The work is significant because it places five related profiles within one computational framework rather than drawing together results obtained under different domains, meshes, boundary conditions or flow settings. The investigators used identical computational domains, mesh characteristics, turbulence modelling, boundary conditions, inlet velocity and angle of attack for all five airfoils. The simulations treated the flow as steady, incompressible and turbulent, with the standard k–ε turbulence model, a uniform velocity inlet, a pressure outlet and a no-slip wall at the stationary airfoil surface. This common setup was intended to make geometry, rather than numerical methodology, the main source of variation in the comparison.

The computational model used a 100-millimetre chord and operated at a Reynolds number of approximately 2.2 × 10⁵. The researchers described this as a low-speed aerodynamic regime relevant to applications such as small aircraft and unmanned aerial vehicles. They generated the airfoil geometries with the standard NACA four-digit formulation and applied local mesh refinement around each airfoil to resolve near-wall flow and steep velocity gradients. A structured hybrid mesh dominated by eight-node hexahedral elements was used for the three-dimensional domains, whose outer boundaries were placed sufficiently far from the airfoils to reduce blockage effects.

Before comparing the five configurations, the team conducted a five-level mesh sensitivity test on the NACA 2408. The grids ranged from 84,620 cells with 20-millimetre elements to 417,380 cells with 8-millimetre elements. The predicted lift-to-drag ratio rose as the mesh was refined but approached a stable value: increasing the grid from 286,740 to 417,380 cells changed the ratio by only 0.10 percent. The researchers consequently selected the 286,740-cell mesh as a compromise between numerical resolution and computational cost, then applied it consistently to all five airfoils. The reported primary outputs were dimensional lift and drag forces, with L/D calculated directly from those forces rather than from lift and drag coefficients.

The results showed that the balance between lift and drag differed markedly across the family. NACA 2408 produced a reported lift force of 7,369.2 newtons, drag of 338.2 newtons and L/D of 21.79. NACA 2415 generated slightly less lift than NACA 2412, at 8,524.8 newtons, but substantially more drag, at 448.1 newtons, giving it a much lower L/D of 19.02. NACA 2418 and 2421 generated the lowest reported lift forces, 4,290.9 and 5,290.7 newtons, respectively, and also had the lowest drag values, 130 and 153.5 newtons. Their L/D ratios reached 33.01 and 34.47, but neither matched NACA 2412.

The pressure results also emphasized that absolute static pressure alone cannot explain the aerodynamic ranking. NACA 2408 and 2415 recorded the highest reported static pressures, 103,034 and 103,035 pascals, while NACA 2418 and 2421 recorded 101,242 and 101,178 pascals. NACA 2412 occupied an intermediate position at 102,553 pascals while achieving the highest lift and L/D. The investigators’ streamline analysis described faster flow over the upper surface and comparatively higher pressure below the airfoil, producing a pressure differential associated with lift. The relatively smooth streamlines and limited wake disturbance were interpreted as evidence of stable flow development at the selected zero-degree condition, although the study did not test a broad range of angles of attack or stall conditions.

To add experimental evidence, the researchers fabricated a geometrically similar 1:20-scale NACA 2412 model using high-resolution three-dimensional printing. The model, with a measured mass of 0.026 kilograms, was tested in a low-speed, low-turbulence subsonic wind tunnel with a 250-by-250-millimetre test section and an operating range of 2 to 40 metres per second. The experimental calculations used a reference area of 0.0907 square metres, while pressure points on the upper and lower surfaces were used to examine static-pressure distribution. The printed model preserved the selected airfoil’s camber, leading-edge radius and thickness distribution, allowing physical testing without the material cost and fabrication difficulty of a full-scale wing section.

The wind-tunnel model measured a lift force of 20.6 newtons, drag of 0.5828 newtons, static pressure of 101,432 pascals and an L/D ratio of 35.34. For a like-for-like numerical comparison, the team also ran a CFD case using the 1:20 geometry and the experimental flow conditions. That scaled simulation predicted 21.43 newtons of lift, 0.5920 newtons of drag, 101,513 pascals of static pressure and an L/D ratio of 36.20. The reported differences between scaled CFD and experiment were 3.87 percent for lift, 1.55 percent for drag, 0.08 percent for static pressure and 2.36 percent for L/D.

Those close numerical-experimental differences support the reported aerodynamic behaviour of NACA 2412, but they must be interpreted within an important limitation. Scaling the chord by 1:20 preserved geometric similarity, not dynamic similarity, and the model therefore operated at a substantially lower Reynolds number than the 100-millimetre CFD configuration. The physical measurements consequently provide complementary evidence rather than a strict Reynolds-number-matched validation. The researchers noted that small discrepancies could also arise from manufacturing tolerances, measurement uncertainty, flow non-uniformity, support interference and differences between numerical assumptions and practical tunnel conditions. The comparison was also limited to one selected profile, one zero-degree simulation condition, steady incompressible flow and five related airfoils.

Within that scope, the study identifies NACA 2412 as the most aerodynamically efficient of the five profiles in the common CFD comparison. Its leading result reflects a combination of high reported lift and comparatively low drag, not a universal advantage for every operating condition. The authors say further work should examine a wider range of Reynolds numbers and angles of attack, compressibility and advanced turbulence models such as SST k–ω, RSM, LES and DES. They also identify transient calculations, three-dimensional wing geometries, aeroelastic effects, fluid–structure interaction, optimisation, machine learning and multi-objective design as avenues for work that would better represent practical aircraft. The present results therefore offer a controlled baseline for preliminary airfoil selection, not a final determination of performance across real flight envelopes.

Subject of Research: Comparative low-speed aerodynamic performance of five NACA 24-series airfoils using CFD and wind-tunnel testing.

Article Title: Comparative aerodynamic analysis of NACA 24-series airfoils at low Reynolds number using computational fluid dynamics and wind-tunnel experiments

Article References: Sadaq, S. I., Kumar, P., Agarwal, A., Wa Kalenga, M. K., Yelamasetti, B., Saniya, S., & Singh, V. D. (2026). Comparative aerodynamic analysis of NACA 24-series airfoils at low Reynolds number using computational fluid dynamics and wind-tunnel experiments. Frontiers in Mechanical Engineering, 12, Article 1987465. https://doi.org/10.3389/fmech.2026.1987465

Image Credits: AI Generated

DOI: 10.3389/fmech.2026.1987465

Keywords: aerodynamics, NACA 2412, NACA airfoils, computational fluid dynamics, wind-tunnel testing, low Reynolds number, lift-to-drag ratio, airfoil efficiency, unmanned aerial vehicles, Comparative, aerodynamic, analysis