The Toilet Swirl Phenomena
Being from the Caribbean, my teachers always made sure that the science concepts taught were always linked to our geographical location. That being said, when I was first introduced to the Coriolis effect, it was done by using a hurricane and the Virgin Island’s infamous trade winds as a model.
The Coriolis is a phenomena that causes fluids (air, water) to be deflected as they travel across the earth’s surface. The Coriolis effect is the reason why storms spin counterclockwise in the northern hemisphere and spin clockwise in the southern hemisphere. More interestingly, it explains why ship captains were able to use the trade winds (the greatest “driving force” of the 18th century) to travel across the ocean. This all sounds good to me, and I’ve accepted it, but how do I know that this is actually true? Does the Coriolis effect really exist?
It has been said that the Coriolis Effect determines what direction a toilet bowl will drain; counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The phenomena is so powerful, that its strength has even been tested on the Simpsons.
A recent youtube experiment (available below) disproved the Coriolis Effect on toilet swirl. Flushing numerous toilets within the same hemisphere showed that some swirl counterclockwise, while others swirl clockwise, leading to the revelation that the direction a toilet flushes is actually determined by a flow jet within the toilet. Sorry Simspons.
The experimenters then set out to prove that the Coriolis Effect exist by draining a perfectly still kiddy pool. The pools were filled opposite to how they were expected to swirl in their respective hemisphere. They are then left alone for 24 hours to eliminate the vorticity that would contribute to the direction of swirl.
Upon draining (without added disturbance to the water), it is evident that the pool in the northern hemisphere swirled in a counterclockwise direction and the pool in the southern hemisphere swirled in a clockwise direction, thus confirming the existence of the Coriolis Effect.
Image that a stationary pool was touching the edge of the south pole; although stationary relative to earth, the pool rotates with the earth. The side of pool furthest away from the pole moves fastest since it also has a larger rotation. The velocity distribution decreases from the outer-edge to the edge closest to the pool. The swirl is caused because the fluid from the outer-edge has a fastest velocity than that of the other edge; and similarly to a hurricane, as the pool drains, it swirls clockwise. For a hurricane, the higher pressure air rushes into the center of the storm and causes the air to flow clockwise. The Coriolis effect is real!
For more information on the Coriolis Effect or entertaining science, check out the links below and thanks for reading!
