Fully coupled model for high-temperature ablation and a reactive-Riemann solver for its solution

Ablation is a process of rapid material removal from a solid surface by chemical reactions, sublimation and other erosive processes. Ablation absorbs large quantities of heat, which makes it a desirable process for Thermal Protection Systems (TPS) used on aerospace vehicles that encounter severe thermal environments, and has been in use since the beginning of the Space Age. The ablation process consists of several coupled sub-processes including gas dynamics, heat, and ablative mechanisms at the surface.;Experimental techniques can reproduce some but not all of the parameters of the flight environment, and for this reason numerical modeling has been undertaken to provide greater understanding. The past state of the art has involved modeling only some of the sub-processes with simplifications of the others, which tended to incorrectly predict the thickness of TPS. The computational resources necessary to model all of the sub-processes in a coupled manner have become available.;A tightly coupled mathematical model for the non-charring ablation problem is developed within this dissertation. The Reynolds Transport Theorem (RTT) is used to derive a set of governing equations that takes into account the movement of the ablating surface and the resulting mass transfer.;A set of numerical methods has been developed and/or modified from existing forms. For example, finite volume discretization schemes are modified to allow for arbitrary composition (solid or gas) within a fixed body-fitted computational grid, and a new method called a reactive-Riemann solver is derived to solve the mass transfer across the ablating surface and its movement. Finally, serial and parallel algorithms are developed for the numerical methods.;Individual components of the model and numerical methods are validated against standard test cases. The full solver is used for ablation problems across a range of free-stream and surface conditions, and these results are shown to agree with experimental data. The effect of surface defects on the local ablation rate and process are shown for the first time: a localized defect can greatly enhance the local ablation rate and create a region of sublimation dominated ablation even if the rest of the surface is ablating primarily via oxidation.