Ablation modeling for high speed internal and external flows

Thesis Type: Doctorate

Institution Of The Thesis: Middle East Technical University, Faculty of Engineering, Department of Aerospace Engineering, Turkey

Approval Date: 2020

Student: Oğuz Kaan Onay

Supervisor: SİNAN EYİ


In this thesis study, the ablation of graphitic materials is modeled and two different analysis tools are developed. In the first model, the computations are conducted with a decoupled approach. Secondly, a more generalized calculation method is introduced via coupling the flow field and solid conduction analysis codes. In the modeling studies, both the gas and solid domains are assumed to be axisymmetric and the physical domains are discretized with structured finite volume cells. For the flow field analyses, Godunov type approximate Riemann solvers are used for the convective flux calculations and the gradient terms of the viscous fluxes are calculated with the help of grid transformation metrics. Mass diffusion terms are included in the Navier-Stokes equations. Baldwin-Lomax, Baldwin-Barth and Spalart-Allmaras turbulence models are implemented and the results are compared for the coupled approach. A linear solver is developed for the computation of gas phase chemical reaction source terms. The effects of the solid thermal properties with temperature are not neglected in the computations. The models are tested for hypersonic air and Solid Rocket Motor (SRM) nozzle flow conditions. Wall equilibrium is assumed for graphite in air problem and an implicit solver is developed for the calculation of surface species mass fractions rather than using previously prepared lookup tables. Both equilibrium and finite rate surface thermochemistry approaches are tested for the internal flows of the SRM nozzles.