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Article Dans Une Revue Journal of Fluid Mechanics Année : 2021

Energy balance and mixing between waves and eddies in stably stratified turbulence

Résumé

DNS simulations of stably stratified turbulence explore the strong stratification regime and the transition between the viscosity-affected stratified and the strongly stratified regimes. The 3D field is decomposed into Internal Gravity Waves (IGW) and eddy motion by using an extended Riley decomposition (Riley et al. 1981) that takes into account the space-time properties of waves, their modification by vertically sheared horizontal flow and the vertical mixing by eddies (Lam et al. 2020). We establish the evolution equations for the IGW and eddy parts separately. Up to buoyancy Reynolds number Re b ∼ 1, we observe that eddy dissipation is larger than IGW dissipation and is reinforced by an additional exchange that pumps energy from IGW to eddy. For higher Re b , the two dynamics seems to be separate and no global exchange is observed. The origin of the mixing coefficient in terms of IGW and eddy is computed. At the largest Re b considered, the mixing due to eddies is four times the mixing due to waves.
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Dates et versions

hal-03397106 , version 1 (22-10-2021)
hal-03397106 , version 2 (15-11-2021)

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H. Lam, A. Delache, F S Godeferd. Energy balance and mixing between waves and eddies in stably stratified turbulence. Journal of Fluid Mechanics, 2021, 923, ⟨10.1017/jfm.2021.589⟩. ⟨hal-03397106v2⟩
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