[Jingxue Wang]

I am a green hands of OpenFOAM. I read some cases using LES in the User guides of OpenFOAM. The definations of divSchemes are like followings:

divSchemes
{default none;
div(phi,U) Gauss LUST grad(U);
div(phi,k) Gauss limitedLinear 1;
div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

1.I am wondering phi is a Generic Variable? It should be u,v,w in the momentum equation. Where do programmers to define phi?
2.I also see some samples like: div(rhoPhi,U) Gauss LUST grad(U).
Including rho or not is both ok?
3.And why to define k in LES smagorinsky model?What is the meaning of k？
4. And what's the meaning of div((nuEff*dev2(T(grad(U))))) .

Thanks for your help.