On the different types of global and local conservation laws for partial differential equations in three spatial dimensions: Review and recent developments. (November 2020)

• Record Type: Journal Article
• Authors: Anco, Stephen C.; Cheviakov, Alexei F.
• Is Part Of: International journal of non-linear mechanics. Volume 126(2020)
• Publication Date: 2020-11
• Subjects: Nonlinear mechanics -- Periodicals; Mécanique non linéaire -- Périodiques; Nonlinear mechanics; Periodicals; 531
• DOI: 10.1016/j.ijnonlinmec.2020.103569
• Languages: English
• ISSNs: 0020-7462

Abstract

Abstract: For systems of partial differential equations in three spatial dimensions, dynamical conservation laws holding on volumes, surfaces, and curves, as well as topological conservation laws holding on surfaces and curves, are studied in a unified framework. Both global and local formulations of these different conservation laws are discussed, including the forms of global constants of motion. The main results consist of providing an explicit characterization for when two conservation laws are locally or globally equivalent, and for when a conservation law is locally or globally trivial, as well as deriving relationships among the different types of conservation laws. In particular, the notion of a "trivial" conservation law is clarified for all of the types of conservation laws. Moreover, as further new results, conditions under which a trivial local conservation law on a domain can yield a non-trivial global conservation law on the domain boundary are determined and shown to be related to differential identities that hold for PDE systems containing both evolution equations and spatial constraint equations. Numerous physical examples from fluid flow, gas dynamics, electromagnetism, and magnetohydrodynamics are used as illustrations. Highlights: All types of conservation laws (CLs) in 3 dimensions are reviewed in a unified framework. A locally trivial CL on a domain can yield a globally non-trivial CL on the boundary. A direct connection is shown between boundary CLs and differential identities in a PDE. Two new examples of boundary CLs are given for fluid flow with non-vanishing vorticity.