1 / 26

Turbulence, mixing and transport in magnetized plasmas

Turbulence, mixing and transport in magnetized plasmas.

harva
Download Presentation

Turbulence, mixing and transport in magnetized plasmas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Turbulence, mixing and transport in magnetized plasmas Turbulence is found to dominate the transport of plasma across the confining magnetic field.In the edge region turbulent transport is order of magnitude stronger than classical – collision dominated – transport.All lost plasma must go through the edge region! Numerical and theoretical studies of turbulence and transport!Purpose:Understanding turbulence and the associated anomalous transport in magnetized plasmas Predictive model Ultimate goal: Odd-Erik Garcia, Volker Naulin, Anders H.Nielsen, Jens Juul Rasmussen Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  2. 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, 2005 Turbulence, mixing and transport, June 21, 2005

  3. Turbulence? Every day phenomena: nature --- administration Leonardo da Vinci : 1452 –1519 van Gogh Turbolenza Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  4. Turbulence? A.N. Kolmogorov 1903 - 1987 Irregularity and randomness Fluctuations on all scales ”Unpredictability” Diffusivity, rapid mixing E(k) ~ k-5/3 Nonlinearity dominates Energy cascade, input at large scales – dissipation at small scales Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  5. Turbulence: effective mixer Turbulence Laminar Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  6. Turbulence in a magnetized plasma ITER Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  7. Plasma turbulence The turbulence degrades the confinement: Turbulent transport is the main cause for loosing plasma across the magnetic field lines Our turbulence studies are concentrated on edge turbulence Lost plasma has to go through the edge! Numerical Tokamak, Dorland et al. Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  8. Plasma Turbulence is ”2-Dim” Vortex Inverse cascade: energy concentrate at large scales. Vortical structures dominate the dynamics Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  9. Self-organisation Coherent structures Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  10. Dipole vortices Red : positive vorticity Blue : negative vorticity Vortices of opposite vorticity do not cancel Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  11. Vortex merger Like signed vortices merge Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  12. Vortices trap particles Dipole vortices Passive tracer field Red : positive vorticity Blue : negative vorticity Vortices : transport barriers Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  13. 3-Dimentional vortices Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  14. Vortex ring Vortex ring bubble Silver ring Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  15. Particle dispersion Potential Density Drift-wave turbulence Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  16. Turbulent flux: Flux PDF Particle flux: Γ = n v = n vExB 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, 2005 Turbulence, mixing and transport, June 21, 2005

  17. Modelling turbulence at the edge Two-dimensional dynamics: outboard midplane Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  18. 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, 2005 Turbulence, mixing and transport, June 21, 2005

  19. Particle flux at the edge Pdf of edge particle flux Strong possitive flux events! Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  20. Edge turbulence transport in JET Pdf of flux Large intermittent burst B. Gonçalves: 11th EuropeanFusion Physics Workshop, Heraklion, Crete 8-11 Dec. 2003 . Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  21. Edge 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, 2005 Turbulence, mixing and transport, June 21, 2005

  22. Blobs in ExperimentAlcator C-Mod (O. Grulke et al 2004) H-alpha light: proportional to density. CCD: Looking along B-field Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  23. Blobs aligned with B-fieldMast, Culham UK (Kirk et al 2005) H-alpha light, Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  24. Impurity transport. Impurities are also transported by the turbulence. Modelled by passive tracer transport: e.g., trace tritium experiments 3-Dim simulations, full geometry, flux-tube coordinated Global variations self-consistent profiles Poloidal projection of 3-D turbulent field Turbulent transport statistics; transport barriers Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

  25. Dynamics 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, 2005 Turbulence, mixing and transport, June 21, 2005

  26. Film blobs: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. Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005 Turbulence, mixing and transport, June 21, 2005

More Related