A tight-coupling scheme sharing minimum information across a spatial interface between gyrokinetic turbulence codes

TL;DR

This paper introduces a new tightly coupled scheme for kinetic turbulence codes across a spatial interface, improving computational efficiency and stability by sharing minimal information and using global boundary conditions.

Contribution

The paper presents a novel coupling scheme that uses a composite distribution function and global boundary conditions, reducing data exchange and enhancing stability in large-scale turbulence simulations.

Findings

The new scheme is more computationally efficient for large-scale simulations.

Coupling via composite distribution functions improves numerical stability.

Sharing minimal information across the interface is effective for turbulence code coupling.

Abstract

A new scheme that tightly couples kinetic turbulence codes across a spatial interface is introduced. This scheme evolves from considerations of competing strategies and down-selection. It is found that the use of a composite kinetic distribution function and fields with global boundary conditions as if the coupled code were one, makes the coupling problem tractable. In contrast, coupling the two solutions from each code across the overlap region is found to be more difficult due to numerical dephasing of the turbulent solutions between two solvers. Another advantage of the new scheme is that the data movement can be limited to the 3D fluid quantities, instead of higher dimensional kinetic information, which is computationally more efficient for large scale simulations on leadership class computers.