  BOUT++ turbulence simulations are conducted for a 60s steady-state long pulse
high \{beta}p EAST grassy ELM discharge. BOUT++ linear simulations show that
the unstable mode spectrum covers a range of toroidal mode numbers from low-n
(n=10~15) peeling-ballooning modes (P-B) to high-n (n=40~80) drift-Alfv\'en
instabilities. Nonlinear simulations show that the ELM crash is trigged by
low-n peeling modes and fluctuation is generated at the peak pressure gradient
position and radially spread outward into the Scrape-Off-Layer (SOL), even
though the drift-Alfv\'en instabilities dominate the linear growth phase.
However, drift-Alfv\'en turbulence delays the onset of the grassy ELM and
enhances the energy loss with the fluctuation extending to pedestal top region.
Simulations further show that if the peeling drive is removed, the fluctuation
amplitude drops by an order of magnitude and the ELM crashes disappear. The
divertor heat flux width is ~2 times larger than the estimates based on the HD
model and the ITPA multi-tokamak scaling (or empirical Eich scaling) due to the
strong radial turbulence transport.
