Capillary-Driven Flower-Shaped Structures around Bubbles Collapsing in a Bubble Raft at the Surface of a Liquid of Low Viscosity Ge ´rard Liger-Belair* and Philippe Jeandet Laboratoire d’Œnologie, UFR Sciences Exactes, UPRES EA 2069, BP 1039, 51687 Reims, Cedex 2, France Received February 19, 2003. In Final Form: May 16, 2003 By using a classical photo camera and a high-speed video camera, snapshots and time sequences of the dynamics of champagne bubbles collapsing close to each other in a bubble raft composed of quite monodisperse millimetric bubbles were made, thus completing two recent works (Liger-Belair et al. in C. R. Acad. Sci. Paris Se ´ rie 4 2001, 2, 775-780 and Liger-Belair in Ann. Phys. Fr. 2002, 27 (4), 1-106). Bubble caps of bubbles adjacent to a collapsing one were found to be strikingly stretched toward the lowest part of the cavity left by the central bursting bubble. Orders of magnitude of shear stresses developed in the adjacent deformed bubble caps were indirectly estimated. Our results strongly suggest, in the thin film of adjacent bubble caps, stresses higher than those observed around a single millimetric collapsing bubble. High-speed time sequences also proved that bubble caps in touch with collapsing bubbles were never found to rupture, thus causing in turn a chain reaction. As in the case of single collapsing cavities, it was also observed that a tiny daughter bubble, approximately 10 times smaller than the initial central bursting bubble, was entrapped during the collapsing process of the central cavity. 1. Introduction As was summarized by Detlef Lohse in a very recent review article, 1 bubbles are very common in our everyday life. They occupy an important role in many natural as well as industrial processes (in physics, chemical and mechanical engineering, oceanography, geophysics, tech- nology, and even medicine). Nevertheless, their behavior is often surprising and, in many cases, still not fully understood. In the present research article, we go back on an unexpected observation recently conducted with bubbles collapsing in the bubble raft at the free surface of a glass poured with champagne. 2,3 Since the first pioneering photographic investigation published in Nature, precisely 50 years ago, 4 numerous experimental, numerical, and theoretical studies have been conducted with single bubbles collapsing at a free surface (see for examples refs 4-22). This phenomenon becomes more and more understood and is now thoroughly modeled. 18-22 In very short, the open cavity left after the disintegration of a bubble cap will collapse inward, leading to the upward projection of the often so-called Worthington jet. 23 As a result of the well-known Rayleigh-Plateau instability, this liquid jet will break up into a few droplets called jet drops. 24,25 It has also been experimentally and numerically observed that a tiny air bubble of about 1 / 10 of the radius of the parent bursting bubble may be entrapped during the collapsing process. Bubble entrap- ment, nevertheless, depends on the parent bubble size and on some physicochemical properties of the liquid medium. 20,21 But despite the large body of research concerned with collapsing bubble dynamics, by using classical high-speed macrophotography techniques, the close-up observation of bubbles collapsing at the free surface of a glass poured with champagne, nevertheless, recently revealed an unexplored and visually appealing phenomenon. Actually, while trying to get the famous Worthington jets arising when champagne bubbles collapse at the liquid surface, snapshots of bubbles collapsing close to each other were taken by accident. Clusters of bubbles strongly deformed toward a bubble-free central area were observed, leading to unexpected and visually appealing flower-shaped structures. 2,3 As surprising as it may seem, no results concerning the collateral effects on adjoining bubbles of bubbles collapsing in a bubble monolayer had been * Corresponding author. Telephone: (33) 3 26 91 86 14. Fax: (33) 3 26 91 33 40. E-mail: gerard.liger-belair@univ-reims.fr. (1) Lohse, D. Phys. Today 2003, 56 (2), 36-39. (2) Liger-Belair, G.; Robillard, B.; Vignes-Adler, M.; Jeandet, P. C. R. Acad. Sci., Ser. IV 2001, 2, 775-780. (3) Liger-Belair, G. Ann. Phys. (Paris) 2002, 27 (4), 1-106. (4) Woodcock, A.; Kientzler, C.; Arons, A.; Blanchard, D. Nature 1953, 172, 1144-1145. (5) Kientzler, C.; Arons, A.; Blanchard, D.; Woodcock, A. Tellus 1954, 6,1-7. (6) Blanchard, D. Prog. Oceanogr. 1963, 1, 77-202. (7) MacIntyre, F. J. Geophys. Res. 1972, 77, 5211-5228. (8) Wu, J. Science 1981, 212, 324-326. (9) Blanchard, D.; Syzdek, L. Appl. Environ. Microbiol. 1982, 43, 1001-1005. (10) Resch, F.; Darrozes, J.; Afeti, G. J. Geophys. Res. 1986, 91, 1019- 1029. (11) Blanchard, D. J. Geophys. Res. 1989, 94, 10999-11002. (12) Blanchard, D. Tellus, Ser. B 1990, 42, 200-205. (13) Dekker, H.; de Leeuw, G. J. Geophys. Res. 1993, 98, 10223- 10232. (14) Spiel, D. Tellus, Ser. 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London Math. Soc. 1878, 10,4-13. 5771 Langmuir 2003, 19, 5771-5779 10.1021/la034290j CCC: $25.00 © 2003 American Chemical Society Published on Web 06/12/2003