Contrasting turbulence in stably stratified flows and thermal convection

Abstract

The properties of stably stratified turbulence and turbulent thermal convection are contrasted in this paper. A key difference between theses flows is the sign of the kinetic energy feed by buoyancy, ${{ \mathcal F }}_{B}$. For SST, ${{ \mathcal F }}_{B}\lt 0$ due to its stable nature; consequently, the kinetic energy flux Πu(k) decreases with wavenumber k that leads to a steep kinetic energy spectrum, Eu(k) ~ k−11/5. Turbulent convection is unstable, hence ${{ \mathcal F }}_{B}\gt 0$ that leads to an increase of Πu(k) with k; this increase however, is marginal due to relatively weak buoyancy, hence Eu(k) ~ k−5/3, similar to that in hydrodynamic turbulence. This paper also describes the conserved fluxes for the above systems.