Modifying NACA6409 Airfoil Configuration to Improve Aerodynamic Performance in Low Wind Speeds

This paper will modify the design of the NACA6409 airfoil model to improve aerodynamic performance in operating conditions with low wind speeds from 2m/s to 5m/s corresponding to the normal operating values of small capacity wind turbines. Some main parameters such as maximum thickness (MT), position of maximum thickness (MTP), maximum cumber (MC) and position of maximum cumber (MCP) will be changed to find the most suitable airfoil configuration. The redesign processes will be performed on XFLR5 software using Full Inverse Design Method (FIDM), then analyzed by Panel Method (PM). The reliability of the PM is also determined and is acceptable for the analytical models used in this research. The most important result obtained from the analytical models is the lift coefficient
$(\mathrm{C}_{1})$
to drag coefficient
$(\mathrm{C}_{\mathrm{d}})$
ratio
$(\mathrm{C}_1/\mathrm{C}_{\mathrm{d}})$
of the airfoils according to the angles of attack (AoA) under different wind speed conditions. From the obtained results, it is shown that the best modified airfoil gives a maximum
$\mathrm{C}_1/\mathrm{C}_{\mathrm{d}}$
value that is about 1.205 times to 4.522 times higher than the original NACA6409 airfoil, the values are equivalent to some of the best airfoils published by other research groups.