A SIMPLIFIED THEORY FOR UNSTEADY AERODYNAMIC FORCES ACTING ON AN AIRFOIL FLYING ABOVE SEA-WAVES

A simplified theoretical method based on the quasi-steady wing theory was proposed to study the unsteady aerodynamic forces acting on an airfoil flying in non-uniform flow. Comparison between the theoretical results and the numerical results based on nonlinear theory was made. It shows that the simplified theory is a good approximationfor the investigation of the aerodynamic characteristics of an airfoil flying above sea-waves. From on the simplified theory it is also found that an airfoil can get thrust from a wave-disturbed airflowand thusthe total dragis reduced. And the relationship among the thrust, the flying altitude, the flying speed and the wave parameters was worked out and discussed.