Numerical study of iced airfoils with horn features using large-eddy simulation

Separated flowfields around two iced airfoils with horn features near stall are numerically studied using wall-modeled large-eddy simulation. The iced airfoils are the GLC305 airfoil with rime ice 212 and the NLF0414 airfoil with glaze ice 623. A grid-quality-based hybrid central/upwind scheme is applied for numerical flux computation. The close agreement between the computed lift, drag, and surface pressure distribution and the experimental results illustrates the capability ofthe present method. In particular, the current method can accurately predict the Kelvin–Helmholtz instability of a free shear layer. The statistical results, instantaneous flowfields, pressure fluctuations, and characteristic frequencies are investigated. Both flowfields are dominated by separation bubbles. The bubble length increases with the angle of attack according to a quadratic relation. A strong-fluctuation region in the flowfield grows rapidly at high angles ofattack, especially near stall. High- and low-frequency peaks are found in the initial and further downstream regions ofthe free shear layer, respectively. The high frequency is caused by the Kelvin–Helmholtz instability andvortex shedding.Thelow frequency mightbe causedby the vortex merging in the further downstream region of the free shear layer.