THE DYNAMICS OF WINE

Figure 1.                                                                Figure 2.

Figure 3.                                                               Figure 4.



    In a wine glass, evaporation of alcohol creates Marangoni stresses that cause the wine to climb to the top of the thin film, where it accumulates in a band that grows until becoming gravitationally unstable and releasing the `tears of wine'. The tears of wine are evident in Figure 1, a plan view of a wine glass. Also evident in Figure 1 is a fine radial spoke pattern in the meniscus, which accompanies the tears of wine in strong alcoholic beverages.

    We have demonstrated that this spoke pattern results from ridge-like elevations of the free surface supported by evaporatively-driven Marangoni convection within the thin film. The ridges are evident in Figure 2, which is an oblique perspective looking along the meniscus region adjoining the reservoir (left) and the thin film (right). Tears roll from right to left in Figure 2. Vortices associated with small-scale convective motions are aligned in the streamwise direction by the surface tension gradient responsible for the sustenance of the tears. The convective motions are revealed by adding Kalliroscope to the fluid, and are evident in Figure 3, a plan view of a wine glass in which the reservoir is at the bottom, the thin film in the middle and the incipient tear line at the top. Finally, when the angle of inclination of the glass is very small, the meniscus region is marked by a dendritic free-surface structure (Figure 4).

    The results of our combined experimental, theoretical and numerical models of evaporatively-driven convective instabilities in climbing films is presented in Hosoi & Bush (2001).

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