Reestablishing turbulence intensity as a critical parameter for NACA2414 airfoil performance at low Reynolds number: A computational study

Small wind turbines operate under low Reynolds number conditions, where improving aerodynamic efficiency becomes crucial due to the adverse inflow characteristics. This study systematically investigates the isolated effect of a broad range of inflow turbulence intensities on the aerodynamic performance of a NACA2414 airfoil at a Reynolds number of 10 5 using two-dimensional finite volume Unsteady Reynolds-Averaged Navier-Stokes simulations. The computational domain was discretized as a structured grid and a Realizable k-ɛ model was utilized as the closure model in ANSYS Fluent. Three turbulence intensities (1%, 5%, and 10%) were examined over angles of attack spanning from 0° to 30°. Significant reduction in lift-to-drag ratio was observed pre-stall with a contrasting enhancement post-stall with increasing turbulence intensities. In addition, onset of stall was delayed. Statistical analysis, employing ANOVA, based on 800 design points from 0.1% to 20% confirmed turbulence intensity as a significant parameter governing lift-to-drag ratio explaining 42.5% of the associated variance. The effect was substantial at lower angles of attack and diminished at higher angles as post-stall conditions dominated. The present work demonstrates a non-linear and regime-dependent influence of turbulence intensity over NACA2414 airfoil performance at a transitional flow regime, directly relevant to small-scale wind turbine operation. Rotor-level analysis using a validated blade element momentum model further indicates a reduction in mechanical power output with increasing turbulence intensity. The findings establish turbulence intensity as a critical design parameter for low-Reynolds number wind turbine airfoils. • Explored turbulence intensity impact on NACA2414 airfoil at a Reynolds number of 10 5 . • Behavior in pre-stall and post-stall regions at higher turbulence intensity are discussed. • Patterns in lift, drag coefficients and boundary layer development are discussed. • Established turbulence intensity as a critical parameter through a comprehensive ANOVA test. • Blade Element Momentum analysis revealed a 59.23% reduction in mechanical power as turbulence intensity increased from 1% to 10%.