CFD Online Discussion Forums - Numerical diffusion between TVD and NVD schemes

Hi all formers,

I recently calculated a compressible flow using rhoCentralFoam and I found quite difference between the results when using different interpolationSchemes in fvSchemes file.
The default interpolationSchemes for "reconstruct()" is VanLeer(V):

Code:

interpolationSchemes

{

    default                linear;

    reconstruct(rho)    vanLeer;

    reconstruct(U)      vanLeerV;

    reconstruct(T)      vanLeer;

}

I found the result is sort of over dissipation, but when I use Gamma

Code:

interpolationSchemes

{

    default                linear;

    reconstruct(rho)    Gamma    0.2;

    reconstruct(U)      GammaV  0.2;

    reconstruct(T)      Gamma    0.2;

}

the results are better. I don't know why they are different since they are all second order schemes. It means that VanLeer is more numerical diffusive?
Any suggestions?