water down the plughole

For discussion of surf forecasting science and technology, wave science, weather and board mechanics or for any questions about the magicseaweed.com forecasts and software.

water down the plughole

Postby thedeadly » Fri Sep 10, 2004 3:05 pm

was going over some meteorology stuff i did when i learnt to fly years ago and it got me going on a "Grizzly" type train of thought !!!

Question about corriolis effect

water goes down a plughole in a spiral and depending what side of the equator you live on, the water will either go clockwise or anti clockwise - if you drove a rocket sled at the same speed as the earth is rotating on a straight track due west so the sled would stay in the same spot in space and you had a sink on it and some water would it just pour straight down the plughole or would it spiral - this would be done way into the northern or southern hemishere and not on the equator :?: :?: :?: :?: :?: :?:
Never buy a stupid dwarf - Its not big and its not clever
User avatar
thedeadly
 
Posts: 10765
Joined: Thu Jan 01, 1970 12:00 am
Location: ! No Signal !

Postby Hokusai » Fri Sep 10, 2004 3:19 pm

water goes down a plughole in a spiral and depending what side of the equator you live on, the water will either go clockwise or anti clockwise.

I thought that was just a fallacy.
User avatar
Hokusai
 
Posts: 849
Joined: Wed Sep 08, 2004 10:30 pm

Postby Grizzly » Fri Sep 10, 2004 3:30 pm

Hokusai wrote:water goes down a plughole in a spiral and depending what side of the equator you live on, the water will either go clockwise or anti clockwise.

I thought that was just a fallacy.


Correct. The spiralling motion arises from residual currents in the sink, not the corriolis effect. If your sink was about the size of the Irish sea, the coriolis effect would come into play, but at standard sink size, the effect is negligable.

But I like your train of thought :D :D :D
Gorau dial, dangos cwm a'i ffadau.
http://singlefin.blogspot.com
User avatar
Grizzly
 
Posts: 1941
Joined: Thu Jan 01, 1970 12:00 am
Location: Aberystwyth

Postby kevchenco » Fri Sep 10, 2004 3:36 pm

The Coriolis effect is to do with the earth travelling faster at the equator than at the poles. If you had a sled going straight west the parts closer to the equator would still be moving faster than the parts closest to the poles so the plug hole effect would still hold.
I think
It is a bloody good question though and has made the latter part of my afternoon more interesting thinking about it
kevchenco
 
Posts: 569
Joined: Thu Jan 01, 1970 12:00 am
Location: shizzol in the brizzol

Postby kevchenco » Fri Sep 10, 2004 3:42 pm

Oops maybe i was talking from my rear end then
kevchenco
 
Posts: 569
Joined: Thu Jan 01, 1970 12:00 am
Location: shizzol in the brizzol

Postby Hokusai » Fri Sep 10, 2004 3:48 pm

Coriolis effect is an inertial force described by the 19th-century French engineer-mathematician Gustave-Gaspard Coriolis in 1835. Coriolis showed that, if the ordinary Newtonian laws of motion of bodies are to be used in a rotating frame of reference, an inertial force--acting to the right of the direction of body motion for counterclockwise rotation of the reference frame or to the left for clockwise rotation--must be included in the equations of motion.

The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system. The object does not actually deviate from its path, but it appears to do so because of the motion of the coordinate system.

Ooooo, that takes me back. :lol:
User avatar
Hokusai
 
Posts: 849
Joined: Wed Sep 08, 2004 10:30 pm

Postby thedeadly » Fri Sep 10, 2004 7:55 pm

cool - right what i know of the coriolis effect is that a straight line wind from high to low pressure bends up into the circular lows and highs we all know of - couple of interesting things came up from the depth of my memory

1 - if you stand with your back to the wind then the low pressure is to your right - except thunderstorms

2 - if you fly a plane into a low pressure and dont change your altimeter settings as you go your height will over read progressivly eg you will be nearer the ground than you think - DANGER :!:

The spiralling motion arises from residual currents in the sink,


what do you mean by residual currents - nothing to do with electricity, sultanas stuck in the plughole, magnetic flux :?: :?: :?: ???
Never buy a stupid dwarf - Its not big and its not clever
User avatar
thedeadly
 
Posts: 10765
Joined: Thu Jan 01, 1970 12:00 am
Location: ! No Signal !

Postby Grizzly » Mon Sep 13, 2004 9:23 am

thedeadly wrote:
The spiralling motion arises from residual currents in the sink,


what do you mean by residual currents - nothing to do with electricity, sultanas stuck in the plughole, magnetic flux :?: :?: :?: ???


It's raisins mate....
Nah, just small movements and bits of turbulence in the water, left from pouring it in...
Gorau dial, dangos cwm a'i ffadau.
http://singlefin.blogspot.com
User avatar
Grizzly
 
Posts: 1941
Joined: Thu Jan 01, 1970 12:00 am
Location: Aberystwyth

Postby thedeadly » Mon Sep 13, 2004 4:31 pm

Nah, just small movements and bits of turbulence in the water, left from pouring it in...

that dont make sense - if that was true then the circular motion would be random clockwise or anticlockwise and in fact i have previously tried to make the water go the other way round and it just goes back to clockwise ????????
Never buy a stupid dwarf - Its not big and its not clever
User avatar
thedeadly
 
Posts: 10765
Joined: Thu Jan 01, 1970 12:00 am
Location: ! No Signal !

Postby soulsurfer » Tue Sep 14, 2004 10:51 pm

In pluholes tiny defects in the surface often mke it prefer to go in one vdirection rather than another. then there the residual vorticity and finally the coriolis
learn, create, test and tell Evolution rules!
User avatar
soulsurfer
 
Posts: 12
Joined: Mon Sep 13, 2004 11:19 am
Location: Tiverton and Woolacombe

Postby Hokusai » Wed Sep 15, 2004 7:44 am

Surely Vorticity wouldn't have any effect, unless the Plughole was the size of the UK?
Or are you just plugging a website? :lol:
User avatar
Hokusai
 
Posts: 849
Joined: Wed Sep 08, 2004 10:30 pm

Postby Grizzly » Wed Sep 15, 2004 8:55 am

It sure would... think conservation of angular momentumumumum
Gorau dial, dangos cwm a'i ffadau.
http://singlefin.blogspot.com
User avatar
Grizzly
 
Posts: 1941
Joined: Thu Jan 01, 1970 12:00 am
Location: Aberystwyth

Coriolis effect......

Postby EJay » Thu Oct 28, 2004 2:44 pm

Hey there,
Am new to this forum although not the site - look at it every day for the charts etc....
Am studying Geological Oceanography and was told the other day in a lec that the Coriolis effect acts at 45 degrees to the right in the Northern Hemisphere and left in the Southern Hemisphere and is negligable at the equator. As someone mentioned previously it is indeed to do with the varying speed at the poles in relation with the equator. The equator spins at approx 1000 m.p.h so if you fired a bomb from Africa to Scotland due to the Coriolis effect it would prob land somewhere more near Russia.......
Hope this helps and doesn't confuse matters more!
I reckon the water would go straight down the plughole by the equator - good excuse for a bit of research and a holiday!
User avatar
EJay
 
Posts: 122
Joined: Thu Jan 01, 1970 12:00 am
Location: Sunny Wales!

Postby Bigjohn » Thu Oct 28, 2004 6:15 pm

FACT: water rotation direction reverses as you cross the equator (see Michael Palin on "Pole to Pole"). It has nothing to do with residual currents, raisins or anything like that. Next time you have a bath, pull the plug, let the water start to spin, then make it spin the wrong way with your hand and it will stop and then go back the other way. Take the same bath south of the equator and the water WILL go round the other way.
I used to design water recirculation systems for fish farms and had to allow for this on outlet stand pipe design. Got caught out when a modular system was exported to South Africa, had to remake all the outlets and ship them out, BASTARD> :x
......Rubber Duck this is Pig Pen, I'm gonna put the hammer down..........

Image
Bigjohn
 
Posts: 4845
Joined: Thu Jan 01, 1970 12:00 am
Location: Anywhere except on a f*@king shortboard

coriolis and plugholes

Postby weathermanRN » Wed Aug 24, 2005 10:16 am

I know this thread is really old, but if anyone reads this i thought id shed some light on this arguement about whether or not water flows in different directions down plug holes in different hemispheres.....
1. Michael Palins example is flawed, he did it just either side of equator where coriolis force is almost non existent (the reason why tropical cyclones etc cannot form within 5 degrees of the equator - no spin to make them rotate) - to do with the sine of the angle (sin0 = 0 and sin90=1)
2. Already mentioned i think- Coriolis force is an EXCEPTIONALLY weak force and therefore only noticeable on things on a large scale, ie weather systems, Intercontinental Ballistic Missiles and Tides. As already said you would need a plug hole the size of the Irish sea to notice anything.
3. If the Coriolis force was that strong to affect your bath water then you would see it elsewhere......when trying to walk in a straight line, driving your car etc

Hope that clears it up
weathermanRN
 

Postby thedeadly » Wed Aug 24, 2005 11:01 am

they covered it on Brainiacs on sky - had people all round the world and phoned them up and asked them which way the water went - the result was totaly random
User avatar
thedeadly
 
Posts: 10765
Joined: Thu Jan 01, 1970 12:00 am
Location: ! No Signal !

Postby sponger_boy » Wed Aug 24, 2005 11:39 am

heeeeey i watched that, they do some cool stuff with household items.
hold her dash, or throw the three of us
User avatar
sponger_boy
 
Posts: 699
Joined: Thu Jun 02, 2005 11:00 am
Location: Kernow, east coast, no surf

Postby thedeadly » Wed Aug 24, 2005 1:04 pm

sponger_boy wrote:heeeeey i watched that, they do some cool stuff with household items.


and caravans :twisted:
User avatar
thedeadly
 
Posts: 10765
Joined: Thu Jan 01, 1970 12:00 am
Location: ! No Signal !

Postby Banana_man » Wed Aug 24, 2005 1:09 pm

The biggest point everybodys missed is that the taps are usually on different sides of the sink! Gravity will then make it run with the curve of the sink and that will determine the direction.
Cawabunga dude!
Banana_man
 
Posts: 1398
Joined: Wed Nov 03, 2004 10:54 am
Location: mars

Postby Noki » Sat Aug 12, 2006 8:27 pm

To early.
Noki
 


Return to Surf Science

Who is online

Users browsing this forum: No registered users and 2 guests