[mfoster]

I have a student modeling a heat sink that can be thought of as a hollow sphere or cylinder. We would like to investigate the rate of heat loss via conduction through and natural convection from the sphere to the surrounding fluid (air) domain. He modeled the geometry in SolidWorks and exported it as an STL file, which he has imported into OpenFOAM via snappyHexMesh.

Due to the multiple regions to be simulated, he has been using chtMultiregionFOAM and wants to apply a heat power boundary condition to the interior wall of the hollow sphere. (The interior volume of the hollow sphere can be ignored or considered insulated since it is the heat source.) My student has looked into TopoSet for selecting a particular face/surface, but it’s not clear to us how to select the interior surface.

Is TopoSet the best way to approach this? Ultimately, we'd like to select various complex surfaces and apply BC's to them.

[Kummi]

Posting your schematic model will be helpful to guide in better way.
I'm assuming that the sphere volume is inside the fluid domain, if then ignoring the interior volume, won't it affect the flow dynamics ?
Thank you

[mfoster]

Attached is a schematic.

The entire interior of the sphere is essentially the heat source, so we would like to simplify it to just an applied heat power on the inner surface of the sphere. (Sorry, probably not helpful on my part to call it "hollow"!) The interior volume does not interact with the exterior air.

[Kummi]

Hi,
Got the clear picture of your model. Hope it may look something similar as I shown in the attachment.
Create 2 domain based on chtMultiRegionFoam (1 solid 1 fluid)
In order to apply heat source from the surface, check the reference tutorial in the fireFoam (oppositeBurningPanels) solver. There you can find heat source as burner, which was implemented using toposet,

actions
(
{
name fBurner;
type faceSet;
action new;
source boxToFace;
sourceInfo
{
box (-0.15 -0.001 -0.30) (0.15 0.001 0.30);
}
}
);

As per your problem, you can set the respective heat source patch at the solid domain.
Hope it helps.
Thank you

[mfoster]

Thank you for identifying the reference tutorial in the fireFoam solver!

It seems that boxToFace uses a very defined area to make a face out of. Since we'll be applying this to a more complex geometry (again, the hollow sphere was just a simplification), do you still recommend boxToFace or would you point to another TopoSet solver to better interact with an unusual, imported face?

[Kummi]

Creating circular inlet on a square face
topoSet Dictionary Problem
3D semisphere in openfoam
This should be helpful.
I haven't tried by myself either