Master thesis defense by Aske Olsen
Title: 3D Modelling of Turbulence in a Magnetically Confined Toroidal Plasma
Abstract: In order to accurately describe the dynamics of a fusion plasma 3D-models are essential. However using a simple cartesian coordinate system makes complex fluid models of plasma require a lot of computational time. By creating a a set of coordinates aligned with the magnetic field, the number of grid points in the direction of the magnetic field can be greatly reduced, due to the relatively free motion of charged particles along the magnetic field line.This thesis sets out to investigate plasma dynamics in such a fieldaligned coordinate system. Much emphasis has been put on the geometry of the investigated system, using a modified version of the simple Hasegawa-Wakatani equations derived using the two-fluid equations. Whereas the original Hasegawa-Wakatani equations include few 3Deffects from the magnetic field, the model investigated in this thesis include more, such as magnetic shear.To create a 3D-model with analytical expressions of the metric, a circle equilibrium solution to the Grad-Shafranov equation was assumed, which holds in the large aspect ratio limit.The modified Hasegawa-Wakatani equations was the simulated with the geometric effects of the magnetic field given by the derived metric. To make the numerical simulations the BOUT++ platform was used.