[uli]

hi all

going through the tutorial http://openfoamwiki.net/index.php/Ho...ure_to_icoFoam

I did not completely understand the implementation of the energy equation.

            fvm::ddt(T)
             + fvm::div(phi, T)
             - fvm::laplacian(DT, T)

with phi = rho*U is equal to



whereas the energy equation is:



for a 2D flow not considerung the pressure terms, the dissipation function and with DT = thermal diffusivity = lambda/(rho * c_p)

Where is my mistake?

thank you
Uli

[wyldckat]

Greetings Uli,

I'm unable to answer your question, but I can make the following affirmation: that tutorial is basically an "how to copy-paste-modify code from scalarTransportFoam into icoFoam".
Here's a step-by-step explanation about scalarTransportFoam: http://openfoamwiki.net/index.php/ScalarTransportFoam

Best regards,
Bruno

[uli]

hi Bruno, thanks for your response.

according to the ScalarTransportFoam the code is correct. Then in this case phi must be U and not rho * U.
I thought it's rho * U because here it is: http://www.openfoam.org/docs/user/fvSchemes.php (chapter 4.4.5)

Uli

[wyldckat]

Hi Uli,

Ah! Now I get it... this is so basic that even I can answer

• Incompressible solvers assume constant rho, therefore only present in the viscosity.
• Compressible solvers need "rho" as a field, therefore present in "rho * U".

Best regards,
Bruno