The Colorful Crashing Leaping Fountain
Larry Cunningham
This photo of a water display known as a ‘leaping fountain.' These fountains have a special laminar flow nozzle that creates the dynamic arched glass-like rods of water. In laminar flow the motion of the particles of fluid is very orderly with all particles moving in straight lines parallel to the pipe walls. The velocity of flow varies from zero at the walls of the nozzle to a maximum along the centerline of the nozzle to create the streaming smooth glass rod effect. The Reynolds flow number needs to be low for this effect, if the flow number is too high it has the opposite effect creating a turbulent flow. A turbulent flow is unpredictable and not smooth, like water flowing out a garden hose.
This picture also includes internal reflection by placing a laser light inside the nozzle that illuminates the laminar flow stream internally causing the water stream to glow like a fluorescent tube. Total internal reflection is the result of light passing from a more dense into a less dense medium such that the incident angle is too large for the light to refract into the next medium and it reflects back into the incident medium. In this case the light is being reflected towards the center of the water tube by the outer surface like a mirror which creates the colorful rods of water. This is especially present where the rods of water meet each other making the white water emit the light very clearly.