Numerical Study of the Effect of Backward-Facing Steps on an Airfoil’s Surface on the Position of the Laminar–Turbulent Transition Using Global Stability Analysis

This 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 (T–S) waves) laminar–turbulent transition (LTT) on the laminar airfoil NLF(1)-0416. The study is performed using a technique based on global stability analysis (GSA) previously developed by the authors and adapted to this type of flow in this study. 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 angles of attack. For the airfoil with a backward-facing step, a parametric study is conducted, which results in quantitative data on the dependence of the transition position on the step height.