โ Scribed by Claude Cambon
No coin nor oath required. For personal study only.
Linear and nonlinear structuring effects caused by Coriolis force and/or buoyancy force/density stable stratification are surveyed and discussed in this article. Its main part, which reports on theoretical, experimental and numerical results, illustrates what can be explained from classic approaches to anisotropic homogeneous turbulence, taking advantage of the close relationship between 'two-point closures theories' and 'weakly nonlinear theories for wave turbulence'. The description including anisotropy allows the representation of linear and nonlinear interactions in terms of detailed eigenmodes of motion, like 'vortex' and 'waves', including the angular dependence of related scalar spectra and co-spectra in Fourier space. This anisotropic description is shown to be relevant to obtain precise indicators of the 'columnar' and 'pancake' structuring in physical space, by calculating for instance integral length scales for both different velocity components and different directions of two-point separations, vertical and horizontal. Additional effects of local forcing and confinement are investigated to understand the creation of coherent quasi-two dimensional vortices by pure rotation, from initially strongly three-dimensional, unstructured turbulence. Finally, stability analysis is briefly considered when the rotating and/or stratified flow consists of 'pre-existing' coherent large-scale vortices subject to three-dimensional disturbances.
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