Hi, we just did the balance vortex here at Umass Dartmouth with a modification. Instead of having a cork, which is complicated to open later, we installed a valve that could be opened a little bit easier than the cork. However, the duct from the valve was narrow and the experiment ran slower than the regular "cork version". Here is the link for the video:
http://www.youtube.com/watch?v=MqX_UVhTVK8
Here are two selected frames. the blue indicates the surface trajectories and the red the bottom.
Frame 1 
Frame 2