Dynamics of bubble coalescence in non-Newtonian fluids: A chaotic approach

This work reports a study of in-line bubble coalescence in non-Newtonian fluids. An original method is elaborated by relating the rise of a chain of bubbles to consecutive shear deformations. A series of measurements on a rheometer and the visualisation method based on birefringence prove for the first time that the bubble coalescence is mainly governed by the dynamical competition between the creation and relaxation of shear stresses. The time delay embedding method of reconstructing the phase-space diagram is applied to time series data recorded at different heights in the bubble column. The calculation of several parameters: the largest Lyapunov exponent, the correlation dimension, the power spectrum, and the phase portraits, reveals that the coalescence between bubbles obeys a chaotic and deterministic mechanism.