Large-eddy simulations of complex aerodynamic flows over multi-element iced airfoils

Abstract

Large-eddy simulations (LESs) of flows over two types of iced airfoils with three multi-elements are performed to investigate the aerodynamic characteristics and complex interactions between flows generated from slat, main, and flap elements. The two iced airfoils are considered under supercooled large droplet (SLD) and non-SLD conditions. A good agreement of the mean properties between our numerical and previous experimental data demonstrates that our LES method provides an accurate solution of the complex flows around iced airfoils., whereas it is not for unsteady Reynolds-averaged Navier–Stokes (URANS) data that is simulated independently. For the iced airfoils under the SLD and non-SLD conditions, the aerodynamic degradation is found compared to that of a clean airfoil because the separation bubbles (SBs) induced by ice accretion change shear layer (SL) trajectory shed from the slat cusp, leading to a severe reduction in mass flow. Furthermore, we show that the flow interactions near the slat gap play a crucial role in determining the flow characteristics on main and flap elements (e.g., flow separation). Although strong flow interactions are observed for the non-SLD case because of the presence of upwind horn-shaped ice, the smaller gap distance of the SLD case leads to a larger lift loss. The unsteady features of SBs on the upper surfaces of the slat and main elements under the non-SLD condition are characterized by the power spectral density (PSD) of the pressure fluctuations with multiple peaks at low and high frequencies.