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:

 

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

 

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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