Whirlpool Direction

[orangehero]

Howdy,

I came across this post by MoreBeer on the ProBrewer forums:

Yes, Experiments with a Whirlpool Tank. By G. Van Gheluwe and M. Dadic Molson Breweries published in The Brewers Digest, September 1972

In the study, many factors were studied. Their research showed an increase in sedimentation of 6.2 % by running counter clockwise vs. clockwise.

MoreBeer

It's an interesting conclusion. Don't know if it really matters for homebrewers, but I'm still curious about what they did and how they measured. I've tried to find this paper but I am not having any luck. Does anyone happen to have a copy?

 

[Calichusetts]

This sounds ridiculous unless it has something to do with the equipment and where they are attached.

 

[SpeedYellow]

So in the southern hemisphere would they have to run the opposite direction to achieve that 6.2% gain?

 

[orangehero]

You're welcome to elaborate on why it sounds ridiculous. It could be due to Coriolis effect, but everything I've read says its influence should be miniscule at even commercial brewery scale. I've also read statements that Budweiser brewhouses have random placement of inlets. Then again maybe they just do it for convenience and use some other separation process where it doesn't matter.

I'm not sure why they found the sedimentation increase, that's the only explicit reference of the paper I've been able to find.

Here it's referenced but no mention of the rotation direction:
http://morebeer.com/brewingtechniques/library/backissues/issue1.4/barchet.html

 

[ajdelange]

In the northern hemisphere Coriolis is to the right i.e. the center for CW rotation but is tiny unless the velocity is great and the latitude high. So if they found CCW to produce better separation then the particles were moving against Coriolis. In any case Coriolis is a fictional force.


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[yogensha]

http://www.snopes.com/science/coriolis.asp

First google hit when you search for 'coriolis toilet'.

 

[orangehero]

In the northern hemisphere Coriolis is to the right i.e. the center for CW rotation but is tiny unless the velocity is great and the latitude high. So if they found CCW to produce better separation then the particles were moving against Coriolis. In any case Coriolis is a fictional force.


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Apparently it has been found to result in CCW rotation in the northern hemisphere.

 

[DSorenson]

How is Coriolis a frictional force? I always assumed it had to do with the angular velocity of the spinning globe... which would substantiate your claim that the effect increases as the experiment approaches higher latitudes. At the poles the motion of the flow of draining water is parallel to the motion of the spinning of the earth. It flows in the path of least resistance... meaning clockwise on the north pole, counterclockwise on the south pole.

 

[audger]

It's an interesting conclusion. Don't know if it really matters for homebrewers, but I'm still curious about what they did and how they measured.

I wasnt able to find it either, but the only force that would have an effect on direction of a whirlpool as described would be the Coriolis effect, as mentioned.

It has quite a noticable effect on the 1-2 gallons in my toilet, so I would imagine it would have a non-zero effect on similar fluids flowing in similar ways.

is <10% clarifying efficiency going to be noticed by a homebrewer? almost definately not. Should a brewery operator take this effect into account when designing a large brewery? its not a bad idea...

How is Coriolis a frictional force?

he said FICTIONal, not FRICTIONal....
in either case though, coriolis forces are neither FRICtional nor FICTional.

 

[DSorenson]

he said FICTIONal, not FRICTIONal....
in either case though, coriolis forces are neither FRICtional nor FICTional.

I got all these brains and yet I still can't read for comprehension...
:cross:

I assume you know what they mean by a fictional force, right? It's not that it doesn't exist. I think it's because it's due to a change in direction, causing a change in momentum. Think of the force on a fighter pilot pulling hard turns.

 

[Calichusetts]

The Coriolis affect is meaningless at the home brew level, no way it could increase trub settlement by 6%

This works on MASSIVE systems. Hurricanes, hundreds of miles wide, traveling for days. It doesn't even affect tornadoes. Even the slightest disturbance to water at the homebrew level would negate any aspect of this. Its is a function of length and velocity. You need to be moving large distances to see this. It affects missiles and not a baseball pitch.

People are reading way to much into an obscure 40-year old abstract.

 

[DSorenson]

Cali, you're 100% correct. I just got distracted by how little I had considered Coriolis. It didn't take much thinking to figure out that any deviation in that study is a bunch of bunk.

 

[ajdelange]

Apparently it has been found to result in CCW rotation in the northern hemisphere.

Yes, it does. Consider a mass of air at some distance from a low pressure center in the northern hemisphere. It accelerates towards that center and as soon as it acquires some velocity it is deflected to the right so it doesn't move along a radial line to towards the low but rather along a cyclonic (CCW) spiral.

 

[DSorenson]

Yes, it does. Consider a mass of air at some distance from a low pressure center in the northern hemisphere. It accelerates towards that center and as soon as it acquires some velocity it is deflected to the right so it doesn't move along a radial line to towards the low but rather along a cyclonic (CCW) spiral.

I wish I could type the face I am making, since I don't think I understand how this works. It would seem to me that since the northern hemisphere is rotating (relative to the north pole) counterclockwise. To me that means if I fired a bullet off the north pole, the bullet would begin to take a clockwise path, relative to the surface of the earth, since the bullet loses the force of the earth acting on it.

Perhaps you can enlighten me?

 

[govner1]

Howdy,



I came across this post by MoreBeer on the ProBrewer forums:







It's an interesting conclusion. Don't know if it really matters for homebrewers, but I'm still curious about what they did and how they measured. I've tried to find this paper but I am not having any luck. Does anyone happen to have a copy?

Check out Einsteins Tea Leaf Paradox. Explains why the trub migrates to the middle & bottom of the pot when you whirlpool instead of to the outside edge.


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[ajdelange]

How is Coriolis a frictional force?

By being non existent!

Now I'm being cute here but in fact there is no such force. It would be less confusing if it were called an 'apparent force' rather than a fictional force but engineers call it the latter. F = ma, where F and a are vectors, holds in inertial space but ECEF (Earth Centered, Earth Fixed) coordinates are not inertial coordinates. To get ECEF from innertial you must do two rotations, one about the z axis (by the longitude plus the rotation rate of the earth times time), and one about the new y axis (by the latitude). If you write these out and differentiate twice you find that the acceleration in the ECEF's contain terms which depend not only on the acceleration (and thus force) in inertial space but also on the velocity and position in inertial space. These latter are, respectively, the Coriolis and centrifugal forces. They aren't real forces. They are apparent forces.

I always assumed it had to do with the angular velocity of the spinning globe...

. It does. The first rotation matrix contains cos(&#937;*t) and sin(&#937;*t) terms. The first derivative of cos(&#937;*t) is -&#937;*sin(&#937;*t) which leads to the Coriolis forces and the second is -&#937;*&#937;*sin(&#937;*t) which leads to the centrifugal forces.

..which would substantiate your claim that the effect increases as the experiment approaches higher latitudes. At the poles the motion of the flow of draining water is parallel to the motion of the spinning of the earth. It flows in the path of least resistance... meaning clockwise on the north pole, counterclockwise on the south pole.

It's pretty easy to convince yourself that if you have a long range cannon at the north pole, point it at Dallas and fire you are likely to hit Fort Worth. It's not, perhaps, so easy to see that if you are at the equator directly south of New York and fire at it your shell will land somewhere in Connecticut and even harder, without the math, to convince yourself that a shell fires due west will be deflected north but all are true. In the northern hemisphere a moving particle is deflected perpendicular to its velocity vector. As explained in a previous post this results in cylconic (CCW) spiraling.

 

[Hoppity]

The Ekman Spiral is something I remember from an Oceanography course I took. The Coriolus effect makes the water cold in L.A. and warm in Cape Cod (relatively speaking). I was a big Jacques Cousteau fan as a kid.
I also liked Jethro Tull's "Aqualung" album.

 

[ajdelange]

It affects missiles and not a baseball pitch.

It effects, in a practical way, very much smaller systems. In the days before GPS aircraft used to navigate by measuring the altitudes of stars. As one could not see the horizon at night from an aircraft above the clouds the vertical reference was a small bubble in a liquid filled chamber - like the one in a level. The Coriolis force was enough to deflect the bubble far enough that appreciable error would be introduced into the quality of the fix if the navigator did not correct for Coriolis which he did by using a simple formula involving the velocity of the aircraft and the sin of the latitude. Deflection is to the right of the flight path in the northern hemisphere and to the left in the southern.

Now if it effects the bubble in a bubble sextant it will obviously effect the bubbles in your beer! The next time you order a beer on a flight provided the plane is making more than a couple hundred knots you will see a deflection perpendicular to the flight path (well, maybe you won't see it but it is there).

People are reading way to much into an obscure 40-year old abstract.

Well sure but engineers, being the weird sorts they are, get a kick out of chiding their colleagues for simulating non existent forces.

 

[DSorenson]

great... now I have to go take a cold shower for the math boner I have.

 

[Calichusetts]

It effects, in a practical way, very much smaller systems. In the days before GPS aircraft used to navigate by measuring the altitudes of stars. As one could not see the horizon at night from an aircraft above the clouds the vertical reference was a small bubble in a liquid filled chamber - like the one in a level. The Coriolis force was enough to deflect the bubble far enough that appreciable error would be introduced into the quality of the fix if the navigator did not correct for Coriolis which he did by using a simple formula involving the velocity of the aircraft and the sin of the latitude. Deflection is to the right of the flight path in the northern hemisphere and to the left in the southern.

Now if it effects the bubble in a bubble sextant it will obviously effect the bubbles in your beer! The next time you order a beer on a flight provided the plane is making more than a couple hundred knots you will see a deflection perpendicular to the flight path (well, maybe you won't see it but it is there).

Well sure but engineers, being the weird sorts they are, get a kick out of chiding their colleagues for simulating non existent forces.

Just to be clear, I bubble in a plane is NOT a small system. Again, distance and time are a huge part of this, a plane travels hundreds of miles, my whirlpool does not. Once again, a tornado is not affected by this effect compared to a hurricane traveling hundreds of miles more over days, not minutes.

If you brew on a plane and do a three day whirlpool, keep this thread in mine, otherwise, continue to argue engineers!

PS- While it has to do with the effect, Cape Cod is cold because we have a current of water running from the arctic to us. LA gets a current of equatorial water from Asia. Lucky sons-a....

And honestly...6% people, we are talking about 6% While I doubt its true, what would this even mean on a homebrew level?

 

[ajdelange]

Just to be clear, I bubble in a plane is NOT a small system.

A glass is perhaps 30 cm high and 6 cm in dia. The bubbles a mm? That's a pretty small system to me.

Again, distance and time are a huge part of this

No. The two things that count are the angular velocity vector of the frame of reference (which anywhere on the surface of the earth is 7.3E-5*sin(lat) directed up and the speed of the particle (as long as the particle in moving in a horizontal plane which is perpendicular to the rotation vector irrespective of heading). What matters is that the frame of the observer is rotating. That's all.

, a plane travels hundreds of miles, my whirlpool does not.

True but irrelevant. If you have a 20 m shot tower at the equator the shot will land about 2 mm to the east of the point from which they are dropped. Not a huge effect but measurable. The shot only travels 20 m.

Another example of the observability of Coriolis on a small (larger than a beer glass though) scale is the Foucault pendulum. The plane of swing rotates 15 degrees per hour in a clockwise direction in the northern hemisphere.

Once again, a tornado is not affected by this effect compared to a hurricane traveling hundreds of miles more over days, not minutes.

I think the point you are trying to make is that the Coriolis acceleration is small compared to, for example, g. In a car traveling 100 kmph at 45°N the force is only 0.0003 g. Small but measurable as it is enough to deflect the apparent direction of down by 1 minute of arc (and throw off a celestial navigator by 1 nm if not corrected).

If you brew on a plane and do a three day whirlpool, keep this thread in mine, otherwise, continue to argue engineers!

The only argumentative soul in this thread appears to be you. The rest recognized from the very beginning that Coriolis, as a practical matter, has nothing to do with brewing (well except perhaps if Coriolis flow meters are used in a commercial brewery).

 

[Calichusetts]

A glass is perhaps 30 cm high and 6 cm in dia. The bubbles a mm? That's a pretty small system to me.

No. The two things that count are the angular velocity vector of the frame of reference (which anywhere on the surface of the earth is 7.3E-5*sin(lat) directed up and the speed of the particle (as long as the particle in moving in a horizontal plane which is perpendicular to the rotation vector irrespective of heading). What matters is that the frame of the observer is rotating. That's all.

True but irrelevant. If you have a 20 m shot tower at the equator the shot will land about 2 mm to the east of the point from which they are dropped. Not a huge effect but measurable. The shot only travels 20 m.

Another example of the observability of Coriolis on a small (larger than a beer glass though) scale is the Foucault pendulum. The plane of swing rotates 15 degrees per hour in a clockwise direction in the northern hemisphere.

I think the point you are trying to make is that the Coriolis acceleration is small compared to, for example, g. In a car traveling 100 kmph at 45°N the force is only 0.0003 g. Small but measurable as it is enough to deflect the apparent direction of down by 1 minute of arc (and throw off a celestial navigator by 60 nm if not corrected).


The only argumentative soul in this thread appears to be you. The rest recognized from the very beginning that Coriolis, as a practical matter, has nothing to do with brewing (well except perhaps if Coriolis flow meters are used in a commercial brewery).

I am referring to the Rossby number used to explain these as they actually appear in geophysics. In other words, its not just a tiny bubble, its actually about the distance the plan travels, its how far the missle travels, etc. I am probably wrong, or maybe misunderstanding. My last class in the physics of the environment was like 2002. Great course, but probably rusty.

How about this...which direction does everyone stir in and will anyone change it after this thread? I can't even recall, but I think I actually do go counter-clockwise

 

[ajdelange]

I am referring to the Rossby number used to explain these as they actually appear in geophysics. In other words, its not just a tiny bubble, its actually about the distance the plan travels, its how far the missle travels, etc. I am probably wrong, or maybe misunderstanding. My last class in the physics of the environment was like 2002. Great course, but probably rusty.

It's entirely appropriate to use Rossby number to assess whether the pilot of the aircraft has to compensate for Coriolis acceleration. He doesn't. It's too small compared to the accelerations caused by inertial forces acting on the plane (if he is making 700 kmph at 45 °N it's .0021g). His navigator (using a bubble sextant) does, however, have to compensate for it because he is not concerned with the inertial forces acting on the plane but rather the relative magnitude of the Coriolis acceleration and g. Even though that ratio is still small it is enough to throw off his star altitude measurements by a tenth of a degree (abeam).

It's also appropriate to use it to decide whether Coriolis will have an appreciable effect on the particles in a whirlpool. It won't and as I said earlier I don't think anyone here meant to suggest that it does.

Does it have an effect on beer though? Yes. Your bubbles in a glass of beer on an airplane don't go straight up. They go up along a path slightly misaligned with the vertical. This was pointed out to entertain rather than try to convince anyone that there would be a Coriolis effect in a brewery. The only place one relies on Coriolis in a brewery (AFAIK) is where a Coriolis flow meter has been installed and I don't have any of those in mine.

 

[Huff360]

Does it have an effect on beer though? Yes. Your bubbles in a glass of beer on an airplane don't go straight up. They go up along a path slightly misaligned with the vertical. This was pointed out to entertain rather than try to convince anyone that there would be a Coriolis effect in a brewery.

AJ,

Just curious, is this enough off vertical to be seen with the naked eye?

 

[ajdelange]

In No. 23 we calculated that in an aircraft making 700 km/h at 45 °N the Coriolis acceleration would be 0.0021 g. That means the vertical would be deflected by atan(0.0021/1) = 0.12 °. Your eye would have to be pretty good (or the glass pretty tall) to see it. It would be noticeable to the user of a bubble sextant though.