Hi Andrew, Based on the test case for the compressible flow solver: CylinderSubsonic_WeakDG_Implicit.xml The order of the DIRK time-integration scheme is specified as: <I PROPERTY="TimeIntegrationMethod" VALUE="DIRKOrder2" /> The same is applied to other test-cases that use DIRK as an integration scheme which are: * Tests/TimeDependentAbsorption.xml * Tests/implicitSolverCallsSFD_session.xml So in order to change the order of the DIRK time-integration scheme, you should something that looks like: <I PROPERTY="TimeIntegrationMethod" VALUE="DIRKOrder3" /> Unfortunately, I am not aware with the default order of the DIRK time-integration scheme. I hope this is helpful! Best wishes, Alexandra From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> On Behalf Of Andrew Barnes Sent: 27 January 2023 10:03 To: Nektar mail list <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Help with using DIRK Time Integration Methods This email from A.Barnes2@lboro.ac.uk <mailto: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://spam.ic.ac.uk/SpamConsole/Senders.aspx> 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