Experimental and Numerical Investigation of the Influence of Leading Edge Tubercles on S823 Airfoil Behavior

Abstract

Investigating the role of leading edge tubercles on the aerodynamic behavior of S823 airfoil tailored for wind turbine applications has been the forefront of the study. The aerodynamic characteristics of S823 airfoil effectuated by leading edge tubercles are ascertained at Reynolds number Re=200000 which is the usual operating range of most of the small-scale wind turbines. Firstly, the study elucidates the numerical investigation of baseline airfoil and later modified airfoils exhibiting different amplitude A and wavelength λ of the sinusoidal leading edge tubercles represented as A07W50, A12W50, and A07W25. The aerodynamic characteristics of the airfoils at Re=200000 and angles-of-attack ranging from 00 to 200 are evaluated numerically through k-ω SST turbulence model using ANSYS FLUENT® software package. A preliminary comparison of the computational data shows that the coefficient of lift Cl of all the modified airfoils was visibly superior to the baseline model across the angles tested. A07W50, A12W50 and A07W25 registered 20.6%, 26.2%, and 8.7% increase in the Cl values as compared to the baseline model. Contrasting to the Cl values, the aerodynamic efficiency Cl/Cd of the baseline model was slightly better but only across the pre-stall regime and later culminated with a sudden hard stall. Promisingly, this type of hard stall was not true for the tubercled models that demonstrated a more gradual and restrained stalling characteristic, thus showcasing superior performance in the post stall envelope that was never observed for the baseline model. Based on the outcomes, A07W50 model that displayed better aerodynamic characteristics was eventually fabricated and experimentally tested for its performance in a low speed wind tunnel. The numerical results of A07W50 were in good agreement with the experimental results. The overall results of the study prove beyond any point of doubt that tubercles indeed aid in improving the aerodynamic characteristics by enhancing the lift Coefficient Cl, rendering soft stalling nature and extending the scope of operation for the airfoil under study. Finally, the study positively confirms that leading edge tubercles very much play a significant role in passively augmenting the fluid dynamic characteristics of S823 airfoil and also qualify them to be a competitive passive flow control device.