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Drop coalescence is sometimes partial, and repeated
This may be simulated numerically (on a computer)
More viscous liquids merge completely
Less viscous liquids support capillary waves. Those waves converge at the top of the drop, causing it to stretch, and allowing pinch off to occur.
If the reservoir has a different surface tension, more complicated things happen
This may also be simulated numerically, if it is not too vigorous
Same surface tension for the drop and the reservoir.
Slightly smaller surface tension for the drop (5%).
Very slightly smaller surface tension for the drop (3%)
Larger surface tension for the drop (50%)
Drops containing two miscible fluids flowing in a tube get mixed.
With equal surface tension, there is slow mixing.
With the upper fluid having larger surface tension, mixing is faster.
With the lower fluid having larger surface tension, mixing is faster and more complete.
Drops coalescing with a second drop of different surface tension also get mixed, and very quickly at that
Weak surface tension difference (4%)
Intermediate surface tension difference (24%)
Large surface tension difference (40%)
For more details, you may consult the papers listed
Last modified: Wed Dec 29 08:29:20 PST 2010