Originally Posted by dbxmcf

Hi, all:

I intended to specify a volScalarField p with boundaryField and internal Field specified by another function call instead of read from case file on hard drive, e.g. cavity/0/p, and in the creatFields.H for icoFoam.C I found the p was constructed using the following:
//-------------------------------------
volScalarField p
(
IOobject
(
"p",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);

I tried change the readoption IOobject::MUST_READ to IOobject::NO_READ, it compiles but then when the program runs I got:

--> FOAM FATAL IO ERROR : NO_READ specified for read-constructor

After searching the Doxygen and read the source file of GeometryField.C it seems that the createFields.H file of icoFoam.C used a constructor that will create a read-only volScalarField, I am not sure if there is some example to create such kind of volScalarField p that does not necessarily have to initiate from the disk file? I tried to use the IOobject::READ_IF_PRESENT, but the compiled program still tried to read from file and gave me an fatal error:

--> FOAM FATAL IO ERROR : cannot open file

file: /.../OpenFOAM/foamCases/run/cavity/p/0 at line 0.

Function: regIOobject::readStream(const word&)
in file: db/regIOobject/regIOobjectRead.C at line: 68.

FOAM exiting

I guess I need to use other constructor for class GeometricField but there are so many of them (totally 12 constructors) and it seems difficult for me to figure out how to use each of these? I searched the forum with the keyword "NO_READ", although this topic has been discussed for several times, I didn't find a satisfactory answer.

And kind of help is welcome!
Thanks a lot!