423 research outputs found
Self-consistent coupling of DSMC method and SOLPS code for modeling tokamak particle exhaust
No full textIn this work, an investigation of the neutral gas flow in the JET sub-divertor area is presented, with respect to the interaction between the plasma side and the pumping side. The edge plasma side is simulated with the SOLPS code, while the sub-divertor area is modeled by means of the direct simulation Monte Carlo (DSMC) method, which in the last few years has proved well able to describe rarefied, collisional flows in tokamak sub-divertor structures. Four different plasma scenarios have been selected, and for each of them a user-defined, iterative procedure between SOLPS and DSMC has been established, using the neutral flux as the key communication term between the two codes. The goal is to understand and quantify the mutual influence between the two regions in a self-consistent manner, that is to say, how the particle exhaust pumping system controls the upstream plasma conditions. Parametric studies of the flow conditions in the sub-divertor, including additional flow outlets and variations of the cryopump capture coefficient, have been performed as well, in order to understand their overall impact on the flow field. The DSMC analyses resulted in the calculation of both the macroscopic quantities—i.e. temperature, number density and pressure—and the recirculation fluxes towards the plasma chamber. The consistent values for the recirculation rates were found to be smaller than those according to the initial standard assumption made by SOLPS
Simulation of neutral gas flow in the JET sub-divertor
No full textThe present work presents a numerical study of the neutral gas dynamics in the JET sub-divertor. A complex model of the sub-divertor geometry is implemented and successful comparisons between corresponding numerical and experimental data have been performed. The experimental data represent the neutral gas pressure obtained by a sub-divertor pressure gauge. The recently developed Divertor Gas Simulator (DIVGAS) which is based on the Direct Simulation Monte Carlo (DSMC) method is applied. DIVGAS is able to predict the behaviour of the flow including macroscopic quantities of practical interest as for instance the pressure, temperature and bulk velocity. The non-linear feedback of the sub-divertor gas flow on the divertor plasma vicinity is not taken into account. For all presented plasma cases, the deduced flow pattern is non -isothermal and covers the free molecular up to the transition flow regime. Furthermore, for low intermediate and high divertor density simulations, recirculation effects occur through gaps between the vertical target tiles, which seem to be two order of magnitude less compared with the recycling ion flux onto the divertor walls. (C) 2017 Elsevier B.V. All rights reserved
Numerican and experimental investigation of rarefied gas flows over the whole range of the Knudsen number
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