hi, does anybody know why t
 

hi,

does anybody know why the flux in the icoFoam-case is calculated as it is?
there are lines like that:
volScalarField A=UEqn.A();
U=UEqn.H()/A;
phi=(fvc::interpolate(U+UphiCoeff*fvc::ddt0(U)/A,"interpolate((H(U)|A(U))")&mesh .Sf())-UphiCoeff*fvc::interpolate(1/A)*fvc::ddt0(phi);

where phi itself is "linearinterpolate(U)&mesh.Sf()"
i know that i need a div-term for the pressure-eqn but what are these other terms in the phi-calculation? for me it looks like adding something in the interpolation and than substracting the same after interpolation.
Am i right, that ddt0(U) gives the old-time-value for U in discretizised form (with coefficient)?
I hope somebody can explain what happens here.
thanks in advance
stephan