Six-field two-fluid simulations of peeling–ballooning modes using BOUT++

The simulations on edge-localized modes (ELMs) with six-field peeling–ballooning (P–B) modes using the BOUT++ code are reported in this paper. This six-field model based on the full Braginskii equations are developed to simulate self-consistent turbulence and transport between ELMs. Through the comparison with the previous three-field two-fluid model, P–B instability, ion diamagnetic effects, resistivity and hyper-resistivity are found to be the dominant physics during ELMs. The additional physics, such as ion acoustic waves, thermal conductivities, Hall effects, toroidal compressibility and electron–ion friction, are less important in this process. Through the simulations within different equilibrium temperature profiles but with the same pressure and current, the particle loss of ions contributes the least to the total ELM size. The ELM size will be smaller for low-density cases. The study of convective particle and heat flux indicates that the peak of radial particle flux is obviously related to the ELM filaments burst events. The analysis of radial transport coefficients indicates that the ELM size is mainly determined by the energy loss at the crash phase. The typical values for transport coefficients in the saturation phase after ELM crashes are Dr ∼ 200 m2 s−1, χir ∼ χer ∼ 40 m2 s−1. The turbulent zonal flow, which is mainly driven by the Reynolds stress and suppressed by ion diamagnetic terms, regulates the turbulence from the ELM crash phase to the quasi-steady state for large ELM cases. (paper)