arXiv subjects

Bernard Parent

Publications and source records attributed to Bernard Parent.

8 recordsLinked to original sources

arXiv2026

Superelastic Heating in Treanor-Gordiets Plasmas: A Unified Analytic Closure

In thermally non-equilibrium plasmas, conventional harmonic models can significantly mispredict superelastic electron heating rates. When the vibrational temperature exceeds the gas temperature ($T_{\rm v}>T_{\rm g}$), these models underestimate energy transfer by several times; conversely, they overestimate heating when $T_{\rm g}>T_{\rm v}$. We show that this discrepancy arises from neglecting the exponential heating from overpopulated, high-lying states in anharmonic Treanor-Gordiets distributions, and their thermodynamic depopulation at high gas temperatures. To resolve this, we derive a closed-form, thermodynamically consistent macroscopic closure based on detailed balance and a second-order Dunham expansion. This unified framework introduces an analytic anharmonic correction factor that captures the kinetic competition between vibrational-vibrational (V-V) up-pumping and vibrational-translational (V-T) relaxation. By predicting the Treanor minimum, this formulation recovers the fidelity of full state-to-state kinetic benchmarks. Ultimately, this model provides a governing equation for heat exchange between electrons and excited states in non-equilibrium environments -- including plasma-assisted combustion and hypersonic flows -- enabling the development of accurate, rate-limited reduced-order models for macroscopic fluid solvers.

physics.plasm-ph↗

arXiv2025

Thermodynamically Consistent Vibrational-Electron Heating: Generalized Model for Multi-Quantum Transitions

Accurate prediction of electron temperature ($T_{\rm e}$) is critical for non-equilibrium plasma applications ranging from hypersonic flight to plasma-assisted combustion. We recently proposed a thermodynamically consistent model for vibrational-electron heating [Phys. Fluids 37, 096141 (2025)] that enforces the convergence of $T_{\rm e}$ to the vibrational temperature ($T_{\rm v}$) at equilibrium. However, the original derivation was restricted to single-quantum transitions, limiting its validity to low-temperature regimes ($T_{\rm e} \lesssim 1.5$ eV). In this Letter, we generalize the model to include multi-quantum overtone transitions, extending its applicability to high-energy regimes. We demonstrate that previous models neglecting hot-band transitions incur a systematic heating error of $\exp(-\theta_{\rm v}/T_{\rm v})$, where $\theta_{\rm v}$ is the characteristic vibrational temperature. This error exceeds 40% when $T_{\rm v}$ is greater than $\theta_{\rm v}$, effectively preventing thermal relaxation. To correct this, we derive a formulation where the total heating rate is a summation of channel-specific cooling rates $Q_{\rm e-v}^{(m)}$, each associated with a quantum jump $m$, scaled by a thermodynamic factor $\exp(m\theta_{\rm v}/T_{\rm e}-m\theta_{\rm v}/T_{\rm v})$. This generalized model preserves thermodynamic consistency by ensuring zero net energy transfer at equilibrium.

physics.plasm-ph↗

arXiv2025

Electron Density Depletion in Reentry Plasma Flows Using Pulsed Electric Fields

Communication blackout due to the plasma layer creates a critical telemetry gap for re-entry vehicles. To mitigate this, we present the first fully-coupled simulation of high-voltage pulsed discharges interacting with a Mach 24 flowfield using an advanced numerical framework. The results demonstrate that the applied electric field generates a large, non-neutral plasma sheath near the cathode, depleting electron density by several orders of magnitude over a distance commensurate with the height of the shock layer. This depletion window effectively reduces the attenuation of a 4 GHz signal from 60% to 4% with a manageable power requirement of 66 W per cm$^2$ of exposed cathode surface. Feasibility analysis indicates that this system can be powered by a battery pack weighing less than 3 kg for a typical re-entry trajectory, with further mass reductions possible through intermittent transmission. A sensitivity analysis reveals that the sheath topology is governed principally by ion kinetics; specifically, corrections to ion mobility at high reduced electric fields lead to enhanced space-charge shielding and a subsequent contraction of the sheath. Conversely, the sheath structure is largely insensitive to the electron mobility model. Finally, we argue that the present drift-diffusion model likely yields a conservative lower bound for mitigation performance. A kinetic approach accounting for ballistic ion transport and non-local ionization would likely predict thicker sheaths and lower attenuation for equivalent power deposition.

physics.plasm-ph↗

arXiv2025

Thermodynamically Consistent Vibrational-Electron Heating: Generalized Derivation for Excited State Populations

Accurate prediction of electron temperature ($T_{\rm e}$) in non-equilibrium plasma flows is critical for applications ranging from hypersonic flight to plasma-assisted combustion. We recently proposed a thermodynamically consistent model for vibrational-electron (V-e) heating [Phys. Fluids 37, 096141 (2025)] which enforces convergence of $T_{\rm e}$ to the vibrational temperature ($T_{\rm v}$) at equilibrium. While the original derivation assumed electron energy loss was dominated by collisions with ground-state molecules, this Letter presents a rigorous generalization of the model. We demonstrate that the heating-to-cooling ratio $\exp(\theta_{\rm v}/T_{\rm e}-\theta_{\rm v}/T_{\rm v})$ with $\theta_{\rm v}$ the characteristic vibrational temperature remains valid even when electron cooling interactions with vibrationally excited states are included. This derivation removes the previous constraint assuming ground-state dominance, thereby extending the model's validity to plasma flows where vibrationally excited populations contribute significantly to electron cooling.

physics.plasm-ph↗

arXiv2025

Electrodeless Magnetohydrodynamic Local Force Generator for Aerocapture

This paper presents a novel magnetohydrodynamics (MHD) system for planetary entry aerocapture. The system is advantaged over previous approaches by having the following two characteristics: (i) it can be deployed locally to one or various flow regions, and (ii) it does not make use of electrodes. Previous MHD systems for planetary entry were either electrodeless global systems or two-electrode local systems. The proposed novel MHD system employs two magnets to establish a current loop resulting in a Faraday electromotive force (EMF). The first magnet is positioned to ensure the magnetic field faces outward from the shell, while the second magnet is oriented to ensure the magnetic field faces inward toward the shell. Preliminary findings demonstrate that when located on the surface of an Earth entry capsule at a flight Mach number of 35, the novel electrodeless MHD system can generate forces several times greater than a two-electrode system while utilizing the same magnetic field strength. The study is conducted entirely through numerical simulation using CFDWARP, a computational fluid dynamics (CFD) code that employs advanced numerical methods allowing for the full coupling between aerodynamics, magnetohydrodynamics, and non-neutral plasma sheaths. The physical model includes an 11-species finite-rate chemical solver including real gas effects, the drift-diffusion model for all charged species, along with an electric field potential equation that satisfies Gauss's law.

physics.plasm-ph↗

arXiv2025

Vibrational-Electron Heating in Plasma Flows: A Thermodynamically Consistent Model

Accurate prediction of electron temperature ($T_{\rm e}$) in non-equilibrium {plasma} flows is critical, yet hampered by inadequate models for electron heating from vibrationally excited states. Prior models often relied on ad-hoc scaling or flawed applications of detailed balance that failed to ensure the convergence of electron temperature and species-specific vibrational temperature ($T_{\rm v}$) at thermal equilibrium. This paper introduces a novel, thermodynamically consistent electron heating model derived rigorously from the principle of detailed balance. By assuming a Boltzmann vibrational distribution and employing an effective activation energy, our approach yields a simple heating-to-cooling ratio of $\exp(\theta_{\rm v}/T_{\rm e}-\theta_{\rm v}/T_{\rm v})$, where $\theta_{\rm v}$ is the characteristic vibrational temperature of the species under consideration. This formulation guarantees that $T_{\rm e}$ correctly converges to $T_{\rm v}$ at equilibrium. A key advantage is that our model can utilize total cooling rates determined from swarm experiments, leading to higher accuracy at low electron temperatures. For re-entry flows, the proposed approach predicts an electron temperature several times lower than previous models which results in improved agreement with some flight test data. These more reliable predictions can significantly enhance the modeling fidelity of plasma-assisted combustion, laser-induced plasmas, and various hypersonic plasma technologies such as electron transpiration cooling or magnetohydrodynamic force generators.

physics.plasm-ph↗

arXiv2024

Impact of Ion Mobility on Electron Density and Temperature in Hypersonic Flows

This study provides the first comprehensive analysis of how ion mobility affects electron density and temperature in hypersonic flows. We compare two ion mobility models: one derived from Gupta-Yos cross-sections, and the other from swarm drift velocity experiments. The ion mobility model significantly alters the plasma density around a hypersonic waverider, with increases of more than twofold observed at low dynamic pressures and high Mach numbers. This is partly due to electron loss through surface catalysis, which depends on ambipolar diffusion scaling with ion mobility. We also derive novel scaling laws that highlight the strong dependence of electron cooling on ion mobility both within the quasi-neutral regions and the non-neutral plasma sheaths. Electron cooling influences the electron temperature across the plasma, leading to a previously unrecognized impact of ion mobility on plasma bulk temperature. This in turn affects plasma density via electron-ion recombination rates which are temperature-dependent. Accurately modeling ion mobility is critical for predicting hypersonic plasma behavior, with important implications for optimizing magnetohydrodynamic technologies and mitigating or exploiting plasma-induced interference with electromagnetic waves.

physics.plasm-ph↗

arXiv2024

Progress in Electron Energy Modeling for Plasma Flows and Discharges

A novel formulation of the electron energy relaxation terms is presented here, which is applicable to plasma flows and discharges wherein the electron temperature could be higher or lower than the gas temperature. It is demonstrated that the electron energy losses due to inelastic collisions can be expressed as a function of only two species-dependent parameters: the reduced electric field and the reduced electron mobility. This formulation is advantageous over previous ones, being simpler to implement and more accurate when experimental data of the reduced electric field and reduced mobility are available. Curve fits to empirical data of these two properties are outlined here for all important air molecular species. The approach accounts for all inelastic electron energy relaxation processes without needing individual cross-sections or rates, reducing potential errors associated with independently handling each process. Several test cases are presented to validate the proposed electron energy source terms including re-entry plasma flows for which the electron temperature is less than the gas temperature, as well as discharges in which the electron temperature reaches values in excess of 30 eV. In all cases, the agreement with experimental data is observed to be very good to excellent, significantly surpassing prior electron energy models for plasma flows

physics.plasm-ph↗