Event Title

Extension of the PECOS Quasi-steady Ablation Toolkit for Uncertainty Propagation

Start Date

1-3-2011 8:00 AM

End Date

3-3-2011 12:30 PM

Description

Low-order models are quite useful for sensitivity analysis and design. This work details work done on adding complementary pieces to the PECOS low-order, quasi-steady-state ablation model to facilitate uncertainty propagation. The PECOS quasi-steady state ablation model is a one-dimensional, quasi-steady-state, algebraic ablation model that uses finite-rate surface chemistry and equilibrium pyrolysis-gas-production submodels to predict surface recession rate. The material response model is coupled to a film-transfer boundary layer model to enable the computation of heat and mass transfer from an ablating surface. For comparison to arc jet data, a simple shock heated gas model is coupled. A coupled model consisting of submodels for the shock heated gases, film heat and mass transfer, and material response is exercised against recession rate data for surface and in-depth ablators. Comparisons are made between the quasi-state-state ablation model and the unsteady ablation code, Chaleur, as well as to other computations for a graphite ablator in arcjet facilities. The simple models are found to compare reasonably well to both the experimental results and the other calculations. Uncertainty propagation using a moment based methods is presented. The method is applied to a number of simplified sample problems, for both univariate and multivariate scenarios. The results of this study are discussed, and conclusions about the utility of the method as well as the properties of the ablation code are drawn.

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Mar 1st, 8:00 AM Mar 3rd, 12:30 PM

Extension of the PECOS Quasi-steady Ablation Toolkit for Uncertainty Propagation

Low-order models are quite useful for sensitivity analysis and design. This work details work done on adding complementary pieces to the PECOS low-order, quasi-steady-state ablation model to facilitate uncertainty propagation. The PECOS quasi-steady state ablation model is a one-dimensional, quasi-steady-state, algebraic ablation model that uses finite-rate surface chemistry and equilibrium pyrolysis-gas-production submodels to predict surface recession rate. The material response model is coupled to a film-transfer boundary layer model to enable the computation of heat and mass transfer from an ablating surface. For comparison to arc jet data, a simple shock heated gas model is coupled. A coupled model consisting of submodels for the shock heated gases, film heat and mass transfer, and material response is exercised against recession rate data for surface and in-depth ablators. Comparisons are made between the quasi-state-state ablation model and the unsteady ablation code, Chaleur, as well as to other computations for a graphite ablator in arcjet facilities. The simple models are found to compare reasonably well to both the experimental results and the other calculations. Uncertainty propagation using a moment based methods is presented. The method is applied to a number of simplified sample problems, for both univariate and multivariate scenarios. The results of this study are discussed, and conclusions about the utility of the method as well as the properties of the ablation code are drawn.