Abstract
Self-consistent full-size turbulent-transport simulations of the divertor and scrape-off-layer (SOL) of existing tokamaks have recently become feasible. This enables the direct comparison of turbulence simulations against experimental measurements. In this work, we perform a series of diverted ohmic L-mode discharges on the tokamak à configuration variable (TCV) tokamak, building a first-of-a-kind dataset for the validation of edge turbulence models. This dataset, referred to as TCV-X21, contains measurements from five diagnostic systems from the outboard midplane (OMP) to the divertor targets - giving a total of 45 one- and two-dimensional comparison observables in two toroidal magnetic field directions. The experimental dataset is used to validate three flux-driven 3D fluid-turbulence models - GBS, GRILLIX and TOKAM3X. With each model, we perform simulations of the TCV-X21 scenario, individually tuning the particle and power source rates to achieve a reasonable match of the upstream separatrix value of density and electron temperature. We find that the simulations match the experimental profiles for most observables at the OMP - both in terms of profile shape and absolute magnitude - while a comparatively poorer agreement is found towards the divertor targets. The match between simulation and experiment is seen to be sensitive to the value of the resistivity, the heat conductivities, the power injection rate and the choice of sheath boundary conditions. Additionally, despite targeting a sheath-limited regime, the discrepancy between simulations and experiment also suggests that the neutral dynamics should be included. The results of this validation show that turbulence models are able to perform simulations of existing devices and achieve reasonable agreement with experimental measurements. Where disagreement is found, the validation helps to identify how the models can be improved. By publicly releasing the experimental dataset and validation analysis, this work should help to guide and accelerate the development of predictive turbulence simulations of the edge and SOL.
| Original language | English |
|---|---|
| Article number | 096001 |
| Journal | Nuclear Fusion |
| Volume | 62 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 2022 |
Funding
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work was supported in part by the Swiss National Science Foundation. This work was partly supported by the U.S. Department of Energy under Grant No. DE-SC0010529. This work was completed within the framework of the EUROfusion Enabling Research ENR-MFE19.EPFL-02, led by Christian Theiler. It was supported by the EUROfusion Theory Simulation Verification and Validation project 3, led by Patrick Tamain. This work was supported by a Grant from the Swiss National Supercomputing Centre (CSCS) under project IDs s1126, s1129, s1028 and s882. The simulations in this work were performed within the 4th and 5th cycles of MARCONI-FUSION HPC. The required computational resources for GBS were allocated under the projects DIVturb and XTurb . We acknowledge PRACE for awarding us access to SuperMUC-NG at GCS@LRZ, Germany. The required computational resources for GRILLIX were allocated under the projects FUA34_EST3D , FUA35_EST3D and FUA35_TSVV3 . TOKAM3X simulations were additionally performed on HPC systems provided by GENCI. The TCV-X21 repository was made possible by several collaborators agreeing to publish their data openly. The data analysis relied on several open-source software packages, particularly the scipy [], numpy [], matplotlib [], xarray , [] Jupyter [], pint and netCDF4 Python packages.
Keywords
- divertor
- simulation
- turbulence
- validation