Coagulation in turbulent flow: Theory and experiment

Abstract

The coagulation of colloidal particles in turbulent flows is investigated theoretically and experimentally. A coagulation model is developed for destabilized particles in an isotropic turbulent flow. Simple binary collision mean-free path concepts are employed and for mono-disperse systems coagulation rate relations are derived for particle sizes less than and larger than the Kolmogorov microscale of turbulence. Polydisperse systems are also considered and some general results concerning their behavior are obtained. Coagulation experiments are reported on inside fully developed turbulent pipe flows using an approximately monodisperse UCAR latex dispersion in which the particle sizes are less than the Kolmogorov microscale. The flow rate, destabilizer concentration and volume fraction of the dispersed phase were varied in these experiments. The experimental results for destabilized particles are shown to agree very well with the theoretical predictions. Brownian motion coagulation experiments for partially destabilized systems are compared with the corresponding turbulent motion experiments and the results indicate that the coagulation efficiency does not appear to depend on the particle transport mode.