RANS CFD Simulation, Experimental Validation and Flow Control of Low-Speed NACA 2412 Aerofoil with Vortex Generators for Stall Delay in UAV Applications

Unmanned Aerial Vehicles (UAVs) operating at low Reynolds numbers (Re 10⁵–10⁶) encounter aerodynamic challenges distinct from those of large manned aircraft — particularly the formation of laminar separation bubbles on the upper aerofoil surface at moderate angles of attack that precipitate abrupt stall with minimal pre-stall warning, threatening mission continuity and airframe safety. The NACA 2412 aerofoil, widely adopted for small UAV and agricultural drone wing sections due to its well-documented thickness and camber characteristics, exhibits stall at approximately 15° under clean surface conditions at Re 3×10⁵ — a stall angle insufficient for the high-angle manoeuvres required in precision agricultural spray operations and urban air mobility corridors. This paper presents a comprehensive CFD simulation study using RANS k-ω SST and DDES turbulence models in Ansys FLUENT 2023 R2, validated against wind tunnel measurements in the IIT Kanpur 1.4m×1.0m low-turbulence (Tu=0.04%) tunnel across α=−4° to 20°, for the clean NACA 2412 and three vortex generator (VG) configurations — triangular delta, counter-rotating rectangular, and co-rotating asymmetric arrays at 5% chord station. Lift and drag coefficients, Cp distribution, and boundary layer velocity profiles from hot-wire anemometry constitute the validation dataset. The counter-rotating VG array achieves CLmax extension to 1.62 (+9.5% over clean baseline) and stall angle delay to 18° (+3°). Grid convergence, turbulence model sensitivity, and drag breakdown analysis are systematically presented.