Firstly, the geometry needs to be ‘CFD ready’
The solid volumes should be non-overlapping and should all be touching each other. More specific preparation details are explained here: Cad Preparation.
Basic recommended geometry checks:
This is a simple LED on a heatsink. It will be tested floating in the air and so will only have natural convection to lose heat.
Reference project here
Once the model is uploaded to SimScale, a fluid domain around the Heat sink should be created to analyse the flow characteristics. This can be done using the “Enclosure” operation under “Geometry Operations” as shown in the picture.
The video here shows how to perform the Fluid Volume extraction/ Enclosure using SimScale
The “Enclosure” option allows the user to set the dimensions of the Fluid volume. To complete this operation, we need to pick a “Seed Face”. A Seed face can be any face of the Heat sink. Picking just one face is enough for this purpose.
Please remember to switch on the “Keep existing parts” option, or the solid parts will not be retained.
The enclosure needs to be large enough to avoid artificially accelerating the air around the sides. These are the minimum dimensions:
Once the dimensions are defined, click “Start” to build the enclosure.
If the enclosure option is not used, the model would need to be ‘Imprinted’ so that all solid components are connected for conduction. This is also in the same menu.
Use the “Hex-Dominant (only-CFD)” mesh in this case. This is the most automated approach and is usually the best starting point.
Start with a ‘Coarse’ mesh. Finer can also be tested later
16 processors or fewer would be sufficient for the model shown.
Once when the mesh is complete, open the Meshing log and scroll down to the last few lines. If there is an error, it is likely that some interfaces are missing between materials. At this point, it might be sensible to reach out to support for assistance.
Ideally, all interfaces will be resolved, as shown here:
Here is a short video on how to assign Materials to different parts of the model.
In the “Initial conditions”, set the ambient temperature and pressure (101325 Pa)
For the general LED case, which is not sitting on the ground these boundary conditions are set:
Assign Volumetric Heat Loads
Advanced Concepts -> Power Sources -> Absolute power source.
Select each volume that will have a heat load and assign a power to it. If multiple volumes are selected, the same power will be applied to each.
It is advisable to set a “Result control” item, to monitor convergence during the simulation.
The default values should be suitable
Results for this sample case can be directly accessed here.
There is a short guide on using our online Post Processor here.