Fluctuation-response relation in turbulent systems.
We address the problem of measuring time properties of response functions (Green functions) in Gaussian models (Orszag-McLaughin) and strongly non-Gaussian models (shell models for turbulence). We introduce the concept of halving-time statistics to have a statistically stable tool to quantify the time decay of response functions and generalized response functions of high order. We show numerically that in shell models for three-dimensional turbulence response functions are inertial range quantities. This is a strong indication that the invariant measure describing the shell-velocity fluctuations is characterized by short range interactions between neighboring shells.
Biferale
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Department of Physics and INFM, University of Rome "Tor Vergata," Via della Ricerca Scientifica 1, I-00133 Roma, Italy.
Daumont
I
I
Lacorata
G
G
Vulpiani
A
A