Title: Nonlinear fluid simulation of particle and heat fluxes during burst of ELMs on DIII-D with BOUT++ code [Fluid Simulation of Particle and Heat Fluxes during Burst of ELMs on DIID with BOUT++ code]

Abstract

In order to study the distribution and evolution of the transient particle and heat fluxes during edge-localized mode (ELM) bursts, a BOUT++ six-field two-fluid model based on the Braginskii equations with non-ideal physics effects is used to simulate pedestal collapse in divertor geometry. We used the profiles from the DIII-D H-mode discharge #144382 with fast target heat flux measurements as the initial conditions for the simulations. Moreover, a flux-limited parallel thermal conduction is used with three values of the flux-limiting coefficient $${{\alpha}_{j}}$$ , free streaming model with $${{\alpha}_{j}}=1$$ , sheath-limit with $${{\alpha}_{j}}=0.05$$ , and one value in between. The studies show that a 20 times increase in $${{\alpha}_{j}}$$ leads to ~6 times increase in the heat flux amplitude to both the inner and outer targets, and the widths of the fluxes are also expanded. The sheath-limit model of flux-limiting coefficient is found to be the most appropriate one, which shows ELM sizes close to the measurements. The evolution of the density profile during the burst of ELMs of DIII-D discharge #144382 is simulated, and the collapse in width and depth of $${{n}_{\text{e}}}$$ are reproduced at different time steps. The growing process of the profiles for the heat flux at divertor targets during the burst of ELMs measured by IRTV (infrared television) is also reproduced by this model. The widths of heat fluxes towards targets are a little narrower, and the peak amplitudes are twice the measurements possibly due to the lack of a model of divertor radiation which can effectively reduce the heat fluxes. The magnetic flutter combined with parallel thermal conduction is found to be able to increase the total heat loss by around 33% since the magnetic flutter terms provide the additional conductive heat transport in the radial direction. Finally, the heat flux profile at both the inner and outer targets is obviously broadened by magnetic flutter. The lobe structures near the X-point at LFS are both broadened and elongated due to the magnetic flutter.

Authors:

Xia, T. Y. ^[1]; Xu, X. Q. ^[2]

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+ Show Author Affiliations

1. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Tue Sep 01 00:00:00 EDT 2015

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:

1321430

Report Number(s):

LLNL-JRNL-665624
Journal ID: ISSN 0029-5515

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 55; Journal Issue: 11; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION; ELM; heat flux; DIIID; simulation