This work presents the numerical study of the convective heat transfer of a flow over non-homogeneous rough surfaces obtained from ice accretion experiments on an airfoil. This supports the study of inflight ice accretion over aircraft components, a phenomenon that poses a risk to the safe operation of aircraft. The study of the convective heat transfer is of utter importance since it dictates the ice growth rate on a surface, especially in icing conditions favoring glaze ice formation. Therefore, icing codes, which permit the numerical simulation of ice accretion, require the proper modeling of the convective heat transfer on the boundary layer of a flow under the influence of non homogeneous roughness. This allows to accurately obtain ice geometries to subsequently study their effects on aircraft aerodynamics. The numerical study is performed on experimentally obtained ice shapes on an asymmetric airfoil. The experiments are carried out in the Braunschweig Icing Wind Tunnel, involving supercooled water droplets which follow Appendix C conditions of the EASA regulations. The obtained ice shapes were digitized via the photogrammetry method for their subsequent analysis and preparation for the numerical simulations. Embedded LES (ELES) is performed for the numerical study, which allows the simulation of unsteady 3D turbulent behavior in the region surrounding the ice geometry, typically located on the stagnation point of the airfoil, while the rest of the fluid is simulated via a RANS approach. The results obtained from the ELES are analyzed and compared to the ones of fully turbulent RANS simulations (SST with roughness model), from which several observations are elaborated. First, ELES shows that the wall shear stress and heat flux do not possess a direct correlation in the presence of roughness, in contrast to smooth surfaces, which show a linear correlation between the skin friction coefficient with the Stanton number, as observed in experiments found in the literature. On the other hand, RANS results show a ...
Numerical and experimental investigations on rough airfoil in icing conditions
2023-01-01
Hochschulschrift
Elektronische Ressource
Englisch
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