Ablation modeling for high speed internal and external flows

Onay, Oğuz Kaan
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.


Adjoint Shape Optimization of Hypersonic Blunt BodiesIncluding the Effect of Graphite Ablation
Onay, Oğuz; Eyi, Sinan (2016-07-11)
One of the aims of the study, is to develop a numerical analysis tool for thermochemical ablation problem under hypersonic flow conditions. The other aim is to include the effects of the graphite ablation to a design optimization tool which uses adjoint method. In this study, IRV2 geometry is selected as the original geometry and optimization study is performed under reacting flow conditions. Drag coefficient of the geometry is reduced without increasing the stagnation point temperature. After the optimizat...
Çelik, Mutlu; Uğur, Ömür; Eyi, Sinan; Department of Scientific Computing (2022-12-30)
In this thesis, open source softwares SU2 Multiphysics and The Porous material Analysis Toolbox (PATO) based on OpenFOAM are used to conduct loosely coupled analysis of hypersonic non-equilibrium flow and thermochemical ablation. Both solvers have become prominent open source softwares with numerous validation and verification cases. NEMO, the non-equilibrium modeling solver of SU2 is used to model chemically reactive and non-equilibrium flows by integrating thermochemistry library of Mutation++. SU2-NEMO s...
Dynamic stiffness-based test systems for viscoelastic material characterization: Design considerations
Özgen, Gökhan Osman; Batihan, Ali Cagri (2012-07-24)
In this paper, several important design issues for viscoelastic material characterization test systems which utilize dynamic stiffness measurements are discussed. These discussions are focused on structural dynamics aspects of the design of these test systems. These test systems are used to experimentally obtain the complex modulus of viscoelastic solids such as rubber, plastics, etc. Various standards exist on dynamic stiffness-based viscoelastic material characterization test methods, which give general g...
Parameter optimization of chemically activated mortaars containing high volumes of pozzolan by statistical design and analysis of experiments
Aldemir, Başak; Saatçioğlu, Ömer; Department of Industrial Engineering (2006)
This thesis illustrates parameter optimization of early and late compressive strengths of chemically activated mortars containing high volumes of pozzolan by statistical design and analysis of experiments. Four dominant parameters in chemical activation of natural pozzolans are chosen for the research, which are natural pozzolan replacement, amount of pozzolan passing 45 æm sieve, activator dosage and activator type. Response surface methodology has been employed in statistical design and analysis of experi...
Nonlinear Vibrations of a Functionally Graded Material Microbeam with Geometric Nonlinearity
Uz, Canan; Ciğeroğlu, Ender (2017-02-02)
In this paper, nonlinear vibration analysis of micro scale functionally graded material (FGM) beams with geometric nonlinearity due to large deflection is studied using modified couple stress theory (MCST). MCST is a nonlocal elasticity theory which includes a material length scale parameter since the size of an atomic microstructure becomes comparable to the length of the microbeam. Equations of motion of the micro scale FGM beam are obtained by using Hamilton's principle. Nonlinear free vibrations of the ...
Citation Formats
O. K. Onay, “Ablation modeling for high speed internal and external flows,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2020.