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Title: Fluids Toy - Colors in Motion, density differential driven flow in Hele-Shaw cells

Description: Colors in Motion (Trademark by Wesmister, Inc., Atlanta, GA)

Two Hele-Shaw cells back to back comprise this novelty toy; each has two immiscible liquids with different densities. The heavy liquids are dyed green and red, seen in the first photo, top row, which fill the bottom reservoirs. The lighter liquid in both cells is dyed yellow, which occupies the remaining portion of the toy (including the top reservoirs). A small amount of air is also present. There are small strips in zigzag formation that separate each reservoir from its cell. Small openings in the strips allow passage of liquids.

The second and third photos, top row, show what happens when the toy is turned one half a turn, the air bubbles rise quickly, forcing the heavy fluid to flow down. Then blobs of red and green liquids flow down as yellow liquid rises to replace them. The bottom row photos show the foam flow at the end of about one minute operation of the toy. They show foam dynamics: elongation, pinch-off, and coalesce. For more information on this toy and how it could be used in education, contact Said Shakerin at



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Contributed By: Said Shakerin

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