Effect of initial shape and geometric characteristics of airfoils in discrete adjoint-based optimization

This study investigates the role of initial geometry and constraint formulation in discrete adjoint-based airfoil optimization for small wind turbine (SWT) applications. Aerodynamic shape optimization is carried out using newly Generalized k – ω (GEKO) turbulence model (RANS) at Re = 5 × 10 5 and an angle of attack of 7°. Particular emphasis is placed on comparing a standard with an enhanced constraint-handling strategy designed to preserve feasible geometric deformation. The results demonstrate that initial geometry and constraint treatment both strongly influences convergence behavior and achievable aerodynamic gains. While thinner airfoils converge more rapidly, thicker profiles achieve larger improvements in C l / C d when appropriate constraints are enforced. Cambered geometries exhibit higher baseline efficiency, whereas symmetric sections show greater adaptability during optimization. The enhanced constraint-handling approach consistently outperforms the standard method by preventing over-thinning and enabling sustained performance improvements. These findings identify constraint formulation as a critical design parameter in adjoint-based airfoil optimization and provide practical guidance for robust SWT blade design.