On the constitutive equations for fluid particle breakage

The mechanisms and modeling concepts proposed in the literature for the fluid particle (i.e., bubble and drops) breakage phenomena in laminar and turbulent dispersions are examined. Four categories are considered for the breakage mechanisms: (i) turbulent motions and inertial stresses, (ii) viscous shear stresses, (iii) shearing-off processes, and (iv) interfacial instability. In the first category, six breakage criteria have been proposed. The constitutive equations for the breakage frequency and daughter size probability density functions for these mechanisms are examined. A brief survey of experimental analyses performed to understand the behavior of these functions is provided. It is concluded that extensive, well-planned, model-based experiments are required to elucidate the underlying mechanisms for fluid particle breakage. In particular, single particle experiments in known flow regimes are needed to determine the functionality of the breakage frequency, number of daughters, and the daughter size distribution functions and for parameter fitting. Size distribution measurements in the same flow regimes are useful for model validation studies.