The effect of cavity modified stepped geometry on aerodynamic performance of an airfoil at a low Reynolds number.

This article focuses on an experimental investigation of the effects of modified stepped geometries with cavity structures on the pressure surface of a NACA0012 airfoil at a Reynolds number of 1 × 10^5. Using force measurements, titanium dioxide (TiO₂)-based surface oil flow visualization, and velocity measurements, the study evaluates aerodynamic performance changes, flow structures, and wake region modifications for various step configurations. Results indicate that all stepped modifications, particularly the D2 model with a medium cavity size, increase the lift coefficient by up to 13.22% compared to the base model, though drag coefficients slightly increase. The study also reveals that cavity diameter and depth significantly influence wake width, wake centerline shifts, and flow structures such as wavy reattachment lines and recirculation zones, with deeper cavities (D3 model) notably altering flow behavior in the stepped region. These findings contribute to understanding how cavity-modified step geometries affect aerodynamic performance and flow control on airfoils.