Temporal discretisation in interFoam

sebonator · August 20, 2009, 16:24

Hi everyone,

I am writing my Bachelor-Thesis at the moment and need an information about the way time is integrated by the interFoam solver for the basics-chapter of my thesis.

I already spent a lot of time for searching the User- and Programmer-Guides, but all I found are the several possibilities to perform the time integration. What I want to know is: Which of the possibilities is really used by the interFoam solver?

The three possibilities are listed in the Programmer-Guide:
-Euler implicit
-Euler explicit and
-Crank-Nicholson

The only thing I found is the possibility to choose the time derivative in the fvSchemes dictionary, but I could not find a place to choose the way time integration is performed.

I think the answer is located within the PISO loop that is called by interFoam, but I searched every source I could think of and did not find the answer to my question.

Greetings Sebastian

ngj · August 21, 2009, 05:43

Hi Sebastian

For interFoam, the momentum equation is discretized in time using the schemes chosen in fvSchemes by either

default ....

or

ddt(rho,U) ....

With respect to the gamma-equation it is solved using explicit Euler if you use the standard interFoam. It can be recompiled to use input from fvSchemes, i.e. implicit time integration; threads can be found on the forum on this topic.

Best regards,

Niels

sebonator · August 21, 2009, 08:39

Thanks ngj!

This was exactly what I wanted to know!

Greets Sebastian

August 20, 2009, 16:24	Temporal discretisation in interFoam	#1
sebonator Member Sebastian Lang Join Date: Aug 2009 Posts: 47 Rep Power: 17	Hi everyone, I am writing my Bachelor-Thesis at the moment and need an information about the way time is integrated by the interFoam solver for the basics-chapter of my thesis. I already spent a lot of time for searching the User- and Programmer-Guides, but all I found are the several possibilities to perform the time integration. What I want to know is: Which of the possibilities is really used by the interFoam solver? The three possibilities are listed in the Programmer-Guide: -Euler implicit -Euler explicit and -Crank-Nicholson The only thing I found is the possibility to choose the time derivative in the fvSchemes dictionary, but I could not find a place to choose the way time integration is performed. I think the answer is located within the PISO loop that is called by interFoam, but I searched every source I could think of and did not find the answer to my question. Greetings Sebastian

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August 21, 2009, 05:43		#2
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,903 Rep Power: 37	Hi Sebastian For interFoam, the momentum equation is discretized in time using the schemes chosen in fvSchemes by either default .... or ddt(rho,U) .... With respect to the gamma-equation it is solved using explicit Euler if you use the standard interFoam. It can be recompiled to use input from fvSchemes, i.e. implicit time integration; threads can be found on the forum on this topic. Best regards, Niels

August 21, 2009, 08:39		#3
sebonator Member Sebastian Lang Join Date: Aug 2009 Posts: 47 Rep Power: 17	Thanks ngj! This was exactly what I wanted to know! Greets Sebastian