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On the Computation of Roll Waves

Shi Jin, Yong Jung Kim (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

The phenomenon of roll waves occurs in a uniform open-channel flow down an incline, when the Froude number is above two. The goal of this paper is to analyze the behavior of numerical approximations to a model roll wave equation ut + uux = u,u(x,0) = u0(x), which arises as a weakly nonlinear approximation of the shallow water equations. The main difficulty associated with the numerical approximation of this problem is its linear instability. Numerical round-off error can easily overtake the...

On the condition of Λ-convexity in some problems of weak continuity and weak lower semicontinuity

Agnieszka Kałamajska (2001)

Colloquium Mathematicae

We study the functional I f ( u ) = ∫ Ω f ( u ( x ) ) d x , where u=(u₁, ..., uₘ) and each u j is constant along some subspace W j of ℝⁿ. We show that if intersections of the W j ’s satisfy a certain condition then I f is weakly lower semicontinuous if and only if f is Λ-convex (see Definition 1.1 and Theorem 1.1). We also give a necessary and sufficient condition on W j j = 1 , . . . , m to have the equivalence: I f is weakly continuous if and only if f is Λ-affine.

On the conditional regularity of the Navier-Stokes and related equations

Dongho Chae (2006)

Banach Center Publications

We present regularity conditions for a solution to the 3D Navier-Stokes equations, the 3D Euler equations and the 2D quasigeostrophic equations, considering the vorticity directions together with the vorticity magnitude. It is found that the regularity of the vorticity direction fields is most naturally measured in terms of norms of the Triebel-Lizorkin type.

On the connection between some Riemann-solver free approaches to the approximation of multi-dimensional systems of hyperbolic conservation laws

Tim Kröger, Sebastian Noelle, Susanne Zimmermann (2004)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

In this paper, we present some interesting connections between a number of Riemann-solver free approaches to the numerical solution of multi-dimensional systems of conservation laws. As a main part, we present a new and elementary derivation of Fey’s Method of Transport (MoT) (respectively the second author’s ICE version of the scheme) and the state decompositions which form the basis of it. The only tools that we use are quadrature rules applied to the moment integral used in the gas kinetic derivation...

On the connection between some Riemann-solver free approaches to the approximation of multi-dimensional systems of hyperbolic conservation laws

Tim Kröger, Sebastian Noelle, Susanne Zimmermann (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

In this paper, we present some interesting connections between a number of Riemann-solver free approaches to the numerical solution of multi-dimensional systems of conservation laws. As a main part, we present a new and elementary derivation of Fey's Method of Transport (MoT) (respectively the second author's ICE version of the scheme) and the state decompositions which form the basis of it. The only tools that we use are quadrature rules applied to the moment integral used in the...

On the continuity of degenerate n-harmonic functions

Flavia Giannetti, Antonia Passarelli di Napoli (2012)

ESAIM: Control, Optimisation and Calculus of Variations

We study the regularity of finite energy solutions to degenerate n-harmonic equations. The function K(x), which measures the degeneracy, is assumed to be subexponentially integrable, i.e. it verifies the condition exp(P(K)) ∈ Lloc1. The function P(t) is increasing on  [0,∞[  and satisfies the divergence condition ∫ 1 ∞ P ( t ) t 2 d t = ∞ . ∫ 1 ∞ P ( t ) t 2   d t = ∞ .

On the continuity of degenerate n-harmonic functions

Flavia Giannetti, Antonia Passarelli di Napoli (2012)

ESAIM: Control, Optimisation and Calculus of Variations

We study the regularity of finite energy solutions to degenerate n-harmonic equations. The function K(x), which measures the degeneracy, is assumed to be subexponentially integrable, i.e. it verifies the condition exp(P(K)) ∈ Lloc1. The function P(t) is increasing on  [0,∞[  and satisfies the divergence condition ∫ 1 ∞ P ( t ) t 2   d t = ∞ .

On the controllability and stabilization of the linearized Benjamin-Ono equation

Felipe Linares, Jaime H. Ortega (2005)

ESAIM: Control, Optimisation and Calculus of Variations

In this work we are interested in the study of controllability and stabilization of the linearized Benjamin-Ono equation with periodic boundary conditions, which is a generic model for the study of weakly nonlinear waves with nonlocal dispersion. It is well known that the Benjamin-Ono equation has infinite number of conserved quantities, thus we consider only controls acting in the equation such that the volume of the solution is conserved. We study also the stabilization with a feedback law which...

On the controllability and stabilization of the linearized Benjamin-Ono equation

Felipe Linares, Jaime H. Ortega (2010)

ESAIM: Control, Optimisation and Calculus of Variations

In this work we are interested in the study of controllability and stabilization of the linearized Benjamin-Ono equation with periodic boundary conditions, which is a generic model for the study of weakly nonlinear waves with nonlocal dispersion. It is well known that the Benjamin-Ono equation has infinite number of conserved quantities, thus we consider only controls acting in the equation such that the volume of the solution is conserved. We study also the stabilization with a feedback law...

On the controllability of fractional dynamical systems

Krishnan Balachandran, Jayakumar Kokila (2012)

International Journal of Applied Mathematics and Computer Science

This paper is concerned with the controllability of linear and nonlinear fractional dynamical systems in finite dimensional spaces. Sufficient conditions for controllability are obtained using Schauder's fixed point theorem and the controllability Grammian matrix which is defined by the Mittag-Leffler matrix function. Examples are given to illustrate the effectiveness of the theory.

On the controllability of the 1-D isentropic Euler equation

Olivier Glass (2007)

Journal of the European Mathematical Society

We study the controllability problem for the one-dimensional Euler isentropic system, both in Eulerian and Lagrangian coordinates, by means of boundary controls, in the context of weak entropy solutions. We give a sufficient condition on the initial and final states under which the first one can be steered to the latter.

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