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Irreversibility of the two-dimensional enstrophy cascade.
E Piretto1, S Musacchio2, F De Lillo1
1Department of Physics and INFN, Università di Torino, 1 Via P. Giuria, 10125 Torino, Italy.
Physical Review. E
|December 15, 2016
Summary
We investigated time irreversibility in two-dimensional turbulence using metenstrophy. Higher Reynolds numbers increased irreversibility, similar to 3D turbulence, but forcing statistics played a key role.
Area of Science:
- Fluid Dynamics
- Turbulence Theory
- Computational Physics
Background:
- Two-dimensional turbulence exhibits distinct energy and enstrophy cascades.
- Time irreversibility is a key characteristic of turbulent flows.
- Metenstrophy, the time derivative of squared vorticity, quantifies enstrophy dynamics.
Purpose of the Study:
- To quantify the time irreversibility of the direct enstrophy cascade in 2D turbulence.
- To investigate the dependence of irreversibility on the Reynolds number.
- To compare irreversibility in 2D turbulence with 3D turbulence and the energy cascade.
Main Methods:
- Extensive direct numerical simulations (DNS) of 2D turbulence.
- Lagrangian trajectory analysis of metenstrophy.
- Statistical analysis of the probability density function (PDF) of metenstrophy.
Main Results:
- Time irreversibility was measured via the asymmetry of the metenstrophy PDF.
- Irreversibility increases with the Reynolds number in 2D turbulence.
- Significant differences were found compared to the energy cascade, particularly the influence of forcing statistics.
Conclusions:
- The direct enstrophy cascade in 2D turbulence is time-irreversible.
- Reynolds number and forcing statistics are crucial determinants of this irreversibility.
- Findings offer insights into fundamental differences between 2D and 3D turbulence dynamics.
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