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Main Title: A Finite-Time Thermodynamics of Unsteady Fluid Flows
Author(s): Noack, Bernd R.
Schlegel, Michael
Ahlborn, Boye
Mutschke, Gerd
Morzyński, Marek
Comte, Pierre
Tadmor, Gilead
Type: Article
Language Code: en
Abstract: Turbulent fluid has often been conceptualized as a transient thermodynamic phase. Here, a finite-time thermodynamics (FTT) formalism is proposed to compute mean flow and fluctuation levels of unsteady incompressible flows. The proposed formalism builds upon the Galerkin model framework, which simplifies a continuum 3D fluid motion into a finite-dimensional phase-space dynamics and, subsequently, into a thermodynamics energy problem. The Galerkin model consists of a velocity field expansion in terms of flow configuration dependent modes and of a dynamical system describing the temporal evolution of the mode coefficients. Each mode is treated as one thermodynamic degree of freedom, characterized by an energy level. The dynamical system approaches local thermal equilibrium (LTE) where each mode has the same energy if it is governed only by internal (triadic) mode interactions. However, in the generic case of unsteady flows, the full system approaches only partial LTE with unequal energy levels due to strongly mode-dependent external interactions. The FTT model is first illustrated by a traveling wave governed by a 1D Burgers equation. It is then applied to two flow benchmarks: the relatively simple laminar vortex shedding, which is dominated by two eigenmodes, and the homogeneous shear turbulence, which has been modeled with 1459 modes.
Issue Date: 2008
Date Available: 1-Oct-2018
DDC Class: 530 Physik
Subject(s): finite-time thermodynamics
Galerkin model framework
flow benchmark
Journal Title: Journal of non-equilibrium thermodynamics
Publisher: De Gruyter
Publisher Place: Berlin
Volume: 33
Issue: 2
Publisher DOI: 10.1515/JNETDY.2008.006
Page Start: 103
Page End: 148
EISSN: 1437-4358
ISSN: 0340-0204
Notes: Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.
Appears in Collections:Inst. Strömungsmechanik und Technische Akustik (ISTA) » Publications

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