interfoam B.C help
 

hi friends
1. can some1 explain buoyantPressure for pressure condition in interfoam?

down
{
type buoyantPressure;
value uniform 0;
}

I read an explain(below) in openfoam 1.7 user guide but didn't understand it's mean.
" At all wall boundaries, the buoyantPressure boundary condition is applied to the pressure field, which calculates the normal gradient from the local density gradient"

2. can we use this b.c in openfoam 1.6 ?
3. what about total pressure?

up
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;