Investigating the aerodynamic performance of an UAV

Abstract: The aerodynamic performance of any airborne vehicle is an important characteristic to be considered during the concept development process. Lift and drag forces are the two most important aspects of aerodynamics that dictates vehicle efficiency. As these forces depend on various conditions, evaluating the performance at the intended flight condition is necessary. As the experimental investigations are extremely expensive, computational methods are used to find the performance characteristics of a vehicle in the early design stages. The main focus of this thesis is to find the aerodynamic parameters of an UAV, lift coefficient (Cl) and drag coefficient (Cd) at a predefined flight state and further investigate the trim performance in turn flight state. Two types of computational methods were used namely Panel Methods i.e., Vortex Lattice Method (VLM) and Computational Fluid Dynamics (CFD). These methods differ by computational time and accuracy. Investigations were performed to two UAV models namely UAV1 andUAV2 where both models have minor differences in design. Both VLM and CFDwere used to investigate the performance of UAV1. This was done to find the maximum capability of VLM, which is computationally cheaper. A trim analysis was also performed to find additional parameters to aid the comparison of VLM and CFD. Apart from investigating UAV1 at the required flight states, investigation was also performed at near stall to find the performance of UAV1 in worse flight condition. A comparison of UAV1 and UAV2 was then made to find the best flight states where an UAV can fly fulfilling the designer requirements. UAV2 was then simulated to find the trim condition of a level flight by deflecting the elevator control surfaces in turn flight state. The results from the analysis showed that VLM provides reasonable results within its limitations. From the CFD results, both the UAV’s have sufficient Cl, but the Cd of UAV1 is approximately twice the Cd of UAV2. The turn analysis of the UAV2 showed that at a higher angle of attack, UAV2 can bank at a large bankangle without losing the level flight condition.