Here are some videos of the “Turbulence in stratified and unstratified environments” demonstration. The full videos are linked to from the GIF titles.
I had not tried this before I made these videos and I do not think I got as sharp a stratification as is possible. That said, the demonstration still worked quite well.
Placing the upper layer of fresh water. The basic idea is that you pour the water into the boat and have it slowly overflow and spread out over the dense water below. I used salt rather than sugar, and it worked fine.
Adding the food coloring and getting the 2D flow. Again, I messed this up a bit and added too much dye with too much momentum. However, I did end up with a single vortex. The demonstration is quite forgiving.
3D demonstration. Here you just inject the dye into a jar of fresh water and watch the fine scale structures develop.
An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (firstname.lastname@example.org). I also welcome comments (through the comments section or via email) on improving the demonstrations.