Multidimensional Modeling of Ablation Heat Transfer

Abstract

This paper describes multidimensional modeling of ablation heat transfer with a focus on ablative insulation materials used in rocket motor nozzles. Phenomenology is discussed, and detailed three-dimensional math models are presented along with a finite element solution strategy. Implementation into a computer program named Hero is described, including a description of the parallel processing capability that enables computational support for large finite element models. A validation case is presented using measurement data from booster motors of the space shuttle program. The validation results are quantified in terms of the probabilistic propensity for misprediction of the char depth at varying levels. The validation results show a trend toward the overprediction of char depth by around 4%. The standard deviation of percent misprediction is shown to be between 6 and 16%, depending on boundary condition fidelity. This suggests that accuracy to three standard deviations can be expected to fall in the range of 18–48% for ablation modeling in rocket nozzles. This paper provides an important reference for multidimensional ablation heat transfer analysis and quantification of related modeling uncertainty.