found that Kármán vortex shedding associated with an initially static airfoil primarily interferes with the LEV detachment and dynamic lift stall as per large variations in the post-stall unsteady aerodynamic loading. Monitored LEV trajectories and computed LAVD fields both confirm this notion and are utilized to link this phenomenon to the status of a TEV. Interestingly, the respective LEV trajectory paths leading up to dynamic lift stall tend to coalesce at a singular point before a rapid growth in spatial deviation. This event appears to be weakly dependent on the LEV circulation during its maturation stage. Finally, the LEV morphology is investigated near its detachment location through several morphometric quantifiers such as the area, aspect ratio, and eccentricity. It is found that the LEV morphology undergoes a similar contraction in parametric variations for the aspect ratio and eccentricity.