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Evolution by the vortex filament equation of curves with a corner

Valeria Banica (2013)

Journées Équations aux dérivées partielles

In this proceedings article we shall survey a series of results on the stability of self-similar solutions of the vortex filament equation. This equation is a geometric flow for curves in 3 and it is used as a model for the evolution of a vortex filament in fluid mechanics. The main theorem give, under suitable assumptions, the existence and description of solutions generated by curves with a corner, for positive and negative times. Its companion theorem describes the evolution of perturbations...

Évolution de tourbillon à support compact

Dragoş Iftimie (1999)

Journées équations aux dérivées partielles

On considère l’équation d’Euler incompressible dans le plan. Dans le cas où le tourbillon est positif et à support compact on montre que le support du tourbillon croît au plus comme O [ ( t log t ) ] 1 / 4 , améliorant la borne O ( t 1 / 3 ) obtenue par C. Marchioro. Dans le cas où le tourbillon change de signe, on donne un exemple de tourbillon initial tel que la croissance du diamètre du support du tourbillon est exactement O ( t ) . Enfin, dans le cas du demi-plan et du tourbillon initial positif et à support compact, on montre que le...

Évolution d'une singularité de type cusp dans une poche de tourbillon.

Raphaël Danchin (2000)

Revista Matemática Iberoamericana

We investigate the evolution of singularities in the boundary of a vortex patch for two-dimensional incompressible Euler equations. We are particularly interested in cusp-like singularities which, according to numerical simulations, are stable. In this paper, we first prove that, unlike the case of a corner-like singularity, the cusp-like singularity generates a lipschitzian velocity. We then state a global result of persistence of conormal regularity with respect to vector fields vanishing at a...

Evolution in a migrating population model

Włodzimierz Bąk, Tadeusz Nadzieja (2012)

Applicationes Mathematicae

We consider a model of migrating population occupying a compact domain Ω in the plane. We assume the Malthusian growth of the population at each point x ∈ Ω and that the mobility of individuals depends on x ∈ Ω. The evolution of the probability density u(x,t) that a randomly chosen individual occupies x ∈ Ω at time t is described by the nonlocal linear equation u t = Ω φ ( y ) u ( y , t ) d y - φ ( x ) u ( x , t ) , where φ(x) is a given function characterizing the mobility of individuals living at x. We show that the asymptotic behaviour of u(x,t)...

Exact boundary controllability of 3-D Euler equation

Olivier Glass (2010)

ESAIM: Control, Optimisation and Calculus of Variations

We prove the exact boundary controllability of the 3-D Euler equation of incompressible inviscid fluids on a regular connected bounded open set when the control operates on an open part of the boundary that meets any of the connected components of the boundary.

Exact boundary controllability of a nonlinear KdV equation with critical lengths

Jean-Michel Coron, Emmanuelle Crépeau (2004)

Journal of the European Mathematical Society

We study the boundary controllability of a nonlinear Korteweg–de Vries equation with the Dirichlet boundary condition on an interval with a critical length for which it has been shown by Rosier that the linearized control system around the origin is not controllable. We prove that the nonlinear term gives the local controllability around the origin.

Currently displaying 81 – 100 of 212