Abstract— A numerical simulation was performed using a vortex method to investigate the fluid mechanical interferences of two tandem airfoils at variable angles of attack. The distance between two airfoils (distance ratio) in a vessel or submarine and the range of angle of attack were chosen based on the shape of the vessel or submarine. A symmetrical airfoil NACA0012 was used, and the Reynolds number was Re = 3.8 × 105. The distance ratio was L/C = 5.0, and different attack angles α = 0°, ±5°, ±10°, and ±15° were considered. The flow characteristic of an initial stage was observed in this study. The flow pattern in each case was obtained via calculations, and the variation in the fluid force in each case and that in the overall lift coefficient were examined. The mutual interference of two airfoils indicated that the rapid variation in the overall lift coefficient occurs at the early stage.