[immortality]

I want to have second order rhoCentralFoam.
whats your opinion about this fvScheme has been used for rhoCentralFoam,is it first order or second order:

divSchemes
{
    default none;
    div(tauMC) Gauss linear;
    div(phi) Gauss upwind;
    div(phi,omega) Gauss upwind;
    div(phi,k) Gauss upwind;
    div(phi,gas) Gauss upwind;
}

I have changed it to this form:

divSchemes
{
    default none;
    div(tauMC) Gauss linear;
    div(phi) Gauss linearUpwindV;
    //div(phi,omega) Gauss upwind;
    //div(phi,k) Gauss upwind;
    div(phi,gas) Gauss linear;
}

does they have any effect on the accuracy of the solution,or accuracy of schemes are really hard-coded and can't be changed?
1)how can find out that schemes are hard-coded in the solver or not?
2)what tutorial is suitable for testing that does change in schemes has any effect or doesn't?