2d fluid modeling of the asdex upgrade far solf. subba and r. zanino, itm-tf general meeting 2007 1...
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F. Subba and R. Zanino, ITM-TF General Meeting 20071
2D Fluid Modeling of the ASDEX Upgrade Far SOL
ITM Task Force meeting
19-21 September 2007
F. Subba, X. Bonnin1, D. Coster2 and R. Zanino
Dipartimento di Energetica, Politecnico di Torino, Italy1 University of Paris, France
2 IPP Garching, Germany
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F. Subba and R. Zanino, ITM-TF General Meeting 20072
Outline
• Motivation
• Strategy for SOL modelling up to FW
• Models
• Mesh
• Near-far SOL coupling
• Application to ASDEX Upgrade
• Conclusions
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F. Subba and R. Zanino, ITM-TF General Meeting 20073
Motivation (I)
Source:www.eirene.de
Near SOL: well represented
by edge modelling codes
Far SOL: usually not
included
Traditional approach to edge plasma modelling
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F. Subba and R. Zanino, ITM-TF General Meeting 20074
Motivation (II)
Plasma conditions in the far SOL affect
analysis and prediction of ITER ICRH antenna performance
© Copyright Protected by UKAEA, Culham
Science Centre and/or EFDA JET
Limiter plasmas, e.g. First Wall/Limiter
(FTU, IGNITOR, …) and/or divertor start-
up (ITER, …) require FW description
Reasons to focus interest on the far SOL
Source: http://ftu.frascati.enea.it
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F. Subba and R. Zanino, ITM-TF General Meeting 20075
Strategy for SOL Modelling up to FW
• Well developed codes (e.g., B2) exist for near-SOL modelling– Finite Volume schemes
– Structured quadrilateral meshes
• The ASPOEL code is being developed at PoliTo, with emphasis on the far SOL [F. Subba, et al., J. Nucl. Mater. (2007)]– Control Volume Finite Element (CVFE) schemes
(conservative)
– Triangular (in principle unstructured) meshes �increased geometrical flexibility
Use different codes for different SOL regions
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F. Subba and R. Zanino, ITM-TF General Meeting 20076
Models
• ASPOEL
– Two fluids, single ion species + electrons
– Conserve particles, momentum and energy
– No neutrals
• B2 (as used here)
– Reduced to roughly same plasma model as
ASPOEL
– Neutrals (fluid approximation)
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F. Subba and R. Zanino, ITM-TF General Meeting 20077
Mesh (I)
• ASPOEL
• Fills the far SOL (no far PV at present)• ~ 6000 elements
• Triangular
R (m)
Z (m)
• B2
• Fills the near SOL
• ~ 3700 cells
• Quadrilateral
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F. Subba and R. Zanino, ITM-TF General Meeting 20078
Mesh (II)
B
ASPOEL nodes
B2 nodes
ASPOEL meshes are
accurately aligned to B and
interpolate the FW
geometry
Nodes are not coincident at
the interface surface �
interpolation is needed
Outer wall
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F. Subba and R. Zanino, ITM-TF General Meeting 20079
B2-ASPOEL coupling (I)
• B2 and ASPOEL are coupled through an interface magnetic surface
• A consistent solution is produced via an iterative procedure
• Information sharing:– ASPOEL: use B2 computed
fluxes as boundary condition at the interface
– B2: use ASPOEL computed profiles as boundary condition at the interface
From ASPOEL
n, V, T
From B2
Γn, ΓV, ΓE
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F. Subba and R. Zanino, ITM-TF General Meeting 200710
Application: ASDEX Upgrade (I)Near-far SOL interface
Very low
density/vacuum
in the farthest
regions
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F. Subba and R. Zanino, ITM-TF General Meeting 200711
Application: ASDEX Upgrade (II)
Density profile @ outer mid-plane
Excellent
agreement with
experimental data
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F. Subba and R. Zanino, ITM-TF General Meeting 200712
Application: ASDEX Upgrade (III)
Te profile @ outer mid-plane
Qualitative
agreement in
edge and near
SOL.
Issues (also
diagnostic) in far
SOL?!
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F. Subba and R. Zanino, ITM-TF General Meeting 200713
Application: ASDEX Upgrade (IV)
B2 stand-alone
No experimental
data available in
far SOL
Ti profile @ outer mid-plane
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F. Subba and R. Zanino, ITM-TF General Meeting 200714
Conclusions• B2-ASPOEL is proposed as a tool for
global SOL modelling up to the first wall
• An iterative procedure provides continuity of fluxes and primary variables
• First application to ASDEX Upgrade shows reasonable agreement with measured profiles
• Perspective: (JET), (ICRH, coupling to TOPICA), ASPOEL/Eirene, ITER
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F. Subba and R. Zanino, ITM-TF General Meeting 200715
B2-ASPOEL coupling (II)
Convergence of B2-
ASPOEL interface
fluxes
Under investigation
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F. Subba and R. Zanino, ITM-TF General Meeting 200716
Application: ASDEX Upgrade (V)Electron mean free path λe
Connection length ≥ 10 m � Far SOL barely collisional at midplane
Outer midplaneCollisionless SOL region