Optimally accurate higher-order finite element methods on polytopial approximations of domains with smooth boundaries
For computational scientists using affine meshes for curved domains, this method enables higher-order accuracy without complex curved elements.
This paper develops higher-order finite element methods that achieve optimal accuracy on polytopial approximations of domains with smooth boundaries, overcoming the error from boundary representation. Numerical examples demonstrate optimal H1 and L2 convergence rates.
Meshing of geometric domains having curved boundaries by affine simplices produces a polytopial approximation of those domains. The resulting error in the representation of the domain limits the accuracy of finite element methods based on such meshes. On the other hand, the simplicity of affine meshes makes them a desirable modeling tool in many applications. In this paper, we develop and analyze higher-order accurate finite element methods that remain stable and optimally accurate on polytopial approximations of domains with smooth boundaries. This is achieved by constraining a judiciously chosen extension of the finite element solution on the polytopial domain to weakly match the prescribed boundary condition on the true geometric boundary. We provide numerical examples that highlight key properties of the new method and that illustrate the optimal $H^1$ and $L^2$-norm convergence rates.