The mechanisms of bubble-particle detachment in a turbulence
The mechanisms of bubble-particle detachment in the turbulent field were comprehensively investigated. Based on the analysis of interface evolution and force variation during the detachment process, three mechanisms of a particle detaching from a bubble in turbulence were identified: (1) the centrifugal motion of the particle on bubble surface; (2) the rapid changes in the direction of bubble motion; (3) the oscillations of bubble surface. It was observed that the dynamic contact angle varied in the range of the receding contact angle and advancing contact angle during the detachment process. The capillary force, Laplace pressure force, and centrifugal force were changed due to the interactions of the turbulence and bubble-particle aggregate. The stability of bubble-particle aggregate in turbulence can be significantly enhanced by improving particle hydrophobicity. The distribution of modified Bond numbers in different cases of experiments verified the crucial role of centrifugal force in detaching particles from bubble surfaces in turbulence. Besides, the modified Bond numbers were far less than 1.0 in some experimental cases, which confirmed the detachment process was facilitated by other disruptive forces, such as those caused by the shear effects and bubble oscillations.
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