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Nonequilibrium ensembles for the three-dimensional Navier-Stokes equations.

Margazoglou, G., Biferale, L., Cencini, M., Gallavotti, G. and Lucarini, V. ORCID: (2022) Nonequilibrium ensembles for the three-dimensional Navier-Stokes equations. Physical Review E, 105 (6). 065110. ISSN 2470-0053

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To link to this item DOI: 10.1103/PhysRevE.105.065110


At the molecular level fluid motions are, by first principles, described by time reversible laws. On the other hand, the coarse grained macroscopic evolution is suitably described by the Navier-Stokes equations, which are inherently irreversible, due to the dissipation term. Here, a reversible version of three-dimensional Navier-Stokes is studied, by introducing a fluctuating viscosity constructed in such a way that enstrophy is conserved, along the lines of the paradigm of microcanonical versus canonical treatment in equilibrium statistical mechanics. Through systematic simulations we attack two important questions: (a) What are the conditions that must be satisfied in order to have a statistical equivalence between the two nonequilibrium ensembles? (b) What is the empirical distribution of the fluctuating viscosity observed by changing the Reynolds number and the number of modes used in the discretization of the evolution equation? The latter point is important also to establish regularity conditions for the reversible equations. We find that the probability to observe negative values of the fluctuating viscosity becomes very quickly extremely small when increasing the effective Reynolds number of the flow in the fully resolved hydrodynamical regime, at difference from what was observed previously.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Mathematics and Statistics
ID Code:106594
Additional Information:** From PubMed via Jisc Publications Router ** Journal IDs: eissn 2470-0053 ** Article IDs: pubmed: 35854520 ** History: accepted 22-05-2022; submitted 27-12-2021
Publisher:American Physical Society


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