February 21, 2011

Fountain, Wind, and Splash Pattern

The plaza in front of the Lawrence Hall of Science in Berkeley, Calif., features not only a model of a fin whale, which attracts clamberers of all ages, but also something more mundane—a fountain that simply  spouts water into the air. Nonetheless, on a windy day, the fountain can produce an intriguing splash pattern (below) that is well worth pondering.

Notice that a fairly smooth curve bounds the wet area to one side of the fountain. What factors determine the size and shape of this curve?

One key determinant is the wind—both its direction and speed. In this case, because the curve is relatively narrow and symmetrical, the wind isn’t changing direction very much, and the height of the curve suggests strong gusts.

Other factors also come into play, including the geometric shape of the fountain's water jets, the evenness of the plaza's surface, the fountain's octagonal edge, and so on. What might be causing the wings on either side of the main bulge?

It would be interesting to observe these splash patterns as they vary from day by day. What would they tell us about prevailing winds and the other factors that combine to create these wet spots?

Photos by I. Peterson

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