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Statistical mechanics of large scales in turbulent flows
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.