help for data output
 

Dear OpenFOAMers!

I am studying a tutorial about cavity flow, which is on Sec.2.1 in UserGuide.
Here, a standard k-epsilon model(kEpsilon) is used for turbulence.
I have a question about output. I would appreciate it if you can tell me
how to solve my question.

We can see (volume averaged) temporal derivative term 'ddt(epsilon_)'
in OpenFOAM/OpenFOAM-1.6/src/turbulenceModels/incompressible/RAS/kEpsilon/kEpsilon.C,

kEpsilon.C
---------------------------------------------------
223 // Dissipation equation
224 tmp<fvScalarMatrix> epsEqn
225 (
226 fvm::ddt(epsilon_)
227 + fvm::div(phi_, epsilon_)
228 - fvm::Sp(fvc::div(phi_), epsilon_)
229 - fvm::laplacian(DepsilonEff(), epsilon_)
230 ==
231 C1_*G*epsilon_/k_
232 - fvm::Sp(C2_*epsilon_/k_, epsilon_)
233 );
---------------------------------------------------

I would like to output ddt(epsilon_) (just as 'p' and 'U') at each time step,
but I am not sure how to modify the code.

As a trial, I modified kEpsilon.C as follows

---------------------------------------------------
volScalarField A = fvm::ddt(U);
volScalarField B = fvm::div(phi_, epsilon_);
volScalarField C = fvm::Sp(fvc::div(phi_), epsilon_);

tmp<fvScalarMatrix> epsEqn
(
A
+ B
- C
.
.
.
---------------------------------------------------

but I failed to output...How may I modify the code???
I would appreciate any solution you can come up with that would resolve the problem.
I am so sorry my English is very poor. Any assistance which you can give me would be gratefully received.

aki