Abstract :
Bubble coalescence is an important stage of foaming process. A goal of foaming
is to produce numerous, uniform-size bubbles. Therefore, suppression of bubble coalescence
is desirable during foaming process. For stationary bubbles, if their distance is less than
a critical gap, they will coalesce. Actually, in this case, attractive forces attract the outer
surfaces to touch each other and form a growing gas bridge, which nally merges the
bubbles. For bigger distance, the attractive forces cannot make a bridge and coalescence
will not happen. In this study, the dynamics of bubble coalescence are modeled using a
di use-interface LBM. Then, critical gap of bubble coalescence is de ned as the maximum
distance between the stationary bubbles where the coalescence will happen. Sensibility of
critical gap is obtained with respect to critical properties of material, bubble size, viscosity
of gas and liquid, density ratio, surface tension, temperature, and interface thickness. The
results show that interface thickness is the only factor that controls the critical gap. In
other words, in the case of stationary bubbles, by a precise estimation of interface thickness,
the coalescence can be predicted. Critical gap is a useful parameter in foaming where the
maximum number of bubbles is desirable
