Nonlinear lift behavior in medium-aspect-ratio wings at low Reynolds numbers: An extension of the Polhamus–Lamar model

The aerodynamic behavior of low- and medium-aspect-ratio (LAR/MAR) slender wings operating at low Reynolds numbers is critical for the design of modern unmanned aerial vehicles. The widely used Polhamus–Lamar model (PLM) effectively captures the lift characteristics of LAR wings by representing vortex and potential lift components. However, the existing PLM approaches may lose accuracy at higher angles of attack (AoA) and increasing ARs. This study introduces a simple modification to the PLM that (1) reduces model nonlinearities, (2) preserves the vortex and potential lift components, and (3) extends its applicability to MAR wings and higher AoA. The proposed model is assessed through computational fluid dynamics (CFD) simulations, wind tunnel experiments, and comparison with published experimental data. The CFD visualizations qualitatively illustrate the evolution of vortical and separated-flow structures as AoA increases. Experimental and numerical results show that the proposed parameterization improves the representation of nonlinear lift attenuation relative to classical PLM-based predictions within the studied conditions. The proposed methodology extends the useful range of the PLM structure while preserving its fundamental decomposition into potential and vortex-related lift terms.