On the mechanisms of colloidal particle and vapor bubble aggregation in liquid flows

Mechanisms of aggregation of micrometrically scaled colloidal particles and vapor bubbles are discussed. It is shown that when particles move in reference to the liquid, the attractive force induced by the flow may be greater than the capillary interaction. Such a situation is realized when capillary interaction is gravity driven, and particles float. For partial (weak) wetting situations, flow-induced and capillary attractive forces may be comparable. If the wetting is good, it will play a decisive role in the realistically achievable values of the flow velocities. Hydrodynamic interaction between particles may be of primary importance for sedimentation and fast dip-coating-induced aggregation.