Dan Fries, Ph.D.Assistant Professor, University of Kentucky
Friday, November 8th, 2024, 3:00 - 4:00 PM
In Person JH-109
Title: Coherent Anti-Stokes Raman Scattering and Emission Spectroscopic Measurements in an Inductively Coupled Plasma Torch to Characterize High-Enthalpy Flows and Gas-Surface Interactions
ABSTRACT: Measurements in high-enthalpy environments representative of hypersonic flows are challenging due to background radiation, chemical reactions, extreme temperatures, and potential thermal and chemical non-equilibrium. Coherent anti-Stokes Raman scattering (CARS) is a non-linear optical four-wave mixing process that can be used as a gas phase diagnostic and has properties that make it particularly useful for this kind of challenging environment. I will discuss efforts to perform temperature measurements in the range of 3000-7000 Kelvin using CARS in the high-enthalpy flow of an inductively coupled plasma torch. The same technique is used to simultaneously measure temperature and the relative CO to N2 concentration in the boundary layer of a graphite sample exposed to this high-enthalpy flow. These measurements can provide crucial insight into heat transfer and oxidative chemistry affecting the survivability of carbon-based ablative heat shields. Another useful diagnostic for radiating flows is optical emission spectroscopy (OES), which seeks to interpret the information carried by spontaneously emitted photons. I will discuss efforts to leverage OES in the characterization of high-enthalpy flows and plasmas. This involves the development of a Bayesian framework for the evaluation of emission spectroscopic data and direct uncertainty quantification. The utilization of more complex measurement models will eventually allow us to infer otherwise inaccessible physical quantities and their associated uncertainties. These efforts are critical for the development of predictive models and their validation.
BIO: Dan Fries will start as an Assistant Professor in the Mechanical and Aerospace Engineering Department at the University of Kentucky in January 2025. He is currently a research associate at the University of Texas at Austin and holds a Ph.D. in Aerospace Engineering from the Georgia Institute of Technology. Prior to his Ph.D., he obtained Master's degrees from the University of Stuttgart (Germany) and Georgia Tech. Dan is engaged in ongoing research on an inductively coupled plasma torch, high-enthalpy material tests, and plasma kinetics in a capacitive glow discharge. He collaborates closely with researchers at Sandia National Labs and the UT Oden Institute for Computational Engineering and Sciences. His research interests include high-enthalpy and high-speed flows, plasma and combustion chemistry, aerothermochemistry, laser diagnostics and spectroscopy, and the inversion of measurement models. His work is driven by a commitment to advancing space access and hypersonic flight, enabling exploration, and addressing environmental pollution through the study of important fundamental research questions.
