The fluid dynamics of wine swirling—orbital shaking—could extend to mixing and oxygenation in bioreactors for biopharmaceuticals manufacture. Credit: Farhat, et al.; YouTube.

Even those of us who are not oenophiles—wine aficionados—know that the essential first step to a proper tasting is to swirl the glass to aerate the wine and release its bouquet.

This video by Wine Spectator is a quick step-by-step guide to tasting red wines. The swirling step is important enough to be demonstrated twice, the advanced version and the “training wheels” version.

The fluid dynamics term for this kind of swirling is called “orbital shaking,” and it turns out that how swirling works in a wine glass is not well understood.

“The formation of this wave has probably been known since the introduction of glass or any other kind of cylindrical bowl, but what has been lacking is a description of the physics related to the mixing and oxygenation,” according to Mohamed Farhat in a press release.

I was wondering about that, too.

Farhat is a senior scientist the Ecole Polytechnique Federale de Lausanne in Switzerland, and his work on fluid flow and the wave dynamics in a wine glass will be presented at the 64th Annual Meeting of the Division of Fluid Dynamics of the American Physical Society in Baltimore, Md., which is underway now.

His team used state-of-the-art instrumentation to track the motion of waves in cylinders. The study showed that the waves and liquid interact to set up a pumping mechanism that improves the mixing. Several types of wave patterns form, as the video above shows. Farhat says, “for a given glass shape, the mixing and oxygenation may be optimized with an appropriate choice of shaking diameter and rotation speed.”

The study has implications that extend far beyond the pleasure of a good glass of wine. Farhat says “The intuitive and efficient motion of wine swirling has inspired engineers in the field of biopharmaceuticals,” where cell cultures in large cylindrical bioreactors are often subjected to orbital shaking. Farhat says his “oenodynamic” work shows that “such 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.”

The talk, “‘Oenodynamic: hydrodynamics of wine swirling,” is being presented by Farhat’s student and PhD candidate, Martino Reclari, on Monday, Nov. 21.

In connection with the meeting, the APS/DFD has assembled a very nice gallery of fluid dynamics images and videos that are worth the time it will take you to drink a glass of wine, properly swirled, of course.