a break from the usual ordinaire

[kalen0matic]

why does water, when going down a drain, form a counter-clockwise flowing whirlpool?

hmmm. my insatiable curiosity is peaked.

Comments

[pianistamy]

I don't know, but if you swirl your finger around in the water clockwise, the whirlpool changes directions.

[kalen0matic]

well yes.

but the point is why does it naturally do so?

my dad has this hare-brained theory... but.

[pianistamy]

What's his theory?

[kalen0matic]

its effected by the mass in the center of the earth. gravity. could be pheasible...

[unpoedic]

I was about to impart the old theory that water drains in a counter-clockwise direction due to the rotation of the earth. Right? right? I'll hold that thought.There is no "single cause" for the formation of a vortex in a drain. It is due to "turbulent flow", which really only puts a name on it ... The "explanation" you probably heard in high school physics is that the rotation of the earth produces Coriolis forces[1] that make the vortex flow anti-clockwise in the northern hemisphere and clockwise in the Southern hemisphere. This is an error that has a life of its own, and just will not die. A quick calculation of the magnitude of the Coriolis effect[2] on the mass and time scale of the draining of a sink are way too small to account for vortex formation. The fact that a given sink always may flow in the same direction is most likely due to some asymmetry in the geometry of the sink and the drain.

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1. Coriolis force : an apparent force that as a result of the earth's rotation deflects moving objects (as projectiles or air currents)

[kalen0matic]

i don't think that asymmetry has much to do with it seeing as draining toilets and bathtubs turn in the same direction.

so... what next?