الملخص الإنجليزي
Abstract:
This study has traced the surface Roughness effect on NACA 4412 airfoil. In addition, research revised Aerodynamic characteristics with and without the impact of applied surface roughness at different heights on the lower surface of the Airfoil and investigated the differences. This study employed Numerical and Experimental approaches to affirm the results.
Numerical solution was performed using Fluent Ansys code. Two sets of spherical aligned surface roughness patterns were applied to the lower surface face of the NACA 4412 airfoil and then compared the first and second sets to a smooth Airfoil. The first set has ten designed surface roughness heights (ks) from 0.05 mm to 0.5 mm. The second set possesses four different surface roughness with ks from 1 mm to 4 mm. The simulation was conducted in turbulent high subsonic incompressible flow with 4.39 x 106 > Re ≥ 8.79 x 106, 10 km Altitude, and k-w model. Each model was tested at 0º, 5º, and 10° angles of attack (a) and run-in velocities: 150 m/s, 200 m/s, 250 m/s, and 300 m/s at steady level flight.
The experimental study was conducted in a horizontal low subsonic wind tunnel at sea level air properties. Four models were tested with a smooth upper surface and a lower surface with roughened ks = 0.258 mm, ks =0.45 mm, ks =0.125 mm, and ks =0.129 mm. Each model sampled at a- 0º, 5º, 10º for speeds V-20 m/s, 23 m/s, 27 m/s, 30 m/s, and 35 m/s. Boundary Layer Thickness (BL) was also measured for each model Experimentally to indicate the effect of surface roughness on BL thickness. Airfoil models compared to the smooth Airfoil (ks 0mm) numerically. The ks=0.05 mm (first set) and ks=1 mm (second set) had shown the best outcomes. Lift Coefficient C increased at a=0° but set but increased significantly for the second. For the First set model with ks=0.05 mm, the C₁/CD at a = 5º increased compared to the smooth airfoil model by 13.08%, 13.73%, 14.3%, and 12.2% at velocities: 150 m/s, 200 m/s, 250 m/s, and 300 m/s. For the second set model of ks = 1 mm, CL/CD decreased at a = 5º compared to the smooth airfoil by: 4.91%, 5.9%, 6.35%, 7.52% at velocities: 150 m/s, 200 m/s, 250 m/s, and 300 m/s. Power required to operate the airfoil with ks=0.05 mm at a = 5º decreased by 12.78%, 13.53%, 13.95%, and 12.50% for velocities: 150 m/s, 200 m/s, 250 m/s, and 300 m/s respectively.
Roughened experimental models were compared with a smooth model (k, 0mm). The airfoil model with ks = 0.125 mm revealed CL's best results at a = 0°. Airfoil with ks = 0.045 mm had the slightest decrease in C₁ values for all angles of attack 0º, 5º, and 10° and recorded the best values at 10º with 2.32%, 4.24%, 4.98%, 5.53%, and 6.28% for wind tunnel velocities: 20 m/s, 23 m/s, 27 m/s, 30 m/s, and 35 m/s. Cp values decreased the lowest for ks 0.125 mm at a 0° by 11.95%, 11.67%, 11.39%, 11.18%, 10.88% for velocities: 20 m/s, 23 m/s, 27 m/s, 30 m/s, and 35 m/s. C1/CD improved the best at a = 0° by 1.288%, 12.76%, 12.31%, 12.30%, and 12.29% for velocities: V = 20 m/s, 23 m/s, 27 m/s, 30 m/s and 35 m/s respectively. Power conservation improved the best for Airfoil with ks=0.125 mm compared to the smooth Airfoil and documented 12.53%, 12.54%, 12.04%, 12.16%, and 12.32% for velocities of 20 m/s, 23 m/s,27 m/s, 30 m/s, and 35 m/s respectively. Finally, BL thickness is proven to be sensitive to surface roughness change. By increasing ks, the transition from laminar to turbulent BL shifts upstream.
These results suggested that low-cost designated rounded surface roughness film be applied at the lower surface of NACA 44the 12 Airfoil to get better aerodynamic characteristics.
