Coupled Vlasov and two-fluid codes on GPUs

TL;DR

This paper introduces a coupled Vlasov and two-fluid simulation approach for collisionless plasmas, leveraging GPU acceleration to efficiently model large domains with detailed velocity distribution data in key regions.

Contribution

It presents a novel coupling method that does not assume specific distribution functions and achieves significant speed-up using GPUs, enabling detailed kinetic-fluid plasma simulations.

Findings

Achieved a 20x speed-up with GPU implementation.

Demonstrated effective coupling without assuming Maxwellian distributions.

Validated the approach on the GEM reconnection challenge.

Abstract

We present a way to combine Vlasov and two-fluid codes for the simulation of a collisionless plasma in large domains while keeping full information of the velocity distribution in localized areas of interest. This is made possible by solving the full Vlasov equation in one region while the remaining area is treated by a 5-moment two-fluid code. In such a treatment, the main challenge of coupling kinetic and fluid descriptions is the interchange of physically correct boundary conditions between the different plasma models. In contrast to other treatments, we do not rely on any specific form of the distribution function, e.g. a Maxwellian type. Instead, we combine an extrapolation of the distribution function and a correction of the moments based on the fluid data. Thus, throughout the simulation both codes provide the necessary boundary conditions for each other. A speed-up factor of around 20 is achieved by using GPUs for the computationally expensive solution of the Vlasov equation and an overall factor of at least 60 using the coupling strategy combined with the GPU computation. The coupled codes were then tested on the GEM reconnection challenge.