Effect of Surface Roughness Size on the Skin Friction Drag for NACA0012 Airfoil

The generated lift and drag forces for any airfoil represent the crucial parameters that measure the airfoil’s performance. The high lifting force to drag force at different angles of attack is the target of design to gain wide application at high performance. In term of the generating lifting force, the speed, and density of air is dominant and the curvature of the airfoil plays a role too. In terms of drag force, the development of the boundary layer can consider the main source of the drag. The boundary layer development depends on many parameters such as air velocity, density, viscosity, and surface roughness. Skin friction is related to surface roughness and the point where the separation can provoke. In this work, a regular roughness has been added to the surface of NACA 0012 to investigate the drag force performance. A wire mesh with different holes per inch is used (120, 200). The velocity gradient, velocity profile, lift, drag, and pressure distribution are measured at different angles of attack. The results show a slight improvement in velocity gradient for the mesh 200 holes per inch compared to a smooth surface and 120 holes per inch. As a consequence of the velocity gradient, a small reduction in drag force is obtained.