Recent Progress in BOUT$++$ simulations

BOUT$++$ has been applied for a range of problems, including edge-localized mode (ELM) simulations, flux-driven simulations of an edge transport barrier formation, pedestal MHD turbulence, and validating the magnitude and scaling of the divertor heat load width for C-Mod, DIII-D, NSTX, and EAST. BOUT$++$-PIC simulations supporting RF antenna design show impurity migration pattern from RF sputtering. The latest 3-field 2-fluid BOUT$++$ simulation results demonstrated the linear and nonlinear characteristics of ELMs at different collisionality {\&} electric fields E$_{\mathrm{r}}$ shear via a density scan. The BOUT$++$ simulation results show an emerging understanding of dynamics of ELM crashes and the consistent collisionality scaling of ELM energy losses with the world multi-tokamak database. The impact of radial electric field E$_{\mathrm{r}}$ shear on low-n peeling and high-n ballooning modes is different. The increase E$_{\mathrm{r}}$ shear significantly enhances the linear growth rate of low-n peeling modes at low density, but only weakly impacts on nonlinear saturation amplitudes. In contrast, the increasing E$_{\mathrm{r\thinspace }}$shear leads to large suppression of nonlinear peeling-ballooning saturation amplitudes at high density, but only weakly impacts on their linear growth rates.