Fabien Beaumont

Kinetics and stability of the mixing flow patterns found in champagne glasses as determined by laser tomography techniques: likely impact on champagne tasting

Laser tomography techniques were used in order to make visible the flow patterns induced by ascending bubbles in flutes poured with champagne. The stability of flow patterns was investigated in flutes showing natural (without any specific surface treatment) as well as artificial effervescence (i.e., engraved at their bottom), all along the first 15min after pouring. Engravement conditions were found to strongly influence the kinetics and the stability with time of the mixing flow phenomena found in champagne glasses.

Visualization of Swirling Flows in Champagne Glasses

For the very first time, classical flow visualization techniques were employed to capture the fluid motion in traditional flutes and coupes poured with champagne(1), (2). These techniques have also been used to underscore the impact of glass shape and glass engravement conditions on the role of flow mixing phenomena on the flavours and aroma exhalation process. To better highlight the fluid dynamics inside a glass, laser tomography combined with fluorescent dyes (sulforhodamine B and fluoresceine, see Figs. 1(a) and (c)) and solid Rilsan tracers (Fig. 1(b)) has been used to give the quasi-instantaneous velocity field and the vorticity convection as well. Once poured with champagne, the glass is lighted in its symmetry plane with a 1 mm planar laser sheet. Because glasses are usually circularly engraved at their bottom, the resulting flow exhibits an annular behaviour clearly evidenced in Figs. 1(a) and (b). Equally surprising is the presence of surface hydrodynamic instabilities at the glass periphery whose details are revealed in Fig. 1(c). If Champagne remains the wine of celebration undoubtedly due to its bubbling behaviour, it should also be for the splendor of its swirling motion

Dynamic-tracking desorption of CO2 in Champagne wine using infrared thermography

Graphical Abstract

Ring Vortex Scenario in Engraved Champagne Glasses

The simple idea this study rests on is that one cannot be concerned by the bubbling and aromatic exhalation events in champagne tasting without being interested in the study of the flow mixing mechanisms inside the glass. Indeed, a key assumption is that a strong link of causality may exist between inherent liquid-phase flow structures due to bubble motion and the flavors exhalation process. This is the reason why, to underscore the impact of glass-shape and glass-engravement conditions on mixing flow phenomena, classical flow visualization techniques were used to capture fluid motion in traditional flutes and coupes poured with champagne. Laser tomography combined with fluorescent dyes and solid tracers have been used to give the quasi-instantaneous velocity field from which streamline patterns are deduced as well as the vorticity convection.

Artificial Bubble Nucleation in Engraved Champagne Glasses

In order to ensure an aesthetic and controlled bubbling behaviour during champagne tasting, specialized glassmakers use to engrave the bottom of glasses by means of impact laser techniques. This industrial process creates artificial nucleation sites which are much more vigorous in terms of bubbling behaviour compared to the natural and random effervescence from tiny particles stuck on the glass wall(1). The resulting bubble column (Fig. 1(a)) is the cause of both the generation of large vortical coherent structures in the liquid flow(2) and the presence of a bubble surface flow acting like a planar isotropic source point (Fig. 1(b)). Due to their short lifetime, most bubbles burst at the free surface during their isotropic migration. A laser sheet in the symmetry plane of the glass highlights the projection in the central migration area of hundreds of champagne droplets induced by bursting events. By use of a long enough exposure time of a digital photo camera, one gets the feeling of visualizing a splendid droplet fog in motion above the champagne surface (Fig. 1(c)).

Evidence for ascending bubble driven flow patterns in champagne glasses, and their impact on gaseous CO2 and ethanol release under standard tasting conditions

A simple glass of champagne or sparkling wine may seem like the acme of frivolity to most of people, but in fact it may rather be considered as a fantastic playground for any fluid physicist or physicochemist. In this tutorial review, some recent investigations on ascending bubble driven flow patterns found in various champagne glasses, and their impact on gaseous carbon dioxide and ethanol release under standard tasting conditions, are reported. Ascending bubble driven flow patterns found in the bulk of various glasses were evidenced, through laser tomography techniques, which illustrate the fine interplay between ascending bubbles and the fluid around. Moreover, spontaneous and self-organised two-dimensional convective cells were also evidenced at the air/champagne interface. In addition, the simultaneous monitoring of gaseous CO2 and ethanol in the headspace of both a flute and coupe filled with champagne was reported, depending on whether or not the glass shows effervescence. Both gaseous CO2 and etha...

Numerical modeling of bubble-induced flow patterns in champagne glasses

Purpose – Very recently, driven by glassmakers and champagne houses, attention has been paid to the way to control effervescence and bubble nucleation. It was demonstrated that ascending bubbles act like many swirling motion generators in champagne glasses. It is the reason why a numerical modeling of flow dynamics induced by the effervescence in a glass of champagne has been carried out for the first time using the finite volume method by Computational Fluid Dynamics (CFD). The paper aims to discuss these issues. Design/methodology/approach – In order to define source terms for flow regime and to reproduce accurately the nucleation process at the origin of effervescence, specific subroutines for the gaseous phase have been added to the main numerical model. These subroutines allow the modeling of bubbles behavior based on semi-empirical formulas relating to bubble diameter and velocity or mass transfer evolutions. Findings – Details and development of the steps of modeling are presented in this paper, sh...

Aerodynamic study of time-trial helmets in cycling racing using CFD analysis

The aerodynamic drag of three different time-trial cycling helmets was analyzed numerically for two different cyclist head positions. Computational Fluid Dynamics (CFD) methods were used to investigate the detailed airflow patterns around the cyclist for a constant velocity of 15 m/s without wind. The CFD simulations have focused on the aerodynamic drag effects in terms of wall shear stress maps and pressure coefficient distributions on the cyclist/helmet system. For a given head position, the helmet shape, by itself, obtained a weak effect on a cyclists aerodynamic performance (<1.5%). However, by varying head position, a cyclist significantly influences aerodynamic performance; the maximum difference between both positions being about 6.4%. CFD results have also shown that both helmet shape and head position significantly influence drag forces, pressure and wall shear stress distributions on the whole cyclists body due to the change in the near-wake behavior and in location of corresponding separation and attachment areas around the cyclist.

Preliminary numerical investigation in open currents-water swimming

The drafting in swimming is a sports practice usually used during the open water race of triathlon. Indeed, it is well known that swimming drafting behind or close to the lead swimmer induces a reduction in drag, once the draft swimmer is located in the low pressure field of the lead swimmers wake. For this purpose, in order to determine the best position for the draft swimmer, a preliminary perfect knowledge of the lead swimmers wake is necessary in presence or not of currents. The present preliminary study focuses this point before developing further analyses on reducing drag and enhancing performance in drafting by considering both lead and draft swimmers. In this work, the computational fluid dynamics (CFD) method was used in order to evaluate the hydrodynamic drag during the swimmers displacement in presence of currents. The standard k-ω turbulence model was chosen to predict the resistance forces with currents-negative (α=0°: aligned position of the swimmers body relative to the main flow direction) and cross-currents (angle of incidence of the swimmers body relative to the main flow direction, respectively 10 and 20°). The analysis of the CFD results have shown that the best position for a draft swimmer was found to be directly behind the lead swimmer (close to the toes) and very close to the side of the lead swimmer when drafters head is between shoulders and hip level of the leader.

Temperature Dependence of Ascending Bubble-Driven Flow Patterns Found in Champagne Glasses as Determined through Numerical Modeling

A numerical modeling of bubble-driven flow patterns in a glass of champagne has been carried out for three champagne temperatures, by using the finite-volume method by CFD (computational fluid dynamics). In order to define source terms for flow regime and to reproduce accurately the bubble nucleation process responsible for champagne effervescence, specific subroutines for the gaseous phase have been added to the main numerical model. These subroutines allow the modeling of bubbles behavior based on semiempirical formulas relating to bubble diameter, mass transfer, velocity, and drag force. Both ascending bubble dynamics and bubble-driven flow patterns dynamics were examined, respectively, 60 s, 180 s, and 300 s after pouring champagne into the glass. Details and development of the various steps of modeling are presented in this paper, showing that the bubble-driven flow patterns velocities of the liquid phase significantly vary with the champagne temperature.