Irish Mathematicians Solve The Guinness Sinking Bubble Problem

I for one am glad to see that the great minds of our time are focusing on the important things....like a nice cold pint of Guinness ( For Strength !).  In my present location, such a thing of beauty is not available, but there will be plenty ready for me when I get some R&R.


Irish Mathematicians Solve The Guinness Sinking Bubble Problem -
Bubbles sink in Guinness because of the peculiar geometry of pint glasses, say a dedicated group of researchers at the University of Limerick


One of the more intriguing conundrums in fluid dynamics is the puzzling behaviour of bubbles in Guinness, the famous Irish stout.

As many drinkers will attest, the bubbles in Guinness appear to sink as the drink settles and the head forms. How can this be, given that bubbles are less dense than the surrounding fluid and so should rise?

Over the last ten years or so, physicists have begun to pick this problem apart. Most recently they've shown that it is not the bubbles that sink but the liquid, which circulates in a way that is downwards near the glass walls and upwards in the interior.  As long as the downward flow of the liquid is faster than the upward motion of the bubbles, they will appear to sink.

But that still leaves a puzzle: why does the liquid circulate in this way?

Today, a dedicated team of Irish mathematicians reveal the answer. Eugene Benilov, Cathal Cummins and William Lee at the University of Limerick say the final piece in this puzzle is the shape of the glass, which has a crucial influence over the circulatory patterns in the liquid.

To understand how, first remember that the motion of every bubble exerts a drag on the liquid around it. Now imagine what would happen if there were a region of liquid containing fewer bubbles near the wall of a pint glass and consequently a region of higher bubble density near the middle of the glass.

Benilov and co say that the drag will be higher in the region where the bubble density is higher, in other words near the centre of the glass. This creates an imbalance that sets up a circulation pattern in which the liquid flows upwards in the centre of the glass and downwards near the walls. 

That's exactly as observed in a pint of Guinness. But what causes the region of low bubble density near the glass walls in the first place?

Benilov and co imagine that to start with, the bubbles are distributed evenly throughout the liquid. In a perfect cylinder, they would simply rise together. The bubbles in each volume of liquid are steadily replenished from below. 

But imagine a container that is narrower at the bottom and wider at the top so that the walls rise at an angle, as in a pint glass. In this case, the simple act of bubbles rising creates a region of low bubble density next to the angled wall because the bubbles are not being steadily replenished below.

By contrast, the bubble density is higher in the middle of the glass because the bubbles are replenished from below.

That would set up exactly the circulation pattern that is observed, say Benilov and co.

This effect is well known in sedimentation theory as the Boycott e?ect. "It was ?rst observed in test tubes containing red blood cells when it was discovered that sedimentation times could be signi?cantly reduced by inclining the test tubes," say Benilov and co.

These guys have even created a computer model of bubble behaviour in Guinness which confirms their thinking.

The icing on the cake, however, is that there is a simple experiment that can easily confirm the theory.

Experiments are not usually the domain of mathematicians. But Benlivo and co demonstrate valour beyond the call of mathematical duty by actually performing the experiment in which they bravely pour Guinness into a cylinder. "If the container is tilted, bubbles will be observed to move upwards near its upper surface and downwards near its lower surface," they say.

They have even created a video of this experiment which you can download here (avi).

Of course, the essence of experimental science is repeatability. Many readers will not be content with mere visual evidence from a video but insist on repeating this experiment on their own terms, perhaps in a hostelry of their own choosing. Quite right.

But if you choose this route, remember that this work is not entirely whimsical. "Understanding these types of bubbly ?ows is important for a number of applications, such as manufacturing champagne glasses engraved with nucleation sites, and widget and similar technologies for promoting foaming in stouts," say Benilov and co.

Guinness drinkers (and servers) will also be aware of another problem that plagues them--the time it takes for a pint of Guinness to settle, which is significantly longer than with most ales and lagers.

Could this work allow pint glasses to be redesigned in a way that encourages stouts to settle more quickly?

We'll be following future developments closely.

Ref: arxiv.org/abs/1205.5233: Why Do Bubbles In Guinness Sink?
http://www.technologyreview.com/blog/arxiv/27880/?p1=blogs

Why Guinness tastes better on the Emerald Isle than anywhere else in the world

The reputation that Guinness has as the world's finest brew is well deserved...I for one, prefer it over all other forms of brew.....maybe I am a bit of a Guinness snob, but that is the way it is....you can drink your other brews but for a true enjoyable brew, you can't beat one that has been brewed in the same location since 1759....why that out dates the USA !!

So this info doesn't surprise me....I'll toast a few on St. Patty's day and I advise you to do the same...Enjoy !

Stout of Ireland: Why Guinness tastes better on the Emerald Isle than anywhere else in the world
By Daily Mail Reporter
7th March 2011

It's one of the most stoutly contested Irish boasts in bars the world over.
But scientists claim to have settled the score once and for all: Guinness tastes better in Ireland than anywhere else.

Experts from the Institute of Food Technologists carried out extensive taste surveys in 33 cities in 14 countries to find the best place for a pint of the black stuff.
And the majority of testers said they enjoyed a pint of plain in Ireland far more than in any other location.

The study, which claims to be the first to scientifically prove that the stout doesn't travel well, used 'non-expert' tasters, each from different countries, to conduct the test.

It took 103 in 71 different pubs where factors such as pub ambience, Guinness appearance, flavour, and aftertaste were all considered.

Using a Visual Analogue Scale which ranks enjoyment from 1-100, Guinness drinking in Ireland averaged a score of 74, compared to just 57 anywhere else.

Pete Brown is a celebrated beer author who toured the world searching out the local tipple for his book 'Three Sheets to the Wind'.

He said a Guinness in Ireland marks the end of a pilgrimage for beer lovers, and it is no surprise they enjoy it more there than anywhere else.

He said: 'Drinking Guinness in Ireland is always going to be more enjoyable than in London or Paris, or anywhere else.

'There is a feeling of authenticity that you associate with drinking a beer in it's true home, so the ambience you feel in an Irish pub would be like no other.

'People will go to Dublin with the intention of ordering a pint of the black stuff, so you're already gearing yourself up for that satisfaction before it's passed your lips.

Although, he says, the sensation of having a 'proper' Guinness will heighten the drinker's enjoyment, he said there are also practical reasons the local drink will always taste better.

He said: 'In Irish pubs you can order a Guinness knowing that the tap has been flowing all day, so you'll never get a pint which has been sat in the pipes for an hour. Whereas in London, it could have been there all day.

'The locals also tend to know their own beer inside out, so you'll get it at the right temperature, in the right glass and with the right head. That's really important

BRILLIANT !!! The ingenious beer-pouring device that could make " beer lines" a thing of the past....

BRILLIANT !!!


The ingenious beer-pouring device that could make Beer lines a thing of the past
26th December 2010

For anyone who has been to a music festival, a big gig - or even just a loaded bar full of thirsty punters, there's an invention that will make your life easier... and possibly a little bit drunker.

It should also light up the dollar-signed eyes of bar owners everywhere.
It's an invention that has literally come from the ground up, and uses common-sense technology to fill a plastic beer glass from the bottom.




The technology is relatively simple - a plastic cup with a hole in the bottom is coupled with a magnetic disk that seals the hole after the weight of the fluid is pumped in.

It not only regulates the flow of beer, claims the manufacturers, but does it faster than a regular pour, and apparently leaves a perfect head.

The Bottoms Up pouring machine is the brainchild of GrinOn industries, which has manufactured and marketed the cup/disc concept.

It prides itself on the fact that the machine pours a perfect beer in record time, and its website shows videos of laymen beer pourers dispensing up to more than 50 beers in one minute.

Check out the video.....



It's not yet ready for market - but should catch the eye of any vendor who likes the idea of pouring beer swiftly and consistently.

The GrinOn website, not content with the revolutionary bottom-up pouring technique, also crows about the advertising potential of the magnetic disc - saying that it could carry a logo or phrase that you can take home.