Pitch rate and pitch-axis location effects on vortex breakdown onset

Computational results are presented for the onset of vortex breakdown above a 75-deg sweep delta wing subject to a ramp-type pitch maneuver to high angle of attack. The flows are simulated by solving the full threedimensional unsteady NavierStokes equations on a moving grid using the implicit Beam-Warming algorithm. An assessment of the effects of numerical resolution, and comparison with experiment are employed to validate the computational approach. The effects of pitch rate and pitch-axis location are examined. For a range of these parameters, it is found that either increasing pitch rate or moving the axis downstream results in a larger angular delay of vortex bursting. These effects are correlated with the motion-induced effective incidence along the wing. For fixed pitch rate, the change in pivot location is equivalent to a shift in time without significant alteration of the flow structure.