Introduction

Before uploading a CAD file to ColdStream, specific geometry preparations are required. Unlike standard manufacturing CAD files that only contain solid bodies, ColdStream requires additional explicit entities (such as fluid volumes and boundary surfaces) to accurately define the simulation environment.

The video below outlines these necessary preparations to ensure your geometry is properly configured for the platform.

Click here to download an example STEP file demonstrating proper CAD preparation.

Fluid medium

ColdStream is not a CAD manipulation tool; it does not automatically extract fluid volumes (negatives) from solid bodies. Users must explicitly model a separate 3D body representing the fluid volume.

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Important
The explicitly modeled fluid body strictly defines the fluid domain. If the fluid body protrudes beyond the solid enclosure, flow will be simulated outside the solid region. Conversely, any unintended gap between the fluid body and the solid housing will be treated as a physical cavity during the simulation.

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Note
Pure conduction cases do not require a fluid volume to be modeled.
Pure flow cases do not require solid regions; the fluid body alone defines the flow domain.

Boundary conditions

By default, any external boundary of a region that does not intersect another region is treated as an adiabatic wall (no heat transfer). To apply any other boundary condition (such as an inlet, outlet, or specific heat source), you must create a 2D surface entity. The exact size, shape, and position of this surface entity dictate where the boundary condition is applied.

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Important
Explicit 2D surface entities are strictly required to impose any non-default boundary conditions.

Design region

To utilize the generative design solver, you must create a dedicated 3D body defining the design region. The volume of this specific body establishes the maximum allowable space where ColdStream can generate optimized structures. When preparing this geometry, the design region must be fully enclosed within its parent region.

CAD preparation rules

To ensure successful uploads and simulations, strictly adhere to the following rules during CAD preparation:

No Overlapping Bodies: 3D bodies cannot physically overlap (with the sole exception of a design subregion, which must overlap/be enclosed within its parent region).
Perfect Mating: Any unintended gap or clearance between two adjacent bodies is treated as an adiabatic cavity, completely insulating the two bodies from one another in that specific local area.
Surface Patch Placement: Surface entities used for boundary conditions must lie perfectly flush on the exterior boundary of the target region. They cannot be placed at the internal interface between two or more regions.
File Format and Structure:
1. The CAD file must be exported as a single Part file (containing all individual bodies and surfaces), not an Assembly file (which merely references external part files).
2. Export the final geometry strictly to the STEP format (.stp or .step) using the STEP AP214 protocol.