Introduction

	Region	Subregion	Boundary
Geometry type	Volume	Volume	Surface
Required	At least one	Base case: No Simulation case: No Design case: Yes	Yes
Part of	NA	One region	One region

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 aluminum 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 aluminum plate. If a design run for this heat sink is to be started, the different materials, the fluid type, the location of the inlet and outlet, the location of the heat sources, and the design region need to be indicated.

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.

Region

A region represents a closed volume within the geometry that consists of a single material, classified as either a solid or a fluid. Every case must contain at least one region. If a region is a solid, it can be made up of multiple disconnected bodies that share the same material. However, if the region is a fluid, it must be a single, continuous volume. Finally, if a case consists of multiple regions, they must all be physically connected to form one contiguous overall assembly.

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Geometry guidelines

When having multiple Regions, they need to be connected to interact. Gaps between regions have to be filled, otherwise they will be thermally insulated from each other.

Regions cannot overlap with each other.

The figures below share the example described in the introduction with: (1) an aluminum region of type solid, (2) a plastic region of type solid, (3) and a water region of type fluid.

The aluminum region of type solid. — The manifold region.

The plastic region of type solid. — The cover region.

The water region of type fluid. — The fluid region.

Subregion

Just like a region, a subregion must represent a closed geometric volume or consist of multiple closed volumes. The key distinction is that a subregion belongs to a parent region and must fall entirely within its boundaries. A subregion can be classified as one of two types: general or design.

A general subregion is used to apply special conditions to a specific area of a region. For example, if a localized volume within a region generates heat, the geometry of that specific volume must be defined as a general subregion.
A design subregion, on the other hand, indicates the allowable space for geometric optimization. For design cases, at least one design subregion is required.

The figure below shares the example described in the introduction with the design region falling entirely within the water region.

The design region which falls entirely within the water region — The design subregion.

Boundary

A boundary consists of a single surface or multiple disconnected surfaces. Every boundary must belong exclusively to the exterior shell of a single, specific region.

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Note
It is not necessary to explicitly define or upload surfaces intended to be adiabatic. The software automatically applies an adiabatic boundary condition to all unassigned boundaries.

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Geometry guidelines

Boundaries should only touch 1 region and not overlap with other boundaries. Thus, they cannot be defined on interfaces.

Inlets and outlets are preferably flat surfaces (2D surfaces).

The figures below share the example described in the introduction with 3 boundaries: (1) the heated surface, (2) the inlet boundary, and (3) the outlet boundary.