Multibody Simulation of Flexible Aircraft with Variable-Sweep Wingtips

An investigation into variable-sweep wingtips for use on flexible aircraft is presented. A suitable flexible multibody formulation is first developed, which also includes prescribed rotation kinematics between flexible beam elements. This allows for the simulation of dynamic actuated wingtips for use within an aeroelastic simulation framework. Automatic differentiation is used to compute derivatives, thus allowing for a very convenient implementation for a range of multibody constraints. The use of the unsteady vortex lattice method for modeling swept wings where the paneling is misaligned with the flow is also investigated, all combined to give an analysis tool for flexible aircraft dynamics with actuated swept wingtips. Numerical results on representative configurations investigate the potential advantages of this unconventional solution, with gust load alleviation from sweeping back the wingtips observed when compared to the reference configuration. The effect of wingtip sweep on the aeroelastic stability characteristics of the aircraft is explored, which is seen to affect both the flutter speed and mechanism. Lastly, it was found that there are potential uses for dynamically sweeping the wingtips in flight, with a roll and pitching maneuver being demonstrated using opposing and symmetric sweeps, respectively.