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Coalescence of electrolytically-generated, 50-to 600-pm-diameter gas bubbles was observed using an optical technique that employs a linear photodiode array to detect inteface movement with a resolution of 10-6s. when two bubbles coalesce, the suface energy that is released causes interface velocities of 2 to 4 m/s; these are followed by large-amplitude damped oblateprolate oscillations. Within the viscosity range studied, the oscillation period is insensitive to the viscosity and damping is insensitive to surface tension, in agreement with a scaling analysis based on a damped harmonic oscillator. Surface waves are superimposed on the motion. Finite-element solutions of the freesugace, nonlinear Navier-Stokes equations are consistent with the experiments.

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