How to prepare your CAD

Introduction

ColdStream (as many other tools) requires its users to first upload a CAD file. For optimal use of ColdStream, we typically see a trend that a few additional CAD preparations are required. To introduce you to these, or to double-check that you have included them all, please reference the video below.
Most CAD files simply contain all the solid bodies. ColdStream will require a few additional entities to be uploaded.

Click here to download an example STEP file.

Fluid medium

ColdStream is not a CAD manipulation tool, it won't automatically create a negative of your solid bodies. Instead, the user should create a body that defines the fluid volume.

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Important

The fluid body defines where the fluid can flow, if it sticks outside of the solid region, ColdStream will simulate fluid flow outside of the solid region. Or vice versa, if there is a cavity between the fluid body and the solid housing, this cavity will be present during the simulation/optimization.

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Note

Pure conduction cases don't require a fluid volume to be created.

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Note

Pure flow cases don't require any solid regions, the shape of the fluid body defines where the fluid can flow.

Boundary conditions

Any boundary of a region that doesn't touch another region will automatically be assumed as an adiabatic wall. Any other type of boundary condition needs to be specified using a surface entity. The size and shape of this surface entity will determine where this boundary condition is applied.

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Important

Surface entities are needed to impose non-default boundary conditions.

Design region

ColdStreams will require you to define where it can create the optimized structures. For this, a new body needs to be created in your CAD tool. The volume of this body will determine where ColdStream can add the optimized structures.

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Important

The design region is the only entity where overlap is allowed with another region. The design region needs to be fully inside of its parent region.

CAD preparation rules

1. Bodies cannot overlap with each other (the only exception is the design subregion or general subregion).
2. A gap between two adjacent bodies will be (locally) thermally insulated from one another.
3. Surface patches are there to define boundary conditions:
   1. they must thus lie on the boundary of the entities on which you want to impose a boundary condition.
   2. they can only touch one region, and not be placed at the interface between 2 or more regions
4. Any CAD software can be used to prepare the CAD file
   1. The CAD file should be made in a parts file, not an assembly. An assembly file is a CAD file that refers to many individual parts files. The parts files contain all the individual entities making up the overall geometry.
   2. The CAD software should export the CAD geometry to STEP format using the 214 protocol.