Experimental and numerical analysis of NREL S823 airfoil with auxiliary airfoil integration

Abstract

ABSTRACT This study explores the potential for using an auxiliary airfoil to improve the aerodynamic characteristics of an NREL (National Renewable Energy Laboratory) S823 airfoil designed explicitly for small-scale wind turbines. The experimental investigation is carried out on a standard S823 airfoil (S823(S)) and an S823 with the inclusion of an auxiliary airfoil (S823(A)), at different angles of attacks (0º-20º) and different low wind speeds (4–10 m/s). The result shows that the S823(A) model consistently outperforms the S823(S) model in terms of lift-related metrics. It exhibited a 10% increase in CL values. Specifically, the S823(A) model achieved a maximum CL value of 1.284 at 10 m/s, which is an 8% improvement over the S823(S) model’s maximum of 1.191 at the same wind speed. Besides, the S823(A) model demonstrated superior performance in the sliding ratio, with values consistently higher by approximately 11%, 9%, 10%, and 14% at wind speeds of 4 m/s, 6 m/s, 8 m/s, and 10 m/s, respectively. Moreover, numerical simulations were carried out for both the models at similar conditions, which reveal that using an auxiliary airfoil reduces flow separation on the pressure side, along with well controlling the Turbulence Kinetic Energy (TKE) dissipation of the S823(A) model. Moreover, the airfoil flow visualization reveals that the auxiliary airfoil promotes smoother airflow separation, especially near the trailing edge of the airfoil. This reduces turbulence and improves the overall stability and controllability of the airfoil across different AoAs. Overall, the S823(A) model offers superior aerodynamic performance, improved lift-to-drag ratio, and better control characteristics across a range of angles of attack compared to the S823(S) model that improves the overall aerodynamic performance of the main airfoil.