[sharonyue]

Hi guys,

I want to make a test about rising bubble via interFoam,Its really simple.But what confused me is my B.C. I wish the outlet boundary permit only water getting in and air getting out. so I set alpha B.C. like this:

boundaryField
{
    sides
    {
        type            zeroGradient;
    }
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 1;
        value           uniform 1;
    }
    frontAndBack
    {
        type            empty;
    }
}

To maintain stability,I use a combination of p_rgh and U B.C.

P_rgh

boundaryField
{
    sides
    {
        type            buoyantPressure;
	value		uniform 0;
    }
    inlet
    {
        type            buoyantPressure;
	value		uniform 0;
    }
    outlet
    {
 type            totalPressure;
        p0              uniform 0;
        U               U;
        phi             phi;
        rho             rho;
        psi             none;
        gamma           1;
        value           uniform 0;
    }
    frontAndBack            
    {
	type		empty;   
    }    
}

U

boundaryField
{
   sides
    {
      type            zeroGradient;
    }
    inlet
    {
	type		fixedValue;
	value		uniform (0 0 0);
    }
    outlet
    {
	type            pressureInletOutletVelocity;
        value           uniform (0 0 0);
    }
  frontAndBack           
    {
	type		empty;   
 }    
}

It runs normally, and the solution of alpha is not bad.but the p_rgh is little big.you can see the image.

So.if I want to simulate this situation which is only water can getting in,How should I set the B.C.?Thanks in advance.