ITPA, DivSOL, May 2007: Coster et al Coster, Bonnin, Corrigan, Wiesen, Chankin, Zagorski, Owen, Rognlien, Kukushkin, Fundamenski, … With contributions

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


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


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


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


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}


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


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


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


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


ni

ng

Te Ti


Divertor profiles as of Nov. ‘06 differ substantially


SO

LPS

| U

ED

GE

Status as of Nov 2006, II


Present status

ni ng

TeTi


Sep.

SO

LPS

| U

ED

GE

Midplane profiles still fit well



Present status, II

ning

TeTi


Sep.

SO

LPS

| U

ED

GE

Divertor profiles are now much closer with the various corrections noted



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


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


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



Ionization rate

Agreement between the data sets – except for the standard rates

used for the fluid model by SOLPS



Agreement between the data sets – except for the standard rates

used for the fluid model by SOLPS

Recombination rate



More complicated situation•Ionization driven piece

•Recombination driven piece (plus Bremsstrahlung)

Electron cooling rate



•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


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!


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


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


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


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


Midplane profiles as of Nov. ‘06 are reasonably close


Te Ti

ni

ng


Divertor profiles as of Nov. ‘06 differ substantially

ni

ng

Te Ti



Present status: midplane profiles still fit well

ni ng

TeTi


Sep.


Present status: divertor profiles are now much closer with the various corrections noted

ning

TeTi


Sep.


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

Documents

ITPA, DivSOL, May 2007: Coster et al Coster, Bonnin, Corrigan, Wiesen, Chankin, Zagorski, Owen, Rognlien, Kukushkin, Fundamenski, … With contributions