[sachinjain]

Hi Everyone,

I'm trying to simulate a two phase flow using interFoam solver and I need to use explicit ddt scheme for the discretization of ddt equation for phase fraction. Is there any inbuilt scheme for that as all I could find were implicit schemes.
I'm using OpenFOAM version 3.0.1.

[satyam4841]

Can anyone answer this question, I trying to figure out same thing here.

[aow]

As far as I can tell, there are some implicit/explicit schemes, EulerDdtScheme, localEulerDdtScheme and SLTSDdtScheme, but I'm not entirely sure what that means as it is not explained in any detail (see this Time Schemes webpage). In general though, there seem to be two namespaces of derivative calculation functions in the source code, fvc and fvm, which are explicit and implicit schemes, respectively. For example, the time derivatives used to define the available ddt schemes in OpenFOAM are fvcDdt/fvcDDt and fvmDdt. Taking the EulerDdtScheme as an example, the source code uses both types of derivatives in different parts of the code and I couldn't tell at a glance whether you could control the use of one or the other.

Long story short, it seems like there aren't any obvious options for running a purely explicit simulation.

[satyam4841]

Thanks for the immediate reply Andrew. I found the answer in the user guide.
fvm::d(dT)-fvc::laplacian(DT,T)=0 -- solves explicitly
fvm::d(dT)-fvm::laplacian(DT,T)=0 -- solves implicitly.

[aow]

I'm glad you were able to find what you needed and it seems looking further into the fvc vs. fvm commands was the way to go. Are you trying to make a custom solver of some sort using commands like this?

[satyam4841]

Yes, i was trying to make a solver for simulating isotropic melt solidification process based on phasefield model proposed by R.Kobayashi 1993.

[aow]

Understood, that sounds intriguing. I didn't realize that at first and misunderstood your original query since I thought you were only looking at built-in ddt schemes. Good luck!