  We carry out direct numerical simulation combined with adhesive discrete
element calculations to investigate collision-induced breakage of agglomerates
in homogeneous isotropic turbulence. Based on extensive simulation runs, an
adhesion parameter Adn is constructed to quantify the possibility of occurrence
of sticking, rebound, and breakage events. The collision-induced breakage rate
is then formulated based on the Smoluchowski equation and a breakage fraction.
The breakage fraction, defined as the fraction of collisions that result in
breakage, is then analytically estimated by a convolution of the probability
distribution of collision velocity and a universal transfer function. It is
shown that the breakage rate decreases exponentially as the adhesion parameter
Adn increases for doublets and scales as linear functions of the agglomerate
size, with the slope controlled by Adn. These results allow one to estimate the
breakage rate for early-stage agglomerates of arbitrary size. Moreover, the
role of the flow structure on the collision-induced breakage is also examined.
Violent collisions and breakages are more likely caused by particles ejected
rapidly from strong vortices and happen in straining sheets. Our results extend
the findings of shear-induced fragmentation, forming a more complete picture of
breakage of agglomerates in turbulent flows.
