Aerodynamic Analysis of a Small Scale Powered Autonomous Aircraft Employing a KFm2 Modified NACA 2412 Airfoil

Powered autonomous aircraft can fly under an automatic control system without intervention from a pilot, which is significant for firefighting applications in today’s world. Small, capable, and cost-effective, they can be used to survey an area in more detail and closer to the ground than traditional aircraft and can even deliver humanitarian or fire-suppression payloads. In this work, a small-scale powered autonomous aircraft employing a KFm2 modified NACA 2412 airfoil is designed and analyzed. The conventional airfoils generally follow a teardrop shape, with the interior structure drastically increasing weight. A flat plate design reduces the weight, however, it drastically increases the parasitic drag from exposed avionics components on the surface and does not produce useful lift. The KFm2 airfoil modification is a hybrid of a flat plate and a conventional airfoil (NACA 2412), reducing the weight while maintaining the lift capability of the original airfoil. The KFm2 modified airfoil has a stepped profile where the step is located at the 50% chord length, and the height of the step is 7% of the chord length. The flow field characteristics and aerodynamic performance of this powered autonomous airplane are investigated numerically at different angles of attack (0°, 3°, 5°, 7°, 9°, and 11°) and velocities (6.1 m/s, 12.2 m/s, and 18.3 m/s). A similar study is performed on a small-scale aircraft with an unmodified NACA2412 airfoil to compare the effect of airfoil design at different velocities and angles of attack. For numerical modeling, ANSYS Fluent is employed and the SST K-Omega turbulence model is used for turbulence modeling. A grid independence study is performed and validation study is conducted against experimental data in literature. The results indicate the advantage of the hybrid geometry of the airfoil by increasing the lift force while reducing weight, making it a prime candidate for small powered autonomous aerial vehicles.