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Product category: Fluid, thermal, noise and vibration analysis software
News Release from: CD-adapco | Subject: Star-CD CFD software
Edited by the Engineeringtalk Editorial Team on 24 December 2001

CFD software attempts to understand
pasta

The University of Padova has been using Star-CD CFD software from The CD Adapco Group to help transform shapeless pasta dough into the spaghetti, penne and farfalle we know and love.

If there's one subject that's close to every Italian's heart, it's pasta Italians take pasta seriously

Very seriously.

As anyone who has ever tried to create authentic, home-made pasta - just like mama used to make - will appreciate, shaping perfect farfalle-like bows, which are actually edible, can pose more than a few problems.

Even experts, producing pasta on an industrial scale, have some serious planning to do before they can begin the process.

Pasta, in its pre-production state, is a non-Newtonian fluid.

This means that, while appearing to be a solid, it is actually a fluid.

To confuse matters further, although technically a fluid, it does not strictly conform to the rules traditionally associated with other liquids.

This non-conformist behaviour makes the understanding of non-Newtonian fluids a complex process, and the production of pasta a challenge for even the most experienced Italian chef.

So it seems only fitting that a new study to try to understand the behaviour of non-Newtonian fluids should be carried out by the pasta-loving Italians from the University of Padova.

The study has been commissioned in response to a genuine industrial need.

If the scientists at the fluid dynamics research group of Padova can gain a better understanding of modelling non-Newtonian flows and the laws that govern them, it will become possible to work out how to improve the industrial processes necessary for their manufacture.

Pasta was chosen as the ideal subject for the study because, during production, it conforms precisely to the laws of a non-Newtonian fluid.

In an industrial environment, pasta needs two very different machines to control its production.

The first is involved in the shaping stage and is used to mould the material in a controlled atmosphere to ensure the correct and permanent shape.

The second, consisting of a drawbench and extruder, releases the moulded pasta while maintaining the nourishing properties that keep the pasta edible and tasty.

This machine must also ensure that the pasta is correctly distributed between the outlets.

These outlets set the final shape of the pasta, be it spaghetti, linguine or penne.

At each of these stages controlled temperature and precision are a must.

If the conditions are even slightly less than perfect the results could be disastrous.

It is in the final stages of setting the shape that the high variability of the fluid's molecular properties becomes a vital factor between creating bows and twirls or tasteless, shapeless lumps.

The researchers at Padova realised that CFD could offer them the depth of analysis they needed to understand this complex environment.

It was also hoped that a better understanding of pasta would lead to a greater knowledge of all non-Newtonian fluids.

Assisted throughout by Italy's industry leader in industrial and manufacturing plants, Pavan S.p.A, the fluid department began its analysis.

Using specialised instrumentation, engineers measured the viscosity of pasta while still in its fluid form in order to see how it reacted to changes in both temperature and velocity.

The researchers chose Star-CD from The CD adapco Group for its proven record in providing high quality simulations of complex environments.

Even so, the first step was to test the software's capacity for accurately simulating the behaviour and flow of pasta to see how it reacted when subjected to a variety of constitutive equations.

The theory being that if it worked for pasta, it would work for other non-Newtonian fluids.

The variations of temperature and velocity were tried and tested using the software, before going ahead with simulations of the industrial machinery, including the moulders and extruders, currently in use for pasta production.

The CFD analysis and results obtained highlighted useful changes in the machinery, which would optimise the pressure drop and distribution.

It illustrated that a reduction in pressure would ultimately lead to a reduction in the energy consumption necessary, simply because of the high viscosity of the fluid.

After observing the combined effects of both the geometry and the viscosity of the fluid pasta using the CFD simulations, it was possible to make the necessary adaptations needed to achieve and easier production process and a higher quality product.

The Padovans can now enjoy perfect pasta but they have also illustrated the effectiveness of CFD analysis as a useful tool when designing new equipment in any industry where the performance depends largely on the flow field.

In the case of non-Newtonian fluids this study highlights potential for further research, not only in the production of pasta but in a wider range of applications from plastic or silicone production to examining blood circulation.

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