Three-dimensional, short-wavelength instabilities in idealized models of aircraft wake vortices

Aircraft wakes are known to comprise of counter-rotating vortex pairs, and their instability characteristics have significant implications on aircraft performance and safety. Three-dimensional short-wavelength instabilities on idealized aircraft wake vortex pair are investigated using a local stability analysis. Two strategies are used to generate the base flow; the first involves approximating the base flow as a combination of two counter rotating Lamb-Oseen vortices and in the second strategy, the base flow is generated by performing a 2D numerical simulation. The vortex pair is found to be susceptible to elliptic and tripolar instabilities, and the corresponding growth rates are calculated for a wide range of vortex core size to vortex separation distance ratios. The local stability results are compared against relevant previous studies based on both local and global stability analyses. Finally, to represent aircraft wake vortices more faithfully, an axial flow is added to the aforementioned 2D base flow, and the effects of the axial flow are systematically investigated.