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Fluid, kinetic and hybrid approaches for neutral and trace ion edge transport modelling in fusion devices
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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en
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12
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Nuclear Fusion, Volume 62, issue 8, pp. 1-12
Abstract
Neutral gas physics and neutral interactions with the plasma are key aspects of edge plasma and divertor physics in a fusion reactor including the detachment phenomenon often seen as key to dealing with the power exhaust challenges. A full physics description of the neutral gas dynamics requires a 6D kinetic approach, potentially time dependent, where the details of the wall geometry play a substantial role, to the extent that, e.g., the subdivertor region has to be included. The Monte Carlo (MC) approach used for about 30 years in EIRENE (Reiter et al 2005 Fusion Sci. Technol. 47 172-86), is well suited to solve these types of complex problems. Indeed, the MC approach allows simulating the 6D kinetic equation without having to store the velocity distribution on a 6D grid, at the cost of introducing statistical noise. MC also provides very good flexibility in terms of geometry and atomic and molecular (A&M) processes. However, it becomes computationally extremely demanding in high-collisional regions (HCRs) as anticipated in ITER and DEMO. Parallelization on particles helps reducing the simulation wall clock time, but to provide speed-up in situations where single trajectories potentially involve a very large number of A&M events, it is important to derive a hierarchy of models in terms of accuracy and to clearly identify for what type of physics issues they provide reliable answers. It was demonstrated that advanced fluid neutral models are very accurate in HCRs, and at least an order of magnitude faster than fully kinetic simulations. Based on these fluid models, three hybrid fluid-kinetic approaches are introduced: a spatially hybrid technique, a micro-macro hybrid method, and an asymptotic-preserving MC scheme, to combine the efficiency of a fluid model with the accuracy of a kinetic description. In addition, A&M ions involved in the edge plasma chemistry can also be treated kinetically within the MC solver, opening the way for further hybridisation by enabling kinetic impurity ion transport calculations. This paper aims to give an overview of methods mentioned and suggests the most prospective combinations to be developed.
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| openaire: EC/H2020/633053/EU//EUROfusion Funding Information: The paper presents a joint effort within the EUROfusion Theory and Advanced Simulation Coordination (E-TASC), task ‘NGM’ 2019–2020 and the related O-EIRENE HLST project. 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. W. Van Uytven is funded by a PhD fellowship of the Research Foundation Flanders (FWO). Parts of the work were supported by the Research Foundation Flanders (FWO) under project Grant G078316N. Publisher Copyright: © 2022 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd.
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Borodin, D V, Schluck, F, Wiesen, S, Harting, D, Börner, P, Brezinsek, S, Dekeyser, W, Carli, S, Blommaert, M, Van Uytven, W, Baelmans, M, Mortier, B, Samaey, G, Marandet, Y, Genesio, P, Bufferand, H, Westerhof, E, Gonzalez, J, Groth, M, Holm, A, Horsten, N & Leggate, H J 2022, 'Fluid, kinetic and hybrid approaches for neutral and trace ion edge transport modelling in fusion devices', Nuclear Fusion, vol. 62, no. 8, 086051, pp. 1-12. https://doi.org/10.1088/1741-4326/ac3fe8