Computational aeromechanics of annular wings unnamed aerial vehicle

Computational evaluation of the aerodynamic and propulsive characteristics of several annular wing-propeller configurations to assess the effect of propeller on the aerodynamic performance of the annular wing for application in UAVs is the focus of this work. This research work establishes the potential of annular wing-propeller configuration as a propulsive unit for unconventional UAVs. Higher propulsive efficiencies of ducted propellers make them suitable to propel UAVs whereas annular wings provide higher aerodynamic efficiencies than conventional wings. A cambered Clark-Y airfoil section for the annularwing and a 3-blade propeller with NACA 4412 airfoil section combine to form the annular wing-propeller system investigated in this work. Effect of parameters such as the tip clearance ratio and the position of the propeller within the annular wing for various advance ratios and angles of attack of the annular wing-propeller system are analyzed using RANS & LES models. Resulting velocity fields upstream and downstream, thrust and torque of the annular wing-propeller system are computed. Computed results are also validated against the experimental and computational results reported in the literature. The compressibility effects are also assessed for propeller advance ratios for which the propeller blade tips may exceed Mach 0.3. The relative performance of various annular wing-propeller configurations is studied in depth. LES captures the compressibility effects even with incompressible flow solver predicting realistic flow field in the vicinity of Mach 0.3. LES is found to resolve the flow field more intricately than RANS. Additionally, comparison of solo and contra-rotating propellers within the annular wing is also presented. Contra-rotating propeller-annular wing system is found to be superior to the solo propeller-annular wing configuration for UAV applications. The design of the annular wing-propeller configuration so developed is further investigated dynamically for an Annular Wing UAV in hover and forward flight. Longitudinal static stability analysis to compute the static margin and neutral point of the complete UAV with and without propeller effect assisted greatly in attaining the final annular wing UAV configuration. The mission statement of the annular wing UAV includes vertical take-off, hover, swivelling of the propulsive unit and forward flight. Propeller powered annular wing UAVs thus have a huge potential as a VTOL aircraft.by Abheeti GoyalM.Tech