itpa, divsol, may 2007: coster et al coster, bonnin, corrigan, wiesen, chankin, zagorski, owen,...
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ITPA, DivSOL, May 2007: Coster et al
Coster, Bonnin, Corrigan, Wiesen, Chankin, Zagorski, Owen, Rognlien, Kukushkin, Fundamenski, …
With contributions fromHorton, Isler, Krstic, Reiter, Stotler
•Present status
•Lessons learned
•Plans
Edge Code-code benchmarking
ITPA, DivSOL, May 2007: Coster et al
Present status
• Phases– I: D, no drifts– II: D, drifts– III: D+C, no drifts– IV: D+C, drifts
• Code pairs– A: (i) SOLPS (B2-EIRENE) |
(ii) EDGE2D-NIMBUS | (iii) EDGE2D-EIRENE
– B: SOLPS (B2) | UEDGE– C: SOLPS
• (i) SOLPS4 | SOLPS5• (ii) SOLPS5.0 | SOLPS 5.1• (iii) SOLPS5.0 | SOLPS 6.0
• Comparison technique– A: eproc routines based on “tran
files”– B: UEDGE ability to read SOLPS
b2fstate file; moving to MDSplus– C: comparison of MDSplus results
• Status– I A i/ii: done
• iii: in progress – III A: in progress– I B: in progress– III C i: hot topic (Bonnin/Kukushkin)– I C ii: re-done recently– I C iii: needs to be re-done– III C ii: need to be done– III C iii: need to be re-done
ITPA, DivSOL, May 2007: Coster et al
SOLPS (B2-EIRENE) | EDGE2D-NIMBUS
• Same plasma grid• Generated by GRID-
2D (A, B)• Different surfaces seen by
• SOLPS-EIRENE• EDGE2D-NIMBUS• (EDGE2D-EIRENE
matched to EDGE2D-NIMBUS)
• Orthogonal grid from UEDGE (C)
A B
C
ITPA, DivSOL, May 2007: Coster et al
Some observations
1. The importance of flux limiters:
• SOLPS• 0.5e19• Fl=0.15, 0.2, 10.0
2. Unimportance of 5/9 pt stencil
• EDGE2D-NIMBUS• 5pt stencil• 9pt stencil
• SOLPS (5pt stencil)• 0.5e19• Fl=10• Also: good agreement
between SOLPS & EDGE2D-NIMBUS
1
2
SO
LPS
| E
DG
E2D
-NIM
BU
S
ITPA, DivSOL, May 2007: Coster et al
Some observations, II
3. Now started to include EDGE2D-EIRENE
• Cases• EDG2D-NIMBUS (XB)• SOLPS• EDGE2D-NIMBUS (SW)• EDGE2D-EIRENE (SW)• EDGE2D-EIRENE (SW)
• 0.5e19• Fl=10.0
4. D+C, no drifts• Cases
• EDGE2D-NIMBUS• EDGE2D-NIMBUS
(better BC)• SOLPS
• Fl=10
3
4
SO
LPS
| E
DG
E2D
-{N
IMB
US
,EIR
EN
E}
ITPA, DivSOL, May 2007: Coster et al
SOLPS(B2) | UEDGE
• Fluid neutral– More “difficult” than with
kinetic neutrals• Neutral flux limiters
• Atomic physics
• More ad hoc parameters
• Expect geometry closer to the target to play a greater role (5pt vs 9pt)
• Using an orthogonal mesh generated by UEDGE at the moment
ITPA, DivSOL, May 2007: Coster et al
Boundary conditions (D only)
• Core– Neutrals leakage, recycled into
ions– 2.5 MW energy equally divided
between electrons and ions• Outer SOL surface
– Te: 5 cm decay length– Ti: 50 cm decay length– nD+: 5 cm decay length– Gas puff of D0 to control
separatrix electron density• Private flux surface
– Te: 1 cm decay length– Ti: 10 cm decay length– nD+: 5 cm decay length– Leakage for D0
• Targets– Standard sheath boundary
conditions
• Transport coefficients– D: 0.5 m2s-1
e, i: 0.7 m2s-1
• Flux limiters– Electron, Ion thermal: 10
– Viscosity: 0.5
– Neutrals: 21
ITPA, DivSOL, May 2007: Coster et al
Progress …
• Started with fairly large disagreements
• Eliminated some possible causes– Moved to orthogonal mesh
• Reduced disagreements by– Introducing the factor in
the neutral flux limits– Changing to pressure driven
transport for the neutrals in UEDGE
– Implementing the same method for calculating the neutral D’s, ’s
– Using the same atomic
physics
– Switching off a term in
UEDGE which gives a
contribution from
molecular break-up
– Using the same ion
energy recycling
coefficient
– Braginskii/Balescu
– …
21
ITPA, DivSOL, May 2007: Coster et al
Status as of Nov 2006
Midplane profiles as of Nov. ‘06 are reasonably close
Taken from a presentation by Tom Rognlien at ECC, April 2007
Radial distance (m) Radial distance (m)
Te Ti
ni
ng
SO
LPS
| U
ED
GE
ITPA, DivSOL, May 2007: Coster et al
ni
ng
Te Ti
Radial distance (m) Radial distance (m)
Divertor profiles as of Nov. ‘06 differ substantially
Taken from a presentation by Tom Rognlien at ECC, April 2007
SO
LPS
| U
ED
GE
Status as of Nov 2006, II
ITPA, DivSOL, May 2007: Coster et al
Present status
ni ng
TeTi
Radial distance (m) Radial distance (m)
Sep.
SO
LPS
| U
ED
GE
Midplane profiles still fit well
Taken from a presentation by Tom Rognlien at ECC, April 2007
ITPA, DivSOL, May 2007: Coster et al
Present status, II
ning
TeTi
Radial distance (m) Radial distance (m)
Sep.
SO
LPS
| U
ED
GE
Divertor profiles are now much closer with the various corrections noted
Taken from a presentation by Tom Rognlien at ECC, April 2007
ITPA, DivSOL, May 2007: Coster et al
Status• SOLPS EDGE2D-
EIRENE comparisons progressing
• SOLPS-UEDGE comparisons progressing– Challenging some of
the implicitly made assumptions
Status and Plans
Plans• SOLPS-EDGE2D-
EIRENE– D+C– D, drifts
• SOLPS-UEDGE– “complete” D– D+C– D, drifts
A large effort is going into these benchmarks
ITPA, DivSOL, May 2007: Coster et al
Standard SOLPS simulations•Minor variations
•in when the atomic physics files were created•How may points were used in the interpolation table
Barely detectable difference
Changing the physics assumptions had a relatively small effect!
Different atomic physics assumptions have a large effect!
Atomic physics
ITPA, DivSOL, May 2007: Coster et al
Atomic physics, in more detail
Te
n e
Te
n e
Te
n e
Te
n eIonization rate Recombination rate
Electron cooling rate Charge exchange rate
ITPA, DivSOL, May 2007: Coster et al
Atomic physics, in more detail
Ionization rate
Agreement between the data sets – except for the standard rates
used for the fluid model by SOLPS
ITPA, DivSOL, May 2007: Coster et al
Atomic physics, in more detail
Agreement between the data sets – except for the standard rates
used for the fluid model by SOLPS
Recombination rate
ITPA, DivSOL, May 2007: Coster et al
Atomic physics, in more detail
More complicated situation•Ionization driven piece
•Recombination driven piece (plus Bremsstrahlung)
Electron cooling rate
ITPA, DivSOL, May 2007: Coster et al
Atomic physics, in more detail
•B2 used simple formula•Not too bad!
•ADAS: •89: wrong•93: no file•96: file with 0 rates•Now have “ADAS” format data from Horton
Charge exchange rate
ITPA, DivSOL, May 2007: Coster et al
Conclusion: Atomic physics
• Came as a surprise to me that the atomic physics made such a difference– Since this is all D– And I thought that the hydrogen atom was
relatively well understood!
ITPA, DivSOL, May 2007: Coster et al
Backup slides
Update on the UEDGE/SOLPS benchmark activity for edge fluid transport*
Presented at the
ECC Workshop
April 20, 2007
San Diego, CA
* Work performed under the auspices of U.S. DOE by ORNL and the Univ. of Calif. LLNL under contract Nos. DE-AC05-00OR22725 and W-7405-Eng-48.
L.W. Owen, ORNL and T.D. Rognlien, LLNL
X. Bonnin, Univ. Paris, and D.P. Coster, IPP Garching
Owen, RognlienECC April ‘07
Motivation
• US and EU 2D edge-plasma transport codes
– mature, used widely to understand/ interpret tokamak edge
– predict ITER divertor characteristics
– benchmark is official ITPA Activity
• Integration of many plasma, neutral, and atomic physics processes included; nonlinear interactions abound
• Models are effectively the same and use exactly the same mesh
Owen, RognlienECC April ‘07
Strategy: a multi-stage “primacy hierarchy” to more efficiently uncover differences
• Carefully verify equations and coefficients
• UEDGE imports SOLPS solutions and fluxes (reverse process is also straightforward)
• Using SOLPS solution, UEDGE evaluates fluxes and sources; compare to SOLPS fluxes & sources
• After corrections, compare ni,g, Te,i, and u||
(ng, ne,Te)
Simple primacy hierarchy
Level 1 Level 2 Level 3
Eqns. Flux ne(r) Source sp
Owen, RognlienECC April ‘07
Since the APS Nov. ‘06, a number of model differences have been identified and resolved
1. Convective energy transport coefficients differ:• SOLPS typically uses (5/2)nTv and (3/2)nTv||
• UEDGE typically uses 5/2 both places, or (3/2) and (5/2)||
2. Hydrogen atomic physics rates are similar, but diff. matters:• UEDGE uses data from Stotler, ‘96• SOLPS uses
• Electron parallel thermal conductivity differs:
• UEDGE uses Spitzer/Braginskii
• SOLPS uses higher-moment Balescu coeff. - 35% larger(!)
• Nonorthogonal mesh differences motivate first obtaining agreement on an orthogonal mesh
Owen, RognlienECC April ‘07
Similar, but different atomic physics rates can give significant variations in plate parameters
• Ionization and radiation loss rates depend nonlinearly on Te
0
2
4
6
8
10
12
14
16
-0.1 -0.05 0 0.05 0.1 0.15 0.2
s-ssep [m] (outer target)
REFdo no harm
testtest2adas
stotler
1.5
2
2.5
3
3.5
4
4.5
-0.1 -0.05 0 0.05 0.1 0.15 0.2
s-ssep [m] (outer target)
REFdo no harm
testtest2adas
stotler
Variation in SOLPS results for different rate tables
Owen, RognlienECC April ‘07
Midplane profiles as of Nov. ‘06 are reasonably close
Radial distance (m) Radial distance (m)
Te Ti
ni
ng
Owen, RognlienECC April ‘07
Divertor profiles as of Nov. ‘06 differ substantially
ni
ng
Te Ti
Radial distance (m) Radial distance (m)
Owen, RognlienECC April ‘07
Present status: midplane profiles still fit well
ni ng
TeTi
Radial distance (m) Radial distance (m)
Sep.
Owen, RognlienECC April ‘07
Present status: divertor profiles are now much closer with the various corrections noted
ning
TeTi
Radial distance (m) Radial distance (m)
Sep.
Owen, RognlienECC April ‘07
Summary
• Verifying multi-component (integrated) models is a complex and time-consuming process
• Resolving discrepancies at a lower primacy level (i.e., fluxes, sources) is very useful
• Benchmarking process is a powerful way to uncover
– more subtle programing errors
– unrecognized, underappreciated model differences
– sensitivity of solutions to model parameters
EVEN “straightforward” (nonlinear) edge transport codes have many complexities that verification exercises help identify - very important