DUCTED FAN FOR VTOL UAV

Abstract

Reynolds-averaged Navier-Stokes (RANS) based computational fluid dynamics (CFD) simulations have been conducted to investigate the aerodynamics of a typical ducted-fan in forward flight at angles of attack below stall. The duct is modelled as an annular wing with a Clark Y airfoil profile. The fan is represented by a simple actuator disc. Results for the unpowered duct are validated against annular wing experiments and theory. Based on the simulation results, simple equations for the ducted-fan force and moment coefficients are formulated by semi-empirically extending existing annular wing theory. The semi-empirical ducted-fan aerodynamics model is then employed in a flight dynamics model of a simplified ducted-fan vehicle based on the ST Aerospace FanTail 5000 unmanned aerial vehicle (UAV). Both linear and nonlinear flight simulations are conducted for the model vehicle in forward flight.