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This paper deals with the numerical simulation of the two-dimensional, incompressible, steady air flow past an airfoil for a solar powered unmanned aerial vehicle (UAV) with internal propulsion system. This airfoil results from a NACA 2415 four digits family base airfoil modification [7] and has a propulsive outlet with the shape of a step on the suction surface. The analysis involved the airfoil’s aerodynamic performance which meant obtaining lift, drag and pitching moment coefficient curves as a function of the angle of attack (AOA) for the condition where the engine of the UAV is turned off called the gliding condition and also for the blowing propulsive condition by means computational fluid dynamics. The computational domain has been discretised using a structured mesh of 188 x 200 tetrahedral elements. The RNG k-ε model is utilized to describe the turbulent flow process as it was followed in [5]. The simulations were held at a Reynolds number of 300000. Results allowed obtaining lift and drag forces and pitching moment coefficient and also the location of the separation and reattachment points in some cases by means of the wall shear stress on the suction surface as well as velocity contours and streamlines for both conditions at different angles of attack, from 0 to 16 degrees with the smallest increment of 4 degrees. Finally, results from both cases were compared and the influence of the propulsive flow on the aerodynamic characteristics of the airfoil has been analysed turning out that it improves significantly the performance of the airfoil reaching values up to 1,8 times in terms of lift at high angles of attack.
[5] Rhie C.M., Chow W.L., Numerical Study of the Turbulent Flow Past an Airfoil with Trailing Edge Separation, AIAA Journal, Vol. 21, No. 11, 1983.
[7] Velazquez L., Nožicka J, Kulhanek R., Oil and Smoke Flow Visualization past Two-Dimensional Airfoils for an Unmanned Aerial Vehicle, in The 11th Asian Symposium of Visualization. Niigata, Japan. 2011.
