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Borges de Oliveira, Hermenegildo

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  • The classical Kelvin-Voigt problem for incompressible fluids with unknown non-constant density: existence, uniqueness and regularity
    Publication . Antontsev, S. N.; Oliveira, H. B. de; Khompysh, Kh
    The classical Kelvin-Voigt equations for incompressible fluids with non-constant density are investigated in this work. To the associated initial-value problem endowed with zero Dirichlet conditions on the assumed Lipschitz-continuous boundary, we prove the existence of weak solutions: velocity and density. We also prove the existence of a unique pressure. These results are valid for d is an element of {2, 3, 4}. In particular, if d is an element of {2, 3}, the regularity of the velocity and density is improved so that their uniqueness can be shown. In particular, the dependence of the regularity of the solutions on the smoothness of the given data of the problem is established.
  • Existence and large time behavior for generalized Kelvin-Voigt equations governing nonhomogeneous and incompressible fluids
    Publication . Antontsev, S N; de Oliveira, H. B.; Khompysh, Kh
    Generalized Kelvin-Voigt equations governing nonhomogeneous and incompressible fluids are considered in this work. We assume that, in the momentum equation, the diffusion and relaxation terms are described by two distinct power-laws. Moreover, we assume that the momentum equation is perturbed by an extra term, which, depending on whether its signal is positive or negative, may account for the presence of a source or a sink within the system. For the associated initial-boundary value problem, we study the existence of weak solutions as well as the large time behavior of the solutions.
  • Kelvin-Voigt equations with anisotropic diffusion, relaxation and damping: Blow-up and large time behavior
    Publication . Antontsev, S.; Oliveira, H. B. de; Khompysh, Kh
    A nonlinear initial and boundary-value problem for the Kelvin-Voigt equations with anisotropic diffusion, relaxation and absorption/damping terms is considered in this work. The global and local unique solvability of the problem was established in (J. Math. Anal. Appl. 473(2) (2019) 1122-1154). In the present work, we show how all the anisotropic exponents of nonlinearity and all anisotropic coefficients should interact with the problem data for the solutions of this problem display exponential and polynomial time-decays. We also establish the conditions for the solutions of this problem to blow-up in a finite time in three different cases: problem without convection, full anisotropic problem, and the problem with isotropic relaxation.