High-fidelity modeling of high-enthalpy plasma wind tunnels for hypersonic testing

Kumar, Sanjeev

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https://hdl.handle.net/2142/130023 Copy

Description

Title

High-fidelity modeling of high-enthalpy plasma wind tunnels for hypersonic testing

Author(s)

Kumar, Sanjeev

Issue Date

2025-07-08

Director of Research (if dissertation) or Advisor (if thesis)

Panesi, Marco

Doctoral Committee Chair(s)

Panesi, Marco

Committee Member(s)

• Stephani, Kelly
• Kearney, Sean
• Radovitzky, Raul
• Munafo, Alessandro

Department of Study

Aerospace Engineering

Discipline

Aerospace Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Hypersonics, Inductively coupled plasma, Re-entry plasma, CFD

Abstract

This dissertation presents the development and application of a high-fidelity, multiphysics computational framework for modeling Inductively Coupled Plasma (ICP) wind tunnels, with a particular focus on the Plasmatron X facility at the University of Illinois Urbana-Champaign. The integrated multi-solver approach enables high-fidelity simulations of plasma behavior within ICP facilities, capturing key aspects such as non-equilibrium chemistry, electromagnetics, radiation, three-dimensional effects, and unsteady flow dynamics within a unified computational framework. A state-to-state (StS) investigation of nonequilibrium phenomena in a nitrogen plasma torch has been conducted using a novel coarse-grained StS approach. The simulations reveal significant deviations from Boltzmann equilibrium in vibronic populations, underscoring the necessity of accounting for non-Boltzmann effects to accurately predict plasma states. The study further confirms the validity of the quasi-steady-state (QSS) assumption in the plasma core, enabling the development of a computationally efficient two-temperature (2T) model that qualitatively captures key macroscopic features. Additionally, the analysis demonstrates that the vibrational relaxation time and vibrational energy loss ratio are critical parameters for controlling plasma discharge characteristics, offering a pathway for experimental calibration. Next, an in-depth numerical analysis of radiative processes in the Plasmatron X wind tunnel has been conducted across a wide range of operating conditions using both air and nitrogen gases. The radiation-coupled simulations show that radiative losses become significant above 10 kPa for nitrogen and 20 kPa for air, with nitrogen plasmas exhibiting higher radiative losses due to distinct plasma compositions and dominant radiation mechanisms. The plasma operates in an optically thin regime, allowing most radiation to escape without reabsorption. The study then focuses on three dimensional magnetohydrodynamic phenomena in the Plasmatron X facility, revealing strong departures from axisymmetry in the plasma discharge due to the helical coil design. High-pressure cases display unsteady, three dimensional plasma jets with dominant modes below 500 Hz, aligning with experimental observations. Such unsteadiness and asymmetry challenge conventional axisymmetric diagnostic assumptions, affecting key measurements like heat flux and surface temperature. In contrast, low-pressure cases exhibit steadier, nearly axisymmetric jets, though species distributions remain three-dimensional due to nonequilibrium effects. Finally, an extensive validation against experimental data from the Plasmatron X facility demonstrates the predictive capability of the computational framework. Simulations capture key flow features such as subsonic-to-supersonic transitions, shock structures, and temperature fields, with good agreement against LIF, CARS, and OES measurements and heat flux data. Further validation through coupled and uncoupled material response simulations confirms the framework’s reliability, with coupled cases achieving superior alignment with measured surface temperatures. While both approaches tend to overpredict surface recession rates, coupled simulations consistently come closer to experimental values. Overall, this work advances the state of the art in ICP modeling by providing a robust, validated tool for simulating the complex, coupled physics of plasma wind tunnel environments.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/130023

Copyright and License Information

Copyright 2025 Sanjeev Kumar

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