Evaluation of NACA4412 smooth and denticle-covered airfoils using blade element momentum theory

Abstract The present study investigated the impact of using a denticle-covered NACA 4412 airfoil inspired by the Short?in Mako shark dermal denticle surfaces on the aerodynamic performance of a horizontal axis wind turbine. This was compared to the same airfoil with smooth surfaces. The airfoil was tested in a wind tunnel with twenty-seven (27) static pressure taps on two 355 by 184 mm airfoils to determine the lift and drag coef?icients at different wind speeds of 6.0 m/s and 9.0 m/s with an angle of attack ranging from −11.6 to 17.2 degrees. Nine pressure sensors were utilized to assess the static pressure distribution at various angles of attack. Initial ?indings indicated that the lift and drag ratio was higher for the smooth airfoil at angles of attack greater than 1.03 degrees. However, the denticle-covered airfoil showed a higher lift and drag ratio at angles of attack ranging from −9.77 to less than 1.03 degrees. Additionally, the study calculated the power output and power coef?icient using the blade element momentum theory proposed by DNV/Ris0 and GH Bladed in a three-bladed wind turbine with a rotor radius of 9.80 m and rated rotational speed of 60 rpm. The calculation results showed that the smooth airfoil generated over 25.65% more power than the denticle-covered airfoil when the wind speed was above 7.5 m/s. In contrast, the denticle-covered airfoil performed better at lower wind speeds, speci?ically between 4.0 m/s and 6.5 m/s. Maximum power coef?icients of 0.231 and 0.248 were achieved for smooth and denticle-covered airfoils when the upstream wind speeds were 8.0 m/s and 6.0 m/s, respectively.