Kelvin twist waves in the transition to turbulence

We present evidence for Kelvin twist waves on vortex tubes in a numerical simulation of the transition to turbulence in a breaking internal gravity wave. Specifically, m = 0, m = 1, and m = 2 twist waves are found and are compared to analytic versions of the waves. The observed twist waves are of a sufficiently large amplitude to break up the vortex tubes on which they reside, with the m = 0 waves fragmenting the vortex tubes along their length and the m = 2 waves unraveling the vortex tubes into pairs of helical tubes. Under the influence of these waves, the flow evolves from an organized collection of horseshoe vortices to a disorganized collection of vortex fragments. (C) Elsevier, Paris.