--> FOAM FATAL IO ERROR : keyword (psi*p) is undefined in dictionary "/afs/nada.kth.se/home/nada/marcok/PDC/sonicOodles/base/system/fvSolution::solvers"

file: /afs/nada.kth.se/home/nada/marcok/PDC/sonicOodles/base/system/fvSolution::solvers from line 27 to line 34.

Function: dictionary::lookupEntry(const word& keyword) const
in file: db/dictionary/dictionary.C at line: 144.

FOAM exiting

What does this mean? I do not have any div psi*p in my equations. Not at least that I'm avare of. What should I do?

It says that you are trying to solve an equation for the variable called (psi*p) and that in your case "base", in the solvers section of the system/fvSolution dictionary you did not define which solver to use.

To be more precise, the variable you are trying to solve for (rho, by the looks of things), has been created automatically (sounds dubious, you may have already lost the oldTime() and similar, depending on the precise nature of error you've made) rather than being named. I would suggest looking at sonicFoam in detail, especially at the bottom of the createFields.H

volScalarField rho
(
IOobject
(
"rho",
runTime.timeName(),
runTime
),
psi*p
);


See, this one is named!

Enjoy,

Hrv