Collisional transport across the magnetic field in drift-fluid models

TL;DR

This paper integrates collisional transport into drift-fluid models for magnetically confined plasmas, enabling more accurate turbulence simulations without artificial diffusion and providing a computationally efficient 2D model.

Contribution

It introduces a self-consistent method to include collisional transport in drift-fluid models and develops a simplified, efficient 2D turbulence model for tokamak edge regions.

Findings

Collisional transport causes diffusion of particles, momentum, and pressure.

The simplified 2D model agrees well with the full model in simulations.

The approach eliminates the need for artificial diffusion in turbulence modeling.

Abstract

Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum and pressures in drift-fluid turbulence models and thereby obviate the customary use of artificial diffusion in turbulence simulations. We further derive a computationally efficient, two-dimensional model which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model employs a computational expedient model for collisional transport. Numerical simulations show good agreement between the full and the simplified model for collisional transport.