Hi Alex,

The solver type refers to how you approach solving the given equations. In the case of incompressible Navier-Stokes, there are different approaches. The most common is the velocity-correction scheme (VCS) and it's derivatives. However, there is also a coupled solver for the monolithic system.

The TimeIntegrationScheme refers to standard time-stepping schemes. This includes Runge-Kutta, backwards difference formula (BDF), Euler-forward/backward and more specific schemes such as the Implicit-Explicit (IMEX) schemes. You can find a number of examples in e.g. the ADRSolver tests.

Your specific combination VCS + IMEXOrder2 leads to a second-order accurate VCS. An alternative might be the first-order accurate scheme via IMEXOrder1.

Best wishes,
Henrik

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Von: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> im Auftrag von Alexander Schukmann <alexander.schukmann@protonmail.com>
Gesendet: Dienstag, 9. Juli 2024 16:33
An: nektar-users@imperial.ac.uk <nektar-users@imperial.ac.uk>
Betreff: [Nektar-users] Velocity Correction Scheme and Time Integration Methods

 

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Hello everyone,

would somebody be so kind to briefly explain to me what exactly the TimeIntegrationScheme flag does in the session file when there is also a solver type that needs to be set?

The Velocity Correction Scheme is a time integration algorithm in itself, so why exactly is setting TimeIntegrationScheme to e.g. IMEXOrder2 needed in addition to choosing VCS? 

All the best

Alex 

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