Adam J. Amar

One-Dimensional Ablation Using a Full Newton's Method and Finite Control Volume Procedure

The development and verification of a one-dimensional constant density material thermal response code with ablation is presented. The implicit time integrator, control volume finite element spatial discretization, and Newtons method (with an analytical Jacobian) for the entire system of residual equations have been implemented and verified for variable material properties, Q* ablation, and thermochemical ablation problems. Timing studies were performed, and when accuracy is considered, the method developed in this study exhibits significant time savings over the property lagging approach. In addition, maximizing the Newton solvers convergence rate by including sensitivities to the surface recession rate reduces the overall computational time when compared to excluding recession rate sensitivities.

Overview of the CHarring Ablator Response (CHAR) Code

An overview of the capabilities of the CHarring Ablator Response (CHAR) code is presented. CHAR is a one-, two-, and three-dimensional unstructured continuous Galerkin finite-element heat conduction and ablation solver with both direct and inverse modes. Additionally, CHAR includes a coupled linear thermoelastic solver for determination of internal stresses induced from the temperature field and surface loading. Background on the development process, governing equations, material models, discretization techniques, and numerical methods is provided. Special focus is put on the available boundary conditions including thermochemical ablation and contact interfaces, and example simulations are included. Finally, a discussion of ongoing development efforts is presented.

Inverse Heat Conduction Methods in the CHAR Code for Aerothermal Flight Data Reconstruction

Reconstruction of flight aerothermal environments often requires the solution of an inverse heat transfer problem, which is an ill-posed problem of specifying boundary conditions from discrete measurements in the interior of the domain. This paper will present the algorithms implemented in the CHAR code for use in reconstruction of EFT-1 flight data and future testing activities. Implementation nuances will be discussed, and alternative hybrid-methods that are permitted by the implementation will be described. Results will be presented for a number of one-dimensional and multi-dimensional problems

Development and Verification of Enclosure Radiation Capabilities in the CHarring Ablator Response (CHAR) Code

With the recent development of multi-dimensional thermal protection system (TPS) material response codes, the capability to account for surface-to-surface radiation exchange in complex geometries is critical. This paper presents recent efforts to implement such capabilities in the CHarring Ablator Response (CHAR) code developed at NASAs Johnson Space Center. This work also describes the different numerical methods implemented in the code to compute geometric view factors for radiation problems involving multiple surfaces. Verification of the codes radiation capabilities and results of a code-to-code comparison are presented. Finally, a demonstration case of a two-dimensional ablating cavity with enclosure radiation accounting for a changing geometry is shown.