54 research outputs found
Higher-Order Global Regularity of an Inviscid Voigt-Regularization of the Three-Dimensional Inviscid Resistive Magnetohydrodynamic Equations
We prove existence, uniqueness, and higher-order global regularity of strong
solutions to a particular Voigt-regularization of the three-dimensional
inviscid resistive Magnetohydrodynamic (MHD) equations. Specifically, the
coupling of a resistive magnetic field to the Euler-Voigt model is introduced
to form an inviscid regularization of the inviscid resistive MHD system. The
results hold in both the whole space \nR^3 and in the context of periodic
boundary conditions. Weak solutions for this regularized model are also
considered, and proven to exist globally in time, but the question of
uniqueness for weak solutions is still open. Since the main purpose of this
line of research is to introduce a reliable and stable inviscid numerical
regularization of the underlying model we, in particular, show that the
solutions of the Voigt regularized system converge, as the regularization
parameter \alpha\maps0, to strong solutions of the original inviscid
resistive MHD, on the corresponding time interval of existence of the latter.
Moreover, we also establish a new criterion for blow-up of solutions to the
original MHD system inspired by this Voigt regularization. This type of
regularization, and the corresponding results, are valid for, and can also be
applied to, a wide class of hydrodynamic models
Global Regularity vs. Finite-Time Singularities: Some Paradigms on the Effect of Boundary Conditions and Certain Perturbations
In light of the question of finite-time blow-up vs. global well-posedness of
solutions to problems involving nonlinear partial differential equations, we
provide several cautionary examples which indicate that modifications to the
boundary conditions or to the nonlinearity of the equations can effect whether
the equations develop finite-time singularities. In particular, we aim to
underscore the idea that in analytical and computational investigations of the
blow-up of three-dimensional Euler and Navier-Stokes equations, the boundary
conditions may need to be taken into greater account. We also examine a
perturbation of the nonlinearity by dropping the advection term in the
evolution of the derivative of the solutions to the viscous Burgers equation,
which leads to the development of singularities not present in the original
equation, and indicates that there is a regularizing mechanism in part of the
nonlinearity. This simple analytical example corroborates recent computational
observations in the singularity formation of fluid equations
A Blow-Up Criterion for the 3D Euler Equations Via the Euler-Voigt Inviscid Regularization
We propose a new blow-up criterion for the 3D Euler equations of
incompressible fluid flows, based on the 3D Euler-Voigt inviscid
regularization. This criterion is similar in character to a criterion proposed
in a previous work by the authors, but it is stronger, and better adapted for
computational tests. The 3D Euler-Voigt equations enjoy global well-posedness,
and moreover are more tractable to simulate than the 3D Euler equations. A
major advantage of these new criteria is that one only needs to simulate the 3D
Euler-Voigt, and not the 3D Euler equations, to test the blow-up criteria, for
the 3D Euler equations, computationally
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