hartvig.de » fluids http://hartvig.de Personal homepage of Kaare Hartvig Jensen Thu, 17 May 2012 13:22:03 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 The Horror : Cornstarch Fingers http://hartvig.de/2009/thehorro/ http://hartvig.de/2009/thehorro/#comments Tue, 24 Mar 2009 19:27:54 +0000 admin http://hartvig.de/?p=302 Continue reading →]]> I recently had the pleasure of meeting Robert Deegan from the University of Michigan. He has been involved in research that focuses on the dynamics of non-equilibrium systems for many years. Recently, he has become ‘famous’ among physicists for the discovery of the so-called “cornstarch fingers”. They can be observed when accelerating a non-newtonian liquid rapidly up and down by eg. placing it on a loudspeaker.

Deegan’s setup involves some pretty expensive hardware but this weekend, I decided to give it a try myself with a couple of friends: tjansson and haalle. Below is a photo of our setup, which consisted of a signal generator, an amplifier and a 8″ loudspeaker.



The first movie we recorded shows the effect of accelerating water rapidly up and down. You clearly see patterns, known as Faraday waves, forming on the fluid surface.


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The second movie we recorded shows the effect of accelerating a 70/30 mixture of cornstarch and water rapidly up and down. Above a critical acceleration rate, fingers starts to emerge that makes the experiment look more and more like a horror movie!


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Finally, check out our friend at MythBusters:

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