Emergence of helicity in rotating stratified turbulence
annick pouquet2013, Physical Review E
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Abstract
We perform numerical simulations of decaying rotating stratified turbulence and show, in the Boussinesq framework, that helicity (velocity-vorticity correlation), as observed in super-cell storms and hurricanes, is spontaneously created due to an interplay between buoyancy and rotation common to large-scale atmospheric and oceanic flows. Helicity emerges from the joint action of eddies and of inertia-gravity waves (with inertia and gravity with respective associated frequencies f and N ), and it occurs when the waves are sufficiently strong. For N/f < 3 the amount of helicity produced is correctly predicted by a quasi-linear balance equation. Outside this regime, and up to the highest Reynolds number obtained in this study, namely Re ≈ 10000, helicity production is found to be persistent for N/f as large as ≈ 17, and for ReF r 2 and ReRo 2 respectively as large as ≈ 100 and ≈ 24000.
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