Hi Andrew, In our case we use second order and this is what we prescribe in the session file: <SOLVERINFO> [...] <I PROPERTY="TimeIntegrationMethod" VALUE="DIRKOrder2" /> [...] </SOLVERINFO> Cheers, Margarida On Fri, 27 Jan 2023 at 11:03, Andrew Barnes <A.Barnes2@lboro.ac.uk> wrote:

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Hello everyone,

I'm trying to use the DIRK Time Integration methods in the CompressibleFlowSolver but keep getting an error when trying to specify the order and variant.

If I specify only <I PROPERTY="TimeIntegrationMethod" VALUE="DIRK" /> in SolverInfo it will work perfectly, however I am unsure which order this is using. When I try to define VALUE="DIRKOrder3" or in a separate TIMEINTEGRATIONSCHEME section as below instead, it will produce the error bad_function_call.

<TIMEINTEGRATIONSCHEME> <METHOD> DIRK </METHOD> <ORDER> 3 </ORDER> </TIMEINTEGRATIONSCHEME>

Could anyone clarify:

1. Which order is used for the default "DIRK" model? 2. What would be the correct way to specify the order of DIRK model?

Thank you in advance, Andrew _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users

-- Margarida Moragues Ginard MSCA-IF Researcher *BCAM - *Basque Center for Applied Mathematics Alameda de Mazarredo, 14 E-48009 Bilbao, Basque Country - Spain Tel. +34 946 567 842 mmoragues@bcamath.org | www.bcamath.org/mmoragues *(**matematika mugaz bestalde)*

Hi Andrew, My understanding is if you only specify <I PROPERTY="TimeIntegrationMethod" VALUE="DIRK" />, then the default order will be "1". A DIRK time-integration scheme of order 1 reduces to backward Euler. However, a DIRK time-integration scheme of order 1 is not currently defined in the code base (you have to use BackwardEuler). When use simply use "DIRK", have you checked the solution is being updated? Jacques ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Andrew Barnes <A.Barnes2@lboro.ac.uk> Sent: Friday, January 27, 2023 10:02 AM To: Nektar mail list <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Help with using DIRK Time Integration Methods Some people who received this message don't often get email from a.barnes2@lboro.ac.uk. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> This email from A.Barnes2@lboro.ac.uk originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspam.ic.ac.uk%2FSpamConsole%2FSenders.aspx&data=05%7C01%7Cjacques.xing%40kcl.ac.uk%7Cd9ec82ec8cb2447f1b1808db004dcb93%7C8370cf1416f34c16b83c724071654356%7C0%7C0%7C638104106495972233%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000%7C%7C%7C&sdata=CaeTZxfyaVTGMozEq6XmWU1Eg32WvE5o4hAqwoeLWDo%3D&reserved=0> to disable email stamping for this address. Hello everyone, I'm trying to use the DIRK Time Integration methods in the CompressibleFlowSolver but keep getting an error when trying to specify the order and variant. If I specify only <I PROPERTY="TimeIntegrationMethod" VALUE="DIRK" /> in SolverInfo it will work perfectly, however I am unsure which order this is using. When I try to define VALUE="DIRKOrder3" or in a separate TIMEINTEGRATIONSCHEME section as below instead, it will produce the error bad_function_call. <TIMEINTEGRATIONSCHEME> <METHOD> DIRK </METHOD> <ORDER> 3 </ORDER> </TIMEINTEGRATIONSCHEME> Could anyone clarify: 1. Which order is used for the default "DIRK" model? 2. What would be the correct way to specify the order of DIRK model? Thank you in advance, Andrew