Generación de mallas de hexaedros en geometrías múltiplemente conexas mediante submapping

En este trabajo se presenta una mejora del método de submapping para ampliar su aplicabilidad. El algoritmo de submapping tiene dos limitaciones principales. La primera de ellas es que sólo se puede aplicar en geometrías tales que los ángulos entre las aristas y las caras de la geometría tienen que ser, aproximadamente, múltiplos enteros de π/2. La segunda limitación es que la geometría tiene que ser simplemente conexa. En este trabajo se presenta una extensión del algoritmo de submapping para mallar geometrías con agujeros totalmente interiores.Peer Reviewe

Automatic generation of quadrilateral structured meshes using linear programming and transfinite interpolation

This paper presents an implementation of a structured quadrilateral algorithm called submapping. The meshing procedure splits the geometry into patches and then meshes each patch separately preserving the mesh compatibility between patches via an linear integer problem. The submapping algorithm can only be applied to geometries such that each angle between consecutive edges is, approximately, an integer multiple of ¼=2

An HDG formulation for incompressible and immiscible two-phase porous media flow problems

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International journal of computational fluid dynamics on 27/05/2019, available online at: https://tandfonline.com/doi/abs/10.1080/10618562.2019.1617855We develop a high-order hybridisable discontinuous Galerkin (HDG) formulation to solve the immiscible and incompressible two-phase flow problem in a heterogeneous porous media. The HDG method is locally conservative, has fewer degrees of freedom than other discontinuous Galerkin methods due to the hybridisation procedure, provides built-in stabilisation for arbitrary polynomial degrees and, if the error of the temporal discretisation is low enough, the pressure, the saturation and their fluxes converge with order P+1 in L2-norm, being P the polynomial degree. In addition, an element-wise post-process can be applied to obtain a convergence rate of P+2 in L2-norm for the scalar variables. All of these advantages make the HDG method suitable for solving multiphase flow trough porous media. We show numerical evidence of the convergences rates. Finally, to assess the capabilities of the proposed formulation, we apply it to several cases of water-flooding technique for oil recovery.Peer ReviewedPostprint (author's final draft

Management, design and developement of a mesh generation environment using open source software

In this paper we present an object oriented implementation of a general-purpose mesh generation environment for geometry-based simulations. The aim of this application is to unify available legacy code and new research algorithms in only one mesh generation suite. We focus in two aspects that can be of the general interest for managers, designers and developers of similar projects. On the one hand, we analyze the software engineering practices that we have followed in the management and development process. In addition, we detail and discuss the Open Source tools and libraries that we have used. On the other hand, we discuss the design and the data structure of the environment. In particular, we first summarize the topological and geometrical representation. Second, we detail our implementation of the hierarchical mesh generation structure. Third we present our design to mediate collaboration between classes. Finally, we present some of the mesh generation features to show the capabilities of the environment

Bisecting with optimal similarity bound on 3D unstructured conformal meshes

We propose a new method to mark for bisection the edges of an arbitrary 3D unstructured conformal mesh. For these meshes, the approach conformingly marks all the tetrahedra with coplanar edge marks. To this end, the method needs three key ingredients. First, we propose a specific edge ordering. Second, marking with this ordering, we guarantee that the mesh becomes conformingly marked. Third, we also ensure that all the marks are coplanar in each tetrahedron. To demonstrate the marking method, we implement an existent marked bisection approach. Using this implementation, we mark and then locally refine 3D unstructured conformal meshes. We conclude that the resulting marked bisection features an optimal bound of similarity classes per tetrahedron.This project has received funding from the European Research Council (ERC) under the European Union’sHorizon 2020 research and innovation programme under grant agreement No 715546. This work has also received funding from the Generalitat de Catalunya under grant number 2017 SGR 1731. The work of X. Roca has been partially supported by the Spanish Ministerio de Economía y Competitividad under the personal grant agreement RYC-2015-01633.Peer ReviewedPostprint (published version

Automatically imposing incremental boundary displacements for valid mesh morphing and curving

We present a new incremental mesh morphing method obtained by proposing and discretizing a solution procedure for the continuous morphing problem. Our method seeks a diffeomorphism that transforms an initial domain to a final domain by only prescribing the boundary displacement. To this end, we propose to minimize the distortion of the morphing mapping constrained to satisfy the imposed boundary displacement. To solve this problem, we consider an augmented Lagrangian method in Hilbert spaces that incorporates the boundary condition in the objective function using the Lagrange multipliers and a penalty parameter. The distortion is devised to penalize the appearance of non-invertible mappings and therefore, we do not need to equip our discrete implementation with untangling capabilities. Moreover, we introduce a weight function to improve the quality of the deformation and thus, the robustness of the non-linear solver. The discretization of the continuous augmented Lagrangian method leads to a mesh morphing method suitable for large displacements and rotations of meshes with non-uniform sizing, and mesh curving of highly stretched high-order meshes.Peer ReviewedPostprint (author's final draft

Generación de mallas de hexaedros en geometrías múltiplemente conexas mediante submapping

En este trabajo se presenta una mejora del método de submapping para ampliar su aplicabilidad. El algoritmo de submapping tiene dos limitaciones principales. La primera de ellas es que sólo se puede aplicar en geometrías tales que los ángulos entre las aristas y las caras de la geometría tienen que ser, aproximadamente, múltiplos enteros de π/2. La segunda limitación es que la geometría tiene que ser simplemente conexa. En este trabajo se presenta una extensión del algoritmo de submapping para mallar geometrías con agujeros totalmente interiores.Peer Reviewe

Automatic generation of quadrilateral structured meshes using linear programming and transfinite interpolation

This paper presents an implementation of a structured quadrilateral algorithm called submapping. The meshing procedure splits the geometry into patches and then meshes each patch separately preserving the mesh compatibility between patches via an linear integer problem. The submapping algorithm can only be applied to geometries such that each angle between consecutive edges is, approximately, an integer multiple of ¼=2

High-order hybridizable discontinuous Galerkin formulation for one-phase flow through porous media

We present a stable high-order hybridizable discontinuous Galerkin (HDG) formulation coupled with high-order diagonal implicit Runge–Kuta (DIRK) schemes to simulate slightly compressible one-phase flow through porous media. The HDG stability depends on the selection of a single parameter and its definition is crucial to ensure the stability and to achieve the high-order properties of the method. Thus, we extend the work of Nguyen et al. in J Comput Phys 228, 8841–8855, 2009 to deduce an analytical expression for the stabilization parameter using the material parameters of the problem and the Engquist-Osher monotone flux scheme. The formulation is high-order accurate for the pressure, the flux and the velocity with the same convergence rate of P+1, being P the polynomial degree of the approximation. This is important because high-order methods have the potential to reduce the computational cost while obtaining more accurate solutions with less dissipation and dispersion errors than low order methods. The formulation can use unstructured meshes to capture the heterogeneous properties of the reservoir. In addition, it is conservative at the element level, which is important when solving PDE’s in conservative form. Moreover, a hybridization procedure can be applied to reduce the size of the global linear system. To keep these advantages, we use DIRK schemes to perform the time integration. DIRK schemes are high-order accurate and have a low memory footprint. We show numerical evidence of the optimal convergence rates obtained with the proposed formulation. Finally, we present several examples to illustrate the capabilities of the formulation.This work has been supported by FEDER and the Spanish Government, Ministerio de Ciencia Innovación y Universidades grant project contract PGC2018-097257-B-C33 and Ministerio de Economía y Competitividad under grant BES-2015-072833.Peer ReviewedPostprint (author's final draft

Management, design and developement of a mesh generation environment using open source software

In this paper we present an object oriented implementation of a general-purpose mesh generation environment for geometry-based simulations. The aim of this application is to unify available legacy code and new research algorithms in only one mesh generation suite. We focus in two aspects that can be of the general interest for managers, designers and developers of similar projects. On the one hand, we analyze the software engineering practices that we have followed in the management and development process. In addition, we detail and discuss the Open Source tools and libraries that we have used. On the other hand, we discuss the design and the data structure of the environment. In particular, we first summarize the topological and geometrical representation. Second, we detail our implementation of the hierarchical mesh generation structure. Third we present our design to mediate collaboration between classes. Finally, we present some of the mesh generation features to show the capabilities of the environment