  The effect of toroidal rotation on both turbulent and neoclassical transport
of tungsten (W) in tokamaks is investigated using the flux-driven, global,
nonlinear 5D gyrokinetic code GYSELA. Nonlinear simulations are carried out
with different levels of momentum injection that drive W to the supersonic
regime, while the toroidal velocity of the main ions remains in the subsonic
regime. The numerical simulations demonstrate that toroidal rotation induces
centrifugal forces that cause W to accumulate in the outboard region,
generating an in-out poloidal asymmetry. This asymmetry enhances neoclassical
inward convection, which can lead to central accumulation of W in cases of
strong plasma rotation. The core accumulation of W is mainly driven by inward
neoclassical convection. However, as momentum injection continues,
roto-diffusion, proportional to the radial gradient of the toroidal velocity,
becomes significant and generate outward turbulent flux in the case of ion
temperature gradient (ITG) turbulence. Overall, the numerical results from
nonlinear GYSELA simulations are in qualitative agreement with the theoretical
predictions for impurity transport, as well as experimental observations.
