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Pre-Publicación 2021-26

Tomás Barrios, Edwin Behrens, Rommel Bustinza:

Numerical analysis of a stabilized mixed method applied to incompressible elasticity problems with Dirichlet and with mixed boundary conditions

Abstract:

We analyze a new stabilized dual-mixed method applied to incompressible linear elasticity problems, considering two kind of data on the boundary of the domain: nonhomogeneous Dirichlet and mixed boundary conditions. In this approach, we circumvent the standard use of the rotation to impose weakly the symmetry of stress tensor. We prove that the new variational formulation and the corresponding Galerkin scheme are well-posed. We also provide the rate of convergence when each row of the stress is approximated by Raviart-Thomas elements and the displacement is approximated by continuous piecewise polynomials. Moreover, we derive a residual a posteriori error estimator for each situation. The corresponding analysis is quite different, depending on the type of boundary conditions. For known displacement on the whole boundary, we based our analysis on Ritz projection of the error, and requires a suitable quasi-Helmholtz decomposition of functions living in $H(\mathbf{div};\Omega)$. As a result, we obtain a simple a posteriori error estimator, that consists of five residual terms, and results to be reliable and locally efficient. On the other hand, when we consider mixed boundary conditions, these tools are not necessary. Then, we are able to develop an a posteriori error analysis, which provide us of an estimator consisting of three residual terms. In addition, we prove that in general this estimator is reliable, and when the traction datum is piecewise polynomial, locally efficient. In the second situation, we propose a numerical procedure to compute the numerical approximation, at a reasonable cost. Finally, we include several numerical experiments that illustrate the performance of the corresponding adaptive algorithm for each problem, and support its use in practice.

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