  Unsteady Lifting-Line Theory (ULLT) is a low order method capable of modeling
interacting unsteady and finite wing effects at low computational cost. Most
formulations of the method assume inviscid flow and small amplitudes. Whilst
these assumptions might be suitable for small-amplitude aeroelastic problems at
high Reynolds numbers, modern engineering applications increasingly involve
lower Reynolds numbers, large amplitude kinematics and vortex structures that
lead to aerodynamic non-linearities.
  This paper establishes that ULLT still provides a good solution for low
Reynolds number, large-amplitude kinematics problems, by comparing ULLT results
against those of experimentally validated computational fluid dynamics
simulations at Re=10000. Three-dimensional (3D) effects stabilize Leading Edge
Vortex (LEV) structures, resulting in a good prediction of whole wing force
coefficients by ULLT. Whilst the inviscid spanwise force distributions are
accurate for small-amplitude kinematics, the ULLT cannot model 3D vortical
structures, and thus it cannot correctly predict the force distribution due the
LEV. It can however predict the shedding of LEVs to a limited extent via the
leading edge suction parameter criterion. This can then be used as an indicator
of the usefulness of the force distribution results.
