Looking at the
        temperature of the fluid  | 
        
| 
     | 
    Different stable patterns can occur under the same conditions.  The pattern depends on the initial condition of the experiment.  | 
Experimental conditions
Outer temp.:22°C
Inner Temp.:15°C
Water depth: 73mm
Visible layer: 20mm below the surface of the waterPhotographic conditions
f=135mm, F8, 1/2sec, ASA400
Filming conditions
Speeded up 6 times
240x180: 15fps, 320x240; 30fps