Aerodynamic modeling and optimization of a blended-wing-body transitioning UAV

In this paper, the aerodynamic analysis and optimization of a new transitioning unmanned aerial vehicle (UAV) is presented. This UAV is capable of VTOL, hover, efficient (fixed-wing type) forward flight, and flight states in-between. The overall configuration comprises a blended-wing-body (which facilitates desirable weight distribution and flight efficiency), with two rotor arms mounted at the two wing tips using span-wise shafts; the arms can rotate about the span-wise axis, and each contains two propellers at its two ends (4 propellers in total). A Vortex Lattice (VL) method is used to perform the aerody- namic analysis; appropriate airfoil choices and number of panels in the VL method are established. The lift and drag forces computed are used to estimate forward flight range and endurance (assuming battery-powered flight), by leveraging typical momentum theory formulations. Since, a hybrid UAV such as BITU is expected to provide the flexibility of flying in varying wind conditions, diverse wind scenarios are taken into consideration here. Uncertainties associated with wind conditions are addressed by taking a typical and worst case scenario perspective, and introducing carefully tailored redundancies during the mod- eling and optimization formulation process. Optimization studies, using a mixed-integer Particle Swarm Optimization algorithm, are performed to separately maximize forward- flight range, subject to various aerodynamic and geometric constraints. Interestingly, the optimization converges to distinct designs under calm, windy, and stormy wind scenarios, with flight ranges going from about 163 km to about 54 km.