Aerodynamic Performance Analysis of a UAV using CFD and VLM

Abstract: Computational Fluid Dynamics has become a versatile product development tool, bringing many advantages to the conceptual design phase of products, and is being used for a wide variety of applications. In this thesis, the aerodynamics of a UAV with internal radar has been investigated. UAV is an acronym for Unmanned Aerial Vehicle, that is an aircraft which is flown with no human pilot onboard the aircraft, maneuvering the flight controls. The studies conducted throughout this thesis aimed at conducting numerical simulations of two UAV wing designs, through the utilization of the Vortex Lattice Method and Computational Fluid Dynamics. A number of different flight cases were investigated for comparing the two wing designs with respect to their aerodynamic characteristics, as well as a sustained turn analysis for the second UAV wing design. The analyses were conducted by importing provided UAV CAD-models into the numerical software, setting up appropriate grids, and running the simulations at the flight cases of interest. The results gathered from the simulations concerning the first wing design demonstrated favorable flight characteristics at lower angles of attack, although at angles of attack greater than 5°, flow separation was apparent. Regarding the results concerning the second wing design, it could be flown at greater angles of attack without experiencing flow separation, while decreasing the total drag of the UAV. For the sustained turn analysis concerning the second wing design, the aircraft generated sufficient lift at desired load factors, for maintaining its altitude however, it could not reach a trimmed state despite larger deflection angles of the ruddervators. Therefore the center of gravity position of the UAV was manipulated for sustaining the turns at desired load factors. Pressure contour plots were generated from the CFD simulations from which it could be determined that the front and nose of the aircraft could be further redesigned for decreasing aerodynamic drag.