Measurements of Turbulent Coagulation Process in Turbulent Flow and Comparison with Calculated Results

Abstract

Turbulence causes collisions between neighboring particles by random motions. These collisions then result in coagulation of particles. In this study, we measured the change of size distributions of the suspended aerosol particles in a stirred tank using a scanning electron microscope. We also calculated the process of turbulent coagulation using a population balance equation with three different turbulent collision rate equations. The calculated results based on Saffman and Turner's equation which had neglected the relative velocity between colliding particles due to their inertia underestimated changes of size distributions. The calculated results based on Abrahamson's equation which had neglected the velocity correlation between colliding particles overestimated them. On the other hand, the calculated results based on Yuu's equation which had taken into account both the relative velocity due to their inertia and the velocity correlation between colliding particles were found to be in good agreement with the experimental results. It is concluded that the particle inertia and the correlation between collision particles should not be neglected for the description of particle collisions in turbulence even when the particle sizes are less than one micron.