MHD modeling of a DIII-D low-torque QH-mode discharge and comparison to observations

摘要

Extended-MHD modeling of DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614(2002)] quiescent H-mode (QH-mode) discharges with nonlinear NIMROD [C. R.Sovinec et al., J. Comput. Phys. 195, 355 (2004)] simulations saturates into aturbulent state but does not saturate when the steady-state flow inferred frommeasurements is not included. This is consistent with the experimentalobservations of the quiescent regime on DIII-D. The simulation with flowdevelops into a saturated turbulent state where the n=1 and 2 toroidal modesbecome dominant through an inverse cascade. Each mode in the range of n=1-5 isdominant at a different time. Consistent with experimental observations duringQH-mode, the simulated state leads to large particle transport relative to thethermal transport. Analysis shows that the amplitude and phase of the densityand temperature perturbations differ resulting in greater fluctuation-inducedconvective particle transport relative to the convective thermal transport.Comparison to magnetic-coil measurements shows that rotation frequencies differbetween the simulation and experiment, which indicates that more sophisticatedextended-MHD two-fluid modeling is required.