Abstract Details
Abstracts
Author: Kyle J. Bunkers
Requested Type: Poster
Submitted: 2019-02-21 17:31:37
Co-authors: C.R. Sovinec
Contact Info:
University of Wisconsin-Madison
1500 Engineering Drive
Madison, WI 53706
USA
Abstract Text:
Vertical Displacement Events (VDEs) are of concern at ITER because they can create large forces and heat loads on the first wall. In order to understand VDE dynamics and estimate potential damage, accurate models of VDEs are required. This is challenging because conductive currents link plasma halo regions and boundary structures, and a full model would require handling edge physics such as radiation and neutral dynamics, sheath physics, and plasma-material interaction. Using boundary conditions consistent with these processes is one way of improving VDE computation models. Previous axisymmetric calculations have shown the halo current distribution to be dependent on thermal boundary conditions [Bunkers and Sovinec BAPS 62, No.~12 (2017)]. In addition, sheath effects can be modeled in fluid equations by implementing boundary conditions consistent with a magnetic presheath at the edge [Loizu, et al., Phys.~Plasmas 19, 122307]. Accurate representation of the plasma halo region is also important because the parallel thermal conductivity there is directly related to the plasma halo temperature, which influences plasma resistivity and motion. Because the plasma halo is low temperature and collisional, a Braginskii closure is expected to accurately model thermal and viscous effects in this region. The NIMROD code is being used to investigate the importance of the magnetic presheath Chodura-Bohm velocity boundary condition and of the Braginskii closures. The addition of the Chodura-Bohm condition versus the standard zero velocity boundary condition substantially changes the flow velocity profile, producing smoother flows into the wall. Relative to computations with fixed thermal conductive coefficients, computations with Braginskii thermal conduction predict a larger current bump with a longer current quench.
*This effort is supported by the U.S. Dept. of Energy, award numbers DE-FG02-06ER54850 and DE-SC0018001.
Comments:
