Sensitivity Analyses of Thermochemical Kinetics for Radiating Ablative Nonequilibrium Hypersonic Flows

Global sensitivity analyses and uncertainty quantification are used to estimate input parameter contributions to the total variance of a quantity of interest. This work provides methods and results attempting to quantify how thermochemical reaction rate parameters affect infrared radiance uncertainty along the initial trajectory of the IRV-2 vehicle. Results from a baseline case involving a coupled nonequilibrium hypersonic flow and material response simulation as well as multiple uncoupled nonequilibrium radiation simulations are provided. Hundreds of simulations are used to provide quantity of interest sensitivity and uncertainty propagation metrics. Several sparse linear regression algorithms are employed in conjunction with a nonintrusive polynomial chaos collocation approach to identify the most significant uncertain thermochemical kinetics parameters. Reaction rate parameters involving the dissociation of nitrogen via Zel’dovich mechanisms, nitric oxide dissociation, and CN-O and CO-N exchange reactions are the most significant contributors to uncertainty in participating medium infrared radiance throughout the flow domain. Near-infrared sensitivities ([Formula: see text]) exhibit the most variation across the vehicle body, where carbon exchange reactions involving CN and CO comprise the majority of variance contributions. Infrared participating medium radiance uncertainty propagation yields similar results, where the majority of participating medium radiance uncertainty resides near the stagnation point.