Guiness Bubbles Flowing Downwards

[sdascanada]

I saw a clip on Discovery Canada last night featuring Jearl Walker, a science educator who wrote The Flying Circus of Physics. He attributed the downward flow of the tiny nitrogen bubbles to the attachment of organic molecules as they moved upward through the Guinness (central and not seen because of the colour/thickness of Guinness) and not just due to the turbulent flow characteristics. Any ideas?

[CalMeacham]

Jearl Walker's book The Flying Circus of hysics was and still is a great repository of oddball physics, but he hasn't revised it since it came out 30 years ago, and there's been a lot of work since. His website has been up and down with revamps.


Walker usually draws his stuff from the work of others. A search using Google Scholar turmns up a number of interesting papers on beer bubble flow (there was one several years ago on this topic that I sent to Dave Barry, but I can't find it now). Here are a few:

http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=sm01&database=%2Fdata%2Fepubs%2Fwai s%2Findexes%2Fsm01%2Fsm01&maxhits=200&="T21A-12"

TI: Bubble Growth and Dissolution on Ascent in Water: Applications to Bubbles in Beer and Methane Bubble Dissolution in a Water Column
AU: * Zhang, Y
EM: youxue@umich.edu
AF: The University of Michigan, Dept. of Geological Sciences, Ann Arbor, MI 48109-1063 United States
AU: Xu, Z
EM: zhengjiu@umich.edu

a similar manner to the convective crystal dissolution model of Kerr [1995], but with incorporation of the special features of bubbles. One of the fun applications of the model is to investigate bubble growth in beer. Calculated CO2 bubble growth in beer containing 1.5 bars of CO2 is in agreement with experimental data of Shafer and Zare [1991] More serious applications include bubble growth in lake eruptions and the survival of methane bubbles as they ascend and More serious applications include bubble growth in lake eruptions and the survival of methane bubbles as they ascend and dissolve in a water column. For CO2 bubble growth in lake eruptions, the effect of rapid ascent of the water parcel itself

They seem to think the small bubbles are easily pulled down by the flow, from the abstract. No mention of proteins.


[b]Food and Bioproducts Processing
Print ISSN: 0960-3085 | Electronic ISSN: 1744-3571
Volume: 79 | Issue: C1
Cover date: March 2001
Page(s): 13-20




Characterizing Gas Bubble Dispersions in Beer

--------------------------------------------------------------------------------
Author(s): N. J. Hepworth 1 | J. Varley 2 | A. Hind 3

Certain beers develop a large number of micro bubbles during dispense, which circulate in the beer as it stands in the glass rather than immediately rising to the surface. This phenomenon is often referred to as bubble haze. The challenge is to understand how bubble hazes are affected by process conditions such as changes in the dissolved gas composition, the flow rate of beer and the presence of a sparkler (a flow restrictor) in the tap. In this study, the haze dispersion of a synthetic beer was characterized in terms of three parameters: the time it takes the haze to clear (surge time), the localized rise velocity of the measured haze, and bubble size. A CCD camera based image analysis procedure was developed, to measure bubble size distributions. The surge time was found to increase with increasing beer flow rate, nitrogen content in the supply gas and with the addition of a sparkler. The localized haze rise velocity of the bubble haze fell into two distinct sections. The two sections were distinguished by a doubling in rise velocity. This doubling of the rise velocity marked the point at which the plunging jet of liquid issuing from the beer tap, became sufficiently quiescent for the bubbles to rise unimpeded. Changes in process conditions altered the bubble size distribution, which in turn altered the surge time as expected from consideration of the underlying physical properties and the findings of other researchers. The median bubble diameter and number of bubbles (defined as the number of bubbles visible in the in-focus volume as described by the depth of field, and remains constant) are important factors in determining the haze lifetime and are affected by the process conditions. Understanding this effect quantitatively is central if the system is to be successfully modelled in future.

Author(s): N. J. Hepworth 1 | J. Varley 2 | A. Hind 3

CITATION] Gas entrainment by plunging jets
AK Bin - Chem Eng Sci, 1993


The Physics of Fizz
P Weiss - Science News, 2000 - JSTOR
... Fletcher says that the new bubbles, with diameters smaller ... buoyancy and momentum
to resist the downward currents and so ... sim- ulations only apply to beer in the ...

[Just Ed]

. . . and the column under discussion would seem to be Why do the bubbles in Guinness Stout float down? Dunno if any observed effects in the published studies would be different for nitrogen as opposed to carbon dioxide, as Cecil implies, but I'm also not sure what exactly "the attachment of organic molecules as they moved upward through the Guinness" means, either. At any rate, there seems to be agreement the interior movement of the bubbles is masked by the stout's opacity, and the downward movement observed at the outskirts is a corollary effect (that is, not all the bubbles are flowing downward).

[NunOfTheAbove]

Originally Posted by Quixotic

.Dunno if any observed effects in the published studies would be different for nitrogen as opposed to carbon dioxide, as Cecil implies...

I can think of other double-tap nitrogen beers that have a similar "surging" effect. Belhaven and Boddington's are good examples. This leads me to believe that the nitrogen has to have some effect.