Long-wave deformation of in-ground-effect wake vortex under crosswind condition

Abstract

The in-ground-effect (IGE) aircraft wake vortex poses great hazards to airplanes. Especially when the vortex column is deformed with a long wavelength, the vortex core position is harder to determine, and thus, the IGE wake vortex is essential to air traffic safety and requires more detailed research. In this study, to account for the effects of roll-up-induced structures, the wake vortex pair was initialized using the vortex sheet model proposed by Lin et al. [1]. The asymmetrical wing loading effect on IGE wake evolution was considered for the first time. The Large Eddy Simulation results showed that the crosswind strengthened the upwind vortex, while the long-term wake vortex evolution was not significantly influenced by the wind. Most importantly, in certain crosswind conditions, the wake vortex deformed sinusoidally and linked with its mirror counterpart. From a linear stability analysis, it was found that this long-wave deformation could only occur on the upwind side owing to the redistribution of the strain field caused by the near-ground wind shear. Due to secondary vortex generation, the deformation was suppressed and a low growth rate of α≈0.41 was recorded for the long-wave instability.