Pull request: Add functions into "ITHACAstream" to read the converged fields in parallel.

[Ruansh233]

1-Add two functions, read_last_fields and readLastFields, to the ITHACAstream. The two functions allow parallel reading of the converged fields in the subfolders.
2-The solver, 18simpleTurbNS, is also modified.
3-Declear as const for those immutable variables in the read_last_fields function.
4-Use pointers to improve the code's efficiency, following Dr. Mark Olesen's suggestions.
5-Add #if defined(OFVER) && (OFVER >= 2212)_ to activate emplace_back function for the new OF version.
6-Use Info instead of std::cout in the getTurbRBF function to reduce repeating print.

[olesenm]

This is really wasteful. There is no reason to read the field from disk and then make a full (deep) copy if it, which is what the clone() will do. At least wrap it as a pointer to allow the append to steal the contents. Eg,

auto tfld =
    autoPtr<GeometricField<Type, PatchField, GeoMesh>>::New
    (
        IOobject
        (
            field.name(),
            casename + runTime2.times()[last_s-1].name(),
            field.mesh(),
            IOobject::MUST_READ
        ),
        field.mesh()
    );

Lfield.append(std::move(tfld));

[olesenm]

Starting with OpenFOAM-v2212, you can also use the emplace_back() method. For example,

#if (OPENFOAM >= 2212)
Lfield.emplace_back
(
    IOobject
    (
        field.name(),
        casename + runTime2.times()[last_s-1].name(),
        field.mesh(),
        IOobject::MUST_READ
    ),
    field.mesh()
);
#else 
...
#endif

[Ruansh233]

Good morning, Dr. Olesen. Thanks for your contributive suggestions. I will modify the code and submit it later today. As a new guy in OpenFOAM, I still need to learn lots of such programming skills.

[olesenm]

No worries, you just need to be "paranoid" about clean code and memory use and most things will work out fine...

[olesenm]

consider passing as const fileName& casename

[Ruansh233]

Ok, I will modify it as const fileName& casename.