Video snapshot captures fluid flow changes

by Adele Kimber

Fluid flow prediction is more powerful with video technique development

Design engineers using computer techniques to predict fluid flows can be faced with complex models and an infinite number of ways to analyse and view the results.

But engineers working at motor industry research body MIRA have devised a method of visualising how flow patterns change over time. They have developed a system which allows engineers to watch a three dimensional moving image of the flow and alter the angle of view.

The system uses computational fluid dynamic (CFD) techniques, now established as a key method of fluid flow prediction to assess external or internal flow behaviour of gases and liquids.

The flow can be watched as an animated image, using a package based on Ensight software running on a Silicon Graphics workstation.

Traditionally design engineers using CFD will take a freeze frame of the flow pattern to illustrate, for example, temperatures on a surface but will not get a view of how this changes with time.

`For instance it is much easier to spot a vortex in particle flow, which could suggest an area of wear, or to spot areas where heat is not well transferred. We can see changes which cannot be seen with traditional CFD snapshots,’ said Swapan Mallick, MIRA research engineer. `It means complex flows in complex geometries such as an exhaust manifold can be more easily understood.’

MIRA plans to offer the video technique as an extra to its CFD capabilities and has several proposals with car manufacturers.

Its engineers developed the technique during work with Daf Trucks on simulating air flow inside the engine compartment of a commercial vehicle. The research aimed to develop simulation and measurement techniques so that CFD could be used confidently to predict the performance of a new cooling system at a very early design stage.

`CFD now provides a powerful numerical technique for simulating three-dimensional air flow phenomena. Increased computer power and advances in mesh generation software permit CFD to be applied realistically to very complex geometries such as engine compartments,’ said Dr Anthony Baxendale, head of fluid dynamics engineering and research at MIRA.