Session: 03-09-01: Materials for Extreme Environments

Paper Number: 190205

190205 - Stochastic Permeability Modeling for Thermal Protection System Design. 

Thermal protection system (TPS) offers reliable protection against extreme heat load from the aerothermal environment experienced during atmospheric entry. TPS undergoes multistage processes to relieve thermal stress, including pyrolysis, coking, and oxidation. Permeability of the TPS material is crucial during the pyrolysis stage, as it is the main driver that dictates transport of pyrolysis gas through the material. Therefore, a thorough understanding in the material’s permeability enables optimal and reliable TPS design. When developing a material response (MR) code for TPS designing, permeability values are required for wide ranges of material porosities and lengthscales. This is because the material’s structure evolves as pyrolysis and in-depth oxidation occurs, altering its porosity, as well as different scales which the MR code is leveraged to. Additionally, existing entry modeling tools suffer from high uncertainty caused by the material stochasticity stemming from inherent manufacturing-induced variability. To address these challenges, a semi-parametric model is developed for FiberForm, a porous, anisotropic carbon preform widely used for TPS like phenolic impregnated carbon ablator (PICA). This model was trained on rarefied flow data generated via direct simulation Monte Carlo (DSMC) on FiberForm microstructures digitized through X-ray computed tomography (XRCT). For a given set of porosity and lengthscale, the model can accurately predict permeability distributions across all principal components. By providing a continuous and differentiable formulation, the model can easily be incorporated into MR codes, as well as delivering permeability values for wide ranges of porosities and lengthscales. Furthermore, this model takes account a structural stochastic nature of FiberForm, quantifying necessary uncertainties for improved entry system modeling frameworks.

Presenting Author: Savio Poovathingal University of Kentucky

Presenting Author Biography: Dr. Savio Poovathingal is an Associate Professor and Lighthouse Beacon Foundation Scholar in the Mechanical and Aerospace Engineering Department at the University of Kentucky. Poovathingal specializes in developing computational tools to solve multi-scale problems in gas-surface interactions pertaining to hypersonic flows.