[Nicholas_Langbein]

Hello,

can someone explain me intuitively or mathematically what does this 2nd term in convection flux formulation mean
in interFOAM we have :
surfaceScalarField alphaPhi2
(
fvc::flux
(
phi,
alpha2,
alphaScheme
)
+ fvc::flux
(
-fvc::flux(phir, alpha1, alpharScheme),
alpha2,
alpharScheme
)
);

what does -fvc::flux(phir, alpha1, alpharScheme) mean or how is it different from -fvc::flux(-phir, alpha1, alpharScheme) in interMixingFoam please help

[sharonyue]

`-fvc::flux(-phir, alpha1, alpharScheme),` in this way, a upwind scheme equals a downwind scheme. In other way, we can say `-fvc::flux(-phir, alpha1, upwind) = fvc::flux(phir, alpha1, downwind)`

`-fvc::flux(phir, alpha1, alpharScheme)` and `-fvc::flux(-phir, alpha1, alpharScheme)` is different. But `-fvc::flux(phir, alpha1, alpharScheme)` and `fvc::flux(-phir, alpha1, alpharScheme)` is the same (if you dont care about the scheme)