Multi-scale dynamics of Kelvin–Helmholtz instabilities. Part 2. Energy dissipation rates, evolutions and statistics

Fritts et al. (J. Fluid Mech., vol. xx, 2022, xx) describe a direct numerical simulation of interacting Kelvin–Helmholtz instability (KHI) billows arising due to initial billow cores that exhibit variable phases along their axes. Such KHI strong ‘tube and knot’ dynamics identified in early laboratory studies by Thorpe ( Geophys. Astrophys. Dyn. , 34, 1985, pp. 175–199). Q.J.R. Meteorol. Soc. 128, 2002, 1529–1542) noted these may be prevalent the atmosphere, they were recently atmospheric observations at high altitudes. Tube knot found J. Fluid. Mech. 2022) drive stronger faster turbulence transitions than secondary instabilities individual KH billows. Results presented here reveal tube also yield energy dissipation rates $\sim$ 2–4 times larger as arises remain 2–3 later stages flow evolution, compared with those convective (CI) accompanying without influences. Elevated occur on much scales CI where are misaligned. excite large-scale Kelvin ‘twist waves’ cause vortex core fragmentation, more energetic cascades similar interactions smaller account for strongest events such evolutions.