Exploration of Mechanisms leading to turbulent bifurcations

Turbulence is usually presented as a universal, ultimate state of a flow. This is especially relevant at geophysical level where the scales are so large that the system is guaranteed to be far in a turbulent state. Experiments and observations of the climate in the near and far past show that dramatic bifurcations of endogenous origins are still possible even in this supposed featureless flow. In this thesis, I will explore the possibility that these abrupt changes and especially how the small-scale structures of the flow relate to the large-scale ones. Using traditional numerical techniques, this would be hard to test conclusively, due to the prohibitively heavy cost of the finely resolved simulations. This is why I will be relying on a new toy model for fluid mechanics known as Logarithmic Lattices. The latter are upgraded with new approaches to implement boundary conditions with more flexibility. This tool will help investigate the feedback loop where on the one hand the small scales are being generated from the large scales following a downscale cascade, while conversely the small scales can trigger large scale bifurcations.