BiGlobal and Point Vortex Methods for the Instability Analysis of Wakes

Abstract

To better understand destruction mechanisms of wake-vortices behind aircraft, the point vortex method for stability (inviscid) used by Crow 1970 is here compared with viscous modal global stability analysis of the linearized Navier-Stokes equations acting on a two-dimensional basic flow, i.e. BiGlobal stability analysis. The fact that the BiGlobal method is viscous, and uses a finite area vortex model, gives rise to results somewhat different from the point vortex model. It adds more parameters to the problem, but is more realistic.