18 research outputs found
Turbulence and structure formation in complex plasmas and fluids
The formation and evolution of nonlinear and turbulent dynamical structures
in two-dimensional complex plasmas and fluids is explored by means of
generalised (drift) fluid simulations. Recent numerical results on turbulence
in dusty magnetised plasmas, strongly coupled fluids, semi-classical
("quantum") plasmas and in rotating quantum fluids are reviewed and discussed
Flux surface shaping effects on tokamak edge turbulence and flows
Shaping of magnetic flux surfaces is found to have a strong impact on
turbulence and transport in tokamak edge plasmas. A series of axisymmetric
equilibria with varying elongation and triangularity, and a divertor
configuration are implemented into a computational gyrofluid turbulence model.
The mechanisms of shaping effects on turbulence and flows are identified.
Transport is mainly reduced by local magnetic shearing and an enhancement of
zonal shear flows induced by elongation and X-point shaping.Comment: 10 pages, 11 figures. Submitted to Physics of Plasma
The collisional drift wave instability in steep density gradient regimes
The collisional drift wave instability in a straight magnetic field
configuration is studied within a full-F gyro-fluid model, which relaxes the
Oberbeck-Boussinesq (OB) approximation. Accordingly, we focus our study on
steep background density gradients. In this regime we report on corrections by
factors of order one to the eigenvalue analysis of former OB approximated
approaches as well as on spatially localised eigenfunctions, that contrast
strongly with their OB approximated equivalent. Remarkably, non-modal phenomena
arise for large density inhomogeneities and for all collisionalities. As a
result, we find initial decay and non-modal growth of the free energy and
radially localised and sheared growth patterns. The latter non-modal effect
sustains even in the nonlinear regime in the form of radially localised
turbulence or zonal flow amplitudes.Comment: accepted at Nuclear Fusio
TIFF: Gyrofluid Turbulence in Full-f and Full-k
A model and code (TIFF) for isothermal gyrofluid computation of
quasi-two-dimensional interchange and drift wave turbulence in magnetized
plasmas with arbitrary fluctuation amplitudes (full-f) and arbitrary
polarization wavelengths (full-k) is introduced. The model reduces to the
paradigmatic Hasegawa-Wakatani model in the limits of small turbulence
amplitudes (delta-f), cold ions (without finite Larmor radius effects), and
homogeneous magnetic field. Several solvers are compared for the generalized
Poisson problem, that is intrinsic to the full-f gyrofluid (and gyrokinetic)
polarization equation, and a novel implementation based on a dynamically
corrected Fourier method is proposed. The code serves as a reference case for
further development of three-dimensional full-f full-k models and solvers, and
for fundamental exploration of large amplitude turbulence in the edge of
magnetized plasmas