Published October 26, 2023
Suction/Leeward Surface: The suction or leeward surface of the blade is the surface facing away from the wind (hence leeward). On average it experiences a lower pressure than the pressure/windward surface, meaning that the resultant lift forces acts from the pressure surface towards this surface, in the direction of the wind. The boundary layer flow over the suction surface is critical for blade performance and loads as aerodynamic stall originates on this surface. This is why we find aerodynamic upgrades such as vortex generators on the suction surface.
Pressure/Windward Surface: The pressure or windward surface of the blade is the surface facing towards the wind (hence windward). On average it experiences a higher pressure than the suction/leeward surface. The boundary layer flow over the pressure surface is less important for blade performance issues such as stall, but it still holds great potential to yield blade performance improvements. This is why we find aerodynamic upgrades such as Gurney flaps on the pressure surface.
The suction and pressure surfaces have very different aerodynamic characteristics, which results in different aerodynamic upgrades being appropriate. This knowledge allows engineers to fine-tune blade and upgrade designs to ensure that the blade extracts the maximum energy from the wind.