Multiscale analysis of interface-driven momentum transport at free-flow and porous medium boundaries
| The interaction between a porous medium and an adjacent free-flow is critical in many natural and engineered systems, yet accurately describing interfacial momentum transport remains a challenge. This study examines such coupled systems at the microscale, using an integrated experimental and theoretical approach. Soft-lithography-fabricated micromodels and micro-Particle Image Velocimetry (µPIV) are used to characterize momentum transport across the fluid-porous interface under isothermal, single-phase, laminar conditions. The influence of porosity on interfacial slip velocity and boundary layer development is examined using ordered porous structures. An explicit analytical solution for interfacial velocity distributions is derived using the Brinkman model, overcoming limitations of classical Stokes-based models that suffer from convergence and truncation issues in high width-to-height ratio rectangular channels. The developed model incorporates a Navier-type boundary condition and introduces an empirical, viscosity-independent correlation for the slip length, validated in Hele-Shaw-type flows with excellent agreement. Notably, both slip velocity and slip length increase monotonically with porosity, highlighting their intrinsic correlation governed by interfacial momentum transfer mechanisms. The study further extends to disordered porous domains, providing, for the first time, two-dimensional velocity field measurements in coupled free-flow and porous systems with random solid-phase distributions. An asymptotic expansion method yields a multiscale analytical solution at the Representative Elementary Volume (REV) scale, resolving both local and averaged dynamics through excess parameter functions that are validated experimentally. Lastly, preliminary results on immiscible two-phase flows lay the groundwork for future multiphase microfluidics in porous systems, establishing a robust experimental pathway for high-resolution imaging and quantitative analysis of interfacial dynamics. |
Light refreshments will be served before the lecture
