In many turbulent flows, scales larger than the forcing scale display equipartition of energy. This familiar result of equilibrium statistical physics could look surprising in turbulent flows which are considered as a canonical example of an out of equilibrium dissipative system.
After displaying several examples and discussing this result, we show that concepts from equilibrium statistical physics can also be used to describe transitions between different turbulent regimes when a governing parameter is varied. More precisely, the truncated Euler equation provides a tool to describe the dynamics of large scales and bifurcations that occur on a turbulent background.
Finally, we show how the dynamics of these large scale is related to 1/f type noise observed in many turbulent flows and elsewhere.