[alberto]

Hello,
I have a question on the implementation of the eulerian model in bubbleFoam.

Why the alpha equation has been implemented as:

fvScalarMatrix alphaEqn
(
fvm::ddt(alpha)
+ fvm::div(phi, alpha, scheme)
+ fvm::div(-fvc::flux(-phir, beta, scheme), alpha, scheme)
);

and not as

fvScalarMatrix alphaEqn
(
fvm::ddt(alpha)
+ fvm::div(phia, alpha, scheme)
);

Best regards,
Alberto

[henry]

To maintain boundedness of alpha at the 1 limit as well as the 0 limit.

[alberto]

Thank you Henry.

Alberto

[sanglee]

Could anyone explain the defference between,
fvm::ddt(rho,e), and rho*fvm::ddt(e) ?

[henry]

Does rho vary with time?

[sanglee]

Yes, rho varies with time.

[henry]

In that case they are clearly different, the first is the rate of change of rho*e and the second is rho* the rate of change of e, wasn't that obvious?

[sanglee]

Yes, it is obvious.
Could you tell me the correct expression among the following ones;

fvm::ddt(rho,e)=( (rho)^^(n+1)*e^^(n+1) - (rho)^^n*e^^n )/dt or
fvm::ddt(rho,e)=( (rho)^^n*e^^(n+1) - (rho)^^n*e^^n )/dt

Or, if both are not correct, give me correct one please .
Thank you

[henry]

The first expression corresponds to an Euler-implicit discretisation of fvm::ddt(rho,e) and the second is clearly equivalent to an Euler-implicit discretisation of rho*fvm::ddt(e).

If you need to know these details you should look at the source code, it is all there ready and waiting for you, all you have to do is load it into an editor. The files you need to look at for implicit temporal discretisation are all in OpenFOAM-1.2/src/OpenFOAM/finiteVolume/ddtSchemes.

[sanglee]

Dr. Weller
I am trying to implement energy equation in bubbleFoam. I have problems with the disapprearing phases. As I reviewed your technical report, TR/HGW/02, Derivation...., I got an idea that your phase intensive momentum equation approach might help me. Could you give me some comments on using phase intensive energy equation instead of using the energy equation in conservative form.