Advanced analysis helps to capture speed record

A report on the increasing integration of CFD into the design process and the big part it played in gaining a world record

Although design teams have been making use of computational fluid dynamics to optimise designs, it has in the past been left to a specialist to carry out the analysis and interpret the results. However, the trend now seems to be that more generalist engineers are making use of the analysis as it becomes available within mainstream CAD and is more intuitive to use.

This approach is saving a lot of time both in the design of ordinary products, and in pushing the limits of what is possible. Although the analysis does perhaps not give as detailed results as those carried out by specialist packages, it does act as a compass for generalist engineers to follow.

And this approach has been particularly useful to the Bub Enterprise racing team which has recently set a new motorcycle land speed record of 367.382mph on the Bonneville Salt Flats in the US. The team exceeded the previous record by just 8mph, but owes much of this performance gain to superior aerodynamics analysis. The car was designed using SolidWorks with analysis carried out using SolidWorks Simulation, including the use of the Flow Simulation software.

Bub Enterprise chief executive Dennis Manning says: "The last thing we did before the run was to make an eighth of an inch change to the aerodynamics and that made all the difference."

The Flow Simulation software within SolidWorks is in fact written by what is now the Mentor Graphics Mechanical Analysis Division, formerly known as Flomerics. General Manager of Mentor, Dr Erich Bürgel, says: "It is not just available in SolidWorks, but also in Pro/Engineer and Catia V5, with NX and Autodesk Inventor implementations under construction."

Bub Enterprises also uses flow simulation software within SolidWorks called FloEFD to analyse its commercial exhaust systems. Dr Bürgel says the software is easy to apply to the design of a Fischer plastic ball valve, identifying recirculation caused by a sharp edge which would add a sharp pressure drop. The problem was eliminated with a fillet, which is something the design engineer would know to do. This is a typical example of how the approach can save time as it avoids having a model and design thrown back and forth between the design engineer and CFD specialist.

"It still includes some approximations," says Dr. Bürgel. "However the big movement forward is that, ten years ago it was really something for the specialist, whereas now it can be used by design engineers who are not specialists."

US based fluid handling firm Graco makes various design of a spray gun. Rick Anderson, a senior project engineer at the company, says it used FloEFD to optimise a product in one third the time that it would have taken to produce an acceptable design by trial and error.

He says: "The use of software prototypes made it possible to explore a much wider design space than would have been possible with physical prototypes. I was able to achieve these results despite the fact that I am a design engineer without any training in CFD."

Author
Tom Shelley

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