Project - Ion irradiation

research activities

hybrid continuum/kinetic solver for chemically reacting flows

combined kinetic approach for DSMC rare events and tail-driven processes

assessment of continuum breakdown in high-speed chemically reacting flows

exploiting the role of defects for enhanced thermoelectric material performance

calibration of DSMC parameters for transport processes in ionized air based on ab initio calculations

The computational kinetics group employs DSMC, deterministic Boltzmann methods and MD to explore and improve modeling for engineering systems ranging from high-altitude, rarefied flows to material modification and material response through irradiation processing.

Some of our current research activities include:

The careful treatment of transport properties is of paramount importance to ensure consistency between computational transport models employed in flow solvers, from deterministic methods to stochastic, particle-based methods. Such considerations are important when comparing flowfield solutions between, for example, computational fluid dynamics (CFD) and direct simulation Monte Carlo (DSMC) methods, but consistency is especially critical for use of these methods within hybrid CFD/DSMC frameworks. Simply stated, the same material at the same conditions, should have the same properties where both CFD and DSMC flow solutions are applicable. In the context of hybrid solutions, this ensures that the same flow problem is being solved by each method and the differences between the solutions are due to fundamental non-equilibrium processes, rather than differences in the physical models. The DSMC collision cross section model parameters are calibrated for high temperature atmospheric conditions

DSMC study of carbon fiber oxidation in ablative thermal protection systems

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Thermoelectric materials offer a sustainable, potentially green and elegant solution for challenges ranging from energy harvesting to precise temperature control. The wide-scale adoption of thermoelectric technologies has been hindered by low overall conversion efficiencies and high costs. Improvement of thermoelectric performance relies on the optimization of three material parameters: thermal conductivity, electrical conductivity and Seebeck coefficient.

The focus of this work is achieving high figure merit in relatively cheap and simple materials with selective introduction of defect configurations. The first objective of this study would be identify the optimum defect configuration for achieving maximum figure of merit. The next step would involve using strategic material processing techniques like ion irradiation, which offers wide tunability in terms of design parameters for producing stable forms of the determined optimal defect configuration.

Exploiting the role of defects for enhanced thermoelectric material performance

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We gratefully acknowledge funding for this research provided by the National Science Foundation, NASA, AFOSR, DOE, Air Force Research Laboratory and the University of Illinois at Urbana-Champaign.

Computational resources and technical support are provided by NASA through the High-End Computing Capability (HECC) and by DOE through the PSAAP Center.