Tornados in Groningen
Wind speeds of 117-180 kilometres per hour, roof tiles flying, caravans and trailers blown over, cars blown off the road and even some sheds and garages destroyed... and that’s only a mild tornado.
Whirlwinds in the Netherlands
Thankfully, tornados like these occur only very rarely in the Netherlands. But you might be surprised to hear that small whirlwinds are a regular occurrence here. With some 35 whirlwinds and 100 waterspouts above the North and Wadden seas and Lake IJssel, the Netherlands is the European front runner. If you would like to see this natural phenomenon with your own eyes, the best place and time to see one is along the North Sea coast in late summer. If you want to know more about tornados or you’d like to stick your hand in one (without the rest of you being sucked in!), then the Science LinX exhibition is the place to be.
Mini tornados made by birds
Alongside the tornado machine in the Science LinX exhibition, tornados also regularly appear in several of the research programmes carried out at our Faculty. Sometimes in rather unexpected places... Not long ago, for example, our researchers at the Marine Biology department John Videler and Eize Stamhuis, together with their colleague David Povel from Leiden, discovered that swifts are so agile and supple in flight because they create mini tornados. They demonstrated this by building a model of a swift’s wing and placing it in a tank containing running water. The sharp edge of the wing caused vortexes in the running water. As water and air both display similar dynamic behaviour, it was easy to conclude what the situation must be under natural conditions in the air.
Two different flows
Tornados in water and air can be described using flow theory, the study of the movement of liquids and gases. An essential element in this theory is the difference between ‘laminar’ and ‘turbulent’. In laminar flows all the liquid or gas particles move in the same direction in an orderly fashion, while in turbulent flows the particles all criss-cross each other haphazardly. Although the particles in turbulent flows all move in the same direction ‘on average’, the impression they give is decidedly jumbled. You can discover both of these types of flows in our tornado machine. The pirouette made by the tornado can be caused by both laminar and turbulent flows. However, the extra kink in the tornado’s funnel is the effect of turbulent flows.
Research in Groningen
Flow theory is the principal research theme of Groningen’s Applied Mechanics and Numerical Mathematics research group. Under the leadership of Arthur Veldman, our mathematicians have been studying all manner of flows for many years now. They’re very grateful for the existence of the computer. By running extensive calculations and creating revealing visualizations they can answer questions such as: ‘What is the force of a wave breaking on a ship?’, ‘What does turbulence look like?’, ‘How stable is the Gulf Stream’ and ‘How does blood flow through our veins?’ Or another example: ‘How can we control sloshing satellites?’
That last question might need some explaining... The movements of a store of drinking water or liquid fuel can cause all kinds of problems in space. Sloshing liquids can make spaceships harder to control or send satellites off their course. That is why our scientists are collaborating with the Dutch National Aerospace Laboratory in the North-east Polder to discover how we can control all this sloshing around!
- Science: ‘Abstract research on swifts’
- Computational Mechanics and Numerical Mathematics research group
Special thanks to: Hüttinger Exhibition Engineering, Charlotte Vlek and Lenny Taelman. Please contact Science LinX if you should have been included in the acknowledgements.
|14 December 2020 2.03 p.m.