Difficulties in predicting vortex breakdown effects on a rolling delta wing

An analysis has been performed of the challenges encountered when trying to predict the unsteady aerodynamics associated with the breakdown of the leading-edge vortices on a 65-deg sharp-edged delta wing, describing roll oscillations around an axis inclined 30 deg to the freestream, It is shown that to produce a realistic prediction the mathematical model has to represent in a satisfactory manner the highly nonlinear, almost discontinuous steady and unsteady aerodynamic characteristics associated with the downstream travel of the vortex breakdown past the trailing edge on the leeside wing half at 5 < \phi\ < 8 deg.