Mean-field and turbulent transport in divertor geometry Davide Galassi In collaboration with: Ph. Ghendrih, P. Tamain, C. Baudoin, H. Bufferand, G. Ciraolo, C. Colin and E. Serre
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Our goal: quantify turbulence in divertor performance Cross-field transport Turbulent transport impacts: 2D transport codes Diffusive • Poloidal asymmetries • experiments Ballistic, filaments Heat deposition on divertor targets • Confinement properties Turbulence in the divertor: still little explored domain TOKAM3X in divertor configuration 2
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Different geometries in TOKAM3X PhD C. Colin COMPASS - like JET - like LIMITER 3
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Similar turbulence properties far from the X-point Ballooning at the LFS midplane Strong fluctuations in PFR (P.Tamain CPP 2014) PDF at LFS midplane LIMITER geometry JET-like geometry 4
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Mean-field and turbulent transport In our simulations, mean-field and turbulent fluxes have comparable order of magnitude Mean-field flux, Turbulent flux already introduced in 2D Beyond linear analysis where transport codes [1,2] Mean fields = const. Xp LFS Top Xp LFS midplane HFS HFS midplane [1] T.D. Rognlien, G.D. Porter, D.D. Ryutov, J. Nucl. Mater. 266–269 (1999) 654 [2] A.V. Chankin, D.P. Coster, J. Nucl. Mater. 438 (2013) S463 5
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Gradients around X-point drive complex patterns of fluxes Divertor acts as a big plasma sink Xp Xp HFS LFS Big density gradients in the poloidal direction Top HFS LFS midplane midplane Complex ExB flux pattern around X-point EDGE SOL SOL PFR 6
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts The global effect of cross-field transport TOKAM3X results JET-like Xp LFS Xp HFS HFS LFS midplane midplane Top COMPASS-like Xp LFS Xp HFS HFS LFS midplane midplane Top (N. Asakura JNM 2007) 7
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Different instabilities can rise in Private Flux Region The Sheath Negative Resistance[4] instability has higher growth rate than the interchange TOKAM2D nonlinear simulations (C. Baudoin PET 2015) Interchange SNR also for negative curvature Kelvin-Helmoltz Objective: include these instabilities in a 2D transport code [3] C. Baudoin, P. Tamain, G. Ciraolo et al. , Proceedings of the 15th International Workshop on Plasma Edge Theory in Fusion Devices. [4] H. Berk, D. Ryutov, and Y. A. Tsidulko, Physics of Fluids B: Plasma Physics (1989-1993) 3(6), 1346–1354 (1991). 8
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts An alternative way to describe turbulence in plasma edge (more details in the talk of G. Ciraolo, tomorrow) Courtesy SimScale Interchange produces turbulence Description still based on empirical coefficients [5] H. Bufferand, G. Ciraolo, Ph. Ghendrih et al. , Proceedings of the 15th International Workshop on Plasma Edge Theory in Fusion Devices. [6] B. Launder, D. Spalding, Computer Methods in Applied Mechanics and Engineering, Vol 3, 1974 9
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts A physical guideline for 2D codes Detailed description of instabilities: TOKAM2D interchange, SNR, Kelvin-Helmoltz Interchange and drift waves TOKAM3X Mean field flows together with turbulent transport Effects related to the 3D geometry TOKAM3X turbulence 1st Courtesy H. principle Bufferand 10
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts CONCLUSIONS Ø First TOKAM3X simulations in divertor configuration show that: • there is an analogy with limiter cases in turbulence properties • mean-field and turbulent fluxes coexist with similar order of magnitude. Complex drift flux patterns are found around the X-point • in different geometries, flows in parallel direction are in qualitative agreement with experiments. Ø Anisothermal, 2-D models give an insight on a wider range of physical phenomena: they show the importance of turbulence in the whole divertor volume . Ø The 2D and 3D turbulent codes can give important physical guidelines to 2D transport codes about different instability mechanisms, with the objective of getting a predictive modelling. 11
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts TOKAM3X model: multi-fluid with drifts Now in isothermal version 12
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts TOKAM3X geometry with X-point Flux surface aligned mesh • Realistic geometry, with coordinates aligned to flux surfaces • EDGE + SOL • Now in isothermal version JET-like geometry 13
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Simulation parameters Physics Geometry 14
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Mean fields in a JET-like geometry 15
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Flux expansion plays a major role JET – like geometry COMPASS – like geometry Poloidal asimmetries in density decay length Same pattern is found on poloidal distribution of density decay length 16
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts Work in progress: comparison with Eich’s expression 17
29th September 2015 | IAEA Headquarters 1st IAEA Technical Meeting on Divertor Concepts 18
Recommend
More recommend
