Computational and experimental investigation of lower-surface dimple effects on NACA 0015 airfoil aerodynamics

Aerodynamic efficiency is fundamentally limited by flow separation at moderate angles of attack, where boundary layer detachment precipitates lift degradation and drag augmentation. In response to growing energy imperatives, this investigation advances passive flow control methodologies through systematic analysis of surface-modified symmetrical airfoils. This study examines a modified NACA 0015 airfoil incorporating indentations at five discrete chordwise positions along the lower surface. Through ANSYS CFD simulations employing the k-ω SST turbulence model, this work systematically evaluates aerodynamic performance variations of lower surface dimple modified airfoil across multiple angles of attack and chordwise locations. Results reveal that strategically positioned dimples profoundly influence aerodynamic efficiency, with 70 % chord position yielding 13.5 % greater lift-to-drag ratio at 7° AoA. While trailing-edge dimples (90 % chord) improve high-angle performance (7.25 % L/D increase at 10° AoA), this benefit is offset by 16.86 % degradation at 4° AoA. The optimal lift-to-drag ratio for 70 % chord length at 7° AoA is attributed to delayed flow separation, corroborated by static pressure contour analysis. Experimental validation via wind tunnel testing at 3 m/s further substantiates these computational finding. This study contributes to the rather underexplored arena of the lower surface modified dimples providing systematic evidence that these modifications can concurrently enhance lift and mitigate drag. The findings consolidate dimple engineering as a viable zero-energy solution for separation control.