InterPore2026

Multi-scale multi-physical modeling of porous ablators

20 May 2026, 15:05

15m

Oral Presentation (MS18) High-temperature heat and mass transfer within porous materials for energy and space (T > 800 °C) MS18

Speaker

Savio Poovathingal (University of Kentucky)

Description

Charring ablators protect spacecraft by coupling low thermal conductivity and endothermic pyrolysis with porous outgassing to produce transpiration cooling. This work establishes an end-to-end multiscale modeling framework for these TPS materials. At the pore scale, we performed detailed DSMC simulations of high-temperature rarefied gas flow through reconstructed fibrous preform geometries. The DSMC results predicted the permeability of these fiber networks in continuum/transitional regimes, matching CFD/theory and laboratory data. Crucially, coupled DSMC simulations with outward-blowing pyrolysis gas and O-atom diffusion showed that the outgassing strongly curtails oxygen penetration (to only ~0.2–0.4 mm depth), significantly reducing net oxidation and surface recession.

At the continuum scale, a finite-volume material-response solver (KATS) was deployed that captures full three-dimensional, anisotropic behavior of porous ablators. As part of this development, we introduced a 3D transient pyrolysis-gas transport model coupled to an orthotropic thermal-conductivity model for the charred composite . This fully coupled solver integrates conductive heat transfer, internal pore-gas convection, and surface pyrolysis/oxidation kinetics in one framework. The studies demonstrated that including internal gas flow and directional conductivity significantly alters predictions of surface temperature and recession relative to simpler 1D or isotropic models. In practice, the macroscale simulations use closure parameters (effective permeability, conductivities, etc.) obtained from the pore-scale DSMC analyses, ensuring consistency across scales.

This strategy tightly couples modeling and experiment across scales. Micro-CT imaging and flow-tube tests supply pore-scale geometry and material properties used in the models, while microscale simulations yield the constitutive relations needed by the continuum solver. For example, it was recently demonstrated that through these multiscale simulations, we were able to match the experimental permeability of fragile TPS preforms, directly informing the simulation inputs. In summary, the multiscale approach blends pore-resolved DSMC, novel material characterization, and 3D continuum CFD into a predictive framework. The integrated results capture how porous microstructure, pyrolysis outflow, and coupled ablation physics combine to determine heat-shield performance.