Vortex tubes in shear-stratified turbulent flows
Coherent vortex extraction using wavelets is applied to a shear-stratified turbulent flow computed by Direct Numerical Simulations (DNS) to compute the atmospheric jet stream at the tropopause. The basic state is characterised by a jet centred at the tropopause and stable density stratification profile with increased stratification above the tropopause. Quasi-equilibrium turbulent flow-fields are obtained after long-time integration of the governing equations written in primitive variables using adaptive spectral domain decomposition method. The coherent vortex tubes are extracted from the vorticity and potential vorticity fields, using a nonlinear filtering in wavelet space. It is finally checked that the coherent vortex tubes exhibit the same dynamics as the total flow and therefore drive the residual background flow.
KeywordsPotential Vorticity Vortex Tube Vorticity Field Coherent Vortex Gradient Richardson Number
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