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BOUT++ workshop 2015
Ben Dudson
York Plasma Institute, Department of Physics,University of York, Heslington, York YO10 5DD, UK
BOUT++ Workshop
14th September 2015
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (1 of 21)
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Ben Dudson, YPI BOUT++ Workshop 2015 welcome (2 of 21)
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Meet outside at the front of the building
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (3 of 21)
Workshop events
Coffee: Morning and afternoon coffee breaks
Lunches: Buffet lunches with sandwiches, hot and cold drinks
Dinner: The workshopdinner will be tonight in theAle House on Walmgate,starting at 7:00pm. Pleasebring cash (around £20).
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (4 of 21)
Miscellaneous
Taxis The phone downstairs in the common area can calllocal numbers. Some taxi companies are
Ebor taxis: 641 441Station taxis: 623 332
WiFi internet access. If you need a guest account please seeme. Connect to eduroam or UoY Setup.
Printing and Fax. If you need anything printed, or faxed,please see Ben or Sharon
Lecture room not locked. Please see Ben about storingvaluables.
Welcome to York, and have a good meeting
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (5 of 21)
Introduction to BOUT++
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (6 of 21)
Background: Transport in the tokamak edge
Plasma edge region criticalto reactor design
Core performanceHeat fluxes to divertorParticle fluxes to first wall
Understanding of transportprocesses incomplete
Leads to uncertainty inpredictions for future devices
*Figure: www.euro-fusion.org/glossary/divertor/
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (7 of 21)
Background: Tokamak divertor exhaust problem
ITER designed for 500MW fusionpower for 50MW input
Of this 500MW, 100MW goes intothe plasma→ 150MW must beexhausted from the plasma
Area available to handle power
A ' 2πRλq/ sinα
R ' 6m α ' 2.5o λ ∼ 2 − 20mm
→ A ' 1.7m2
Power fluxes could be∼ 100MW/m2∼ 10× technological limits!
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (8 of 21)
Background: Tokamak divertor exhaust problem
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (9 of 21)
Background: Tokamak divertor exhaust problem
1T.Eich et.alNucl. Fusion 53 (2013) 093031Ben Dudson, YPI BOUT++ Workshop 2015 welcome (9 of 21)
Background: Tokamak divertor exhaust problem
A solution is thought to exist for ITER, even with λq ∼ 1mmBeyond ITER, a demonstration power plant (DEMO) will needto handle even higher powers in order to be economical(Power increased ×5)Machine cannot be much larger than ITER
Heat flux becomes 500MW/m2 rather than 100MW/m2
“A reliable solution to the problem of heat exhaust isprobably the main challenge towards the realisation ofmagnetic confinement fusion”
– EU-EFDA Report: Fusion Electricity A Roadmap to therealisation of fusion energy (2012)
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (10 of 21)
Tokamak edge simulations
Transition region betweenhot core and materialsurfaces
Complex nonlinear physics:plasma turbulence, neutrals,impurities, material surfaces
Complex geometry:X-points, shaped divertorsurfaces, snowflakeconfigurations,...
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (11 of 21)
BOUT++ development aims to tackle these problems
BOUT++ has been designed(and re-designed) to handle thiscomplicated physics
Curvilinear coordinates andbranch-cuts allow quitegeneral geometries (*)
Extendable code allowsexperimentation withnumerical methods andphysics models
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (12 of 21)
BOUT++ overview
What BOUT++ is:
A toolbox for solving PDEs on parallel computers. Aims toreduce duplication of effort, and allow quick development andtesting of new models
A collection of examples and test cases
Focussed on flute-reduced plasma models in field-alignedcoordinate systems, though has more general capabilities
And is not:
A single plasma model or simulation
A general library of numerical methods. Other libraries likePETSc are available for that
Magic. Appropriate numerical methods depend on theproblem, and must be chosen intelligently by the user
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (13 of 21)
BOUT++: A toolbox for plasma simulations
Collection of useful data types and associated routines.Occupies a middle ground between problem-specific codesand general libraries (e.g. PETSc, Trilinos, Overture,Chombo,...)
Has its origins in the BOUT code123. Re-written andre-designed (at least once) in C++45
Researchers can make use of a (mostly) well tested library ofsimulation code and input / output tools
Greatly reduces the time needed to develop a new simulation
1X.Q. Xu and R.H. Cohen, Contrib. Plasma Phys. 38, 158 (1998)2Xu, Umansky, Dudson, Snyder, CiCP 4, 949-979 (2008)3Umansky, Xu, Dudson et al. Comp. Phys. Comm. 180, 887-903 (2008)4Dudson, Umansky, Xu et al. Comp. Phys. Comm 180, 1467 (2009)5Dudson et al. J. Plasma Phys. (2014).
Preprint: http://arxiv.org/abs/1405.7905Ben Dudson, YPI BOUT++ Workshop 2015 welcome (14 of 21)
http://arxiv.org/abs/1405.7905
Growing BOUT++ community
Open source project, available on github
http://boutproject.github.io
Users in labs and universities in UK, US, China, India, Japan,S.Korea, Denmark,...
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (15 of 21)
http://boutproject.github.io
BOUT++ workshop
Aims of this workshop are to:
Get new users started with using BOUT++
Share experience and expertise in plasma edge modellingand tools
Discuss problems and future work
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (16 of 21)
BOUT++ workshop
Aims of this workshop are to:
Get new users started with using BOUT++
Share experience and expertise in plasma edge modellingand tools
Discuss problems and future work
Outline
Getting started (This afternoon, Tuesday afternoon)
Recent work and developments (This morning, uesdaymorning)
More advanced uses (Tuesday afternoon)
Divertor modelling activities (Wednesday morning)
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (16 of 21)
Getting started (This afternoon)
Getting started, runningsome “simple” test cases
Heat conduction,turbulence, plasma blobsReading data into Python.Also possible in IDL,Mathematica, Matlab,Octave,...Some new tools forrunning simulations andvisualising outputs
Introduction to where theimportant bits of the codeare
Data handling, PDEsolvers, integrationAnatomy of a physicsmodel
0 10 20 30 40 50 60 70Radius [ρs ]
0
10
20
30
40
50
60
70
Bino
rmal
dire
ctio
n [ρs]
0.990
1.035
1.080
1.125
1.170
1.215
1.260
0 50 100 150 200 250X index
0
50
100
150
200
250
Z in
dex
Normalised plasma density fluctuation n
0.96
0.72
0.48
0.24
0.00
0.24
0.48
0.72
0.96
1.20
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (17 of 21)
Applications in tokamak physics
Filaments / blobsTransport of heat and particles in SOL2D examples run on a laptop
Edge turbulenceFormation of blobsNear SOL heat transport (λq)
Divertor simulationsSpreading of particle and power fluxesto surfacesInteraction with neutral gas anddetachment
Pedestal physics and ELMsGyro-fluid models to capture FLR,Landau damping, and drift resonanceeffectsL-H transition physicsStability and nonlinear dynamics
0 50 100 150 200 250
0
50
100
150
200
250
Density [×1018m−3 ]
0.00
0.06
0.12
0.18
0.24
0.30
0.36
0.42
0.48
0.54
0.60
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (18 of 21)
Recent developments
Many people contributing fixes, features and improvements:George Breyiannis, David Dickinson, Luke Easy, Erik Grinaker, JoeHenderson, Peter Hill, Jarrod Leddy, Michael Loiten, Peter Naylor,Jens Madsen, John Omotani, Kevin Savage, David Schwoerer,Luke Townley, Nick Walkden (apologies for omissions)
In the last year(git diff --stat)
534 files changed
22674 insertions(+)
47251 deletions(-)
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (19 of 21)
Recent developments
Some of the new features at this workshop are:
Implementation of the Flux Coordinate Independent (FCI)scheme (P.Hill, B.Shanahan)
Implicit-Explicit (IMEX) schemes for time integration(N.Walkden, B.Dudson, D.Dickinson)
Non-orthogonal meshes for realistic tokamak geometries(J.Leddy, N.Walkden)
Interaction with neutral gas (S.Mekkaoui, J.Leddy, B.Dudson)
Finding eigenvector/eigenvalues using SLEPc (D.Dickinson,B.Dudson)
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (20 of 21)
Issues and future work
Increasing time-step size: Often limited by fast electronparallel dynamics to δt < 1/ΩciCalculating the potential φ from vorticity efficiently androbustly
Inclusion of impurities
Development of neutral gas models and divertor turbulencestudies
...
Lots of things to discuss!
Ben Dudson, YPI BOUT++ Workshop 2015 welcome (21 of 21)