Jorge Ulecia, Juan Carlos

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Jorge Ulecia

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Juan Carlos

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Estadística, Informática y Matemáticas

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ISC. Institute of Smart Cities

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Now showing 1 - 3 of 3
  • PublicationOpen Access
    A splitting uniformly convergent method for one-dimensional parabolic singularly perturbed convection-diffusion systems
    (Elsevier, 2023) Clavero, Carmelo; Jorge Ulecia, Juan Carlos; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    In this paper we deal with solving robustly and efficiently one-dimensional linear parabolic singularly perturbed systems of convection-diffusion type, where the diffusion parameters can be different at each equation and even they can have different orders of magnitude. The numerical algorithm combines the classical upwind finite difference scheme to discretize in space and the fractional implicit Euler method together with an appropriate splitting by components to discretize in time. We prove that if the spatial discretization is defined on an adequate piecewise uniform Shishkin mesh, the fully discrete scheme is uniformly convergent of first order in time and of almost first order in space. The technique used to discretize in time produces only tridiagonal linear systems to be solved at each time level; thus, from the computational cost point of view, the method we propose is more efficient than other numerical algorithms which have been used for these problems. Numerical results for several test problems are shown, which corroborate in practice both the uniform convergence and the efficiency of the algorithm.
  • PublicationOpen Access
    A uniformly convergent scheme to solve two-dimensional parabolic singularly perturbed systems of reaction-diffusion type with multiple diffusion parameters
    (John Wiley & Sons Ltd, 2021) Clavero, Carmelo; Jorge Ulecia, Juan Carlos; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
    In this work, we deal with solving two-dimensional parabolic singularly perturbed systems of reaction-diffusion type where the diffusion parameters at each equation of the system can be small and of different scale. In such case, in general, overlapping boundary layers appear at the boundary of the spatial domain and, because of this, special meshes are required to resolve them. The numerical scheme combines the central difference scheme to discretize in space and the fractional implicit Euler method together with a splitting by components to discretize in time. If the fully discrete scheme is defined on an adequate piecewise uniform Shishkin mesh in space then it is uniformly convergent of first order in time and of almost second order in space. Some numerical results illustrate the theoretical results. © 2020 John Wiley & Sons, Ltd.
  • PublicationOpen Access
    Solving efficiently one dimensional parabolic singularly perturbed reaction¿diffusion systems: a splitting by components
    (Elsevier, 2018) Clavero, Carmelo; Jorge Ulecia, Juan Carlos; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
    In this paper we consider 1D parabolic singularly perturbed systems of reaction¿diffusion type which are coupled in the reaction term. The numerical scheme, used to approximate the exact solution, combines the fractional implicit Euler method and a splitting by components to discretize in time, and the classical central finite differences scheme to discretize in space. The use of the fractional Euler method combined with the splitting by components means that only tridiagonal linear systems must be solved to obtain the numerical solution. For simplicity, the analysis is presented in a complete form only in the case of systems which have two equations, but it can be easily extended to an arbitrary number of equations. If a special nonuniform mesh in space is used, the method is uniformly and unconditionally convergent, having first order in time and almost second order in space. Some numerical results are shown which corroborate in practice the theoretical ones.