Concurrent CFD Explained (Part I)

Happy New Year everyone. I hope it’s a prosperous and peaceful year for both you and your company.

As promised, here’s a Flash animation showing the difference between traditional CFD, upfront CFD and concurrent CFD which needs some introduction.

In traditional CFD, the model geometry is first exported from the CAD system. That’s the easy part. The geometry then needs to be re-imported into the CFD tool, meshed, solved, the results post-processed and then reported back to the design team. Next time I’ll talk about what this entails in more detail, but for now suffice to say this process typically takes 4 weeks or more. The work is usually done by a specialist analysis group, or outsourced so it’s necessary for the design team to explain what needs to be done. By the time the results are in the analysis model has become ‘stale’, as the design has moved on, often making it difficult to act on the results. Consequently companies often find little benefit in using conventional CFD before the detailed design stage is all but complete, with little opportunity to influence the design.

Upfront CFD attempts to improve this situation. Again I’ll go into more detail next time, but the main thrust of the approach is to streamline the interfacing from the CAD tool to the CFD tool. Usually this is done by incorporating a solid modeller within the analysis suite, which is the approach we took with FloTHERM well over a decade ago when we developed FloTHERM.MCADbridge based on the ACIS solid modeling kernel. The result is a much cleaner import of the geometry, but again the analysis work is done outside the CAD system, so it’s still takes time and having to go back and forth between the CAD and CFD software is messy. This remains the state-of-the-art in electronics, since the design effort is shared between the MCAD and ECAD systems, with the thermal design taking data from each.

Upfront CFD certainly helps bring the analysis in house. Being a separate tool it has a completely different user interface to the MCAD software that designers are familiar with, making it difficult for occasional users to become proficient. Hence the work may still need to be done an analyst rather than a member of the design team.

Concurrent CFD on the other hand works very differently. It’s MCAD-embedded CFD so the work is done within the MCAD environment. Embedding CFD inside an MCAD tool like Pro/ENGINEER Wildfire is hard to accomplish, but delivers very significant benefits. Design changes necessary to achieve the desired product performance are made directly on the CAD model, so the design is always up-to-date with the analysis. The familiar user interface means there’s very little the design team need to learn to become proficient.

Hopefully it should be clear that upfront CFD can never be faster than MCAD-embedded CFD which both removes time-consuming steps and allowing the design team to use their familiar MCAD user interface. We call this Concurrent CFD as it eliminates the need to go back and forth between the CAD and CFD tools means the CFD can be done concurrently with the design, leading to a more fluent CFD process – more on that next time. For now enjoy the animation!

Dr. J, Hampton Court

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Posted January 5th, 2010, by

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About John Parry’s Blog

A mixed bag of things that interest me professionally -CFD technology and its use in education, cooling technologies and the place of thermal design in the overall design flow. John Parry’s Blog

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[…] CFD is different to Traditional CFD approaches and Upfront CFD, take a look at these blog posts… Concurrent CFD Explained (Part I) Concurrent CFD Explained (Part II) Concurrent CFD Explained (Part III) Concurrent CFD Explained […]

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