New stabilized discretizations for poroelasticity and the Stokes' equations
This work provides a practical solution to numerical instability in poroelasticity simulations, benefiting researchers and engineers using finite element methods for coupled flow and deformation problems.
The authors propose a stabilization technique for the P1-RT0-P0 discretization of Biot's consolidation problem that ensures uniform stability with respect to physical parameters, eliminating volumetric locking. The method is also applied to Stokes' equations, achieving optimal approximation with minimal degrees of freedom.
In this work, we consider the popular P1-RT0-P0 discretization of the three-field formulation of Biot's consolidation problem. Since this finite-element formulation does not satisfy an inf-sup condition uniformly with respect to the physical parameters, several issues arise in numerical simulations. For example, when the permeability is small with respect to the mesh size, volumetric locking may occur. Thus, we propose a stabilization technique that enriches the piecewise linear finite-element space of the displacement with the span of edge/face bubble functions. We show that for Biot's model this does give rise to discretizations that are uniformly stable with respect to the physical parameters. We also propose a perturbation of the bilinear form, which allows for local elimination of the bubble functions and provides a uniformly stable scheme with the same number of degrees of freedom as the classical P1-RT0-P0 approach. We prove optimal stability and error estimates for this discretization. Finally, we show that this scheme can also be successfully applied to Stokes' equations, yielding a discrete problem with optimal approximation properties and with minimum number of degrees of freedom (equivalent to a P1-P0 discretization). Numerical tests confirm the theory for both poroelastic and Stokes' test problems.