Study of Milk Crown

Hiroshi Gunji (Department of Geophysics, Kyoto University, Japan)
Hideki Ishii (Graduate School of Frontier Sciences, University of Tokyo, Japan)
Aya Saito (Graduate School of Medicine, Kyoto University, Japan))
Satoshi Sakai (Graduate School of Human and Environmental Studies, Kyoto University, Japan)

If liquid drop collides with a thin fluid layer, crown-like structure (milk crown) will be formed. In such phenomenon, surface tension is dominant, and a time scale is very short. To catch a continuous image of such phenomena, expensive equipment, such as a high-speed camera, would be required. Therefore, systematic researches which change parameters, such as collision speed of liquid, were not done.

Then, we considered how to record with a cheap commercial digital video camera, conducted the systematic experiment by this method, and analyzed the obtained picture.

Consequently, we found that the diameter of a crown was proportional to the 1/4th power of the lapsed time after liquid drop collides. That of  the trace after a crown disappears was proportional to the 1/2nd power of the lapsed time. The domain where the diameter of a crown is proportional to the 1/2nd power of lapsed time has only been found in the trace after a crown disappeared. We think that the crown turns into the capillary wave during its collapse.

We found that the time that the crown grows up is longer than the crown falls down. Considering a simplified model concerning of mass change and surface tension of the crown upper part, we could reproduce the asymmetry.