Constraint energy minimizing generalized multiscale finite element method in the mixed formulation
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AbstractThis paper presents a novel mass-conservative mixed multiscale method for solving flow equations in heterogeneous porous media. The media properties (the permeability) contain multiple scales and high contrast. The proposed method solves the flow equation in a mixed formulation on a coarse grid by constructing multiscale basis functions. The resulting velocity field is mass-conservative on the fine grid. Our main goal is to obtain first-order convergence in terms of the mesh size which is independent of local contrast. This is achieved, first, by constructing some auxiliary spaces, which contain global information that cannot be localized, in general. This is built on our previous work on the generalized multiscale finite element method (GMsFEM). In the auxiliary space, multiscale basis functions corresponding to small (contrast-dependent) eigenvalues are selected. These basis functions represent the high-conductivity channels (which connect the boundaries of a coarse block). Next, we solve local problems to construct multiscale basis functions for the velocity field. These local problems are formulated in the oversampled domain, taking into account some constraints with respect to auxiliary spaces. The latter allows fast spatial decay of local solutions and, thus, allows taking smaller oversampled regions. The number of basis functions depends on small eigenvalues of the local spectral problems. Moreover, multiscale pressure basis functions are needed in constructing the velocity space. Our multiscale spaces have a minimal dimension, which is needed to avoid contrast dependence in the convergence. The method’s convergence requires an oversampling of several layers. We present an analysis of our approach. Our numerical results confirm that the convergence rate is first order with respect to the mesh size and independent of the contrast.
Acceptance Date05/01/2018
All Author(s) ListEric Chung, Yalchin Efendiev, Wing Tat Leung
Journal nameComputational Geosciences
Year2018
Month6
Volume Number22
Issue Number3
PublisherSpringer Verlag (Germany)
Pages677 - 693
ISSN1420-0597
eISSN1573-1499
LanguagesEnglish-United Kingdom
KeywordsHigh-contrast flow problem, Mixed method, Multiscale basis functions, Localization

Last updated on 2020-06-08 at 03:26