Interaction of a circular porous cylinder with an unconfined steady flow at the mesoscopic scale

We investigate the interaction of a circular porous cylinder with a steady unconfined flow based on a mesoscopic One-Domain Approach (ODA) at the Representative Elementary Volume (REV) scale. Unlike classical penalized methods, which impose sharp discontinuities at the fluid-porous interface, our method resolves the transition zone explicitly, using space-dependent porosity and permeability profiles extracted from filtered pore-scale simulations (PSSs). A curvilinear perme- ability framework is introduced, aligning the principal anisotropy directions with the tangential and normal vectors of the cylinder surface, which significantly improves prediction of viscous shear, pressure-driven filtration, and flow penetration. We show that the size and shape of meso- scopic profiles, controlled by the REV, act as a “hydrodynamic buffer” governing momentum transfer, interface penetration, and wake structure. Smaller REVs reproduce reference PSS data accurately, while larger REVs overpredict wake extension and underpredict drag, highlighting the sensitivity of macroscopic forces to the transition zone. Comparisons with conventional penalized models reveal systematic overestimation of drag and underestimation of flow penetration, demon- strating the limitations of abrupt-interface approximations. This approach leverages the scalabil- ity and data-driven nature of PSS-informed profiles, providing a robust, computationally efficient tool for complex flows. The methodology is particularly relevant for applications where interface- resolved hydrodynamics determine performance. Our results emphasize that explicit treatment of the mesoscopic transition zone is critical to capture realistic drag, wake dynamics, and momen- tum transfer, offering a generalizable alternative to traditional macroscopic or penalized ODA models.