SimScale CAE Forum

Enclosure failure on incompressible CFD

Hello, I am aware this question has been asked before and answered, but I am very new to SimScale and unable to follow the steps that the last person took to resolve this issue. My issue is that I am testing a very complex car assembly in CFD with surface models (which I know sometimes cause problems) and I cannot appropriately generate an enclosure or “background mesh” like what was suggested in a similar question. I am trying to simulate just the right half of the car with the smooth tires at the moment even though I know the car is asymmetric. It will provide sufficiently adequate results.
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Here’s an image of the error I am getting when generating an enclosure. Here is the link to the project.https://www.simscale.com/workbench/?pid=9058993943451789791&mi=spec%3A2c2928cb-9f6d-470a-855e-dbe4ee773c48%2Cservice%3ASIMULATION%2Cstrategy%3A18&ps=domain. Any tips would be greatly appreciated!

Hi!

You are correct - sheet parts can definitely cause issues (and require fixing in a CAD model before importing). On the other hand, the model also has one issue.

We can all agree that having a very complete and nice-looking model is awesome. From a production standpoint it may even be required. However, this is very much not optimal for CFD.

The reason is rather simple: whatever is in your geometry will have to be meshed. Small parts/unecessary details are a major problem here for three reasons:

  • Given their nature (small/detailed), they take a lot of additional cells to mesh. Very small/detailed parts require very small cells
  • If we don’t take care about these small cells, they may generate very poor mesh quality locally. E.g. very small cells adjacent to very large cells (a,k,a, large volume ratio). Not to mention non orthogonality/aspect ratio
  • And finally, most of these small parts don’t play a major role in the results. Think of an airfoil of an airplane. If you include or remove the rivets, this won’t really change the results that much (if at all). But the mesh size will be much different.

The CAD preparation page contains some useful information, especially in the “CAD preparation” section. It might be a good idea to look in the public projects section for similar geometries as the one that you have, so you can get a feeling for the desired level of complexity!

Cheers

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Thank you for the reply, I absolutely agree, this model is much too complex, and I have to work on simplifying it. I used this model because it is the official “full assembly” of the car put together by my team. I will work on simplifying it and stripping it down to large features. Thank you for your recommended sources, I will take a look at those.

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