Abstract
The dynamics of a stably-stratified mixing layer exhibit the major features of small scale dynamics in stratified turbulence. In order to get some insight into those dynamics, a stably-stratified mixing layer is studied by + means of direct numerical simulations of resolution up to 1283. The three-dimensional Boussinesq equations are solved using a pseudo-spectral method.
The fundamental feature exhibited by our calculations is the organization of the flow into thin and quasi-horizontal layers of spanwise vorticity (vorticity of the mean flow and associated fluctuations). Depending upon the initial value of the Reynolds and Richardson numbers, two regimes have to be distinguished: a regime of “diffusive layers” (for low values of these parameters), and a regime of “baroclinic layers” (for higher values). In the former regime, the layer dynamics are driven by the shear and diffusive effects, which eventually balance. In the regime of baroclinic layers (upon which we shall focus in this paper), horizontal density variations and the mean shear lead to the development of a secondary instability of the Kelvin-Helmholtz + type in the layers. We show that this instability does not develop in a two-dimensional layer and propose an argument to explain this behavior.
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© 1991 Springer Science+Business Media Dordrecht
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Staquet, C. (1991). Influence of a shear on a stably-stratified flow. In: Metais, O., Lesieur, M. (eds) Turbulence and Coherent Structures. Fluid Mechanics and Its Applications, vol 2. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7904-9_28
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DOI: https://doi.org/10.1007/978-94-015-7904-9_28
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-4063-3
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