Abstractions and Automated Algorithms for Mixed Domain Finite Element Methods
Abstractions and automated algorithms for mixed domain finite element methods CÉCILE DAVERSIN-CATTY, Simula Research Laboratory, Norway CHRIS N. RICHARDSON, BP Institute, University of Cambridge, United Kingdom ADA J. ELLINGSRUD, Simula Research Laboratory, Norway MARIE E. ROGNES, Simula Research Laboratory, Norway Mixed dimensional partial differential equations (PDEs) are equations coupling unknown fields defined over domains of differing topological dimension. Such equations naturally arise in a wide range of scientific fields including geology, physiology, biology and fracture mechanics. Mixed dimensional PDEs arealso commonly encountered when imposing non-standard conditions over a subspace of lower dimension e.g. through a Lagrange multiplier. In this paper, we present general abstractions and algorithms for finite element discretizations of mixed domain and mixed dimensional PDEs of co-dimension up to one (i.e. nD-mD with jn −mj 6 1). We introduce high level mathematical software abstractions together with lower level algorithms for expressing and efficiently solving such coupled systems. The concepts introduced here have alsobeen implemented in the context of the FEniCS finite element software. We illustrate the new features through a range of examples, including a constrained Poisson problem, a set of Stokes-type flow models and a model for ionic electrodiffusion. CCS Concepts: • Mathematics of computing → Solvers; Partial differential equations; • Computing methodologies → Modeling methodologies. Additional Key Words and Phrases: FEniCS project, mixed dimensional, mixed domains, mixed finite elements 1 INTRODUCTION Mixed dimensional partial differential equations (PDEs) are systems of differential equations coupling solution fields defined over domains of different topological dimensions. Problem settings that call for such equations are in abundance across the natural sciences [27, 47], in multi-physics problems [13, 48], and in mathematics [8, 29].
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