Numerical study of the effect of backward-facing steps on airfoil’s surface on position of laminar-turbulent transition using global stability analysis

The paper presents the results of a numerical study of the effect of surface irregularity in the form of a backward-facing step on the position of the onset of natural (caused by the convective instability of Tollmien-Schlichting waves) laminar-turbulent transition on the laminar airfoil NLF(1)-0416. The study is performed using a technique based on Global Stability Analysis previously developed by the authors and adapted to this type of flows in the present work. It is shown that for a smooth airfoil these results are in good agreement with the experimental data on the transition position in a wide range of angle of attack. For the airfoil with a backward-facing step, a parametric study was conducted, which resulted in quantitative data on the dependence of the transition position on the step height.