[SLS] Pascale Garaud (UC Santa Cruz)

“Asymptotic analysis and numerical simulations of stratified turbulence (at Pr ≤ 1)”

I will present some recent results on the properties of stratified turbulence at Pr ≤ 1, obtained using a combination of asymptotic analysis and numerical simulations. The asymptotic analysis leverages the strong anisotropy of the flow combined with its multiscale properties, and yields scaling laws for the characteristic vertical length scale and vertical velocity of the turbulent eddies, as functions of the Froude number Fr (characterizing the stratification), Reynolds number Re (characterizing viscous effects), and Peclet number Pe (characterizing the buoyancy diffusivity). Numerical simulations verify these scaling laws, but also show that the turbulence is strongly intermittent in the limit of strong stratification. Interestingly, we find that the fraction of the volume occupied by ‘turbulent patches’ is a universal function of the so-called buoyancy Reynolds number (Re_b = Fr² Re), and similarly the fraction of the volume occupied by local overturns is a universal function of the so-called buoyancy Peclet number (Pe_b = Fr² Pe). These findings allow us to obtain useful parametrizations for turbulent mixing in various low Prandtl number environments.

Sack Lunch Seminar Series —
Informal seminar series within PAOC (Program in Atmospheres, Oceans, and Climate) that focuses on more specialized topics than the PAOC Colloquium. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.

Contact: sacklunch-committee@mit.edu