A spectral mimetic least-squares method for the Stokes equations with no-slip boundary condition

Formulation of locally conservative least-squares finite element methods (LSFEM) for the Stokes equations with the no-slip boundary condition has been a long standing problem. Existing LSFEMs that yield exactly divergence free velocities require nonstandard boundary conditions [3], while methods that admit the no-slip condition satisfy the incompressibility equation only approximately [4, Chapter 7]. Here we address this problem by proving a new non-standard stability bound for the velocity-vorticity-pressure Stokes system augmented with a no-slip boundary condition. This bound gives rise to a norm-equivalent least-squares functional in which the velocity can be approximated by div-conforming finite element spaces, thereby enabling a locally-conservative approximations of this variable. We also provide a practical realization of the new LSFEM using high-order spectral mimetic finite element spaces [15] and report several numerical tests, which confirm its mimetic properties.