Competing Lagrangians for incompressible and compressible viscous flow

Marner, F.; Scholle, M.; Herrmann, D.; Gaskell, P.H.

Abstract

A recently proposed variational principle with a discontinuous Lagrangian for viscous flow is reinterpreted against the background of stochastic variational descriptions of dissipative systems, underpinning its physical basis from a different viewpoint. It is shown that additional non-classical contributions to the friction force occurring in the momentum balance vanish by time averaging. Accordingly, the discontinuous Lagrangian can alternatively be understood from the standpoint of an analogous deterministic model for irreversible processes of stochastic character. A comparison is made with established stochastic variational descriptions and an alternative deterministic approach based on a first integral of Navier–Stokes equations is undertaken. The applicability of the discontinuous Lagrangian approach for different Reynolds number regimes is discussed considering the Kolmogorov time scale. A generalization for compressible flow is elaborated and its use demonstrated for damped sound waves.

Citation

Marner, F., Scholle, M., Herrmann, D., & Gaskell, P. (2019). Competing Lagrangians for incompressible and compressible viscous flow. Royal Society Open Science, 6(1), Article 181595. https://doi.org/10.1098/rsos.181595

• Journal Article Type: Article
• Acceptance Date: Dec 7, 2018
• Online Publication Date: Jan 16, 2019
• Publication Date: Jan 16, 2019
• Deposit Date: Jan 16, 2019
• Publicly Available Date: Jan 16, 2019
• Journal: Royal Society Open Science
• Electronic ISSN: 2054-5703
• Publisher: The Royal Society
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Issue: 1
• Article Number: 181595
• DOI: https://doi.org/10.1098/rsos.181595
• Public URL: https://durham-repository.worktribe.com/output/1310219