Direct numerical simulations of forced and unforced separation bubbles on an airfoil at incidence

Abstract

Direct numerical simulations (DNS) of laminar separation bubbles on a NACA-0012 airfoil at Rec= 5 × 104 and incidence 5° are presented. Initially volume forcing is introduced in order to promote transition to turbulence. After obtaining sufficient data from this forced case, the explicitly added disturbances are removed and the simulation run further. With no forcing the turbulence is observed to self-sustain, with increased turbulence intensity in the reattachment region. A comparison of the forced and unforced cases shows that the forcing improves the aerodynamic performance whilst requiring little energy input. Classical linear stability analysis is performed upon the time-averaged flow f..