Transpiration cooling has been demonstrated to provide substantial benefits in high heat flux environments. However, the effect of porous microstructure on cooling performance has not yet been systematically investigated. To fill this research gap, this study applies reconstruction techniques to replicate the representative microstructure of fiber-type porous media and develops a precise geometric model of Gyroid-type porous structures grounded in the theory of triply periodic minimal surfaces (TPMS) . Steady-state numerical simulations are conducted to quantitatively characterize the transport coefficients of both porous structures. These derived parameters are then integrated into a two-dimensional macroscopic model to perform transient simulations of transpiration cooling. The simulations are conducted using ANSYS FLUENT, based on the volume of fluid (VOF) multiphase flow model in conjunction with a user-defined scalar (UDS) approach. This approach implements a coupled simulation framework that integrates the non-thermal equilibrium representation of porous media with multiphase flow processes. The results demonstrate that the fiber-type structure maintains a significantly lower skeleton temperature than the Gyroid-type structure under identical cooling conditions, despite exhibiting more pronounced temperature fluctuations. A dynamic analysis of the saturation field reveals that these variations are primarily attributed to the imbalance between evaporative heat transfer and liquid replenishment. This study systematically evaluates the influence of distinct porous microstructures on transpiration cooling performance, establishing a theoretical framework for the optimal design of thermal protection materials operating under extreme heat flux conditions. Future research will explore a wider range of porous structures with complex morphologies, rigorously assess their influence on coolant phase-change dynamics and thermal protection performance, and thereby inform the design and engineering of high-efficiency transpiration cooling systems.

Numerical simulation,Porous media,Transpiration cooling,VOF,UDS