Global gyrofluid simulations of turbulence in tokamak plasmas

Global flux-driven gyrofluid simulations of internal transport barrier formation by external torque in weak magnetic shear configuration

“…describing the Landau damping process [22], where v th = T i0 /m i is ion thermal velocity. Terms with V neo ∥ = BV neo θ /B θ in equations ( 3) and (4) are introduced to generate the neoclassical poloidal flow [8,23], where B θ is the poloidal field and V neo θ = (1.17/eB) θ • b × ∇ ⟨T i ⟩ represents the neoclassical poloidal velocity [24]. Here, θ is the unit vector in poloidal direction and ⟨•⟩ means a flux-surface average.…”

“…The dissipative effect of the missing FLR terms are modeled by the hyper-viscous terms with the operator µ hv ∇ 4 ⊥ in equations (1)−(4). Linear and nonlinear simulations are performed by varying µ hv , whose results are compared to those of global gyrokinetic ones for code verification in [8]. With an appropriate hyper-viscosity (µ hv = 1), GF2-BOUT++ produces reasonable linear and nonlinear results on ion temperature gradient (ITG) mode except for the residual ZF effect [28].…”

“…With an appropriate hyper-viscosity (µ hv = 1), GF2-BOUT++ produces reasonable linear and nonlinear results on ion temperature gradient (ITG) mode except for the residual ZF effect [28]. Following [8], we use the fixed hyperviscosity µ hv = 1 [8] in this work. More detailed descriptions on the performance, reliability, and limitations of the code can be found in [8].…”

“…Following [8], we use the fixed hyperviscosity µ hv = 1 [8] in this work. More detailed descriptions on the performance, reliability, and limitations of the code can be found in [8].…”

“…To investigate the physical mechanisms behind the ITB formation in KSTAR, we employ a global flux-driven simulation code [8] which is capable of calculating plasma profile evolution in the presence of external heat and momentum sources/sinks. The code has been developed based on a gyrofluid model using the BOUT++ framework [9].…”