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Experiments are performed to record data of single drop breakup events in turbulent flow (stirred tank conditions) for improved understanding of the breakup phenomena. Different interpretations can be made of a multiple breakup event, in particular, either the initial breakup can be evaluated, or the entire breakup cascade can be considered. The examining of these two breakup definitions in the present study reveals that the binary breakup event, which is the most frequent used assumption for the number of daughter drops in the literature, is only a rough assessment of the physical truth. For a 1 mm toluene drop up to 47 daughter drops as a consequence of an entire breakup sequence were counted and the arithmetic average value was 11.7 with standard deviation of 7.7. The corresponding average value for the initial breakup was 2.39. By high-speed imaging it is possible to break down the breakup cascade into binary breakups. However, the isolation of these individual breakups is a strong simplification of the breakup process. The breakups in the cascade are triggered by the initial breakup and are not statistically independent. It is more meaningful to evaluate not only the initiation of a drop breakup but the whole sequence of the breakup cascade. The breakup time of the two breakup definitions appears significantly different. For a 1 mm toluene drop the difference in the arithmetic breakup time was 129 ms. The relative number distribution of the breakup time is wider for the breakup cascade than for the initial breakup as it is influence by the wider range and higher number of daughter drops. Resolution limitations of the camera used did not allow determination of the complete daughter size distribution of the final drop population of the breakup cascade with sufficient accuracy. Two different experimental set-ups were used to verify the general trends of the breakup definitions.

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The models for fluid particle breakage and coalescence due to turbulence are generally limited to the inertial subrange of isotropic turbulence and infinite Reynolds numbers. A rigorous procedure for extending the fluid particle breakage and coalescence closures to the entire spectrum of isotropic turbulence and for a wider range of Reynolds numbers can be established based on statistical turbulence theory. The modeling procedure consists of a three‐dimensional (3‐D) literature model energy spectrum for the dissipation, inertial, and energy containing subranges of isotropic turbulence, and an exact literature integral relation for determining the second‐order longitudinal structure function from the 3‐D energy spectrum. A review of the requisite statistical turbulence theory and the use of the model energy spectrum is provided, because the necessary details are not easily accessible in the chemical engineering literature and misconceptions are found in the publications of the previous modeling attempts. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1795–1820, 2016

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