Analysis of the expanding process of turbulent separation bubble on an iced airfoil under stall conditions

摘要

The expanding process of turbulent separation bubble induced by a horn ice on the leading edge of an airfoil for business jet was investigated numerically with IDDES. Through comparing with the experiment results of critical stall condition, the fidelity of method for detailed simulation of ice-induced separation was verified firstly. Then the separation bubble under post-stall conditions was investigated in the aspects of both the features of averaged static flowfield and the behaviors of transient shear-layer vortices. The averaged results manifested that during the stall process, the bubble expanded with stretching and deformation for reattachment line and turbulence region were shifted towards trailing edge and spread continually. The corresponding extending and descending of pressure plateau with weak pressure gradient resulted in an early but mitigated stall pattern consequently. From the transient flowfield, it was observed that the entire evolution process of bubble was driven by the hairpin-type vortices generated from the shedding shear-layer with K-H instability. The propagation direction of these shear-layer vortices was affected by the entrainment of external flow. Under the post-stall condition, the motion of vortices towards the wall was delayed with the increasing of incidence and the interaction between vortices and wall was weakened correspondingly, which leaded the gradual decrease of reattachment effect and the continuous expanding of recirculation region. (C) 2021 Elsevier Masson SAS. All rights reserved.