arXiv subjects

Alessandro Munafo

Publications and source records attributed to Alessandro Munafo.

4 recordsLinked to original sources

arXiv2026

From Coils to Surface Recession: Multiphysics Simulation of Ablation in ICP Wind Tunnels

This work presents a multi-solver, coupled computational framework for predicting the thermo-chemical material response of thermal protection systems in inductively coupled plasma (ICP) wind tunnels. The framework integrates a high-fidelity Navier-Stokes plasma solver, an electromagnetic field solver, and a discontinuous-Galerkin material response solver using a partitioned coupling strategy. This enables an ab initio, end-to-end simulation of the 350 kW Plasmatron X facility at the University of Illinois Urbana-Champaign (UIUC), including plasma generation, electromagnetic heating, near-wall thermochemistry, and time-accurate material ablation. The model captures key ICP physics such as vortex-mode recirculation, Joule-heating-driven plasma formation, and Lorentz-force-induced flow confinement, and accurately predicts the transition from subsonic to supersonic jet behavior at low pressures. Validation against cold-wall calorimetry shows that predicted stagnation-point cold-wall heat fluxes fall well within experimental uncertainty, while coupled ablation simulations accurately reproduce measured stagnation temperature histories and recession rates with errors below 12% and 10%, respectively. Remaining discrepancies are attributed to uncertainties in power-coupling efficiency, equilibrium ablation modeling, and material property datasets. Sensitivity analyses reveal that a 10% variation in system efficiency can induce changes of up to 11% in steady- state surface temperature and 17% in recession rate, whereas an equivalent variation in material thermal conductivity results in comparatively minor deviations of about 1.5% and 0.5%, respectively. Overall, the framework demonstrates strong predictive capability for ICP wind tunnel environments and provides a foundation for improved design, interpretation, and planning of hypersonic material testing campaigns.

physics.plasm-ph↗

arXiv2025

Numerical analysis of three-dimensional magnetohydrodynamic effects in an inductively coupled plasma wind tunnel

This paper introduces a three-dimensional model for the 350 kW Plasmatron X inductively coupled plasma facility at the University of Illinois Urbana-Champaign, designed for testing high-temperature materials. Simulations of the facility have been performed using a three-dimensional, multiphysics computational framework, which reveals pronounced three-dimensional characteristics within the facility. The analysis of the plasma and electromagnetic field in the torch region reveals the influence of the helical coils, which cause a non-axisymmetric distribution of the plasma discharge. Additionally, simulations of the torch-chamber configuration at two operating pressures have been conducted to examine the impact of plasma asymmetry in the torch on jet characteristics in the chamber. The results indicate an unsteady, three-dimensional behavior of the plasma jet at high pressure. Spectral Proper Orthogonal Decomposition (SPOD) has been performed on the unsteady flow field to identify the dominant modes and their associated frequencies. At low pressure, a steady, supersonic, nearly axisymmetric plasma jet forms with consistent flow properties, such as temperature and velocity. However, strong non-equilibrium effects at low pressures lead to substantial deviations in species concentrations from axial symmetry despite having an almost axisymmetric distribution for quantities such as velocity and temperatures.

physics.plasm-ph↗

arXiv2023

Multi-physics modeling of non-equilibrium phenomena in inductively coupled plasma discharges: Part I. A state-to-state approach

This work presents a vibrational and electronic state-to-state model for nitrogen plasma implemented within a multi-physics modular computational framework to study non-equilibrium effects in inductively coupled plasma (ICP) discharges. Within the computational framework, the set of vibronic (i.e., vibrational and electronic) master equations are solved in a tightly coupled fashion with the flow governing equations. This tight coupling eliminates the need for invoking any simplifying assumptions when computing the state of the plasma, thereby ensuring a higher degree of physical fidelity. To mitigate computational complexity, a maximum entropy coarse-graining strategy is deployed, effectively truncating the internal state space. The efficacy of this reduced StS model is empirically substantiated through zero-dimensional isochoric simulations. In these simulations, the results obtained from the reduced-order model are rigorously compared against those obtained from the full StS model, thereby confirming the accuracy of the reduced StS framework. The developed Coarse-grained StS model was employed to study the plasma discharge within the VKI Plasmatron facility. Our results reveal pronounced discrepancies between the plasma flow fields obtained from StS simulations and those derived from Local Thermodynamic Equilibrium (LTE) models, which are conventionally used in the simulation of such facilities. The analysis demonstrates a substantial departure of the internal state populations of atoms and molecules from the Boltzmann distribution. These nonequilibrium effects have important consequences on the energy coupling dynamics, thereby impacting the overall morphology of the plasma discharge. A deeper analysis of the results demonstrates that the population distribution is in a Quasi-Steady-State in the hot plasma core.

physics.plasm-ph↗

arXiv2013

A Spectral-Lagrangian Boltzmann Solver for a Multi-Energy Level Gas

In this paper a spectral-Lagrangian method for the Boltzmann equation for a multi-energy level gas is proposed. Internal energy levels are treated as separate species and inelastic collisions (leading to internal energy excitation and relaxation) are accounted for. The formulation developed can also be used for the case of a mixture of monatomic gases without internal energy (where only elastic collisions occur). The advantage of the spectral-Lagrangian method lies in the generality of the algorithm in use for the evaluation of the elastic and inelastic collision operators. The computational procedure is based on the Fourier transform of the partial elastic and inelastic collision operators and exploits the fact that these can be written as weighted convolutions in Fourier space with no restriction on the cross- section model. The conservation of mass, momentum and energy during collisions is enforced through the solution of constrained optimization problems. Numerical solutions are obtained for both space homogeneous and space in- homogeneous problems. Computational results are compared with those obtained by means of the DSMC method in order to assess the accuracy of the proposed spectral-Lagrangian method.

math.NA↗