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Oenodynamics

November 29, 2011

Wine has inspired scientists from the very start. As an example, I offer quotations from three scientists whom I've mentioned in this blog.[1]
"Wine is sunlight, held together by water!"
-Galileo Gallilei
"Wine makes daily living easier, less hurried, with fewer tensions and more tolerance."
-Benjamin Franklin
"If penicillin can cure those that are ill, Spanish Sherry can bring the dead back to life."
-Alexander Fleming (Attributed)

Pliny the Elder (Gaius Plinius Secundus), who wrote extensively about minerals in his Natural History (Naturalis Historia),[2] devoted a large potion of that work to wine and viticulture. Pliny was the originator of the famous dictum, "In vino veritas," "In wine (there is) truth."

Figure caption

Beginning of Pliny's discourse on wine and viticulture. (Via Google Books, Ref. 3).

Much of today's technology involves moving fluids from place to place, so fluid dynamics is an important field of physics. As I wrote in a previous article (Superconductivity with a Twist, March 9, 2011), one interesting fluid phenomenon was noted by Galileo. The fluid, of course, was wine, and the phenomenon, which was apparently a well known party trick in Galileo's time, is called the "wine-raiser."

In this party trick, a playing card is placed over a glass of water, and the glass is inverted and placed over over a glass of wine. The card is shifted slightly to allow a flow of liquid between the glasses. This must be done carefully to prevent turbulent mixing. Wine is less dense than water, so it will rise to the top, and the water will fall to the bottom. There a video of this here.

Another fluid phenomenon involving wine is known as "wine legs," or "tears of wine." This is the phenomenon known to all wine connoisseurs in which droplets fall from a ring of clear liquid at the top of a glass of wine of high alcohol content. This happens because alcohol has lower surface tension than water, and wine will flow to regions of lower alcohol concentration. Since alcohol evaporates faster than water, liquid on the sides of the glass will have low alcohol content. This liquid will draw other liquid up to it, and droplets will fall when too much liquid accumulates.

Wine connoisseurs perform another hydrodynamic trick during their wine tasting. Before their first sip, they swirl the wine in their glass to release its bouquet. How this simple process works has been somewhat of a mystery, and where there's both mystery and wine you'll find scientists. A paper by a team of scientists from the École Polytechnique Fédérale de Lausanne (Lausanne, Switzerland), scheduled to be presented at the 64th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (Baltimore, Maryland, November 20-22, 2011) by team member, Martino Reclari, describes results of a study of this fluid dynamics problem.[4-6]

This process is useful not just for wine tasting, but whenever fluids need to be aerated; for example, cell cultures in orbital shaken bioreactors. One thing that was known before this study was that swirling generates a wave that propagates around the inner edge of the glass. The wave churns the liquid as it travels, but how this churning affects the interaction between liquid and air was not known.[5]

In their study, the Swiss scientists generated this wave in an instrumented apparatus that allowed measurement of the liquid velocity. What they found is that the wave propagation around the glass wall also caused the fluid to move back and forth from top to bottom and center to edge. The displacement is more pronounced at the glass wall, and this where most of the liquid-air mixing takes place.[5]

The Swiss team investigated the various process parameters, such as glass diameter and rotation rate, and they discovered a group of dimensionless parameters that govern this fluid flow. The mixing and aeration is optimized with an appropriate choice of parameters. Said Mohamed Farhat, one of the authors of the paper,
"The intuitive and efficient motion of wine swirling has inspired engineers in the field of biopharmaceuticals... [Their] bioreactors offer better mixing and oxygenation over existing stirred tanks, provided that operating parameters are carefully optimized. Moreover, the gentle nature of orbital shaking also ensures a better viability and growth rate of the cells at reduced cost."[5]

The 2011 annual meeting of the AIP Division of Fluid Dynamics was hosted by Johns Hopkins University, the University of Maryland, the University of Delaware and George Washington University. Howard University and the U.S. Naval Academy participated in the organization of the meeting.[5]

References:

  1. Glendal Leon Reeves, Glen's Place.
  2. This Blog, Scratching Diamond, December 6, 2010.
  3. Carolus Mayhoff, Editor, "C. Plini Secundi Naturalis Historiae," vol. 2, books 7-15 (B.G. Teubner, 1875), p. 347. Translation by John Bostock, Pliny the Elder, The Natural History, Book XIV. The Natural History Of The Fruit Trees, Chap. 1 - the Nature Of The Vine. Its Mode Of Fructification, via Project Perseus.
    "Those which have been hitherto mentioned, are, nearly all of them, exotic trees, which it is impossible to rear in any other than their native soil, and which are not to be naturalized in strange countries. It is now for us to speak of the more ordinary kinds, of all of which Italy may be looked upon as more particularly the parent. Those who are well acquainted with the subject, must only bear in mind that for the present we content ourselves with merely stating the different varieties of these trees, and not the mode of cultivating them, although there is no doubt that the characteristics of a tree depend very considerably upon its cultivation. At this fact I cannot sufficiently express my astonishment, that of some trees all memory has utterly perished, and that the very names of some, of which we find various authors making mention, have wholly disappeared."
  4. Martino Reclari, Matthieu Dreyer, Stephanie Tissot, Danail Obreschkow, Florian Wurm and Mohamed Farhat, "'Oenodynamic': hydrodynamic of wine swirling," Anstract for 64th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD), Baltimore, Maryland, November 20-22, 2011.
  5. Charles Blue, "Mechanism of wine swirling explained," American Institute of Physics Press Release, November 21, 2011
  6. Web Site of the 64th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD), Baltimore, Maryland, November 20-22, 2011.