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We prove regularity, global existence, and convergence of Lagrangian mean curvature flows in the two-convex case. Such results were previously only known in the convex case, of which the current work represents a significant improvement.…

Differential Geometry · Mathematics 2023-12-22 Chung-Jun Tsai , Mao-Pei Tsui , Mu-Tao Wang

In this chapter, we illustrate the advantage of variational principles for modeling water waves from an elementary practical viewpoint. The method is based on a `relaxed' variational principle, i.e., on a Lagrangian involving as many…

Fluid Dynamics · Physics 2019-12-16 Didier Clamond , Denys Dutykh

We present a variational approach which shows that the wave functions belonging to quantum systems in different potential landscapes, are pairwise linked to each other through a generalized continuity equation. This equation contains a…

Mathematical Physics · Physics 2019-05-22 Fotis K. Diakonos , Peter Schmelcher

The irreducible representations of the extended Galilean group are used to derive infinite sets of symmetric and asymmetric second-order differential equations with constant coeffcients. All derived equations are local and their Lagrangians…

General Physics · Physics 2023-04-14 Z. E. Musielak

In the presence of inertia-gravity waves, the geostrophic and hydrostatic balance that characterises the slow dynamics of rapidly rotating, strongly stratified flows holds in a time-averaged sense and applies to the Lagrangian-mean velocity…

Atmospheric and Oceanic Physics · Physics 2021-01-27 Hossein A. Kafiabad , Jacques Vanneste , William R. Young

The evaluation and consideration of the mean flow in wave evolution equations are necessary for the accurate prediction of fluid particle trajectories under wave groups, with relevant implications in several domains, from the transport of…

The Lagrangian formulation for the irrotational wave motion is straightforward and follows from a Lagrangian functional which is the difference between the kinetic and the potential energy of the system. In the case of fluid with constant…

Fluid Dynamics · Physics 2024-06-04 Conor T. Curtin , Rossen I. Ivanov

The majority of coastal flows are characterized by turbulence, rendering the application of shallow water equations an inadequate approach for their accurate description. This paper presents a theory for characterizing accelerated coastal…

Fluid Dynamics · Physics 2024-09-19 Arno Roland Ndengna Ngatcha

Foundations of a new projection-based model reduction approach for convection dominated nonlinear fluid flows are summarized. In this method the evolution of the flow is approximated in the Lagrangian frame of reference. Global basis…

Fluid Dynamics · Physics 2021-10-05 Rambod Mojgani , Maciej Balajewicz

We derive the exact gravitational wave solutions in a general class of quadratic Poincar\'e gauge gravity models. The Lagrangian includes all possible linear and quadratic invariants constructed from the torsion and the curvature, including…

General Relativity and Quantum Cosmology · Physics 2017-04-18 Yuri N. Obukhov

This article studies the mean curvature flow of Lagrangian submanifolds. In particular, we prove the following global existence and convergence theorem: if the potential function of a Lagrangian graph in T^{2n} is convex, then the flow…

Differential Geometry · Mathematics 2016-09-07 Knut Smoczyk , Mu-Tao Wang

In [SW2], we defined a generalized mean curvature vector field on any almost Lagrangian submanifold with respect to a torsion connection on an almost K\"ahler manifold. The short time existence of the corresponding parabolic flow was…

Differential Geometry · Mathematics 2016-04-12 Knut Smoczyk , Mao-Pei Tsui , Mu-Tao Wang

We describe a novel approach for computing wave correlation functions inside finite spatial domains driven by complex and statistical sources. By exploiting semiclassical approximations, we provide explicit algorithms to calculate the local…

Chaotic Dynamics · Physics 2017-03-09 Stephen C Creagh , Gabriele Gradoni , Timo Hartmann , Gregor Tanner

We formulate a perturbative approximation to gravitational instability, based on Lagrangian hydrodynamics in Newtonian cosmology. We take account of `pressure' effect of fluid, which is kinematically caused by velocity dispersion, to aim…

Astrophysics · Physics 2009-11-07 Masaaki Morita , Takayuki Tatekawa

We derive the exact gravitational wave solutions in a general class of quadratic metric-affine gauge gravity models. The Lagrangian includes all possible linear and quadratic invariants constructed from the torsion, nonmetricity and the…

General Relativity and Quantum Cosmology · Physics 2021-01-14 Alejandro Jiménez-Cano , Yuri N. Obukhov

It is well-known that the equations for a simple fluid can be cast into what is called their Lagrange formulation. We introduce a notion of a generalized Lagrange formulation, which is applicable to a wide variety of systems of partial…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Robert Geroch , Gabriel Nagy , Oscar Reula

A Lagrangian gravity-wave parameterization (MS-GWaM, Multi-Scale Gravity-Wave Model) that allows for fully transient wave-mean-flow interaction and horizontal propagation is applied to orographic gravity waves for the first time. Both…

Fluid Dynamics · Physics 2024-08-07 Felix Jochum , Ray Chew , François Lott , Georg S. Voelker , Jan Weinkaemmerer , Ulrich Achatz

We derive a Wentzel-Kramers-Brillouin (WKB) closure of the generalised Lagrangian mean (GLM) theory by using a phase-averaged Hamilton variational principle for the Euler--Boussinesq (EB) equations. Following Gjaja and Holm 1996, we…

Fluid Dynamics · Physics 2023-05-17 Darryl D. Holm , Ruiao Hu , Oliver D. Street

We consider two-fluid flow problems in an Arbitrary Lagrangian Eulerian (ALE) framework. The purpose of this work is twofold. First, we address the problem of the moving contact line, namely the line common to the two fluids and the wall.…

Numerical Analysis · Mathematics 2015-05-13 J. -F. Gerbeau , T. Lelievre

Exact Lagrangian in compact form is derived for planar internal waves in a two-fluid system with a relatively small density jump (the Boussinesq limit taking place in real oceanic conditions), in the presence of a background shear current…

Atmospheric and Oceanic Physics · Physics 2010-09-24 V. P. Ruban