Deformation and time scales of drop dynamics in turbulent field and the effect of physical properties

Abstract

The deformation scale prior to breakage and time behavior, including the maximum deformation time and the time of the total breakage cascade of two different oil drops in the turbulent field of a stirred tank, was analyzed by high-speed imaging coupled to image processing software. The effects of Reynolds number and the physical properties of drop on the deformation scale and breakage time were quantified and discussed. Different shape descriptors were used to characterize the deformation scale at the impeller vicinity, such as drop projection circularity, projection area increase, and projection perimeter extension, using image processing software. Through flow visualization, new findings concerning the effect of physical properties and Re on the critical deformation scales and breakage time were obtained. The results revealed that drop A, with a lower viscosity, experiences a lower critical deformation scale and a lower breakage time, resulting in a higher number of daughter drop at breakage. Higher viscosity drop (B) exhibited a higher critical deformation scale and higher breakage time, taking longer for breakage. About 90% of the drop deformation scale occurred at the blade’s tip. The breakage time was found to be considerably influenced by physical properties of the drop. A higher impact of impeller Re on the deformation and time behavior of drop A was observed due to the lower surface stability against turbulent stresses. A highly branched morphology of deformed drop A was observed, while drop B exhibited larger elongation.