“When a vertical water jet strikes a circular horizontal impactor, the water is deflected into a horizontal sheet. At sufficiently high speeds, the flow results in a circular water sheet, whose radius is set by a balance between inertial and curvature forces. At lower speeds, the sheet sags significantly under the influence of gravity, and may close, giving rise to a water bell (Figure 1). We have conducted a series of experiments in order to investigate the influence of increasing fluid viscosity on fluid sheets and bells.”

SEE MORE FLUID POLYGONS AND POLYHEDRA PHOTOS HERE:
http://www-math.mit.edu/~bush/bells.html