Regions, subregions and boundaries

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Every case setup starts with uploading the geometry of your case. Usually, a case consists of multiple entities. As an example consider a simple water cooled heat sink. This heat sink consists of an aluminium base in which cooling channels should be placed and a plastic top plate to seal the heat sink. A heat generating component is applied at the surface of the aluminium plate. If you want to start a design run for this heat sink, you need to somehow indicate on the geometry the different materials, the fluid type, the location of the inlet and outlet, the location of the heat sources and last but not least the domain in which cooling channels are allowed to be placed. That’s where the concept of regions, subregions and boundaries come into play.

You can upload the parts of your geometry as one of the three entity types: (1) region, (2) subregion and (3) boundary. Each entity type is explained below.

A region represents the parts of the geometry which consist of one and the same material. It should always be a closed manifold or consist of multiple closed manifolds. A region can be one of the following two types: a fluid or a solid. If the region is a solid type, it does not have to be one lump but can consist of multiple lumps from the same material. If the region is a fluid type, it does need to be one lump. Every case needs to have at least one region. If a case consists of multiple regions, they should be connected in such a way that all regions together form one lump.

In the example described above three different regions can be distinguished: (1) an aluminium region of type solid, (2) a plastic region of type solid, (3) and a water region of type fluid.

Just like a region, a subregion should always be a closed manifold or consist of multiple closed manifolds. The only difference is that a subregion belongs to a region and must always fall entirely within that region. A subregion can be one of the following two types: general or design. A general subregion can be introduced to indicate special conditions in a particular part of a region. If for example a part of the volume of a region is generating heat, the geometry of that part should be uploaded as a subregion. A design subregion is used to indicate the design region. For design cases at least one design subregion is required.

In the example described in the introduction one subregion should be introduced: the design region which should fall entirely within the water region.

As the name implies, boundaries are used to apply boundary conditions. A boundary is represented by a surface which can be open but can be closed as well. A boundary can consist of multiple not connected surfaces. One boundary should always be part of the shell of one and only one region.

In the example described in the introduction three different boundaries can be distinguished: (1) the inlet boundary, (2) the outlet boundary, (3) the heated surface boundary to which the heat generating component is applied.