18 May 2011
Posted in WFTV Severe Weather Center 9
Have you ever wondered what a vortex is and how natural vortices including tornadoes, whirlpools and cyclones move the way they do? Try the tornado in a bottle experiment to find out. A vortex is a whirling mass of water, air or fire that creates a visible tornado-like column or spiral. A vortex can be created with the help of angular momentum, surface tension, centripetal force and fluid displacement. This experiment requires the use of super glue and a drill, so kids – don’t try this without an adult!
- Two 2 liter plastic soft drink bottles
- Food coloring (optional)
- Glitter (optional)
- Two bottle lids
- Super glue
- Electrical Tape
- Fill one bottle ¾ full with water.
- Add some food coloring and glitter. (Optional)
- Use the super glue (with a parent’s help) to glue the two bottle lids together, flat sides touching.
- Let dry.
- Drill a hole (with a parent’s help) through the center of both lids with a 9 mm drill bit.
- Screw in one side of the bottle lid to the bottle filled with water. Then, screw the empty bottle onto the other side of the connecting lids.
- Add some electrical tape around the connection to reinforce.
- Turn the bottles over and observe the movement of water from one bottle to the next.
- Try again, but this time give the bottle a few spirals as you set it down. Notice what happens this time.
The first time you turn the bottles over, the surface tension of the water tries to keep the water from flowing down. The weight of the water above it, however, forces the water to bubble up and break through into the second bottle. This is what makes the BLOOP BLOOP sound you hear as it happens several times. Each time this happens, pressure builds up in the bottom of the bottle until the air is forced up into the top bottle over and over until the top bottle is empty.
The second time, the water was directed into a spiral by your swirling motion creating a vortex into the bottom bottle. Gravity works to pull the spinning water down through the hole into the bottom bottle. The angular momentum of the spinning water makes the water at the center of the vortex spin faster than the water closer to the edge of the bottle creating a whirlpool effect.
The vortex created by the swirl lets the air pass through the center of the vortex without disrupting the flow of the water. When you combine this with the forces of water pressure and the gravity force, a centripetal force, or spinning force, makes the water swirl. Notice that the water near the bottom moves faster than the water at the top. The higher the speed, the steeper the curve needed to allow the spinning motion.