Parameter-robust Preconditioners for the Stokes-Darcy Coupled Problem without Fractional Operators

We consider the Stokes-Darcy coupled problem, which models the interaction between free-flow and porous medium flow.

By enforcing the normal flux continuity interface condition directly within the finite-element spaces, we establish unified well-posedness results for the coupled system under various boundary condition scenarios.

Using the operator preconditioning framework, we develop a parameter-robust preconditioner that avoids the use of fractional operators.

Numerical experiments employing both $H(\operatorname{div})$-conforming and nonconforming finite-element methods are presented to confirm the theoretical findings and demonstrate the robustness of the proposed block preconditioners with respect to the physical parameters and mesh size.