Takehiro Nakaoka

Turbulent coagulation model considering effects of London-van der Waals force and wettability

In this study, coagulation rates of various particles observed in agitated water were analysed by a mathematical model of turbulent coagulation. This model is based on the Saffman-Turner model of turbulent collision modified by Higashitani to take into account, van der Waals-London force between a pair of particles under collision. The Higashitani model could not account for the retardation of coagulation rate at high concentrations of suspended particles, which was observed in our precious studies. The new model proposed in this study considered the breakup of coagulating particles due to collision with other particles, and the turbulent shear force. Two parameters were introduced in the model; one was the film-thinning time and the other the breakup frequency. By choosing suitable values of the two parameters, the estimated coagulation curves fitted well with the observed curves. In addition, the film-thinning time increased with increasing wettability of particle and the breakup frequency increased with increasing turbulent intensity.