Module 5: Schlieren and Shadowgraph
  Videos
 

 

Here we see a KDP crystal hanging from a glass rod within a supersaturated solution of KDP in water. The excess KDP salt adjacent to the crystal deposits on the crystal surface and the salt concentration in the solution momentarily diminishes. Thus, the solution adjacent to the crystal becomes lighter than the rest of the solution and a buoyant plume is formed. The plume is further distorted by the crystal rotation.
The buoyant plume has been visualized here by a color schlieren technique. The yellow background arises from the yellow color of the rainbow filter initially picked up by the light beam, before the start of the experiment. The crystal rotation rate in this experiment is considerably higher than in the first video (with a blue background). Accordingly, the plume structure is symmetric with respect to the axis of the supporting rod. It can be expected that the symmetricity of the flow pattern will result in a symmetric salt deposition pattern over the crystal surface.