Giuseppe Gangemi presents at the 47th IOP Plasma Physics Conference
"Development of a multi-component diffusion fluid solver for two-temperature binary plasma sheath".
Giuseppe Gangemi is persueing his PhD in the DoT group and the von Karman institute on the high resolution modeling of the plasma sheaths. He will present his work at the 47th IOP Plasma Physics virtual Conference (http://plasma2021.iopconfs.org/home) taking place from 6-9 April 2021.
The prediction of arcing in vacuum electronics and the electrical charging of space platforms due to the interaction with the plume of electric thrusters are two aerospace applications where an accurate description of the plasma sheath is crucial. Together with the need of accuracy, complex geometries require computational methods that are also computationally affordable.
In this work we investigate two different approaches to plasma fluid simulations: the multi-fluid, commonly used in the plasma physics community, and the multi-component approach (a generalization of the simpler drift-diffusion model), commonly used in the combustion and re-entry flows community. The former considers the species within the mixture as interpenetrating fluids, solving (under the isothermal assumption) for each fluid one equation for mass conservation and one for momentum conservation; the latter (in this work in its binary diffusion approximation) assumes the plasma as a single fluid with diffusing species, hence solves (in isothermal condition) for one mass conservation equation for each species and only one equation for momentum conservation of the bulk velocity of the plasma. In both models solving for the electrostatic Poisson equation ensures charge conservation inside the domain. The multi-component model offers advantages when simulating mixtures with large number of species as the number of equations (and the model complexity) decreases, with a reduction in computational cost.
In this work we compare the results of the two methods by simulating a one-dimensional discharge with a binary mixture of argon plasma (electrons and positive ions in a uniform bath of argon neutrals). We adapt the boundary conditions from the classic multi-fluid approach and implement a semi-implicit treatment of the electric potential in order to improve performance in terms of stability of the time integration scheme. Different simulations have been performed with different degrees of collisionality in the mixture by changing the gas pressure.
The proposed approach shows good agreement above gas pressure of 10 Pa with a noticeable decrease in the computational complexity; such results pave the way to the development of a full multi-component model that will allow to simulate more complex mixtures.
