Aeroplanes and Water Down the Drain

1 yes it is true

somebody living on the equator in Africa even found out that the direction is reversed if you move a pace or two over the line of the equator.

2 the difference may be caused by the direction of the wind on that day.

3 yes it is almost related due to standard air flow zones.

The effect has a name but it is stuck on the tip of my tongue.

1. Coriolis effect is what you are thinking of, however based on the information provided on Wikipedia I'm not sure it's actually true. The Coriolis force provides measurable effects over large distances and over long periods of time. So for toilets and sinks perhaps the way water enters and the configuration of the drain system has more of an influence.

2. In addition to wind speed and direction of flight from A to B, the actual flight path may differ.

1 The program showing the experiment was on TV (and those people are always trustworthy)

Actually the force is very weak and can be reversed very easily. But if you eliminate design effects the rotation will always be the same.

The experiment can be done in any symmetrical container, even a bath tub.

2 The altitude may also differ. Pilots are always aiming for jet streams.

1. The flow of water is based on the sinks design no where you are located on the earth

2. Wind speed and direction are to large factors which effect flight times. If everything was equal from A to B as B to A then the flight time would be the same. This in reality never happens.

1) No, it's not true.

2) Wind speed, or if you're really not paying attention, time zones. You're traveling with respect to the earth's surface, so movement of the earth is irrelevant.

3) since (1) is false, it follows that (3) is false.

Thanks, T-Rex,

As we know the earth is rotating from west to east ( via North) in the CW direction. If you see the earth from the top ( Northern hemisphere) it will look like moving in CW direction and the water to the drain follows the earth movement.

At the same time if you view this from bottom of the earth ( southern hemisphere) it will look like moving in CCW direction.

So in Northern hemisphere the water to drain moves in CW dierction and CCW in southern hemisphere, asssuming the drains are constructed without any slope.

I want someone to support my understanding.

2) As far as Aeroplanes,I thought there will be a drag when the plane moves from East to west ( in the opposite dirction of earth movement )in the Northern hemisphere), it takes more time than the otherway.

Vice versa in the Southern hemisphere

Any takers?

Airplanes fly along in a block of air. If that block of air is moving along (lets say 10 mph east) then you add the speed of the block of air to the planes speed if you are flying east, and subtract the block of air's speed if you are flying west. That is how you figure out your ground speed. Nothing fancy here, every student pilot learned this in ground school prior to soloing.

I'm surprised no one here has said: TRY IT! I have spent hours trying it, in both hemispheres. The result is: the way you pull the plug and the design of the sink/tub/etc. are much more significant than where you are located. The Coriolis effect is very real on fluids that travel large distances; over a few cm or inches it is insignificant.

See '17'...

1) No, it's not true.

I have to disagree, as I have stood one side of the equator and poured water into a bucket with a whole in the bottom and watched it swirl in one direction, taken 3 steps and watched it go the other, stood on the equator and watched it go strait - no swirl. The only explanation I have ever heard is Coriolis, so unless you have a real good idea, thats what I'm going for.

1. The Coriolis effect increases with distance from the equator so unless you have very big steps you experiment was effected by some other influence. Perhaps a very slight motion of water in the bucket, caused by your steps or the pouring of the water, that would have been obvious had you added a drop or two of dye and observed the mixing process.

I have another one for you,along the same lines as the water down the drain question. If you have a helium balloon floating in a bus or truck with all of the doors and windows closed, what direction will the balloon move when starting from a stop. or stopping from a steady speed. I know the answer,lets see how many of you know, and why does it do what it does.

Hilltopper,

I never thought about this, but I'll take a guess.

The balloon will tend to move slowly in the direction opposite the acceleration produced "g" force, and down. In other words, the faster you accelerated forward, the more the balloon would tend to move toward the front of the bus, and the floor. Likewise, the faster you decelerated, the more the balloon would tend to move toward the rear of the bus, and the floor. This effect is the result of the balloon floating in the air and therefore it would tend to move forward and back, in the direction of lower air pressure. The air being affected by the acceleration such that a slight pressure gradient will occur between the front and back of the bus, (and across the balloon itself) with the gradient depending on the direction of acceleration. It would also tend to move downward as its buoyancy would be reduced as it moved toward the lowered pressure. (The elastic membrane of the balloon prevents it from expanding as much as it would have, so the relative density in respect to the surrounding air increases, resulting in less buoyancy.)

Anyway, that's my guess.

Regards, Greg

One: an object in motion tends to stay in motion

two: when the bus brakes, the baloon is not breaking so it will head toward the windshield just like someone who runs into a wall without a seatbelt on.

three: when accelerating, the baloon will shift to the rear of the vehicle.

four: there will be some effect relating to the relative friction of the air on the balloon (more substantial than you might think due to the low mass of the balloon.

"One: an object in motion tends to stay in motion"

Well you've obviously heard of Isaac Newton!

But, is it really as simple as you make it out to be?

If the bus accelerates forward, the air will be pushed to the back and therefore there will be a pressure gradient from front to back where the pressure is greatest at the back.

Thus the bouancy of the ballon (less dense than air) would push the balloon towards the front where the air is least dense.

It will go to the inside of the curve and to the back of the car, being lighter that air the air will go to outside of the curve and to the frount of the car pushing the lighter than air balloon in the oppsite direction than you would guess.

So now it appears you have cause to believe fact and fiction both. So let's try to answer only the questions you asked.

1. Yes water drains one direction in souther hemisphere the opposite in nothern; due to the slower speed of rotation of earth poleware; moving objects appear to veer right in NH, left if SH. All this known as coriolus force if you want to look it up and ponder the explanations given and try to get your brain around it.

2. No relaton between trip time and coriolus force in the sense you're thinking. Trip elapse times (measured on the plane) are typically shorter west to east because prevailing global air circulation (i.e., tail wind--that's jet stream in the stratosphere) is west to east. However, W-E trips are lengthened because time zones revolve east to west--pass to a more eastward time zone, your trip time has suddenly increased by one hour by local clock time where you land.

NatNat: It is true that water going down a drain TENDS to turn in a CCW direction in the northern hemisphere and the reverse in the southern hemisphere because the earth is turning under it. The force is very weak though and may be easily overcome by design of the fixture. The same force in weather patterns, winds flowing toward the center of a low pressure area, causes the same effect, but it isn't so weak and, in the case of a hurricane or tornado, not so easily overcome. Prevailing winds or differences in flight path may account for flight time differences. DickL

Replying to your 2 question, wind speed and direction are factors which effect flight times. Flights from A to B versus B to A are never same.

The Coriolis force is indeed very weak in terms of toilets and tubs. I read a report where folks tried to verify whether this was a myth or not. They used a tub designed to have as little influence as possible on flow direction etc. They were able to get the tub to consistently drain in the "correct" direction due to the Coriolis force. However, they said that they had to wait at least a day (maybe it was several days) after filling the tube. Otherwise, the swirling of the water when filling the tub was greater influence than Coriolis force, even after many hours.

Tad

My wife tells me Albuquerque to Houston takes less time than the return trip because one is down hill.

Gosh I love her !

Thanks guys and gals ( I suspect any ) for a wonderful discussion, so I conclude like this

1. True, but the effects are min ,the phenomena is "corialis effect"

2. True, due to wind speed not due to earth's rotation

3. No. As ans to 1 and 2 are not related.

see you all in the next discussion.

Nata

Hi PlbMac

I have to disagree, as I have stood one side of the equator and poured water into a bucket with a whole in the bottom and watched it swirl in one direction, taken 3 steps and watched it go the other, stood on the equator and watched it go strait - no swirl. The only explanation I have ever heard is Coriolis, so unless you have a real good idea, thats what I'm going for.

I have played around with water going down a drain hole and there are many factors that can vary the direction that can completely overwhelm the coriolis effect. To start with how accurately was the position of the equator known, could it have been out by as little as ±0.000 01 %. If it was then you didn't actually cross from one hemisphere to the other.

Here are several hypothesis that could explain the reverse in direction.

· When you moved your buckets you imparted a certain amount of rotation to the water in the bucket you were pouring the water from. This rotation did not have sufficient delay to cease and thus effected the results.

· The coriolis effect at the equator is negligible and the rotation was just random and pure chance gave the results you saw.

· If the buckets were on a flat level surface then both buckets could not be level as the surface of the Earth is curved. This means that the bottom of the bucket being poured into can't be exactly level during both tests and this minor variation in the level of the base of the bucket caused the reverse in rotation.

· The bottom of the bucket was no perfectly uniform and a slight change in alignment of the two buckets cause the reverse in rotation.

All these factors would have only a miniscule effect but they are all strong enough to overcome the coriolis effect, particularly near the equator.

Before looking any further into your experiment do you recall the direction the water rotated in the southern and northern hemispheres and how many times did you repeat the experiment.

Hi NatNat,

Just when you thought everything was clear and you understood what is going on I am going to throw a spanner in the works and confuse the issue again.

1. True, but the effects are min ,the phenomena is "corialis effect"

I agree with this

2. True, due to wind speed not due to earth's rotation

Yes the primary reason for opposing flights having different durations is indeed the wind.

However the primary driving force behind the wind is actually the coriolis effect which in turn is directly related to the rotation of the Earth. So in a round about way the difference in flight times is indeed caused by the rotation of the Earth just not in the direct way you originally thought.

3. No. As ans to 1 and 2 are not related.

So yes 1 and 2 are related but only at undetectable level. For all intense and purposes they are unrelated but in a completely different way than one might initially think.

Has that confused the issue sufficiently?

Pls find the info I have cut and paste from Wikipedia under the caption" Coriolis effect".

Now can anyone explain planes and timings?

[edit] Draining bathtubs/toilets

A popular misconception is that the Coriolis effect determines the direction in which bathtubs or toilets drain, and that water always drains in one direction in the Northern Hemisphere, and in the other direction in the Southern Hemisphere. This myth has perhaps been perpetuated by the Simpsons episode "Bart Vs. Australia," in which protagonist Bart Simpson has a young Australian boy confirm that his toilet water in the Southern Hemisphere spins in the opposite direction from Bart's own in the Northern Hemisphere. The myth is also propagated by the plethora of websites claiming that this fallacy is true^[1]. Strangely, many of these sites claim that drain water spins clockwise north of the equator, and counterclockwise south of it, which is reversed from direction of spin that would result from the Coriolis force, if it were a determining factor.

In reality, the Coriolis effect is a few orders of magnitude smaller than various random influences on drain direction, such as the geometry of the sink, toilet, or tub, and the direction in which water was initially added to it. Most toilets flush in only one direction, because the toilet water flows into the bowl at an angle. If you shot water into the toilet basin from the opposite direction, the water would spin in the opposite direction^[2].

This is less of a puzzle once one remembers that the Earth rotates once per day but that a bathtub takes only minutes (and a toilet only seconds) to drain. When the water is being drawn towards the drain, the radius with which it is spinning around it decreases, so its rate of rotation increases from the low background level to a noticeable spin in order to conserve its angular momentum (the same effect as ice skaters bringing their arms in to cause them to spin faster).

I have often wondered why cyclonic winds swirl anti-clockwise in the northern hemisphere when viewed from space. The Coriolis effect should cause moving masses to deflect to the right in the northern hemisphere. So the rotation should be clockwise when viewed from above. The storm as a whole does tend to curve clockwise as it moves over the ocean. What causes the swirl to be counter-clock while the direction of travel is clockwise ? I hope some atmospheric physics expert can come in on this.

The problem most people have in comprehending the coriolis effect is that they are looking at what is happening to a single parcel of air rather than the effect on the system as a whole.

The diagram shows the effect on the winds for a low pressure cell in the northern hemisphere. The black lines show the direction that the air would try to move if the Earth were stationary.

Now the winds that are moving from the equator (shown in oranges) and have a northerly component to them will all be deflected towards the east. This is because the air near the equator is moving faster towards the east than the air at the centre of the low pressure cell.

The winds that are near the pole and that have a southerly component to them (shown in red) will be deflected to the west. This is because the air closer to the north pole is moving eastward slower than the air at the center of the low pressure cell.

The net effect of all these deflected winds is that the air in the low pressure cell will rotate in a counter clockwise direction (green arrow). In the southern hemisphere the process is reversed and the rotation is in the opposite direction.

The trick is to look at it from the point of view of the center of the low pressure cell and the effect that all the winds will have on the cell rather than the deflection of just one parcel of air.

Thank you very much for the clear explanation. I am a bit conceited in thinking that I have a fair grasp of mechanics and can ususlly figure out these things. But whenever I see a satellite picture of a cyclone (huricane) I have had this doubt. Never took the trouble to look it up. I had vaguely thought that perhaps vertical winds in such a storm had something to do with deflecting the wind into a counterclock swirl.

Thank you once again

Hi Yaπanthram,

I must admit tat it is something that I too found confusing at first. It wasn't till I studied meteorology for my pilots license that I got it sorted out in my head.

Ok. position by GPS - bucket had a cork in until the water had calmed, sorry, but I'm convinced!

I was going to come in with a whole lot about how GPS units aren't that accurate and other things that can be at play here but I had a better idea.

I always like to see physical results and pictures so how about we build a simple mechanism to test it that can easily be shipped around the world in the mail? We could then send it to 10 to 12 of the CR4 regulars in various locations and ask them to test how the water goes down the drain at there location. You would need to take several tests at each location with the system aligned in various directions over several days. When they have finished testing they can then mail it to the next person and post the results on CR4. At the end we could then correlate all the results and see if there is or isn't anything to it.

I have never seen an experiment like this and it could either prove prove or sink the story once and for all. I live in Australia so we have a least one southern hemisphere location and it could be a fun experiment.

What do you think, is it worth doing or do we just accept the Wiki information?

I'm all for trying it again, I can only say that I could not detect any 'cheating'. I do detect some scepticism! As you're in Oz, will you use Beer?

You never waste beer pouring it down the drain!

No no no no no no! YOU lay underneath to analyse the flow direction, and your assistant takes out the cork.

I lived near Adelaide for half my life and had over 20 wineries within a 15 minute drive of the front door. Perhaps a nice lightly wooded chardonnay or maybe a gutsy cabernet-sauvignon with a good 8 years of bottle age?

Funny thing about beer ...... it seems to find its way to the drain quite well anyway!

Regards, Greg

Beer will always flow in the same direction.

Yep, through the kidneys then straight to the urinal and down the drain.

MASU- Thats a good idea about testing the draining of water from different areas of the world. I would be willing to do that. I suppose a good machine shop could construct a vessel to proper specs. so the experiment would prove one way or another. Its going to take time and commitment from fellow CR4 readers to do this. We need to work out some guidelines for everyone to follow. James

Hi James,

I was thinking of something along the lines of a plastic funnel that had level measuring devices and a way to make sure that the axis was vertical mounted on some sort of light weight adjustable frame. The flow of water would be controlled by a solenoid valve that could be opened without disturbing the arrangement. It would also need a compass mounted on the frame so you can check the alignment of the system with relation to the Earth's axis.

The test procedure would entail filling the funnel arrangement with water and after leaving it for a suitable amount of time opening the valve and monitoring the water. The tests would need to be carried out several times with the apparatus aligned in several orientations.

I am in the middle of moving house from Adelaide to Sydney and my workshop is going to be in transit for some weeks so I can't do anything at the moment. I will have a play with some funnels though and see what we would need to get it to work.

If you have any thoughts on how to go about testing this they would be greatly appreciated and you can either post them here or via the CR4 email service.

Sorry I don't know how to get graphics posted... Perhaps the water could be fed from 6 or more plastic hoses leading from an upper container, where the solenoid would open flow into all of them simultaneously, and the hoses would all feed at equal spacings radially into the periphery of a very shallow funnel. Ideally the funnel would have something akin to a parabolic cross-section to ensure smooth flow.

This would provide a close approximation to your Coriolis graphic.

I'd be happy to participate, and could give values for both 32° and 39° latitude, as I travel frequently between Placerville, and San Diego, CA.

I have shop facilities, and given some time, could construct the apparatus...

Dick W

Hi Dick,

To post a graphic you need to use the graphics button (as shown on the left) on the CR4 editor toolbar. Clicking this will open a window that allows you to either browse your computer and select the image or enter the URL of the image you wish to insert. You can leave an image without alignment in which text will appear before and after the image or align it to the left or right. The image on this post is aligned to the left.

The image will appear at the beginning of you post and you can then drag it to wherever you want it to be within your post. You can also resize it by dragging the corners or edges.

Thanks Masu.

Unfortunately, I just searched around, and don't see any tool bar! Perhaps that's because I'm using a Mac and Safari instead of a PC and Explorer.

Dick

Unfortunately, I just searched around, and don't see any tool bar! Perhaps that's because I'm using a Mac and Safari instead of a PC and Explorer.

That's interesting. You are looking in the correct place? The tool bar I am referring to is directly above the text box that you use to enter the text and is part of the web page? Since it is on the web page I would have thought it should be there regardless of the system.

MASU-It sounds like we are getting a worldwide plan together! I see that good gentlemen in Placerville, CA (dkwarner) is interested also. He lives on the west coast of United States and I live on the east coast. I work around testing equipment for the road paving industry and I might be able to come up with something. Funnels, solenoid valves and a stand does not sound too complicated. does your idea include some measuring of the force of the water flowing down the funnel? James

Hi Dick, James, Yanthram and anybody else that is interested.

I was thinking of something like this as a test rig.

The main part of the device is the mounting plate with a suitable funnel attached to it with the axis of the funnel perpendicular the mounting plate. There are three small spirit levels on the plate that are used in conjunction with the adjustable legs to level the mounting plate. The legs are threaded as are the holes in the mounting plate and by turning the legs you can adjust the length and level the mounting plate. This could be done with 2 spirit levels but it's easier with three and considering the extra cost is minimal I thought 3 would be worth it.

I am not sure what sort of solenoid valve would be suitable as all of the ones I can think of don't let the fluid pass directly through. They all deflect the water in some way and this could effect the results. I think a ball valve would be the most suitable as when open they offer no impediment to the flow of water and would therefore have less chance of effecting the results.

The reason for the funnel is that it has a vertical as well as horizontal component to the flow of water. With the water that is rotating there may be a vertical force that may cause it to rotate as well as the horizontal coriolis effect. If there is a vertical component then we may want to test a couple of different shaped containers but I think the conically shaped container would have the greatest chance of having an effect.

What do you think, has anybody else got some ideas of how to build something to test it and settle this conundrum once and for all.

MASU-Thats about what I had in mind. We could forget the solenoid valve -as you stated it could alter the results. I will do some researching on suitable ball valve arrangement. I still would like to put some kind of electronic flow gauge on it to measure the force of the whirlpool going around inside the funnel. I would think that the closer you get to the equator, the whirlpool action would be reduced. What do you think? James

Hi James,

There are several possible things that I can think of that may impart rotation to a fluid.

First off there is the he coriolis effect has which described earlier so there is no need to discuss this further.

Secondly there is altitude. Objects that are further away from the center of the earth must be moving faster towards the east than objects directly below them.

Thirdly we have differential gravity. This is also controlled by altitude and the fact that the force of gravity is related to the inverse square law. An object at altitude will be subjected to a slightly lower force due to gravity than an object below it.

There could also be a horizontal component to gravity if you are for example on the coast. In this case the mass of the land compared to the mass of the sea will produce a slight deviation on gravity and cause gravity to act at a small angle off vertical.

Now all of these effects are incredibly small and I would be dubious about trying to add any instrumentation to measure the effect as by doing so you may either cancel it out or induce a rotation.

I agree on all points you brought up. Introduction of something to the flow might alter the flow. Its a possibility that some kind of optical device could be employed. I got some thinking to do on this! James

MASU- Its a possibility we wont get any whirlpool activity out of the funnel. The hole might not be big enough. I will do some experimenting with other container arrangements. James

I have just be playing with a funnel to see if there is any sort of rotation imparted on it. Interestingly I was unable to get it to start rotating by itself and it needed a deliberate effort on my part. Once a rotation is started however it quickly develops to a complete whirlpool.

So what can we learn from this. First off since the rotation quickly develops into a whirlpool then we can safely say that any damping factor in the rotation has little to no effect until the speed of rotation is fast enough that the friction and centripetal forces increase to a point that stability is achieved. I think we can also say that if there were any natural rotation there this instability would amplify this effect.

Since it takes a deliberate effort to get it going then the coriolis effect is having no appreciable effect on the water draining from a funnel. If it were it would be quickly increase as the deliberate rotation did till a whirlpool formed.

Anyway I am interested to see if others find the same and see what they think so please have a try and see what you can find out.

Hello Masu,

With regard to the apparatus for checking the Coriolis effect; a funnel seems to be too small. Why not a large vessal with a hole punched at the center of its bottom. We need to clean the rim of the hole to ensure that it does not cause any rotation of flow. A plug made of some stuff which disolves in water can initially close the apperture. This is to avoid any sort of valve which may cause an initial disturbance. As the plug disolves the flow will commence. I don't see the need for a compass. The bottom of the vessal needs to be held level to ensure the flow will be vertical. The direction of the vertical with respect to the earth's axis of spin can be obtained using a GPS rather than a compass.

I live at a point in South India just 8.5 degrees from the equator; but I will give it a try any way.

I can't imagine a soluble plug that would dissolve in such a way that the flow started uniformly on all sides. The way Masu has his valve at the bottom of a relatively long tube should pretty well isolate any effects of the valve. It would not be hard to connect a small gearmotor to a ball valve, so you would not disturb the apparatus while turning the valve. It might be good to add a small magnetic compass, and perhaps a way of attaching a camera.

Masu's design would more directly answer the 'down the drain' question. The idea I proposed is more of a test whether Coriolis or any other force causes spinning of water flowing down a drain over small scale distances. Dick

"...sink the story..."

Isn't the English language wonderful?

The coriolis effect and its influence upon the weather is much stronger on a large body such as the planet Jupiter, which presents an interesting opportunity to study the phenomenon visually because of the varied colours. Greatly scaled down, the effect is present on earth in the behaviour of High and Low pressure spots in the atmosphere. Air, though, is largely transparent.

In the northern hemisphere, the winds go around a Low anticlockwise as viewed by an observer in space. What happens in the southern?

In the northern hemisphere, the winds go around a Low anticlockwise as viewed by an observer in space. What happens in the southern?

Cyclonic depressions rotate in exactly the opposite direction or in other words clockwise round a low and counter clockwise around highs.

Regarding 2:

I flew from Portland Oregon USA to Vienna Austria. The flight time was 16 hours, but headed East, we traversed 9 time zones. Thus relative to local time, the flight took (16 + 9), 25 hours, or over a day.

Now coming west, flight time was the same (16 hours), but we traversed the same 9 time zones, and thus relative to local time it only took (16-9) or 7 hours.

In simpler terms, it is an 8 hour drive from Portland OR to Boise ID. Going east, we go from Pacific time to Mountain time, so the trip takes 9 hours. Conversely, coming back (Mountain time to Pacific time), it only takes 7 hours. Flight schedules reflect departure and arrival times as local time at both the departure location and destination location... thus the discrepency depending on direction.

Bill

Consider?

If a level floor of 1 km x 1km is created the side furthest away from the equator will move at a slightly slower speed. This will stay true when the size of the slab is reduced. (rigid warping slab)

"Create circle" The shortest distance between 2 distant places usually (always) follow a curved path. a S curve if the equator is crossed.

"Create circle" The shortest distance between 2 distant places usually (always) follow a curved path. a S curve if the equator is crossed.

The shortest distance between two points on a sphere is along a great circle which has a radius the same as the sphere. The curved part of a great circle is always in the vertical plane and has no horizontal component at all. It only appears as a curved or S shaped line on a map and this is caused by the translation of the curved surface of a sphere to a flat surface of a map.

I've just got back from a small break and caught up with all the posts, and I think I've had an epiphany! The Moon shot program is back on, so lets do it on the moon! Just enclose your original design in a pressurised container and take it to the Moons equator - given the slower rotation of the moon, the effect should be harder to detect, but hay! We have to spend the research budget somehow........

What does this post have to do with the original questions regarding water going down a drain and air travel time? Some people need to filter things through a warped vision of their own reality.

1.False

2.Wind speed

A plane leaving Newark Airport flying to the west coast will take just over 6 hours. The reverse trip in similar weather conditions will be approximately one hour less. This has nothing to do with the flight plan as some else said. It is the Jet Steam that always flows from west to east.

The Coriolis effect causes water to spin CW north of the equator and CCW below the equator. Directly on the equator, if the had toilets or sinks or tubs the water would fall into the drain. Sort of like an implosion. The rate of spin has to do with the volume of the liquid and the diameter of the orifice of the drain.

Personally, I would like to see water fall into the drain at the equator. It is one of these natural effects that any one of else will ever actually see, like the Aurora Borealis.

The important thing is that the effect is tiny, though present, in draining liquid containers. The above posts might indicate that the flow is more likely to be disturbed by the action of local air movement, pulling the plug out and drainage outlet shape, than the Coriolis effect. One would be fortunate to achieve a 100% consistency in recorded observations across a range of bathtubs in both hemispheres.

The planet Jupiter is a good place to observe the Coriolis effect, as its action upon the Jovian atmosphere is rendered in colour. http://www.the-planet-jupiter.com/pictures-jupiter/planet-picture.html

Galileo was doing the right sort of thing many centuries ago...

The original post was a two part question. The first part was on drains and liquids spinning down a drain. The second part was about east to west air travel taking longer than west to east travel over the same approximate route.

I did not interpret the post to have a connection.

Hi Harold, welcome to CR4,

The Coriolis effect causes water to spin CW north of the equator and CCW below the equator. Directly on the equator, if the had toilets or sinks or tubs the water would fall into the drain. Sort of like an implosion. The rate of spin has to do with the volume of the liquid and the diameter of the orifice of the drain.

The coriolis effect has way too little effect to cause water flowing down a drain to rotate. In any case if it were having an effect then water would go down the drain in the northern hemisphere in a counterclockwise direction and in the southern hemisphere in a clockwise direction. For details of why refer to my post #27.

Then what causes the spinning effect? I always believed it was the Earth's gravity.

Hi Harold,

Then what causes the spinning effect? I always believed it was the Earth's gravity.

There are a myriad of things that can cause a rotation but the most common are some sort of rotation from the filling process and an uneven drain that imparts a rotation to the fluid going through it.

When you fill a container it is very difficult to get the water flowing in absolutely symmetrical and this causes the fluid to rotate around the center of gravity. It can take several hours for this rotation to cease completely and when you drain the container this rotation is amplified by the draining process.

Something to keep in mind is that anything that is round more than likely was machined on a lathe somewhere along the line. A lathe rotates in one direction and while the finish might appear to be even at a microscopic level it will favour rotation of a fluid passing over it in the opposite direction to the one in which it was machined.

There are a host of other things as well but the two I have mentioned, small as they are, have considerably more effect than coriolis. To see the coriolis effect you need something the size and duration of whether patterns and the atmosphere. Time is important as the longer the motion persists the further the earth is going to rotate and the greater the coriolis effect.

What does this post have to do with the original questions regarding water going down a drain and air travel time?

Threads meandering off topic is pretty is a pretty common event here at CR4. You will often see a thread change topic or branch off into to completely separate and unrelated discussions. It's just the way thins happen at CR4 and is probably associated with the way engineers think.

In this case, however, this thread has sort of merged with another thread that also ended up discussing the coriolis effect. Since actions and pictures speak louder than words I suggested that we build an apparatus to test the hypothesis and then ship it off to members across the globe to test it. Hopefully, the results will show, the earths rotation and ones location, had nothing to do with the way water rotates, as it drains and we can put this myth to rest once an for all. I believe this is a first for CR4 but it could be a lot of fun and set a precedent for future experiments.

Hi Harold,

Then what causes the spinning effect? I always believed it was the Earth's gravity.

What if the water is drained after the tank of vessel has been left to stand? Any mechanical effect from filling is then dissipated. (There are a myriad of things that can cause a rotation but the most common are some sort of rotation from the filling process) What about bathtubs? The drains are always at one end! ( and an uneven drain that imparts a rotation to the fluid going through it.) Or for that mater, liquid hoppers that have a slope, leading to the drain?

Appreciate the cause and effect logic. But this type of energy dissipates quite rapidly if the water or liquid is left alone. (When you fill a container it is very difficult to get the water flowing in absolutely symmetrical and this causes the fluid to rotate around the center of gravity. It can take several hours for this rotation to cease completely and when you drain the container this rotation is amplified by the draining process.)

What about chemical glassware? Almost devoid of any surface imperfection. For that matter, devoid of any porosity! No influence by the surface condition there! (Something to keep in mind is that anything that is round more than likely was machined on a lathe somewhere along the line.) What about sinkholes in nature? Very haphazardly formed, with out any relationship to anything really! (A lathe rotates in one direction and while the finish might appear to be even at a microscopic level it will favour rotation of a fluid passing over it in the opposite direction to the one in which it was machined.)

You are correct about the Coriolis effect. But the earths gravitational pull has a daily profound effect on everything from flying bodies to our wives breasts to my belly!(There are a host of other things as well but the two I have mentioned, small as they are, have considerably more effect than coriolis. To see the coriolis effect you need something the size and duration of whether patterns and the atmosphere. Time is important as the longer the motion persists the further the earth is going to rotate and the greater the coriolis effect.)

What does this post have to do with the original questions regarding water going down a drain and air travel time?

Did you see the last episode of ROME? Boy that Marc Anthony was a real.... (Threads meandering off topic is pretty is a pretty common event here at CR4. You will often see a thread change topic or branch off into to completely separate and unrelated discussions. It's just the way thins happen at CR4 and is probably associated with the way engineers think.)

Great idea! You start, and I will join you! (In this case, however, this thread has sort of merged with another thread that also ended up discussing the Coriolis effect. Since actions and pictures speak louder than words I suggested that we build an apparatus to test the hypothesis and then ship it off to members across the globe to test it. Hopefully, the results will show, the earths rotation and ones location, had nothing to do with the way water rotates, as it drains and we can put this myth to rest once an for all. I believe this is a first for CR4 but it could be a lot of fun and set a precedent for future experiments.`)

Hi Harold,

I have done some quick calculations of the sort of deflection that one can expect due to the earths rotation and it is controlled by three factors:

Distance From the Geographic Pole The coriolis effect is greatest at the north or south geographic pole and decreases as you get further from the pole reaching zero at the equator.

Distance the Fluid Flows The further the fluid flows the greater the deflection will be. This is analogous to the ice skater that is spinning on the spot and as they bring their arms in towards their chest the speed of rotation increases.

Duration of Flow The longer it takes the fluid to flow from the perimeter of the container to the center the greater the deflection will be.

Ok so what sort of deflection are we talking about? If you are at the pole the deflection you will see is about 4.36 mm per meter per minute or in SI units about 72 μm m^-1s^-1.

Ok I will leave it up to you to decide if you think that sort of deflection will make an effect.

Sorry cant comment on the last episode of ROME. This is most likely due to the fact that I live in Australia and as far as I know the series hasn't aired here yet.

I am going to start a new thread for the experiment under my An Engineer's Look at the Future of Energy blog but I have been completely swamped today. Its currently 02:30 Wednesday morning and I still havn't finished answering yesterdays thread responses let alone checking the daily news letter. Hopefully I will have time to get to it some time later today.

But the $64,000.00 question still is;

What causes the direction of flow of a liquid down a drain? CW? CCW? Neutral (at the equator)? Southern Hemisphere? Northern Hemisphere? As one who is not obsessed by the flow of toilet water as it takes away yesterdays porter house steak and baked potato, I am intrigued by the natural phenomena that causes this. My best information is the earths gravity and polarity do this. Polarity being what it is, is a negative versus positive force and it is at perfect balance at its epi-center (theoretical).

As I contemplate tonights grilled halibut and rice pilaf and spinach and Thursday's farewell removal. I await any post that answers the question and is not a tangential digression!

In the case of toilets, The construction of the toilet is never sufficiently precise to have water entering symmetrically at all parts, and many toilets have the main flow intentionally off center to induce swirling, thus helping to clean the sides of the bowl. Even if there were a 'perfect' bowl, the likelyhood of its being mounted perfectly level is pretty small; with one side slightly higher, you're right, gravity would tend to induce a vortex. Dick

Hi Harold,

Basically the rotation you see is caused by some sort of asymmetry in the drainage system or way the container is filled. Unless the water flows exactly along the radial lines, drawn from the center of the drain, it will impart some sort of rotation on the fluid as it moves towards the drain. The whole effect is cumulative and as the fluid gets closer to the hole the rotational speed increases. This is because its linear speed remains the same and as rotational speed, is defined as linear speed divided by radius, a decreasing radius means an increase in rotational speed.

Now its almost impossible for something to be exactly symmetrical so that the fluid only flows along the radials. Therefore, there will be some sort of rotation imparted. The bigger and larger the system the greater the rotation will be. For example, look at our solar system, every body within it is rotating and this is because as the initial cloud of gas, that condensed to form the Sun and planets, did not start of perfectly stationary and this all added up over time and distance to cause the rotation you see.

As you can see in my earlier post the sort of linear deflection we see due to coriolis is a maximum of 72 μm m^-1s^-1 so the time and diameter need to be fairly great in order to get any sort of rotation going due to coriolis.

Commercial schedules are often adjusted to include the gate to takeoff time and for congestion at the arriving airport, both of which can be excessive at some airports and during busy times of the day.

The actual flight time is affected by the wind speed and the routing which is not always the same on both legs.