TY - JOUR T1 - A Nonconforming P2 and Discontinuous P1 Mixed Finite Element on Tetrahedral Grids AU - Zhang , Shangyou JO - Advances in Applied Mathematics and Mechanics VL - 4 SP - 1259 EP - 1274 PY - 2025 DA - 2025/05 SN - 17 DO - http://doi.org/10.4208/aamm.OA-2023-0316 UR - https://global-sci.org/intro/article_detail/aamm/24061.html KW - Quadratic finite element, nonconforming finite element, mixed finite element, Stokes equations, tetrahedral grid. AB -

A nonconforming $P_2$ finite element is constructed by enriching the conforming $P_2$ finite element space with seven $P_2$ nonconforming bubble functions (out of fifteen such bubble functions on each tetrahedron). This spacial nonconforming $P_2$ finite element, combined with the discontinuous $P_1$ finite element on general tetrahedral grids, is inf-sup stable for solving the Stokes equations. Consequently, such a mixed finite element method produces optimal-order convergent solutions for solving the stationary Stokes equations. Numerical tests confirm the theory.