Multi-timescale coupling simulation between turbulence and transport codes using BOUT++ framework

A new coupling model has been developed to integrate multi-scale turbulence and transport simulations, such as ELM bursts and pedestal recovery. As a proof of principle, we first start from a set of three-field two-fluid model equations which includes the pressure, current, and vorticity. The equations are separated into the slowly evolving part of the axisymmetric component by taking a time average of the axisymmetric component. The time-averaged fluxes, which are quadratic in fluctuating quantities, act as drive terms for the time-averaged axisymmetric quantities that determine the plasma transport, and therefore the large-scale evolution of the plasma profiles. Good agreement has been achieved for the solutions obtained by the coupled simulation to direct numerical simulation of the unseparated equations. Multiple ELM cycles have been simulated using the coupling technique in the circular geometry. The axisymmetric component evolution tracks the pedestal pressure profile collapsing in the fast component and the profile recovery between ELMs with additional sources in the slow component. The same coupling technique is applied to a set of six-field two-fluid model equations and results will presented.