An alternative view of generalized Lagrangian mean theory

TitleAn alternative view of generalized Lagrangian mean theory
Publication TypeJournal Article
Year of Publication2013
AuthorsSalmon R
JournalJournal of Fluid Mechanics
Date Published2013/03
Type of ArticleArticle
ISBN Number0022-1120
Accession NumberWOS:000315082000008
Keywordsflow interaction; fluid; mathematical foundations; variational methods; wave-action; waves in rotating fluids

If the variables describing wave-mean flow interactions are chosen to include a set of fluid-particle labels corresponding to the mean flow, then the generalized Lagrangian mean (GLM) theory takes the form of an ordinary classical field theory. Its only truly distinctive features then arise from the distinctive feature of fluid dynamics as a field theory, namely, the particle-relabelling symmetry property, which corresponds by Noether's theorem to the many vorticity conservation laws of fluid mechanics. The key feature of the formulation is that all the dependent variables depend on a common set of space-time coordinates. This feature permits an easy and transparent derivation of the GLM equations by use of the energy-momentum tensor formalism. The particle-relabelling symmetry property leads to the GLM potential vorticity law in which pseudo-momentum is the only wave activity term present. Thus the particle-relabelling symmetry explains the prominent importance of pseudo-momentum in GLM theory.

Short TitleJ. Fluid Mech.
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