Abstract
<jats:p>Laminar flow behavior over airfoil surfaces plays a critical role in determining the aerodynamic efficiency in subsonic flight, particularly through its influence on viscous drag and boundary-layer development. The thickness of an airfoil affects the pressure-gradient distribution along the surface and can therefore influence laminar flow stability and aerodynamic performance. Quantitative investigations on isolating the thickness as an independent geometric parameter under consistent numerical conditions remain limited. This study presents a numerical investigation into the influence of airfoil thickness on laminar flow characteristics at subsonic Mach numbers. A symmetric NACA 0012 airfoil was adopted as the baseline geometry, and systematic thickness variations were introduced while maintaining a constant chord length and camber characteristics. The aerodynamic performance was analyzed using XFLR5 predictions combined with computational fluid dynamics (CFD) simulations performed using a Reynolds-averaged Navier–Stokes framework with transition-sensitive modeling. The analysis was conducted under subsonic operating conditions representative of low-speed aerodynamic applications. The results showed that increasing the airfoil thickness strengthened the adverse pressure gradients on the suction surface, leading to increased boundary-layer sensitivity and drag penalties. Thinner configurations exhibited delayed pressure recovery and improved aerodynamic efficiencies within the investigated operating range. CFD flow-field visualization further illustrated the relationship between pressure gradient development, wake growth, and aerodynamic performance trends. The findings provide insights into the sensitivity of laminar flow behavior to airfoil thickness and highlight the efficacy of the XFLR5 and CFD approaches in early-stage airfoil design and aerodynamic evaluations.</jats:p>