Explicit lower bounds for Stokes eigenvalue problems by using nonconforming finite elements (Q1742892)

The authors find explicit lower bounds for exact eigenvalues of 2D Stokes problem. Their analysis is based on a result of the third author on eigenvalue bounds for self-adjoint differential operators. They use FEM along with the usual and enriched Crouzeix-Raviart element. Additionally, they show that such a lower bound has the optimal convergence order when the mesh size decreases to zero. Two illustrative numerical examples are carried out.