Accueil Imprimer Annuaire Plan du site Crédits Fil RSS du site Twitter Plans d'accès Contacts Annuaire Webmail Intranet Logo

Accueil > A propos du LPP > Communication > Actualités archivées > 2022 > A moment model that captures non-Maxwellian electron energy distribution function effects in partially-ionized plasmas

A moment model that captures non-Maxwellian electron energy distribution function effects in partially-ionized plasmas

Researchers of the low-temperature plasma group at LPP working on electric propulsion have proposed a fluid model that self-consistently captures non-Maxwellian electron energy distribution functions (EEDFs) in partially-ionized plasmas. The work is published in the “Editor’s pick” collection of Physics of Plasmas.

Electrons in partially-ionized plasmas often do not follow a Maxwellian distribution due to the collisions with a much colder gas, spatial inhomogeneities, and the presence of electromagnetic fields (See figure 1). However, most of the fluid models for plasma discharges are based on the local approximation (that assumes that the electric forces are locally balanced by the collisions with the gas) or simplify the collisional exchange terms (by assuming a constant collision frequency or a Maxwellian distribution).

JPEG - 942.3 ko
Figure 1
Mesures expérimentales de l’EEDF réalisées au LPP d’une décharge d’argon. En supposant une fonction de distribution maxwellienne (à gauche), la queue de la distribution est surestimée. Alternativement, le modèle aux moments d’ordre élevé est capable de capturer la forme de l’EEDF.

In this work, we propose a macroscopic model that, in addition to electron particle, momentum and energy conservation equations, solves the evolution equations for the heat flux vector and the contracted fourth moment. The article shows that by solving fourth moment equation, we are able to self-consistently capture non-Maxwellian distribution functions as seen in experiments and in kinetic simulations (see fig. 2). In addition, novel non-local transport phenomena are found by the model. They are due to spatial gradients of the EEDF, which is beyond the local-field assumption. The collisional terms in the equations are solved exactly by considering elastic, inelastic and ionization collisional processes. The model is computationally less expensive than kinetic solvers.

JPEG - 658.5 ko
Figure 2
Comparaison entre les simulations cinétiques (rouge), le modèle aux moments d’ordre élevé (vert) et un modèle qui suppose une fonction de distribution maxwellienne (bleu). Le modèle proposé capture quantitativement la fonction de distribution comme celle simulée avec un solveur cinétique.

Voir en ligne : A. Alvarez Laguna, B. Esteves, A. Bourdon, and P. Chabert, Phys. Plasmas 29, 083507 (2022)

Dans la même rubrique :


transparent
CNRS Ecole Polytechnique Sorbonne Université Université Paris-Saclay Observatoire de Paris
transparent
©2009-2022 Laboratoire de Physique des Plasmas (LPP)

Mentions légales
Exploitant du site : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Hébergeur : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Directeur de la publication : Dominique Fontaine (Directrice)