Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


akron1271035105.pdf (2.88 MB)

ETD Abstract Container

Abstract Header

Fully Coupled Model for High-Temperature Ablation and a Reative-Riemann Solver for its Solution

Mullenix, Nathan Joel
http://rave.ohiolink.edu/etdc/view?acc_num=akron1271035105

Abstract Details

2010, Doctor of Philosophy, University of Akron, Mechanical Engineering.
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.
Alex Povitsky, Dr. (Advisor)
Minel Braun (Committee Member)
Scott Sawyer (Committee Member)
S. I. Hariharan (Committee Member)
Gerald Young (Committee Member)
231 p.
Aerospace Materials; Engineering; Mechanical Engineering
ablation; tightly coupled solver; finite volume scheme; CFD; graphite; oxidation; nitridation; sublimation; hypersonic flight; TPS

Recommended Citations

Citations

  • Mullenix, N. J. (2010). Fully Coupled Model for High-Temperature Ablation and a Reative-Riemann Solver for its Solution [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271035105

    APA Style (7th edition)

  • Mullenix, Nathan. Fully Coupled Model for High-Temperature Ablation and a Reative-Riemann Solver for its Solution. 2010. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1271035105.

    MLA Style (8th edition)

  • Mullenix, Nathan. "Fully Coupled Model for High-Temperature Ablation and a Reative-Riemann Solver for its Solution." Doctoral dissertation, University of Akron, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271035105

    Chicago Manual of Style (17th edition)

akron1271035105
2,325
© 2010, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.