K-H Instability

Creating a Sharp Boundary Layer

In this experiment, you have to be careful not to mix the salt and clear water when pouring them in. When pouring the water in, putting the water tank at an angle means that there is less surface area in contact than when you have it flat, making it harder for the two liquids to mix. Even if you get a little mixing taking place, when you return the tank to horizontal, the layers are stretched out in each direction, giving you a clear boundary layer. However, if you move the tank back to horizontal too quickly, you can inadvertently cause a K-H instability, so taking your time to return the tank to horizontal slowly is important.

 

Taking Clear Pictures

When taking photographs of transparent water tank, if you light the tank from the front, the light reflects off the surface of the tank, making for fuzzy pictures. However, if you don't directly light the tank at all, use only back lighting and take photographs using the light that penetrates through, even scratches etc. on the water tank no longer become a problem.