[jherb]

I would like to ask, why in some occasions in the following source file of a turbulence model the tmp<> mechanism is used and sometimes not:


https://github.com/OpenFOAM/OpenFOAM.../LienCubicKE.C


This is just an example, I would like to understand the concept. I have read the explanation at the wiki: https://openfoamwiki.net/index.php/OpenFOAM_guide/tmp


Here it is used, even though it is just a temporary variable in a method:

tmp<volScalarField> LienCubicKE::f2() const 
{     
    tmp<volScalarField> Rt = sqr(k_)/(nu()*epsilon_);      
    return scalar(1) - 0.3*exp(-sqr(Rt));  

}

and here it is not:

tmp<volScalarField> LienCubicKE::E(const volScalarField& f2) const 
{
    const volScalarField yStar(sqrt(k_)*y_/nu());
    const volScalarField le
    (
        kappa_*y_/(scalar(1) + (2*kappa_/(pow(Cmu_, 0.75))/(yStar + small)))
     );
 
    return
    (
        Ceps2_*pow(Cmu_, 0.75))
       *(f2*sqrt(k_)*epsilon_/le)*exp(-AE_*sqr(yStar)); 
 }

Does it matter? Is there a reason for it? Which rules should be followed?


Thank you very much for any help.