Direct Numerical Simulations of Two-Fluid Plasma Turbulence

Abstract

Abstract. Electromagnetic turbulence thought to be responsible for anomalous transport in magnetic confinement devices such as tokamaks is very complicated, involving a multitude of physical processes, length and time-scales. It cannot be investigated by traditional linear theories any more than aerodynamic fluid turbulence. The relatively longer wavelength (kxPi <C 1), low frequency (w £± u>* <C w ci ) drift-type modes are, however, susceptible to a direct numerical solution approach pioneered in the case of fluid turbulence by Orszag and Patera. A substantial two-fluid nonlinear code called CUTIE has been developed at Culham in recent years to study the nonlinear saturation and transport consequences of electromagnetic drift wave turbulence in simplified tokamak geometry. This development and some results obtained using such a model are briefly described in this contribution.

Three-dimensional computation of collisional drift wave turbulence and transport in tokamak geometry

“…The electrons are further assumed to be collisional, ν e (∂/∂t), but due to the drift regime only parallel resistive friction and parallel thermal conduction are retained. In future studies this will be subject to correction along the lines of [20,21], limiting collisional damping rates to V e /L where V e is the electron thermal velocity, also allowing Landau damping effects [22] to be retained. The ion parallel velocity is prevented from reaching arbitrarily large parallel wavenumber by inserting artificial parallel viscosity.…”

“…Simulations which are serious about actually computing turbulent transport are going to have to relax drift ordering entirely. An ongoing study which does this properly is under development for global electromagnetic turbulence in cylindrical geometry [21]. The additional numerical development to incorporate the complete fluid dynamics of both electrons and ions in the context of the covariant magnetic flux surface geometry is also underway.…”