What Is Concurrent CFD?

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Tags | analysis model, cad system, cfd simulation, cfd technology, FloTHERM, plm systems, Simulation, structural analysis software

Posted on 18 March 2010 by admin

Traditional CFD, upfront CFD and concurrent CFD are very different entities – but I want to point out that they represent the evolutionary spectrum of how the CFD technology itself has been packaged over the years.

Partly this change results from developments in other areas, like 3D CAD and PLM systems, and partly from improvements in the robustness and reliability of CFD to deliver useful solutions. Together these have allowed vendors the opportunity to package technologies together to deliver innovative products. Whereas they can be regarded as evolutionary in terms of how CFD technology is deployed. Concurrent CFD, upfront CFD and traditional CFD all have very different origins. Concurrent CFD can trace its origins back to the late 1990s and was inspired by the success of CAD-oriented structural analysis software such as COSMOS, Pro/Mechanica, etc., and by existing vertical easy-to-use CFD products for engineers, such as FloTHERM.

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. 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. 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 modeler within the analysis suite. 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 by 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 or CATIA V5 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.

Concurrent CFD therefore eliminates the “transfer geometry,” “create cavity” steps, and effectively meshes in one step. Meshing still takes place, but only takes minutes rather than hours of iterating back and forth. For example, one case I heard about recently took over a week using conventional CFD but only 10 minutes in FloEFD – a very happy customer!

CAD-embedded CFD, or concurrent CFD, is made possible by seven key technologies unique to FloEFD. These have been enhanced and refined over the years to the point where today we can truly claim that CFD analyses can be performed concurrently with design changes on the fly inside the CAD package. Today Concurrent CFD delivers the most fluent CFD process possible for product design.

Hopefully it should be clear that upfront CFD can never be faster than MCAD-embedded CFD which both removes time-consuming steps and allows 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 more a fluent CFD process.

The use of 3D modeling at the concept design stage reduces iteration loops and shrinks time to market. This is exactly where using concurrent CFD has the greatest impact, ensuring that the design’s flow and heat transfer performance are satisfactory before detailed production models are built and the design ‘solidifies’ making it much more expensive and time consuming to make significant design changes. I’ve recreated the slide below to show how FloEFD can be used concurrently with changes made to the CAD model right across the design process. Concurrent CFD is democratizing CFD for the mechanical design community, so now any mechanical designer can analyze the flow and heat transfer behavior of his or her design.

Source: Siemens PLM Community