[b.simpson]

Hi all,

I have a natural ventilation model which comprises of a small simple room with a couple of heat sources inside and two sections on either side of the room acting as the external environment. I am using OpenFOAM v8 running buoyantSimpleFoam with RNG K-Epsilon.

When I visualize the U field in paraview, the air flows seem to be flowing from the top atmospheric boundary down to the ground on both sides of the building. My initial guess is that I need some sort of coefficient to control how the internal pressure matches the set external pressure. I know Phoenics has a control where you can add either a linear or quadratic coefficient to acheive this control. Unfortunately I do not now how, providing I need to, acheive this in OpenFOAM.

I have attached an image of the flows in paraview which hopefully shows the problem that I am trying to explain. I have also attached a compressed version of my model, if that is needed.

I have seen the use of a p0 value in some of the p files and not sure if I should be using this.

Hopefully someone will be able to help with this issue.

Kind regards.

Here is my p file:

FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 1e5;

boundaryField
{
    "xmin_South|xmin_North|xmax_South|xmax_North|ymin|ymax|zmin|Ceiling|Floor|East_Wall|North_Wall|South_Wall|West_Wall|Computer|Person|zmax_north|zmax_south|zmax_ceiling|North_Window|South_Window|xmin_Centre|xmax_Centre"
    {
        type            calculated;
		p0              $internalField;
        value           $internalField;
    }
	
	#includeEtc "caseDicts/setConstraintTypes"
}

// ************************************************************************* //

[b.simpson]

By any chance does anyone know how to fix this issue and achieve more realistic flows using the RNG K-e model?

[b.simpson]

Does anyone have any suggestions as to how to fix this model?

[Yann]

Hi,

First thing I would try: use 2nd order schemes in fvSchemes instead of 1st order (upwind)

For buoyant flows, using first order schemes can cause this kind of behavior.

I hope this helps,
Yann