Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code
A new algorithm for toroidal flow shear in a linearly implicit, local δf gyrokinetic code is described. Unlike the current approach followed by a number of codes, it treats flow shear continuously in time. In the linear gyrokinetic equation, time-dependences arising from the presence of flow shear...
| Main Authors: | , , |
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| Format: | Journal article |
| Language: | English |
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Cambridge University Press
2021
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| _version_ | 1797107450252361728 |
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| author | Christen, N Barnes, M Parra, FI |
| author_facet | Christen, N Barnes, M Parra, FI |
| author_sort | Christen, N |
| collection | OXFORD |
| description | A new algorithm for toroidal flow shear in a linearly implicit, local δf gyrokinetic code is described. Unlike the current approach followed by a number of codes, it treats flow shear continuously in time. In the linear gyrokinetic equation, time-dependences arising from the presence of flow shear are decomposed in such a way that they can be treated explicitly in time with no stringent constraint on the time step. Flow shear related time dependences in the nonlinear term are taken into account exactly, and time dependences in the quasineutrality equation are interpolated. Test cases validating the continuous-in-time implementation in the code GS2 are presented. Lastly, nonlinear gyrokinetic simulations of a JET discharge illustrate the differences observed in turbulent transport compared with the usual, discrete-in-time approach. The continuous-in-time approach is shown, in some cases, to produce fluxes that converge to a different value than with the discrete approach. The new approach can also lead to substantial computational savings by requiring radially narrower boxes. At fixed box size, the continuous implementation is only modestly slower than the previous, discrete approach. |
| first_indexed | 2024-03-07T07:14:46Z |
| format | Journal article |
| id | oxford-uuid:0fea2681-ad83-4ca8-9d93-048971439a33 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:14:46Z |
| publishDate | 2021 |
| publisher | Cambridge University Press |
| record_format | dspace |
| spelling | oxford-uuid:0fea2681-ad83-4ca8-9d93-048971439a332022-08-09T15:38:09ZContinuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic codeJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:0fea2681-ad83-4ca8-9d93-048971439a33EnglishSymplectic ElementsCambridge University Press2021Christen, NBarnes, MParra, FIA new algorithm for toroidal flow shear in a linearly implicit, local δf gyrokinetic code is described. Unlike the current approach followed by a number of codes, it treats flow shear continuously in time. In the linear gyrokinetic equation, time-dependences arising from the presence of flow shear are decomposed in such a way that they can be treated explicitly in time with no stringent constraint on the time step. Flow shear related time dependences in the nonlinear term are taken into account exactly, and time dependences in the quasineutrality equation are interpolated. Test cases validating the continuous-in-time implementation in the code GS2 are presented. Lastly, nonlinear gyrokinetic simulations of a JET discharge illustrate the differences observed in turbulent transport compared with the usual, discrete-in-time approach. The continuous-in-time approach is shown, in some cases, to produce fluxes that converge to a different value than with the discrete approach. The new approach can also lead to substantial computational savings by requiring radially narrower boxes. At fixed box size, the continuous implementation is only modestly slower than the previous, discrete approach. |
| spellingShingle | Christen, N Barnes, M Parra, FI Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title | Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title_full | Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title_fullStr | Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title_full_unstemmed | Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title_short | Continuous-in-time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| title_sort | continuous in time approach to flow shear in a linearly implicit local δf gyrokinetic code |
| work_keys_str_mv | AT christenn continuousintimeapproachtoflowshearinalinearlyimplicitlocaldfgyrokineticcode AT barnesm continuousintimeapproachtoflowshearinalinearlyimplicitlocaldfgyrokineticcode AT parrafi continuousintimeapproachtoflowshearinalinearlyimplicitlocaldfgyrokineticcode |