Coalescence of a bubble at a fluid–fluid interface: Comparison of theory and experiment

Coalescence times for air bubbles rising through hexadecane to an air–hexadecane interface are measured and compared with an analysis based upon our previous extension of continuum mechanics to the nanoscale [J.C. Slattery, E.-S. Oh, K. Fu, Chem. Eng. Sci. 59 (2004) 4621–4635] with the assumption of retarded dispersion forces. The relation between the retarded and non-retarded Hamaker constants proposed by Görner and Pich [J. Aerosol Sci. 20 (7) (1989) 735–747] is tested for the first time.

Graphical abstractAs a bubble approaches an interface during the last stage of coalescence, a thin liquid film is formed and deformed as the result of retarded dispersion forces. Its thickness h∗h∗ is a function of time t∗t∗ and radial position r∗r∗. The film ruptures and coalescence occurs, when h∗=0h∗=0.Figure optionsDownload full-size imageDownload as PowerPoint slide