Enhanced prediction of three-dimensional finite iced wing separated flow near stall

Abstract

Icing on three-dimensional wings causes severe flow separation near stall. Standard improved delayed detached eddy simulation (IDDES) is unable to correctly predict the separating-reattaching flow due to its inability to accurately resolve the Kelvin-Helmholtz instability. In this study, a shear layer adapted subgrid length scale is applied to enhance the IDDES prediction of the flow around a finite NACA 0012 wing with leading edge horn ice. It shows that using the new length scale contributes to a more accurate prediction of the separated shear layer (SSL). The predicted reattachment occurs earlier as one moves towards either end of the wing, and the computed surface pressure distributions agree well with the experimental measurements. In contrast, standard IDDES severely elongates surface pressure plateaus. For instantaneous flow, the new length scale helps to correctly resolve the rollup and subsequent pairing of vortical structures due to its small values in the initial SSL. The vortical motion frequencies increase when moving towards the wing tip due to the downwash effect of the tip vortex. In comparison, the excessive eddy viscosity levels from the standard IDDES delay the rollup of spanwise structures and give rise to “overcoherent” structures.