State-resolved O2--N2 kinetic model at hypersonic temperatures

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143050/1/6.2017-0659.pd

Master equation simulation of O2-N2 collisions on an ab-initio potential energy surface

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143056/1/6.2017-3163.pd

Kinetic Models of Oxygen Thermochemistry Based on Quasi-Classical Trajectory Analysis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140704/1/1.T4968.pd

Master Equation Study of Vibrational and Rotational Relaxations of Oxygen

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140703/1/1.T4769.pd

Aerothermochemical Nonequilibrium Modeling for Oxygen Flows

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143077/1/1.T4962.pd

View-Factor Approach as a Radiation Model for the Reentry Flowfield

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140427/1/1.A33305.pd

Quantal treatment of O2--Ar vibrational relaxation at hypersonic temperatures

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143097/1/6.2017-0661.pd

Kinetic and continuum modeling of high-temperature oxygen and nitrogen binary mixtures

The present paper provides a comprehensive comparative analysis of thermochemistry models of various fidelity levels developed in leading research groups around the world. Fully kinetic, hybrid kinetic-continuum, and fully continuum approaches are applied to analyze parameters of hypersonic flows starting from the revision of single-temperature rate constants up to the application in 1-D postshock conditions. Comparison of state-specific and two-temperature approaches shows there are very significant and often qualitative differences in the time-dependent nonequilibrium reaction rates and their ratio to the corresponding single-temperature rates. A major impact of the vibration-dissociation coupling on the temporal relaxation of gas properties is shown. For instance, the legacy Park's model has a strongly nonlinear behavior of nonequilibrium reaction rate with vibrational temperature, while a nearly linear shape exists for all state-specific approaches. Analysis of vibrational level populations in the nonequilibrium region shows a profound impact of the numerical approach and the model on the population ratios, and thus vibrational temperatures inferred from such ratios. The difference in the ultraviolet absorption coefficients, calculated by a temperature-based spectral code using vibrational populations from state-specific and kinetic approaches, is found to exceed an order of magnitude

Kinetic and continuum modeling of high-temperature air relaxation

Fully kinetic, vibrationally kinetic, and continuum solvers with varying model fidelity are used in this work to model the high-temperature relaxation of air in 7230 and 15,000 K adiabatic heat baths and a 6 km/s hypersonic flow over a cylinder. The results show significant impact of uncertainties in vibrational relaxation times and reaction rate constants on thermal and chemical relaxation, in particular, on gas temperature and species mole fractions. Most notably, these uncertainties need to be reduced for collisions that include nitric oxide. Order-of-magnitude differences in the nitric oxide dissociation and recombination rates have a large impact on the peak NO mole fraction immediately behind the shock and surface-distributed heat flux, respectively. High-fidelity kinetic and continuum approaches are found to have different reaction channels having the largest effect on species mole fractions and gas temperature: N-2+O exchange and O-2+O dissociation in the former, and NO+O and O-2+N-2 dissociation in the latter

Non-Equilibrium Models for High Temperature Gas Flows

A multi-physical approach is developed for non-equilibrium high enthalpy flows to cover a wide range of interdisciplinary studies. Compressible Navier-Stokes equations are coupled with the chemical model and equation of energy conservation for internal degrees of freedom. The model is capable of accounting for the non-equilibrium dissociation and thermal radiation heat transfer in gas flows. The methodology covers a range of problems from the combustion in subsonic counter-flowing jets to the hypersonic re-entry flows. The present approach attempts to validate the finite rate chemistry mechanisms by modeling the diffusive non-premixed flame of hydrogen at a very low Mach number. The comparison with the artificial compressibility method provides some insights into the compressible Navier-Stokes equations when applied to the flow with nearly constant pressure. High Mach number flow is assessed by a TVD flux splitting scheme applied to model the re-entry of RAM-C II probe. The chemical composition of the air plasma is validated against available experimental and theoretical data. The uncertainty in electron concentration, measured by microwave reflectometers and a Langmuir probe, is examined in the light of chemical reactions, multi-temperature models, boundary conditions and a vibrational-dissociation coupling model. The heating rates are reported on a wide range of trajectory points. A novel approach is used to improve the accuracy of the radiation transfer model based on the ray tracing method by introducing Gauss-Lobatto quadrature and space partition algorithms to the nearest neighbor search. The accuracy of the method is analyzed for hypersonic flows and for laser-supported combustion waves. The approach revealed an increased efficiency of two orders of magnitude when solving the radiation transfer energy along the line of sight. Finally, the concept of the view factor is applied to assess the radiation transfer in high temperature absorbing gas flows. This concept was verified against the ray tracing method and demonstrated several important advantages. The semi-analytical solution for the radiation flux density in axisymmetric geometry is obtained in terms of elliptic integrals. The cost of the radiation transfer model based on the view factor approach in weakly absorbing media is comparable with the cost of the tangent slab approximation and achieves the asymptotic accuracy of the ray tracing method