Linear stability analysis of a counter rotating vortex pair of unequal strength

An elliptic type instability of a counter rotating vortex pair of unequal strength was numerically investigated with a linear stability analysis method. The peak growth rates of the unstable modes were predicted. The instability characteristics were found to differ from an equal strength vortex pair, of either co-rotating or counter rotating vortices. This investigation serves as a fundamental model to the flow of two unequal strength vortices, which can be generated from the ends of aerodynamic surfaces of an aircraft, such as wing tips and ailerons. These results provide predictions of the vortex arrangements likely to develop three dimensional instabilities, which is known to promote the dissipation of the underlying vortex structure.