Post on 01-Feb-2016
description
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulence, mixing and transport Turbulence, mixing and transport
in magnetized plasmas in magnetized plasmas
Ultimate goal: Predictive modelOdd-Erik Garcia, Odd-Erik Garcia, Volker NaulinVolker Naulin, , Anders H.Anders H. NielsenNielsen,, Jens Juul Rasmussen Jens Juul Rasmussen
Turbulence is found to dominate the transport of plasma across the confining Turbulence is found to dominate the transport of plasma across the confining magnetic field.magnetic field.In the edge region turbulent transport is order of magnitude stronger than In the edge region turbulent transport is order of magnitude stronger than classical – collision dominated – transport.classical – collision dominated – transport.
All lost plasma must go through the edge region!All lost plasma must go through the edge region!
Numerical and theoretical studies of turbulence and transport!Numerical and theoretical studies of turbulence and transport!Purpose:Purpose:Understanding turbulence and the associated anomalous Understanding turbulence and the associated anomalous transport in magnetized plasmastransport in magnetized plasmas
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Content:Content:
A general description of turbulence Turbulence in fluids Turbulence and mixing/transport Turbulence in plasmas, quasi 2-dimensional Vortex structures Vortex structures and transport Plasma edge turbulence: modelling comparison
with experiments Transport of impurities.
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulence?Turbulence?
Every day phenomena: nature --- administration
Leonardo da Vinci : 1452 –1519 van Gogh
Turbolenza
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulence? Turbulence?
Irregularity and randomness
Fluctuations on all scales
E(k) ~ k-5/3
”Unpredictability”
Diffusivity, rapid mixing
Energy cascade, input at large scales – dissipation at small scales
Nonlinearity dominates
A.N. Kolmogorov A.N. Kolmogorov 1903 - 19871903 - 1987
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulence: effective mixerTurbulence: effective mixer
Turbulence Laminar
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulence in a magnetized plasmaTurbulence in a magnetized plasma
ITER
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Plasma turbulencePlasma turbulence The turbulence degrades the confinement:
Turbulent transport is the main cause for loosing plasma across the magnetic field lines
Numerical Tokamak, Dorland et al.
Our turbulence studies are concentrated on edge turbulence
Lost plasma has to go through the edge!
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Plasma Turbulence is ”2-Dim”Plasma Turbulence is ”2-Dim”
Inverse cascade: energy concentrate at large scales.
Vortical structures dominate the dynamics
VortexVortex
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Self-organisation Coherent Self-organisation Coherent structuresstructures
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Dipole vorticesDipole vortices
Vortices of opposite Vortices of opposite vorticity do vorticity do notnot cancel cancel
RedRed : positive vorticity : positive vorticity
BlueBlue : negative vorticity : negative vorticity
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Vortex mergerVortex merger
Like signed vortices Like signed vortices mergemerge
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Vortices trap particlesVortices trap particles
Dipole vorticesDipole vortices
RedRed : positive vorticity : positive vorticity BlueBlue : negative vorticity : negative vorticity
Passive tracer Passive tracer fieldfield
Vortices : transport Vortices : transport barriersbarriers
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
3-Dimentional vortices3-Dimentional vortices
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Vortex ringVortex ring
Vortex ring Vortex ring bubblebubble
Silver ringSilver ring
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Particle dispersion Particle dispersion
Potential
Density
Drift-wave turbulenceDrift-wave turbulence
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Turbulent flux:Turbulent flux:
Particle flux: Γ = n v = n vExB
Flux PDFFlux PDF
The probability distribution function for the plasma flux across the magnetic field is strongly non-Gaussian, i.e., strong bursts are dominating!
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Modelling turbulence at the edgeModelling turbulence at the edge
Two-dimensional dynamics: outboard midplaneTwo-dimensional dynamics: outboard midplane
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Modelling turbulence at the edge Modelling turbulence at the edge
Global model 2D: self consistent evolution of pressure profile
The source region is separated from the loss region, SOL
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Particle flux at the edgeParticle flux at the edge
Strong possitive flux events!
Pdf of edge particle fluxPdf of edge particle flux
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Edge turbulence transport in JETEdge turbulence transport in JET
-20 -10 0 10 20 3010-4
10-3
10-2
10-1
JET #54271
PD
F
ExB / <
ExB>
Large intermittent burstLarge intermittent burst
65.5255 65.5260 65.5265-10
0
10
20
ExB
/ < E
xB>
time (s)
JET #54271
B. Gonçalves: 11th European Fusion Physics Workshop, Heraklion, Crete 8-11 Dec. 2003
. .
Pdf of fluxPdf of flux
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Edge transport eventsEdge transport events
Bursts of density and heat are released and propagate far out in the SOL
Strong lasting effect on plasma facing components
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Blobs in ExperimentBlobs in ExperimentAlcator C-Mod (Alcator C-Mod (O. Grulke et al 2004)O. Grulke et al 2004)
H-alpha light: proportional to density. CCD: Looking along B-fieldH-alpha light: proportional to density. CCD: Looking along B-field
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Blobs aligned with B-fieldBlobs aligned with B-fieldMast, Culham UK Mast, Culham UK (Kirk et al 2005)(Kirk et al 2005)
H-alpha light,H-alpha light,
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Impurity transport.Impurity transport.
3-Dim simulations, full geometry, flux-tube coordinated
Global variations self-consistent profiles
Turbulent transport statistics; transport barriers
Impurities are also transported by the turbulence.
Modelled by passive tracer transport: e.g., trace tritium experiments
Poloidal projection of 3-D turbulent field
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Dynamics of impurity densityDynamics of impurity density
Projected from a 3D fluxtube simulation onto a poloidal cut
Timespan: 120 μs
Poloidal Asymmetry in transport, pinch
Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005Turbulence, mixing and transport, June 21, 2005
Film blobs:Film blobs:Summary:Summary:
We are approaching models with results that can be compared directly with experiments!
In hot plasmas: Dynamics of fast ions, alphas etc. Confinement!
-------------------------------------------------- Spændende Eksamensprojekter og PhD
Projekter. Med ITER mange nye udfordringer.