Introduction

Every case setup begins with uploading the geometric CAD models. Typically, a case consists of multiple interacting entities. For example, consider a simple water-cooled heat sink: it includes an aluminum base (housing the cooling channels), a plastic top cover (sealing the heat sink), a fluid volume (water), and a heat-generating component applied to the aluminum surface. To configure a design run, you must define the materials, fluid type, inlet and outlet locations, heat source locations, and the allowable design region.

You can categorize and upload the parts of your geometry as one of three entity types: Region, Subregion, or Boundary. The table below summarizes their characteristics:

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

Region

A region represents a closed volume within the geometry consisting of a single material, classified as either a solid or a fluid. Every case must contain at least one region.

Solid Regions: Can consist of multiple disconnected bodies, provided they share the exact same material.
Fluid Regions: Must be modeled as a single, continuous geometric volume.
Assemblies: If a case contains multiple regions, they must all be physically connected to form one contiguous overall assembly.

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Geometry guidelines

Multiple regions must physically touch to interact thermally. Unintended gaps between regions will act as perfect thermal insulators (adiabatic cavities).

Regions cannot geometrically overlap with one another.

The figures below illustrate the heat sink example, highlighting an aluminum solid region and a water fluid region.

Subregion

Similar to a region, a subregion must represent a closed geometric volume (or multiple closed volumes). The key distinction is that a subregion is always assigned to a parent region and must fall entirely within its boundaries. Subregions are classified into two types:

General Subregion: Used to apply localized conditions within a region. For example, if only a specific internal volume of a solid generates heat, that localized volume must be defined as a general subregion.
Design Subregion: Defines the allowable space for the generative solver to optimize geometry. Design cases require at least one design subregion.

The figure below illustrates the design subregion falling entirely within the parent water (fluid) region.

Boundary

A boundary consists of a single 2D surface or multiple disconnected 2D surfaces. Every boundary must lie exclusively on the exterior shell of one specific region.

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

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Geometry guidelines

Boundaries must only touch one region and cannot overlap with other boundaries. They cannot be placed at the internal interface between two or more regions.

Inlets and outlets should ideally be flat (planar) 2D surfaces.

The figures below illustrate the heat sink example with three defined boundaries: the heated surface, the inlet, and the outlet.