title: Variational principle for frozen-in vorticity interacting with sound waves.
abstract: General properties of conservative hydrodynamic-type models are treated from positions of the canonical formalism adopted for liquid continuous media. A variational formulation is found for motion and interaction of frozen-in localized vortex structures and acoustic waves in a special description where dynamical variables are, besides the Eulerian fields of the fluid density and the potential component of the canonical momentum, also the shapes of frozen-in lines of the generalized vorticity. This variational principle can serve as a basis for approximate dynamical models with reduced number of degrees of freedom.
authors.affiliation: L. D. Landau Institute for Theoretical Physics, 2 Kosygin Street, 119334 Moscow, Russia.
authors.forename: V P
authors.initials: VP
authors.lastname: Ruban