Numerical investigation of unsteady aerodynamic characteristics of pitching delta wings

A numerical investigation of the structure of the vortical flow field over a delta wing when undergoing a pitch-up motion from 0°C to 90°C is presented here. Three-dimensional Navier-Strokes numerical simulations were carried out to predict the complex leeward-side flow field characteristics that are dominated by the effect of the breakdown of the leading-edge vortices. Two cases are considered to investigate the frequency effect on the flow field structure and aerodynamic loads for the delta wing. The lateral moments are more evident as the frequency decreases. Pitching motion with high frequency delays the vortex breakdown. Besides, the influences of a transient lateral disturbance on the lateral aerodynamics are researched. For lower frequency case, the lateral moment diverges even if the disturbance occurs at an angle of attack at which the vortex do not breakdown over the wing. As the frequency increases, the lateral moment has no evident change after the transient lateral disturbance occurs, and the lateral-directional stability is more pronounced.