ANR DisET meeting (30-31 Jan 2019)

**"Garrett-Munk spectrum"**

vertical spectra $N^2 k_z^{-3}$

temporal spectra, energy for $f < \omega < N$

Naive representation: soup - cascade of (weakly interacting) IG waves?

- Kinematic decomposition: $\omega_z$, $\nabla_h u$ and shear modes

**For oceanic parameters** (strongly stratified, large Re):

Strongly non-linear

$\omega_z \sim \nabla_h u$

$$b(x,z)$$

Brethouwer, Billant, Chomaz & Lindborg (2007)

no well-defined $T_N(k)$

$\Rightarrow$ well-defined non-dimensional numbers

direction of propagation $F = \frac{\omega_l}{N}$

non-linearity $\gamma = \frac{\omega_f}{\omega_l}$

dissipation

Dissipation only at small scales $\Rightarrow$ energy transfers towards small scales

It would not be the case without stratification!

Small vertical length scales for strong stratification

**Warning:** dissipation at large horizontal scale even for large $Re$

$\gamma = 1$ (strongly stratified), $n_x = 3840$

**A thesis:**

- open-source never so strong,
- new tools and methods allowing collective work,
- possibility of collaborations on good quality research codes.

**Some packages:**

fluidimage, fluidlab, fluidsim, fluidfft, transonic, ...

(Ashwin Vishnu, Cyrille Bonamy, Miguel Calpe)

**Open-source collaborative**framework / library for writting solversHigh quality code (tests run with continuous integration, proper documentation, issue tracker)

Very user-friendly

Developer friendly: mostly in Python, highly modular (object-oriented Python)

Extensible (for example fluidsim-ocean)

Specialized in pseudo-spectral (Fourier), but not only

Very efficient

FluidFFT: Python / C++ library for (parallel) Fourier transforms (2D and 3D)

Transonic and Pythran: "Make your Python code fly at transonic speeds!" (actually at good-C++ speed)

Work in progress

Dissipation dominated by vertical gradient $\Rightarrow$ not yet "geophysical" regime

Very interesting tools (FluidSim, FluidFFT, Transonic)

Outputs not shown here (for example spatio-temporal spectra)

Can we obtain (weak?) internal gravity wave turbulence?

Statistics similar as in the oceans?